There is a xk2116 CNC gantry boring and milling machine in the equipment workshop of a heavy-duty automobile Co., Ltd., which is the product of a heavy-duty machine tool factory in Wuhan in 1993 and has been running for more than 20 years. At present, the measurement result of the total length positioning accuracy of the x-axis of the machine tool workbench is 0.5, and the positioning accuracy P1000 required by the machine tool certificate is less than 0.035, which has seriously exceeded the tolerance.