Why there are air holes in final pellets?

There are many factors, moisture, dust, or other impuries. 1: Firstly, confirm the moisture of raw material. If the raw material is too wet, add the dryer equipments before feeding. 2: Dust unit on the compactor is also good choice to remove moisture and dust. 3: Double stage with double vacuum systems and double screen changers is suitable to high quality final product requirements. Invest too much, high price. If the budget is okay, good choice. 4: Screen changer, Vacuum degassing system, high quality screw and heater, compactor. Check all of them. Need expecter help, leave message and pictures of problem machines, and I will ask for our engineer, and reply you soon.