Cover Story by BILL KENNEDY, CONTRIBUTING EDITOR WATER WORKS Advances in Abrasive Waterjet Machining Have Encouraged a Growing Number of Shops to Adopt the Technology

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MAY 2005 / VOLUME 57 / NUMBER 5 cover story BY BILL KENNEDY, CONTRIBUTING EDITOR WATER WORKS Advances in abrasive waterjet machining have encouraged a growing number of shops to adopt the technology. High-pressure water

lthough a cycle time of 6 mil- Jewel lion years and tolerances of ±10 (orifice) A miles don’t quite meet just-in- time or Six Sigma standards, the carv- Abrasive ing of the Grand Canyon clearly shows inlet the cutting power of a stream of water. Try putting the water under pressure of 50,000-plus psi, sending it through a tiny opening so it accelerates to twice Mixing tube the speed of sound and adding hard, abrasive grit. The result is a precise erosive force that can cut virtually anything—and do it fast. Diagram Abrasive waterjet (AWJ) machining of an AWJ is often considered an unconventional cutting head. cutting technology best-suited for niche Omax applications. However, an increasing number of general manufacturers and job shops are employing it. Advances in AWJ equipment and software have boosted the versatility and ease of use of this cutting technology.

A 30-Something Process Compared to most other metalcut- ting processes, waterjet cutting is a youngster. Use of high-pressure water-

jets as cutting tools began in the 1970s. B. Kennedy Manufacturers found that a 0.005"-dia. An AWJ cuts conveyor components out of stainless steel plate at Kutz Fabricating.

34 / MAY 2005 CUTTING TOOL ENGINEERING stream of plain water at a pressure of 3-D vision 40,000 to 60,000 psi could quickly and cleanly cut soft materials such as food ruce Kivisto, general manager for wa- products and disposable diapers. B terjet manufacturing services In the early 1980s, Dr. Mohamed provider Chukar Waterjet Inc., St. Michael, Hashish, now senior vice president of Minn., said waterjet technology is relatively technology for Flow International new and “every year we get better. It used Corp., a waterjet machine builder in to be a flat technology, but now we can do Kent, Wash., invented the AWJ by 3-D. We’ve got waterjet cutting equipment adding abrasive grit to the water on a robot in our shop.” stream. The abrasive gave the waterjet Kivisto said the cutting angles possible the ability to cut nearly any material, with the AWJ extend “as far as you can

from steel, glass and rubber to difficult- twist your robot. You’ll hit a limit, depend- Chukar Waterjet to-machine materials such as titanium, ing on how you tube your water up, but ba- Robot fitted with an AWJ cutting nickel-base alloys and granite. sically you can run in any direction you head at Chukar Waterjet. Control of the AWJ cutting path and want.” The only limitations are the working speed has evolved as well. The first wa- range of the robot; the unit in his shop can cover about 75 cu. ft. terjet setups were basically liquid A typical application that illustrates its 3-D machining capacity is trimming dif- bandsaws. Today, AWJs are applied on ficult-to-machine workpiece materials to near-net shape before CNC machining or gantry-style, servodriven X-Y cutting EDMing. The benefits, Kivisto said, are “faster machining cycle times and a re- tables and even 5-axis robotic arrange- duction in the material you’re losing in the process.” ments that can make complex 3-D cuts He did mention a downside to AWJ machining: the difficulty of controlling DOC. (see “3-D vision” sidebar). Also, ad- Accurate depth in blind-holes, as opposed to through-holes, is hard to achieve. vances in control software have Also, when cutting through one side of open materials such as pipe, the uncut boosted productivity and accuracy and side must be protected, usually with some buffer material. Kivisto said the flexi- simplified machine use. bility and speed of the 3-D AWJ setup makes it a viable way to produce long and AWJs offer a variety of advantages. short runs of parts. —B. Kennedy They can cut thick (10" or more) materials as well as thin. They do not gener- more intense, maintenance than conven- sizes for different applications. Finer ate temperatures high enough to cause a tional machine tools. grits impart smoother surfaces, while heat-affected zone or part distortion. coarser grits cut faster but impart Machining pressures on the part are Pieces of the Puzzle rougher surfaces. Depending on grit minimal—typically in the range of 1 Although equipment and applications size and quality, abrasive costs between psi—which preserves the material char- vary greatly, AWJs share common char- 10 and 40 cents per pound. acteristics of the workpiece and simpli- acteristics. AWJs typically operate at The abrasive is released into the wa- fies fixturing. The AWJ’s accuracy and 40,000 to 60,000 psi. The water pressure terjet at 0.5 to 2 lbs. per minute, de- narrow kerf enable it to follow highly is generated by 2-stage intensifier pumps pending on the water pressure, nozzle detailed cutting paths, producing little or single-stage, direct-drive pumps. size and other factors. The water and or no burr. The same attributes enable At the AWJ cutting head, the water abrasive mix in a tube, which also fo- AWJs to cut around parts tightly nested travels through a 0.010"- to 0.018"-dia. cuses the cutting stream. on a single piece of material, reducing orifice in a plug called a “jewel,” made Early AWJ mixing tubes were made waste. The process neither requires nor from ruby, sapphire or diamond. The of tungsten carbide and wore out in a produces hazardous gases or chemicals. tiny opening combined with high water few hours. Today, most mixing tubes AWJs can cut reflective materials that pressure produce the AWJ’s speed. The are formed from tungsten-carbide com- pose problems for laser machining, as most common jewel material is sap- posites that contain vanadium carbide well as nonmetallic parts that cannot be phire; sapphire jewels cost $15 to $30 or molybdenum carbide and last 100 to electric-discharge-machined. each and provide 50 to 100 hours of 150 hours. The fine-grained compos- The benefits offered by AWJs are, cutting life. Diamond jewels last 800 to ites are exceptionally hard, dense and however, accompanied by some singular 2,000 hours, but cost 10 to 20 times porosity-free. But with the high hard- peculiarities. It is difficult to accurately more than those made of sapphire. Di- ness comes a degree of brittleness, so control the DOC of the cutting stream, amond can be useful where continuous care must be taken not to break the ap- and cut quality and precision are highly operation is required. proximately $150 mixing tube by run- dependent on the traverse speed of the Abrasive grit is added to the water ning it into the workpiece or machine. cutting head. While no chips or heat are stream just below the jewel. The most The orifice at the end of the mixing- generated, a shop does have to deal with common abrasive is garnet. Hard and tube nozzle generally ranges in diame- used water and abrasive. And AWJ ma- relatively inexpensive, the grit is ter from 0.015" to 0.060", and the size chines certainly require different, if not screened and classified in different of the kerf where the cutting stream en- cutting stream moves through the cut, the trailing end of the cutting stream knowledge used to guide an applica- lags behind the point where it enters tion) for AWJ machining has been key the workpiece. This lag can cause in- to advancement of the technology. accuracy in cuts that curve. Dr. John Cheung, Omax chairman, In addition, an AWJ cut tapers, or is said the software is based on the con- wider at the top than at the bottom. cept of “plan first and move later.” Generally, the faster the cutting speed, Cheung said that in the early 1990s, the greater the taper. Too much taper is Dr. John Olsen, now Omax’s opera- unacceptable in applications where tions vice president, developed AWJ tight tolerances are required or when it control software. The software com- compromises workholding in sec- bined a workpiece machinability data- ondary operations. base with details about the intended Continuing progress in overcoming cutting path. It used the information to lag and taper is the main reason for compute how fast to move the cutting growing acceptance of AWJ technol- stream to achieve a desired quality of

B. Kennedy ogy. cut, minimize taper and lag, and maxi- Blanks for these small HSS parts were Sandra McLain, marketing director mize productivity and accuracy. cut on an AWJ machine at Arthur R. for Omax Corp., a waterjet machine The software, Cheung said, permits Warner Co. OEM in Kent, Wash., said the “main- accurate machining from the get-go. The streaming” of AWJ machining “is hap- cutting path and feed rate profile are ters the workpiece is about 10 percent pening because of the software. Be- stored in a PC and used to directly drive larger than that nozzle orifice. fore, you basically controlled that the servomotors that control the X-Y The effective feed rate or cutting floppy cutting tool by G-code, which motion. For a given part geometry in a speed for an AWJ depends on multiple was sort of a black art.” Often, numer- given material, the feed rate can change variables, including the material char- ous test pieces were required before as often as every 0.0005" along the cut- acteristics of the workpiece, its thick- accurate production was possible. ting path. Precision of ±0.002" to ness and the contour of the cut itself. McLain said introduction of a PC- ±0.005" in material up to 2" thick is As a general comparison, Flow Inter- based expert system (a database of common. national lists typical cutting speeds for various materials cut on an AWJ machine running a 60,000-psi cutting Art imitates work stream through a 0.014"-dia. jewel orifice. Nominal speeds for a 1⁄4"-thick om Risser, president of U.S. Bottlers Ma- workpiece range from 76 ipm in alu- Tchinery Co., uses AWJ to make his liv- minum to 207 ipm in graphite to 30 ing—and also to make his art. ipm in mild steel to 26 ipm in Inconel. Risser said his artwork is “all over the map,” As material thickness increases, the from large-scale abstract metal sculpture to cutting speed slows. For example, furniture and fused glass. He is affiliated with while the cutting speed for 1⁄4"-thick more than half a dozen galleries and also owns mild steel is 30 ipm, it drops to 14 ipm Eight Legs South of the Tracks Gallery in Wax- for a 1⁄2"-thick workpiece and to 6 ipm haw, N.C. (Check out his entertaining Web site T. Risser T. on a 1"-thick plate. Also, a hardened at www.twisted-design.com.) Among the artwork Tom Risser workpiece cuts more slowly than one Risser said he does very little art completely creates with the help of his AWJ that is annealed. Flow International on the AWJ machine. “I’m not a guy who machine are fused-glass bowls. notes that these are maximum speeds, wants my art to look like it’s factory-pro- and to impart a high-quality surface duced,” he said. “I occasionally blank out some butterflies or something like that, finish, cutting speeds may need to be then take them home to weld and burnish them, turning them into 3-D objects.” reduced by up to 60 percent. On the other hand, he said, “you can do things with glass on the waterjet that you cannot do by hand. For fused glass, I cut spirals that nest inside each other Precision and the Floppy Tool and put them in a kiln to melt them together.” The curves and contours of the cut- Risser even makes use of manufacturing scrap. “The cool thing about a water- ting path also influence cutting speed, jet is that every time you cut a circle or a hole, you’ve got a nice piece left over, as does the level of precision desired. a nice shape,” he said. “You can reach down to the bottom of the tank and find That is because an AWJ is a “soft” tool, some really interesting metal pieces. Then as an artist, you go home and turn meaning it loses energy in the cut. De- them into furniture!” —B. Kennedy pending on the speed with which the we just waterjet and send out.” outside vendors for laser cutting,” said The minimum-taper feature of the Risser. “I wanted to bring that money control software is effective, Green said, in-house, and I discovered waterjet cut- but it slows the AWJ machine down. ting. We used to have the steel com- “Sometimes, we use it when we are ma- pany cut out a blank in a certain size. chining a keyway or the center of some- Now we cut everything from sheets.” thing that’s fairly critical,” he said. “It The AWJ also enabled the company eliminates the taper to maybe 0.001" or to eliminate sourcing of some castings 0.002".” However, customers are from outside suppliers. Instead of charged according to machining time spending $3,000 for pattern (mold for and usually don’t want to pay for the the casting) for a cast plate with a few slower cut when higher precision isn’t radiused corners, “now we do it on the necessary. The extra cost becomes ac- waterjet,” said Risser. “We cut it and ceptable, though, when a more precise we’re done. We only cut as many as we

B. Kennedy cut can eliminate a secondary operation. need, and we can cut anytime we want.” Mike Warner, president of Arthur R. Green said the software also enables Mike Warner, president of Arthur R. Warner Co. (right), and Mathias Packe, the shop to perform operations in one Warner Co., Latrobe, Pa., has an Omax shop supervisor, inspect stainless steel setup that used to require multiple ma- AWJ machine to cut HSS blanks. hose wrenches cut on an AWJ machine. chines. Previously, when machining Warner Co. specializes in the produc- flanges, “we used to have to lay them tion of thin, flat, HSS blanks, down to Recently, AWJ control technologies out, take them over to a punch press and 0.020" thick, as well as a complete line have progressed to include computer-po- make holes in them, then take them to a of HSS throwaway inserts. sitioned cutting heads that tilt to provide saw or burning table (plasma cutter) and Before it acquired the AWJ machine, taper correction. In the Omax Tilt-a-Jet burn them. Now the waterjet does every- the company cut HSS sheet and bar system, for example, the computer posi- thing at once. It puts the holes in, cuts the stock with a plate saw. Seeking greater tions the cutting head so it produces a cut circle, cuts the ID and cuts the OD,” he productivity, Warner investigated plasma that is taper-free and perpendicular on said. “We lay everything out on the cutters, lasers and AWJs. “You can’t use one side while doubling the taper on the screen—it’s Windows software—and plasma to cut HSS,” he said. “It actually waste side. Cheung said that with the sys- the waterjet cuts it.” changes the chemistry of the steel at the tem “many of our customers are able to The nesting feature of the control soft- cut and pulls the tungsten and the molyb- hold part accuracy somewhere between ware facilitates profitable AWJ machin- denum toward the surface. Laser gives a 0.001" and 0.002" on parts up to 2" ing of short production runs. Tom Risser heat-affected zone, and with HSS, I thick.” is president of U.S. Bottlers Machinery didn’t want that.” Warner settled on the However, the intrinsic precision of Co., Charlotte, N.C., a maker of cus- AWJ machine, and found it could cut the AWJ machining can make achieving tom-designed bottle-filling and -han- such levels of precision unnecessary. dling machines. The plant has a 12'x12' Many shops cut a part to near-net AWJ machine from Flow International. shape with an AWJ and then grind it to “Our longest runs are 20 to 30 parts,” final dimensions. Risser said. “The waterjet is easy to pro- Tom Green, owner of Kutz Fabricat- gram for ‘onesie-twosie’ stuff. You can ing Inc., a Pittsburgh machining and take a sheet, slowly nest in all your dif- fabrication shop, has two Omax AWJ ferent components over a week, then set machines. Kutz makes parts ranging it up and let it run for a couple of hours.” from conveyor components to thin Risser added that fixturing a part for electrical contacts. “We cut a little bit AWJ machining usually is simple. Com- of everything,” he said. “Glass, rubber, pared to the tooling and fixturing issues steel, stainless, copper, aluminum— prevalent when using a CNC milling you name it, we probably cut it.” machine, “with a waterjet, primarily all Green said his shop adjusts the accu- you are doing is sliding the plate into a racy of the cut to fit the job at hand. corner, homing it, clamping it down and “With the waterjet, you may only have a going,” he said. “You don’t have to buy couple thousandths taper on a 1⁄2" piece special tooling or fixturing.”

of material,” he said. AWJ machine B. Kennedy OEMs, he continued, “say you can hold Why a Waterjet Tom Green, owner of Kutz Fabricating, ±0.005", and that’s fairly true. I like to Often, a shop adds AWJ capacity to shows mating rubber and stainless stay around ±0.010". I know we can replace outsourced services. “We were steel conveyor components that were hold that. We do thousands of parts that spending $30,000 to $50,000 a year on cut, separately, on an AWJ machine. same material at 12 to 18 ipm that cut at A typical case is aluminum, he said. The following companies only 2 ipm on the plate saw. “Aluminum is a reflective material so contributed to this report: Warner generally cuts HSS parts to lasers have problems with it. And we near-net shape, sends them out for heat can cut it pretty much as fast as a laser, Chukar Waterjet Inc. 1 treating and then finish-grinds them. especially when it’s over ⁄4 " thick.” (763) 497-8749 However, the ability of an AWJ to pre- AWJ can make out-of-the-ordinary www.chukarwaterjet.com cisely cut hardened workpieces with no work routine. In fact, Warner said, “I heat-affected zone has helped him solve allow 20 percent of the machine’s time Flow International Corp. customer inventory crises. After acquir- for walk-in work. The guys in town (800) 446-FLOW ing the AWJ machine, Warner began to bring me stainless to cut. We’ve done www.flowcorp.com stock a variety of small, heat-treated rubber and ceramic. You name it and HSS plates. “Now, if a customer wants I’ve cut it.” Warner said he’s even cut KMT Waterjet Systems Co. to order a hundred parts, but he needs 10 different materials on the same job, cit- (800) 826-9274 real quick, we can take the heat-treated ing work on a 46"-dia. lapping pad that www.kmtwaterjet.com plate, put it on the waterjet, cut 10 parts consisted of a 0.078"-thick steel disk Kutz Fabricating Inc. and ship them to him in 4 to 5 days. It with 0.172" of rubber bonded to it. The (412) 771-9353 might be only 10 pieces, but it’s enough customer wanted Warner to make 144, to get him out of the woods,” he said. 1⁄8"-dia. through-holes in the pad, then Omax Corp. AWJ also helps Warner get the most countersink the rubber down to the (800) 838-0343 out of raw material, an important bene- steel to accommodate a 3⁄8" bolt head. www.omax.com fit as steel prices continue to rise. Using “It took a little bit of time to figure it the plate saw to cut blanks, he could out,” Warner said. “First, we cut the U.S. Bottlers Machinery Co. make 4,500 pieces of a certain tool bit through-holes with the waterjet, then (704) 588-4750 from a 2,000-lb. plate of HSS. With the we turned off the abrasive and cut the www.usbottlers.com 3 AWJ, it is possible to cut 6,800 bits ⁄8" countersinks at a high cutting Arthur R. Warner Co. from the same amount of material. The speed. We cut the rubber but didn’t cut (724) 539-9229 narrow kerf produced and tight toler- the steel, then popped the rubber out www.arwarnerco.com ances the AWJ meets, compared to the with a screwdriver.” plate saw, minimize waste. Many shops consider AWJ machining as a complement to other metalcut- must monitor these machines and keep Job Shopping ting processes rather than a straight re- them in good running condition.” John Dedic, marketing manager for placement. For example, Warner said, Flow International’s Murdock high-pressure waterjet equipment sup- “you can’t compare EDM to waterjet. stressed the importance of training op- plier KMT Waterjet Systems Co., Bax- EDM cuts very accurately, but at such erators of AWJ machines. “That’s the ter Springs, Kan., said versatility is the a slow rate. The waterjet isn’t as pre- big thing. Once they are trained, they biggest appeal of AWJ machining for cise, but it cuts really, really fast. It de- have no problems,” he said. shops. “The variety of material they can pends on what you’re doing.” AWJ machining is not the perfect so- cut with waterjet is extreme,” he said, lution for every application, but it’s cer- “from titanium and steel to foam, gran- Maintenance and Disposal tainly an alternative to consider for a ite countertops and glass.” While mate- Productivity and versatility do have range of situations. Risser is a true be- rials like foam and stone are not tradi- their price. Kutz Fabricating’s Green liever. “In the next decade, if you’re a tional fare for metalworking shops, eco- said, “It’s probably the most mainte- job shop and you don’t have a waterjet, nomic pressures are driving them to find nance-intense piece of equipment we you’re going to be really hurting,” he ways to diversify. AWJ capacity, he said, have here. You do have to keep an eye said. “Everybody needs to have one, “has given them a lot more ways to on it.” Nevertheless, he added, “I’m even if it’s a little 4'x8'. People are con- make money when times get tough.” very happy with it—I bought another stantly coming up with new shapes that Duncan Murdock, regional sales AWJ machine!” you just can’t do any other way.” manager for Flow International, called KMT Waterjet Systems’ Dedic Dedic simply looks at the present the AWJ the “Swiss Army knife of met- agreed that maintenance is critical in state of supply and demand for AWJ alcutting processes” because it can cut getting maximum precision and pro- services. “When I talk to people who nearly any material. He acknowledged ductivity out of an AWJ machine. “It’s aren’t sure if they should buy a ma- that some materials are cut more not like other machine tools that you chine, I tell them to call a job shop in quickly with a plasma cutter or a laser, just set up and run,” he said. “We try to the area that does have one, and get a but for others, AWJ excels. be very clear with people that they quote on the time to deliver a part.”

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