Whether the frame is twisted or not is generally judged by measuring the diagonal of the frame. In order to ensure that the axes of the front and rear axles are parallel, the distance between the centers of pin holes of steel plate seats fixed on the frame must be appropriate. If the deformation of the frame is caused by a traffic accident, you can usually see it with your eyes. However, the straightness and verticality of the frame with small bending deformation should be detected by pulling wire, ruler and square ruler. The straightness and verticality of the longitudinal beam affect the strength of the frame and the installation of related components. Straightness can be detected by the drawing method, and the maximum bending of the plane on the frame shall not exceed 5 mm; Verticality can be detected with a square ruler, and the maximum spacing shall not exceed 0.50. The lateral bending of mm longitudinal beam can be detected with a ruler. When the maximum bending exceeds 5mm, J should be corrected. 1 When the longitudinal and transverse beams of the frame are slightly bent locally, a mobile hydraulic press can be used to correct them when assembling the frame. Or adopt the method of locking the two ends with chains and ejecting the middle with jacks for correction, and generally use cold pressure for correction, so as not to affect the mechanical strength of the frame. 6 For hard damage with large bending and difficult to correct by cold pressing, local heating can be assisted, and the heating range should be narrowed as much as possible, and the temperature should not exceed 700? C, and slowly cooling, so as not to increase the brittleness of the material. After the frame is revised? Check the sample nails on the frame to prevent them from rattling during calibration. If the frame has serious special curvature and distortion, it should be leveled, and the longitudinal beam and the transverse beam should be corrected respectively according to the requirements of the model, and then reassembled. What kind of nails can be used to hoe difficult elbows? I can fix it with special butterflies and nails. After inspection, if the frame is bent or twisted beyond the limit, it should be corrected. When the main frame is in good condition} only a few parts are deformed, PJ is directly on the frame and corrected. If the frame is seriously damaged, it should be partially disassembled and corrected. The calibration of 1 frame should be carried out with special tools or on a press, and generally cold-pressing calibration is adopted. If local thermal calibration is adopted, the heating of the frame should not exceed 700? C.