Tobias Mueller

Manufacturing of High-Grade Micro Components by Powder Injection Molding

Powder injection molding (MicroPIM) has a considerable potential for the production of high-value metal and ceramic micro components. This does not only apply to technical aspects but, due to the deployability of mass production, also to economic ones. The current status can be summed up by the following key data: latest trials revealed smallest struc-tural details in the 10µm range or lower. Theoretical densities of up to 99% were achieved depend-ing on the particular powder applied. Typical materials processed are metals (Fe, Cu, 316L, 17-4PH, W and W-alloys etc.) or ceramics (aluminum/zirconium oxide etc.). Best surface qualities were obtained with ultrafine or even nano-doped ceramic powders. Another major line of development is multi-component or assembly injection molding. These proc-esses do not only reduce assembly expenditure, but also allow for the use of new functional material combinations. Interesting examples are ceramic micro heating elements or gear wheel/shaft samples which can be performed as fixed or movable combinations. Micro inmold-labelling using PIM feed-stocks offers further promising opportunities.

Replication of Overmolded Orthopedic Implants with a Functionalized Thin Layer of Biodegradable Polymer

The present paper reports on the development of a biodegradable overmolded orthopedic implant: a metal bone fixing screw, which has been overmolded with a functionalized thin layer of biodegradable polymer to enhance cell adhesion during the healing process. The main challenges were to integrate precise, high-throughput and repeatable solutions to achieve a thin, defect-free structured polymer layer and to ensure a high and consistent implant quality. The work carried out entailed determining proper materials (Purasorb PDLG 5010) for the biodegradable overmolding layer and its economical substitute (NaKu PLA 100HF) to be used during initial tool and process development, designing the surface structure of the overmolded polymer layer, development of injection molding tools, as well as feeding and handling procedures. The injection overmolding process of Purasorb PDLG 5010 polymer was controlled, and the process parameters were optimized. In particular, the dominant process parameters for the overmolding, namely injection pressure, barrel temperature and mold temperature, were experimentally examined using a circumscribed three-factor central composite design and two quality marks; overmolding roughness and mass of polymer. The analysis of the experimental results shows that the mass of the overmolding is not feasible for use as the quality mark. However, the optimal parameters for the overmolding of a metallic implant screw with a thin, micro-structured polymer layer with a predefined roughness of the surface texture have been identified successfully.

Fused Deposition Modeling of ABS-Barium Titanate Composites: A Simple Route towards Tailored Dielectric Devices

A process for the development, characterization and correlation of composite materials for 3D printing is presented, alongside the processing of a polymer-ceramic functional composite using fused deposition modeling (FDM). The composite was developed using acrylonitrile butadiene styrene (ABS) as the matrix material filled with barium titanate (BT) micro-powder up to 35 vol % (74.2 wt %). The ABS-BT composites exhibited a shear thinning behavior with increasing ceramic content. The composite was 3D printed into structural and functional test samples using FDM by adapting and optimizing the print parameters. Structural characterization revealed increasingly brittle behavior at higher filler ratios, with the ultimate tensile strength falling from 25.5 MPa for pure ABS to 13.7 MPa for the ABS-35 vol % BT composite. Four-point flexural tests showed a similar decrease in flexural strength with increasing ceramic content. Functional characterization revealed an increase in the relative permittivity at 200 kHz from 3.08 for pure ABS to 11.5 for the composite with 35 vol % BT. These results were correlated with the Maxwell-Garnett and Jayasundere-Smith effective medium models. The process described in this work can be used for other 3D printing processes and provides a framework for the rapid prototyping of functional composites into functional parts with reliable properties. The ABS-BT composite shows promise as a functional dielectric material, with potential applications as capacitors and light-weight passive antennas.

Micro systems need a boost in manufacturing methodologies

While macroscopic powder injection moulding is drawing the attention of mass manufacturing and winning plaudits for its high process and economic efficiency, its micro variant still faces challenges…