For the same mold and the same batch of products, POM material is not reinforced. Why is it finally found that the shrinkage of black is much larger than that of white?

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1.Mould aspect:
(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 pouring system should make the material flow symmetrical to avoid warping due to different flow directions and shrinkage rates, and appropriately thicken the runners and mainstreams of the difficult-to-form parts. Road, try to eliminate the density difference, pressure difference, and temperature difference in the cavity.
(3) The transition zone and corners of the thickness of the part should be smooth enough and have good mold release. For example, increase the mold release margin, improve the polishing of the mold surface, and maintain the balance of the ejection system.
(4) Good exhaust.
(5) Increase the wall thickness of the part or increase the direction of anti-warping, and strengthen the anti-warping ability of the part by reinforcing ribs.
(6) The strength of the material used in the mold is insufficient.
2.Processing aspects:
(1) The pressure is too high, the 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.
(2) The mold temperature is too high and the cooling time is too short, which will cause the part to be ejected due to overheating during demolding.
(3) Reduce the screw speed and back pressure to reduce the density while keeping the minimum filling amount to limit the generation of internal stress.
(4) If necessary, the parts that are easy to warp and deform can be subjected to mold soft shaping or annealing treatment after demolding.