Analysis of the cause: The so-called Burn Mark generally includes the discoloration of the surface of the product due to plastic degradation and the blackening of the filled end of the product. Charring is the air in the trapped cavity that is not quickly discharged (trapped) when the plastic melt is filled, compressed to significantly heat up, and the material is scorched. Poor exhaust.
Countermeasure: Strengthen the exhaust in the trapped area to allow the air to be discharged in time. Reduce the injection pressure, but it should be noted that the injection speed will decrease after the pressure drops, which will easily cause flow marks and weld marks and weld lines to deteriorate.
1. Multi-stage control filling is adopted, and multi-stage deceleration mode is adopted at the end of the forming process to facilitate gas discharge.
2. The vacuum pump is used to extract the air in the cavity, so that the cavity is filled under vacuum. Clean the venting groove to prevent clogging.
3. The gate is too thin or too long, causing the plastic to degrade. p Exhaust tank, exhaust inserts, etc.