Putting on the Pressure

An aerospace fabricator had a problem. They were outsourcing thick plate cutting and their in-house EDMs were a slow way to produce parts that did not need exacting tolerances. The solution was to get a waterjet.

Now, they had another problem. Putnam, CT-based ERW Inc.’s business grew so much that jobs now overwhelmed their capacity. They needed another waterjet.

ERW is a custom fabricator primarily focused on the aerospace market. They specialize in hard tool thermal spray masking as well as custom sheet metal fabrication. Their machine tools include lasers, EDM, CNC mills, CNC lathes, and press brakes.

ERW often had applications where thick plate production required relatively tight finish tolerances, but still looser than that of their EDM machines. Though very accurate, EDM is a very slow cutting process, so ERW outsourced this work. Outsourcing, however, meant that they did not have complete control over the process and could miss deadlines.

The company also produced one-off form tooling for its press brakes, which they usually cut on their EDMs. For many of these jobs the part tolerance did not require EDM accuracy and they wanted their tooling created faster. They also wanted a cutting method that would not produce a heat-affected zone (HAZ) because aerospace companies are becoming less tolerant of the metallurgical changes and potential micro-cracking produced by melting the material during the cutting process. Broadening their capabilities would provide more services to their current customers, and enable them to gain new ones.

“We had a customer that required a fair amount of 1/2" 304 plate work and was willing to use us as a main source,” says Kevin Rukstela, engineer, ERW. “Continuing to outsource it did not make sense at that point. We also deal a lot with 1/4" to 1/2" Hastelloy and Inconel that we wanted to bring in house. By changing the manufacturing process, we knew we could save time and money. Milling complete parts out of high nickel alloys is just not cost effective when tolerances are reasonably open to ±0.005" or greater.”


Rescue by Waterjet
So, ERW purchased a 6ft x 12ft Integrated Flying Bridge from Flow International with Dynamic Waterjet and a 60,000psi intensifier. The purchasing team selected Dynamic Waterjet with Active Tolerance Control to provide them a competitive advantage over other regional waterjet shops. The ability to cut parts without taper also gave them the opportunity to do all of their tooling work in-house, as well as cutting custom punches and dies.

Adding a waterjet cutting system allowed them to add thicker materials to their services. Having parts with virtually no taper put them in high demand. In fact, their work for the waterjet increased so much that within three years it exceeded the capacity of their 60,000 psi machine.

“We originally selected Flow when we purchased our first waterjet because of their technical expertise and industry presence. We returned to Flow for our second system because of the very positive experience we had working with them,” Rukstela explains. “They clearly demonstrated how increasing pressure would increase our throughput.”

With the goal of continuing to produce accurate parts even faster, they purchased a 2m x 4m (6.5ft x 13ft) Integrated Flying Bridge with a HyperJet pump rated at 94,000psi and configured with Dynamic Waterjet.


Reducing Cycle Time
The choice of the HyperJet was to attain both the additional 45% increase in pressure and increased power. Operators use the same amount of garnet, yet parts are cut up to twice as fast as a conventional waterjet. In addition, because parts are produced faster, operators can get more jobs done with the same work force.

“We have moved into a lot of roughing operations for new aerospace customers on exotic alloys such as Inconel 600 and 718, as well as Hastelloy X and titanium to save CNC time. These parts were the main reason for moving up to the HyperJet due to their long cycle times,” Rukstela explains. “There are also some 3" and thicker aluminum parts that we can now cut cost effectively as a finished product with no follow-up machining. The HyperJet has definitely exceeded our expectations.”

An aerospace job cutting 2" thick Inconel demonstrates the impact of using HyperPressure technology rated at 94,000psi. On the original machine, it took 105 hours. However, with the HyperJet, it now takes 52 hours. In general, stainless cuts 40% faster than it did on the first waterjet, while thicker aluminum cuts 60% faster or more.

The part shown on the Mach 3 table is a window made of 1" thick 6061-T6 aluminum plate. Cutting it on a waterjet instead of milling provides reusable scrap pieces such as the cut out piece being removed. On the 60,000psi system, the part took 43 minutes to cut. With the new 94,000psi system, it takes 26 minutes while still maintaining the 125rms surface finish.

“We have some larger parts with more windows,” Rukstela explains. “The pierce time on the 60,000psi system took 4 seconds to 6 seconds. On our new system, it takes 1.5 seconds, so in addition to the system cutting parts faster, a significant amount of time is saved on parts with many holes or contours. “Our HyperJet machine is awesome,” Rukstela continues. “For roughing operations of 2" and thicker materials there is just no comparison to the 60,000psi machine. Cut times on the HyperJet are consistently 80% to 100% faster than the 60,000psi times were.”

Flow Int’l Corp.
Kent, WA
flowwaterjet.com

ERW Inc.
Putnam, CT
erwinc.com