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Fine Grinding of Bioceramics for Knee Implants with Elastically Bonded Abrasives: Process Modeling and Validation
A. Müller, B. Denkena
Institute of Production Engineering and Machine Tools, Leibniz Universität Hannover, An der Universität 2, D-30823 Garbsen, Germany
received June 27, 2014, received in revised form August 1, 2014, accepted September 23, 2014
Vol. 6, No. 1, Pages 31-40 DOI: 10.4416/JCST2014-00024
Abstract
In recent years, there has been steady growth in the application of complex-shaped joint replacement implants and wear-resistant ceramics as implant material. The challenge of implant production remains finishing to an average surface roughness of 20 nm. Tools with elastically bonded diamonds combine grinding and loose abrasive polishing to achieve a high finish with low material removal and thus high shape accuracy – a so-called fine grinding process. This work addresses the working principle of elastic diamond tools in the fine grinding process and the influence of process parameters on the roughness of bioceramics for knee implants. A physical-empirical roughness model based on the number of cutting grains and grain forces was developed and verified as part of the study. The results confirm the hypothesis that the increase of the single-grain force results in the reduction of the surface peaks while taking into account the bond characteristics. For automated use as machine tools for the finishing of all-ceramic implants, continuous wear detection and compensation, by e.g. force controlled polishing, and the temperature stability of the bonds have to be developed.
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Keywords
Biomedical ceramics, processing by polishing and fine grinding, elastic tool, surface topography, knee implant
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