Wire EDM and Moldmaking | CNC Wire EDM

Applying wire EDM to moldmaking: accuracy and autonomy - electrical discharge machines - BP - Column

Wire EDM is still a relatively underutilized technology in the field of moldmaking, but when faced with a mold that was impossible to grind, Peter Fedorko, president of Parm Tool in Erie, Pennsylvania, got a close look at its potential. The results led him to further apply the technology in ways and for operations that previously were impossible for him.

In Parm Tool's 50,000 square foot facility, Mr. Fedorko turns out a variety of workpieces but his specialty is the complex injection molds such as those used for electric connectors. In 1987, a customer brought him a complex part drawing. Mr. Fedorko agreed to take it on for the manufacturing challenge and because he will not say "no" to customers. The mold called for 164 slots with a width of seven thousandths (with a taper).

"At that time, we could grind slots down to eleven and a half thousandths wide but there was just no way a grinder could touch the job," he states. Mr. Fedorko asked around and found another shop using an Agie machine (Agie USA Ltd., 839 Rohlwing Road, Addison, IL 60101) and sent the drawing to them. He goes on to say, "When I got the finished piece I inspected it closely, and within a month Parm Tool had its first Agie machine, an AgieCut 100." The company went on to produce as much as three and a half million parts for that particular project.

Parm Tool is said to be the single largest user of Vectra A130, a liquid crystal polymer. The polymer is said to be a more stable material to mold with better flow for finer centerline parts. "Using EDM from Agie, we can create molds for parts with seven thousandths walls." He goes on to say that his operator can even hold 50 millionths on the work he does. "One little secret is that we keep the room tightly temperature controlled. On the core pin blanks we're cutting out, we can hold a tolerance of 50 millionths by keeping the room at 67 |degrees~."

Today, Parm Tool uses the original AgieCut 100 and a newer AC100D wire EDM system, and both operate 24 hours a day, seven days a week.

"At first, we were using the Agie machines for the accuracy they provided. But the more we worked with them, the more we were able to take advantage of features such as the automatic wire-threading (which rethreads the wire, even in the taper) and programming, to get outstanding productivity. My operator, Gary, runs both machines but spends only 30 percent of his time doing that. The other 70 percent of the time, he spends doing some mold repair in another part of the plant. We could put another machine in there and only impact his job by another ten percent, they really are that autonomous."

How good are the parts they produce from their molds? In February 1991, they produced their highest volume of plastic parts ever and maintained a CPK level of 1.51 or six sigma for over one and a half million parts.

Mr. Fedorko describes the changes at Parm Tool by saying, "Our first priority is getting the tool right. Having a good quality tool is 85 to 95 percent of the molder's job. If you have a good tool, a molder can make a good or a bad part. But if you have a bad tool, even the best molder in the world can't do anything about it." What began as an alternative to grinding has become an essential part of Parm Tool and its success.