Effects of activated charcoal on dewaxing time in microwave hybrid heating

Abstract

High energy consumption, mould cracking and wax contaminations are the major problems during dewaxing process in investment casting. On the other hand, low loss factor of most mould materials and some pattern waxes make direct microwave heating them slow. In this research, activated charcoal was added to the ceramic mould in order to improve microwave absorption and reduce dewaxing time. A modified domestic microwave oven was used as a test rig. The activated charcoal was added to the back-up stucco from 0 to 30% by weight. The microwave heating tests were carried out from 5 to 20 minutes. The dielectric properties of the green mould and the wax were measured using a co-axial dielectric end probe. It was found that the loss factor of the wax is low, and the higher the percentage of activated charcoal added into the mould, the better the dielectric loss factor and the lower the dewaxing time. Adding 25% activated charcoal in the mould causes about 40% decrease in dewaxing time. This also improved energy saving and makes the process more sustainable.