Plastic mold barrel and screw design considerations, can choose the regular materials compatible with the screw and barrel, GE resin to processing, special recommend the use of double metal barrel.
According to the screw diameter, had better choose compression ratio of 2.5:1, the screw length to diameter ratio for those days. Also suggest choose short feed section (5) screw groove, and a long compression section (11) screw groove, equal diameter gradient to shorter metering section (4) screw groove of the screw. Compression should be achieved by the gradient isometric taper, because, all of a sudden change will produce excessive shearing and material degradation. When unable to select a specific screw length to diameter ratio of 18:1 ~ 24:1, compression ratio was 2.0:1 ~ 3.0:1 general screw can be used successfully. Exhaust type barrel is not recommended for machining GE resin, but within a certain range, it can also be used for CYCOLAC ® ABS resin and NORYL ® PRO ® resin modified. The type of check valve should be smooth check ring type (FIG. 2-1).
In screw metering zone, over-current clearance generally need to account for at least 80% of the cross-sectional area of flow area. Small diameter screw  1/2 inch (4.76 mm) or smaller slip ring travel at least 3/16 of an inch (4.76 mm). Larger screw need a long trip, to provide the necessary flow area. Ball screw pointed tip, is not recommended due to excessive shearing and dead spot, will cause degradation.
Note: the above information by dongguan Plastic mold factory, welcome to reprint, indicate the source!