The Semi-automatic CMM can be defined as "a detector that can move in three directions and can move on three mutually perpendicular guide rails. The detector transmits signals in contact or non-contact, and the displacement measurement of the three axes The system (such as grating ruler) calculates each point (x, y, z) of the workpiece and the instrument for measuring various functions through a data processor or computer. The measurement function of the three-coordinate measuring instrument should include dimensional accuracy, positioning accuracy, geometric accuracy and contour accuracy, etc.