September 2012 / Volume 64 / Issue 9|
Get your feet wet
By Yesenia Salcedo, Senior Editor
| Abrasive waterjet cutting machines are flowing into small shops as complementary equipment.
Job shops looking for a relatively low-cost, small-footprint option to produce one-offs and small runs should consider an entry-level abrasive waterjet cutting machine.
Many such shops have already jumped onboard the waterjet wagon to accommodate customers who are starting to request waterjet-cut parts, according to John Cheung, president of waterjet machine builder Omax Corp., Kent, Wash.
“Waterjet is one of the fastest-growing systems in the machine tool industry,” said Brian Kent, global product manager for waterjet machine manufacturer Flow International Corp., Kent, Wash.
Courtesy of KMT Waterjet
“The speed and versatility of waterjet make it popular for small job shops,” Kent added. “It can cut practically any shape or material, which is important to small shops because they don’t know what kind of work is coming through the door the next day. It could be stainless steel today and plastic tomorrow. Also, turnaround time is becoming more critical in the U.S. as we do more reshoring, and the versatility of a waterjet really adds to its efficiency.”
Materials commonly cut with a waterjet include steel, stainless steel, aluminum, titanium, rubber, foam, plastics, composites, stone and tile. The only materials that typically cannot be cut are tempered glass (because it can shatter on impact), diamond (because it is too hard) and certain brittle ceramics.
“Water doesn’t know what it can’t cut,” said Bob Pedrazas, marketing manager at waterjet pump and cutting head manufacturer KMT Waterjet Systems Inc., Baxter Springs, Kan. “It doesn’t discriminate. Water can be very powerful—it did a pretty good job cutting the Grand Canyon.”
As more job shops seek smaller, less-expensive waterjet machines, waterjet machine manufacturers are meeting those needs.
“The number of new waterjet systems, in general, has conservatively doubled in the last 5 years, with an annual growth of 15 to 20 percent during that time,” Pedrazas said.Why Waterjet?
It’s the waterjet’s versatility that has boosted its popularity among job shops because it complements the other machines on the shop floor.
“End users continually mention that their waterjet systems are the most versatile machine tool in their facility because of the variety of materials the system will cut,” Pedrazas said.
But waterjets won’t necessarily replace other technologies because there’s not one system out there that can do everything perfectly, according to Pedrazas. He added that what laser and plasma cutting machines can’t perform, a waterjet can.
While a laser can cut parts faster than a waterjet, lasers generally cut up to a maximum of 1" in some materials and reflective materials are problematic. Some waterjets can cut up to 15" of steel and all can cut reflective materials.
Courtesy of Miro Tool
Plasma machines also have their limitations, as they create heat-affected zones along the cut edges that can require secondary operations, such as grinding, to remove, according to Omax’s Cheung. In contrast, waterjet cutting is a cool erosion process so it does not create a HAZ.
Jeff Brown, owner and president of job shop Miro Tool & Manufacturing Inc., Waukesha, Wis., explained why his shop invested in a waterjet. “As we branched out more into the manufacturing world, we added a waterjet to complement our other systems, particularly the wire EDM, which is expensive to operate because parts take longer to cut, and the CNC machine, which is time-consuming because it requires more setup time,” Brown said.
Miro Tool has two Mitsubishi 6' × 12' waterjet systems with KMT pumps that cut material up to 6" thick at 90,000 psi.
According to Brown, a CNC machine is better than a waterjet for full production runs, but the waterjet is preferable for quick-turnaround jobs. “You can cut anything with the waterjet. We’ve used it on stainless, marble, ceramic, aluminum and hardened steel,” he said, noting CNC machines and wire EDMs are limited on the types of material they can cut.
A waterjet can be effective for certain large runs. To produce an order for 34,000 stainless steel flange plates, for example, Brown uses a waterjet because it’s faster than the CNC machine. He noted the types and thicknesses of some materials can make a CNC machine inefficient.
For Brown, determining which type of machine to use depends on the part shape, the type of material and its thickness and the tolerance specification. “Anything you want to cut with a tolerance that’s ±0.005 "—in many instances, the waterjet can be the best solution,” he said.Blast of Benefits
Waterjet systems also are becoming more attractive as the technology evolves while prices come down.
“Five years ago, I wouldn’t have bought a waterjet system because its accuracy didn’t meet our customers’ standards,” Brown said. “I sent some product out to get water-cut 5 years ago and the system just couldn’t hold the tolerances required by our customers.” But as waterjet technology continues to improve, the speed and accuracy of current waterjet systems have changed his mind.
Courtesy of Omax
Courtesy of KMT Waterjet
Depending on the operating pressure of the pump, which ranges from 50,000 psi to 120,000 psi, a waterjet can cut up to 15" of steel or workpieces as thin as paper.
“Once you get into the waterjet game, you find all kinds of things you can cut. I’m keeping two waterjets busy all the time—one running almost 24/7,” Brown said.
The versatility of waterjets can generate new revenue streams for small job shops. “With a waterjet, they can accept jobs they otherwise would have had to turn away,” Omax’s Cheung said.
Flow’s Kent concurred. “Adding a waterjet allows shops to bid larger projects that use their combined capabilities,” Kent said. “When multiple operations are involved, using a waterjet can make the entire [manufacturing] process more efficient.”
For example, Kent cited a customer that was plasma cutting an aerospace part, which then required several secondary operations. After switching to waterjetting, which takes longer than plasma cutting, the shop still went from making the part in 27 minutes to 9 minutes by eliminating some secondary processes.
Also, turnaround times are critical, particularly for a small shop outsourcing its waterjet work and relying on someone else for setting turnaround time, according to Scott Wirtanen, northeast regional manager, Boston, for waterjet machine builder Jet Edge, St. Michael, Minn.
“If a shop invests in an entry-level waterjet system and starts doing its own waterjet cutting, it controls its own lead times,” Wirtanen said.
Also, waterjets reduce operator requirements, according to Miro Tool’s Brown. “You can run it unattended, which makes it more profitable,” he said. “That’s why we bought a second machine. One guy can program and run two machines and then still go do something else.”Worth the Cost?
Research is required to find the type of machine that best meets a shop’s budget. Expect to pay around $80,000 to $125,000 for a small (4' × 4' table), entry-level waterjet machine and up to $200,000 to $400,000 for a larger (5' × 10'), more sophisticated one.
Waterjet machine builder MultiCam Inc., Dallas, Texas, has introduced a 5' × 5' system for less than $75,000 that is powered by a KMT pump.
Flow’s entry-level Mach 2 systems are available with 2m × 2m (6.56' × 6.56'), 2m × 3m (6.56' × 9.84') and 2m × 4m (6.56' × 13.12') table sizes and can cost less than $100,000. Jet Edge offers 5' × 5' models from $140,000 to $180,000. Omax’s Maxiem waterjet machine line starts at $69,000 and has a cutting area of 2½' × 2½'.
The most advanced waterjet systems with options such as multiple cutting heads, combination waterjet/plasma or waterjet/drilling heads, 3-D bevel heads, 5-axis capabilities or 6-axis robotic systems range from $250,000 to $400,000.
The size needed depends on the plate size being loaded, according to Jet Edge’s Wirtanen. “If you’re loading large parts, you’re obviously going to need a larger table size,” he said.
The main price difference between a basic waterjet machine and a more sophisticated one is based on table size (cutting envelope) and cutting speed (pressure capability).
Typically, entry-level waterjet systems use pumps with pressures up to 60,000 psi, while the more accurate, higher production and more expensive systems use 90,000-psi hydraulic pumps, which can cut from 50 percent faster to more than twice as fast as 60,000-psi pumps—depending on the horsepower (60 or 125 hp) and number of cutting heads.
Increasing the operating pressure to 90,000 psi reduces the cost per part, while improving performance, productivity and profitability, according to KMT Waterjet’s Pedrazas.
How much to spend on a waterjet machine depends on the estimated amount of work it will handle.
Miro Tool paid about $300,000 for each of its two 6' × 12', 90,000-psi waterjets, Brown noted. His goal is to earn from $125 to $150 an hour with each one.
Brown said a small job shop purchasing a $200,000 machine should have enough business to run it at least 40 hours a week to make it cost-effective. Expenses include electricity, abrasives and parts that wear and need replacement, such as nozzles.
Courtesy of KMT Waterjet
On the other hand, Flow’s Kent said even if the waterjet is used only a few hours a day, it’s more economically feasible to buy a waterjet to complement a shop’s other processes.
Others take it even further. “If you know you’re only going to use the waterjet system for a few hours a week, even 5 years from now, then an entry-level system is definitely right for you,” said KMT Waterjet’s Pedrazas.
Omax’s Cheung said the number of hours is entirely dependent on a shop’s customer base and the type of work the job shop does, but estimated that around 8 hours a week of run time would justify the purchase.
According to Jet Edge’s Wirtanen, justifying the cost is not only about the number of hours a user operates a waterjet. “What is the value of the job you’re cutting on the waterjet? You may only be using that machine 20 hours a week, but if you’re doing a high-value job for a key customer or freeing up a CNC machine to do other work, then that waterjet is valuable,” he said.
Wirtanen pointed out that one of its customers reduced material waste 35 percent by switching to a $200,000, entry-level, 5' × 5' waterjet when cutting 5"-thick Invar to rough out the shape of a part to machine later. Previously, the parts manufacturer used a $500,000 CNC machine, which created a lot of chips. Wirtanen estimates that customer uses its waterjet 30 to 40 hours a week.
As productive as they are, waterjets require some regular downtime to replace nozzles and filters, according to Miro Tool’s Brown. He estimates his are down at least 20 percent of the time.
And, in terms of consumables, waterjets can be more expensive to run than wire EDMs and laser cutters. However, a waterjet’s cutting speed more than makes up for the cost of consumables, according to Flow’s Kent.
“It doesn’t cost any money to think this through—visualize where you think you could be 5 years from now if you purchased a waterjet and if you really marketed those services to your customers,” KMT Waterjet’s Pedrazas said. CTE
About the author: Yesenia Salcedo is senior editor of CTE. Contact her at (847) 714-0177 or firstname.lastname@example.org.
Water, water everywhere
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