Three Types of Gears for High-Temperature Melt Pumps

The gears commonly used in high-temperature melt pumps can be classified into three types based on tooth direction: straight-tooth, helical-tooth, and herringbone-tooth. Among these, external-meshing involute profiles are the most widely used, as they are suitable for harsh operating conditions involving high temperatures (up to 350°C), high pressure, and high viscosity. The following describes the characteristics of these three types of gears:

I. Straight-Tooth Gears (Economy Type)

In straight-tooth gears, the tooth direction is parallel to the axis. They are the simplest in structure and have the lowest manufacturing costs among the three types. They do not generate axial forces during operation, resulting in lower load requirements on the bearings.

Advantages: Easy to install and disassemble, with low maintenance costs. Suitable for production conditions involving small to medium displacement, medium to low pressure, and general precision. Typical applications include PVC pelletizing production lines.

Limitations: Low meshing overlap, significant output flow pulsation, and more noticeable noise and vibration during operation. They cannot meet the production requirements for high-pressure, high-flow, or optical-grade high-precision products.

II. Helical Gears (Mainstream Type)

In helical gears, the tooth pitch is arranged at an angle to the axis. This results in higher tooth overlap during meshing, smoother transmission, minimal flow pulsation, and greater overall load-bearing capacity. They are currently the mainstream type used in the industry.

‌Advantages: The preferred solution for high-pressure (≤50 MPa), high-flow, and high-viscosity applications, suitable for the production of films, pipes, and precision extruded products.

‌Limitations‌: Axial forces are generated during operation, requiring additional design for axial force balancing; overall manufacturing costs are higher than those of straight-tooth gears.

III. Heron Gears (High-End Type)

Heron gears consist of two rows of symmetrically arranged helical teeth oriented in opposite directions. They completely offset axial forces while combining the smooth operation of helical gears with the absence of axial forces found in straight-tooth gears, making them suitable for high-end applications.

‌Advantages‌: Extremely smooth operation, minimal flow pulsation, and low operating noise. Suitable for ultra-high precision, high-pressure, and high-temperature conditions. Typical applications include the processing of specialty materials such as PC and PEEK, as well as the production of medical devices and high-end optical products.

‌Limitations‌: Complex manufacturing processes and the highest production and customization costs; primarily used in high-end custom scenarios.

Quick Selection Guide

Standard applications, budget-conscious: Straight-tooth gears

High-pressure, high-flow, precision extrusion: Helical gears (most common)

Ultra-smooth operation, high-end product manufacturing: Heron gears

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