1, insufficient cooling or uneven

In the incomplete cooling of the ejection, the top thrust of the ejection rod often deforms the formed parts, so insufficient cooling on the forced release will produce deformation. Countermeasures are in the mold cavity full cooling, such as completely hardened before ejecting. It can also reduce the mold temperature and extend the cooling time. However, the local cooling of some molds is insufficient, and deformation cannot be prevented under normal forming conditions. In this case, it should be considered to change the path of cooling water, the location of cooling waterways or additional cooling pin holes, especially should be considered not to cool water, the use of air cooling and other ways.

2, the ejector rod caused by

some parts of poor release, the ejector rod forced release caused by deformation. For the plastic parts that are not easy to deform, this time it is not a deformation but a crack. For ABS and polystyrene parts, this deformation is manifested by the whiteness of the pushed part (see cracking, cracking, micro-cracking and whiteness). The elimination method is to improve the polishing of the mold and make it easy to release, and sometimes the release agent can also improve the release. The most fundamental improvement method is to grind the core, reduce the release resistance, or increase the inclination of the drawing die, add the ejector rod in the difficult ejector part, etc., and change the ejector way is more important.

3, caused by the forming strain

Deformation caused by the forming strain is mainly caused by the difference in the direction of the forming contraction and the change of wall thickness. Therefore, increasing the mold temperature, increasing the molten temperature, reducing the injection pressure, improving the flow conditions of the pouring system, etc., can reduce the shrinkage rate in the direction of the difference. However, only changing the forming conditions are mostly difficult to correct, then it is necessary to change the position and number of the gate, such as molding long rods to be injected from one end.

Sometimes it is necessary to change the configuration of the cooling channel; Longer sheet parts are easier to deform, and sometimes the local design of the parts needs to be changed to set reinforcing bars on the back of the upturned side. The use of auxiliary tool cooling to correct this deformation is mostly effective. If it cannot be corrected, the mold design must be corrected. Among them, the most important thing is to pay attention to make the wall thickness of the product consistent. In the case of necessity, had to measure the deformation of the product, according to the opposite direction to correct the mold.

4, crystalline plastic

larger shrinkage resin, generally crystalline resin (such AS polyformaldehyde, nylon, polypropylene, polyethylene and PET resin, etc.) than amorphous resin (such as PMMA resin, polyethylene, polystyrene, ABS resin and AS resin, etc.) deformation is large, In addition, due to the fiber coordination of glass fiber reinforced resin, deformation is also large.

Due to the narrow melting point temperature range most deformation, and is often difficult to correct. The crystallinity of crystalline plastics varies with the cooling rate, that is, the sharp cooling crystallinity decreases and the molding shrinkage decreases, while the slow cooling crystallinity increases and the molding shrinkage increases. The special correction method for the deformation of crystalline plastics is to use this. Properties.

Actually the correction method used is to make the dynamic and static die have a certain temperature difference. Is to take the other side of the warp to produce strain temperature, you can correct the deformation. Sometimes this temperature difference can be as high as 20 бу C or more, but it must be distributed very evenly. It must be pointed out that in the design of crystalline plastic molding parts and molds, if you do not take special means to prevent deformation in advance, the parts will be unable to use due to deformation, only so that the molding conditions meet the above requirements, most cases still can not correct the deformation.

5, the method of warping correction products

Products taken out of the mold if you want to correct, the simple way to correct the products on the tool, in the place of warping with heavy weight, but must clearly determine the weight of the weight with the position.

or put the warped products on the straightener, together with the product hot water near the heat deformation temperature, simply straightened by hand. But pay attention to the temperature of the hot water can not be too high, otherwise it will make the deformation of the product more harmful.

After warping correction can not leave marks on the product.

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