Original Date: 05/08/1995
Revision Date: 01/18/2007
Best Practice : Low Rate Expandable Tooling
A new concept being applied in McDonnell Douglas Aerospace (MDA)-St. Louis in the F/A-18 E/F assembly process is Low Rate Expandable Tooling (LRET) that reduces the total number of tools required to assemble a major aircraft assembly at a low production rate. This approach offers many advantages over conventional assembly where subassembly tools feed a sequential assembly process. MDA-St. Louis is using the LRET approach on the F/A-18 E/F forward fuselage and wing assemblies, and MDA’s partner for this aircraft, Northrop, is also using the approach on the center barrel and vertical fin assemblies.
The LRET concept calls for fabrication of a small number of large mainframe assembly jigs and a larger number of assembly locator tools, referred to as Assembly Jig Accessories. These removable Assembly Jig Accessories are used to locate primary aircraft structures when pinned to a mainframe jig, and are designed to be interchangeable with mainframe jigs. This concept minimizes duplicate tooling requirements. In addition, the practice of locating the Assembly Jig Accessory (AJA) tools to the mainframe provides the added benefit of reduced tolerance build-up, reduction in jig lock caused by part shortages, and improved quality.
As in the F/A-18 E/F program, developmental flight test programs typically result in minor aircraft configuration changes that drive corresponding changes to assembly tooling. A reduction in tooling rework is anticipated since minimum tooling is required for the Engineering and Manufacturing Development phase of the F/A-18 E/F acquisition program and the Assembly Jig Accessories are removable. With over two years of hands-on experience with the LRET approach, MDA-St. Louis has thoroughly addressed manpower loading, impact of late parts, and the quality of the assembly produced through successful aircraft splice.
To date, the LRET approach has been used to assemble four F/A-18 E/F aircraft and is performing well above MDA- St. Louis’ expectations with a 21% savings reported in up-front tooling costs.
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