What are the causes of deformation and warping of injection molded products?

The condition of injection molding products deformation, bending, distortion produced mainly because of liquidity position at the time of plastic forming shrinkage is bigger than the vertical position, make the product is different to shrinkage and warp, and because of the injection molding inevitably there are a lot of parts internal residual thermal stress caused by warping, this is all the main performance of the high in situ stress tends to lead to deformation. Therefore, from the source, stamping die decisions the warpage trend of parts, according to the standard of variable forming to prevent this trend is very difficult, the final solution to the difficulties must start from stamping die and improvement. The key to this situation lies in the following aspects:

1. Mold level:

(1) The thickness and quality of the parts should be well-proportioned.

(2) The development of the refrigeration system to make the mold shell concave die each part of the temperature symmetry, pouring system software to make the material flow symmetry to prevent the flow direction, shrinkage is not the same and lead to warpage, moderate font bolding is difficult to form part of the separation channel, popular channel, as far as possible to remove the relative density difference, pressure difference, temperature difference in the concave die.

(3) Thin and thick parts of the junction area and corner to be sufficiently rounded, to have excellent mold, such as improving the mold surplus, improve the mold surface polishing, injection system software to maintain stability.

(4) The exhaust pipe should be excellent.

(5) Improve the thickness of the workpiece or improve the anti warping position, and improve the anti-warping working ability of the workpiece by the rib plate.

(6) The compressive strength of the commonly used raw materials is not enough.

2. Plastic layer:

Crystalline resin than non crystalline resin plastic warping deformation opportunities, and crystalline plastic can be used to reduce the crystallinity with cooling speed, shrinkage of the crystallization process to correct warping deformation.

3. Production and processing level:

(1) If the injection pressure is too high, the pressure test time is too long, and the temperature of wear resistant materials is too low and the rate is too fast, the thermal stress will increase and the warping deformation will occur.

(2) The mold shell temperature is too high, the refrigeration time is too short, using the mold when the parts overtemperature and injection deformation.

(3) Reduce the extruder screw speed ratio and back pressure to reduce the relative density to limit the generation of thermal stress while keeping the minimum amount of charge.