Production of two-material micro-assemblies by two-component powder injection molding and sinter-joining

In the field of micro-technology the production of metallic and ceramic micro-components by powder injection molding (PIM) has become a more and more established fabrication method. But in order to fulfill the demand for more complex-shaped high-precision micro-components further development work has to be performed. This is especially true if more efficient production routes for multi-component-micro-assemblies consisting of different materials or sub-components are envisaged. To meet these challenges, investigations are performed to realize and to establish two primary shape micro-processes. These are two-component micro-injection molding (2C-MicroPIM) and sinter-joining. The realization of these technologies will lead to a markedly reduction of the efforts for handling, adjustment, and assembling of metallic and ceramic micro-assemblies. Furthermore, an increased integration level and functionality can be yielded. For an effective transfer of scientific results to industrial applications the whole process chain must be considered, from development and construction of the tooling as well as of the components to the quality assurance and determination of the properties of the assemblies after sintering. These primary shape processes shall enable the mutual processing of different materials within the fabrication process, so avoiding separate mounting or assembling steps. Additionally fixed and loose junctions between at least two components shall be realized. The progress in research and development will be demonstrated especially by the implementation of shaft-to-collar connections between micro-gearwheels and corresponding shafts. Regarding two-component micro-injection molding, the tool construction for shaft-to-collar connections will be presented as well as first experimental results on the properties of selected ceramic powders and feedstocks for the special requirements of the 2C-MicroPIM process. With the assembly step being performed outside the injection molding tool before sinter-joining different parts and geometries can be combined quite easily. The presented article gives an overview on the concept and on preliminary testing results for the fabrication of a shaft-to-collar-connection. Additionally, a solution for an automated assembly of a shaft and a toothed wheel outside the injection molding tool is presented.     

Replication of LIGA structures using microcasting

Microcasting with a gold base alloy and an Al-bronze as a replication technique for LIGA structures is shown. A LIGA mold insert for injection molding is used to produce PMMA patterns as lost wax models in the microcasting process. Although there are several steps of replication the accuracy of the process is high and allows the fast manufacturing of middle size batches of microstructured parts. The mechanical properties can be varied within a wide range by choosing different casting alloys or cooling rates. Additionally the influence of the investment on the surface roughness is presented as well as results of flowlength tests showing maximal achievable aspect ratios with the gold base alloy and the Al-bronze.The funding of this work within Collaborative Research Center SFB 499 by Deutsche Forschungsgemeinschaft (DFG) is gratefully acknowledged. Thanks also to the colleagues in the SFB 499 for good collaboration, especially to S. Rath for providing special investments for microcasting.     

Signal evaluation for high-speed confocal measurements

The confocal-detection principle is open especially for use in medical applications. For inspection systems applications for technical objects in reflection confocal setups are of growing importance. For such applications the confocal measurements need to have a very short measuring time. A fast detection system is needed and to satisfy this requirement only a small number of height levels are measured and a fast-evaluation algorithm is used. Drawbacks of the reduction of height levels are a greater influence of noise and additional systematic errors on the measured heights. Study the effects of the reduction are calculated, different evaluation algorithms are analyzed, and the optimization of the parameters is discussed.     

Development of a micro annular gear pump by micro powder injection molding

Scaling down devices from the macroscopic world to microsystems presents various problems since tolerances decrease down to the range of the surface roughness. Consequently, the problems assembling such systems increase and any wear has an extreme impact on the function of microsystems. Recently, most microparts are made of thermoplastics or in brittle materials like silicon by deep etching. The mechanical properties of these materials, however, are not favorable for microparts subjected to mechanical wear. To meet the obvious demand for wear resistant microparts made of metals and ceramics, the development of Micro-Metal Injection Molding (Micro-MIM)/Micro-Ceramic Injection Molding (Micro-CIM) was started at Forschungszentrum Karlsruhe a few years ago. The article describes special distinctions between Micro-Powder Injection Molding (-PIM) and normal PIM as well as the arising process variations.However, one has to keep in mind the shrinkage during the PIM-route that makes it very difficult to meet the small tolerances required.In this paper the results of a demonstrator development of a micro annular gear pump and the adaptation for micro ceramic injection molding (Micro-CIM) are reported. For CIM, mold inserts made by LIGA were used. The quality of the molds was evaluated by SEM and micro injection molding in PMMA. Subsequently, Micro-CIM was carried out using zirconia feedstocks. The microparts were separated from the substrate, debound, sintered and surface finished. The surface roughness was evaluated and the processes were optimized.