Flow Analysis in Consideration of Unstable Flow for Injection Moulding

Abstract

By the progress in resin, mould and moulding technique, it is now possible to make various products of plastics. Mainly, these products are made of thermoplastics or fibre reinforced thermoplastics (FRTP) and are moulded by injection. In the injection moulded parts, the orientation of short fibres is determined by the flow of molten resin and therefore the mechanical properties are highly dependent on the flow condition. From this reason, it is important to make clear the flow condition.
In this paper, the moulding process is investigated microscopically in order to solve the unstable flow problem. In experiment, the investigation on the flow front shape of cylindrical products in short shot moulding was carried out to observe the unstable flow. The result showed the asymmetrical flow front shape resulting from the unstable flow behavior. The flow analysis was carried out, by applying the eigenvalue analysis. The fibre orientation analysis was also performed, by using the results of this flow analysis. These numerical analyses were in good agreement with the experimental results. It is considered that this flow analysis using eigenvalue analysis is effective to express the unstable flow.