Modeling, Simulation, and Optimization of Machining Polymer Infiltrated Calcium Polyphosphate

Calcium PolyPhosphate (CPP) is a biodegradable inorganic polymer that when formed as a porous structure with interconnected pores of a desired size range holds great potential for certain tissue engineering applications. While possessing desirable characteristics of biocompatibility with acceptable compressive strength, the brittle nature of porous CPPmakes it difficult to machine to desired form from blocks made by sintering CPP powders. To accurately generate anatomically conforming features, conservative material removal rates have been used. In this paper, we investigate the impact of polymer impregnation on the machinability of CPP. The choice of polymer and machining conditions is optimized using Taguchi approach to statistical design of experiments. A cutting force model has been developed for simulation purposes and is validated experimentally. The force model is used to determine peak loading conditions, which are considered in Finite Element studies to ensure that the implant, during machining, does not chip or break. The proposed cutting conditions are validated in rough machining of porous CPP implants (~ 30 volume % porosity) where 8 times reduction in cycle time is achieved over earlier studies, while still producing desired shapes and surface features of excellent quality.