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Feature-based characterisation of surface topography and its application
Abstract
This keynote paper gives an overview of emerging technologies of feature-based characterisation, for surface topographies having features. It is complementary to conventional surface characterisation using texture field parameters. An original concept, the feature spectrum is proposed to organise surfaces, in order to help select the appropriate characterisation for different types of surface topographies and to achieve a more direct relationship between characterisation, manufacturing process and surface function. The keynote paper focuses on fundamentals and the state of the art for feature-based characterisation technologies. Applications of feature-based characterisation are illustrated and discussed. Guidelines for future industrial applications are laid out, and considerations for future challenges are addressed.
Surfaces, Micro structure, Feature-based Characterisation.
... FBC is a developing area of surface metrology that focusses around the characterisations of features found in topographical data that has been proven effective at identifying expected features on PBF surfaces [242,243]. This approach varies from conventional methods of surface characterisation, such as surface texture parameters like roughness and waviness, by targeting individual features on the surface. ...
... Spatter features are formed by fully molten gobs of material ejected from the processing area and fallen back onto the surface. FBC methods to identify leftover particles and spatter features have been successfully implemented in previous work, however only from labbased surface topography measurement, i.e. not in-situ [243][244][245]. ...
Metal powder bed fusion systems have been rapidly gaining interest from high-value manufacturing sectors, such as aerospace and biomedical, due to the unique benefits the technology can offer in terms of part design flexibility and bespoke manufacturing. In-process monitoring techniques for metal powder bed fusion have become increasingly popular as the technology continues to mature. However, adequate methods of handling data collected from the manufacturing process have yet to be explored in depth. Due to the large quantities of potential data and the temporal constraints when monitoring the PBF process, automated data interpretation is essential to allow for real time defect detection to be achieved. In this thesis, a novel measurement method for PBF systems is proposed that uses multi-view fringe projection to acquire high-resolution surface topography information of the powder bed. Measurements were made using a mock-up of a commercial powder bed fusion system to assess the system’s accuracy and precision in comparison to conventional single-view fringe projection techniques for the same application. Featured based characterisation methods were applied to the measured topography to extract salient information about spatter and particles with the data being compared against a higher resolution reference measurement (focus variation). Results show that the multi-view system is more accurate, but less precise, than single view fringe projection on a point-by-point basis. The multi-view system also achieves a high degree of surface coverage by using alternate views to access areas not measured by a single camera. Measurements from the multi-view fringe projection system achieved similar reconstruction fidelity to the reference focus variation, in particular at the scales required for the largest targeted features (200 µm size and up). Topography partitioning and feature identification results achieved by feature based characterisation were comparable between fringe projection and focus variation.
... There were many digital filters provided for the extraction of form from the data such as spline [22,23], wavelet [24,25], morphological [26,27], fast Fourier transform (FFTF) [28,29], and many others [30]. Very popular in recent studies is multi-scale characterisation [31][32][33] or analysis based on feature consideration [34,35]. These techniques separate the received raw measured data in various frequencies using different methods, and filters in some cases [36]. ...
... However, this property was received when the ACFs were thresholded. These techniques, and especially their validity, have been widely introduced and considered for surface roughness analysis in many previous studies [35,64,89,90]. ...
Studies of surface topography including processes of measurement and data analysis have an influence on the description of machined parts with their tribological performance. Usually, surface roughness is analysed when a scale-limited (S-L) surface, excluding short (S-) and length (L-) components from the raw measured data, is defined. Errors in the precise definition of the S-L surface can cause the false estimation of detail properties, especially its tribological performance. Errors can arise when the surface contains some burnished details such as oil pockets, dimples, scratches, or, generally, deep or wide features. The validation of proposed methods for S-L surface definition can also affect the accuracy of the ISO 25178 surface topography parameter calculation. It was found that the application of commonly used procedures, available in commercial software (e.g., least-square fitted cylinder element or polynomial planes, regular or robust Gaussian regression, spline, median or fast Fourier transform filters) can be suitable for precise S-L surface definition. However, some additional analyses, based on power spectral densities, autocorrelation function, texture direction graphs, or spectral characterisation, are strongly required. The effect of the definition of the S-L surface on the values of the ISO 25178 parameters was also comprehensively studied. Some proposals of guidance on how to define an appropriate S-L surface with, respectively, an objective evaluation of surface roughness parameters, were also presented.
... It is based on a novel approach to localize lead structures as individual elements in high-resolution topography measurement data. The motivation for this type of evaluation is feature-based surface characterization, described, among others, in [35,36]. The structurebased lead analysis requires optical measurement data which provide high-resolution topographies and form the basis for the further application of segmentation algorithms. ...
The leak tightness of the sealing system rotary shaft seal is based on the formation of an active back-pumping effect of the sealing ring. Here, the sealing ring pumps the fluid in the sealing gap back into the housing. However, this active sealing mechanism is disturbed by so-called “lead structures”. Lead structures include all types of directional structures on the sealing counterface which create rotation-dependent axial fluid pumping. Lead-affected sealing counterfaces can thus cause leakage or insufficient lubrication of the sealing contact. To ensure leak tightness, lead must be avoided or tolerated. This article investigates how different structural characteristics of lead affect the amount of fluid pumped by the shaft surface. For this purpose, 26 shafts are subjected to surface analyzing methods and an experimental pumping rate test. The interaction of various geometric features of the lead structures and their combined effect on the pumping capacity is modeled based on the measured data. Appropriated correlation models are discussed and relationships between shaft lead and its pumping effect are shown. The aim is to estimate shaft pumping rates based on surface measurements in future. The results contribute to the derivation of measurable tolerance values for lead and to the prevention of leakage.
... Contrary to surface data filtering techniques, algorithms based on the deviation or slope can be successfully used [36]. Many encouraging results for data suppression were presented by Jiang et al. [58] based on the thresholding technique which refers to a family of segmentation methods. This approach was found especially suitable when the reduction in time of the data processing is important. ...
In this paper, the methods of compensation of differences in the results of entire bending-fatigued fracture surface topographies were presented. The roughness evaluation was performed with a focus variation microscope and confocal surface topography measurement techniques. The differences in the ISO 25178 roughness parameters were investigated and procedures for their compensation were studied. It was found that various types of optical measurements can cause differences in the errors occurring in the measurement process, such as outliers, and noise. The reduction of differences in the various optical roughness measurements can be attained when measurement errors are compensated. For this study, the applications of general procedures available in commercial software can be suitable for improvements of the roughness measurement results, such as raw data thresholding technique, digital filtering (S-filter), power spectral density, and autocorrelation function analyses. The validation of measurement techniques was proposed for areal and profile studies, including analysis of differences in the calculation areal ISO 25178 roughness parameters.
... Numerical modeling of a rough surface is required to solve three problems. First, the prediction of standard texture parameters in the manufacture of products and the identification of the reasons for non-compliance with the specified values [1,2]. Secondly, modeling of physical processes during the operation of a product, for example, for tribology of surface mating [3,4] or assembly of products [5][6][7]. ...
Numerical modeling of a rough surface is required to predict the quality in the manufacture and physical simulate of the product. Another important application is the testing of filtering methods in metrology. The transition from standard texture parameters to an analytical description of the surface geometry makes it possible to solve these problems at a higher level. In digital manufacturing, this step is extremely important. Additive manufacturing products have manufacturing features, that distinguish them from other processing methods. The real surface is a complex geometric object and contains deterministic and stochastic components. There is a pronounced deterministic component from the trajectory and scanning speed of the laser and a stochastic component from the physics of powder melting. The main scientific idea of this article is to model texture as a superposition of two deterministic and two Gaussian components with different parameters under given constraints. Surfaces were modeled using a combination of four component errors. For simulated surfaces, the problem of identifying relationships between model parameters and standard surface texture parameters was solved. The numerical simulation performed showed a good agreement with the real data of surface texture measurements.
... Frequently observed features in powder-based AM are particle agglomerations of different size. In recent years, extensive work has been done on developing methods for segmentation and feature detection and their application to AM surfaces [8][9][10][11][12][13][14][15]. In this work, we focus on the evaluation of surface properties related to powder particle agglomerations, such as size and quantity, as well as the area portion of the surface covered by attached particles and their relation to the particle size distribution of the powder used in the process. ...
Additive manufacturing (AM) technologies show potential for the development of functionally integrated lightweight designs, biomimetic structures and material savings. Typically, as-built surfaces show powder particle agglomerations and re-entrant features, leading to rough surfaces, which are associated with poor fatigue performance. To benefit from the full range of advantages with special focus on aerospace applications, critical features for crack initiation when subjected to fatigue loading need to be identified and mitigated. A first step toward achieving this goal is the surface texture characterisation based on the quantification of surface features. In this paper, selected areal height, functional and feature parameters from ISO 25178-2:2022 are generated and process-specific features are examined for as-built AlSi7Mg0.6 from laser powder bed fusion (PBF-LB). A connection with the particle size distribution of the used powder is demonstrated. It is shown that surface feature analysis opens up opportunities to use physically meaningful surface characteristics in future quality assurance and part qualification processes.
... Frequently observed features in powder-based AM are particle agglomerations of different size. In recent years, extensive work has been done on developing methods for segmentation and feature detection and their application to AM surfaces [8][9][10][11][12][13][14][15]. In this work, we focus on the evaluation of surface properties related to powder particle agglomerations, such as size and quantity, as well as the area portion of the surface covered by attached particles and their relation to the particle size distribution of the powder used in the process. ...
Additive manufacturing (AM) technologies show potential for the development of functionally integrated lightweight designs, biomimetic structures and material savings. Typically, as-built surfaces show powder particle agglomerations and re-entrant features, leading to rough surfaces, which are associated with poor fatigue performance. To benefit from the full range of advantages with special focus on aerospace applications, critical features for crack initiation when subjected to fatigue loading need to be identified and mitigated. A first step toward achieving this goal is the surface texture characterisation based on the quantification of surface features. In this paper, selected areal height, functional and feature parameters from ISO 25178-2:2022 are generated and process-specific features are examined for as-built AlSi7Mg0.6 from laser powder bed fusion (PBF-LB). A connection with the particle size distribution of the used powder is demonstrated. It is shown that surface feature analysis opens up opportunities to use physically meaningful surface characteristics in future quality assurance and part qualification processes.
... The reduction in errors in the feature characterization is another encouraging task to be resolved [31]. In general, each of the actions provided on the surface topography data, including those with the feature-based characterization, is provided for a more direct relationship between characterization, manufacturing process, and surface function [32]. The effect of feature size, density, and distribution was found crucial in the validation of methods for both an areal form removal and high-frequency measurement noise reduction [33]. ...
Characterization of surface topography, roughly divided into measurement and data analysis, can be valuable in the process of validation of the tribological performance of machined parts. Surface topography, especially the roughness, can respond straightly to the machining process and, in some cases, is defined as a fingerprint of the manufacturing. When considering the high precision of surface topography studies, the definition of both S-surface and L-surface can drive many errors that influence the analysis of the accuracy of the manufacturing process. Even if precise measuring equipment (device and method) is provided but received data are processed erroneously, the precision is still lost. From that matter, the precise definition of the S-L surface can be valuable in the roughness evaluation allowing a reduction in the rejection of properly made parts. In this paper, it was proposed how to select an appropriate procedure for the removal of the Land S-components from the raw measured data. Various types of surface topographies were considered, e.g., plateau-honed (some with burnished oil pockets), turned, milled, ground, laser-textured, ceramic, composite, and, generally, isotropic. They were measured with different (stylus and optical) methods, respectively, and parameters from the ISO 25178 standard were also taken into consideration. It was found that commonly used and available commercial software methods can be valuable and especially helpful in the precise definition of the S-L surface; respectively, its usage requires an appropriate response (knowledge) from the users.
... The formation of the quality parameters of the treated surface is due to the friction of the smooth part of the tool and the opposite movement of the inclined groove on the contact surface of the workpiece. Based on the features of topography defined in [44], the results of the analysis of the topographies of the treated surfaces (see Figure 9) show that the location of the peaks is more uniform for the surface after the MPT with the tool with the oppositely directed grooves on the working surface than it is after the treatment using another tool. The surface waviness in the transverse direction is more pronounced than it is in the longitudinal one ( Figure 10). ...
A surface nanocrystalline steel layer in the low alloy steel 41Cr4 was fabricated by using mechanical-pulse treatment (MPT) with different deformation modes. The structure parameters, the physical and mechanical properties, the wear resistance, and the surface topography parameters of the treated steel depending on the deformation mode were investigated. A tool with a smooth working surface was used for inducing unidirectional deformation in the top surface layer (shear), and a tool with the oppositely directed grooves was used for generating multidirectional deformation. The surface layer with a nanocrystalline structure formed by MPT using both of the tools was characterised by enhanced mechanical properties and wear resistance compared with those of the untreated or heat-treated steels. Inducing multidirectional deformation during the MPT resulted in a decrease in the grain size and an increase in the depth and microhardness of the surface layer due to it facilitating the generation of dislocations compared to those formed under unidirectional deformation. The results also demonstrated that favourable surface topography parameters providing the highest wear resistance of the steel were obtained at MPT using multidirectional deformation.
... Dabei werden Täler und Hügel voneinander getrennt und Elemente, die den Prunenschwellwert (i.d.R. angegeben in %Sz) unterschreiten, mit dem nächstgelegenen größeren Element kombiniert, wie veranschaulicht in Bild 3. In der ISO 25178[3] ist für einige Elementparameter der Standard-Schwellwert mit 5% angegeben. Für detaillierte Informationen wird auf[3][4][5][6] verwiesen. Kombination kleiner Täler durch WolfbeschneidungFigure 3: Combination of small dales by Wolf pruningEs werden in dieser Arbeit Charakteristika von Senken betrachtet, da in Folgearbeiten vor allem der Zusammenhang mit der Dauerfestigkeit thematisiert wird. ...
Additive manufacturing (AM) technologies show potential for the development of functionally integrated lightweight designs, biomimetic structures and material savings. Typically, as-built surfaces are characterized by powder particle agglomerations and re-entrant features, leading to a high initial surface roughness, which is associated with poor fatigue performance. In order to make use of the full range of advantages with special focus on aerospace applications, critical features for crack initiation when subjected to fatigue loading need to be identified and mitigated. A first step toward achieving this goal is the surface texture characterization based on the quantification of surface features by means of surface feature parameters. Selected areal feature parameters are evaluated and compared for three different as-built surface conditions of aluminium alloy samples from laser powder bed fusion (LPBF).
... In contrast, this current paper assumes that Uncertainties are Topographically and Material Dependent, called UTMD, i.e., uncertainties depend on the material properties and complexities of topographies [7]. For this reason, some surfaces are manufactured to be closer to industrial topographies and, therefore, more appropriate for estimating practical UTMD. ...
A top-down method is presented and studied for quantifying topographic map height (z) fluctuations directly from measurements on surfaces of interest. Contrary to bottom-up methods used in dimensional metrology, this method does not require knowledge of transfer functions and fluctuations of an instrument. Fluctuations are considered here to be indicative of some kinds of uncertainties. Multiple (n), successive topographic measurements (z = z(x,y)) are made at one location without moving the measurand relative to the measurement instrument. The measured heights (z) at each position (x,y) are analyzed statistically. Fluctuation maps are generated from the calculated variances. Three surfaces were measured with two interferometric measuring microscopes (Bruker ContourGT™ and Zygo NewView™ 7300). These surfaces included an anisotropic, turned surface; an isotropic, sandblasted surface; and an abraded, heterogeneous, multilayer surface having different, complex, multiscale morphologies. In demonstrating the method, it was found that few non-measured points persisted for all 100 measurements at any location. The distributions of uncertainties are similar to those of certain features on topographic maps at the same locations, suggesting that topographic features can augment measurement fluctuations. This was especially observed on the abraded ophthalmic lens; a scratch divides the topographic map into two zones with different uncertainty values. The distributions of fluctuations can be non-Gaussian. Additionally, they can vary between regions within some measurements.
... Furthermore, the statistical properties of feature aggregations, such as mean or standard deviation, may be more intuitive or related to functionality and could be assessed with a feature-based characterisation. Moreover, isolating relevant topographic formations, regularly defined as features, is a developing field of study in surface topography measurement [46,47]. Examples of feature characterisation are methods with excluding valleys approaches [48,49]. ...
Errors that occur when surface topography is measured and analysed can be classified depending on the type of surface studied. Many types of surface topographies are considered when frequency-based errors are studied. However, turned surface topography is not comprehensively studied when data processing errors caused by false estimation (definition and suppression) of selected surface features (form or noise) are analysed. In the present work, the effects of the application of various methods (regular Gaussian regression, robust Gaussian regression, and spline and fast Fourier Transform filters) for the suppression of high-frequency measurement noise from the raw measured data of turned surface topography are presented and compared. The influence and usage of commonly used available commercial software, e.g., autocorrelation function, power spectral density, and texture direction, which function on the values of areal surface topography parameters from selected (ISO 25178) standards, are also introduced. Analysed surfaces were measured with a stylus or via non-contact (optical–white light interferometry) methods. It was found that the characterisation of surface topography, based on the analysis of selected features, can be crucial in reducing measurement and data analysis errors when various filters are applied. Moreover, the application of common functions can be advantageous when feature-based studies are proposed for both profile and areal data processing.
... A Sisma MYSINT100 LPBF machine was used to fabricate parts, whose surface topography was acquired using the CT device described in Section 2.2 to exploit the CT capability of measuring also re-entrant surface features [24]. The obtained surfaces (see the example in Fig. 6a) were analyzed with two different methods: feature-based analysis to segment and measure the features on the surface [25] (see the example in Fig. 6b), and characterization of surface profiles including re-entrant features (see the example in Fig. 6c). The featurebased analysis was performed through a specifically developed procedure implemented combining the use of VGStudio MAX 3.2 and ImageJ to evaluate the equivalent spherical diameter of surface features (dsf). ...
Metal powder has a significant influence on the quality and performance of laser powder bed fusion (LPBF) processes and products. A key requirement for metal powder is to have shape and size distribution designed to have adequate flowability, packing behavior and laser absorption, as well as to fabricate parts with acceptable density, surface finish and mechanical properties. Accurate three-dimensional (3D) characterizations of powder particles are fundamental to enable relevant research, for example on powder reuse and material waste reduction in LPBF. This work studies advanced measurement approaches, based on X-ray computed tomography (CT), for the 3D geometrical characterization of powder particles. The work includes comparisons with conventional powder characterization methods, considering different materials and powder morphologies. Results show the potential of the CT-based approaches to provide accurate and complete 3D powder geometrical measurements, and to exploit the obtained results for the enhancement of surface topography analyses and LPBF development.
... Evaluating the surface coatings' properties is correlated to the characterization of selected features. Very popular in the analysis of ST are, as commonly called, featurebased algorithms [34] or feature-based procedures [35], used for segmentation [36] of the measured surface topography area. Additionally, methods based on multi-scale analysis are also popular in surface metrology [37]. ...
Coatings, taking comprehensive studies into account, cannot be considered without their functional performance [...]
... The surface of the Tintoretto painting, before or after the laser-chemical cleaning, is considered (locally) a stochastic-dominated surface and it is analyzed in term of average surface descriptors in small ROIs (order of centimeter). At the larger scale, an ancient painting, which is a hand-made artistic object with its complex and unique conservation history, can be likely treated as a stochastic-deterministic surface, on which advanced feature-based analysis [38] of topography could be tested, e.g., to study brushstroke pattern as an artist fingerprint [3]. To this regard, we point out that the possible pattern left by the manual cleaning treatment (i.e., by hand-held laser probe or solvent swabbing) across the painting was out of the aim of the present study and that the experimental test areas were prepared and supposed to be representative of the average painting surface. ...
In the field of engineering, surface metrology is a valuable tool codified by international standards that enables the quantitative study of small-scale surface features. However, it is not recognized as a resource in the field of cultural heritage. Motivated by this fact, in this work, we demonstrate the use and the usefulness of surface metrology based on scanning conoscopic holography for monitoring treatments on the Venetian masterpiece by Tintoretto St. Martial in Glory with the Saints Peter and Paul. We carried out in situ and in-process monitoring of the painting microtexture during an experimental, innovative laser–chemical treatment, and we performed a statistical analysis based on ISO areal field parameters. A wide and in-band roughness analysis through the complementary use of amplitude, spatial, and hybrid parameters confirmed the noninvasive nature of the whole treatment on the painting surface topography, giving us the chance to review and critically discuss the use of these parameters in a real case in heritage science.
... While this organizational approach is very reasonable when comparing image processing options, it does not provide insights into correct selection of a processing method for a given imperfection-surface combination. A recent CIRP review paper from Jiang et al. [104], that addresses feature segmentation and characterization from areal height maps is also a useful resource for this task. Figure 24 is an attempt at a high-level overview of the available processing strategies along with example processing tools to achieve the same. ...
This paper takes the broad topic of geometrical surface imperfections on manufactured surfaces and provides an overview of how they affect component functionality and how they may be detected and classified as defects or not. The presented overview considers both human visual inspection and machine vision-based approaches along with their evolving roles. Of note is that the paper takes a highly granular field consisting of customized solutions for customized applications and frames the discussion around fundamental considerations for each of the tasks; search/acquisition, sensing/detection, processing, classification and decision. Future trends and areas still requiring attention are highlighted.
... A typical example is a thresholding on heights which, due to their simplicity, become a common method to obtain a segmentation of the surface topography. However, simple thresholding is not a stable method when surfaces have a stochastic content and can produce many insignificant features that can cause problems for many characterisation parameters, such as the number of defects and the density of features [55]. Alternatively, morphological segmentation into hills or dales is the only partitioning operation currently endorsed by the ISO specification standards on surface texture metrology [56]. ...
There are many factors influencing the accuracy of surface topography measurement results: one of them is the vibrations caused by the high-frequency noise occurrence. It is extremely difficult to extract results defined as noise from the real measured data, especially the application of various methods requiring skilled users and, additionally, the improper use of software may cause errors in the data processing. Accordingly, various thresholding methods for the minimization of errors in the raw surface topography data processing were proposed and compared with commonly used (available in the commercial software) techniques. Applied procedures were used for the minimization of errors in the surface topography parameters (from ISO 25178 standard) calculation after the removal and reduction, respectively, of the high-frequency noise (S-filter). Methods were applied for analysis of the laser-textured surfaces with a comparison of many regular methods, proposed previously in the commercial measuring equipment. It was found that the application of commonly used algorithms can be suitable for the processing of the measured data when selected procedures are provided. Moreover, errors in both the measurement process and the data processing can be reduced when thresholding methods support regular algorithms and procedures. From applied, commonly used methods (regular Gaussian regression filter, robust Gaussian regression filter, spline filter and fast Fourier transform filter), the most encouraging results were obtained for high-frequency noise reduction in laser-textured details when the fast Fourier transform filter was supported by a thresholding approach.
... On the other hand, 2D parameters like Ra or Rz are often used in industry. Other parameters, such as spatial, hybrid or functional ones, can deliver more information about the surface [21]. ...
The article presents selected issues related to material quality manufactured by selective laser sintering of AlSi10Mg alloy powder after milling. The workpiece was prepared and machined by down-milling and up-milling with tools made of high-speed steel. Breaches, pores and failure-like cracks on the machined surface were found, which negatively influenced the values of 3D surface roughness parameters. The occurring phenomena were analyzed and proposals for their explanation were made. The results of this research describe the effect of cutting parameters (the feed rate of f = 0.013–0.05 mm/tooth) on the values of parameters describing the surface quality and benchmarks. Topography measurements and 3D surface roughness parameters are presented, as well as the results of microscopic surface analysis. It was found that for aluminum alloy produced by the direct metal laser sintering (DMLS) method, the recommended machining method is down-milling.
... The goal of the present work is a material measure to enable the overall assessment of a calibrated topography instrument for specific AM inspection tasks, conceptually similar to type AIR but reproducing the character of typical AM surfaces. Since real AM surfaces are naturally a hybrid of deterministic (weld structure) and stochastic (surface particles) [8], such a material measure would not fully replace the function of a conventional type AIR material measure, and certainly not the highly directional structure of a type PRO. The deterministic production of specific AM topographic features required for full replacement is still immature [1]. ...
The unique complex topography of additively-manufactured surfaces – and the recent rapid evolution of instruments and techniques to measure them – limits trust in inspection data, in direct conflict with the requirements of application areas such as aerospace, where failure of a part can have serious safety consequences. Topography instrument manufacturers and end-users require measurement standards with a controlled reproduction of representative additively-manufactured surfaces to calibrate, performance-verify and intercompare instruments for inspection tasks, thereby improving confidence in measurement. The design of such a surface texture measurement standard is reported, optimised for optical areal topography-measuring instruments and compatible with X-ray computed tomography instruments. Machined from an additively-manufactured blank, the standard’s four sides represent increasing levels of post-processing from the as-deposited surface. Datum features on the measurement standard facilitate direct comparison between topography instruments. Integrated step features support the calibration of an instrument’s Z scale. Calibration of a prototype of the standard is reported; the prototype is matched to a typical aerospace Scalmalloy TM additive manufacturing process. The calibration is also a trial application of a large-area chromatic confocal microscope; this instrument appears capable of calibrating relatively rough measurement standards if required to do so. Reference Ra and S -parameter measurements and associated measurement uncertainties are presented, correlation between parameters noted, and choice and consequences of filter settings discussed.
... The surface segmentation by means of WST is the basis for the derivation of the feature parameters, with which, for example, the contact area of the friction partners of a tribological system can be represented. Blateyron describes in detail their derivation and various applications [22,23]. The standardization of a feature-based evaluation method for profiles is in progress [24]. ...
The seal failure of an elastomer rotary shaft seal is often caused due to lead on the shaft counterface. In sealing technology, the term 'lead' includes all structures on sealing counterfaces that are capable of transporting fluid in axial direction through the sealing contact and thus disrupting the sealing mechanism. Lead structures are created during the manufacturing process of the shaft surface or throughout the handling. They occur in various shapes and sizes. Depending on the characteristics of the lead structures, several specialized measurement and evaluation methods exist which have to be applied in combination. However, not all types of lead can be covered with the methods known so far. State of the art are frequency-based and model-based analysis methods, which are only able to detect periodic lead structures. Aperiodic and stochastically distributed lead structures cannot be detected due to the functional principle. This article provides an approach for a structure-based evaluation of macroscopic lead structures based on optical topography measurement data. This allows to detect all known types of macroscopic lead on the shaft surface and in future to measure microscopic and macroscopic lead with a single measurement procedure.
... Topographic analysis of surfaces is used in many different areas of human life and activity, among which conventional and unconventional machining processes [9], tribology [10], wear [11] and friction [12] are the most frequently mentioned. There are many different techniques for digitizing surface in micro scale [13], with different advanced options of extracting interesting features [14,15]. Surface topography influences on adhesion and related processes, including energy phenomena [16]. ...
In the process of continuous improvement of manufacturing processes, this study was developed within the framework of the Ecovoss project, based on the inclusion of lightweight and new materials parts in the automotive sector. The objective was based on the replacement of aluminum welding operations with the option of adhesive operations with other types of materials such as polyamides or, in this case, a TEPEX® composite material (Dynalite 202-c200/50% TYP 13). The aim of this work is to test the best texturing of substrate made in 7075 aluminum specimens manufactured by robotic polishing with an ABB 6640 robot. Another substrate is TEPEX composite. A structural adhesive film AF-163-2 from the 3M company (St Paul, Minnesota, US) is used, which must be applied according to the manufacturing procedure. The tests carried out are based on the topographic measurement of the surfaces to be joined with an Alicona focus variation microscope, and the uniaxial shear tests of adhesive samples have been analyzed. The texture of the surface failure has been analyzed, and the results confirm a significant correlation between the texture parameters of initial surfaces and maximum shear stress. The expected results should provide a better understanding of the surfaces aimed to optimize the adhesion of the studied materials.
... Since then the technological rush has prompted into a digital manufacturing era with almost endless possibilities of 'true 3D', complex and multifunctional surfaces [14][15][16][17]. Furthermore, a new context for the instruments apt to measure the surface topography is available in the series ISO 25 178, based on the metrological characteristics [18,19]. ...
The assessment of the systematic behavior based on frequentist statistics was analyzed in the context of micro/nano metrology. The proposed method is in agreement with the well-known GUM recommendations. The investigation assessed three different case studies with definition of model equations and establishment of the traceability. The systematic behavior was modeled in Sq roughness parameters and step height measurements obtained from different types of optical microscopes, and in comparison with a calibrated contact instrument. The sequence of case studies demonstrated the applicability of the method to micrographs when their elements are averaged. Moreover, a number of influence factors, which are typical causes of inaccuracy at the micro and nano length scales, were analyzed in relation to the correction of the systematic behavior, viz. the amount of repeated measurements, the time sequence of the acquired micrographs and the instrument-operator chain. The possibility of applying the method individually to the elements of the micrographs was instead proven not convenient and too onerous for the industry. Eventually, the method was also examined against the framework of the metrological characteristics defined in ISO 25178-600 with hints on possible future developments.
... There is already a substantial literature in the measurement of surfaces produced by metal additive manufacturing and by powder bed fusion techniques, in particular [2]. It is generally recognized that complex, textured surfaces are poorly characterized or specified by conventional statistical parameters (see for example [3]). The classic literature on the impact of surface roughness on heat transfer (Moody's diagram) uses a simplified treatment of surface roughness, while powder bed fusion processes generate complex surfaces with a mixture of strongly anisotropic, periodic components and a population of individual features (pores and particles, for example), all of which may affect heat transfer and fluid flow. ...
Metal additive manufacturing (AM) offers the possibility of incorporating cooling channel geometry into components in high-temperature applications. Additionally, it has the prospect of optimizing cooling channel geometry unconstrained by geometric limitations of conventional machining processes. Such channels will necessarily have surfaces manufactured at various orientations resulting in different topographies that may influence heat transfer. Numerous studies have shown that conventional (amplitude) roughness parameters do not discriminate between topographies produced under different build conditions-but such descriptions have been used in studies of micro-channel, heat exchanger performance. The motivation behind this study is to explore the correlation between AM roughness characteristics (weld tracks amplitudes/wavelengths and their orientation, spatter, etc) and the resulting effect on heat transfer and pressure drop in fabricated microchannels. Computational Fluid Dynamics (CFD) models for mini-channels using StarCCM+ (a CFD code) were developed by acquiring the roughness data from the real AM surfaces with various roughness parameters such as different wavy patterns and the part orientation during the build. Simplified versions of measured surface topographies reduce the computational overhead. The pressure drops across the mini-channels and Nusselt (Nu) numbers were computed and analyzed for these cases under both laminar-and turbulent-flow conditions. Significant differences in the Nu numbers and pressure drops were observed across the different AM surfaces considered. Further CFD modeling of mini-channels with different wavy surfaces helped in exploring the suitable dimensions for the mini-channel experimental setup and also enabled exploration of the Reynolds number range to consider experimentally. Heat-balance considerations have been used to validate the current findings. An experimental setup is under development to compare models in an idealized setup. Initial results from the experiments are also described.
... The watershed segmentation method is also suitable for analysis of additively manufactured freeform surfaces [199]. Other applications are presented in reviews [200][201][202]. However, Zabala et al. [203] found a limited ability of the Spc parameter to characterise dental implant surfaces. ...
Areal 3D analysis of surface texture gives more opportunities than a study of 2D profiles. Surface topography evaluation, considered as 3D dimensional analysis in micro or nanoscales, plays an important role in many fields of science and life. Among many texture parameters, those connected with height are the most often used. However, there are many other parameters and functions that can provide additional important information regarding functional behaviour of surfaces in different applications. The knowledge about the functional importance of various surface properties is low. This review tries to fill this gap. Surface texture parameters are presented in various groups: height, spatial, hybrid, functional, feature, and others. Based on experiences of the present authors and literature review, the relationships among various surface parameters and functional properties are described. A proposal of a selection of parameters on the basis of their functional significations is provided. Considerations for future challenges are addressed.
... Since then the technological rush has prompted into a digital manufacturing era with almost endless possibilities of 'true 3D', complex and multifunctional surfaces [14]- [17], and with a new context for the instruments apt to measure the surface topography in the series ISO 25178 based on the metrological characteristics [18]- [19]. Even though different working principles exist, the metrological characteristics define sources of variation of the output in common to all the areal topography measuring instruments expressed as uncertainty contributors. ...
The brisk progression of the industrial digital innovation, leading to high degree of automation and big data transfer in manufacturing technologies, demands continuous development of appropriate off-line metrology methods to support processes' quality with a tolerable assessment of the measurement uncertainty. On the one hand specific-area references propose methods that are not yet well optimized to the changed background, and on the other, international general recommendations guide to effective uncertainty evaluation, but suggesting procedures that are not necessarily proven efficient at the micro- and nano-dimensional scale. The well-known GUM approach (i.e. frequentist statistics) was analyzed with the aim to test consistently its applicability to micro/nano dimensional and surface topography measurements. The investigation assessed three different clarifying situations, giving rise to consistent model equations, and to the achievement of the traceability. The choice of the cases provided a number of influence factors, which are typical liabilities at the micro and nano-length scale, and that have been related to the correction of the systematic behavior, viz. the amount of repeated measurements, the time sequence of the acquired micrographs and the instruments used. Such approach allowed the successful implementation of the GUM approach to micro/nano dimensional and topographic measurements, and also the appraisal of the level of efficacy of the method, its application limits and hints on possible future developments.
Average surface height and maximum amplitude can affect surface functions. In the industry, these parameters can be obtained based on profile measurements. However, variability in maximum profile height is high. A more stable parameter can be obtained from the results of the areal surface topography measurements as the average value of the parallel profiles. The aim of this study is to establish this parameter directly from the result of the areal surface texture by correcting the maximum surface height to material ratios in the range of 0.13–99.87%. This method was tested by measuring 100 surface topographies with a stylus profilometer and a white light interferometer. It can be utilized correctly for deterministic textures and random one- and two-process surfaces for which the correlation between neighboring profile ordinates is not very high. In other cases, the method should be modified. Employing this method, the maximum profile amplitude Pt and parameters characterizing the average profile height Pq, Pa, and the ratios Pq/Pa and Pp/Pt describing the shape of the profile ordinate distribution can be correctly estimated. Pq/Pa and Pp/Pt were more stable than the kurtosis Pku and skewness Psk. The corrected maximum height S±3σ can be adopted as a parameter that characterizes the areal surface texture as more stable than the maximum surface height St. Pq/Pa and Pp/Pt were more steady than kurtosis Pku and skewness Psk.
For technical surfaces, it is important to know their functional purpose and to characterize them accordingly. Therefore, ISO 21920-2 in 2D and ISO 25178-2 in 3D offer parameters that can assess surface functional properties. The topographic portions of a surface, for example hills and dales, can be classified as features and evaluated using feature parameters. However, no parameter exists to describe the spatial distribution of features with regard to the degree of homogeneity for aperiodic surfaces. Here we show the application of the Delaunay triangulation to quantify the spatial distribution respectively the geometric relationship of features. Therefore, the feature points are determined by watershed analysis and the resulting point cloud is meshed in 2D. Based on that mean and standard deviation of the triangle side lengths and the area disorder (AD) are calculated as new parameters. The method is demonstrated for sandblasted and chrome-plated specimens. In addition simulation is used to generate more data for analysis. With the proposed approach the distinction and extent of uniform, homogeneous or inhomogeneous spatial distributions of features with parameter AD can be determined.
Laser powder bed fusion (LPBF) is increasingly used to produce metal industrial components for high value-added sectors, such as aerospace, automotive and biomedical. However, mechanical and structural properties of LPBF parts are often hindered by the large quality variability, poor geometrical and dimensional characteristics, complex surface texture and low density. The quality of the feedstock material is an important aspect to be taken into account, as it significantly influences such possible issues. In particular, metal powder used in LPBF should have shape and size distribution designed to facilitate good flowability, spreading and packing behaviour, so that the final fabricated parts have acceptable density, surface finish and mechanical properties. This work focuses on the accuracy of simultaneous measurement of powder size and shape from three-dimensional reconstructions obtained by X-ray computed tomography (CT). Results of CT measurements are compared with results from other methods based on laser diffraction and scanning electron microscopy. Different materials and powder morphologies were investigated. In addition, the CT-measured powder characteristics can be used to improve other CT analyses of LPBF parts.
3D topography metrology of optical micro-structured surfaces is critical for controlled manufacturing and evaluation of optical properties. Coherence scanning interferometry technology has significant advantages for measuring optical micro-structured surfaces. However, the current research faces difficulties of designing high accuracy and efficient phase shifting, and characterization algorithms for optical micro-structured surface 3D topography metrology. In this paper, parallel unambiguous generalized phase-shifting and T-spline fitting algorithms are proposed. To avoid phase ambiguity and improve the accuracy of the phase-shifting algorithm, the zero-order fringe is determined by the iterative envelope fitting with Newton’s method, and the accurate zero optical path difference is determined by a generalized phase-shifting algorithm. In particular, the calculation procedures of the multithreading iterative envelope fitting with Newton’s method and generalized phase shifting are optimized with the graphics processing unit-Compute Unified Device Architecture kernel function. Additionally, to fit the base form of optical micro-structured surfaces and characterize the surface texture and roughness, an effective T-spline fitting algorithm is proposed by optimizing the preimage of the T-mesh with image quadtree decomposition. Experimental results show that the surface reconstruction of optical micro-structured surfaces using the proposed algorithm is more accurate, and the efficiency is 10 times higher than that of current algorithms; the time of the surface reconstruction is less than 1 s. Compared with the current B-spline method, the accuracy of roughness characterization using the proposed T-spline algorithm is improved by more than 10%.
The manufacturing process defines not only the component’s geometry, but also how its surface senses and interacts with the outside world via its topography. Every manufactured surface is rough, but the component can benefit from the roughness control. Topography in functional surfaces is optimized either by controlling the manufacturing parameters or by post-manufacturing surface patterning technologies. However, how are topographic features measured and characterized? How do rough surfaces contact each other? What happens if fluid is present at the contact interface? And what are the mechanisms that correlate surface topography and its functionalities? This article will cover the engineering of surface topography in manufacturing by addressing empirical advancements and scientific understanding in the field. The functionalities covered are adhesion, friction, and convective heat transfer. Relatively large surface structures used for heat transfer mainly take advantage of recent advances in additive manufacturing, while conventional manufacturing processes and deterministic surface patterning techniques are discussed for the control of adhesion and friction.Graphical abstract
Quantitative characterization and uncertainty evaluation of areal step height are of increasing importance for semiconductor manufacturing. However, step characterizations often confront problems of repeatability and reproducibility due to fitting of upper and lower planes. To solve this problem, we propose a cluster-based method for step height characterization and uncertainty evaluation. By data reconstruction and
$K$
-means clustering, our method converts characterizing steps into approximating Euclidean distances, without necessity to fit planes. Moreover, it can evaluate uncertainties simultaneously with parameterization. The proposed method is first validated with synthetic data. Then, two experiments, respectively, on nominal 5
$\mu \text{m}$
and 90 nm standard artifacts are carried out. The characterization results highly conform to the calibrated values, with 0.0986% and 1.22% differences, respectively. Comparing to the latest ISO method, the cluster-based method presents better performance on repeatability and reproducibility. The experimental results demonstrate that the method works well for measurement either with or without outliers.
The structure of deep neural networks (DNNs) used in triangulation displacement sensors was investigated via numerical and experimental analyses. After measuring the fluctuation of the actual measurements in experiments, a numerical model of the measurements was constructed by adding normally distributed noise to the ideal waveform to build a training data set. The structure of the DNNs was optimized by evaluating the major components of the DNNs by numerical calculations. The DNNs were then installed in a measurement system for distance measurement with sub-pixel accuracy.
White light interferometry (WLI) is a widely used technique in various research fields because it can quickly measure the topography of a sample over a large area. In conventional WLI, the topography of the sample is generally obtained by using the envelope of the interferogram. However, this method cannot determine the precise order of the fringes because it is very sensitive to longitudinal chromatic aberration which may cause several measurement errors. Here, we propose an algorithm for avoiding errors in the measurement of the sample’s topography. The concept of the peak matching algorithm and the development of a new scheme of acquiring the topography of the sample by using a color charge-coupled device (CCD) is proposed. We demonstrate that our method can reject the fringe distortion problem encountered when using a conventional WLI system to measure the discrete sample surface. We expect our method to be applied to a variety of research and in industrial fields that require precise topographic measurements.
Die Dichtungsgegenlauffläche ist ein wichtiger Bestandteil des tribologischen Dichtsystems „Radial-
Wellendichtung“. Ein wesentliches Gütekriterium einer Dichtungsgegenlauffläche ist die „Drallfreiheit“, denn
Drallstrukturen können im Betrieb eine Förderwirkung von Fluid in axialer Wellenrichtung erzeugen.
Drehrichtungsabhängige Folgen können Mangelschmierung oder Leckage sein und bis hin zum Ausfall des
ganzen Dichtsystems führen. Um zu überprüfen, ob nach dem Herstellungsprozess Drall auf der
Dichtungsgegenlauffläche vorhanden ist, muss die Wellenoberfläche zunächst messtechnisch erfasst
werden. Anschließend werden die Drallstrukturen in den Messdaten lokalisiert.
Das Projekt FVA 876 I „3D-Makrodrall“ verfolgt einen neuen s.g. strukturbasierten Ansatz zur Messung und
Analyse von makroskopischen Drallstrukturen. Makroskopische Drallstrukturen werden in den periodischen
und die Welle umlaufenden Makrodrall sowie in die Mikrowelligkeit untergliedert. Der Begriff Mikrowelligkeit
umfasst dabei alle aperiodischen und stochastisch verteilten makroskopischen Oberflächenstrukturen auf
der Dichtungsgegenlauffläche. Ziel des Projektes ist es, makroskopische Drallstrukturen vollumfänglich zu
messen und auszuwerten.
Zu diesem Zweck wurde im Projektverlauf eine strukturbasierte Auswertungsmethode entwickelt, um
makroskopische Drallstrukturen auf optisch gemessen, hochauflösenden Oberflächentopographien zu
lokalisieren und anschließend zu beschreiben. Die strukturbasierte Herangehensweise bietet den Vorteil,
jede gemessen Struktur zu analysieren und anschließend die Gesamtheit aller erfassten Strukturen
statistisch zu betrachten. Hieraus ergeben sich neue Möglichkeiten, die Dichtungsgegenlauffläche besser
und zielgerichteter beschreiben zu können.
Des Weiteren wurden systematisch die erforderlichen Messbedingungen wie bspw. die notwendige
Messfeldgröße, die Auflösung, die Anzahl der Messungen sowie die Positionen der entsprechenden
Messstellen erforscht. Darauf basierend wurde ein Messraster zur optischen Vermessung der
Dichtungsgegenlauffläche für die 3D-Makrodrall Analyse festgelegt. In diesem Zuge wurde außerdem die
grundsätzliche Eignung von zwei verschiedenen optischen Messsystemen untersucht und damit gezeigt,
dass strukturbasierte Auswertungsmethoden mit den Messdaten verschiedener Messgeräte und
Messmethoden angewendet werden können.
The noncontact optical probe-based surface scanning is promising for the measurement of complex-shaped optical surfaces. In this study, by combining a chromatic confocal sensor and a planar nano-positioning stage, a sub-aperture scanning and stitching method is developed for the noncontact measurement of the microstructured optical surfaces, with the measured form accuracy being irrespective of the accuracy of the global scanning stage. After the scanning, the Gaussian process-based denoising is employed to remove the measurement noises, and a hybrid registration algorithm is proposed to achieve a 6-DOF alignment of any neighbored sub-apertures. For the registration, the differential evolution-based minimization is implemented to find a coarse transformation which then serves as the initial value for the iterative closest point-based fine registration. The hybrid method is beneficial in finding an optimal registration with a greatly reduced computation burden. Finally, the effectiveness of the developed measurement system, as well as the stitching algorithm, is comprehensively demonstrated through practically measuring a sinusoidal micro-grid surface. © 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.
The wetting state of a water droplet remarkably affecting its sliding behavior is characterized by the droplet boundary contact line. This paper presents experimental studies of the apparent contact angle against droplet deposition time, as well as contact angle hysteresis, and compares the results with the Wenzel and Cassie-Baxter models. Observations indicate that different intermediate wetting phenomena exist. The sliding performance of a droplet under intermediate wetting states is also investigated. It is found that the droplet does not slide under partial wetting but slides when the side walls of the grooves have been wetted by part of the droplet. Further, that droplets under different wetting states on surfaces with varied groove spacing and widths, under the same groove spacing to width ratio, present altered sliding performance before rolling off from the micro-grooves in a parallel direction. This study broadens the characterization method of intermediate wetting states, which determines the condition of anisotropic sliding on micro-grooves. The findings have great potential for application to artificial self-cleaning surfaces.
We consider the problem of partitioning a set of m points in the n-dimensional Euclidean space into k clusters (usually m and n are variable, while k is fixed), so as to minimize the sum of squared distances between each point and its cluster center. This formulation is usually the objective of the k-means clustering algorithm (Kanungo et al. (2000)). We prove that this problem in NP-hard even for k = 2, and we consider a continuous relaxation of this discrete problem: find the k-dimensional subspace V that minimizes the sum of squared distances to V of the m points. This relaxation can be solved by computing the Singular Value Decomposition (SVD) of the m × n matrix A that represents the m points; this solution can be used to get a 2-approximation algorithm for the original problem. We then argue that in fact the relaxation provides a generalized clustering which is useful in its own right.Finally, we show that the SVD of a random submatrix—chosen according to a suitable probability distribution—of a given matrix provides an approximation to the SVD of the whole matrix, thus yielding a very fast randomized algorithm. We expect this algorithm to be the main contribution of this paper, since it can be applied to problems of very large size which typically arise in modern applications.
Feature characterization of rough surfaces is of growing interest in terms of a function oriented description of technical surfaces. Feature characterization requires a segmentation of significant hills and dales of the measured profile. The segmentation can be done in several ways. One method is the so called crossing-the-line segmentation which will be part of ISO 16610 part 45 and ISO 21920 part 2. The crossing-the-line segmentation described in this publication represents an extension of the algorithm proposed by Scott (Scott P, 2006, Meas. Sci. Technol. 17 , 559–564) and is based on new knowledge gathered over the last ten years. As an example, the feature parameters R S m and R c according to ISO 4287:1997 are evaluated.
With the advancement of modern enabling technologies, surfaces of high value-added products are changing from traditional simple geometries to complex geometries that feature freeform shapes. The analysis of topographical features on freeform surfaces is challenging because surface shapes are no longer planar and measurement data often require surface description in the form of triangular meshes. An approach is proposed to extend the watershed segmentation from planar surfaces to freeform surfaces. Surface topography is first extracted from measured surfaces (mesh surfaces) using proper mathematical operations, e.g. fitting and filtration. The watershed segmentation based on Maxwell’s theory is extended to 3D triangular meshes and applied to the extracted surface topography defined as a scalar function associated with the vertices of the mesh surface. Critical surface points such as peaks, pits and saddles are identified to construct a Pfaltz graph. Ridge lines and course lines are then traced starting from saddles and following the steepest uphill and downhill paths to peaks and pits, respectively. Wolf pruning of the change tree is employed to merge over-segmented regions. The extended watershed segmentation method is applied to segment surface topography of the additively processed scaffold and lattice surfaces.
We propose a microlens array (MLA) construction method based on sub-channel optimal design and splicing, and an integrated projection imaging analysis method by using ray tracing and image warping. Our stop mask greatly improves imaging quality and eliminates crosstalk. We realize various projection distances, required projection imaging dimensions, and design optimization of sub-lens structures, providing freedom and possibility for MLA structure design requirements. Optical system chief ray tracing and sub-image generation is combined by using radial basis function forward image warping. Imaging distortion and overlap misalignment from short focal projection, multi-aperture offset, and complicated surfaces are perfectly corrected. Sub-image warping pixel mapping facilitates real-time replacement of projected images. We conduct substantial MLA integration imaging designs and precision analysis of different sub-aperture sizes, MLA sizes, and projection distances.
In manufactured microfluidic channels, geometrical imperfections resulting from the manufacturing process are challenging in terms of reliability and functionality of the microfluidic device. In this work, a methodology for the geometrical and dimensional characterization of microfluidic channels using quantitative 3D optical microscopy is proposed. The methodology is based on a holistic approach including the identification of functionally relevant geometrical features and critical dimensions at design stage, as well as the related verification process at the manufacturing stage. At design stage, the critical geometrical characteristics are identified on the basis of their relation with the performance of the microfluidic device. Verification is based on a novel methodology in which measurement results collected by a surface topography measuring instrument are processed on the basis of concepts and procedures commonly applied to data generated by a coordinate measuring system. The method is presented using as an example the characterisation of a microfluidic channel realized by soft lithography and constituting part of a membrane micro valve. The geometry of the microfluidic channel is acquired by using an imaging confocal microscope.
Illumination for line-scan machine vision systems is required to produce a highly asymmetric elliptical beam pattern, to maximize system speed and accuracy. The use of LED emitters with symmetric Lambertian emission patterns is challenging in this context, requiring significant beam reshaping. A design for a collimated line-light, with long working distance, utilizing LEDs with symmetric Lambertian emission patterns, is presented. Using a combination of Fresnel lenses and total internal reflection (TIR) optics, an elliptical beam with a high degree of collimation is achieved. TIR elements are designed based on an adaptation of a freeform lens design method published by Chen et al. [Opt. Express 20, 10 (2012)]. Practical performance of the design is verified experimentally using a prototype unit. In addition, the design is compared, using ray tracing software, to line-lights constructed using commercially available symmetric and elliptical TIR lenses, and its superior performance is confirmed. The optical design described is fully manufacturable and suitable for both small and large scale production.
Powder bed fusion (PBF) is a popular additive manufacturing (AM) process with wide applications in key industrial sectors, including aerospace, automotive, healthcare, defence. However, a deficiency of PBF is its low quality of surface finish. A number of PBF process variables and other factors (e.g. powders, recoater) can influence the surface quality. It is of significant importance to measure and characterise PBF surfaces for the benefits of process optimisation, product performance evaluation and also product design. A state-of-the-art review is given to summarise the current research work on the characterisation of AM surfaces, particularly PBF surfaces. It is recognised that AM processes are different from conventional manufacturing processes and their produced surface topographies are different as well. In this paper, the surface characterisation framework is updated to reflect the unique characteristics of PBF processes. The surface spatial wavelength components and other process signature features are described and their production mechanisms are elaborated. A bespoke surface characterisation procedure is developed based on the updated framework. The robust Gaussian regression filter and the morphological filters are proposed to be used for the separation of the waviness component due to their robustness. The watershed segmentation is enhanced to extract globules from the residual surface. Two AM components produced by electron beam melting (EBM) and selective laser melting (SLM), are measured and characterised by the proposed methodology. Both of the two filters are qualified for the extraction of melted tracks. The watershed segmentation can enable the extraction of globules. The standard surface texture parameters of different surface wavelength components are compared. A set of bespoke parameters are intentionally developed to offer a quantitative evaluation of the globules.
Areal optical surface topography measurement is an emerging technology for industrial quality control. However, neither calibration procedures nor the utilization of material measures are standardized. State of the art is the calibration of a set of metrological characteristics with multiple calibration samples (material measures). Here, we propose a new calibration sample (artefact) capable of providing the entire set of relevant metrological characteristics within only one single sample. Our calibration artefact features multiple material measures and is manufactured with two-photon laser lithography (direct laser writing, DLW). This enables a holistic calibration of areal topography measuring instruments with only one series of measurements and without changing the sample.
Roll-to-roll (R2R) processing on film substrates has been demonstrated to have the potential for achieving high throughput manufacturing of organic electronic systems at low cost. However, the ever-growing mobile devices market accompanied by the developments in information and communication technologies require high performance systems at very low power operation, sometimes on larger substrates having sizes in the range of a few metres. Organic electronics often fall short of fulfilling the required computing performance and power requirements of most of the common use cases. Hybrid integration of inorganic monocrystalline silicon chips on polymer films is a means to fulfil the aforementioned requirements. In this context, it is opportune to report our recent activities on R2R processing of plastic films for hybrid integration of flexible electronics. Hybrid integration can be performed with conventional, rigid surface mount devices as well as flexible, ultra-thin bare silicon chips. The first section of the paper is dedicated to a brief overview of R2R manufacturing of electronic devices with an example of production of radio frequency identification tags as well as to a discussion emphasising the targets for hybrid integration. Then, detailed descriptions about our processes for R2R manufacturing of metal wiring lines on films and hybrid integration are included. Three-dimensional integration of films and a temperature sensor label manufactured using hybrid integration process are also elaborated on. Furthermore, key results from fatigue reliability assessment of R2R metallised wiring lines are reported. Finally, some of the challenges in transferring the R2R processes for hybrid integration on film substrates from research labs to industrial manufacturing are highlighted.
Traceability in micro-metrology requires an infrastructure of accredited metrology institutes, effective performance verification procedures, and task specific uncertainty estimation. Focusing on the latter, this paper proposes an approach for the task specific uncertainty estimation based on simulation for a generic 3D microscope. The proposed simulation approach is based on the identification and a successive parameter estimation of an empirical model of measured points. The model simulates the probing error of the 3D microscope based on a Gaussian process model, thus including the correlation among close points. Parameters for the error simulation are estimated by a deep analysis of error sources of the 3D microscope. Validations of the proposed simulation approach are carried out in the case of focus variation microscopy (FVM), considering several case studies. The procedure proposed in the ISO/TS 15530-4 standard are applied for validation.
Efficient sampling methods enable the reconstruction of a generic surface with a limited amount of points. The reconstructed surface can therefore be used for inspection purpose. In this paper a sampling method that enables the reconstruction of a curve or surface is proposed. The input of the proposed algorithm is the number of required samples. The method takes into account two factors: the regularity of the sampling and the complexity of the object. A higher density of samples is assigned where there are some significant features, described by the curvature. The analysed curves and surfaces are described through the B-splines spaces. The sampling of surfaces generated by two or more curves is also discussed.
The use of state-of-the-art areal topography measurement instrumentation allows for a high level of detail in the acquisition of topographic information at micrometric scales. The three-dimensional geometric models of surface topography obtained from measured data create new opportunities for the investigation of manufacturing processes through characterisation of the surfaces of manufactured parts. Conventional methods for quantitative assessment of topography usually only involve the computation of texture parameters; summary indicators of topography-related characteristics that are computed over the investigated area. However, further useful information may be obtained through characterisation of signature topographic formations, as more direct indicators of manufacturing process behaviour and performance. In this work, laser powder bed fusion of metals is considered. An original algorithmic method is proposed to isolate relevant topographic formations and to quantify their dimensional and geometric properties, using areal topography data acquired by state-of-the-art areal topography measurement instrumentation.
The challenges of measuring the surface topography of metallic surfaces produced by additive manufacturing are investigated. The differences between measurements made using various optical and non-optical technologies, including confocal and focus-variation microscopy, coherence scanning interferometry and x-ray computed tomography, are examined. As opposed to concentrating on differences which may arise through computing surface texture parameters from measured topography datasets, a comparative analysis is performed focussing on investigation of the quality of the topographic reconstruction of a series of surface features. The investigation is carried out by considering the typical surface features of a metal powder-bed fusion process: weld tracks, weld ripples, attached particles and surface recesses. Results show that no single measurement technology provides a completely reliable rendition of the topographic features that characterise the metal powder-bed fusion process. However, through analysis of measurement discrepancies, light can be shed on where instruments are more susceptible to error, and why differences between measurements occur. The results presented in this work increase the understanding of the behaviour and performance of areal topography measurement, and thus promote the development of improved surface characterisation pipelines.
Selective laser melting (SLM) of metals produces surface topographies that are challenging to measure. Multiple areal surface topography measurement technologies are available, which allow reconstruction of information rich, three-dimensional digital surface models. However, the capability of such technologies to capture intricate topographic details of SLM parts has not yet been investigated. This work explores the topography of a SLM Ti6Al4V part, as reconstructed from measurements by various optical and non-optical technologies. Discrepancies in the reconstruction of local topographic features are investigated through alignment and quantitative assessment of local differences. ISO 25178-2 areal texture parameters are computed as further comparison indicators.
In this paper, the state of art of ultrasonicassisted machining technologies used for fabrication of micro/nano-textured surfaces is reviewed. Diamond machining is the most widely used method in industry for manufacturing precision parts. For fabrication of fine structures on surfaces, conventional diamond machining methods are competitive by considering the precision of structures, but have limitations at machinable structures and machining efficiency, which have been proved to be partly solved by the integration of ultrasonic vibration motion. In this paper, existing ultrasonic-assisted machining methods for fabricating fine surface structures are reviewed and classified, and a rotary ultrasonic texturing (RUT) technology is mainly introduced by presenting the construction of vibration spindles, the texturing principles, and the applications of textured surfaces. Some new ideas and experimental results are presented. Finally, the challenges in using the RUT method to fabricate micro/ nano-textured surfaces are discussed with respect to texturing strategies, machinable structures, and tool wear.
Many applications that exploit the manufacturing flexibility of additive manufacturing (AM) produce surfaces, primarily internal features, which cannot be measured using conventional contact or line-of-sight optical methods. This paper evaluates the capability of a novel technique to extract areal surface data from micro-focus x-ray computed tomography (XCT) from AM components and then generate surface parameter data per ISO 25178-2. This non-destructive evaluation of internal features has potential advantages during AM product research and commercial production. The data extracted from XCT is compared with data extracted using a focus variation instrument. A reference dimensional artefact is included in all XCT measurements to evaluate XCT surface determination performance and dimensional scaling accuracy. Selected areal parameters generated using the extraction technique are compared, including Sa, for which the nominal difference between the value obtained using XCT and used the focus variation method was less than 2.5%.
In this review, the use of x-ray computed tomography (XCT) is examined, identifying the requirement for volumetric dimensional measurements in industrial verification of additively manufactured (AM) parts. The XCT technology and AM processes are summarised, and their historical use is documented. The use of XCT and AM as tools for medical reverse engineering is discussed, and the transition of XCT from a tool used solely for imaging to a vital metrological instrument is documented. The current states of the combined technologies are then examined in detail, separated into porosity measurements and general dimensional measurements. In the conclusions of this review, the limitation of resolution on improvement of porosity measurements and the lack of research regarding the measurement of surface texture are identified as the primary barriers to ongoing adoption of XCT in AM. The limitations of both AM and XCT regarding slow speeds and high costs, when compared to other manufacturing and measurement techniques, are also noted as general barriers to continued adoption of XCT and AM.
Multiscale structured surfaces are a way to provide advanced, otherwise not attainable functionality on a technical part. Applications of such parts can be manifold, and numerous works have already covered the transfer of natural examples into bio-inspired surfaces or the geometrical and functional metrology of such surfaces. After briefly presenting typical functionalities of multiscale structured surfaces, this keynote paper will focus on the available manufacturing processes and review their capabilities to generate multiscale structured surfaces. To compare such processes, the so-called “multiscality” is defined that characterizes the structured surfaces according to the lateral and vertical extent of the individual stacked elements and is used as a first indicator to assess the difficulty of their manufacture. As the boundaries of what is considered a multiscale structure are diffuse, ranges of low, medium and high multiscality are defined instead. After presenting the state of the art of manufacturing processes currently utilized for the manufacture of (not only multiscale) structured surfaces, this keynote paper summarizes the capabilities of single-step and multi-step/multi-physics approaches for their applicability across different scales and gives an outlook on which processes could potentially become relevant in the future.
The chapters of this volume are based on talks given at the eleventh international Sampling Theory and Applications conference held in 2015 at American University in Washington, D.C. The papers highlight state-of-the-art advances and trends in sampling theory and related areas of application, such as signal and image processing. Chapters have been written by prominent mathematicians, applied scientists, and engineers with an expertise in sampling theory. Claude Shannon’s 100th birthday is also celebrated, including an introductory essay that highlights Shannon’s profound influence on the field. The topics covered include both theory and applications, such as:
• Compressed sensing
• Non-uniform and wave sampling
• A-to-D conversion
• Finite rate of innovation
• Computational neuroscience
• Time-frequency analysis
• Operator theory
• Mobile sampling issues
Sampling: Theory and Applications is ideal for mathematicians, engineers, and applied scientists working in sampling theory or related areas.
Definition of "stratified surface" in the CIRPedia, CIRP Encyclopedia of Production Engineering.
The study of how surface topography is affected by build orientation is important for understanding the capability of metal additive manufacturing (AM) processes, such as those based on powder bed fusion. Due to the layer-based nature of the process, surfaces built at varying orientations will be differently affected by a wide array of process-induced topographic modifications, including the staircase effect, and the presence of protruded formations (spatter, un-melted or partially melted particles) in some cases significantly occluding the underlying topography. All such process-induced topographic modifications can significantly influence the choices for surface post-processing. Most research investigating surface texture in metal AM has focused on laser powder bed fusion (LPBF) [1-6].Whilst electron beam powder bed fusion (EBPBF) is somewhat similar [7], it features some rather significant differences in the surfaces it produces [4,5,8]. To assess the topography of AM surfaces as a function of orientation, most researchers [1-6,8] have investigated surface texture parameters (profile-ISO 4287 [9] and areal-ISO 25178-2 [10]). In parallel to studying surfaces as a function of orientation, recent work on metal AM has investigated ways to describe the complex topography of additive surfaces via approaches alternative to texture parameters, focusing on the characterisation of topographic formations that populate the typical metal additive surface (weld tracks, spatter formations, particles) [11-13]. These approaches can be collectively referred to as feature-based characterisation. In this work, the topography of EBPBF surfaces as a function of orientation was investigated using a combined approach including both texture parameters and feature-based characterisation. A Ti6Al4V test part (125 × 125 × 25) mm was manufactured using EBPBF with an Arcam A2XX and designed to possess 36 sides to produce surfaces with orientations varying in 10° increments (0°, 10°, 20°, etc.) (Figure 1a). The surfaces were left in their as-built state, except for minimal post-processing, which consisted of grit blasting, typically applied to remove the sintered cake within the EBPBF process. All support structures were removed. The custom characterisation approach featured multiple steps, beginning with the automated identification and separation of all the protruding formations (spatter, partially melted and un-melted particles), such as those Abstract submitted to the www.metprops2019.org conference
A key challenge of meta-surface research is locally controlling at-will nano-scale geometric features on meter-scale apertures. Such a technology is expected to enable large aperture meta-optics, and revolutionize fields such as long-range imaging, lasers, LADARs, and optical communications. Furthermore, these applications are often more sensitive to light-induced and environmental degradation, which constrains the possible materials and fabrication process. Here, we present a relatively simple and scalable method to fabricate a substrate-engraved meta-surface, with the locally-printed index determined by the induced illumination, and therefore addresses both the challenges of scalability and durability. In this process, a thin metal film is deposited onto a substrate and transformed into a mask via local laser-induced dewetting into nanoparticles. The substrate is then dry-etched through this mask and selective mask removal finally reveals the meta-surface. We show that the masking by the local nano-particle distribution, and therefore the local index, is dependent on the local light-induced dewetting temperature. We demonstrate a printing of a free-form pattern engraved into a fused silica glass substrate using a laser raster scan. Large scale spatially controlled engraving of metasurfaces has implications on other technological fields beyond optics, such as surface fluidics, acoustics, and thermo-mechanics.
The needs, requirements, and ongoing and future research issues in geometrical metrology for metal additive manufacturing are addressed. The infrastructure under development for specification standards in AM is presented, and the research on geometrical dimensioning and tolerancing for AM is reviewed. Post-process metrology is covered, including the measurement of surface form, texture and internal features. In-process requirements and developments in AM are discussed along with the materials metrology that is pertinent to geometrical measurement. Issues of traceability, including benchmarking artefacts, are presented. The information in the review sections is summarized in a synthesis of current requirements and future research topics.
Micro-structured functional surfaces have achieved widespread applications in various advanced scientific, technological, industrial, and engineered fields due to their excellent performances, which are vitally limited by their feasible fabrication. Currently, ultra-precision machining, typically including ultra-precision diamond turning, ultra-precision diamond milling, ultra-precision diamond scratching, ultra-precision grinding, and ultra-precision polishing, is developed as a very-promising solution for the micro-structured functional surface fabrication with high quality, high efficiency, high flexibility, and low cost. Therefore, this paper aims to briefly review the current state of the art in the investigation into ultra-precision machining characteristics of micro-structured functional surfaces with a focus on their typical advanced applications as the significant achievements of their ultra-precision machining fabrication, discuss the key challenges, and further provide new insights into ultra-precision machining of micro-structured functional surfaces for the future research and their further advanced applications.
The Handbook of Surface and Nanometrology explains and challenges current concepts in nanotechnology. It covers in great detail surface metrology and nanometrology and more importantly the areas where they overlap, thereby providing a quantitative means of controlling and predicting processes and performance. Trends and mechanisms are explained with numerous practical examples. Bringing engineering and physics together at the nanoscale reveals some astonishing effects: geometric features such as shape change meaning; roughness can disappear altogether; signals from instruments have to be dealt with differently depending on scale. These and other aspects are dealt with for the first time in this book. It is relevant not only for today's technology but also for future advances. Many aspects of nanotechnology and precision engineering are considered in chapters on manufacture, characterization, standardization, performance and instrumentation. There is a special chapter on nanometrology and this subject permeates the whole book. The Handbook of Surface and Nanometrology is the only book that covers these subject areas and is the definitive work in this field. This book is indispensable for firms making, trading, and researching semiconductor devices, MEMS, and micro-optics, as well as tradition precision engineering products. It will also be useful in quality control as well as for research scientists, development engineers, and production managers.
Hybrid micro-optics of infrared (IR) materials are of great advantage in realizing the function integration and minimization of advanced IR optical systems. However, due to the hard-and-brittle nature of IR materials, it is still challenging for both non-mechanical and mechanical technologies to achieve one-step generation of hybrid infrared micro-optics with high form accuracy. In the present study, a flexible method, namely ultra-precision side milling (UPSM), is first introduced to achieve one-step generation of infrared hybrid microoptics in ductile mode, and the corresponding reflective diffraction characteristics are analyzed. In UPSM, the reflective/refractive primary surface of the hybrid micro-optics is formed via the removal of workpiece material, and the high-frequent secondary diffractive micro/nanostructures are simultaneously generated by the tool residual marks of cutting trajectories. With the consideration of the changing curvature of the primary surface, the optimal toolpath generation strategy is introduced to acquire the desired shapes of the secondary micro/nanostructures, and the selecting criteria of the machining parameters is discussed to avoid the brittle fractures of IR materials. In practice, two types of hybrid microoptic components, namely hybrid micro-aspheric arrays and sinusoid grid surface with highfrequent secondary unidirectional phase gratings, are successfully fabricated on single-crystal silicon to validate the proposed method. The method adopted in this study is very promising for the deterministic fabrication of hybrid micro-optics on infrared materials. © 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.
Atomic force microscopes (AFMs) are commonly and broadly regarded as being capable of three-dimensional imaging. However, conventional AFMs suffer from both significant functional constraints and imaging artifacts that render them less than fully three dimensional. To date a widely accepted consensus is still lacking with respect to characterizing the spatial dimensions of various AFM measurements. This paper proposes a framework for describing the dimensional characteristics of AFM images, instruments, and measurements. Particular attention is given to instrumental and measurement effects that result in significant non-equivalence among the three axes in terms of both data characteristics and instrument performance. Fundamentally, our position is that no currently available AFM should be considered fully three dimensional in all relevant aspects.
The Image Processing Handbook covers two-dimensional (2D) and three-dimensional (3D) imaging techniques, image printing and storage methods, image processing algorithms, image and feature measurement, quantitative image measurement analysis, and more. Incorporating image processing and analysis examples at all scales, from nano- to astro this Seventh Edition: Features a greater range of computationally intensive algorithms than previous versions Provides better organization, more quantitative results, and new material on recent developments. Includes completely rewritten chapters on 3D imaging and a thoroughly revamped chapter on statistical analysis. Contains more than 1700 references to theory, methods, and applications in a wide variety of disciplines. Presents 500+ entirely new figures and images, with more than two-thirds appearing in color.
Textures are abundantly exploited in nature for securing superior functionalities including adhesion, color manipulation, anti-reflection, and drag management. Over millions of years, these advanced properties are endowed to various organisms on the planet to survive and adapt in harsh environmental conditions. Texture characteristics such as feature size, shape, periodicity, aspect ratio, orientation and hierarchy are critical in nature's ‘tool-box’. Manufacturing of cutting-edge products require multi-functionalities for efficiency, durability and sustainability for improving the quality of life of growing population. This paper analyzes and discusses convergence and underlying science and engineering of well proven natural strategies of surface textures and their effective synthetic implementation in engineered products.
One of the major issues of the micro-milling operations pertains to burrs formation, which affects the quality of the final product, and, thus, the capability to meet the part desired performances. Burrs characterization and evaluation are still a challenging task in micro-machining, especially if on-machine monitoring of burrs is desired. This paper proposes a newly developed method based on optical microscopy, a-priori information on the manufacturing process, and an unconventional use of void pixels for fast and non-destructive evaluation of multiple geometrical quantities. Newly defined parameters on burrs lateral distribution and axial depth of cut are presented in addition to the standard surface texture parameters. The proposed methodology is applied to slotting micro-milling operations on pure titanium grade II. The obtained results show the method potential that can be exploited for on-machine monitoring of micro-milling operations.
This work studies multiscale analyses and characterizations of surface topographies from the engineering and scientific literature with an emphasis on production engineering research and design. It highlights methods that provide strong correlations between topographies and performance or topographies and processes, and methods that can confidently discriminate topographies that were processed or that perform differently. These methods have commonalities in geometric characterizations at certain scales, which are observable with statistics and measurements. It also develops a semantic and theoretical framework and proposes a new system for organizing and designating multiscale analyses. Finally, future possibilities for multiscale analyses are discussed.
In this paper a FORTRAN subroutine for the generalization of the topological structure of
topographic surfaces is presented. The surface topology is characterized by weighted surface networks (Pfaltz-graphs) which represent special types of graphs with the vertex sets consisting of the critical or so-called surface-specific points (pits, passes, peaks) and the edge sets consisting of the critical or so-called surface-specific lines (ridges, courses) of the corresponding topographic surfaces: in addition, real numbers greater than zero are associated with the edges and vertices in order to indicate their importance for the macro- and microstructure of the underlying surface. The so-defined weighted surface networks can be condensed by two graph-theoretic contractions which reduce the number of edges and nodes but preserve the topological structure of the associated Pfaltz-graphs and consequently that of the corresponding topographic surfaces; thus the two contractions are equivalent to elementary steps of a cartographic generalization process. The procedure presented in this article is the FORTRAN equivalent of an
algorithm resting on these two contractions and thus being able to condense a given topographic surface until a specified degree of simplicity is achieved.
Nanomanufacturing involves scaled-up, reliable, and cost-effective manufacturing of nanoscale materials, structures, devices, and systems. Nanomanufacturing methods can be classified into top-down and bottom-up approaches, including additive, subtractive, and replication/mass conservation processes. These include a cluster of various techniques such as nanomachining, nanofabrication, and nanometrology to produce nanotechnology components and conduct evaluation. This paper mainly focuses on the manufacturing methods for complex shapes or structures, such as textures on curves and hierarchical structures, and outlines the research perspectives and the current application status of nanomanufacturing fundamentals and key technologies.
The recently published standard ISO 25178-2 distinguishes between field parameters and feature parameters for surface texture characterisation, whereby the main difference between these two types is due to the fact that the parameters belonging to the first group are deduced from all points of a scale limited surface, while the parameters belonging to the second group are deduced from only a subset of predefined topological surface features. As specified in ISO 25178-2, two prerequisites are indispensable for the determination of the feature parameters, viz., an adequate data structure for surface characterisation and a suitable formal method for surface generalisation, i.e. for the successive elimination of the less important surface features. Within ISO 25178-2 change trees are proposed for describing the surface topography, while Wolf pruning is suggested for surface simplification (cf. also ISO 16610-85). Apart from the techniques specified in ISO 25178-2 and ISO 16610-85, the present paper describes a second geometrical-topological approach for the characterisation and generalisation of surfaces that has its origin within the geosciences and is based on weighted surface networks and w-contractions. In addition, it is revealed how the two approaches, both of which have their foundations in graph theory, are interrelated to each other and how, from a historical point of view, the GIScience approach forms the basis of the one applied within surface metrology. Finally, some applications within precision engineering are described.
The growth defects in magnetron sputtered coatings have been well studied in industrial environment. In this work, on the other hand, the emphasis is in observing the same phenomena in a lab-scale UHV environment. TiN and CrN films were deposited at a thickness of 1–2 μm. The statistical evaluation of defect density was based on stylus profilometry scans (2 mm² area), and consequent analysis of hillock density in dependence of threshold height. Morphology of defects was observed by SEM, while on selected defects we made FIB cross-sections. In this way we were able to measure the chemical composition of individual seeds – starting points for growth defects. In contrast to expectations, there was only a relatively minor reduction of defect density by using UHV environment.
Mastering the additive laser manufacturing surface is a real challenge and would allow functional
surfaces to be obtained without finishing. Direct Metal Deposition (DMD) surfaces are composed by
directional and chaotic textures that are directly linked to the process principles. The aim of this work
is to obtain surface topographies by mastering the operating process parameters. Based on
experimental investigation, the influence of operating parameters on the surface finish has been
modeled. Topography parameters and multi-scale analysis have been used in order to characterize the
DMDobtained surfaces. This study also proposes a methodology to characterizeDMDchaotic texture
through topography filtering and 3D image treatment. In parallel, a new parameter is proposed:
density of particles (Dp). Finally, this study proposes a regression modeling between process
parameters and density of particles parameter.
Press molding of silicon (Si)/high-density polyethylene (HDPE) composite is an important technology for producing thin hybrid infrared (IR) optics with microstructures. In this research, Si-HDPE hybrid micro-lens arrays were press molded under various conditions, and the form accuracy and surface integrity of the molded lenses were evaluated. Air trapping occurs inside the micro-lens cavities during molding in a non-vacuum environment, which leads to severe surface defects. To investigate the air trapping phenomenon, a new in-situ observation system was developed which enables real-time direct observation of the molding process. From the in-situ observations, it was found that air traps were formed among the HDPE pellets during melting, and an increase in the pressing force will increase the pressure of the trapped air, forming trenches on the lens surface. The trapped air also impacts the mold coating, causing trench formation on the coating surface. To minimize air trapping, the molding temperature, and pressing force must be strictly controlled. By performing press molding in a vacuum environment, trench formation was completely eliminated. Moreover, polymer shrinkage compensation was performed to improve the lens form accuracy.
Researchers in the fields of computer graphics and geographical information systems (GISs) have extensively studied the methods of extracting terrain features such as peaks, pits, passes, ridges, and ravines from discrete elevation data. The existing techniques, however, do not guarantee the topological integrity of the extracted features because of their heuristic operations, which results in spurious features. Furthermore, there have been no algorithms for constructing topological graphs such as the surface network and the Reeb graph from the extracted peaks, pits, and passes. This paper presents new algorithms for extracting features and constructing the topological graphs using the features. Our algorithms enable us to extract correct terrain features; i.e., our method extracts the critical points that satisfy the Euler formula, which represents the topological invariant of smooth surfaces. This paper also provides an algorithm that converts the surface network to the Reeb graph for representing contour changes with respect to the height. The discrete elevation data used in this paper is a set of sample points on a terrain surface. Examples are presented to show that the algorithms also appeal to our visual cognition.
The tribological behavior of tenfold micro/nanocrystalline CVD diamond multilayers is here investigated in self-mated configuration using ball-on-plate reciprocating wear testing. The effects of relative humidity (RH) and temperature (T) on friction and wear coefficients are assessed. The strongest effect of humidity was found on the value of the critical load (no delamination) that triples from 40 N at 10%RH to 120 N at 90%RH. Evaluation of the wear coefficients of the plates was only possible with the use of 3D optical profilometry. A valley-shaped evolution is observed for the wear coefficient of the plates, within the 10% to 90% RH range, with a minimum of about 1.7x10⁻⁷ mm³N⁻¹.m⁻¹, indicative of a mild wear regime, whereas the balls have lower values in the very mild wear regime of k ~ 10⁻⁸ mm³N⁻¹.m⁻¹. The clearest difference between the RH and temperature experiments is observed for the critical loads, limited to the range 40-55 N at 50-100°C, while at room temperature a value of 120 N was reached. However, the critical loads at high temperature are similar to those attained under dry conditions (≤25% RH) highlighting the absence of water as the load bearing medium.
This keynote paper addresses the manufacturing of high-precision components with micro-scale features, and the associated process chain considerations. Three workpiece classifications as well as a micro-production process chain (MPPC) model are defined. A review of capabilities and advances in micro-manufacturing technologies, metrology, and equipment demonstrates increased versatility across varied applications, while also highlighting limitations. Challenges in the development of process chains are presented using results of the MPPC program of the Collaborative Working Group on Micro-Production Engineering. Finally, a guide for machining high-precision components with micro-scale features in process chains is given with respect to machine tools, tools, technology and environmental conditions.
A comprehensive analysis of literature pertaining to surface texture metrology for metal additive manufacturing has been performed. This review paper structures the results of this analysis into sections that address specific areas of interest: industrial domain, additive manufacturing processes and materials; types of surface investigated; surface measurement technology and surface texture characterisation. Each section reports on how frequently specific techniques, processes or materials have been utilised and discusses how and why they are employed. Based on these results, possible optimisation of methods and reporting is suggested and the areas that may have significant potential for future research are highlighted.