Evaluation of various milling strategies in supporting advanced CAD/CAM environment for biomedical applications

Abstract

The purpose of this study is to simulate various types of milling strategies for knee implant that provides the shortest machining time with integration of conceptual algorithm based on high level data structure known as STEP-NC. STEP-NC, an acronym for Standard for the Exchange of Product Model Data for Numerical Control is developed by the ISO committee with the intention of replacing the outdated G-codes used for machine execution. STEP-NC may provide comprehensive information such as material properties, part feature, the best machining time on cutting strategies and working step for the process. In this study, three cutting strategies such as Spiral, Helical and Concentricused in roughing and strategies of multi axis sweeping with tool axis mode Lead and Tilt, Thru a guide and Normal to Surfaceused in finishing process were simulated using traditional CAD/CAM environment using CATIA V5R19to analyze the shortest machining time in machining a knee implant model. The constant parameters were Feed/tooth 0.01 mm, Cutting Speed 40 m/min and Tool Diameter 10 mm while variable include Depth of cut 2mm and 3mm, Tooth Path Styles Spiral, Helical and Concetric and tool path overlap 50% and 75% for roughing process. While for finishing process, the constant parameters were Feed/tooh 0.01 mm, Cutting Speed 60 m/min, Depth of cut 0.2 mm and Tool Diameter 6mm Bull Nose while variable include multi axis sweeping with tool axis mode Lead and Tilt, Thru a guide and Normal to surface. From the simulation results, it was found that the best machining time is helical strategy for roughing process completed at 4 hours 23 minutes and 27 seconds and tool axis mode with lead and tilt for finishing process at 4 hours 7 minutes and 5 seconds as compared to others having a machining time of more than 4 hours 24 minutes and 26 seconds. In supporting the development STEP-NC standard, a conceptual algorithm model to portray an advanced CAD/CAM environment was proposed. The conceptual model may assist process planners to assign appropriate machining strategies where the interface may suggest a suitable tool path with the shortest machining time for complex features. In conclusion, various machining strategies can be evaluated with respect to various input parameters in giving a shortest machining time with better accuracy results.