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Waterjet Cutting

Beyond the expected

By Gretchen Salois

Above: The Techni Waterjet Quantum NXT electric servo pump allowed Mears Machine to lower machining time and reduce tooling costs.

Bringing a cleaner cutting process in-house quickens production pace

October 2015 - Precision and aerospace go hand in hand. Parts are tested and thoroughly inspected. Whether for prototypes or use in engine components, tolerances are essential. As technology advances and components demand tighter tolerances at a quicker turnaround pace, one aerospace machine shop decided it was time to make a capital investment. At Mears Machine Corp., the versatility of a waterjet cutter meant more business. “We thought the ability to rough cut basic geometric shapes with the waterjet would save us time and perishable tooling expense in final machining,” says Bryan Dobbs, general foreman. “In some cases, we could even use the waterjet for finish machining since we can hold a [tolerance] ± 0.005 in.” Mears works with titanium, Inconel 625/718, Waspaloy, Haynes 188, Hastelloy X, and high-grade stainless steels, can meet tolerances as stringent as ± 0.000025 in. and produce FFJ 1015 waterjet image1parts in a range of thicknesses. 

“Any time we can move more material with the waterjet is less time than if [it’s] cut with a conventional machine, which also reduces our tooling costs,” Dobbs explains. “We use less tooling to finish a part and because we can hold such tolerances, we can offer finish features that would otherwise need to be set up and finished using secondary operations.”

 The Avon, Indiana-based company decided to purchase a Techni Waterjet Quantum NXT electric servo pump, resulting in lower rough machining times and reduced tooling costs, according to Dobbs. The articulating head and garnet removal system particularly stood out for Mears Machine. The articulating head allows operators to cut chamfers, angles and make taper adjustments or any combination cuts without changing the waterjet setup. 

“A standard waterjet head will only cut straight down,” Dobbs adds. Because the Techni has a garnet removal system, Mears Machine doesn’t have to hire an outside contractor to pump the tank of used garnet. “We can perform periodic clean programs to remove spent garnet from the waterjet tank.”

Quicker process

Routine maintenance on the waterjet is quicker and easier compared to the model Mears Machine previously operated. “It only takes us about 20 minutes to change a pump seal on the screw-type seal, versus the two hours it took us to change a seal on the piston-style pump,” Dobbs says.

Techni designed the Quantum NXT to keep maintenance costs low. The model uses a high torque servomotor that directly acts on a high torque ball screw to reciprocate two pistons back and forth to create pressure up to 66,000 psi.  

The intensifier pumps compared to direct drive pumps are more than 25 percent more efficient when running at 100 percent duty cycle, and up to 60 percent more efficient when running at 50 percent duty cycle, have better control with infinite control over pressure, and more advanced diagnostics resulting in reduced high pressure failures and down time, according to Techni.

“The electro servo pump is much easier to work on,” notes Jim Fields, national sales manager at Techni, who has 26 years of experience designing and manufacturing waterjets. The small, lightweight pumps also have reduced pressure spikes, are quieter (65 dBA versus 80 dBA), run cleaner (without high-pressure hydraulics), and can be synchronized to allow multiple pump configurations, he says. 

Preventive maintenance cycles are required on direct drive pumps to assure that if small check valves and poppets fail, it won’t lead to more serious problems. Operators can run the intensifier and Quantum NXT until seals fail, “so you get longer life out of components,” explains Fields. “On a direct drive you don’t want to do that because they run at about 1,400 rpm. If you run them to failure, the failure mode could cause damage to the cylinder walls and plungers. Seal failure modes are significantly increased due to heat. Direct drive pumps naturally generate more seal direct heat just through friction alone. I would much prefer to perform maintenance on two hp cylinders versus three required for direct drive.”

By comparison, direct drive crankshaft pumps are smaller and quieter but cannot dead-head as an intensifier pump or the Quantum NXT. They must displace water when the motor is on and water is dumped over a relief valve in order to drain, according to the company. “With Techni’s design, there’s no risk of causing damage to plungers and cylinder walls and you get longer cutting time between maintenance cycles,” Fields says.

“We use less water and energy and it’s easier to work on,” he continues. “We continue to improve the pump design we released back in 2009. The original one was connected through an umbilical cord, which had all the wires run into it. Now we have a standalone design that can be hooked up to any machine.”

Techni pumps can be fit to any system, which can save money for customers who adopt them regardless of brand and/or different applications.

FFJ 1015 waterjet image2

Practical prototypes

Prototype work during the design cycle of aerospace components requires pieces be made quickly and to specification. “The more capabilities you have, the more you can do in-house,” Dobbs says. “The waterjet is another capability we have. The more we can do in-house without subbing to another vendor, the more time and money we can save.”

Techni’s nesting software allows operators to switch back and forth between jobs in the same way that a CNC operator uses coordinate systems to switch back and forth, says Dobbs. Nesting options are saved in a library for later use, easily accessible to operators. 

One example of the customized parts and forgings Mears Machine produces includes cutting from a larger forging. “This customer owns other forgings that are larger and made of the same material,” explains Dobbs. “Using the waterjet, we cut out the center of the larger forging, which is used to make the required part this customer needs, while still preserving the outer portion of the forged ring, which can be used to make a different part at a later time.” This process is possible because the waterjet allows operators to precisely cut through 2 in. of high-temperature alloy forging, only losing about 0.06 in. of material. 

“If we had conventionally split or parted this forging on a lathe, we would have lost too much material doing so when trying to make the second part,” Dobbs continues. “We could have used a wire EDM, but the waterjet can do this in just a couple of hours versus several hours to wire EDM a part.”

Despite what it has spent on research and development for the Quantum NXT, Techni has kept the price affordable to make it more practical for customers to adopt, Fields says. The cost competitive value pump line released in 2014 will be followed by a wider range of pumps that will be unveiled at Fabtech in November.

Customer support has been world class, says Dobbs. “With this being the only Techni waterjet we have in our shop, I didn’t expect the level of support that we received. They support us as if we had purchased 100 machines.” FFJ

Sources

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Camfil APC - Equipment Beckwood Press Co. Metamation Inc. Admiral Steel
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Messer Cutting Systems Inc.

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AMADA AMERICA, INC.

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