Uses for Wire EDM | Die Makers and EDM

Wire EDMs in vanguard of tool, die progress - electrical discharge machines

Audrey Lipford

NEW YORK--Tool and die makers are making innovative use of electrical discharge machines, while the use of lasers and programmable computer numerical control (cnc) machines use is not expected to dramatically exceed that of conventional machining methods in the immediate future, interviews with officials at several companies found.

Among the innovations now being seen are work with helical parts for aircraft, prototype and short-run jobs, mold making changes, and various applications of vectoring, orbiting, tapering and undercutting, the officials said.

The use of programmable UV axes is one significant innovation making tool and die makers strong competitors for that more diverse work, particularly in aerospace industry areas, according to David Smith, secretary and treasurer of Dayton Wireburn Inc., dayton, Ohio.

Dayton Wireburn does subcontract electrical discharge machine (EDM) work for companies in cases where volume does not justify the high cost of the purchase of such machines or the employee training and investment required to get maximum usage from the EDM technology.

The UV axes, which move independently of one another, facilitate the ability to produce different contours on the top and bottom of the workpiece, and chemical configurations, Smith said. This capability allows the tool and die maker to do more diversified work involving more than one contour, such as in aircraft work.

For example, some aircraft components require helical patterns, the creation of which is facilitated by the UV axes. Use of the Z axis, generally limited to machining a workpiece of four inches, is expanded to 10 inches with the programmable UV axes.

Micro-Cut Engineering, a job shop in Streamwood, Ill., which does contour cuting work, late last year acquired a laser cutting tool which it expects will allow it to move into areas outside those of machine tools. According to Rich Binning, owner of Micro-Cut, the $250,000 machine will allow his company to do short-run production and prototype parts for the stamping industry.

"With the laser we're looking to make a dent in the (stainless steel) signmaking business, prototype dollhouses, and plastic artwork (such as mosaic tiles)," Binning said.

While Binning acknowledged the part accuracy of the laser is not as great as that achieved from a wire EDM, he said the new areas his company plans to move into do not require the same tight dimensional accuracy of machine tools.

In the building of a die, for example, the die clearance between the punch and the die must be strictly maintained, but the part accuracy may not have to be adhered to as strictly, he said. Gaskets, for example, can have a part accuracy of plus or minus 0.005 or 0.0001 inch.

What the laser tool lacks in that accuracy, it makes up in cutting time, Binning said. A part that would take 48 minutes to cut, for example, would take 42 seconds with the laser. As a result, a six-week delivery time can be dropped to perhaps one to two weeks. The accuracy of the tool of the laser ranges from 0.0006 inch to a foot, Binning said, while its part accuracy is not that close.

The problem of controlling the laser's so-called burst of energy can be controlled by changing the pulsing mode, using a non-continuous rather than a continuous ray, Binning said.

The laser tool was manufactured by Laser Lab Sales, Inc. of Farmington Hills, Mich. Basic characteristics of the tool include a table size of 63 inches by 80 inches, a positioning accuracy of 0.0006" per foot of travel, a maximum positioning rate of 800 inches per minute and a maximum cutting rate of 400 inches per minute. Control specifications include a 16-bit micro-processor, up to nine axes of control, and advanced programming and hardware features.

Just last month, Micro-Cut initiated its first who paying cutting jobs with its recently acquired laser tool. One is a prototype part insulator out of a hard fiber material for International Business Machines Corp., White Plaines, N.Y. The second involved the cutting of gasket material for Dana Corp., Toledo, Ohio, a maker of power transmission equipment.

"The main reason I bought the (laser cutting) machine was to get into more diverse work," Binning said. "We'd like to have three or four more of them within the next few years."

Micro-Cut's wire EDM business has been "unbelievably fantastic; I like to think it is due to the quality of our work, and delivery times," Binning said. About 60 to 70 percent of Micro-Cut's business is moldmaking, the remaining 30 to 40 percent is tool and die.

The designing of molds today includes tooling which incorporates more of the capabilities of wire EDM than in the past, Binning said.

Irving Trygg, vice president of Eltee Pulsitron of West Caldwell, N.J., a builder of conventional electrode EDMs and vendor of wire cut machines, said there are about 5,000 wire cut EDMs and about 15,000 conventional EDMs currently in use in the United States.

The wire cut machines are sold at the rate of about 500 to 600 units per year, he said, adding that he expects that rate to increase by about 50 to 100 annually over the next five years after which the rate will start to slow.

Predicting a "more sophisticated operator" in the future, Charles Peterson, vice president of marketing at the Elox division fo Colt Industries, said "the bottom line is we're moving into cnc" as a result of substantial strides and demands for unattended factory operation.