whole_FarnsworthDavid1997_thesis.pdf (13.86 MB)
A study of dimensional limitations in low pressure die casting
thesisposted on 2023-05-26, 21:25 authored by Farnsworth, David
This project is a study of low- pressure die casting process in Southern Aluminium Pty. Ltd., a subsidiary of Comalco in Tasmania. The first major stage in the wheel manufacturing process is casting. Wheels for automobile companies such as Nissan, Ford and Mazda are cast using a low-pressure die casting process. A casting cycle involves filling of the dies with molten aluminium solidifying the aluminium in the dies, ejecting the solidified castings from the dies, quenching the castings to a temperature close to room temperature and delivering the castings to the operator for further processing. When running at full capacity, each casting machine is capable of producing two castings simultaneously every six minutes. Each metal transfer into the caster crucible yields enough volume of metal for the production of approximately sixty wheels. The operator that initiates the casting cycle is responsible for some further wheel processing operations. These operations include the stamping of each cast wheel with a melt number stamp, manually removing any visible marks from the front face of each wheel and removing excess aluminium from the top and bottom rim of each wheel and finally, checking the castings for distortion using a distortion gauge. Each time the caster crucible is filled, an alloy sample is taken from the crucible and examined spectrographically to determine alloy composition. The alloy composition is recorded and the melt number is changed. The melt number of each cast wheel can then be related to an exact alloy composition. A distortion gauge placed on the front face of the wheel will inform the operator of the wheel distortion. A wheel that it badly distorted, greater than plus or minus half a millimeter out of plane is rejected. Further there is limitations on the minimum thickness that can be cast on these wheels. The conditions to achieve the minimum thickness in effective casting have been established in industry over a series of investigations. This project highlights the conditions necessary to maintain minimum thickness in wheel castings, produced by low-pressure die casting, by taking into consideration various process variables. The stress analysis and solidification rates have been studied as a part of this investigation using finite element and finite difference methods. The experimental investigation in achieving minimum effective casting thickness complements the results from the finite element investigations. The experiments were carried out over 500 wheels for Nissan, Ford and Mazda wheels to understand the effect of process variables on cast dimensions This investigation gives a better understanding of the major process variables that control the thickness in casting process. The outcomes of this thesis are extremely useful for practicing engineers in achieving minimum effective thickness in aluminium wheel castings, using low pressure die casting, in modern manufacturing industry.
Rights statementCopyright 1998 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s). Thesis (M.Eng.Sc.)--University of Tasmania, 1998. Includes bibliographical references