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Machining of Molds with Filigree Structures for Sheet-Bulk Metal Forming
Abstract
In this article investigations on micromilling of hardened tool steels as well as developments for an efficient process design are presented. In the course of this, suitable parameter ranges as well as process instructions are given, with which stable micromilling processes of hardened tool steels can be achieved. Besides the analysis of the milling process, a developed simulation technique is presented, which can be used to design and optimize the machining process. For further optimization, the cutting edge preparation of micromilling tools by wet abrasive jet machining and millpolishing and its influence on the manufacturing results are discussed. The production and application of functional surface structures in forming processes is additionally examined. Approaches and developed software are presented, with which machining programs for large-area structures as well as free-formed component surfaces can be generated with minimal effort within the CAD/CAM environment. Besides the derived process chain and tools for an efficient generation of machining programs, the performance and wear behavior of the surface structures is considered.
... Within the broad variety of mechanical manufacturing processes, a promising approach for the machining of heat-treated tool steels for Sheet-Bulk Metal Forming with a hardness of H > 60 HRC is micromilling [29]. First results presented by Twardy and Krebs prove the feasibility and benefits of the manufacturing technology for different tool steels with respect to a low roughness profile [30,31]. ...
... First results presented by Twardy and Krebs prove the feasibility and benefits of the manufacturing technology for different tool steels with respect to a low roughness profile [30,31]. Further investigations were summarized in the contribution by Meijer and Biermann, in which suitable parameters were derived on the basis of the process forces determined as well as the wear behavior of the cutting tools [29]. Despite the demanding machining of heat-treated tool steels, stable manufacturing processes with the excellent surface qualities could be derived. ...
... The face circumferential milling strategies as well as further specifications of the used tools for the hard milling operations are illustrated in Figure 1. The processing parameters are based on previous studies [29,31]. Both processes were performed with a width of cut of 10 % of the tool's diameter, resulting in an a e = 0.1 mm for the micromilling (MM) process and an a e = 0.4 mm for the mesomilling (M) strategy. ...
New manufacturing technologies, such as Sheet-Bulk Metal Forming, are facing the challenges of highly stressed tool surfaces which are limiting their service life. For this reason, the load-adapted design of surfaces and the subsurface region as well as the application of wear-resistant coatings for forming dies and molds made of high-speed steel has been subject to many research activities. Existing approaches in the form of grinding and conventional milling processes do not achieve the surface quality desired for the forming operations and therefore often require manual polishing strategies afterward. This might lead to an unfavorable constitution for subsequent PVD coating processes causing delamination effects or poor adhesion of the wear-resistant coatings. To overcome these restrictions, meso- and micromilling are presented as promising approaches to polishing strategies with varying grain sizes. The processed topographies are correlated with the tribological properties determined in an adapted ring compression test using the deep drawing steel DC04. Additionally, the influence of the roughness profile as well as the induced residual stresses in the subsurface region are examined with respect to their influence on the adhesion of a wear-resistant CrAlN PVD coating. The results prove the benefits of micromilling in terms of a reduced friction factor in the load spectrum of Sheet-Bulk Metal Forming as well as an improved coating adhesion in comparison to metallographic finishing strategies, which can be correlated to the processed roughness profile and induced compressive residual stresses in the subsurface region.
... This is followed by a post-processing step in form of a pressurized air wet abrasive jet machining process and an application of CrAlN physical vapour deposition (PVD) coating for wear reduction. This combined surface treatment is lead researched by Maijer et al. and Stangier et al. [194]- [198] who contributed to the following investigations. ...
The technological environment of industrial production processes faces constant challenges and is subject to continuous change. Requirements regarding resource and emission savings as well as lightweight construction, functionalization and individualization are key drivers of technical innovations. In particular, increasing automation, process monitoring and fast component inspection are of growing importance, which requires novel and innovative measurement approaches and instruments. In this thesis, a flexible, fiber-optic 3D endoscope based on fringe projection profilometry is presented for in-situ wear monitoring in operating forming processes. Due to specific measuring applications, different measuring head designs and positioning configurations are required. Flexible positioning necessitates strategies for registration of the reconstructed surface data in a fixed world coordinate system, which is investigated in the context of different approaches. Furthermore, algorithms and methods for adaptive data masking and improved data fusion are developed and presented, allowing for low-noise and accurate surface reconstruction while maintaining as many object points as possible. Complementary, methods for the reduction of inaccurate deviation values are developed to enable a high sensitivity and conclusiveness of the inspection. Furthermore, approaches for fast point cloud classification by adapted search trees and estimation methods are presented. Finally, the sensor is evaluated on the basis of existing standards and further developed approaches, and the influence of various environmental factors is investigated and quantified in various experiments.
The technology advancement has envisaged going for near net shape of the produces. Also, near net shapes formed are again cold upset for obtaining a final shape of the Product. This work deals with an experimental, theoretical and analytical determination of friction factor 'm' for Solid aluminium Cylinders under different lubricating conditions. The aluminium ring having a standard ratio specified by the Male and Cockcroft (6:3:2) with a dimension of Outer diameter: inner diameter: Height, 42:21:14 is prepared to carry the ring compression test, to determine the friction factor between the interface of the work piece and die. Different lubrication conditions are applied such as zinc stearate, molybdenum disulphide, graphite powder and in dry condition. The friction factor is sensitive to contact between the specimens and die. When the lubricant applied, the aluminium ring dimensions are change. The change in dimension, outer diameter, internal diameter, and reduction in height, using the standard calibration curve available for friction conditions by Male and Cockcroft is used to determine the friction factor of material. Aluminium specimen is applied by the load. Deformations take place, the dimensions of specimen changes. Substituting the initial undeformed geometries and the changes in the dimensions in following equations Give the value of the friction factor.[Ettouney and stelson, 1990: Male and depierre, 1970: avitzur, 1986] the friction factor is determined. When the lubricants are applied on aluminium ring under ring compression test. The load applied to the ring during ring compression test is insensitive to friction condition.
The high quality demand for machined functional surfaces of forming tools, entail extensive investigations for the adjustment of the manufacturing process. Since the surface quality depends on a multitude of influencing factors in face micromilling, a complex optimization problem arises. Through analytical and simulative approaches, the scope of the experimental investigation to meet the requirements for surface roughness can be significantly reduced. In this contribution, both analytical and simulation-based approaches are presented in the context of predicting the roughness of a machined surface. The consideration of actual tool geometry and shape deviations are used in a simulation system to achieve the agreement with experimental results.
In a production of filigree and complex geometries, different NC-controlled processes such as laser cutting, EDM milling, and micromachining require a constant feed rate to ensure high-quality manufacturing results. Due to the technically limited acceleration ability of the machine tool axes, the nominal feed cannot always be achieved. This in particular is the case when the machine tool has to perform a significant change of direction in corners. In this paper, the impact of too low feed rates on the process of precise micromilling of a hardened high-speed steel AISI (M3:2) 63 ± 1 HRC) is discussed. An unattained feed rate leads to a ploughing dominated process with a high burr formation resulting in a huge potential loss of micromilling processes. Furthermore, a simulation approach is presented which allows the prediction of the actually achieved feed rate. The developed machine model provides a reliable method to identify critical areas in the entire NC program.
Current demands for flexible, individual microstructures in high quality result in high requirements for micro tools. As the tool size defines the minimum structure size, ultra-small tools are needed. To achieve tool diameters of 50 μm and lower, we investigate the complete manufacturing chain of micro machining. From the development of the machine tools and components needed to produce and apply the micro tools, the micro tools themselves, as well as the micro machining processes. Machine tools are developed with the possibility of producing the micro geometry (cutting edge design) of micro tools as well as plating processes to produce super abrasive micro grinding tools. Applying these setups, we are able to produce ultra-small micro grinding and micro milling tools with typical diameters of 50 μm and down to 4 μm. However, the application of such tools is very challenging. The article presents possibilities and limitations in manufacturing the micro tools themselves as well as microstructures made with these tools. A special emphasis will be on the influence of the tool substrate in micro milling and grain sizes in micro grinding.
The precise micromanufacturing of complex dies with small structures for sheet-bulk metal forming is a challenge due to the high hardness of the materials to be machined. Experiments have shown that micromilling of these difficult-to-machine materials is possible despite of their high hardness. Nevertheless, the higher wear of the tools plays a decisive role. When implementing the machining task as five-axis process, it is possible to control the wear distribution by tilting the milling tools. In this paper, a simulation system is presented which determines the loads acting on the cut- ting edge with regard to different criteria, e.g., the machined material or the effective impulse. Based on this knowledge, it is possible to design the milling process to minimize the tool wear and thereby to increase the lifetime of the milling tools. In order to show the applicability of the simulation system, test workpieces were machined and the experimental results are compared to the simulation data.
In case of manufacturing miniaturized products with 3D features, micromachining is a suitable technology. By using a five-axis process, it is possible to produce complex products with high material removal rates. Further benefits are, for example, higher tool stiffness due to the possibility of utilizing tools with shorter cantilever lengths and higher surface qualities, which can be achieved by avoiding cutting with the center of the tool when using ball-end milling cutters. A tool inclination can not only be used to avoid the center cut in the five-axis process, but also to achieve better cutting conditions. In this paper, the influence of the tool inclination is analyzed for micromilling hardened high-speed steel (S6-5-2, 63 HRC). The presented results show the possibility of reducing tool wear and achieving better surface qualities by applying a specific tool inclination. This knowledge can be used to generate optimized NC programs for the five-axis micromilling of hardened steels.
Micro-Cutting: Fundamentals and Applications comprehensively covers the state of the art research and engineering practice in micro/nano cutting: an area which is becoming increasingly important, especially in modern micro-manufacturing, ultraprecision manufacturing and high value manufacturing.
This book provides basic theory, design and analysis of micro-toolings and machines, modelling methods and techniques, and integrated approaches for micro-cutting. The fundamental characteristics, modelling, simulation and optimization of micro/nano cutting processes are emphasized with particular reference to the predictabilty, producibility, repeatability and productivity of manufacturing at micro and nano scales.
The fundamentals of micro/nano cutting are applied to a variety of machining processes including diamond turning, micromilling, micro/nano grinding/polishing, ultraprecision machining, and the design and implementation of micro/nano cutting process chains and micromachining systems.
Key features
• Contains contributions from leading global experts
• Covers the fundamental theory of micro-cutting
• Presents applications in a variety of machining processes
• Includes examples of how to implement and apply micro-cutting for precision and micro-manufacturing
Micro-Cutting: Fundamentals and Applications is an ideal reference for manufacturing engineers, production supervisors, tooling engineers, planning and application engineers, as well as machine tool designers. It is also a suitable textbook for postgraduate students in the areas of micro-manufacturing, micro-engineering and advanced manufacturing methods.
Forming tools with tailored surfaces or functional surface modifications offer great potential for the adaption and optimization of forming processes. However, the interaction of the resulting tribological conditions with additional process oscillations and lubricants has not yet been sufficiently investigated. In the field of sheet-bulk metal forming the superimposition of oscillations is a new, highly promising approach for optimizing the forming of metallic materials. The aim of this study is therefore to investigate the forming behavior of metallic materials with an oscillation superimposition in combination with structured tool surfaces. In order to examine to what extend the friction factor and the forming force can be influenced by structured surfaces and PVD-coatings ring compression tests were conducted to re-create the real process conditions. The experiments were carried out statically and with an oscillation superimposition in the main force flow of the machine under lubrication and dry conditions. Occurring interactions between surface applications, lubrication and oscillation superimposition are identified and analyzed within the context of this work. Thereby, three different deterministic surface structures of the ring compression tools were considered. A radial and tangential arrangement of a wave-like structure as well as an isotropic honeycomb structure were applied on the forming tools by means of micromilling. For a lubricated and vibration superimposed process, especially the isotropic honeycomb structure caused a significant decrease in friction. This was attributed to the formation of lubrication pockets. Despite the reduced friction, in some cases no reduction of the forming force occurred by using an oscillation superimposed forming process. This behavior was attributed to damping effects caused by the lubricating pockets.
The increasing demand for closely tolerated and highly integrated functional components motivates the development of the innovative process class sheet-bulk metal forming (SBMF). SBMF is defined as the application of bulk forming operations on sheet metal to produce parts with integrated functional elements. Due to varying tribological loads, caused by the local forming of functional elements and the resulting complex material flow, the geometrical accuracy of the produced parts can be limited. A local increase or decrease of friction by modified surfaces also called tailored surfaces which control the material flow are an approach to improve the geometrical accuracy of the part. These tailored surfaces should be applied tool-sided to guarantee a short process chain. Consequently, the aim of this study is to analyze the potential of modified tool surfaces for a usage as tailored surfaces in SBMF processes. The tribological behavior of tailored tool surfaces is investigated to provide a basis for the selection of tailored surfaces. Different grinding and blasting strategies, as well as lubrication pockets are chosen as surface modifications and applied on the tool steel 1.3344 with a hardness of 61 ± 2 HRC. Lapped tools are chosen as a reference for the modified surfaces, since lapping is a widespread finishing process for forming tools. First of all, the topographies of the modified surfaces are characterized using optical and tactile measurements. Afterwards the tribological behavior of the surfaces is investigated using a modified ring compression test with specimens made of 1.0338. The resulting friction factors are correlated with the topography characteristics of the tailored surfaces to identify functional interrelations. Finally, the tailored surfaces are evaluated regarding their eligibility to adapt the friction and control the material flow in SBMF-processes.
The cutting edge preparation is a common process in the production chain of cemented carbide macro tools. It is used to reduce failures resulting from grinding and to generate a specific cutting edge geometry that is appropriate for the application of the cutting tool. The adhesion of a subsequently applied coating is also increased due to the rounded and more regular shape of a prepared cutting edge. Even though cutting edge preparation is able to significantly increase the life of macro tools, it is not state of the art in the production of micro tools since common preparation processes have not been developed and established for this case of application. Within the investigations, the feasibility of the wet abrasive jet machining process for the preparation of micromilling tools is analysed. For this purpose, the preparation process is refined which allows an effective reduction of the defects and a successful adjustment of different rounding sizes of the cutting edge in a relatively short preparation time. In addition, a high-quality statistical model is achieved to describe the interdependency of the process parameters. In conclusion, TiAlN layers are applied on the rounded cutting edges by a PVD-process without obstructive droplets.
Tool texturing is studied as a method to enhance lubrication and prevent the occurrence of galling. Strip reduction test tools manufactured with longitudinal, shallow pocket geometries oriented perpendicular to the sliding direction are tested. The pockets have small angles to the workpiece surface and varying distance. The experiments show an optimum distance between the pockets to exist that creates table mountain topography with flat plateaus and narrow pockets in between. If the flat plateaus are too narrow, an increase in drawing load and pick-up on the tool plateaus is observed. The same occurs for too wide plateaus. A theoretical friction model supports the experimental findings of an optimum distance between the pockets, where the contribution to friction by mechanical interlocking of the strip in the pockets is limited and lubrication of the plateaus is enhanced by micro-plasto-hydrodynamic lubrication.
Incremental Sheet-Bulk Metal Forming offers an innovative and flexible approach for the manufacturing of gears. An insufficient formfilling of the generated gearing, especially of the first tooth formed, is observed. Aiming for a formfilling improvement of the first tooth element, three influencing factors were investigated. First, the prevailing friction is analyzed and a possibility for its adjustment is offered by a tailored adaption of the tool surface topographies. These were manufactured by micromilling, EDM and polishing processes and partially covered by CrAlN PVD-coatings. Based on ring-compression tests, which were performed to determine the resulting friction conditions, the analyzed topographies were transferred onto real tool surfaces and used in the incremental gear forming process. Second, the influence on the formfilling of the blank cutting process and the resulting sheet edge properties were investigated. The third aspect to enhance the formfilling of the gear elements was the modification of the process strategy of the incremental forming process. Due to different conditions for the initial and the following indentations, a preforming operation was investigated in order to realize a similar material flow for all indentations. With the combination of the best parameters regarding the tool surface, the blank cutting process and the forming strategy, an improvement of the formfilling of the first formed gear element by up to 33% and for the following gears by up to 13% was achieved.
Bionic surface structures, inspired by the flora, were developed for Sheet-Bulk Metal Forming (SBMF) in order to locally control the friction condition by adjusting the wetting behavior. Five bionic structures were micromilled on ASP®2023 in annealed as well as hardened and tempered conditions. Subsequently, the structured surfaces were plasma-nitrided and coated with a CrAlN thin film. The influence of the treatment method on the structural geometry was investigated with the aid of a scanning electron microscope and 3D-profilometer. The wetting behaviors of water and deep drawing oil (Berufluid ST6007) on bionic surfaces were evaluated using contact angle measurements. The resulting micro-milled structures exhibit an almost identical shape as their bionic models. However, the roughness of the structured surfaces is influenced by the microstructure. The combination of plasma-nitriding and Physical Vapor Deposition (PVD) leads to an increase in roughness. All bionic structures possess higher contact angles than that of the unstructured surfaces when wetted by water. This can be explained by the fact that the structural elevations block the spreading. When the bionic surfaces are wetted by deep drawing oil, the lubricant spreads in the structural cavities, leading to smaller contact angles. Furthermore, the anisotropy of the structure has an influence on the wetting behavior.
Sheet-bulk metal forming (SBMF) is characterized by successive and/or simultaneous occurrence of quite different load conditions regarding stress and strain states. These conditions significantly influence the material flow and thus the geometrical accuracy of the components. To improve the product quality a control of the material flow is required. An appropriate approach is given by locally adapted tribological conditions due to surface modifications of tool and workpiece, so-called tailored surfaces. Within the present study different methods to adapt the surfaces are presented and investigated with respect to their tribological effectiveness in SBMF. In a first step, requirements regarding necessary adaptions of the friction values for two SBMF processes are numerically defined. Based on the requirements different tailored surfaces are presented and analyzed regarding their tribological influence. Finally, the potential of surface modifications to improve SBMF processes is shown.
The mechanical wear behavior of forming tools is the limiting factor during an incremental gear-forming process. These forming tools with a simply shaped geometry are exposed to high forming forces. Additionally, the necessary workpiece chambering, which is characteristic for this incremental process restricts the dimensioning of the tools. Thereby, the geometrical design of the forming tools is limited, which leads to a decreased lifetime. Functional structures on the tool surfaces can influence the occurring loading and wear behavior by reducing the contact area, the supply of lubricant pockets, and by a controlled influence and adjustment of the occurring material flow. For the extension of the tool's lifetime, different surface concepts and combinations with CrAlN PVD-coatings are investigated. To offer conditions with a high tool load, the investigations are focused on an incremental gear forming process with a simple one-wedge forming tool.
Sheet-Bulk Metal Forming (SBMF) allows the manufacture of complex parts with integrated functional form elements, such as teeth and thickened areas. Therefore, bulk forming operations are applied to sheets with initial thicknesses of 2 or 3 mm. The design and functionality of the tools are as important as the process itself. Therefore, the working group “Tools” of the Transregional Collaborative Research Centre on Sheet-Bulk Metal Forming (CRC/TR73) focuses on the optimization of the technical tool design. By varying topographies or applying tailored coatings, the friction behavior is changed to achieve a better form filling and to reduce process forces during the forming operations. In this paper, the potential of different tailored surfaces is validated by simulations and experimental studies. The tribological behavior of 14 surface microstructures is evaluated using a half-space model in order to select structures suitable for application. Those were characterized experimentally by ring-compression and pin-extrusion tests. The determined friction factors were used in a forming simulation to predict the form filling of small cavities in a flow forming operation. Furthermore, special attention is paid to the utilization of the anisotropic behavior of specific structures. The results were validated by an incremental gear forming process.
Ein etabliertes Konzept zur Anpassung der tribologischen Eigenschaften sowie zur Steigerung der Verschleißbeständigkeit stellen Beschichtungen dar. Zusätzlich zur werkstoffseitigen Adaption der Oberflächen gibt es Bestrebungen, Strukturen auf funktionalen Werkzeugflächen zu applizieren, um eine weitere Anpassung des Eigenschaftsprofils zu ermöglichen. Aus diesem Grund wird im vorliegenden Beitrag der Einfluss bionisch und technologisch texturierter Flächen auf das Reib- und Verschleißverhalten mit und ohne endkonturnaher PVD-Verschleißschutzschichten untersucht. Nach dem Vorbild der Natur wurde die auf dem Kopf von Skarabäus-Käfern identifizierte wabenförmige Oberflächenstruktur sowie eine auf die Fertigungszeit optimierte Dimpel-Struktur mittels Mikrozerspanung auf Proben aus HSS-Stahl übertragen. Im Fokus der Analysen liegen der Einfluss der Oberflächentexturen, die Auswirkungen der PVD-Schicht sowie die jeweiligen Wechselwirkungen auf das Reib- und Verschleißverhalten.
Surface modification by means of textured structures can largely enhance the tribological and wear behavior of components and tools under various environmental conditions. Continuous developments in machining processes , such as the micromilling technology, can be used to manufacture fine-scaled structures on hardened steel tool surfaces. Thus, the adjusted friction behavior, which can affect the tendency of a material to adhere to the surface, is compensated by the small number of contact points between the friction partner and the surface. Accordingly, anisotropic friction properties of such structures can lead to a locally different wear behavior. In this study, a NiCrBSiFe self-fluxing alloy is thermally sprayed onto specimens made of AISI M2 high-speed steel (HSS). Technological and bionic surface structures were applied on thermally sprayed and laser remelted sub-strates. Based on ball-on-disk tests, the coefficient of friction was determined and compared for different high velocity oxy fuel (HVOF) sprayed NiCrBSiFe coatings and surface textures. These experiments show that functional structures can reduce the coefficient of friction. The bio-inspired surface shows a friction reduction of approximately 35% compared to the as-sprayed and polished sample, and a reduction of 25% when compared to the remelted and smoothened surface. Moreover, the analyzed surface conditions lead to a different wear behavior than the bio-inspired structure, which possesses areas with a reduced oxidational wear and less adhesion when compared to the other surface conditions.
Sheet-bulk metal forming is a process used to manufacture load-adapted parts with high precision. However, bulk forming of sheet metals requires high forces, and thus tools applied for the operational demand have to withstand very high contact pressures, which lead to high wear and abrasion. The usage of conventional techniques like hardening and coating in order to reinforce the surface resistance are not sufficient enough in this case. In this paper, the tool resistance is improved by applying filigree bionic structures, especially structures adapted from the Scarabaeus beetle to the tool’s surface. The structures are realized by micromilling. Despite the high hardness of the tool material, very precise patterns are machined successfully using commercially available ball-end milling cutters. The nature-adapted surface patterns are combined with techniques like plasma nitriding and PVD coating, leading to a multilayer coating system. The effect of process parameters on the resistance of the tools is analyzed experimentally and compared to a conventional, unstructured, uncoated, only plasma nitrided forming tool. Therefore, the tools are used for an incremental bulk forming process on 2 mm thick metal sheets made of aluminum. The results show that the developed methodology is feasible to reduce the process forces and to improve the durability of the tools.
A novel principle of a rotary piston valve and a high-frequency cylinder for a hydraulic actuation system are presented. This system will be utilized in metal-forming presses to superimpose a high-frequency oscillation on the movement of the ram. This technique was proven to enhance the forming parts quality, to extend the process limits and to reduce the forming force significantly. The key components of the valve are a stator and a rotary piston with radial drilled holes that is designed to provide a pulsating pressure and mass flow rate at a high frequency. A hydraulic cylinder is connected to the valve and converts the pulsating flow into a dynamic process force. The valve and the cylinder will be mounted on the bolster plate of a metal-forming press. In order to superimpose oscillation in the main forming direction, the cylinder is centered under the punch of the metal-forming tool. Three-dimensional computational fluid dynamics (CFD) simulations have been conducted to evaluate and to optimize the designs of the main components of the system. Hereby the commercial simulation code of ANSYS CFX was employed to determine the properties of the cylinder and the valve. Through its mesh motion technique, this simulation code allows the flow analysis between the rotary and the stationary part of the valve. Furthermore the dynamic characteristics of the system have been investigated under the influence of inertia and the compressibility of oil.
This paper compares the size effect behaviour in micro- and macromilling by applying Analysis of Variance on the specific cutting force (kc) and relating it with the tool edge radius (re), workpiece roughness (Ra), cutting force and chip formation when cutting slots in AISI 1045 steel. Size effect is observed in micromilling through hyper-proportional increase of the specific cutting force for feeds per tooth (f) lower than endmill edge radius, reaching levels of grinding process (∼70 GPa) when f≅re/10. This particular milling condition does not produce chips. The minimum uncut chip thickness (hmin) varied between 22% and 36% of the endmill edge radius. This range was determined by proposing a curve (kc/Raversus f/re) where specific cutting force becomes amplified (size effect) due to workpiece roughness association. In addition to the minimum uncut chip thickness, there is a cutting thickness between hmin and re that optimizes workpiece surface integrity and not only forms the chip completely. This thickness may be as important as hmin. Besides this, a relation between deformation mechanisms during chip formation and cutting force oscillations is proposed for micromilling and also related to tool tip radius (rε). This cutting force behaviour enables the determination of certain characteristic chip thicknesses including hmin. Finally, it is concluded that minimum uncut chip thickness varies practically from 1/4 to 1/3 of tool cutting edge, regardless of workpiece material, tool geometry, mechanical machining process and technique used for measuring or estimating hmin, i.e. numerical, analytical or experimental.
Tool life and performance are decisively determined by cutting edge geometry. An appropriate shape of the cutting edge improves wear resistance, tool life and process reliability. This paper reviews major developments in cutting edge preparation technologies and methods of cutting edge characterization. Moreover, the influences of cutting edge geometry on chip formation, material flow, as well as mechanical and thermal loads on the tool are discussed. The essential modeling and simulation approaches are presented. Effects on surface integrity are described. Finally, an overview of important perceptions for prospective research and development in this field is provided.
The design of the cutting tool microgeometry influences the thermo-mechanical load profile on the wedge. Applying the appropriate hone design stabilizes the cutting edge, leads to improved wear behavior and higher tool life. Higher process forces and temperature, induced by larger hone, can be described as a side effect of cutting edge preparation, which should also be observed. This paper presents the quality oriented cutting edge preparation via abrasive brushing. The influence of the hone design on process forces, wear behavior and tool life of coated inserts will be analyzed within a wide range of cutting edge microgeometries and process parameters.
Micro milling operations can fabricate miniaturized components with high relative accuracy. Since micro machining operations are different than conventional macro machining processes, due to the large negative rake angle and elasto-plastic effects, it is important that the modeling of micro end milling forces incorporates the dynamics of the tool, ploughing and elastic recovery. This study examines the mechanistic modeling of shearing and ploughing domain cutting regimes to accurately predict micro milling forces. The tool dynamics are indirectly identified by performing receptance coupling analysis. Furthermore, the Kalman filter compensation method is used to precisely measure the forces to obtain the cutting constants.
By means of experiments it could determined that micro-machining processes as grinding, drilling and milling are a good addition
to the established production technologies in micro technology. To machine hard and brittle materials grinding with diamond
tools is well suitable, but the kinematics of the grinding process, as well as the process strategy has a significant influence
on the machined surface quality and the chipping of the edges. The study of micro-machining processes showed, that micro cutting
processes are not just a miniaturisation of the conventional cutting technology. The reduced tool stiffness of micro drills
caused by the changes of geometry requires an adjustment of the complete drilling processes. Sharp cutting edges are an essential
requirement for the fabrication of very small structures. So, using single edged micro milling cutters made of diamond significant
smaller structures could be made compared to using conventional milling cutters made of tungsten carbide. Furthermore, acoustic
emission sensors proved to be suitable for detecting the tool position after a change of the tool with a high accuracy.
This paper investigates the feasibility of increasing the wear resistance of cemented carbide tools through micro-blasting of their PVD-coatings. The enhanced and graded film strength properties before and after micro-blasting are determined by means of a FEM-based evaluation of nanoindentation results. The coating topomorphy, induced by micro-blasting, was monitored and correlated to the substrate roughness and film adhesion. The cutting performance of inserts, coated with micro-blasted films, was investigated in milling and explained with the aid of a cutting process FEM simulation. The obtained results reveal a tool life growth through micro-blasting of coatings, deposited on substrates with appropriate roughness characteristics.
In this work the electrical discharge machining (EDM) of AISI D2 tool steel was investigated. The surface characteristics and machining damage caused by EDM were studied in terms of machining parameters. Based on the experimental data, an empirical model of the tool steel was also proposed. A new damage variable was used to study the EDM damage. The workpiece surface and re-solidified layers were examined by a scanning electron microscopy. Surface roughness was determined with a surface profilometer. The residual stress acting on the EDM specimen was measured by the X-ray diffraction technique. Experimental results indicate that the thickness of the recast layer, and surface roughness are proportional to the power input. The EDM process introduces tensile residual stress on the machined surface. The EDM damage leads to strength degradation.
In manufacturing of metallic components, the size of the part plays an important role for the process behaviour. This is due to so called size effects, which lead to changes in the process behaviour even if the relationship between the main geometrical features is kept constant. The aim of this paper is to give a systematic review on such effects and their potential use or remedy. First, the typology of size effects will be explained, followed by a description of size effects on strength and tribology. The last three sections describe size effects on formability, forming processes and cutting processes.
Fertigen bionischer Strukturen in einem Mikrofräsprozess. wt - Werkstattstechnik online 101
- D Biermann
- E Krebs
Micromilling of bionic structures
- D Biermann
- E Krebs
- J Schlenker
Simulationsgestützte Mikrofräsbearbeitung gehärteter Werkzeugstähle zur Herstellung filigraner Formelemente und funktionaler Oberflächenstrukturen. Disseratation
- E Krebs
Neue Entwicklungen für den produktiven Einsatz von Hartmetallwerkzeugen in kleinsten Dimensionen
- D Biermann
- A Meijer
- E Krebs
- S Michel
- J Jaeger
Untersuchungen strukturierter Werkzeugflächen und der Einfluss auf den Werkzeugverschleiß
- B.-A Behrens
- D Biermann
- A Menzel
- W Tillmann
- R Krimm
- A Meijer
- M Schewe
- D Stangier
- O Commichau
- P Müller
- S Hübner
- D Rosenbusch
Weinert: Schneidkantengestalt bestimmt Einsatzverhalten, Einfluss der Kantenpräparationvon Zerspanungswerkzeugen
- D Biermann
- B Denkena
- J Haubrock
- L De Leon
- I Terwey
Drillpolishen als neuartiges Kantenpräparationsverfahren - Mit elastisch gebundenen Scheiben die Kante verrunden
- J Brodbeck
- S Rothenaicher
- D Biermann
- T Heymann
- M Wolf