The problem of injection molding products is poor gloss

1. What is bad gloss? (Appearance)
Poor gloss refers to that the molded parts are not adhered to the mold, that is, poor replication.
2. Reasons for poor gloss
Caused by spray marks or cold materials
When spray lines or cold materials appear on the surface of the formed product, it looks as blurred as fog because it is different from the surrounding. It often appears near the gate and at uneven places.
Due to gas
This is because the gas is blocked between the mold and the resin and hinders the adhesion between them. It is more likely to occur when the pressure is low or the exhaust is not smooth.
Poor reproduction due to non-exhaust (the surface is foggy)
Due to insufficient pressure
Due to the low pressure, the extrusion pressure on the mold surface of the resin is weak, resulting in poor gloss. In the materials containing glass fiber and other fillers, the poor gloss becomes more obvious because the filler is easy to float out of the surface (the resin is easy to sink into the inside).
For example, when the injection speed is low, the pressure cannot be transferred to the end due to the resin curing, so it is easy to produce poor gloss at the end of the molded product. At the same time, when the mold temperature is low and the overall curing is relatively fast, the whole molding is also prone to poor gloss.
3. Countermeasures for poor gloss
Try to increase the pressure holding
First, try to increase the set value of pressure holding and the set value of pressure holding time. At this time, we should see that the situation is improving. If not, it can be considered that the actual pressure rise of this part is insufficient due to other reasons. At this time, the following countermeasures should be used simultaneously:
(1) Increase mold temperature
(2) Increase barrel temperature (especially nozzle)
(3) Increase gate size
(4) Increase injection speed
(5) Use material grade with good fluidity
In this way, it is expected to achieve good results in mold temperature and gate size.
Check the exhaust port
It must be checked whether the gas has been discharged completely. Check whether the thickness and size of the exhaust port required for effective gas discharge and whether it is contaminated by mold scale are ensured. Whether it is configured to the proper position is also important. If possible, it is recommended to use the short short method to understand the actual resin flow.