Original Date: 08/07/1995
Revision Date: 01/18/2007
Best Practice : Product Proof and Prototype Validation
Lockheed Martin Tactical Aircraft Systems (LMTAS) has developed a Product Proof and Prototype Validation (P3V) process to reduce risks associated with product producibility, quality, cost, and schedule prior to rate production. Ultimately, this process should ensure that the design intent is conveyed in a clear and understandable format to the user and can be manufactured and installed repeatedly on a reliable basis at rate production. The design intent is conveyed through the build-to package which consists of the engineering package, work instructions, production tools, and manufacturing processes. The P3V process is an excellent process for proofing the engineering design prior to formal release. This multifunction process requires management commitment from all functions performing the various tasks.
The most basic element of proofing is the application of a new level of rigor to the "checking" systems. This may include proofing the engineering design, tool designs, and work instructions. It may also include first article inspection and fit checks for component assembly and installation. The proprietary LMTAS software Computer Mock-up (COMOK) and Hard Mock-up are other examples of proofing tools.
Under the P3V process, risk assessments are performed at various stages of the proofing process to evaluate the need for proofing, to forecast the proofing level, and to verify that specified proofing has been accomplished. Information obtained during the initial risk assessment provides input for constructing a critical path schedule that includes proofing activities, verification of a proofed process, and formal release. The scheduled proofing plan is a part of the proposal that is submitted to the customer. Proofing activities continue throughout product development until the final prototype is validated against the formally-released engineering specifications. The parts remain in proof status until the P3V process, first article inspection and installation (fit check) are completed. Significant savings in scrap and rework cost can be obtained by limiting rate production until this process is complete.
In addition to product development, other proofing activities include trial verification installation to proof retrofit kits and engineering evaluation tests for proofing support equipment.
The F-22 program has benefitted from this rigorous process as high-risk component parts are identified and categorized for the P3V process. For suppliers, P3V requirements for high-risk parts are imposed through the purchase order. For in-house manufacturing, P3V requirements have been added to the planning manual in the form of inspection and verification plans. Also, proofing requirements are integrated into the work instructions and planning documentation.
There are several examples of successful P3V application on the F-22 program. For example, titanium bulkheads are large machined forgings measuring 6 feet by 15 feet that are extremely complex to machine with wall thicknesses as thin as 0.050-inch. A typical bulkhead has 3000 to 4000 attributes and, on an average, the supplier-delivered bulkheads had only two or three defects. This is an average yield of greater than 99.5% which is unprecedented for comparable machining processes.
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