Joost Duflou

• Prof. Dr. ir.
• Professor at KU Leuven

Improving energy efficiency has become a crucial priority, as the laser cutting industry is moving toward higher power levels and dealing with increasing energy costs. Recent advancements aim to enhance process performance by optimizing the intensity distribution of the laser beam. This paper evaluates the energy consumption of laser cutting using...

Magnesium-zinc-zirconium (Mg-Zn-Zr) alloys, with their biocompatibility and biodegradability, exhibit great potential for biomedical applications. However, forming complex geometries poses a challenge due to the low formability of magnesium. Single Point Incremental Forming (SPIF) has emerged as a promising rapid manufacturing technique capable of...

Recent advances towards patient specific titanium sheet based medical implants introduce a new challenge for the fixation of these implants to bones. Mainly, the use of locking screws requires an implant thickness of approximately 2 mm for screw thread formation. Friction drilling is a hole-making process that displaces material to create a bushing...

Cutting thick plates is affected not only by the laser power but also by the cut kerf width and the melt flow dynamics that determine the ejection of the molten material. Employing the same laser beam intensity distribution for various thicknesses is the limiting factor when cutting thicker plates. This paper investigates fiber laser fusion cutting...

A significant improvement in laser cutting productivity and quality can be achieved using dynamic beam shaping (DBS). However, the broad potential of improving the cutting performance of thick plates by employing DBS has not been fully explored. This paper uses an extensive experimental campaign to evaluate laser cutting results using DBS for diffe...

Current supportive bio-inspired design methods focus on handcrafting the inspiration engineers use to speed up bio-inspired design. However promising, such methods are not scalable as the time investment is shifted to an up-front investment. Furthermore, most proposed methods require the engineer to adopt a new design process. The current study pre...

The optimization of laser cutting process parameters relies on productivity and obtained edge quality. Whereas maximizing cutting speed is a default procedure to increase the process performance, quality assessment of a cut edge is a non-trivial task. Both contact-based and image-based approaches can be used to quantify the quality of a cut surface...

This paper provides an analysis of the Rigid Body Motion (RBM) in multi-stage Single Point Incremental Forming of a cylindrical cup. The RBM is studied using Digital Image Correlation to track the material in each contour of the tool, resulting in a better understanding of the RBM phenomenon than has been shown in literature. The study shows that t...

The envisaged flexibility of Single Point Incremental Forming is contradicted by its highly complex deformation behavior, making the process easy to implement but difficult to fully control. This paper describes a regression method that uses Gradient Tree Boosting to predict the deviations for a given input geometry, which can replace the physical...

A dramatic increase in the industrial demands for tailoring the laser beam profile in laser cutting has led to significant performance improvements thanks to the recently emerging dynamic beam shaping technology. Nonetheless, the underlying reasons for such process improvements are not fully understood yet, and mainly theoretical assumptions are av...

Automatic quality assessment of laser cut parts is an essential building block in the deployment of data-driven strategies for process parameter optimization, predictive maintenance and continuous improvement in sheet metal workshops. From an industrial perspective, the major quality features of a laser cut edge are roughness, perpendicularity devi...

Further improvement of quality and productivity are some of the most relevant laser cutting process challenges. One way of affecting the process performance is manipulating the laser beam intensity distribution. Within this work, the feasibility of enhancing the cutting speed and edge quality using dynamic beam shaping in 4 kW fiber laser cutting o...

Dynamic beam shaping brings a large potential for the laser cutting process by increasing the cutting speed and improving the cut edge quality. However, laser beam oscillation is almost exclusively realized with 2-mirror galvanometer scanners that limit the industrial implementation of the technology. Within this work, a new concept platform based...

Heat accumulation during laser flame cutting of thick mild steel plates is a problem well acknowledged both in industry and academia. If not considered carefully, elevated plate temperatures can lead to significant quality degradation or even cut failure. As a result, several approaches have been proposed in the literature to mitigate the negative...

This paper discusses the thickness distributions calculated from surface strain measurements using stereo Digital Image Correlations (DIC) for parts produced with Single Point Incremental Forming (SPIF). The research is carried out on six benchmark cones and pyramids with each convex, straight and concave walls. The accuracy of the thickness calcul...

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...

In recent years, most press brake manufacturers have developed systems for automatic machine setup. During a setup operation, a machine layout is built both through loading and unloading of new segments and through repositioning of previously loaded segments. To decrease the number of time-consuming repositioning operations and thus increase the ef...

Recycling of Waste Electrical and Electronic Equipment (WEEE) is challenging due to the high variety in both the design and composition of the products in this waste stream. Therefore, targeted demanufacturing and appropriate material sorting processes are crucial, but remain often a manual and thus labor-intensive and costly activity. Despite firs...

Product life time extension is an important strategy for reducing the impact of electric and electronic devices. Unfortunately, the declining number of companies offering repair services over the last decade, is not compatible with this objective. Some of the main challenges for repair companies are the high costs related to labor, logistics and sp...

Measuring circularity is a hot topic and has gained a lot of attention among policy makers, companies and academia. Such indicators are often applied to assess the implementation level of more circular supply chains. Although life cycle assessment (LCA) will remain important to ensure our industrial activities contribute to an economic system with...

Process visualization is typically used to explore different phenomena involved in laser material processing. The interaction between the laser beam and the workpiece material creates different emission sources during the laser cutting process, as a result of material heating, beam reflection and scattering, which can be visualized with the appropr...

The probable emergence of a global aluminium scrap surplus in the coming decade is one of the main incentives for the aluminium recycling industry to invest in new methods and technologies to collect, sort and recycle aluminium scrap. However, due to the considerable uncertainty in the evolution of the global scrap surplus, it is difficult for poli...

Triggered by smart and zero-defect manufacturing paradigms, in situ quality assurance has become an emerging necessity for industrial laser cutting. Within this work, several real-time monitoring concepts have been tested for 4 kW Ytterbium fiber laser flame cutting of 15 mm mild steel plates. Cut quality deteriorations caused by cutting at varying...

Laser cutting is a well-established industrial process for sheet metal applications. However, cutting thick plates is still accompanied by problems because of the characteristic limited process parameter window. Since cutting by means of fiber lasers has become dominant, tailored solutions are required in such systems for industrial applications. T...

Current fixation plates used to operatively stabilize clavicular fractures are suboptimal, leading to reoperation rates up to 53%. Plate irritation, which can be caused by a poor geometric fit and plate thickness, has been found to be an important factor for reoperation. Moreover, muscle attachment sites (MAS) have to be detached occasionally. To i...

Using bio-inspiration allows engineers to use the knowledge implicitly built up by natural evolution. Current tools for providing engineers with bio-inspiration yield many biological working principles. Starting from the Linnaean taxonomy, which can be seen as a design revision history, this work proposes metrics for a working principle based on th...

Biologicalisation calls for the integration of biological knowledge in manufacturing. Although biologists have been cataloguing biological knowledge for centuries, for the non-biologist finding this inspiration as input for bio-inspired design is a major challenge. In this paper, three different methods are used to find bio-inspiration for a case s...

The paper explores and presents results of an investigation handling design methodologies using the bio-space and biological phenomena combined with the technical space for the development, design and application of products, machine tools, processes and manufacturing systems carried out by a multinational team including Fraunhofer and CIRP fellows...

Quality assessment of parts produced by laser cutting is a time-consuming task which typically requires expert knowledge. One of the main characteristics determining the quality of a cut edge is the roughness of the striations profile generated during the cutting process. Usual practice is to measure roughness by means of contact-based profilometry...

Energy conservation is of increasing importance in contemporary society. A large fraction of energy end-use can be attributed to space conditioning. Therefore, intelligent control systems were devised and commercialised in the form of smart thermostats. Hereto, the availability of occupancy information is essential such that heating and/or cooling...

Knowledge of the correct temperature distribution on the cutting front is essential to understand and quantify the thermo-fluid dynamics during laser cutting, which are directly related to the edge quality. For that purpose, hyperspectral imaging, coupled with trim-cut observations with boundary conditions close to industrial processing, have been...

The complex composition of waste electrical and electronic equipment (WEEE) plastics represents a challenge during post-consumption plastic recycling. A single WEEE category, e.g. large household appliances (LHA), can contain several different plastic types with overlapping material properties, making the sorting of individual plastics a challenge....

Pallets and forklifts equipped with Radio-Frequency Identification (RFID) technology can be a suitable option for bridging the information gap between cutting and bending stages in sheet metal production. However, a decision on how tagged pallets can be assigned to their content needs to be made. In this paper, a reactive and a proactive approach f...

Despite years of supporting research, commercial use of the Single Point Incremental Forming process remains very limited. The promised flexibility and lack of specific tooling is contradicted by its highly complex deformation mechanics, resulting in a process that is easy to implement but where workpiece accuracy is very difficult to control. This...

While Incremental Sheet Forming (ISF) is approaching accuracy levels suitable for industrial take-up for specific applications, limited forming angles are still a great concern, leaving many applications out of reach. In this paper a two sided strategy for multistep incremental forming is presented, aiming at increased uniform wall thickness. By se...

Harmonic decomposition is an analytical technique that is able to express a manifold surface as the sum of a number of simple surface harmonic components. By reconstructing the initial geometry using a reduced number of components, a similar surface is obtained with a lower level of geometric detail. Because small features are filtered out and the...

Several studies in laser cutting literature have demonstrated that quality aspects of the laser cut edge, such as dross attachment, surface roughness and striation pattern, are highly influenced by the melt flow dynamics. Therefore, in order to visualise the laser cutting process, the trim-cut technique was conceived several decades ago and has bee...

The paper explores and presents results of an investigation handling design methodologies using the bio-space and biological phenomena combined with the technical space for the development, design and application of products, machine tools, processes and manufacturing systems carried out by a multinational team including Fraunhofer and CIRP fellows...

Prescriptive ecodesign tools aim to aid designers in creating more sustainable designs by providing them with general recommendations, relying on the designer to adapt and convert such recommendations into a creative concept. This class of ecodesign methods relies on - and is limited by - the creativity and previous knowledge of the designer. In co...

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....

Laser cutting is a conventional and well-established industrial process within the sheet metal working domain. However, processing of thick plates remains a major problem due to the limited process window. Real-time monitoring for adaptive control might significantly decrease the risk of a cut fail. Up to this point, most studies were mainly focuse...

Modelling the occupancy of buildings, rooms or the usage of machines has many applications in varying fields, exemplified by the fairly recent emergence of smart, self-learning thermostats. Typically, the aim of such systems is to provide insight into user behaviour and incentivise energy savings or to automatically reduce consumption while maintai...

Biologicalisation calls for the integration of biological knowledge in manufacturing. Although biologists have been cataloguing biological knowledge for centuries, for the non-biologist finding this inspiration as input for bio-inspired design is a major challenge. In this paper, three different methods are used to find bio-inspiration for a case s...

For many years, regulation and life cycle studies have focussed on reducing the environmental footprint of vehicles. Despite the implementation of different end-of-life vehicle (ELV) regulations to encourage material reuse and to increase recycling and recovery rates, it is unclear how these policies are progressing towards realising a circular eco...

Adaptive real-time monitoring and control is a natural solution for automated unmanned laser cutting that has been intensively studied for the last decades. However, sensor solutions for laser cutting are rarely used in practice. In this paper, a coaxial photodiode-based monitoring system has been developed and investigated for 4 kW fiber laser cut...

Excessive heating of the metal sheet during laser oxygen cutting can cause quality deterioration and even lead to cut loss and possible machine idle time, especially for cutting of thick plates, where the cutting speed is slower. There are at least three different strategies to handle quality deterioration by heat accumulation in flame laser cuttin...

The ambition to extend material recycling from end-of-life electric and electronic products seems to lead to an unavoidable trade-off between circularity maximisation and quality concerns. However, optimized pre-treatment can help to assure that both polymer fraction compatibility and imperfect separation with the available technologies are fully t...

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 usage of high strength steels is a viable option for improving existing sheet metal constructions manufactured by air bending. This improvement can be achieved through increased payload, lighter structures or enlarged safety margins. Unfortunately, as these materials have limited cold formability, usually high strength steels cannot be formed w...

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...

An intelligent control system has been developed in the form of a smart thermostat that takes into account the expected occupancy. The use of the smart thermostat allows to save energy without jeopardizing the user's comfort requirements. The goal of this paper is to estimate the required minimal energy saving to achieve environmental and economic...

The muscle footprint anatomy of the clavicle is described in various anatomical textbooks but research on the footprint variation is rare. Our goal was to assess the variation and to create a probabilistic atlas of the muscle footprint anatomy. 14 right and left clavicles of anatomical specimens were dissected until only muscle fibers remained. 3D...

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...

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...

The increasing demand for materials is a barrier to achieving a truly circular value chain. As long as the demand increases, extraction of virgin material will remain necessary. Furthermore, as we keep injecting pure virgin material in our value chain, the impurities that are added along the different life cycle stages are diluted. For this reason...

For most materials the tensile curve can be fitted with one of the usual constitutive laws: pure plasticity, linear hardening, Hollomon, Nadai, Swift or Ludwik. However, high strength steels, due to a specific hardening behavior, cannot be accurately characterized with one of the above-mentioned laws. The same is true for the unit bending moment th...

Conventional anatomically contoured plates do not adequately fit most tibiae. This emphasizes the need for a more thorough morphological study. Statistical shape models are promising tools to display anatomical variations within a population. Herein, we aim to provide a better insight into the anatomical variations of the tibia and tibia plateau. S...

The industrial importance of air bending applications with high-strength steels has increased in recent years. However, the limited cold formability of high-strength steels requires the application of punches with large radii. The usage of large radii tooling leads to a change of the loading scheme from traditional 3-point to 4-point bending. There...

Surface registration, in which a mapping between surfaces is calculated, is a powerful tool to create patient-specific musculoskeletal and statistical shape models. However, to create these models, surface registration must assure a one-to-one correspondence between both surfaces. To enhance this process, a surface registration framework that uses...

Background: The clavicle presents a large variability in its characterizing sigmoid shape. Prominent and nonproperly fitting fixation plates (FP) cause soft tissue irritation and lead to hardware removal. It is therefore key in FP design to account for shape variations. Statistical shape models (SSMs) have been built to analyze a cluster of complex...

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...

The contamination of aluminium streams during the different life cycle stages by alloy mixing and/or accumulation of foreign elements, in combination with the limited melt purification options during remelting, represents an important limiting factor in recycling. Consequently, in secondary aluminium production, primary aluminium is used to dilute...

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....

Analytical predictions and black box approaches are well-known strategies for the prediction of forming processes. Each of them has its own advantages and weaknesses. Analytical predictions lack flexibility, but usually have a strong theoretical foundation. Black box approach means models based purely on empirical data, these models provides tailor...

Conventional or small radius air bending has been modeled and analytically described by many authors. This process is traditionally called 3-point bending. When using a large radius punch for design reasons or because it is necessary when bending high strength steels, a new phenomenon arises.The contact area between the punch and the plate, which i...

Single Point Incremental Forming owes its flexibility to lack of dedicated tooling needed to create a variety of different geometries. This is possible because of its computer controlled nature: the toolpath that is executed will determine the shape of the produced part. By altering the toolpath in a smart way, the process can be optimized towards...

Laser cutting of metal sheets is a well-established industrial process, however, major process changes are constantly being introduced by newer technologies, e.g. new laser technologies, higher power sources, polarization and beam shaping control units, and gas flow optimizations. The multi-physical nature of the laser cutting process makes detaile...

Experimental data can provide a rich source of information and opportunities for the improvement of production processes. This paper provides a conceptual description of a data-driven model and discusses its possible implementation strategies. Two data-driven methods are applied to air bending, a conventional sheet metal forming process. Self-impro...

Angular precision of air bending is directly related to the precision of the calculated punch stroke, which is computed in order to achieve the required sheet profile before the springback. The calculated springback accuracy depends on the elasticity modulus which, as it is well-known, decreases with increase of plastic prestrain. During the bendin...

Although Incremental Sheet Forming has overcome a number of challenges, its notorious lack of accuracy and need for high formability withholds this process from wide industrial adoption. This study aims to improve accuracy and formability through the use of an elliptical tool. The increased freedom of combining a large curvature in one direction an...

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...

Aluminum alloys are characterized by high-energy demands for primary production. Recycling is a well-documented strategy to lower the environmental impact of light alloys production. Despite that, conventional recycling processes are still energy-intensive with a low energy efficiency. Also, permanent material losses occur during remelting because...

The increasing demand for aluminium (Al) has led to the significant growth of secondary Al production. Although Al is one of the most recycled metal streams, the presence of impurities, such as iron, silicon and copper, has limited the environmental and economic benefits of recycling Al. These competing interests have led to the choice of recycling...

Incremental sheet metal forming in general and Single Point Incremental Forming (SPIF) specifically have gone through a period of intensive development with growing attention from research institutes worldwide. The result of these efforts is significant progress in the understanding of the underlying forming mechanisms and opportunities as well as...

An accurate analytical method is normally the preferred choice in engineering practice since this approach usually does not require additional software and can be applied for different situations. A number of analytical methods have been proposed for the air bending process, however, none of them has the capacity to deal with large radius bending....

The strong effect that beam polarization has on the performance of industrial laser cutting is well known. The linear and circular polarization states were widely investigated for CO2 lasers. These two states are, in fact, special cases of elliptically polarized laser beams. Theoretical models have predicted an optimal cutting performance for a spe...

The usage of the high-strength steels in air bending is limited due to the insufficient cold formability of these materials. One way to extend the air bending process range is to expose the bent plates to high temperatures. In this contribution, radiant heating by means of infrared lamps is utilized for locally heating the plates. A radiant heating...

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...

Flexibility in metal forming is needed more than ever before due to rapidly changing customer demands. It paves the way for a better control of uncertainties in development and application of metal forming processes. Although flexibility has been pursued from various viewpoints in terms of machines, material, process, working environment and proper...

Laser material processing is a technology with an increasing number of industrial applications, especially for aviation and automotive. The present keynote paper focusses on the advances in macro-scale laser processing, meaning that the laser generated structures are large enough to be visible with the naked eye. Next to that, also the reasons for...