Many studies have been done using recycled waste materials to minimise environmental problems. It is a great opportunity to explore mechanical recycling and the use of recycled and virgin blend as a material to produce new products with minimum defects. In this study, appropriate processing parameters were considered to mould the front panel housing part using R0% (virgin), R30% (30% virgin: 70% recycled), R40% (40% virgin: 60% recycled) and R50% (50% virgin: 50% recycled) of Polycarbonate (PC). The manufacturing ability and quality during preliminary stage can be predicted through simulation analysis using Autodesk Moldflow Insight 2012 software. The recommended processing parameters and values of warpage in x and y directions can also be obtained using this software. No value of warpage was obtained from simulation studies for x direction on the front panel housing. Therefore, this study only focused on reducing the warpage in the y direction. Response Surface Methodology (RSM) and Genetic Algorithm (GA) optimisation methods were used to find the optimal processing parameters. As the results, the optimal ratio of recycled PC material was found to be R30%, followed by R40% and R50% materials using RSM and GA methods as compared to the average value of warpage on the moulded part using R0%. The most influential processing parameter that contributed to warpage defect was packing pressure for all materials used in this study.

Injection molding process is well known in plastic molding industries. The development of this process had causes the materials used to mold plastic product to increase. However, this downside of this large amount of plastic consumption also leads to the fact that plastic waste fills the landfill. This cause researches on recycling plastic to increase. Even though injection molding process has many advantages, but the occurrence of defects on plastic part molded is one of the most important issues to be resolved. Warpage defect is one of the defect that normally occurred on molded part. This paper presents a review of the current research on the outlook of injection molding process and the effect of parameter processing on plastic molded part. The effect of parameter processing on mechanical properties of plastic mold parts with a mixture of virgin and recycled material has been numerously studied. However, studies on the physical appearance and quality of plastic mold parts by a mixture of virgin and recycled material have yet to be explored.

Plastic product are commonly produced using an injection molding process. A large amount of product can produce within a very short time. One of the defect that often being encountered in the production is warpage. By determine the appropriate parameter setting by using optimisation method, the quality of the moulded part can be improve. The warpage can be minimise but difficult to eliminate. The part can be smaller than the actual size cause by the warpage. Due to this defect will cause the plastic part difficult to be assembled. Considering the increasing application of these thermoplastic materials, the use of recycled polymers has increased too. Environmental issues, the subsequent tendency to save resources and the high costs of polymers have made the recycling an inevitable option. This study provides a scientific knowledge that will be useful to plastic manufacturing industries in injection moulding process especially by using virgin and recycle material. The parameter that being significant from the studied that been review were mostly melt temperature, packing time, cooling time and packing pressure.

The injection molding process is seen to be one of a versatile and important manufacturing process. This is due to its ability in producing product with complicated design and producing part in large quantity. The advantages of this process had caused an active research on its quality improvement and process. This paper reviews the part quality issues happened in the processes. Along with the reviews of the parameters which affects the defects occurrences. Besides that, recycled plastic application in injection molding process was also reviewed. At the end, it is seen that as compared to other thermoplastic materials, LDPE is least popular and discussed as a subject of research. This paper organizes past research studies in few categories firstly the defects occurrences in plastic injection molding, followed by application of recycled material in molding plastic part, application of optimization method in injection molding, next the application of LDPE material in molding plastic part. Lastly, this paper ends with a brief summary and future work.