In the field EDM

March 1, 2002
Whether it's cutting challenging materials or part shapes that can't be done any other way, each shop has its own reasons for incorporating EDM into manufacturing operations. But whatever the reason, the result is generally the same for all: increased pro

Whether it's cutting challenging materials or part shapes that can't be done any other way, each shop has its own reasons for incorporating EDM into manufacturing operations. But whatever the reason, the result is generally the same for all: increased productivity. That's because the process produces parts with smooth finishes, reduces the need for grinding and hand polishing, and lets shops run jobs unattended.

For Swiss Craft's spare-tooling jobs, Makino EDMs deliver surface finishes that need little hand polishing.

Douglas Machine easily drills holes over 12-in. deep using a Beaumont FH Series fast-hole EDM equipped with a Siemens Sinumerik 840Di control package.

Deep holes
For Douglas Machine of Cincinnati, drilling holes over 12-in. deep with EDM recast as low as 0.0005 in. and diameter tolerances of 0.005 in. throughout is a walk in the park. But this wasn't the case until the shop added a few special CNC fast-hole EDM drills to its arsenal of machines.

The company manufactures components for the aerospace and industrial gas-turbine industries. Parts range from gas-turbine blades, vanes, and nozzles to jet-engine turbine rings, segmented shrouds, seals, rotors, and fan, compressor, and turbine covers. The majority of these components are titanium and nickel-based alloys. To tackle demanding deep-hole drilling in these tough materials, Douglas relies on 12 FH Series fast-hole EDMs from Beaumont Machine, based in Ohio.

Basically, Beaumont designed the machines specifically for Douglas. The two companies had an ongoing business relationship where Beaumont supplied the shop with rebuild and retrofit services. But Douglas' hole-drilling requirements called for more drastic measures — a completely new machine design.

Beaumont had been custom building 20 and 100-in.-travel EDMs, says Ed Beaumont, company president. But for what Douglas wanted to accomplish, the machine needed 6-axis motion for the electrode and spindle control to achieve optimum results in terms of burn time and recast/dimensional accuracy. A control package from Siemens Motion Control Systems of Elk Grove Village, Ill., did the trick.

The package includes the Sinumerik 840Di CNC, 15-in. LCD screen with online programming, six drive motors, and motion control. Siemens' 840Di on the Beaumont machine is an open-architecture, PC-based motion control. It features an industrial PC with Windows NT and a motion-control interface board with Profibus-DP. A single cable connects the control to the I/O periphery of the motor, drive, and other package components.

With the Siemens package, Douglas machine operators program on/off times, along with current and capacities, on one page — with 100 pages accessible. They use a simple mill-style layout to make G and M-code programming and machine operation easy.

In addition, a last-burn-time feature gives operators the duration of the last burn to enhance productivity, while a toolchange counter makes for seamless electrode changeover. Plus, the machine can burn multiple depths within the same program.

According to Subhan Khan, owner of Douglas, the Beaumont machines have exceeded expectations. For industrial gas-turbine nozzles and blade cooling holes, for example, the shop burns 0.010 to 0.125-in.-diameter holes using 5-axis drilling with rotating electrodes. The machines, say Khan, produce a clean surface with uniform diameters throughout the hole's entire depth, and the Siemens control delivers high repeatability from hole to hole.

Spare parts

Swiss Craft Precision Grinding, Berne, Ind., builds spare tooling such as punches and inserts for electronics and automotive dies. It also produces spare tooling for molds, but the shop does not make whole molds or dies. Because its focus is strictly on spare tooling, grinding and wire EDM are essential to its business.

However, two recently purchased wire EDMs are getting the lion's share of work that Swiss Craft used to grind. The two machines are U32K high-precision submerged wire EDMs from Makino. These machines, which join three other Makino EDMs on the shop's floor, says Todd Nussbaum, president of Swiss Craft, improve production times and finish quality.

Surface-finish capability is the reason the shop got its first U32K, which ran mostly small work using 0.004-in. wire. But more orders came in, and customers requested better surface finishes than Swiss Craft could handle with its older machines. So, it purchased the second machine to keep up.

The U32Ks, primarily, wire burn punches and die inserts. The machines feature four-axis programming that lets Swiss Craft tackle work it previously couldn't do by EDM. But four-axis programming is not the only reason Swiss Craft has the U32Ks.

Roughing speed is about twice as fast with the new equipment, and finishing speed is significantly improved over the hand finishing Swiss Craft used to rely on. Still, Nussbaum emphasizes, speed is not the only factor, or even the most important to the shop. Accuracy and surface quality are.

The U32K design is the result of a new concept in CNC wire-EDM technology. It's based on Makino's U-Series, the wire-EDM series that showcased a drop-tank design. The result is a machine that delivers operator efficiency and safety, eliminates dielectric weight shift during operation, and improves servo-reaction speed and precision.

Exotic materials

B&J Machine and Tool relies on EDM for cutting exotic materials, and Esprit CAM software speeds the machine-programming stage. The software's KnowledgeBase includes a technology database of factory recommendations for power settings, feedrates, and offsets specifically tailored to the shop's Mitsubishi FX-20 wire EDM.

B&J Machine and Tool Inc. works with exotic materials such as niobium, tantalum, tungsten, gold, platinum, and 99.99% pure aluminum. Machining these with conventional methods is tough, and the company often finds that EDM works best.

Shop machinists do book research, consult with Mitsubishi — the company that manufactured B&J's EDM — and use quite a bit of trial-and-error testing to establish proper cutting parameters. These parameters, says Jay Powers, machine and die shop super-visor at B&J, are usually a lot slower than normal. So the Sparks, Nev., job-shop looks for ways to speed the process. This includes the programming stage.

With Esprit CAM software for EDM, the shop quickly and accurately programs its EDM through 2D and 3D dimensioning. "We take a print, sketch, or even a sample part and draw the geometry," explains Powers. "Then we easily sequence the toolpaths, offsets, and so forth to download to the machine." All this is done, he adds, with little editing, which wasn't always the case at B&J.

Prior to the Mitsubishi FX-20 wire machine and Esprit software, the shop programmed its old EDM using a tape system requiring extensive, time-consuming editing. The reason, according to Powers, was that the tape system wasn't geared to the EDM process.

Although the Esprit system offers ample toolpath editing and manipulation, it has actually eliminated most editing at B&J, says Jay Thiessen, company president and chairman of the board. "Esprit is extremely compatible with our Mitsubishi," adds Powers. "The editing process involves maybe a line or two," he says, "but otherwise, it's a direct download." That's because the software has all the codes for today's EDMs. And since it is tailored to EDMing, the software automatically defines cutting conditions, power settings, offsets, and flushings for most situations. It also determines the number of rough and skim cuts needed.

Height advantage

Jimmy Huber, a senior toolmaker at Kansas American Tooling, sets up the shop's Charmilles Robofil 300 wire EDM for cutting up to 12-in.-thick extrusion-die parts.

Kansas American Tooling's first exposure to EDM was the result of a predicament. The shop, which makes tooling for the plastic extrusion industry and is based in McPherson, Kans., had accepted a job not realizing it would require a machine bigger than anything on the shop's floor.

"We needed to wire cut 12-in.-thick parts," says Harlan Doering, a vice president at Kansas, "but our one machine handled only 8 in." To achieve greater heights, the shop uses a Charmilles Robofil 310 and Robofil 300 to wire cut parts up to 15.750-in. tall. Extrusion dies from Kansas have fully streamlined flow paths that must be done on its wire EDMs. "They give us the ability to cut greater angles than most other machines," says Doering.

The latest version of the Robofil 310 is the Robofil 310P, which still accommodates tall workpieces. It features an integrated anticollision system on all five axes for effective damage protection during both manual and unattended operation. With a standard 35-lb wire spool, the machine automatically threads wire for extended machining. For toolmaking shops like Kansas, the 310P's Taper Expert option delivers accuracy when cutting changing tapers in one setup, which is critical in machining extrusion tools.

While the machine meets the needs of toolmakers working on tall parts, it is compactly structured and mounted on a single base. A developed process lets the machine's U/V head travel distances equal to those of its X and Y axes (15.7509.80 in.).

Complimenting Kansas's wire EDMs is an HD20 hole popper, also from Charmilles. The shop drills cooling channels in hard materials and start holes in parts for the wire machine. Prior to having the machine, these drilling jobs were farmed out to another shop.

In-house runoff

Star Tool Vice President Tom Montella and EDM operator Rob Morrow conducted their own productivity test between a linear-motor EDM and one with a standard ballscrew design.

Not every shop conducts its own in-house runoff to see if a linear-motor EDM is faster than a ballscrew machine. But Star Tool, which does a lot of repeat and multiple jobs, did just that. The shop, based in Chicago Heights, Ill., set up the same job on two side-by-side EDMs, a ballscrew-type and a recently purchased AQ325L linear-motor machine from Sodick. According to Tom Montella, vice president of Star, the linear-motor EDM was about 30% faster, doing the job nearly four hours quicker.

While cutting speed impacts Star's productivity, the accuracy of the linear motors is changing how the shop does business. "We now program many of the jobs that we sent out for jig grinding or form ground in house right into the AQ325L," says Montella. He adds that parts come out better than grinding and as close to perfect as one can get as far as contours, forms, arcs, and radii.

The Sodick's linear-motor design detects machining position without axis errors caused by ballscrews. Its 0.000004- in.- resolution glass scales further ensure cutting accuracy.

The Sodick EDM also provides another benefit to Star. The company, an ISO 9002-certified job-shop and production stamper, builds dies, tools, fixtures, and jigs for customers and its own stamping division. To run such jobs unattended and at night, it relies on the linear EDM's auto threader and its wire chopper, both of which eliminate jamming.