Abstract: This paper analyzes in detail the causes of following error from the perspectives of dynamic response and follow-up characteristics of the feed servo system, the relationship between following error and contour error, and the impact on the accuracy of contour machining, and provides specific calculation formulas. Keywords: Feed servo system; Following error; Contour error In continuous cutting machining, to ensure the contour shape accuracy, CNC machine tools require not only high positioning accuracy but also good dynamic response characteristics, enabling them to stably and flexibly follow command signals; that is, the system requires high contour following accuracy. Contour following accuracy is related to the steady-state and dynamic characteristics of the servo drive system. During contour machining, each coordinate axis often needs to start, stop, or change speed instantaneously depending on the machining shape. The control system should simultaneously and accurately control the position and speed of each coordinate axis. Due to the steady-state and dynamic characteristics of the system, the coordinated movement and position accuracy of the coordinate axes are affected, resulting in contour shape error. [Click for details]