Effect of part geometry and processing conditions on weld line in plastics product

In Plastics injection moulded parts, a weld line is a visible result of a line or blemish on the part by the merger of more than one stream of plastics flow during processing. It is caused due to the knitting region of two upcoming flow fronts of plastics melt. These lines are usually formed due to obstructions to flow or due to the provision of more than one entry point of plastics melt into the component. The existence of weld lines in plastics parts is not only a surface imperfection, but it also impacts the strength of the part by way of structural weakness. The occurrence of weld lines in the plastics products has made the process of injection moulding a complex one. The major possible causes for the occurrence can be traced to the design of plastics parts geometry and the injection moulding process parameters used for manufacturing the product. In this study, a standard specimen of the plastics part with the unique requirements like the entry of melt defined as a gate and the obstructions to flow in terms of slots that may arise in any plastics part is being considered. The part is analyzed under various geometrical changes and process parameters of importance like injection temperature of plastics melt temperature of injection mould, injection time. Experiments were conducted for the various parameters to study the effect of results obtained from analysis and manufacture. The findings are given in the conclusion that the changes in geometry and parameters of melt injection temperature and mold temperature combination helps to get the products with minimal weld line. Given the required melt temperatures are used, mold temperature modifications provide the better quality weld. This has been verified in the optimized parameters which concurs with the test results and analyzed observations.