Dietmar Drummer

• Prof. Dr.-Ing.
• Head of Department at Friedrich-Alexander-University Erlangen-Nürnberg

A major challenge in the powder bed fusion (PBF) process with polyamides, which are the most commonly used powders, is the handling of already used powder (aged powder). During PBF, polyamide powders undergo chemical ageing, resulting in altered thermal and rheological properties of the feedstock material. Components made from aged powder are of in...

Laser-based powder bed fusion of polymers (PBF-LB/P) is a layer-based additive manufacturing (AM) method that produces functional components with superior mechanical properties. However, the limitation of commercially available materials, primarily polyamides, reduces the range of applications for PBF-LB/P processed parts. The use of novel polymer...

This chapter briefly describes the field of Additive Manufacturing, its benefits, and its applications. Furthermore, the used processes are introduced and explained.

Since the laser based powder bed fusion of polymers process involves previously unknown boundary conditions, process-adapted powder characterization at the particle and powder layer levels is essential. In this chapter, new measurement methods are presented, and the results are discussed within the context of process-adapted boundary conditions for...

This chapter investigates the effects of thermal and temporal influences on the resulting part properties, particularly the temperature profile in the powder bed fusion process with a laser beam for polymers (PBF-LB/P). Through detailed process analysis, new strategies have been developed to increase the robustness of the process, control thermal h...

Multiphase systems are material systems consisting of at least two components. This can be a material system with two polymers (blend production) or a polymer with fillers. The use of multipolymer material systems aims to improve properties through synergistic effects, for example, ‘positive’ material properties of both polymers mixed together shou...

This study investigates the incorporation of an intumescent flame-retardant system, based on a intumescent combination of ammonium polyphosphate (APP) and pentaerythritol (PER), into polyamide 12 (PA12) for selective laser sintering (SLS). The influence of processing parameters and filler content on the mechanical and fire properties of the manufac...

Ultra-high molecular weight polyethylene (UHMW-PE) fibers and bacterial nanocellulose (BNC) display exceptional mechanical properties alongside the outstanding tribological properties of UHMW-PE while showing unrestricted biocompatibility. For combining the intrinsic advantages of both materials, the present work demonstrates an approach that integ...

Flame‐retardant properties of polymer components are essential to a broad variety of applications. However, the processing of flame‐retardant thermoplastics in laser‐based powder bed fusion remains challenging. To overcome prevailing limitations, a new polyphosphate‐based intumescent flame‐retardant system for polyamide 12 (PA12) based powder bed f...

Powder bed fusion processes are among today’s few industrially established additive manufacturing processes. Present power bed fusion process strategies either focus on the application of elevated powder bed temperatures, found in the quasi-isothermal processing of semi-crystalline polymers, or the use of support structures, prevailing in the manuf...

Additively manufactured polyolefins find broad applications in medical engineering, enabling the manufacturing of patient‐specific geometries. For investigating the influence of processing conditions of laser sintered locally macroporous polypropylene substrates, the response of myoblasts, chondrocytes, and fibroblasts has been characterized in thi...

Several application possibilities exist in terms of polymer-bonded magnets, such as the sensors or smaller motors, for example, in the window operators of cars. Increasing demand and rising environmental awareness necessitate a higher understanding in terms of the possible recycling strategies for polymer-bonded magnets, especially in the context o...

There is an urgent need to enhance the mechanical and biotribological performance of polymeric materials utilized in biomedical devices such as load‐bearing artificial joints, notably ultrahigh molecular weight polyethylene (UHMWPE). While two‐dimensional (2D) materials like graphene, graphene oxide (GO), reduced GO, or hexagonal boron nitride (h‐B...

The changing demands in terms of the compactness and performance of electronic devices increase the role of thermal management within this application field. Because polymers and especially thermosets have a low thermal conductivity, filler systems have to be used to improve their performance and make thermosets suitable for applications. So far, s...

The powder-based additive manufacturing of high-melting polyamides is impeded by unfavorable fracture properties and oxidation tendencies, limiting the technical applicability and the reuse of unfused powder. Overcoming these limitations through new processing strategies provides the opportunity for significantly extending the range of materials ap...

Ultra-high molecular weight polyethylene (PE-UHMW) fibers and bacterial nanocellulose (BNC) fibers both display exceptional mechanical properties alongside the outstanding tribological properties of PE-UHMW while showing an unrestricted biocompatibility. For combining the intrinsic advantages of both materials, the present work demonstrates an appr...

Filament-based material extrusion (MEX) represents one of the most commonly used additive manufacturing techniques for polymer materials. In a special variation of this process, highly filled polymer filaments are used to create metal parts via a multi-step process. The challenges associated with creating a dense final part are versatile due to the...

Polymer-bonded magnets are increasingly being used in terms of applications in drive technology and, more specifically, in new concepts based on reluctance motors. The increasing demand for polymer-bonded magnets, especially in the context of electromobility, is leading to a shortage of materials, mainly in terms of the finite resource neodymium–ir...

Objectives / Introduction: The experimental investigation of the flow-structure coupling represents a significant challenge in otolaryngology/phoniatrics, which is often performed with human and animal-derived specimens showing a rapid degradation of relevant mechanical and dynamic properties. The synthetic, elastomer-based replication of larynge...

Rotational molding allows the manufacturing of geometrically complex, hollow parts while maintaining low tool costs. While the rotational molding of thermoplastics is subject to inherent limitations regarding the wall thickness and processing of ultrasoft materials, the present paper introduces the adhesion‐controlled, highly dynamic rotational mol...

Multipolar bonded magnets based on a thermoset matrix provide the opportunity to expand the applications of bonded magnets, especially within the drive technology industry, in terms of the high thermal and chemical resistance, along with a higher utilisation of the magnetic potential. To realize the application of polymer bonded magnets based on th...

With increasing demands for data transfer, the production of components with low dielectric loss is crucial for the development of advanced antennas, which are needed to meet the requirements of next-generation communication technologies. This study investigates the impact of a variation in energy density on the part properties of a low-loss cyclic...

Currently, polyamides serve as the primary material used in laser-based powder bed fusion of polymers (PBF-LB/P), which prevents the components from exhibiting the mechanical characteristics of traditional manufacturing techniques. As a result, highly ductile and chemical-resistant materials are needed to cover more potential application areas. The...

The additive manufacturing of metals by material extrusion in a multi-step process (MEX-MSt/M) represents a special process variant of the commonly used material extrusion (MEX) and is based on the processing of highly filled polymer filaments. This technology uses the geometrical freedom and fast processing given by MEX to create individual metal...

Laser-based powder bed fusion (LPBF) of semi-crystalline polymers enables the support-free layer-wise manufacturing of geometrically diverse, complex components. In contrast to the established quasi-isothermal powder bed fusion of polymers at elevated temperatures, non-isothermal, cold processing strategies allow to significantly extend the range o...

Herein, we demonstrate the preparation of magnetic polyamide 11 feedstock powders for powder bed fusion (PBF) using liquid-liquid phase separation and crystallization. By adding magnetic nanomaterials during the precipitation process, the particulate additive is incorporated into the polymer matrix. This enables the production of filled systems at...

Hybrid components consisting of continuous fiber reinforced thermoplastic (CFRT) and steel components exhibit promising potential in advanced lightweight construction. However, the joining operation presents a significant challenge due to the materials’ distinct physical and chemical properties. This paper studies a joining method in which dual pin...

With the development of integrated circuits and the miniaturization/ integration of electronic devices, heat dissipation solutions have become an increasingly important issue. The thermal conductivity of polymer-based thermal management materials is typically influenced by the amount of incorporated fillers. However, an innovative solution to incre...

The applications of polymer-bonded magnets are increasing within drive technology mostly because of new concepts concerning the magnetic excitation of direct current (DC) or synchronous machines. To satisfy this rising demand for hard magnetic filler particles—mainly rare earth materials—in polymer-bonded magnets, a recycling strategy for thermopla...

Non-isothermal laser-based powder bed fusion of polymers (PBF-LB/P) allows for the support-free additive manufacturing of semi-crystalline polymers at room temperature. The present paper demonstrates the support-free manufacturing of polypropylene, enabled through discretized exposure strategies, constituting fundamentally different processing cond...

The chemical reduction method is a simple and popular way to contrast the graphene network to improve the polymer matrix's thermal conductivity. And hybrid thermal conductive fillers composed of two or more mixed fillers through chemical synthesis usually have better thermal conductivity because of the synergistic effort. In this work, silicon carb...

With this study, correlations in the structuring step of pin-like joining were derived. Increased friction energy due to higher amplitude or force leads to a reduction in structuring time. Changes in thermo-mechanical properties for humid specimens result in increased process times. The theoretical geometry of the pin-like structures is well reprod...

A synergistic multi-material flame retardant system based on expandable graphite (EG), aluminum diethylphosphinate (AlPi), melamine polyphosphate (MPP), and montmorillonite (MMT) has been studied in glass-fiber-reinforced polyamide 6 (PA6). Analytical evaluations and fire performances were evaluated using coupled thermogravimetric analysis (TGA) an...

Due to its chemical structure and the resulting dielectric properties, the processing of the commonly used particle foam material, expanded polypropylene (ePP), is limited. Processing within the radio-frequency welding process is therefore only possible with the use of processing aids. In this paper, a new approach for the use of a solid and dielec...

Laser-based powder bed fusion of polymers (PBF-LB/P) is predominantly based on the quasi-isothermal processing of semi-crystalline polymers. To overcome existing limitations in the range of polymers suitable for PBF-LB/P, the non-isothermal, support-free powder bed fusion of polymers by means of superposed fractal, phase-shifted exposure strategies...

Laser based powder bed fusion of Polymers is an additive manufacturing technology that meets requirements of established manufacturing processes; thus, it is essential to expand the original range of applications from prototype generation to functional components. Semi-crystalline materials, mainly polyamide 12 (PA 12), dominate the market. Prior t...

Laser powder bed fusion of polymers (LPBF) is a promising additive manufacturing technology that allows for the generation of complexly shaped parts with high mechanical properties. However, enhancing the reproducibility of part properties is one of the main challenges on the technologies way to industrialization. Therefore, the process has to be r...

Additive manufacturing technologies represent the disruptive technologies of this century, since they offer an unprecedented degree of geometrical freedom, material diversity and functionalizability. As no tools are required, these components can be provided within a short period of time. Especially with respect to emerging medical applications, th...

The demand for polymer composite solutions in bipolar plates for polymer electrolyte membrane fuel cells (PEMFCs) has risen due to advantages over metal plates such as longer lifetime, weight reduction, corrosion resistance, flexible manufacturing, freedom of design, and cost-effectiveness. The challenge with polymer composites is achieving both su...

Synthetic silicone larynx models are essential for understanding the biomechanics of physiological and pathological vocal fold vibrations. The aim of this study is to investigate the effects of artificial ligament fibers on vocal fold vibrations in a synthetic larynx model, which is capable of replicating physiological laryngeal functions such as e...

An in situ gear test rig has been developed at the Institute of Polymer Technology (LKT) to characterize the deformation of plastic gears during operation. It analyses timing differences between following index pulses of rotary encoders on the input and output shaft. This measurement principle enables the continuous measurement of the elastic tooth...

The filling behavior of electrodeposited microcolumns is strongly influenced by the mass transfer characteristics at the cathode/electrolyte interface. This study aims to elucidate the influence of the mass transfer characteristics (ion supplementation via diffusion and ion consumption via deposition) on the electrodeposition of microcolumns, thus...

Multipolar bonded magnets based on thermosets offer the opportunity to expand the applications of bonded magnets with respect to an increasing chemical and thermal resistance compared to thermoplastics. To utilise this option, the correlation between the material system and the magnetic properties must be explored amongst other influencing factors....

The void defect inside the electroformed nickel microcolumns is a common problem affecting the performance of the microsystem. In this study, a simulation model for the dynamic deposition of microcolumns is set up to clarify the changing characteristics of ion mass transfer and electric field distribution inside the microcavities under the electrof...

Lightweight design in the form of intelligent multi-material structures that combine the advantages of high strength steel and continuous fibre reinforced thermoplastics (CFRTs) gain increasing relevance. In this context, the joining operation is a major challenge as it has to be time and cost efficient and the resulting joint has to exhibit a high...

With the development of integrated circuits, the miniaturization and integration of electronic devices has become a development trend, and the demand for heat dissipation is also increasing. Graphene three‐dimensional aerogels prepared from graphene has been widely used in the field of thermal management materials, but graphene aerogels also face t...

In this second part of our survey on experimental research in Synthetic Molecular Communication (SMC), we review works on long-range SMC systems, i.e., systems with communication ranges of more than a few millimeters. Despite the importance of experimental research for the evolution of SMC towards a mature communication paradigm that will eventuall...

Since its emergence from the communication engineering community around one and a half decades ago, the field of Synthetic Molecular Communication (SMC) has experienced continued growth, both in the number of technical contributions from a vibrant community and in terms of research funding. Throughout this process, the vision of SMC as a novel, rev...

The pulse current electrodeposition has proved to be effective in the preparation of metal films with a low residual stress, while the formation mechanism of residual stress under the pulse current remains unclear. In this study, in situ measurements of residual stress in electrodeposited nickel films was performed. Nickel films with the lowest ave...

To develop new areas of application for laser-based powder bed fusion of polymers (PBF-LB/P), a deeper process understanding of the resulting mechanical properties, particularly for thin-walled and complex structures, is needed. This work addresses the influence of part thickness and orientation in detail. For a general understanding, two PBF syste...

X-ray-computed tomography (CT) is today’s gold standard for the non-destructive evaluation of internal component defects such as cracks and porosity. Using automated standardized evaluation algorithms, an analysis can be performed without knowledge of the shape, location, or size of the defects. Both the measurement and the evaluation are based on...

A persistent problem in laser powder bed fusion (PBF) additive manufacturing (AM) of polymers is the accumulation of used feedstock material that cannot be reprocessed due to alterations in the physical and chemical structure upon ageing at elevated temperatures. The chemical ageing of polyamide 12, the most frequently used feedstock in PBF of poly...

An increased awareness of sustainability among the population leads, from an industrial point of view, to efforts to act more ecologically as well as to the aim for lower production costs and an increased efficiency. With this in mind, a new process has been developed for foaming without blowing agents in rotational molding. Process related air inc...

Laser sintering (LS) enables cost-effective production of small batches as well as complex functional integration due to the direct build-up process without the need for specific tools. Further, geometrical restrictions are non-existent or only very limited. The combination of LS components with series components, for example, from injection moldin...

Within this contribution, the incorporation of nanoparticles (SiO2, Al2O3, TiO2) into the matrix of precipitated polyamide particles during thermally induced phase separation (TIPS) is demonstrated. The obtained polymer composite powders are tailored for their application in powder bed fusion (PBF). The flexible process allows to tune and adapt the...

A new steel–plastic gear set testing methodology has been developed at the Institute of Polymer Technology (LKT). The in situ gear test rig analyses the timing differences between the index pulses of rotary encoders on the input and output shaft. This measurement principle enables the continuous measurement of the elastic tooth deflection on the on...

Continuous fiber-reinforced thermoplastics (CFRTs) can in combination with high-strength metals offer characteristics that cannot be achieved with mono-material parts. One possible example is the combination of locally high-temperature resistance in the metal component with superior weight-related mechanical properties due to the CFRT component. Th...

It is of great significance to study new thermal conductivity filler in practical thermal management application. In this study, a multi‐scale assembled thermal conductivity composite Al2O3‐ZnO NWs/GO/EP was developed. The test results showed that the composite has good thermal conductivity and mechanical properties with low filler content. When th...

To expand the range of applications of multipolar bonded magnets based on a thermoplastic matrix, the chemical and thermal resistance has to be increased and the reduced orientation in the rapid solidified surface layer has to be overcome. To meet these requirements, the matrix of multipolar bonded magnets can be based on thermosets. This paper inv...

Additive manufacturing of material systems sensitive to heat degradation represents an essential prerequisite for the integration of novel functionalized material systems in medical applications, such as the hybrid processing of high-performance thermoplastics and gelling polymers. For enabling an inherent process stability under non-isothermal con...

Laser-based powder bed fusion (LPBF) of polymers allows for the additive manufacturing of dense components with high mechanical properties. Due to inherent limitations of present material systems suitable for LPBF of polymers and required high processing temperatures, the present paper investigates the in situ modification of material systems using...

In this work, the influence of gate design and mould temperature on the mechanical and tribological characteristics of a polyamide-steel gear set is investigated. Of special interest is the interaction of gate design and processing parameters, in this case the mould temperature, on the resulting properties of the polymer wheel. At 60 °C mould tempe...

Due to the confined mass transfer capability in microchannels, void defects are easily formed in electroformed microcolumn arrays with a high depth/width ratio, which seriously affects the life and performance of micro-devices. The width of the microchannel constantly decreases during electrodeposition, which further deteriorates the mass transfer...

The expanding demand for electro mobility in general and specifically for electrified vehicles requires the expansion of electro mobility technology with respect to variations in the requirements of the process and the application. Within the stator, the electrical insulation system has a high impact on the application properties. So far, limitatio...

Non-isothermal laser-based powder bed fusion (LPBF) of polymers suggests the potential for significantly extending the range of materials applicable for powder-based additive manufacturing of polymers, relying on the absence of a material-specific processing window. To allow for the support-free manufacturing of polymers at a build chamber temperat...

Since its emergence from the communication engineering community around one and a half decades ago, the field of Synthetic Molecular Communication (SMC) has experienced continued growth, both in the number of technical contributions from a vibrant community and in terms of research funding. Throughout this process, the vision of SMC as a novel, rev...

In this second part of our survey on experimental research in Synthetic Molecular Communication (SMC), we review works on long-range SMC systems, i.e., systems with communication ranges of more than a few millimeters. Despite the importance of experimental research for the evolution of SMC towards a mature communication paradigm that will eventuall...

With the recent great interest in microfluidic devices, a better understanding of preconcentration technology has become increasingly important. Herein, concentration enrichment of charged samples is achieved by using field-amplified sample stacking (FASS) technology in the microchannel. This paper aims to develop a fundamental understanding of FAS...

Foreword The International Conference on Gears in Garching near Munich, Germany, is an established platform for researchers on and manufacturers of gears and transmission systems. At the 10th issue of the conference in September of 2023, gear experts discussed the latest developments and research results from the powertrain industry and academia. G...

Due to the increasing demand for electro mobility and specifically for electrified vehicles, the demand for electric drive technology is expanding significantly with changing requirements in terms of the process and the application. The electrical insulation system of the stator is an essential part of the fabrication process with a high impact on...

The wear behaviour of PBT-steel gear sets under temporarily changed load has been investigated using an in situ gear test rig developed at the LKT. The in situ test method is based on analysing the timing differences between the index pulses of rotary encoders on the input and output shaft of the test rig. The loading torque was varied between two...

The direct encapsulation of electronic components is an effective way of protecting components against external influences. In addition to achieving a sufficient protective effect, there are two other big challenges for satisfying the increasing demand for encapsulated circuit boards. The encapsulation process should be both suitable for mass produ...

Friction and wear in a tribological system are directly dependent on the surface structure and roughness of the friction partners involved. In this article, a clear interaction between surface topologies and their roughness depth was identified for the material pairing polyamide 66 – steel. The typical correlation between roughness and wear, initia...