Wire EDM software allows 90-percent reduction of production time

Modern Machine Shop, Feb, 1992

Only two years old, Compdraw of Attleboro, Massachusetts, has built its growing business around the speed and accuracy with which its three wire EDM machines can produce complex parts at competitive rates. Compdraw specializes in wire EDM, precision tool-building and design engineering services in a 3,000 square foot shop of four people. Its diversified customer list includes manufacturers of machine parts and tools, medical instruments and jewelry.

That's why whenever the opprtunity arises, the company uses wire EDM's capabilities, plus innovative fixturing and flushing techniques to increasingly convert conventional machining jobs to EDM wire cutting.

Their typical process was reversed in one case however. Compdraw's president, Dan Carrioggia, saw a cost-effective way to speed up production of dental parts by switching from EDM to stamping using the recently released MasterCam Wire EDM software, developed by CNC Software, 344 Merrow Ct., Tolland, CT 06084, to wire-cut the necessary tooling.

Compdraw's dental parts order call for making approximately 200 each of five differently-shaped dental instrument parts: spatula, j-hook, hook, spatula hook, and claw. Made from stainless steel, each part is about one inch long and 0.062 inch in thickness. Accuracy is maintained to within 0.001 inch.

The first three jobs of the ongoing small order were stack-cut on the EDM machines. When the MasterCam Wire EDM program was introduced, Mr. Carrioggia offered to build the customer a short run stamping tool that would dramatically reduce the piece price of follow-on orders.

The automatic reverse skimming feature of the software was used to machine the stamping tool. A major advantage this skim option offered, Mr. Carrioggia, said was its speed and ease of use, particularly in creating tool paths.

The design included punch blanks two inches long for the five dental-part shapes, the punch holder, diem and stripper. After programming the parts geometry, the tool paths were generated for the five punches. Three skim passes were chosen to achieve the desired tolerance of [+ or -]0.0002-inch and high finish--a rough cut at a high setting and the subsequent skims at lower settings.

The application's wire library automatically entered in quick sequence, the direction of each skim pass, offsets, power settings, flushing, wire diameter, and type and thickness of material. The post-processor was used to download the G codes to the wire EDM controller.

All tool parts were built from hardened D2 steel. The five punch blanks were wire-cut overnight from a two-inch block. The next day, three blocks were stacked together to cut the punch holder, die and stripper. Skimmed last, the die, which had to be larger than the punch blanks, was opened up to achieve the necessary punch die clearance. All the tooling was completed in ten hours. Stamping the 1,000 small parts reduced production substantially and the payback from the switchover allowed Compdraw to lower the customer's cost while increasing profitability.

Mr. Carrioggia reported that stamping the 1,000 dental parts now takes only one hour compared to the ten hours required by wire cutting. Such an improvement in productivity allowed Compdraw to absorb the tooling expenses, reduce the dental-parts customer's per job cost by 50 percent and still realize a larger profit.