A THESIS SUBMITTED TO THE FACULTY OF MECHANICAL ENGINEERING, SCHOOL OF GRADUATE STUDIES, ARBA MINCH UNIVESITY IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE DEGREE OF MASTER OF SCIENCE IN MANUFACTURING AND AUTOMATION ENGINEERING

Abstract

This research presents a comprehensive case study on the parameter optimization of the plastic injection molding machine process with the specific objective of reducing short shot defects and shrinkages. Focused on ETHIO-plastic factory, the study employs the Design of Experiment (DOE) methodology to systematically investigate and analyze key process parameters such as injection speed, melt temperature, holding pressure, injection pressure, injection speed and cooling time. Through a series of controlled experiments and statistical analyses, including analysis of variance (ANOVA), the study evaluates the individual and interactive effects of these parameters on short shot defects and shrinkages in the context of ETHIO-plastic factory's manufacturing environment and s/n ratio is use to find the optimum setting of experiment combination. The research aims to provide tailored insights and optimized parameter settings that are directly applicable to the unique operational conditions of ETHIO-plastic factory. From the result of the experiments it is shown that the factor most strongly affects the short shoot defect and shrinkages is the met temperature, with holding pressure being a secondary consideration. The optimum parameters that can minimize the short shoot defect and shrinkages defects melt temperature (200°C), holding temperature (70MPa), injection pressure (65 MPa), injection speed 40 rpm and cooling time(18s). The outcomes of this case study contribute not only to the broader understanding of plastic injection molding process optimization but also offer practical solutions and recommendations specifically tailored to enhance the production quality and efficiency at ETHIO-plastic factory