Original Date: 07/25/2005
Revision Date: 09/12/2006
Best Practice : Sheet Metal Manufacturing Capabilities
(equipment: Trumpf Trumatic 500 CNC punch press and Cincinnati Autoform CNC press brake)
By using a concurrent design environment and continuous process improvement, Northrop Grumman Electronic Systems is producing closer tolerance parts than ever before. As a result, improvements in built-up assemblies have led to reduced inspection and testing requirements. Close work with material suppliers and the initiation of a Qualified Manufacturing Line to control processes has resulted in further cost savings and cycle time reductions. By designing on the same equipment as production occurs, Northrop Grumman Electronic Systems ensures sheeting metal manufacturing processes that are feasible and reproducible.
Northrop Grumman Electronic Systems’ design and process development was previously done by a “toss-it-over-the- wall approach.” Engineering designed a product and “tossed” the design to production. Production looked at the design and pointed out those aspects of the design that could not be produced and “tossed” it back to engineering, only to have the cycle repeated until a design desirable to both groups was finally agreed upon.
Production is currently assisting the design process by identifying current process capabilities as well as intended future improvements. This formalized manufacturing capability data has been published as design guidelines that includes information on tolerances and desired hole sizes and their placement in sheet metal assemblies. The development of a concurrent design and process allows the production of parts that are held to 2- to 5-mils accuracy versus the previous standard of 10- to 20-mils accuracy. These close tolerance parts are now developed as prototypes in the production environment, eliminating a step in the startup cycle.
Assemblies are built up from close tolerance components and are sufficiently joined to eliminate the time-consuming and costly process of match drilling. Test results qualify these assemblies for skip-lot testing of one unit out of five (a 20 % sampling), eliminating weeks of testing and associated transport costs. Further productivity improvements at the component level have been achieved by working with material suppliers to produce raw shapes to near net size. Parts are now delivered from material suppliers and presented to the machine operator in the sequence desired for just-in-time build.
Test coupons are now produced on a daily basis before parts are made, providing characteristic data on a handful of key features to ensure that a process is capable of producing the desired results. This proactive approach to quality has resulted in a Qualified Manufacturing Line (QML) where machine operators decide to either run production based on qualifying results or to shut the process down and implement a QML team action if required.
NGES’ practice of designing on the same equipment as production occurs has created sheet metal manufacturing processes that are feasible and reproducible and meet demanding customer needs, resulting in reduced build cycle times for sheet metal assemblies and reduced production costs.
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