In the same figure, L/D is 20, the ratio of Feed (F) / Compression (C) / Metering (M) is divided into 60/20/20, pitch H
is almost equal to screw diameter D, and compression ratio C.R. of the screw is 2.0:1~2.5:1. The screw that its surface is covered with thick film hard Cr coating is good. When the glass fiber reinforced material is used, there is a problem of abrasion, but constantly preparing spare screw and regularly exchanging after recoating are recommended.
The screw that processed nitriding treatment is hard to be worn due to its high hardness. On the other hand, for transparent product and colored product (except the black) avoiding the burn, because it is easy to cause the burn in PC molding, it had better use the screw that processed with (Ni+Cr), (Co+Cr), TiC treatment at the surface though it is a little expensive.
Recently, the example which uses dulmage, sub flight, pin screw mounted at the screw head with the purpose to improve the melting and mixing and the dispersibility is observed with the precondition of not giving excessive shearing force to PC and the design without PC stagnation.