Injection mold factory: how to solve the problem of cracking in plastic shell processing?

Injection mold factory: how to solve the problem of cracking in plastic shell processing?

When we process plastic shells, we often have some problems, the most common of which is cracks. As we all know, the main cause of cracks is due to stress deformation, and the stress is mainly divided into residual stress, external stress and stress deformation caused by the external environment. Therefore, if the injection mold factory wants to solve the cracking problem in the processing of the plastic shell, it must start with solving the stress.

1. Cracks caused by residual stress

Residual stress is mainly due to the following three conditions, namely overfill, ejection and metal inserts. As for the cracks caused by overfilling in the injection mold factory, the solutions can be mainly started in the following aspects: =

Since the pressure loss of the sprue gate is small, if the cracks in the injection mold factory mainly occur near the sprue gate, the multi-point distribution point gate, side gate and shank gate can be considered instead; if the resin does not decompose , Under the premise of no deterioration, appropriately increasing the resin temperature can reduce the melt viscosity and improve the fluidity, and at the same time, the injection pressure can be reduced to reduce the stress; under normal circumstances, stress is easily generated when the mold temperature is low, and the temperature should be appropriately increased. However, when the injection speed is high, even if the mold temperature is lower, the stress can be reduced; if the injection and pressure holding time is too long, the stress will also be generated, and the effect of shortening it appropriately or switching the holding pressure for th times is better; non-crystalline It should be noted that crystalline resins such as polyethylene and polyoxymethylene are more prone to residual stress than crystalline resins such as AS resin, ABS resin, and PMMA resin.

2. Cracks caused by external stress

The external stress here, the injection mold factory is mainly caused by the stress concentration due to the unreasonable design, especially at the sharp corners.

3. Cracks caused by the external environment

Chemicals, water degradation caused by moisture absorption, and excessive use of recycled materials will deteriorate physical properties and cause cracks.