How to select a gearbox for plastic extrusion

For a single-screw extruder, the gearbox transmits motor power to the screw at a reduced speed and increased torque. The first selection input is the screw diameter and the required screw speed range, which define the target output speed.

The second input is motor power. Together with the screw speed range, it determines the required output torque at the screw. Torque demand, not power alone, drives the gearbox frame size.

Single-screw extrusion generates axial thrust from screw backpressure. A thrust bearing configuration rated for that axial load is a normal part of the extruder gearbox specification.

Continuous operation is standard on extrusion lines, so thermal stability and a suitable service factor should be confirmed against the actual duty cycle, ambient temperature and operating hours per day.

For replacement projects, provide the original drawing or mounting dimensions, the existing motor and coupling arrangement, and the actual operating conditions. Final configuration is subject to technical review.

At HUIGUANG × CHENGFA TRANSMISSION, ZLYJ series extruder gearboxes cover the common single-screw frame range (ZLYJ133–ZLYJ250 in the confirmed model list). Detailed selection tables are available on request.