Wim Dewulf

• KU Leuven

This work examines the impact of powder particle size distribution (PSD) on the surface finish of maraging 300 steel parts produced by laser powder bed fusion (LPBF). After an initial selection of two suitable powder raw materials, Mar 10–30 and Mar 15–45, the study demonstrates that finer powders lead to significantly smoother upfacing surfaces, w...

Motivated by industrial computed tomography, we propose a memory efficient strategy to estimate the regularization hyperparameter of a non-smooth variational model. The approach is based on a combination of FISTA and Condat-Vu algorithms exploiting the convergence rate of the former and the low per-iteration complexity of the latter. The estimation...

Fringe projection systems are well established as metrology tools for fast measurements of (large) workpieces. However, as specular surface reflectivity causes camera saturation, the accuracy of fringe projection for (semi-)reflective parts is limited. The use of polarization filters can reduce the effect of this specular reflectivity, but lowers t...

By detecting internal batteries before treatment, the end-of-life handling of Waste Electrical and Electronic Equipment (WEEE) can be made more safe and cost efficient. Where prior research has demonstrated the potential of deep learning models to detect batteries in X-ray transmission (XRT) images of WEEE, these studies did not fully investigate t...

X-ray Computed Tomography (XCT) is a validated and frequently used tool to verify part geometry and to perform a non-destructive inspection of additive manufacturing parts. However, the acquisition of a large number of X-ray projections generates long inspection times. This conflicts with a high throughput of the production process and hinders the...

This work is concerned with fan- and cone-beam computed tomography with circular source trajectory, where the reconstruction inverse problem requires an accurate knowledge of source, detector and rotational axis relative positions and orientations. We address this additional inverse problem as a preceding step of the reconstruction process directly...

This work is concerned with cone-beam computed tomography with circular source trajectory, where the reconstruction inverse problem requires an accurate knowledge of source, detector and rotational axis relative positions and orientations. We address this problem as a preceding step of the reconstruction process directly from the acquired projectio...

Laser powder bed fusion of metals offers important advantages for several industrial applications. Research work is needed to improve the production rates while reducing the likelihood of defects compromising part quality. It is feasible to improve production rates by fabricating parts with thicker layers, but this often leads to an increased prese...

Determining the roughness of additive manufacturing objects is widely acknowledged as a complex task. This paper therefore presents a practical application of discrete Legendre polynomials in extracting geometrical measurements from Laser sintered material using X-Ray Computed Tomography (XCT). X-Ray Computed Tomography (XCT) is first utilized to e...

In recent years, the non-destructive characterisation via X-ray computed tomography of internal features, often produced with novel manufacturing methods, has gained increasing attention. Reducing the rate of defects during the production of internal features is of particular interest since post-processing steps are highly cumbersome, or removal of...

Additive manufacturing (AM) offers opportunities to produce three dimensional complex geometries with a greater design freedom as compared to subtractive manufacturing. New weight-saving designs are enabled, making AM an appealing production method for the aerospace industry. However metal AM for aerospace applications is currently limited to non-s...

The time of an X-ray Computed Tomography (XCT) measurement is directly affected by the number of acquired X-ray projections. In general, a large number of X-ray projections, hence a large acquisition time is required to obtain a qualitative reconstruction and successive feature analysis. To expand the applicability of XCT towards low-end parts we p...

The few-view image reconstruction problem is one of the challenging research areas in industrial Computed Tomography (CT). On the one hand, acquiring enough data for reconstruction leads to a longer scanning time, which may not be applicable in industrial CT. On the other hand, reconstructing under-sampled data leads to artifacts and inaccurate ima...

Laser powder bed fusion (LPBF) currently faces challenges in consistency, complexity, and cost associated with quality ensurance. In-situ process monitoring is a potential approach to this problem. This work investigates the feasibility of using photodiodes for quality monitoring and correlates photodiode signals with X-ray computed tomography (X-C...

The framework of the Geometrical Product Specification defines the nominal geometry of the components and the characteristic tolerances. Various ISO standards describe the nine defined geometrical properties per characteristic of a workpiece. To prove conformance to the task specific tolerances according ISO 14253–1, the uncertainty budget needs to...

This study proposes an algorithm to autonomously generate the scan path for a laser line scanner mounted on a coordinate measuring machine. The scan path is determined based on task-specific measurement uncertainty in order to prove conformance to specified tolerances. The novelty of the algorithm is the integration of measurement uncertainty. This...

Computed Tomography (CT) as a dimensional metrology tool allows test parts to be fully characterized regardless of whether their features are accessible from the outside or hidden from sight. CT, however, has a complex measurement chain and the measurement accuracy can be strongly affected by metrologist-selected scan parameters. To develop a broad...

X-ray computed tomography (XCT) is increasingly used for quality control and non-destructive inspection in the manufacturing industry. Compared to conventional XCT machines, twin robot CT systems are a promising platform for the scanning of oversized workpieces without disassembling them. This work proposes a reference-free geometry estimation meth...

CT as a measurement technology for quality control has demonstrated unprecedented potential to retrieve comprehensive dimensional information on lightweight parts with complex shapes, including geometries inaccessible to conventional sensors, therefore addressing the current needs of industrial metrology, such as the inspection of objects stemming...

Waste Electric and Electronic Equipment (WEEE) is a prominent and increasing waste stream for which the Commission of the European Union has put in place ambitious recycling targets. However, these targets can only be achieved by ensuring that both industry and governments develop adequate infrastructure and policies for recycling plastics in an ec...

While deep learning has helped improve the performance of classification, object detection, and segmentation in recycling, its potential for mass prediction has not yet been explored. Therefore, this study proposes a system for mass prediction with and without feature extraction and selection, including principal component analysis (PCA). These fea...

X-ray computed tomography (XCT) is increasingly being used for evaluating quality and conformance of complex products, including assemblies and additively manufactured parts. The metrological performance and traceability of XCT nevertheless remains an important research area that is reviewed in this paper. The error sources influencing XCT measurem...

In this study, a procedure to automatically identify the product model by evaluating an image of the label is presented. First, object character recognition (OCR) extracts text from the product label. Second, to identify the product model, the extracted text is compared with unique model references in a database, giving access to other model‐specif...

The expected surge in demand for lithium-ion batteries (LIBs) has influenced the supply chain of several raw materials and increased their market prices significantly. In recent years, rechargeable battery development projects have started addressing the topic of resource availability and their prices. As a result, metrics for assessing resource cr...

Today, the sorting of battery packs and pouch cells from waste electrical and electronic equipment (WEEE) is performed manually as the batteries vary in shape and weight. Therefore, the feasibility to classify waste batteries by first recognizing text on an image of the battery with deep learning object character recognition (OCR), and then compari...

Laser sintering is evolving towards a genuine manufacturing technique for volume production and mass customized products. However, variability in part quality has to be reduced further to enable its use for high demanding and critical end-use applications. High volume and mass customized manufacturing impose the need for a fast and flexible measure...

X-ray Computed Tomography (xCT) is a very effective way of detecting and characterizing the internal information of objects. However, blur is frequent in high-energy industrial xCT (ixCT), degrading image quality and spatial resolution. Therefore, this paper explores the application of L0 regularization to image deblurring in ixCT. With sparsity in...

Digital twins of measurement systems are used to estimate their measurement uncertainty. In the past, virtual coordinate measuring machines have been extensively researched. Research on digital twins of optical systems is still lacking due to the high number of error contributors. A method to describe a digital twin of an optical measurement system...

This contribution reports on exploratory research to streamline the Probability of Detection (PoD) calculation for defect analysis with industrial X-ray Computed Tomography (XCT). Reliable, reproducible and universally applicable PoD information is becoming relevant for all non-destructive testing (NDT) methods, like XCT, where many acquisition par...

In consequence of the electrification and the increased adoption of lightweight structures in the automotive industry, global demand for wrought Aluminum (Al) is expected to rise while demand for cast Al will stagnate. Since cast alloys can only be converted to wrought alloys by energy-intensive processes, the most promising strategy to avoid the e...

We present a concept for propagating uncertainty in x-ray computed tomography (CT) using a Monte Carlo reconstruction (MCR) technique, comprising repeated reconstructions with varying input parameters. The proposed technique follows the framework for model-based x-ray CT uncertainty assessment per the Monte Carlo method (JCGM 101), although it prov...

Digital manufacturing is one of the key drivers associated with the idea of flexible mass customization, which has been boosted in recent years by the substantial advances in additive manufacturing techniques. Complex free-form geometries, irregular shapes, internal and reentrant features, and variable thicknesses can be reproduced using the CAD mo...

Recently, the use of novel CuCr1 surface-modified powder for reliable laser powder-bed fusion (LPBF) manufacturing has been proposed, enabling a broader LPBF processing window and longer powder storage life. Nevertheless, virgin CuCr1 powder is also LPBF processable, on the condition that a high-energy density is employed. In this work, we compare...

The ability to align ex-situ inspection data of an additively manufactured (AM) part to its build geometry can be helpful, for example, to correlate observed in-situ monitoring events or features to measured discontinuities, such as pores and cracks, in ex-situ inspection. In some cases, the original part design does not lend itself to such an alig...

The European Union is promoting the uptake of low emission vehicles to reduce greenhouse gas emissions from transportation. However, this transition will increase the demand for five important battery raw materials; i.e. lithium, nickel, cobalt, copper, and graphite. Therefore, a substance flow analysis and forecasting model are proposed to investi...

Channels and bores in metal components produced by laser powder bed fusion (LPBF) are internal features that are typically affected by defects such as dross and sag formation, dimensional errors and global deformations in different proportions. Such deviations from the ideal geometry may strongly limit the functionality of the channels, but are dif...

This paper presents an algorithm to compensate the systematic error of lasers line scanned data based on the measurement error model of the measurement system. The iterative process of the algorithm is used to determine geometrical features accurately, solely making use of an optical measurement device. The systematic error on the task–specific mea...

Reconstruction algorithms in X-ray computed tomography assume a particular geometrical alignment of the instrument components: X-ray source, sample stage, and detector. Motion errors and misalignments in the actual instrument contribute to errors in the reconstruction. In previous work, we presented an object-based procedure to measure the instrume...

X-ray computed tomography (XCT) is the only non-destructive technique able to perform a complete quality control of additive manufactured products in a single inspection. Yet, high-quality scans are associated with large acquisition times and limited to high-end AM parts. In this paper we investigate a deep learning U-net segmentation algorithm to...

Digital manufacturing is one of the enabling methodologies associated with the concept of flexible mass customization, which has been boosted by the recent advances in Additive Manufacturing (AM) technologies, from which complex freeform geometries, internal and reentrant features can be reproduced based on the CAD model. From the standpoint of coo...

The last decade witnessed an increasing global adoption of electric vehicles. Moreover, the nickel-cobalt-manganese battery chemistry has gained wide acceptance among manufacturers of electric vehicles in Europe. Nevertheless, the environmental impacts associated with recycling this battery technology have not been fully investigated. Therefore, a...

Increasing the durability of electrical and electronics products is key to reduce our worldwide material consumption and the related environmental footprint. A valuable strategy to achieve this goal is extending the useful lifetime of products by means of repair. Methods to assess and rate the repairability of products have been developed recently....

Electric vehicles are sometimes marketed unambiguously as low-carbon technologies; however, they often contain less ‘clean’ ingredients, such as rare earth permanent magnets. In fact, high-performance permanent magnets in electric vehicles often use neodymium. Alternatively, more costly samarium-cobalt magnets can be used. In this paper, life cycle...

Surface topography measurements are vital in industrial quality control. Linear roughness measurements are among the most preferred methods, being quick to perform and easy to interpret. The ISO 16610 standard series prescribes filters that can be used for most cases, but has limitations for restricted measurement lengths. This is because the stand...

The trend of increased use of lithium-ion batteries, challenges the cost-effectiveness and safety of manual battery separation during the end-of-life treatment of Waste Electric and Electronic Equipment (WEEE). Therefore, the need for novel techniques to separate and sort batteries from WEEE is increasingly important. For this reason, the presented...

Computed Tomography (CT) has been used in an upward trend to inspect dimensional and geometric characteristics of manufactured parts. The complexity of the measurement chain, however, gives rise to many influence factors that affect the measurement accuracy. Some of these factors are under the control of the user, who needs to properly set some CT...

This paper presents an unambiguous method to obtain the measurement error model of a laser line scanner, comprising both the systematic error and the random error of a measurement with this type of optical probing system. A ring gauge is used as artefact for the acquisition of the data required for determining the measurement error model. The model...

Robot-CT is drawing great attention for its potential to support highly flexible scan trajectories and various scan modes with a single system. However, the quality of CT reconstruction largely depends on accurate knowledge of the scan geometry, i.e. position and orientation of the source and the detector. This imposes major challenges on current s...

The characteristics of the X-ray focal spot strongly influence XCT image sharpness and structural resolution. However, current international standards only yield a limited characterization of the focal spot as two perpendicular sizes. Therefore, this paper presents a method for full characterization of the focal spot in terms of both 2D shape and i...

Rare Earth Elements (REEs) are one of the most important--albeit critical--commodities for our green technologies. However, there is a general perception that REEs are produced using mining and processing techniques that are unsustainable. Life Cycle Assessment (LCA) is the most widely accepted methodology to evaluate the environmental impacts of r...

The quality of mechanically recycled plastics from WEEE is seen as one of the main bottlenecks for their re-application in high-quality products to enable a circular economy for these materials. Most literature focuses on the quality at the end of the value chain while significant potential to improve the performance of the entire value chain is se...

The closed-loop recycling of PolyCarbonate/Acrylonitrile Styrene Acrylate (PC/ASA) housings from post-consumer payment terminals that are subject to a take-back scheme is presented. The technical feasibility is evaluated by means of mechanical and rheological testing. Compared to virgin PC/ASA, a loss in impact strength is found to be the main bott...

Managing the waste stream of lithium ion batteries from electric vehicles is an emerging challenge. Therefore, a distribution delay forecasting model is developed considering multiple end-of-life options for battery applications; including replace, reuse, repurpose and recycle. This model is used to forecast the characteristics of the waste stream....

Because of the low concentrations of Tantalum on printed wiring boards, today it is not economically viable to recycle Tantalum in pyro- and hydrometallurgical processes. However, in case the Tantalum can be up concentrated, the recycling of the Tantalum can become economically viable in the multi-stage process used to refine Tantalum from ores. Th...

Numerous challenges of additive manufacturing (AM) are tackled in the European Horizon 2020 project PAM^2 by studying and linking every step of the AM process cycle. For example, PAM^2 researchers from the design, processing and application side have collaborated in this work to optimise the manufacturability of metal AM parts using an improved Top...

This two paper series describes a method to develop and evaluate innovative recycling strategies for WEEE plastics. Part A presents a SWOT analysis of a new dismantling based recycling process of plastic components and the integration in an existing post-shredder separation recycling facility. Subsequently, recycling strategies are developed and th...

A new beam hardening correction (BHC) method for multi-material industrial computed tomography (CT) is presented. Our method is a statistical learning approach of the Joseph and Spital (JS) segmentation framework. It consists of four steps. First, a multi-dimensional surface and its corresponding hyperplane are simulated based on the x-ray transmis...

Additive metal manufacturing processes, such as laser powder bed fusion, still show difficulties when producing overhang features or internal structures such as channels or bores. Channels are often mutilated by sag defects and dross formation at their upper part, when the channel-axis is close to parallel to the base plate and in the particular ca...

This work investigates the effect of the powder particle size distribution on the surface finish of Maraging 300 specimens, produced by the Laser Powder Bed Fusion (LPBF) process. Although it is recognized that the initial powder morphological characteristics play an important role on LPBF part density, mechanical properties and surface quality, th...

In this study the accuracy of downfacing surfaces of small LPBF (Laser Powder Bed Fusion) fabricated features is investigated. Calibration geometries with downfacing angles ranging from 75° to 25° are printed in three different layer thicknesses to quantify the dimensional error due to dross formation and other melt pool phenomena in the downfacing...

This paper reports on the results of a round robin test conducted by ten X-ray micro computed tomography (micro-CT) laboratories with the same three selected titanium alloy (Ti6Al4V) laser powder bed fusion (L-PBF) test parts. These parts were a 10-mm cube, a 60-mm long and 40-mm high complex-shaped bracket, and a 15-mm diameter rod. Previously dev...

The additive manufacturing (AM) of injection molding inserts has gained popularity during recent years primarily due to the reduced design-to-production time and form freedom offered by AM. In this paper, topology optimization (TO) is performed on a metallic mold insert which is to be produced by the Laser Powder Bed Fusion (LPBF) technique. First,...

This two paper series describes a method to develop and evaluate new recycling strategies for WEEE plastics. Part A presents a SWOT analysis that leads to five recycling strategies for the optimal integration of new dismantling based recycling processes for plastic components in an established post-shredder separation infrastructure. In this paper...

Triply periodic minimal surfaces (TPMSs) have attracted increasing attention for their high manufacturability, biocompatibility, and mechanical properties. In this work, graded Gyroid cellular structures (GCSs) with varying gradient directions were mathematically designed and manufactured via selective laser melting (SLM). The effect of gradients o...

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 th...

Airplane engines are vital aircraft components, so regular inspections of the engines are required to ensure their stable operation. A dynamic computed tomography (CT) system has been proposed by our group for in situ nondestructive testing of airplane engines, which takes advantage of the rotor’s self-rotation. However, static parts of the engines...

Life cycle engineering (LCE) targets product development and manufacturing activities in a life cycle perspective, with the aim to create more sustainable solutions. Coined approximately 30 years ago, it was adopted by the International Academy for Production Engineering (CIRP, from the French title), which established annual conferences on life cy...

Waste Electrical and Electronic Equipment (WEEE) comprises a complex mix of engineering plastic grades often containing flame retardants. Whereas post-shredder recycling strategies are widely implemented, considerably higher economic and environmental returns can be expected based on information-rich dismantling scenarios. This paper therefore pres...

Owing to recent advancements in the field of machine learning, such as deep convolutional neural networks (CNN), new applications in image processing have become feasible. The aim of this study was to explore the use of CNNs for the correction of X-ray scatter and beam hardening in industrial computed tomography. Through simulation, a large heterog...

The X-ray spectrum provides important information for many industrial CT tasks. Transmission measurement based methods have long been employed in X-ray spectral estimation. There are two advantages of this method. First, no photon counting detector is needed. Second, the detector response is included in the estimation. However, these methods are su...

The occurrence of keyhole porosity in selective laser melting (SLM) has so far not been quantified systematically using X-ray computed tomography (X-CT). In this study, keyhole porosity in selective laser molten Ti-6Al-4V grade 23 parts was analyzed using post-process characterizations. Single tracks were produced with optimum, high volumetric ener...

A newly developed software-based compensation of geometrical misalignments is applied to several computed tomography (CT) instruments. The actual geometry of each CT instrument is measured using a dedicated procedure. Then, given the measured geometries, software-based compensation is applied. Dimensional measurements on a validation object show a...

The occurrence of keyhole porosity in Ti-6Al-4V parts manufactured by selective laser melting (SLM) has not been systematically quantified using post-process characterizations. The X-ray computed tomography (X-CT) technique is capable to analyse the size, shape, location, and number of keyhole pores in SLM parts. In this study, keyhole porosity in...

The occurrence of keyhole porosity in selective laser melting (SLM) has so far not been quantified systematically using X-ray computed tomography (X-CT). In this study, keyhole porosity in selective laser molten Ti-6Al-4V grade 23 parts was analyzed using post-process characterizations. Single tracks were produced with optimum, high volumetric ener...

Worldwide every year 41.8 billion tons of electrical and electronic equipment (EEE) reaches the end-of-life with changing designs, product, and material compositions. In order to enable the recycling industry to adapt its processes to the evolutions in product design and material composition, it is crucial to assess these changes in waste streams....

Repairing modern electrical and electronic equipment is becoming increasingly difficult. The encountered challenges significantly contribute to the costs associated with repair, making direct replacement of a product often the most straightforward option for the consumer. Therefore, the Benelux Union has requested a study to investigate extending p...

The European Union is setting increasingly challenging targets for the waste recycling rates of its member states. This makes improvements in recycling processes, such as dense medium metal separation, a necessity. Dense medium metal separation takes place in a dense medium drum separator where the light metal floats and can be easily separated fro...

en Beam hardening artefacts deteriorate the reconstructed image quality in industrial computed tomography. The appearances of beam hardening artefacts can be cupping effects or streaks. They impair the image fidelity to the object being scanned. This work aims at comparing a variety of commonly used beam hardening correction algorithms in the conte...

Beam hardening artefacts caused by the polychromatic nature of the x-ray spectra are known to deteriorate the reconstructed image quality in multi-material industrial computed tomography. A variety of beam hardening correction (BHC) algorithms exist. Most of these methods rest on the x-ray spectra to a certain extent, which means their performance...

This study demonstrates that, after adequate scaling error compensation, industrial µ-CT could be a viable metrological technique to derive, with one measurement, primary characteristics of Additive Manufacturing metal powders used in Powder Bed Fusion processes. For distribution and shape analyses, special care must be employed on the ISO value de...

The overall aim of this study is to evaluate and, if possible, quantify the ease of repair for energy-related products (ErPs) considering the economic impact from a consumer perspective. In order to meet this objective, repairability criteria for ErPs are proposed. The developed criteria are in accordance with the ongoing initiative of the CEN-CELE...