Dielectric elastomer actuators (DEA) have gained increased attention in the design of electrically driven soft and lightweight robotic devices. They rely on Coulomb forces for their actuation and are able to undergo large displacements as a function of the applied electrical field. Fabricating DEAs with additive manufacturing opens the way to a personalized and cost-efficient fabrication of soft active devices. In particular, extrusion-based techniques provide a versatile strategy to multi-material 3D print DEAs by using electrically conductive and soft filaments with high elongation. One key aspect of DEAs is the electrode's performance, which has to provide a high electrical conductivity and a good adhesion to the sandwiched membrane. Herein, selected 3D printing parameters were varied to optimize the electrode infill density and electrode infill direction. Mechanical and electrical properties, as well as actuation performance, of fully 3D-printed DEA demonstrators were studied comprehensively. With the optimized parameter set, a maximum DEA displacement of 91% was achieved with respect to the free length of the actuator. This is comparable to the performance of non-3D-printed DEAs and demonstrates the potential of 3D printing for the production of DEAs undergoing large deformations while leveraging the design and manufacturing freedom of multi-material 3D printing.

This study investigates the influence of injection volume rate (IVR) on local temperature development in a narrow slit and its effects on the mechanical and molecular properties of unfilled polyamide 6.6 (PA 6.6). An in-situ measurement setup was developed to capture high-resolution temperature profiles across the melt flow path during injection molding. Increasing IVR resulted in a substantial rise in peak melt temperatures, exceeding 500 °C at high IVR in the center region of the slit. However, these extreme temperatures were sustained only for fractions of a second, and the 350 °C threshold was never maintained for more than 2.5 s under any condition. Based on these thermal profiles, significant thermo-oxidation degradation might be expected. Nevertheless, differential scanning calorimetry with oxidative induction time (DSC-OIT) and gel permeation chromatography (GPC) and Fourier Transform Infrared Spectroscopy (FTIR) revealed no measurable signs of chemical degradation. Mechanical properties showed only minor variations, most likely arising from physical effects such as molecular orientation and chain entanglement rather than chemical changes. These findings indicate that, within the investigated processing window, high IVR can induce extreme but short-lived thermal loads without compromising polymer integrity.

The growing demand for sustainable manufacturing necessitates innovative strategies to upcycle recycled and regenerated polymers into high-performance, lightweight components. The objective of this study is to evaluate the feasibility and performance of the Injection Moulding Compounder (IMC) as an integrated one-step processing route for manufacturing lightweight components from recycled polymer systems. Numerical simulations using Ansys POLYFLOW (R) were employed to analyse the effects of process design on pressure build-up, shear stresses, and residence time within the IMC system, and the modelling outcomes were validated against experimental measurements. Post-consumer recycled polypropylene (PP) blended with shredded post-industrial glass fibre-reinforced PP served as the material feedstock. Comprehensive thermal, rheological, and mechanical characterization of the one-step IMC-processed components revealed nominal differences with conventionalprocessed components, which compounded in a twin-screw extruder and then injection moulded. Regarding mechanical properties, less than 10% differences were observed in the tensile and flexural properties, showing the similarity of the components produced by IMC and conventional method. The novelty of this work lies in the combined numerical and experimental assessment of the developed IMC for the direct processing of recycled, fibre-reinforced thermoplastics. The results demonstrate that the proposed single-step process can achieve mechanical performance comparable to conventional processing routes while reducing material handling and processing complexity. These findings highlight the IMC's capability to couple material performance enhancement with environmental benefits, highlighting its role as a scalable pathway for circular economy implementation and the advancement of resource- and energy-efficient polymer processing technologies.

For state-of-the-art hard thin films deposited by various vapor deposition techniques to alter mold filling and facilitate demolding of plastic parts, relevant properties are often not explicitly reported, leaving toolmakers and plastic processors reliant on third-party expertise. The purpose of this study was to characterize the geometrical and physico-chemical properties of hard thin films, which directly influence plastic-mold interfacial phenomena, and to compare these properties with those of steel X40Cr14. Phase structure was analyzed by XRD and Raman spectroscopy, the surface morphology, film thickness, and texture were assessed by scanning electron microscopy and interferometry. These properties are primarily affected by the deposition technique and processing conditions. The elemental composition was determined by energy-dispersive X-ray spectroscopy. Compared to the coating bulk, the near-surface region exhibited material-and deposition-dependent oxygen contents, indicating surface oxidation. Surface free energy under typical micro-molding temperatures (60-120 degrees C) was determined from wetting experiments. Hard thin films exhibited more stable wettability than steel, attributed to their higher surface homogeneity. Among the transition metal nitrides, CrN showed the lowest total and polar surface energy, while TiN exhibited the highest. Amorphous hydrogenated carbon showed considerably higher values. Surface free energy decreased significantly with increasing temperature, with binary high-impulse magnetron sputtered nitride films showing the strongest inverse correlation due to smooth surfaces and chemical composition. The findings highlight the wide range of thin film properties affecting interfacial phenomena, guiding material and deposition technique selection for plastic micro-molding and informing future research in hard thin films, tool making, and micro-molding.

This study presents the development and evaluation of a novel titanium feedstock for metal material extrusion additive manufacturing, using a partially bio-based backbone system composed of polylactic acid and polybutylene adipate terephthalate. To improve printability and flexibility, various combinations of polylactic acid/polybutylene adipate terephthalate and thermoplastic elastomers were investigated. Seven distinct binder formulations were prepared using 55 vol

This study investigates the sustainable production of NdFeB permanent magnets using powder extrusion molding (PEM) with in situ magnetic alignment, utilizing recycled powder from an end-of-life (Eol) wind turbine magnet obtained via hydrogen processing of magnetic scrap (HPMS). Finite Element Method (FEM) simulations were conducted to design and optimize alignment tool geometries and magnetic field parameters. A key challenge in the PEM process is achieving effective particle alignment while the continuous strand moves through the magnetic field during extrusion. To address this, extrusion experiments were performed using three different alignment tool geometries and varying magnetic field strengths to determine the optimal configuration for particle alignment. The experimental results demonstrate a high degree of alignment (Br/Js = 0.95), exceeding the values obtained with PEM without an external magnetic field (0.78). The study confirms that optimizing the alignment tool geometry and applying sufficiently strong magnetic fields during extrusion enable the production of anisotropic NdFeB permanent magnets without post-machining, providing a scalable route for permanent magnet recycling and manufacturing. Moreover, PEM with in situ magnetic particle alignment allows for the continuous fabrication of near-net-shape strands with customizable cross-sections, making it a scalable approach for permanent magnet recycling and industrial manufacturing.

For the processing of metal powders by Metal Injection Moulding (MIM) or indirect methods of Additive Manufacturing (AM), such as material extrusion (MEX-AM) polymers of different kinds are employed. Usually, the task of these polymers is to enable the shaping of a certain geometry and to maintain this shape down to the first cohesive effects of sintering. Nowadays, for the production of metal parts one goal is to get rid of the polymer as complete as possible. Another possibility is to use the polymer or at least part of it, mainly the carbon, for the metallurgical process of forming the final part in sintering as a process of heat treatment. Titanium is a metal, which is reacting with carbon easily. The question in focus here is how to utilise the carbon or some of it in the powder metallurgical processing of titanium. For first steps into this question, we selected two different powders, CPTi and TiH 2 , and mixed them with two different polymers, polypropylene PP and low-density polyethylene LDPE. As a compatibilizer stearic acid SA was used. The polymers were selected because they are normally used as backbone in binder systems, and show a significantly different thermal degradation behaviour. Thus, the amount and type of carbon during thermal degradation could be expected to be different. The study comprises the preparation of polymer-powder blendings with up to 80 vol.% powder to resemble the conditions after solvent debinding; the shaping in discs, and TG-DTA experiments in air and in Ar to find out the temperature of backbone removal (Tr). Isothermal experiments are also done to know about the polymer removal with time. The different interaction of the polymers with the titanium powders is investigated, with a special attention to the interaction of hydride decomposition and polymer degradation. Keywords: Metal Injection Moulding; indirect Additive Manufacturing; titanium and titanium alloys; powder-polymer interaction

This study investigates the influence of viscous dissipation on the wear behavior and near‐surface hardness of five tool steels during injection molding of glass‐fiber‐reinforced PA66. Wear tests are performed at two injection volume rates (IVR: 100 and 300 cm 3 s −1 ), supported by temperature monitoring, hardness profiling, and microscopic surface analysis. At low IVR, all steels show wear values below 0.4 mg with no detectable hardness loss, indicating suitability for long‐term use under moderate conditions. Clear differences emerge at high IVR: the conventional steel X153CrMoV12‐1 exhibits severe wear, while powder‐metallurgical steels (X270CrVMo20‐7‐1, X190CrVMo20‐4‐1, HS6‐5‐3‐8) display superior resistance. X270CrVMo20‐7‐1 shows the highest robustness, whereas X190CrVMo20‐4‐1 suffers pronounced hardness loss and stronger wear, performing similarly to HS6‐5‐3‐8 but through different mechanisms. X190CrVMo20‐4‐1 relies on carbides at the expense of matrix stability, whereas HS6‐5‐3‐8 retains wear resistance through its inherently high hardness, unaffected by viscous dissipation. The results demonstrate that wear resistance in polymer processing is governed not solely by carbide stability or matrix hardness, but by their interplay under thermomechanical loading. Viscous dissipation acts as a decisive factor amplifying material differences. These findings offer guidance for steel selection and provide evidence to refine wear models, especially for fiber–surface interactions and temperature‐dependent material responses.

The development of aluminium (Al) feedstocks for the Metal Material Extrusion (MMEX) process has garnered significant attention due to the growing demand for lightweight and sustainable manufacturing solutions. Achieving optimal feedstock formulations is essential to ensure printability, mechanical performance, and efficient post-processing.Given the relatively low sintering temperatures of Al alloys, which are close to the degradation temperatures of common polymeric binders, the thermal stability of binder components becomes a crucial factor. This study investigates the development of binder systems that optimize extrusion quality and explores the use of less hazardous solvents, such as acetone, for solvent debinding. A comprehensive evaluation of thermal properties (via DSC and TGA), rheological behaviour, contact angle measurements, printability and solvent debinding performance was conducted to identify suitable TPE and solvent. The findings reveal that while acetone can be employed as a solvent, achieving sufficient solubility for most TPEs in acetone remains a significant challenge.

For successful injection moulding simulations, the viscosity change under shear and various temperatures must be reliably determined in a fashion that is as close as possible to the injection moulding reality. Within this context and motivated by it, this work presents a critical comparison among state-of-the-art methodologies currently employed to determine liquid silicone rubber’s resistance to shear flow: rotation-based (oscillatory and steady modes) and pressure-driven (based on the application of a high pressure capillary rheometer, HPCR). Among these methodologies, the steady shear rotational approach and the HPCR deliver viscosity values that are in accordance with each other. This fact is justified by the sample’s state under shear: the filler structure is disturbed during both experiments, reaching a common ground for viscosity determination. On the other hand, oscillatory experiments under linear viscoelastic conditions deal with a sample with intact filler network under mechanical equilibrium, giving rise to the Cox-Merz proposition disagreement. When non-linear viscoelastic conditions are met, i.e., high strain amplitudes are applied, causing a shift out of mechanical equilibrium, all methodologies lie in the same viscosity trend within a shear range. This correlation can serve as a shortcut for viscosity determination applied to material data characterization, leading to faster experiments and more accurate polymer processing simulations.

This study investigates the impact of material composition and processing parameters on glass fibre-reinforced recycled polypropylene (rPP) flakes through mechanical and rheological testing. Using a three-factor, three-level Box-Behnken Design (BBD) within Response Surface Methodology (RSM), the effects of glass fibre flake content, additive content, and extruder screw speed on the properties of injection-moulded samples were evaluated. Analysis of variance (ANOVA) and cross-validation were conducted to assess the influence of these parameters on tensile and rheological properties. The key objective was to maximize tensile modulus (Et) without compromising tensile strength. The results showed a 60 % increase in Et by optimizing extruder screw speed and flake content, achieving the highest Et (4.1 GPa) at a screw speed of 150 rpm, 50 wt% flake content, and 5 wt% additive. The additive contributed up to a 20 % increase in Et but primarily influenced rheological behaviour. Glass fibre flake content was the most significant factor affecting mechanical and rheological properties, with additive content enhancing flow characteristics. These findings highlight the potential to optimize glass fibre-reinforced rPP composites for improved performance, offering a sustainable material solution for applications in diverse industries.

Metal material extrusion (MMEX) is a technique to produce a part, characterized by the sequential deposition of material in layers, which is subsequently followed by debinding and sintering to yield fully dense metallic components. The feedstocks, consisting of metal powder combined with a binder system, are essential in determining both the processability and the final attributes of the manufactured parts. In this study, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), contact angle measurement, rheological measurements, printability, and solvent debinding tests were performed for developing a binder system for MMEX of aluminum alloys. Various binder system formulations with polypropylene (PP) as the backbone along with different thermoplastic elastomers (TPEs) as the soluble part were used. During the solvent debinding, two different solvents, cyclohexane and acetone, were evaluated. The results indicated that acetone was ineffective as a solvent for the TPEs used in this study, primarily due to the low solubility of the TPEs in acetone. However, more than 90 vol% of the TPE was removed using cyclohexane as the solvent even at room temperature. Ultimately, the optimized binder formulation for the MMEX process of the aluminum alloys was chosen to consist of polypropylene (PP) as the backbone and thermoplastic elastomer (TPE) soluble in cyclohexane as the primary component. This formulation successfully facilitated all stages of the MMEX process, from shaping to sintering.

In this study, process parameters are presented on how to optimize the novel process for producing anisotropic NdFeB permanent magnets from recycled materials using powder extrusion moulding (PEM). The process is based on the recycling of end-of-life (Eol) magnets that have been processed into powder by the Hydrogen Processing of Magnetic Scrap (HPMS) process. In this study, the influence of melt temperature on the alignment behaviour of magnetic particles during in situ alignment using the PEM process is investigated. This process enabled the fabrication of sintered, anisotropic NdFeB permanent magnets with a high degree of alignment, as indicated by a Br/Js ratio of 0.96. Moreover, the challenges associated with the production of anisotropic NdFeB permanent magnets with PEM are delineated in this study. The primary focus of this study is on the carbon and oxygen content. The study found that sintered magnets with a carbon content of approximately 0.045 wt% could be produced using the PEM process. The oxygen content, however, exhibited a variation depending on the initial material used. Nonetheless, the oxygen content increased by approximately 0.4 wt% from the HPMS powder to the sintered part.

Injection moulding of liquid silicone rubber (LSR) requires reliable computer-aided engineering simulations to support process optimisation, which in turn depend on accurate material data. In this study, thermo-physical and kinetic properties of a highly filled injection moulding (IM) grade of LSR were systematically characterised using complementary experimental approaches, and their impact on simulation fidelity was critically assessed. Specific heat capacity was measured using both modulated DSC and the standard sapphire method, revealing temperature dependence but no intrinsic change during curing, with sapphire-based data incorporating enthalpic effects more realistically for process prediction. Thermal conductivity was found to be nearly constant across the processing temperature range. Curing kinetics were investigated by calorimetry and rheology, with the former supporting an autocatalytic mechanism and the latter suggesting an nth-order model, reflecting differences in detection sensitivity and onset characterisation. When implemented into injection moulding simulations, viscosity primarily affected injection pressures, while differences in specific heat capacity and curing kinetics strongly influenced predicted curing profiles and cycle times. These results emphasise that dataset choice, particularly for curing-related parameters, is critical to achieving predictive accuracy in LSR injection moulding simulations. Unlike previous studies on LSR injection moulding, which typically adapt thermoplastic-inspired characterisation methods without systematically addressing their limitations, this work introduces an organised and comparative methodology to evaluate how different material characterisation techniques influence simulation outcomes. The proposed approach establishes a methodological framework that can guide future research and improve the reliability of process simulations for LSR and other polymeric systems.

In this study, the miscibility challenges and processability of bio-based polylactic acid (PLA)/polybutylene adipate terephthalate (PBAT) blends as a two-component backbone in the binder systems for aluminium (Al) feedstocks in metal material extrusion (MMEX) process were investigated. Differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR), rheological studies, printability and solvent debinding performance were conducted. DSC and FTIR analyses revealed that the interaction between PLA and PBAT is primarily physical, with minor shifts in the crystallization temperature (Tcc) and melting behaviour influenced by the thermoplastic elastomer (TPE) content as the soluble component in the binder system. Rheological studies showed that PLA/PBAT blends with a lower PLA content exhibited better interphase formation and improved flowability, while higher PLA concentrations led to phase separation and reduced homogeneity. Printability tests demonstrated that increasing PLA content enhanced printing and surface quality, with feedstocks containing 25–30 vol.% PLA achieving defect-free printed parts at higher printing speeds of 40–60 mm/s. However, solvent debinding tests using cyclohexane showed that parts with higher PBAT content maintained structural integrity, while higher PLA content led to increased crack formation, particularly in the outer layers. The results suggest that a careful balance of PLA and PBAT is essential for optimizing feedstock properties for MMEX, with formulations containing 15 vol.% PLA and 25 vol.% PBAT as the backbone and capability of increasing the powder loading to 58 vol.% showing the most promising results for both printability and post-processing stability.

The reinforcement of recycled polypropylene with virgin glass fibers is a widely adopted practice to enhance the mechanical properties of recycled materials. Substituting virgin glass fibers with recycled ones from authentic waste streams poses multiple challenges. This article shows a possible solution for reusing two waste fractions that count as outstandingly challenging when trying to reach a high degree of circularity. Composites consisting of a recycled polypropylene matrix derived from Austrian household waste as well as 10, 30, and 50 wt % of two different postindustrial chopped polypropylene-glass fibers (GF-PP) were produced by extrusion in a twin-screw extruder, followed by injection molding. Fiber length measurements were conducted to characterize the quality and heterogeneity of the two input GF-PP waste composites. Subsequently, the performance of these compounds was assessed by investigating their thermal, rheological, morphological, and mechanical properties. The study revealed that the initial formulation and manufacturing method of the chopped GF-PP composite exerted a significant influence on the extent of reinforcement achieved in the recycled polypropylene composites. Despite the same processing principles and parameters, the different types of GF-PP waste composites exhibited significant differences in terms of their rheological and mechanical properties. The trend was also visible when comparing the results across various compound ratios. These compounds also demonstrated acceptable flow behavior and processability. Despite substantial fiber breakage during the compounding and injection molding processes, resulting in an 87-90% reduction in the average fiber length, the produced composites displayed appropriate mechanical properties, which are mostly comparable to virgin glass-fiber-reinforced polypropylene. The findings indicate that by optimizing both the type of postindustrial GF-/PP composites added to recycled polypropylene and the blend ratio, chopped GF-PP can be effectively enhanced and converted into short-fiber-reinforced recycled polypropylene. This process serves as a model for improved recycling practices.

In the last fifteen years, several groups have investigated metal injection moulding (MIM) of NdFeB powder to produce isotropic or anisotropic rare earth magnets of greater geometric complexity than that achieved by the conventional pressing and sintering approach. However, due to the powder’s high affinity for oxygen and carbon uptake, sufficient remanence and coercivity remains difficult. This article presents a novel approach to producing NdFeB magnets from recycled material using Powder Extrusion Moulding (PEM) in a continuous process. The process route uses powder obtained from recycling rare earth magnets through Hydrogen Processing of Magnetic Scrap (HPMS). This article presents the results of tailored powder processing, the production of mouldable feedstock based on a special binder system, and moulding with PEM to produce green and sintered parts. The magnetic properties and microstructures of debinded and sintered samples are presented and discussed, focusing on the influence of filling ratio and challenging processing conditions on interstitial content as well as density and magnetic properties.

Additive Manufacturing (AM) allows the creation of personalized medical models, tools, and implants. Patient-specific structures can be fabricated faithfully, quickly and reliably. The production of orthopedic implants by means of AM could greatly benefit from multi-material structures. The skeletal system is composed of hard bones and softer cartilage, performing different tasks in the body. Multi-material implant structures require biocompatible materials that can withstand in-body conditions for extended periods of time. Among possible material candidates, polyurethanes have been selected for further investigation. This project studied two medical-grade polyurethanes (with established clinical history for long-term implants) produced by DSM Biomedical with a Shore hardness of 75D and 80A. They were used to fabricate three-dimensional structures with the thermoplastic material jetting technique (MJT) known as Arburg Plastic Freeforming (APF). Tensile and bending specimens were produced for the individual polyurethanes by applying optimized processing parameters. Also, multi-material specimens were manufactured to analyze fracture failure at the interface between the two polyurethanes in tension. Based on information collected in this investigation, recommendations on preparing implantable structures such as rib replacement systems, are given.