The effect of vibration on surface finish for semisolid and cast components

Abstract One of the failings of die casting and semisolid forming processes is that variable surface quality is a common result. This can reduce the competitiveness of these processes because secondary finishing operations are required, i.e. machining, polishing, plating, etc. Dies that are producing poor surface finishes cannot at the present time be substituted as it is not known what changes have to be made to give the necessary improvements. The authors have recently established that die vibration can be used to polish surfaces as they form during solidification [J. Manuf. Sci. Eng., Trans. ASME (2001), in press]. Evidence in the form of experiments performed on a purpose built rig has established that tangential vibration at certain frequencies and amplitudes influences surface finish. Micrographs combined with Talysurf readings show that die vibration can be used to generate surfaces with a quality significantly superior to that of the die. This paper is concerned with an investigation into the feasibility of applying die vibration to commercial dies and processes. Boundary element models are utilised that simulate the complex vibrational behaviour of arbitrary shaped dies. Numerical simulation is used to establish the conditions that prevail at the die surface. It is shown that by varying the position and number of sources of vibration, that conditions required for polishing can be approached. Although the research presented is at an early stage, the numerical and experimental results provide evidence that this new technology is potentially applicable to commercial semisolid and casting processes.