Plastic Lump Defect Reduction in Recycled Plastic Pellets Manufacturing

Abstract

Based on the current situation, the case study company has been confronted with a large number of plastic lump defects within the process resulting in a higher production cost. Therefore, the purpose of carrying out this research project is to minimise the percentage defect rate of plastic lumps in the pelletising process by implementing Six Sigma DMAIC methodology along with quality control tools and Design of Experiment. In define phase, the process improvement team are formed and the purpose and scope of the research are set. For measure phase, Cause and Effect Diagram, Cause and Effect Matrix, Failure Mode Effects Analysis and Pareto chart are conducted through brainstorming technique in order to find the root causes of plastic lumps. In analyse phase, the quality tool and statistical technique such as affinity diagram and Design of Experiment will be applied in order to solve the root causes of plastic lumps. The root causes found in the previous phase are wrong screen pack, incorrect temperature, inadequate screw speed, lack of maintenance and lack of training. By using the Design of Experiment, the optimal parameters were found. Moreover, the work instruction which consists of operational procedure and preventive maintenance schedule are created in order to solve the problem of lack of training and lack of maintenance. For improve phase, the new parameters are implemented together with work instruction within the prescribed time. Then, control chart is created in the control phase in order to see change in the process. The result shows the percentage defect rate of plastic lump is reduced from 4.85% to just only 2.30%.