Surface Enhancement of FDM Patterns to be Used in Rapid Investment Casting for Making Medical Implants

Vivek Kumar Tiwary, Arunkumar P., Anand S. Deshpande and Nikhil Rangaswamy
Department of Mechanical Engineering, KLS Gogte Institute of Technology, Belagavi, India


Purpose – Due to intrinsic limitations, fused deposition modelling (FDM) products suffer from the bad surface finish and inaccurate dimensional accuracies restricting its usage in many applications. Hence, there is a need for processing polymer patterns before, during and after their productions. This paper aims to highlight the importance of pre- and post-processing treatments on the FDM-based acrylonitrile butadiene styrene
patterns improving its surface quality so, that it can be used in rapid investment casting process for making medical implants and other high precision components.
Design/methodology/approach – As a part of pre-processing treatment, the machine parameters affecting the surface quality were identified and optimised using design of experiments. The patterns developed after the first stage of optimisation were given different postprocessing treatments, which included vapour smoothening, chemical treatment and sand paper polishing. The results were compared and the best ones were used for making patterns for making medical implants via rapid investment casting technique. The surface quality was checked while the dimensional changes happening during the stages of this hybrid technique were recorded using a three-dimensional optical scanner.
Findings – The surface roughness of the FDM based ABS patterns reduced from 21.63 to 14.40 mm with pre-processing treatments. Chemical treatment (post-processing treatment) turned to be the most suitable technique for reducing the surface roughness further down to 0.30 mm. Medical implants that used these pre- and post-processing treatments gave an average surface roughness of 0.68 mm. Cost and lead time
comparisons showed that rapid investment casting technique can be a better method for low volume, customised and with specific requirements.
Originality/value – FDM parts/medical implants produced by rapid investment casting technique suffer from the inferior surface finish and inaccurate dimensional accuracies limiting its applications. A systematic approach to overcome this issue is presented in this research paper. This will directly help the end users and the manufacturers of medical implants, wherein, better surface finish and dimensionally accurate components are expected.

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