Abstract: In the process of tool radius compensation in CNC systems, interference between the tool and the contour must be avoided. Using vector analysis, based on different transition patterns of tool radius compensation in the plane, the relationship between the vector of the actual contour of the part and the vector of the tool trajectory after radius compensation is analyzed, and a method for checking tool radius compensation interference is summarized. This method, when applied to CNC systems, can effectively check the interference caused by tool radius compensation. Keywords: Tool radius compensation, interference 1. Generation of Interference Due to the uncertainty and complexity of the contour of the machined part, when the tool radius is too large or encounters an inner sharp corner of the contour, if the tool trajectory at the contour transition is not handled properly, the phenomenon of tool overcutting the contour will occur (Figure 1). This is tool interference. Tool interference can cause damage to the part and must be overcome. Contour interference inspection is divided into two cases: two-segment contour interference inspection and multi-segment contour interference inspection. Two-segment contour interference inspection only checks the interference of two adjacent contour segments participating in tool compensation, without considering the interference of other contour segments. Inspection considering other contour segments is called multi-segment contour interference inspection (Figure 1b). Under normal circumstances, a good interference check on two contour segments is sufficient to meet the requirements of interference testing. Therefore, this paper only considers the interference check of two contour segments. Currently, there are some methods to check for tool interference, but the judgment conditions are too cumbersome. This paper derives an effective algorithm for judging tool interference by judging the contour transition type and combining the changes in the direction vectors before and after contour compensation. [Click for details]