The knife-rotating pipe cutter uses the tool to rotate around the periphery of the fixed pipe for ring cutting,and it has been widely used in situations requiring precise cutting of thin-walled pipes.However,its feed path is usually straight or arc,which has the problems of relatively single and flexible cutting cannot be realized.For this reason,a new type of pipe ring cutter was put forward with redundant driving ring cutting mechanism core component,which could move in plane to control the feed of ring cutter.Taking envelope cutting of semicircular pipe as an example,feed trajectory planning was carried out based on 5-6-5-6-5 sectional high order polynomial curve,and a prototype platform was built for simulation and experimental research.The results show that the actual track is consistent with the theoretical track,the cutting process is more flexible and the quality of pipe cut is better,which verifies the rationality of pipe ring cutter structure design and the feasibility of flexible cutting.