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

Abstract

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 (μ-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.