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The Hyper-X program is a fast track project that requires the implementation of timesaving concurrent design and manufacturing techniques
When the National Aeronautics and Space Administration's experimental X-43 Hyper-X aircraft flies later this year, it will mark an important advance in engine and aircraft technology. That historic flight will be the first time a non-rocket engine will power a vehicle in flight at hypersonic speeds–speeds above Mach 5, equivalent to about one mile per second or approximately 3600 miles per hour at sea level. Actually, the target test speed for the first flight is Mach 7, over 5000 miles per hour.
NASA plans to extend the flight range of this airframe-integrated, air-breathing "scramjet" (supersonic-combustion ramjet) engine to Mach 10, approximately 7200 mph at sea level. The goal is to demonstrate the feasibility of using air-breathing engine technologies for vehicles ranging from hypersonic aircraft to reusable space launchers. The contract for flight and ground research hardware is being implemented for NASA by a team led by Micro Craft, Inc., Tullahoma, Tennessee. In addition to program management, Micro Craft (working with teammates Boeing and GASL) is responsible for fabrication and flight test support.
The Hyper-X program is a fast track project that requires the implementation of timesaving concurrent design and manufacturing techniques to develop rapid prototype test articles and meet very demanding schedule constraints–a difficult combination of objectives that the company has successfully met since its founding in 1958. To augment its production capabilities for the X-43 program, as well as work on the Space Station Project and the Delta Rocket program, Micro Craft has added three Cincinnati Machine Sabre® Vertical Machining Centers and a Lancer® VMC-1250 Vertical Machining Center to its extensive machine tool inventory.
"The VMC's have helped us improve our speed and feedrates," said Jim Herron, Operations Manager at Micro Craft's Tullahoma site, "and we've also seen a significant improvement in productivity and reduced rework."
The Sabre machines are used to cut aluminum brackets that will be used to hold the X-43's fuel tanks in place and brackets used to hold connectors for computer systems and avionics devices.
A typical machining cycle on the Sabre machine takes a little less than half an hour to rough the aluminum billet to near net shape, and then approximately two hours to machine the remainder of the part.
"Because the parts have extremely intricate contours, we have a lot of tool changes during a typical machining cycle and that's why the cycle seems long, although it's about half of what it was with other machines." The installation of the Sabre machines helped Micro Craft increase feedrates about three times, from approximately 100" per minute to about 300" per minute, and has helped improve the surface finish of the parts. "We're getting close to 64 RMS straight off the machines. We're doing a 0.0002" scallop height and just touching them with sandpaper. In the past, we had to file them off," Herron said.
He added that, with the addition of the Cincinnati™ VMCs, the shop has been able to run 600 KB programs now. Before the new controllers, they were not able to load a 50 KB program into the other machines. "That's been a major change. We're also able to simultaneously edit programs, so there is a lot less downtime than before," he said.
The biggest gain in productivity has come with the use of a Renishaw MP700 surface-sensing probe on the machines. "Using the probe, we've had less than two hours of rework per each 1000 hours of cut time. We just didn't expect that kind of improvement," Herron said.
Bringing Parts Back Home The increased speed and related cycle time improvements have allowed Micro Craft to bring parts back in-house that it formerly sub-contracted to local vendors. Those parts, the smaller aluminum pieces, represent about 25-30 percent of Micro Craft's current workload.
"Before we improved our cycle times, we struggled to compete against lower outside contractor labor rates," Herron said. "We're now able to produce parts for less cost because we've cut our cycle times by half when compared to our vendors' cycle times. Our vendors often can't compete with us anymore."
Cells Keep Parts Moving Smoothly Micro Craft has arranged its three Sabre machines in a horseshoe-shaped cell to share tooling and move workpieces easily from one machine to the next without incurring excessive downtime. One of the Sabre machines in the cell is equipped with a fourth axis for circular parts, or parts that require machining on four sides and would require four separate setups.
Herron said he believes the cell configuration saves anywhere from 10-15 percent downtime because it has eliminated the need to chase tooling.
"Plus, the cell lets us micro manage a bit," he said. "If the program manager sees a part waiting that should be working, he can make a change then, on the spot."
The Lancer VMC-1250 is used at Micro Craft to machine steel wind tunnel models and prototype space flight hardware.
The Lancer machine, like the Sabre VMCs, is equipped with the Cincinnati A2100, a high performance, multi-tasking CNC that incorporates a dual-processor with industry-standard PC technology. The software operates on a Windows NT platform which allows it to run a variety of related programs, such as Microsoft Word, so that quality personnel, production schedulers and managers can easily exchange information.
Micro Craft operates 12 engineering and manufacturing sites around the country and there is frequently need for the sites to work together to meet program milestone dates. The optional Ethernet/TCP/IP connectivity allows for direct communication between two or more A2100 controls or any Micro Craft network computer or peripheral. Some information is now transferred across the Internet to the A2100's.
What's next for Micro Craft? No one is saying. "We work on advanced research projects that the public might not see for 10 to 20 years." Herron said. "What I can say is that this is the most exciting kind of manufacturing there