n South African Journal of Industrial Engineering - Assessment of surface finish and dimensional accuracy of tools manufactured by metal casting in rapid prototyping sand moulds : general article

Volume 23, Issue 3
  • ISSN : 1012-277X



In this paper, an initial assessment of the quality parameters of the surface finish and dimensional accuracy of tools made by metal casting in rapid prototyping (RP) sand moulds is undertaken. A case study from a local tool room, dealing with the manufacturing of an aluminium die for the lost wax process, is employed. Modern techniques, including surface roughness analysis and three dimensional scanning, are used to determine and understand how each manufacturing step influences the final quality of the cast tool. The best surface finish obtained for the cast die had arithmetic average roughness (Ra) and mean average roughness (Rz) respectively equal to 3.23μm and 11.38μm. In terms of dimensional accuracy, 82% of cast-die points coincided with the Computer Aided Design (CAD) data, which is within the typical tolerances of sand cast products. The investigation shows that mould coating contributes slightly to the improvement of the cast tool surface finish. The study also found that the additive manufacturing of the sand mould was the chief factor responsible for the loss of dimensional accuracy. These findings indicate that machining will always be required to improve the surface finish and the dimensional accuracy of cast tools in RP sand moulds.

In dié artikel word ‘n aanvanklike beoordeling van kwaliteitsparameters in terme van oppervlak-afwerking en dimensionele akuraatheid van gietstukke vervaardig deur metaal gieting in snel-prototipering sand gietvorms gedoen. 'n Gevallestudie aangaande die vervaardiging van 'n aluminium gietstuk vir die verlore wasproses word gebruik. Moderne tegnieke, soos oppervlak-grofheidsanalise en drie-dimensionele skandering, word gebruik om te bepaal hoe elke vervaardigingstap die finale kwaliteit van die gietstuk beïnvloed. Die beste oppervlak afwerking verkry vir die gietstuk het Ra en Rz waardes van 3.23 μm en 11.38 μm onderskeidelik gehad. In terme van dimensionele akkuraatheid, het 82% van die gietvormpunte ooreengestem met die rekenaarnumeriesbeheerde data wat binne tipiese toleransies is vir sandgegote produkte. Die ondersoek wys dat gietvorm oppervakbedekking effens bydra tot die verbetering van die gietstukafwerking. Ook is gevind dat die snel-prototiperingvervaardigingsproses van die sandgietvorm die hooffoorsaak is vir die verlies aan dimensionele akkuraatheid. Dié bevindings dui aan dat masjinering altyd nodig sal wees om die oppervlak-afwerking en dimensionele akkuraatheid te verbeter.

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