Cutting of hard and brittle insulating materials using spark discharge-assisted diamond wire sawing

Hard and brittle insulating materials have good application prospects but are difficult to machine. This research focuses on the feasibility of cutting such materials using spark discharge-assisted diamond wire sawing. By the electrochemical discharge machining (ECDM) method, spark discharges are generated on the diamond wire. However, no spark discharge is produced when the thickness of workpiece is beyond 5.0 mm, because of the difficulty in generating hydrogen gas film to electrically insulate the diamond wire from the electrolyte. To solve this problem, an oil film is online coated on the diamond wire to separate it from the electrolyte. Oil film may be absent at some micro areas where electrochemical reaction occurs and hydrogen gas is generated. Consequently, an electrically insulating film, which consists of oil and hydrogen gas, is formed on the diamond wire. Experimental results show that evenly distributed spark discharges are generated during the cutting of a 36.0 mm thick workpiece. The combination of spark discharge and diamond wire sawing facilitates the spalling of hard and brittle insulating materials. The material removal rate (MRR) and surface roughness increase with the DC voltage, wire speed, and counterweight mass.