1. The machine

The nozzle hole is too large, which causes the material to flow back and contract.

The flanges will also contract due to insufficient locking force. Check whether there is any problem with the locking system.

If the plasticizing quantity is insufficient, the machine platform with large plasticizing quantity should be selected to check whether the screw and the feeding tube are worn.

2. Thw mold 

The wall thickness should be uniform and the shrinkage should be consistent.

Mold cooling and heating system to ensure the temperature of all parts of the same.

The pouring system should be smooth, and the resistance should not be too large. For example, the size of the main channel shunt gate should be appropriate, the smoothness should be enough, and the transition zone should be arc transition.

For thin parts, the temperature should be increased, the material should be smooth and smooth, and for thick wall parts, the mold temperature should be reduced.

The gate should be opened symmetrically, as far as possible in the thick wall of the parts, the volume of the cold material well should be increased.

3. In plastic

Crystalline plastics contract more severely than non-crystalline plastics, and the amount of material should be increased properly in processing, or nucleated agents should be added to the plastics to accelerate the crystallization and reduce the shrinkage cavity.

4. The process

The temperature of the material barrel is too high, and the volume changes greatly, especially the temperature of the furnace in front.

The injection pressure speed is too low, the injection time is too short, so the amount or density of materials is insufficient, and the contraction pressure speed is too long, which causes the flying edge to contract.

The feeding amount is that when the buffer pad is too large, the injection pressure will be consumed.

For does not require the precision parts, the injection pressure and outer basic condensation sclerosis and sandwich part is soft and hold out parts, as soon as possible out of the mold, allow it to cool down slowly in the air or hot water, can make shrinkage depression gently and not so conspicuous and does not affect use.