Vad är ?rätt? gjutkvalitet? Hur uppnås det?
Ever since ABB has begun diecasting their rotors instead of permanent mold casting it,variation in the quality of the cast has arisen. Diecasting is performed in three differentmachines, M1, M2, M3 with 400, 660 respectively 800 tons of die locking pressures.The aim of this thesis is to answer the following questions:What is the ?right? cast quality? How is the right quality achieved?For sizes 160-180 solutions will be proposed that consider eccentricity between thelaminate and the short circuit ring as well as elimination of the thin Al film that appearson the outer periphery of the rotors.Through considering the statistic material the most often diverging rotor type has beenidentified and one of the actual rotors has been sent to a laboratory to be analyzed inorder to establish the current defects. The result of the analysis shows that there areplenty of gas- and oxide-porosity.It has been proved that every time the dies temperature decreased below 120°C thecontent of gas porosity increased. It is due to rapid solidification of metal that flowsthrough the ?cold? laminate.It has confirmed that enhanced porosity in squirrel cage causes high impedance in therotors. In order to solve these defects keeping the die temperature above 120°C hasbeen suggested. Through better production practices such as arming operators withthermometer or pre warming the laminates has been proposed.Analysis of the eccentricity has shown that it mostly is caused by wear, insufficientmaintenance of machines and dies and inexperienced operators. By doing somereparation the eccentricity has been reduced to an acceptable level but keeping this levelof quality requires a lot more.Aluminum film on outer periphery is caused by a too large die chamber; wear on thedies guiding taps and insufficient adjustment of first injection phase. In order to solvethese defects it has been suggested to reduce the diameter of die chambers after morestudying of other subsystems that could have influence combined with more frequentcontrol of guide taps and better adjustment of the first injection phase.