A model for the surface texturing of steel rolls by electrodischarge machining

Abstract

The need for a closely defined surface texture on steel rolls used to produce steel sheet is described. Conventional shot-blasting as a method of texturing is shown to be increasingly limited by lack of adequate process control and its inability to treat hard alloys. Electrodischarge texturing (EDT) is presented as an alterative method which overcomes the difficulties encountered with the traditional technique. The mechan­isms controlling EDT are shown to depend on the peak current arising from the pulsed electric field applied between the tool-electrode and the work-roll, the time for which the voltage pulse is applied, and the randomness of the discharges produced in the machining gap. These process conditions are included in a model for the process, which is then analysed in the light of physical behaviour known to arise in electrodischarge texturing, namely that the surface roughness produced increases with peak current and with the pulse time for the applied voltage. Attention is drawn to the implications of the model for electrodischarge machining process which has, in general, hitherto proved difficult to analyse, and yet is known to be subject to similar effects of peak current and the ratios of the times for which the pulsed voltage is applied and removed. The present paper therefore also throws light on methods for tackling the general theory of electrodischarge machining which is so widely used in industry.