Improving Quality in Mega-Casted Products, Identification of contributors to geometrical variation

Abstract

When using a process to produce various parts, geometrical variation describes the differences in deviations among those parts. These deviations arise due to different factors, and minimizing them contributes to improved consistency in production, increased overall product quality, and reduced costs in terms of extra rework. This master’s thesis aimed at expanding the knowledge about high-pressure die-casting (HPDC) and identifying contributors to geometrical variations. The scope of the study is limited to larger defects affecting the geometrical accuracy and excludes surface defects, porosities, and machining. The method used for reaching the goal was by conducting qualitative and quantitative approaches. A total of 11 professionals in the area of HPDC were interviewed. Production tests related to the quenching phase were also conducted in the foundry. The main finding from the study was that design is the root cause of geometrical variations, as the varying thicknesses induce residual stresses which in turn influences the accuracy of the final shape. One of the findings successfully reduced geometrical variation in megacastings but led to other problems such as sticking to the trim-press. In addition, a DoE was suggested for future studies. The DoE provides a systematic way of working and helps in finding the optimal combination of influential and easily changeable parameters.