Injection molding, we often see product surface bleaching or broken phenomenon, this phenomenon is what we call the crack.
Plastic cracking is one of the plastic products is one of the more common defects, the main reason is due to the deformation and stress around the product. Mainly to have a variety of residual stress, external stress and the deformation and stress produced by the external environment.
Injection molding processing:
Residual stress is mainly due to the following the three conditions to appear, the so-called excess, stripping out and filling metal inserts the three reasons for this. As in the case of filling excess prone to all kinds of cracks, the main solution can through the following several aspects to start.
The downsprue when injection molding processing of pressure loss minimum, so at the time when the main crack near the sprue, can consider adopting multipoint distribution points to injection into the gate, side gate and handle gate way.
In guarantee plastic resin raw materials under the premise of no decomposition, degradation, raise the temperature of the resin can improve liquidity and lower melt viscosity, at the same time also can reduce the injection pressure, to reduce stress. Mold temperature at lower prone to all kinds of stress, when this happens should be appropriate increase the mold temperature. But if the mould injection velocity is higher, even the mold surface temperature is lower, also can reduce the mold stress in different region. When the injection time and the holding time is too long also can produce all kinds of stress, its proper shorten or for several more pressure switch effect will be better. Crystals of ABS resin, AS resin, ABS resin, PMMA resin such AS a crystalline resin such AS polyethylene, polyformaldehyde prone to residual stress, should be pay attention to this situation.
Plastic mold release launch time, due to the ejection Angle is small, plastic and punch mould type coarse, make out force is too large, produce a certain amount of stress, and sometimes even around the product of plunger trace can produce bleaching or fracture phenomenon. As long as careful observation product surface crack location, which can determine the cause.
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