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

Sammanfattning

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