The 'non-traditional' processes are at it again: EDM, waterjet, lasers are pushing the envelope. (Sparks, Streams & Beams).
For EDM, Waterjet, and lasers, sparks, streams, and beams hold the key to the future. It wasn't that long ago that these processes were the new "nontraditional" machining novelties in the shop. By now, each has been around long enough to gain widespread acceptance, though not without creating some misconceptions about their capabilities. In the case of each, however, technical advances are extending those capabilities and, in the process, dispelling some of those lingering myths.
Breaking the speed limit
For those who think that EDMing is still a slow process, Charmilles Technologies, Lincolnshire, IL, has broken through a speed barrier with its new Robofil 240cc/440cc wire EDM machines. Cutting speeds in tool steel reaches 37 square inches an hour, smashing the previous industry-wide standard of about 30 square inches an hour. The faster cutting speed holds up even when cutting a tall part, up to 15.75", on the 440cc model.
Key to the speedy machines is Charmilles' new CleanCut generator. Features include a new spark design, a maximum ignition voltage that has been increased by 25 percent, and maximum amplitude that has been tripled from 400 amp to 1,200 amp.
From roughing to finishing the machine is zero voltage, protecting surfaces of parts from the effects of electrolysis. As a result, finer surface finishes are produced with fewer skim cuts. This is opening up applications for medical implants which use titanium and titanium alloys. The CleanCut generator prevents oxidation on the titanium and maintains surface integrity free of brass and zinc materials from the wire electrode. Other applications include carbide as the machine minimizes the depletion of cobalt binder, producing a higher bearing capacity in punches or dies. For polycrystalline diamond form tools, surface finish and edge sharpness are said to be at least equal to, and, in most cases, better than grinding.
Linear motor speed
If there is one aspect of EDMing that is thought of as being slow, it's in sinker EDM machines. Sodick Inc., Mt. Prospect, IL, has tackled that problem by introducing linear motors to both its sinker and wire EDM machines. Linear motor sinker EDMs were introduced in the U.S. at Westec in 1999; wire EDMs at Westec in 2000. Worldwide to date, Sodick has produced more than 5,000 linear motor machines and has had no trouble finding testimonials in the U.S. about their reliability and the quality of surfaces of workpieces produced on them.
The benefit of the linear motor machine is that there is no flush needed to remove chips, even from deep cavities in molds. The fast pumping effect (reciprocation) of the linear motor Z-axis movement effectively sweeps machining chips and gas out of the gap, creating consistent even surface finish, which can reduce polishing time in molds, Naughton explains.
There is no need for flush lines or flushing holes drilled in electrodes or for side-mount flushing lines, he says. The result is that quicker setup and true unattended machining are possible, and parts can be burned 30-50 percent faster with better surface finishes.
Machining speeds of 36 m/min (1,400 ipm) are possible with acceleration of 1.2G, considerably higher than ballscrew machines, says Naughton. To keep the price down, Sodick offers its AN30 die sinker with linear motors on the Z-axis only--where it really counts for the flushing capability. The machine is priced just under $80,000. Larger sinker models are available with linear motors on all three axes.
"One of the most common misconceptions about sinker EDMs is that the skill level of the operators must be extremely high," Naughton says. That has changed. Machines are so easy to operate that machine operators don't have to know code. Everything is menu-driven with the software writing programs based on cutting conditions such as depth-of-cut, shape of the electrode, surface finish, orbit pattern and other variables being calculated automatically.
Laser cutting power
Lasers continue to cut deeper--up to 1" of mild steel, according to Bill Shnowske, national sales manager, and Jeff Hahn, product/application manager. Mitsubishi Laser, Wood Dale, IL. They say the secret is "cutting power"--doing more with less. The less in this case is a 3,200-watt laser that features a good quality beam resulting from developments in a unique resonator design, the delivery system, and the beam itself.
The lower power laser is far more reliable and operating costs are significantly better than lasers in the 4-6 kW range. That's one of the misconceptions about lasers, say Messrs. Shnowske and Hahn. More power is not necessarily better. In fact, the real limiting factor in laser efficiency is found in optics technology. Larger machines, with power in the 4 kW to 6 kW range, tend to be more complicated, less stable, and more expensive to operate. Another advantageous factor for manufacturers has been the development of "laser quality" steels with chemistry that is carefully controlled for the laser process.
The laser machine industry experienced its best year in history in 2000 when more than 900 machines were sold. In 2001, machine sales dropped below 500. Growth is returning to pre-2001 rates of about 10 percent a year and 'will likely continue, Mitsubishi Laser says. Steel service centers continue to look for ways of adding value to their services. Job shops are scrambling for ways to differentiate themselves from one another, and Tier 2 and 3 suppliers are picking up fabrication work that is being farmed out by the big automotive, agricultural, and off-highway construction equipment manufacturers, according to Mitsubishi Laser.
One of the single biggest trends is the demand for automation, says Mitsubishi Laser. Currently about one-third of the new machines it sells are automated and the company anticipates that percentage could climb to 50 percent. Adding automation to the laser machine adds about half the purchase price of the laser machine alone.
Laser plus punch
Finn-Power International, Schaumburg, IL, offers a broad range of forming, punching, bending, shearing, and lasing products in varying combinations. The challenge is to match the right machine, machining combination, and automating system to meet the customer's needs today and likely requirements tomorrow.
"My job is to be a good listener and a consultant to my customer," explains Lutz Ehrlich, manager of factory automation. "I have to understand the complexity of the customer's needs so that I can give him the knowledge of our product capabilities that will most likely provide the most cost-effective solution."
Finn-Power's customers occupy that high-volume production world where piece cost is still the key consideration in making any equipment selection.
"There are many ways to make a hole in sheet metal," says Ehrlich. "The least expensive way is with a turret punch press, but adding lasers provides flexibility in part processing for the end user that can accommodate the most frequent design changes."
Combining a laser with a punch is not a new idea. John Deere did it very successfully in the early 1980s, recognizing that hard tooling just didn't give the flexibility it needed.
"The Laser Punch (L+P) machine allows the user to look at the parts, materials, intricacies of product design, and the overall costs of the parts to determine the optimum process for every production," says Ehrlich. The 20-station turret punch press provides the choice of more than 100 tools with the use of the Multi-Tool. In this way, a wide variety of production parts can be processed with punching, forming, tapping, and laser cutting in a single unit.
The L+P features a F6 turret punch press with a 60" Y-axis and a 100" X-axis; a 2.5 kW laser with a capacity of 8 mm (0.314") stainless and cold-rolled steel and 6 mm (0.236") aluminum. An auto index system precisely rotates the punch and die in their tool holders using a single AC servo motor system.
The need for automation continues to become more apparent, even in North America, where up until recently floor space has not really been a consideration. "In Europe, space, energy, and labor constraints have always been important considerations for manufacturers in selecting their equipment," says Lutz. "As a result, automation has been very popular there and is becoming more so here."
Going with the flow
Advances in waterjet machining technology seem to be coming fast and furious. Last year, Flow International Corp., Kent, WA, introduced its Dynamic Waterjet, a cutting system that tilts the cutting head to produce more accurate parts at higher cutting speeds. Software that controls the cutting head automatically compensates for the tendency of the stream to bend and create a taper in the material being cut--a common problem with waterjet cutting. The result is that material can be cut between 25-400 percent faster than a traditional flat-plate cutting machine and taper is eliminated.
Flow's latest development is the HyPlex Ultrahigh-Pressure Pump, which is available in 30-hp, 50-hp, and 75-hp versions that produce 55,000 psi. The significance of the development is that the HyPlex pump system is a direct-drive electric motor rather than a hydraulic system. It operates more like a pressure washer, running at lower power usage and lower water consumption.
According to Mike Ruppenthal, director of marketing, waterjet machining is becoming more competitive with some traditional machining processes. Growth for waterjet is coming from several quarters, principally from job shops and production facilities with flexible and lean manufacturing strategies in place.
About 70 per cent of the cutting is being done on stainless steel and aluminum in 2" or less thickness with part sizes less than 12" square, though it is possible to ramp up to much larger parts and materials. Materials up to 8" thick can be cut, and some wings and spars for the Boeing 777, for example, are being cut with waterjet. In metal cutting, typical accuracies of [+ or -]0.005"--with [+ or -]0.003" possible--can be achieved with waterjet. On the horizon, still more developments being announced at IMTS.
Charmilles Technologies, Lincolnshire, IL, www.rsleads.com/209tp-184 or circle 184
Finn-Power Int'l, Schaumburg, IL, www.rsleads.com/209tp-185 or circle 185
Flow Int'l Corp., Kent, WA, www.rsleads.com/209tp-186 or circle 186
Mitsubishi Laser, Wood Dale, IL, www.rsleads.com/209tp-187
Sodick, Mt. Prospect, IL, www.rsleads.com/209tp-188 or circle 188
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|Publication:||Tooling & Production|
|Date:||Sep 1, 2002|
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