According to a spokesperson for two Raytheon Aircraft manufacturing plants, the facilities are being enhanced from top to bottom. "All key processes conducted at our Wichita, Kansas, plants are being reconfigured into cells to maximize throughput and efficiency. Each year we manufacture and assemble more than 15,000 parts. it is essential that each one is perfect."

The Power of One

"The problem with conventional part manufacturing is the potential for human error," says Bill Jones, a Raytheon Aircraft manager of manufacturing and technical support. "Machining a part out of sheet metal and attaching multiple details onto it. angles, webs, beams, ribs, stiffeners and doublers. creates multiple tolerances. We realized parts like a forward pressure bulkhead can be designed more simply."

This prompted Raytheon Aircraft to investigate high-speed machining for part manufacturing. "High-speed technology allows us to reduce assembly by machining the forward pressure bulkhead from a single piece of billet aluminum," says Jones. "This creates an array of benefits, like eliminating the multiple tolerances associated with each detail and decreasing cycle time, and the bulkhead is more consistent, more accurate and more lightweight."

By examining the conventional approach and the high-speed machining approach to bulkhead manufacturing, the benefits become apparent (see Figure 1.).

Raytheon Aircraft uses a Makino MC1516 high-speed horizontal machining center with a seven pallet modular machining center (MMC) to support this bulkhead application. In two setups, the MC1516 machines thin wall tolerances under .00010 of an inch to near net shape. Roughing and finishing is conducted simultaneously using carbide end mills. Powered by the MC1516. s Jet 50 spindle, these end mills reach 12,500 rpm and achieve metal removal rates as high as 320 cubic inches per minute.

"Part accuracy is impressive," says Bill Ohman, a Raytheon Aircraft machine shop manager. "During installation the bulkheads fit perfectly, eliminating the need to trim and drill the part. Without rivets in the bulkhead, we also have a reduced part count and stronger parts without variation. We can even machine mating parts on the same machine."

"The 15,000 rpm, 50 taper spindle has played a big part in this application," Ohman continues. "It provides horsepower at various ranges and brings a high level of rigidity to this application. With the seven pallet MMC, the spindle is engaged more than 90 percent of the time. The MMC allows us to conduct setup offline and keeps the MC1516 constantlyfed."

Preparation Pays Off

One challenge Raytheon Aircraft foresaw with its modernization was the potential learning curve involved with new technology. The manufacturing team responsible for the bulkhead application worked to ensure the move to high-speed machining was seamless.

"Our team consisted of every discipline involved in the process, from manufacturing engineers to the operator," says Dan Allis, a Raytheon Aircraft equipment engineer. "We wanted to be capable of running production parts immediately and worked with Makino reviewing and optimizing the entire application prior to installation."

During this application review several Raytheon Aircraft programmers also visited Makino. s Los Angeles-based Aerospace Technology Center to apply their programming skills to high-speed techniques. This approach paid off with production parts being machined immediately after installation.

Going Beyond Cut Time

And, while these results are impressive, Raytheon Aircraft quickly realized the efficiencies high-speed machining passed on to the rest of the manufacturing process. "In taking the part down to one piece, we realized a large reduction in labor hours," says Rob Luallen, a Raytheon Aircraft tooling manager. "This allowed us to focus on the application. s offline operations; we consolidated tooling and eliminated other operations. By using simplified, standardized tooling, maintenance decreases and impacts overall part quality and setup time." light chipload. This dynamic behavior requires strong servos to maintain mold contours. To determine how well the servos are tuned, the test follows a circular path in one plane.

Raytheon Aircrafts approach to workholding also impacts setup, using what it refers to as universal vacuum fixturing. While the larger bulkhead is machined on a dedicated fixture, this standardized approach to vacuum fixtures allows operators to set up smaller parts in one operation.

"The fixturing uses back bolts and a large vacuum plate to hold the parts," says Luallen. "The MC1516 first cuts the thinner, more sensitive areas that are more apt to flex away, leaving more material for stability. If there is an angle on the web, it is cut prior to thinning it down. A thin foil web is ultimately cut around the floor of the part. about .0003 inch of material to keep the part attached to the universal fixture. When machining is complete, the vacuum is released and the part is snapped out of the surrounding material."

Ultimately Luallen predicts certain applications could employ vacuum-free fixturing and rely on the material surrounding the part for stability. "This would drive out more fixturing and we would have one less system to rely on," says Luallen.

Making Room For Improvement

This exacting focus on process improvement hasprepared Raytheon Aircraft to meet future demand. A steady flow of new orders has prompted them to consider additional four- and five-axis machine tools.

Additional shopfloor capabilities are also being examined. Using the new DNC communication network, operators will soon be able to view cutter paths at their machines. And manufacturing engineers will be able to view SPC statistics and Cpk values online. All enhancements stemming from a modernization that continue as Raytheon Aircraft makes room for even more improvements.

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