Solutions to furniture mold stress

Update:24-05-2022
Summary:

Furniture molds will crack, and cracking is the most co […]

Furniture molds will crack, and cracking is the most common defect in plastic products, but do you know why this happens? In fact, the reason why furniture molds crack is generally because of residual Stress caused, what is the residual stress caused by and how do we solve it.

Residual stress is mainly caused by three situations: excessive filling, demoulding and metal inserts. As a crack formed in the case of excessive filling, its solution can generally be started in this regard:

1. Because the pressure loss of the sprue is very small, if most of the cracks are generated around the sprue, we can consider using multi-point distribution gates, side gates and shank gates instead.

2. On the premise of ensuring that the resin does not decompose and does not deteriorate, I can increase the resin temperature or reduce the melt viscosity to improve the fluidity. At the same time, we can also reduce the injection pressure to reduce the stress.

3. Under normal circumstances, when the mold temperature is relatively low, it is very easy to form stress, so we need to increase the temperature appropriately, but when the injection speed is relatively high, even if the mold temperature is lower, we can also reduce the stress. produce.

4. Too long injection and pressure holding time will also generate stress. Therefore, we should appropriately shorten or switch the pressure holding effect so that it is better.

5. Non-crystalline resins, for example, AS resins, ABS resins, etc. These relatively crystalline resins such as polyethylene, polyoxymethylene, etc. are very easy to form residual stress, which we should pay attention to.

When demoulding is pushed out, due to the small demoulding slope, the roughness of the mold rubber and the punching die, the pushing force is too large and the shape stress is generated, and sometimes whitening and cracking may be formed near the pushing rod. For this point We only need to look carefully at the location of the cracks to know the cause.

During injection molding, when we insert metal parts, it is easiest to form stress, and sometimes cracks occur after a period of time.

This is mainly because the thermal expansion coefficients of the metal and the resin are too different to form stress, and over time, the stress can exceed the strength of the gradually degraded resin material and cause cracks.

The above is the only situation where the stress of the furniture mold is formed and how to solve it.