CATEGORY: EDM
PUBLICATION: Metal Forming, March 2006

 

Keys to Efficient, Economical Wire EDM

Make the most of your wire-EDM machining by purchasing units with energy-saving features, adopting efficient production practices and using the correct wire—coated wire can increase speed by 15 percent.

 

Wire-EDM machines make it possible to achieve the small, odd-shaped angles and intricate contours and cavities required in the machining of stamping tools and dies. Traditional cutting techniques cannot achieve these angles in such hard metal alloys.

EDM is a good machining solution for parts or materials that tend to leave tough burrs when machined by traditional methods. EDM leaves no burrs, making the deburring process unnecessary and, therefore, eliminating the dimensional changes caused by this process.

Here are some guidelines to ensure you are running your wire EDM machine as efficiently and economically as possible.

Reduce Costs

It is crucial to your company’s bottom line to be ever-mindful of operation and production costs. Purchasing EDM machines with energy-saving features, adopting efficient production practices and using the correct wire are all ways to reduce costs. Many EDM manufacturers are adding features to lower operation costs. For example, some machines offer a cost-saving mode that minimizes wire consumption by slowing down the wire feed as it passes between upper and lower guides.

When purchasing EDM equipment, pay particular attention to the power supply. Newer models on the market often have energy-saving power-supply features that produce less heat and consume less resin, or include power regeneration circuits.

Manufacturing lights-out or incorporating automation also will help minimize production costs and time. Maximize unattended run time by using multiple-parts setups and designing around unattended burning.

Automating the EDM process by adding a robot for machine loading/unloading will help reduce labor costs. And, finally, for the most economical wire consumption, use the optimum wire for the application. Brass is the most cost-effective and commonly used wire for EDM. But for faster speeds, some shops use a zinc-coated wire. Although the per-pound price is slightly higher, coated wire can increase speed by 15 percent, for improved turnaround and productivity.

Edge and Hole Starting

To save time and preserve accuracy when starting edges and holes, consider these pointers:
• Starting from an edge is easier on a submerged machine.
• For additional protection against wire breakage, use a thickness-adapting function for the edge start-up.
• Make the start hole as large as possible to minimize burn time in scrap.
• String punches together for longer, unattended burning. Cut parts off during the day while the operator is present.
• Minimize required operator intervention by using slugless (coreless) machining.

Performing a slugless burn is advantageous when the process will result in a slug that will move and pinch the wire, or when it is so small it could potentially get caught in the lower flush cup.

Further, some machines, when experiencing wire breakage due to a poor batch of material will, after a preset number of wire breaks, make stepped adjustments to complete the job in an unattended operation.

Preparing Blanks

Maximizing conditions such as flushing pressure when preparing blanks will help achieve more efficient machining. For example, some shops leave extra material for clamping and spacing between the parts to preserve the flushing pressure from the previous cut.

Another tip: Try to minimize clamp and step heights when designing fixtures. The flatter the stack the better, to ensure no flushing loss occurs. Weld the stacks when possible, but if screws are needed, use flathead screws to clamp stacks together. This helps maintain the closest possible gap at the flush cups.

One last tip: When cutting thick workpieces or difficult-to-machine materials, set a limit to the feed-rate address value in order to optimize part straightness. This helps the machine attain the best rough-cut speed with the least chance of wire breakage. It also allows the operator to be more aggressive with manual power-setting adjustments to push for faster settings.

 

Featured in March 2006 Metal Forming.