At the front of the barrel, the molten plastic leaves the screw and travels through a screen pack to remove any contaminants in the melt. The screens are reinforced by a breaker plate (a thick metal puck with many holes drilled through it) since the pressure at this point can exceed 5,000 psi (34 MPa).
Before being injected into the mold, molten plastic undergoes a filtering process at the front of the barrel, passing through a screen pack and then encountering a reinforced breaker plate, which is designed to withstand pressures as high as 5,000 psi (34 MPa) at this point.