How to solve the crack problems in the plastic casing processing?
We are in the plastic shell processing, tend to be some problems, among the more common is cracked. It is well known that the main reason for the crack produced is due to the deformation and stress, and stress is mainly divided into residual stress and external stress and the deformation and stress produced by the external environment. Thus, to solve the crack problems in the plastic casing processing will have to start from solving stress.
1, the residual stress caused by cracking
Residual stress is mainly due to the following three conditions, namely filling excess, stripping out and metal inserts. As in the case of excess filling cracks, the solution can be mainly in the following aspects:
Due to the sprue pressure loss minimum, so, if the crack the main produce near the sprue, can consider to switch to a multipoint distribution points gate, side gate and handle gate way; In guarantee under the premise of resin decomposition, degradation, can raise the temperature of the resin melt viscosity reduction, improve liquidity and, at the same time also can reduce the injection pressure, to reduce the stress; In general, die temperature is low, prone to stress should be appropriately raise the temperature. But when injected at high speeds, even if the lower mold temperature, also can reduce stress. Injection and the holding time is too long also can produce stress, it shorten appropriately or Th time pressure switch effect is better; Noncrystalline resins, such AS resin, ABS resin and PMMA resin such AS a crystalline resin such AS polyethylene, polyformaldehyde is easy to produce residual stress should be attention.
2, external cracks caused by stress
External stress, here is mainly caused by unreasonable design of stress concentration, especially in the sharp corners need more attention.
3, the external environment caused by the crack
Chemicals, water degradation caused by moisture absorption, and excessive use can make quality of reworked material degradation, cracks.