Screw Diameter
The screw diameter of an extruder refers to the outer diameter of the screw, which is commonly used to indicate the extruder's specification. China established an extruder standard as early as 1988: ZB G95 009.1—1988, Basic Parameters of Single-Screw Extruders. This standard specified the extruder specification size series as: 20mm, 30mm, 45mm, 65mm, 90mm, 120mm, 150mm, 200mm.
The European Committee of Machinery Manufacturers for the Plastics and Rubber Industries also has a recommended extruder specification size series: 30mm, 45mm, 60mm, (75mm), 80mm, 90mm, (100mm), (120mm), (125mm), 150mm, (160mm), 200mm, 250mm, 300mm, 350mm, 400mm, 500mm. Dimensions in parentheses should be avoided as much as possible.
China's extruder standard was revised in 1996 to replace the old one, with the new standard being JB/T 8061—1996, Single-Screw Plastic Extruders. The new standard specified the extruder size series for China as: 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 80mm, 90mm, 100mm, 120mm, 150mm, 200mm, 250mm, 300mm.
However, the vast majority of commonly used extruder sizes in China still follow the old standard, and most extruders on the market are still specified as: 30mm, 45mm, 65mm.90mm, 120mm, 150mm, etc. The specifications added in the new standard are rarely adopted. The screw diameter of large single-screw pelletizers abroad has currently reached 600mm.