Minimisation of warpage on front panel housing moulded from virgin and recycled blend of polycarbonate (PC) material using response surface methodology and genetic algorithm

Plastic has been widely used to produce many parts especially in automotive, industrial and household products. Increasing consumption of plastic all around the world has generated a significant amount of plastic waste. Therefore, many studies have been conducted using recycled waste materials to minimise environmental problems. Mechanical recycling is preferred by the industry due to its low price and high reliability. Hence, it is a good opportunity to explore mechanical recycling and the use of recycled and virgin blend as the material to produce a new product with minimum defect. Warpage is one of the common defects in the injection moulding process that is formed on the moulded part. This defect can be minimised but cannot be diminished. A value of warpage formed on moulded plastic parts can be accepted if it lies within the range of dimensional tolerance. The processing parameters is one of the factors that can affect the quality of the moulded part other than type of materials used, parts and mould designs. Thus, in this study, appropriate processing parameters was considered to mould the front panel housing part using R0% (100% virgin), R30% (30% virgin: 70% recycle), R40% (40% virgin: 60% recycle) and R50% (50% virgin: 50% recycle) of Polycarbonate material. From the results of the simulation studies, no warpage was found in x direction on the front panel housing. Therefore, this study only focuses on reducing the warpage in y direction. Response Surface Methodology (RSM) and Genetic Algorithm (GA) optimisation methods are used to find the optimal processing parameters. The recommended processing parameters obtained from the AMI software are compared to the warpage results obtained using optimal processing parameters in the simulation studies and experimental works. RSM and GA optimisation methods were utilised. Based on the results from simulation studies, RSM and GA methods are able to reduce warpage up to 24.04% and 25.56% respectively, as compared to predicted warpage using recommended setting of processing parameters from simulation studies. In contrast, the results from experimental works showed yielded an opposite result from the simulation results, where RSM method was found to improve the warpage values up to 2.87% while GA method only showed 0.61% improvement as compared to the simulation studies. The average warpage on front panel housing moulded using R0% material through RSM was improved by 2.30% as compared to GA method. In addition, the average values of warpage in y direction on the front panel housing moulded using R30%, R40% and R50% were also improved by 1.65%, 1.05% and 0.66% respectively, using RSM as compared to the GA method. Therefore, RSM was found to effectively reduce warpage on front panel housing compared to the GA method. The most influential processing parameter that contributes to the reduction on warpage defect was packing pressure for all material used in this study (R0%, R30%, R40% and R50%). It can be seen that the optimal ratio of recycled PC material is R30% followed by R40% and R50% materials using RSM and GA methods as compared to the average value of warpage on parts moulded using R0%. The results from this research provides beneficial scientific knowledge and solutions to the moulding industries to improve the quality of the moulded part produced using virgin and recycled blends materials by employing optimisation methods especially RSM and GA.