Tuesday | 21 May, 2013 | 3:05 pm

Space exploration

By Lauren Duensing

Because of its cold-cutting capabilities, waterjet technology can handle high-tech parts at SpaceX

May 2013 - Long before man landed on the moon, Socrates said, “Man must rise above Earth to the top of the atmosphere and beyond, for only then will he fully understand the world in which he lives.” Exploring the far reaches of space is fascinating to many people, including Elon Musk, the founder of Space Exploration Technologies Corp., Haw­thorne, Calif. Musk founded SpaceX in 2002 to revolutionize space transportation with the ultimate goal of enabling people to live on other planets. 

SpaceX designs and manufactures rockets and spacecraft and has successfully launched both the Falcon 1 and the Falcon 9 launch vehicles. In 2008, NASA selected SpaceX to resupply the International Space Station. On May 25, 2012, the Dragon spacecraft became the first commercial vehicle to successfully attach to the ISS, delivering water, clothing and food to the astronauts. Previously, only the United States, Russia, Japan and the European Space Agency had accomplished this technical feat. SpaceX has now begun regular missions to the ISS and completed its first official cargo resupply mission on Oct. 28, 2012, returning with important samples and space station hardware.


Cutting high-tech parts

The Falcon 1 and Falcon 9 are two-stage launch vehicles powered by liquid oxygen and rocket-grade kerosene. Their primary and tank structures are designed by SpaceX and include materials such as space-grade aluminum alloys, aluminum lithium and carbon fiber aluminum composites. 

To cut these and other high-performance materials, SpaceX uses waterjets. In July 2010, the company purchased a Mach 3 waterjet system with a 60,000 psi intensifier and Dynamic Waterjet technology from Flow International Corp., Kent, Wash. A few months later, SpaceX added more tables and a Mach 2 system with a 60,000 psi pump for conventional cutting. The company also has another Mach 3 system with a Hyperjet pump that is rated at 94,000 psi and has Dynamic XD for bevel and 3-D cutting.

In addition, SpaceX has the latest Mach 4 technology from Flow. “We decided to purchase Flow’s Mach 4 systems to give us even greater flexibility,” says Rick Cortez, manager of development operations for SpaceX. The newest addition to Flow’s Mach 4 waterjet series allows the system to be sized initially as a 2 meter or 3 meter wide by 2 meter long cutting bed, with the ability to expand later to a length of 14 meters (48 feet). Each system is controlled by FlowMaster software, which allows the operator to load a drawing, enter the material, thickness and edge quality, and begin cutting parts. It also monitors the pumps, ensuring they are operating at peak performance. 

Waterjets have several characteristics that make them a good choice for high-tech applications, including the ability to cut virtually any material accurately with no heat-affected zone. Burning methods, such as laser or plasma cutting, create a heat-affected zone that can cause microcracking when the part is shaped. For the aerospace industry, microcracking can be catastrophic, and the part needs to go through extensive secondary processing to grind away the hardened edge. 

“Waterjets can cut basically any material. They’re not limited to just your standard alloys,” says Brian Kent, global product manager at Flow International. “You cut with no heat, so there are no metallurgical changes and no heat-affected zone. In aerospace and high-tech applications, they’re using a lot of alloys that are designed to resist heat, and you want to cut those with a cold-cutting process, such as waterjet.”

For companies like SpaceX, installing a variety of equipment from Flow allows them to manage part production. All waterjets—whether they’re an entry-level model or have more advanced capabilities like five-axis cutting—will cut all types of material; however, more advanced machines can process parts with greater accuracy and speed. 

“With the volume of waterjet cutting that a company like SpaceX is doing, some of their parts are extremely high-accuracy, high-precision parts, which require five-axis cutting,” Kent says. “Other parts are lower-accuracy, sheet-metal-type parts on thinner-gauge material. Instead of tying up the Mach 4 machine with standard sheet metal parts, they have a Mach 2, a Mach 3 and a Mach 4. Based on the type of parts, the accuracy and the end use of the parts, as well as workloads across the different platforms, they can put the parts on the machine that best defines the end use.”

Bringing work in-house

Prior to purchasing the waterjets, SpaceX was outsourcing its cutting, but the company found that method limited its control over timing and quality, especially for parts that required design changes or were cut incorrectly. Bringing the work in-house allowed SpaceX engineers to have more control over the cutting process. “From our experience outsourcing, we knew waterjets and their capabilities. We just wanted more control over the process,” says Cortez. 

Bringing the work in-house improves delivery time and makes it easier to turn around prototypes. “If an aerospace company has a part they want to test, they design it, and then by the time they send it out, wait a couple of weeks, get a quote and wait three weeks for turnaround, it’s a month before they can test,” Kent says. “Whereas, if all the equipment is in-house, you can go from art to part much quicker and have faster turnaround time for a finished design or finished product.” 

Having the equipment in-house also gives companies “tighter control over their processes,” he continues. “They own the part from the initial idea and design stage all the way through finished production.”

Kent says waterjet technology also allows engineers to use some materials that couldn’t be cut otherwise and make “quicker and smaller prototypes, instead of having to cast the finished part or machine it all the way from a giant block. Some of the unique alloys are very expensive per pound, and a waterjet allows them to nest parts together and get better material utilization, saving time and money. 

mm-0513-waterjet-square-image2“They could always cut it with a different method, but a lot of times, there’s a secondary operation to remove the heat-affected zone or remove any areas that have been compromised by whatever cutting process was used,” he continues. “Whereas with the waterjet, since there are no changes to the natural material, they don’t always have to go back and do secondary operations.”

Because SpaceX’s engineers were familiar with waterjet technology, they benefited immediately from bringing the technology in-house. “Because our waterjets are in-house and because [of their] broad capabilities, parts can be designed and manufactured with a turnaround time of the same day or the next,” says Cortez. “Compare that to a two-week or more lead-time we had when we were outsourcing.” MM

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