Optimization of Machining Parameters on The Geometry Precision of Cortical Screw of Ti-6Al-4V ELI Using Gray Relational Analysis Method

Abstract

Titanium and its alloys have been widely developed in aerospace, biomedical, electronics, sports, and offshore. In the biomedical field, titanium alloy that has been widely used, based on its properties, is biocompatible for bone implants and not becoming a foreign thing in the body. This study aims to optimize to determine the optimal conditions for cutting parameters for the precision of the cortical thread screw geometry referring to the ISO 5835 standard. In this study, the cutting was carried out using a CNC lathe, where the machining parameters used were spindle rotation of 100, 200, and 300 rpm, depth of cut of 0.01, 0.02, and 0.03 mm, and types of lubricants in the form of synthetic oil, virgin palm oil, and virgin coconut oil. Data processing in this study is analyzed using the Gray Relational Analysis Method to get an optimal combination of cutting conditions. The significant factor that influences the precision of cortical thread is the depth of cut, which is a contribution of 98%. It can illustrate that the smaller depth of cut will produce better screw geometry. The optimum conditions for cutting parameters that deliver the best level of precision were obtained at a spindle speed of 100 rpm, depth of cut of 0.01 mm, and type of lubricant of coconut oil. Meanwhile, the screw surface damage is stacked chips as a result of the high temperature generated during the cutting process.