The occurrence of deformation, bending and distortion of injection molded products is mainly due to the fact that the shrinkage rate of the flow direction is larger than that in the vertical direction during plastic molding, so that the shrinkage rate of the workpiece is different and warped, and because of the warping caused by the inevitable residual large internal stress in the workpiece during injection filling, which is the deformation caused by the high stress orientation. Therefore, fundamentally speaking, the mold design determines the warpage tendency of the workpiece, and it is very difficult to suppress this tendency by changing the molding conditions, and the final solution must be solved by the mold design and improvement. This phenomenon is mainly caused by the following aspects:

1. Mold aspect:

(1) The thickness and quality of the workpiece should be uniform.
(2) The design of the cooling system should make the temperature of all parts of the mold cavity uniform, the gating system should make the material flow symmetrical to avoid warping caused by different flow directions and shrinkage, appropriately thicken the sub-runners and sprue of the parts that are more difficult to form, and try to eliminate the density difference, pressure difference and temperature difference in the cavity.
(3) The transition area and corner of the thickness of the workpiece should be smooth enough, and there should be good demoulding, such as increasing the demoulding margin, improving the polishing of the die surface, and maintaining the balance of the ejection system.
(4) The exhaust should be good.
(5) Increase the wall thickness of the workpiece or increase the anti-warping direction, and enhance the anti-warping ability of the workpiece by reinforcing ribs.
(6) The strength of the material used in the mold is insufficient.

2. Plastics:

Crystalline plastics have more opportunities for warpage deformation than amorphous plastics, and crystalline plastics can be corrected by using a crystallization process in which the crystallinity decreases with the increase of cooling rate and the shrinkage rate decreases.

3. Processing:

(1) The injection pressure is too high, the holding time is too long, and the melting temperature is too low and the speed is too fast, which will cause the internal stress to increase and warp deformation.
(2) The mold temperature is too high and the cooling time is too short, so that the workpiece during demoulding is overheated and the ejection deformation occurs.
(3) Reduce the screw speed and back pressure while maintaining a minimum charge to limit the generation of internal stress.
(4) If necessary, the parts that are easy to warp and deform can be softly shaped or removed from the mold.