How are workpieces mounted on wire EDM machines?
There are machinists skilled in the use of CNC milling machines and there are machinists with specific skills in the operation of wire EDM machines. This particular type of cutting machine uses a thin wire, usually copper, whose main function is to push the electrons out of the way. The copper wire does not touch the hard or exotic material or anything conductive being cut or shaped.
A Wire EDM machine that use an oil-based dielectric machine carbide workpieces (Courtesy of GF AgieCharmilles)
Handling Wire EDM Machines
The machinist can start the process from the side or from a thru-hole. A wire EDM machine can be self-threading which means there is no need to manually rethread the wire for each part of the material being cut. And to prevent the copper wire from burning, another machine is used to flush dielectric fluid continuously along the wire. This keeps the cut material removed and the wire is prevented from disintegration while working its way through the cutting task.
Thinnest Wires Used in EDM Machines
A wire EDM machine can have a wire as thin as 0.010 inch that can cut a 0.012 inch slot without retooling. There are machines that can retool to 0.04 inch, giving a 0.006 inch slot. An accuracy of 0.002 inch can be achieved but the level of accuracy will depend on the kind of material being cut and the thickness of said material.
Wire EDM machines use wires, filters and other tools
Preparing and Mounting the Workpiece
To ensure high quality and precision cutting results, part of wire EDM services is a training provided to machinists on how to prepare and mount a workpiece properly on an EDM machine. Below are five easy mounting ways for a workpiece:
Preparing the workpiece
1. Clamped to Two Tables
A minimum of 1 inch is required from the edge of the stock to the closest part of the shape to be cut in two places; front and left side, and front and right side.
2. Clamped to One Table
This mounting style requires clamping of 2 inches and 50mm overhang stock for workpieces that weigh up to 5 pounds, and 3 inches if the workpiece weighs more than 5 pounds.
3. EDM Vise
This mounting style can hold blocks of less than 6 inches long. An inch or 25mm in the vise jaws is required for blocks that weigh more than two pounds. The vise can hold blocks up to 10 pounds. Clamped between the jaws are the sides of the block which must be parallel within 0.001 inch.
4. Vee Block
For this mounting style, the cylinders need to be smooth and round with the ends faced parallel. A minimum of 1 inch or 25mm height is required for mounting. For this mounting style, the biggest cylinder is 6 inches in diameter.
5. Rotary Table
This mounting style requires a rotary table that accepts workpieces with maximum 4 inches in diameter and a maximum weight of 10 pounds.
Regardless of the mounting style used, it is important that the workpiece is secured to the table such that the electrode can make the desired cut without interfering with the workpiece or the work holding devices or tools. The workpiece should remain in place and tightly secured during the EDM process.
Would you care to share your experience in mounting a workpiece on a wire EDM machine?