Tighter tolerance EDMs pay off for medical manufacturer: World Class Technology is more than the company's name, it is its reputation. Maintaining that rep meant finding machines to match the company title.

While it never pays to be sloppy, manufacturing medical products sometimes calls for tighter tolerances than other production. For World Class Technology, McMinnville, OR, holding tolerances in the ten-thousandths-inch range was critical, and it was having trouble.

With the machining equipment it had on-hand, WCT had difficulty holding the 0.0001" to 0.0002" tolerances it needed. The company specializes in metal injection molding of orthodontic products such as brackets, buccal tubes, and lingual buttons.

Adding to the close-tolerance demands, the company must use a special nickel-free stainless steel to prevent nickel-related allergic reactions that can appear after two years of exposure in an orthodontic patient's mouth.

Experience Pays Off

John Ashton, WCT tooling supervisor, went searching for alternatives to the company's existing equipment. Having had good experiences with Mitsubishi EDM machines, he went to MC Machinery Systems, Wood Dale, IL, Mitsubishi's distributor.

"I've worked with Mitsubishi machines in the past, so I already knew their capabilities," Ashton said.

WCT purchased a FA10 PS wire EDM, followed by an EA12V sinker machine.

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"We bought Mitsubishi machines because of their accuracy and speed," Ashton said.

"The FA10 PS is very accurate machine and has a small wire diameter option, with wire as small as 0.05mm," he said. "This machine is better for the tight tolerances we need. We are using both wire EDM machines to run medical production jobs nights and weekends, and producing our tools and molds during the day. This has allowed us almost 24-hour a day production."

The FA10 PS cuts ejector pin holes, core pin holes, gib pockets, and other tooling. The capabilities of the FA-S Series make it suitable for manufacturing medical and orthodontic components.

The EDM machine also delivers consumable and electrical cost savings. The Cost Save mode reduces wire consumption up to 30 percent during rough machining.

Night Shift

WCT added System 3R chucks to the FA10 PS and FA10S for unattended cutting at night. Ashton said adding the chucks to the wire EDMs maximized actual burn time with unattended cutting and increased production by reducing setup time.

Both EDMs run about 24 hours a day, producing tools and molds during the day and medical production jobs at night and on weekends.

"The machine is operator-friendly and sets up easily," Ashton said. "It also helped reduce programming time drastically."

A mold insert WCT regularly makes, once required almost 12 hours from setup to burn time on one of the older machines at the firm. The EA12V cut the process time to five hours, a savings of more than 58 percent.

"We continue to be impressed with the accuracy and repeatability of the EA12V," Ashton said. "It has proven to be a valuable asset by decreasing our scrap rate to near zero.

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"Our mold makers have to do less second operations to the molds because we are able to finish more of the details complete from the machine."

The EDM machine recently completed jobs on several projects where 0.0001" positional accuracy had to be maintained.

Heat Shield

EA12V's heat-shielding cabin structure and thermal displacement compensation features enhance accuracy by suppressing the heat displacement caused by changes in ambient temperature. A multi-position work tank lets operators do setups while circulating the dielectric fluid. A fluid-flow adjustment function permits dielectric tank circulation to be changed between two settings for improved, no-flush burning.

The need not to flush the dielectric tank was an important feature for WCT since it maintains a cleanroom-type manufacturing environment in its 60,000 f[t.sup.2] facility. Supplying orthodontia components requires a sterile and hygienic atmosphere and manufacturing environment.

"With the ability to hold tolerances, World Class will continue to be a leader in high precision metal injection molding industry serving the orthodontic and medical industries," Ashton said. Mitsubishi

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