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.

When the longitudinal and transverse beams of the frame are slightly bent locally, they can be corrected by a mobile hydraulic press when the frame is assembled. 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 wounds with large bending and difficult to correct by cold pressing, local heating can be assisted, the heating range can be narrowed as far as possible, and the temperature should not exceed 700℃, so as not to increase brittleness.

After the frame is calibrated, check the sample nails on the frame to prevent the sample nails from rattling during the calibration. If there are serious special bends and distortions, they should be leveled separately, and the longitudinal and transverse beams should be corrected 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.

Frame calibration should be carried out with special tools or on a press, and generally cold-pressing calibration should be carried out. If local thermal calibration is adopted, the heating of the frame should not exceed 700 C.