An Experimental Investigation on the Effect of Vibration on Casting Surface Finish

Abstract

One of the failings of the pressure die casting process is that variable surface quality is a common result. This paper provides evidence that die vibration can be used to polish castings as they form during solidification. Evidence is obtained from experiments performed on a purpose built rig that is designed to be representative of the pressure die casting process. The rig’s design is such that part of the casting face can be subjected to tangential vibration at prespecified frequencies and amplitudes. The castings made are viewed under a microscope and micrographs produced. These combined with Talysurf readings show that die vibration can be used to generate casting surfaces with a quality significantly superior to that of the die. Supporting evidence is also provided by thermocouple readings and the solution of the inverse parabolic heat equation. The expected increase in the interfacial heat transfer coefficient is obtained with improved casting surface quality. Established in the paper is the effect of vibration frequency and amplitude on the Ra value of the casting surface. It is shown that threshold values for frequency and amplitude exist, below which surface improvement is diminished.