Dimensional accuracy and surface finish of biomedical implant fabricated as rapid investment casting for small to medium quantity production

In this work the feasibility of combined route of fused deposition modelling (FDM), chemical vapor smoothing (CVS), vacuum casting (VC) and investment Casting (IC) for the development of customized implant for small to medium quantity production has been investigated. Further, an effort has been made to optimize the dimensional accuracy and surface finish of the implant (hip joint) prepared by varying two controllable factors (namely: drying time of primary coating and mould thickness) each at three levels of the IC process. The master pattern of the hip joint has been prepared by FDM followed by the CVS process to enhance the surface finish and multiple replicas were produced by the VC process for batch production. The tolerance grades for the selected dimension of the implant/castings were found to be acceptable as per the ISO standard UNI EN 20286-I (1995). Also, the Cpk value greater than 1.3 indicated that the proposed process is statistically controlled.