Original Date: 09/15/2003
Revision Date: 01/18/2007
Best Practice : Skip Lot Process
United Defense, L.P. Ground Systems Division Aiken implemented the Skip Lot Process to support its complementary goals of high quality levels, reduced cost, and process ownership by the operators.
With successful implementation of continuous work inspection processes at United Defense, L.P. Ground Systems Division (UDLP GSD) Aiken, traditional quality assurance (QA) sampling techniques based on part cost became redundant and superfluous and did not promote the process ownership goals important to the implementation of modern lean fabrication processes. The company developed the Skip Lot Process to support its complementary goals for high quality levels, reduced cost, and process ownership by the operators. UDLP GSD Aiken benefited from this process by reducing cost/run standard hour, eliminating redundant administrative requirements, reducing inspection time, improving material flow, and maintaining high quality, as measured by scrap and rework performance.
The Skip Lot Process is based on eliminating redundant inspections and unnecessary handling time for work orders on a production lot basis while retaining corrective procedures where needed in the Quality Assurance (QA) process. With final inspection occurring at the workstations, it was possible to ensure quality by periodically auditing the workstation-based process. Workstation audits include monthly verification of the first piece qualification (for each production lot), the calibration of in-use gages, and the drawings and specifications with military standards and weld specifications. To qualify for inclusion in the Skip Lot Process, the production process and operator must be certified, and at least two production lots must be accepted by QA before subsequent production lots become a candidate for the process. When accepted, work orders carry the note “Job on Skip Lot” on the front page. Parts produced under the Skip Lot Process go directly from the workstation to shipping, bypassing the QA lay-down area and improving material flow. Documentation bears the marks of the certified process, operator, and the operator’s inspection sign-off which must be complete before the parts are authorized for shipment. Parts can be removed from the process at any time by quality/manufacturing engineering if the production process is changed or if engineering changes to the part are required. Rejection of any part, by QA or the customer, will automatically cause all such parts to be removed from the Skip Lot Process until three production lots have been accepted by QA.
UDLP GSD Aiken realized many benefits from its Skip Lot process, including: Reduced cost/run standard hour (the standard metric for all manufacturing operations)
Reduced direct inspection costs (with up to a 38% reduction in inspection/manufacturing cost ratio)
Elimination of redundant administrative requirements
Improved material flow
Maintenance of high quality parts (as measured by scrap and rework performance)
Reduced inspection time
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