Fabrication of cemented carbide molds with internal cooling channels using hybrid process of powder layer compaction and milling

Layered compaction manufacturing (LCM), which is a hybrid process of powder compaction and milling in layers, is applied to the fabrication of a cemented carbide mold (WC-9 mass%Co) for the forming of optical glass lenses with internal cooling channels, which are placed along the molding cavity. The mold is produced by repeating the process of powder compaction with the subsequent creation of grooves filled with paraffin wax as a sacrificial material. The channels placed along the molding cavity are formed during the sintering process by dewaxing. In the sintering process, the extent of deformation in the shape of the internal channels and molding cavity is measured. It is found that the shapes of the channels and cavity exhibit uniform linear shrinkage in the range from 17 to 19%. By filling the molding cavity with epoxy resin, the cooling capability of the mold by air is investigated by performing experiments as well as two-dimensional finite differences simulation. The cooling effect of the mold in the glass lens-forming process is also estimated by the simulation. For both resin and glass, when air is supplied to the channels, the obtained cooling rate is approximately ten times higher as compared to natural cooling at an ambient temperature.