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Papers by Christian Kukla

Applied sciences, Jun 28, 2024

Journal of materials research and technology/Journal of Materials Research and Technology, Feb 1, 2024

Euro PM2023 Proceedings

Material Extrusion with filaments, Fused Filament Fabrication – FFF, is the most widespread addit... more Material Extrusion with filaments, Fused Filament Fabrication – FFF, is the most widespread additive manufacturing technology. This counts mainly for polymers, since the use of this technology for metal and ceramic powders is still in its early days. For several metals, filaments can be bought in the market. Aluminium has a low sintering temperature already in the range of the temperatures for thermal debinding of many feedstocks and needs special sintering regimes. To meet these special requirements, a feedstock for the production of highly filled aluminium filaments was developed. The printed parts are debinded by solvents. Here, the following results are presented: 1) rheological behaviour of the feedstock, 2) debinding behaviour with emphasis on the selection of solvents and 3) printing performance.

Proceedings of the 2nd International Conference on Sensor Networks, 2013

The production of high quality plastic parts requires in-mould sensors to monitor the injection m... more The production of high quality plastic parts requires in-mould sensors to monitor the injection moulding process. A novel wireless sensor concept is presented where structure borne sound is used to transmit information from the inside of an injection mould to the outside surface, eliminating the need for cabling within the mould. The sound is acquired and analyzed using new algebraic basis function techniques to enable the detection of temporal occurrence of frequency patterns in the presence of large levels of noise. The temporal occurrence of the resonators represents the passing melt front. The reduction of spectral leakage is computed by an alternative method using low degree Gram polynomials. The computation of the pattern matching algorithm yields both the correlation coefficients and their covariances which are used to determine the certainty of the measurement. The paper presents the used mathematical background as well as real measurements performed on an injection moulding machine. A test mould was equipped with two different resonant structures. Besides calculating the correlation coefficients the 3σ confidence interval of the coefficients is computed. With the novel algebraic approach a reliable separation of the two temporal points of occurrence of the resonant structures was computed.

Polymers, Sep 2, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Polymers, Nov 16, 2022

Fused filament fabrication (FFF) is a very popular additive manufacturing technique for the produ... more Fused filament fabrication (FFF) is a very popular additive manufacturing technique for the production of geometrically complex polymeric parts. FFF can also be used for the production of sintered magnetic parts, as part of the shaping, debinding and sintering (SDS) process. In order for sintering to be possible, it is recommended to prepare feedstock materials with 50 vol% or more filler content. However, when the filler content increases the properties required for FFF change. In this paper the mechanical properties of filaments, the viscosity of the molten feedstock, and surface properties of the solidified feedstock were investigated as a function of strontium ferrite powder content (53 to 60 vol%). In addition printing trials were performed. It was observed that mechanical properties significantly decrease, the viscosity increases and the surface tension showed no changes as a function of powder loading. All materials were in principle printable, but the printing temperature had to be adjusted to print the most highly filled material due to its lower mechanical properties and higher viscosity.

Over the last ten years several groups have been carrying out research into metal injection mould... more Over the last ten years several groups have been carrying out research into metal injection moulding (MIM) of neodymium-iron-boron (NdFeB) powders to produce isotropic or anisotropic rare earth magnets with higher complexity than in the conventional press and sintering approaches. However, difficult processability due to the high affinity of the powder to oxygen and carbon pickup remains problematic in terms of obtaining sufficient remanence and coercivity. In this paper, a new approach to MIM of NdFeB magnets is presented. It is based on the use of powder obtained from recycling of used rare earth magnets by the hydrogen decrepitation (HD) process. Different types of binder systems have been used for producing mouldable MIM feedstock. Influence of debinding and sintering conditions on interstitial contents and magnetic properties of sintered MIM parts are presented and discussed. Magnets with a remanence of 570 mT, a coercivity of 970 kA/m and an energy product of 57 kJ/m3 could be...

Polymers

The current study presents the effect of the backbone as an important binder component on the mec... more The current study presents the effect of the backbone as an important binder component on the mechanical, rheological, and thermal properties of Aluminium (Al) alloy feedstocks. A thermoplastic elastomer (TPE) main binder component was blended with either polypropylene (PP), grafted-maleic anhydride-PP (PPMA), or grafted-maleic anhydride-PPwax (PPMAwax) plus PP, as the backbone. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) tests were performed to investigate the thermal properties of binder systems and feedstocks. Fourier-transform infrared (FTIR) spectroscopy was used to study the chemical interaction between the binder and the Al alloy. After making feedstock filaments, tensile tests, scanning electron microscopy (SEM), and fused filament fabrication (FFF) printing were done. The results showed that although the PP printability was acceptable, the best mechanical properties and printed quality can be achieved by PPMA. TGA test showed that all binder...

Journal of Materials Engineering and Performance

MAX phase, as a group of layered ternary carbides and nitrides exhibiting combined properties of ... more MAX phase, as a group of layered ternary carbides and nitrides exhibiting combined properties of metallic and ceramic materials, attracts increasing interest because they own exceptionally chemical, physical, electrical, thermal, and mechanical properties. In the present paper, a novel Ti3AlC2-based green part was manufactured by extrusion-based fused filament fabrication (FFF) and 3D printing technologies. The morphology, thermal/electrical conductivity, thermal stability, electromagnetic interference (EMI) shielding effectiveness (SE), and mechanical properties of Ti3AlC2/binder with the volume ratio of 1:1 were investigated. The tensile and compressive strengths and elongation are measured to be 8.29 MPa and 18.20%, 44.90 MPa and 33.76%, respectively. The morphology of the filament reveals that Ti3AlC2 powders are well bonded by the thermoplastic binder. More importantly, the composite shows good thermal and electrical conductivities together with the excellent EMI shielding effe...

Journal of Visualized Experiments

Technical ceramics are widely used for industrial and research applications, as well as for consu... more Technical ceramics are widely used for industrial and research applications, as well as for consumer goods. Today, the demand for complex geometries with diverse customization options and favorable production methods is increasing continuously. With fused filament fabrication (FFF), it is possible to produce large and complex components quickly with high material efficiency. In FFF, a continuous thermoplastic filament is melted in a heated nozzle and deposited below. The computer-controlled print head is moved in order to build up the desired shape layer by layer. Investigations regarding printing of metals or ceramics are increasing more and more in research and industry. This study focuses on additive manufacturing (AM) with a multi-material approach to combine a metal (stainless steel) with a technical ceramic (zirconia: ZrO 2). Combining these materials offers a broad variety of applications due to their different electrical and mechanical properties. The paper shows the main issues in preparation of the material and feedstock, device development, and printing of these composites. Video Link The video component of this article can be found at https://www.jove.com/video/57693/ 12. Three different suspension-based AM techniques are qualified to allow the AM of ceramic-ceramic as well as metalceramic components. The utilization of suspension-based AM techniques promises improved component performance in comparison to powder

IBEREO15 - Challenges in rheology and product development, Nov 30, 2015

Powder injection moulding (PIM) process is well established for production of small precision com... more Powder injection moulding (PIM) process is well established for production of small precision components with both metal and ceramic powders. In comparison to unfilled polymers, the PIM-feedstocks are highly filled multiphase systems, whose flow behaviour is very sensitive to composition of binder and powder loading. Furthermore, the rheology of highly filled multiphase systems is characterized by strain and temperature dependence and influenced by flow instabilities and yield stress. In this study, the rheological behaviour of 316L feedstocks with a polypropylene/wax binder system and different powder loadings was investigated. The experimental work was performed with a rotational and a high pressure capillary rheometer. The aim of this work was to evaluate mixing rules predicting the viscosity of the feedstock out of its composition taking into account the melt temperature rise due to dissipative heating. Hence, measured data were corrected with respect to temperature. Thus the influence of the temperature onto the viscosity and the related model was evaluated.

EURO PM2013, Congress & Exhibition, 2013