A simple wirecut EDM operation produced an intricate Ampco 45 bronze mount jaw, which requires tolerances to within +/-.0005″. The manufacturer saved an estimated $300 on special cutters,

and scrap rates dropped from 22 percent for conventional machining to 3 percent using wirecut EDM. Conventional machining techniques would also have required end mills, ground form cutters, deburring and other secondary operations to produce this workpiece.

The finished part features nine different surfaces. Using conventional machining methods, each surface would normally require a separate setup. Drilling, boring and jig grinding would introduce three additional setups and machining operations. Finally, the teeth of the mount jaw would be cut. This conventional machining process required 4.8 hours per part.
Wirecut EDM made this operation faster and less complicated. First, the workpiece was Blanchard ground.

Next, 12 starter holes were drilled, and the workpiece was mounted for wirecut EDM. A parts programmer entered specifications into the computer, which converted those figures into a CNC program for the machine. The unattended machine then produced the mount jaws from five pieces of Ampco bronze blanks.

The same program used to cut the mount jaws also produced a nest type fixture for holding the parts while two starter holes were drilled. These holes were then wirecut to final size in a separate operation. Wirecut EDM also produced the teeth in a final operation. Hole position tolerance was held to .0005″ total, the hole size to .0003″ total, and tooth position and size to .0005″ total.

This procedure would not have been faster than conventional machining without the multiple production capabilities of the five-head equipment. Using five-head wirecut EDM to cut the blanks and fixtures, the process took a total of 2.8 hours per part and produced five parts simultaneously instead of one a 58% reduction in time compared to conventional machining.