Modeling of tool blockage condition in cutting tool design for rotary ultrasonic machining of composites

Although superior in properties, composite materials still have problems in machining, such as delamination, cracking, burning, tool blockage, and cost and efficiency issues. These problems can prevent wide application of extraordinary composite materials. As an effective method in composite machining, rotary ultrasonic machining (RUM) process has been paid much attention to recently. The current studies on RUM tool design are mostly based on experiments. However, the insufficiency of RUM tool design theory would generally result in the tool blockage, which subsequently leads to the sharp increase in cutting force and poor machining quality in the engineer application. Besides, few investigations are made to combine tool design parameters with machining conditions to avoid tool blockage during RUM process. In this work, based on the RUM material removal mechanism, two models for the chip space and the chip length are built. Thus, the tool blockage condition in RUM is linked with the tool design parameters and the cutting parameters. Experimental study is performed for theoretical verification. Due to the differences in the modalities of the chip, two typical types of composites, C/SiC and CFRP T700, are selected to obtain their tool blockage conditions. The test results show that to prevent the occurrence of blockage, the chip space should be greater than the chip length in C/SiC milling, while in T700 milling, the chip space should be at least over 8 times greater than the chip length.