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What are the reasons for the deformation of plastic products

Update:30-06-2022
Summary:The shrinkage rate in the flow direction during plastic molding is larger than t...
The shrinkage rate in the flow direction during plastic molding is larger than that in the vertical direction. The plastic processing of automobile injection parts often has the phenomenon of deformation, bending and twisting. What are the main reasons for the deformation of plastic products?
1. Mould:
(1) The thickness and quality of the parts should be uniform.
(2) The design of the cooling system should make the temperature of each part of the mold cavity uniform, and the gating system should make the material flow symmetrical to avoid warpage caused by different flow directions and shrinkage rates. Main flow channel, try to eliminate the density difference, pressure difference and temperature difference in the cavity.
(3) The transition area and corners of the thickness of the part should be smooth enough, and have good demolding properties, such as increasing the demoulding allowance, improving the polishing of the die surface, and maintaining a balance in the ejection system.
(4) The exhaust should be good.
(5) Increase the wall thickness of the workpiece or increase the warpage resistance direction, and the warpage resistance of the workpiece is enhanced by the reinforcing ribs.
(6) The strength of the material used in the plastic mold is insufficient.
      2. In terms of plastics: crystalline plastics have more warpage deformation opportunities than amorphous plastics. In addition, crystalline plastics can use the crystallization process that the crystallinity decreases with the increase of the cooling rate and the shrinkage rate decreases to correct the deformation.
3. Processing:
(1) The injection pressure is too high, the pressure holding time is too long, and the melt temperature is too low and the speed is too fast, which will cause the internal stress to increase and warp deformation to occur.
(2) The temperature of the plastic mold is too high and the cooling time is too short, which makes the part overheated during demolding and ejection deformation occurs.
(3) Reduce the screw speed and back pressure to reduce the density to limit the generation of internal stress while maintaining the minimum charging amount.
(4) When necessary, the factory can softly shape the easily deformed parts or carry out the de-rice treatment after demoulding.
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