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Making sense of defense.

Defense manufacturers are increasingly eliminating in-house capabilities and depending on subcontractors to handle product development and manufacturing. One contract manufacturer with full-service capabilities is Tolo Inc, Santa Ana, CA.

An example of the company's capabilities is its work with Hughes Electro Optical Operations, a division of Hughes Aircraft Corp, on development and manufacturing of forward-looking infrared (FLIR) targeting pods for the Navy's F/A-18 Hornet aircraft. The pod assembly is composed of numerous materials, including wrought and cast aluminum alloys; titanium forgings, plate, and rod; fiberglass-reinforced epoxy composites; silicone rubber seals and wiring harnesses; structural adhesives; polysulfide sealants; and aluminum honeycomb core.

The array of advanced materials in the pod made cutting complex shapes difficult. Among the tools Tolo used is an abrasive waterjet system with seven-axis robotic control. The system quickly cuts complex shapes to final size and minimizes tooling costs. A CNC laser was employed to cut openings in the forged titanium inner and outer roll housings that contain the pod's sensitive electronic components.

Installation of the roll housing bearing was one of the most demanding parts of manufacturing. The stationary outer roll housing protects the sensitive inner components of the pod and is exposed to a range of service temperatures that result in thermal expansion and contraction. The inner roll housing rotates on bearings and maintains a relatively constant temperature and dimensional stability. Highly preloading the bearings to offset the dimensional differences between the two housings eliminated axial end play under all operating temperature conditions.

Tolo also fabricated the blade seal used to secure the pod perimeter to the aircraft fuselage. The seal is composed of silicone rubber reinforced with Dacron fabric and stiffened with co-cured, polyester-impregnated glass fabric. A low-friction fabric is applied to the seal surface that contacts the aircraft's skin.

Throughout assembly, Tolo technicians measured the roll housing assembly, the bearing preload torques, axial end play, roll housing breakaway torque, and running torque to guarantee satisfactory operation. They then tested the assembly to assure it met the project's specifications.

The company also built a master fixture to machine the pod's four attach surfaces and mounting holes on one machine. Dimensional tolerances on the pod mounting surface were |+ or -~0.001", with angularity tolerance of |+ or -~4 minutes and hole location within |+ or -~0.001". All drilling, reaming, surfacing, counterboring, and broaching operations were performed with the roll housing held in the correct aircraft/pod attitude. Normally this operation would involve using a jig bore machine to position the part in each critical position one step at a time.

Throughout the project, Tolo used such Statistical Process Control (SPC) software to help ensure quality. By using the software to quantify dimensional variations on the pod and its fixtures, engineers were able to precisely match tolerances on bearings and other critical subassemblies.

All work on the pod was completed in just eleven months, seven months ahead of schedule. The pods currently are undergoing flight testing at the Naval Air Warfare Center, China Lake, CA.

For more information from Tolo Inc, Santa Ana, CA, circle 363.
COPYRIGHT 1992 Nelson Publishing
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Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Manufacturing Solutions; defense manufacturers' reduction of of in-house capabilities and reliance on sub-contractors
Publication:Tooling & Production
Date:Oct 1, 1992
Words:509
Previous Article:Probing into quality.
Next Article:Packaging protection for precision parts.
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