Modeling and Analysis of Injection Moulding Process Parameters for Plastic Gear Industry Application

The performance of plastic gears in wide variety of power and motion transmission applications is rather limited due to weak mechanical properties and divergent mechanism of failures. A methodical simulation is carried out to analyze the gear performance with various gating system types, gate locations, and processing parameters via grey-based Taguchi optimization method. With the obtained optimum results in simulation stage, the flow patterns of polymer melt inside the mould during filling, packing, and cooling processes are studied and the plastic gear failures mechanism related to processing parameters are predicted. The output results in the future can be used as guidance in selecting the appropriate materials, improving part and mould design, and predicting the performance of the plastic gear before the real process of the part manufacturing takes place. 1. Introduction Gears have been in use for more than three thousand years and commonly utilized in power and motion transmission under different loads and speeds. Due to the fiscal and practical advantages, the demand of using plastics in gearing industry is significantly increased and indubitably continues in the future. In comparing with metal gears, plastic gears have several advantages such as light weight, noiseless running, resistance to corrosion, lower coefficients of friction, and ability to run under none lubricated conditions [1, 2]. Plastic gears can be produced by hobbing or shaping, likewise to metal gears or alternatively by injection moulding. With the continuous expansion of technology, plastic injection moulding bears itself to considerably more economical means of mass production to meet the rapidly rising market demand of plastic gearing in various applications. Injection moulded plastic gears have been used with success in the automotive industry, office machines, and household utensils, in food and textile machinery, as well as a host of other applications’ areas [3]. Unlike metal gears, the potential uses of plastic gear, however, are rather limited due to weak mechanical properties, poor heat conductors, and tendency to undergo creep [4]. Apart from that, the plastic gear tooth experiences complex stresses during service and can fail by divergent mechanism. Investigations on plastic gear failures were extensively conducted. Senthilvelan and Gnanamoorthy [5] observed different types of failures on the Nylon 66 spur gears such as gear tooth wear, cracking at the tooth surface, tooth root cracking, and severe shape deformation. In the review work of Breeds et al. [6] and Hooke