A study of porosity formation in pressure die casting using the Taguchi approach

Porosity is one of the defects most frequently encountered in aluminium die castings. Porosity formation causes costly scrap loss and limits the use of die-cast parts in critical high-strength applications. The amount of porosity is closely related to die casting process parameters. A considerable reduction in porosity formation can be obtained using the Taguchi approach in the die casting process. An example of the off-line technique used in the Greek die casting industry is given, with the aim of illustrating practicality and ease of use by industry engineers and managers. In the thick-walled sample casting studied, the final intensification pressure contributed 69 per cent towards the reduction in porosity. Among the other parameters considered, melt and die temperatures have a smaller effect (about 10 per cent), followed by the plunger velocities in the second and first stages which have only a slight effect on porosity formation. In addition, the expected quality improvement and the cost savings under optimum parameter settings were evaluated. The expected improvement in reduction in porosity formation was found to be 48.6 per cent, while the expected cost savings for multiple casting parts under optimum conditions was calculated to be 71.4 per cent/$1 loss before the experiment.