Cracks in the middle of the jigsaw puzzle is one of the most common problems, the main factor is due to the deformation and stress.
There are residual stress, the external stress and the deformation and stress produced by the external environment.
Residual stress caused by cracking due to residual stress in the following three conditions, namely filling excess, stripping out and metal inserts.
If surplus caused the jigsaw puzzle crack filling, can from several directions to solve: (
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 resin decomposition, the deteriorating situation, raise the temperature of the resin can reduce the melt viscosity, improve liquidity and, at the same time also can reduce the injection pressure, to reduce stress.
In general, die temperature is low, prone to stress should be appropriately raise the temperature.
But when the injection 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 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.
External stress cracks caused by the external stress, the main is the stress concentration caused by unreasonable design, especially in the sharp corners, should pay attention to more
External environment caused by the crack chemicals, water degradation caused by moisture absorption, and excessive use of reworked material can make physical deterioration, cracks.