CNC wire EDM helps U.S. job shop win job from Singapore

Modern Machine Shop, August, 1989

CNC Wire EDM Helps U.S. Job Shop Win Job From Singapore

ARC Industries, in Elk Grove Village, IL, is one of the highest quality mold shops in the United States. A telephone housing mold not only challenged ARC's precision capabilities, but also the company's ability to compete with an overseas shop.

In landing this order, Dennis Sjodine, President of ARC, had to match a quotation from Singapore. Meeting that price was especially difficult because the traditional approach to this type of job would involve contour grinding and other labor-intensive operations that are less expensive in Singapore.

One of the new tools ARC uses to overcome this struggle is a Robofil CNC wire EDM from Charmilles Technologies Corporation, 26 Chapin Road, P.O. Box 694, Pine Brook, NJ 07058.

The telephone mold had a total of 600 hours of wire EDM work. Over 400 of these hours were untended. Automatic wire threading, thermo-stable submerged EDMing and CNC EDM software are key contributors to the Robofil's operator-free production.

The unit also provides close-tolerance accuracy. Not only did this job demand a lean competitive price, but also 0.0002" tolerances. Another advantage to ARC's production of the telephone mold is that the EDM finish was so smooth that there was very little polishing to do. This cut labor cost.

Mr. Sjodine notes that there are many customers who will give a shop work once they know it has CNC EDM equipment. If the productivity benefits are not available, it is assumed a shop can't do the job.

To meet the parameters of low labor costs and plus zero, minus 0.0002" tolerances on the telephone housing mold, ARC used Robofil to wire EDM push-button inserts, core inserts, mold sections, dowel holes and parting line locks. Tight tolerances are mandatory for mold work to eliminate hand-fitting and flashing. The Robofil has linear glass scales and a true closed-loop positioning system to ensure these accuracies.

The geometries were generated on a McDonnell Douglas CAD/CAM system and merged at the Robofil's CNC using command files for automatic operation. Wire EDMing was broken down into 15-hour to 20-hour, untended runs. One of these runs consisted of thirty 2.25" x 1.0" x 0.375" inserts, each having two intersecting radii.

The only other production approach would have been to contour grind the inserts, which would have increased the time required for just this aspect of the job by 200 or more hours. If that would have been the only solution, ARC Industries would have ended up losing the bid to Singapore.

PHOTO : ARC Industries won a job to produce this telephone housing mold because of the

PHOTO : untended-operation capabilities of the Robofil CNC wire EDM used to produce the workpiece.