Study: temperature and residual stress in an injection moulded gear

Abstract

In recent years plastics have found extensive use in the fabrication of important engineering components like gears, piping, etc. The wide application of plastics has led to a rapid development of computer aided design (CAD) and computer aided manufacturing (CAM) techniques for product development. Their application to the design and production of injection moulds has the potential to reduce the mould costs substantially, with improved moulding quality. It is also possible to obtain a ‘first time right’ mould without any tool tryouts. Thermal analysis is one of the first step towards developing a CAD system for injection moulds. Once the temperatures at different points inside the cavity are known, cooling channel design can be optimised. Also stresses and shrinkages inside the cavity can be studied knowing the temperature profiles. In this paper the problem of determining the temperature distribution and thermal residual stresses which are developed due to the non-uniform cooling of the molten plastic inside the mould cavity in the injection-moulded polystyrene gear has been studied. So to reduce the scrap at the mould design phase such a modular system can be very helpful for the Indian tool manufacturers.