Pitting

Pitting is produced mainly on thick walls of product. It is caused by the resin not sticking to the cavity surface. There are many reasons for pitting, but the main reason is insufficient holding pressure.

1. Insufficient holding pressure
After the resin is injected into the mold, the mold surface has solidified, but the middle part is not fully solidified. If the holding pressure is insufficient at this stage, the semi-solidified surface will not be tightly sticking to the mold cavity, which is easy to produce the pitting.

2. Resin temperature and mold temperature
When the resin temperature or mold temperature is low, the surface of the molded product solidifies faster and sometimes it is impossible to apply holding pressure. Therefore, it is likely to occur the pitting and other defects on the surface.

3. Fluidity and injection speed
When the material has poor fluidity, the filling time will be extended, and the surface layer of the molded product will solidify before the holding pressure process. Therefore, sometimes it is impossible to apply holding pressure to the resin. As a result, poor appearance such as pitting is likely to occur. When the injection speed is slow, pitting is likely to occur for the same reason.

1. Try to increase the holding pressure
First, try to gradually increase setting parameter of the holding pressure. This will basically solve the issue. If other issues such as flash occur after increasing the holding pressure, you need to set the next item "Conditions that make it easy to apply holding pressure".

2. Conditions that make it easy to apply holding pressure
The conditions are as follows:
(1)Increase the resin temperature
(2)Increase the mold temperature
(3)Increase the injection speed
(4)Enlarge the gate
(5)Adjust the thickness (1t~2t is enough)
(6)Use a material with good fluidity

By changing these conditions, the actual holding pressure applied to the cavity will increase, resulting in the less pitting.