A Practical Numerical Approach to Characterizing Non-Linear Shrinkage and Optimizing Dimensional Deviation of Injection-Molded Small Module Plastic Gears.

Xiansong He,Wangqing Wu

doi:10.3390/polym13132092

Abstract

This paper was aimed at finding out the solution to the problem of insufficient dimensional accuracy caused by non-linear shrinkage deformation during injection molding of small module plastic gears. A practical numerical approach was proposed to characterize the non-linear shrinkage and optimize the dimensional deviation of the small module plastic gears. Specifically, Moldflow analysis was applied to visually simulate the shrinkage process of small module plastic gears during injection molding. A 3D shrinkage gear model was obtained and exported to compare with the designed gear model. After analyzing the non-linear shrinkage characteristics, the dimensional deviation of the addendum circle diameter and root circle diameter was investigated by orthogonal experiments. In the end, a high-speed cooling concept for the mold plate and the gear cavity was proposed to optimize the dimensional deviation. It was confirmed that the cooling rate is the most influential factor on the non-linear shrinkage of the injection-molded small module plastic gears. The dimensional deviation of the addendum circle diameter and the root circle diameter can be reduced by 22.79% and 22.99% with the proposed high-speed cooling concept, respectively.

Highlights

In recent decades, with the development of polymer manufacturing technology [1,2,3,4], the share of plastic gears in the gear market has gradually increased
The latest additive manufacturing and 3D printing processes manufacturing is a great breakthrough for plastic gears manufacturing, but it is mainly used in small batch production [8]
For micro-nano manufacturing grade small module plastic gears, there are still many challenges to be addressed in micro-injection molding [12,13]

Summary

Introduction

With the development of polymer manufacturing technology [1,2,3,4], the share of plastic gears in the gear market has gradually increased. Plastic gears have obvious advantages [5] such as low weight, low cost, self-lubrication, strong ability to absorb shock and vibration, etc. It is widely used in frontier such as medical devices, aerospace, and industrial robots [6,7]. Low dimensional accuracy will affect the stability of gear transmission, produce vibration, and noise, and accelerate the fracture of tooth root and gear wear [17,18] It will inevitably shorten the service life of small module plastic gears [19]

Objectives

Methods

Results