Orthogonal Micro-Grooving of Anisotropic Pyrolytic Carbon

Abstract

Pyrolytic carbon (PyC) has excellent biocompatibility, strength-to-weight ratio, and unique directional thermal properties. It finds application in biomedical implants like finger prosthesis, heart valves, and some thermonuclear components. Recently, engineered features have been demonstrated to improve the hemodynamics of heart valves. These features need to be machined on PyC which is a brittle anisotropic material and its machining characteristics are different than standard isotropic materials. Very little work has been done in PyC machining; consequently, this study is aimed at creating the manufacturing knowledge base to generate engineered surfaces in pyrolytic carbon bio-implants. A full factorial experimental design has been used in this article to investigate the effect of micromachining process parameters (rake angle, depth of cut, tool width, and cutting speed) on the response variables. Experiments were conducted in the AB plane (parallel to the layers) and the C plane (normal to the layers) to capture the effect of anisotropy in pyrolytic carbon. The process responses studied were: cutting/thrust forces, surface roughness, surface morphology, and chip morphology. The mean cutting and thrust forces increased by 118% and 88%, respectively, and the surface roughness increased multifold when the cutting plane was changed from AB to C.