Improvement of boring quality of CFRP and evaluation of tool wear by inclined planetary milling

Abstract

In recent years, CFRP is widely used as an alternative structural material to improve fuel consumption with high strength and light weight comparing to conventional aluminum alloy.CFRP is also expected to be the structural material for next generation automobiles - especially electric vehicles - in order improve fuel and/or electric power efficiency. However, CFRP is categorized as one of the difficult-to-cut material and burrs and delamination could occur with conventional drilling and cutting ways due to their severe cutting tool wear. For above mentioned reasons, in order to improve the machinability of CFRP drilling situations, the authors have proposed the inclined planetary milling process as a novel high quality boring technique for CFRP.According to our past experiments, the effectiveness for reduction of burrs and delamination of CFRP boring by the inclined planetary milling has been demonstrated. However, demands for higher speed and wear resistance of cutting tools are rising in the industrial field. The objective of the study is to achieve shorter processing time of CFRP boring and reduction of tool wear with maintaining high bore quality. The authors have carried a set of experiments for evaluating the relationship between feed rate variations and bore quality transition. The workpiece materials were unidirectional and fabric CFRP stack plates and the cutting tool shape was corner radius end-mill. From the experimental results, it was confirmed that the feed rate per one cutting edge strongly affected the generation of cross-sectional profile of the bore. This was also theoretically confirmed by our developed kinematic cutting model of the inclined planetary milling theoretically.In the article, the optimal cutting conditions of the inclined planetary milling for CFRP boring and factorial effect of feed rate to the bore quality are reported.