REG NASA-LLIS-0433-1996 Lessons Learned Voyager - Power Subsystem Power Distribution Flight Relay Procurement (~1975).pdf

1、Lessons Learned Entry: 0433Lesson Info:a71 Lesson Number: 0433a71 Lesson Date: 1996-07-17a71 Submitting Organization: JPLa71 Submitted by: J.A. RobertsSubject: Voyager - Power Subsystem Power Distribution Flight Relay Procurement (1975) Abstract: Voyagers discovery of defective component lots in wel

2、ded module assemblies led to a re-procurement of the flight relays. For procurement of parts with a prior history of problem/failures, evaluate the design and workmanship of the current production and determine the need for JPL inspections and special screening tests.Description of Driving Event: (R

3、elevant Historical Lesson(s) Learned)During flight welded module fabrication (2) 3SBM relay failures occurred. One relay failed due to a shorted coil, the other failure was due to a broken weld. Subsequent JPL failure analysis on (14) additional flight relays showed failed conditions in one or more

4、of the armature positioning welds.An investigative team visited the vendor to review the failures and the relay manufacturing process/Quality Assurance (QA) controls. The welding process suffered from a component “fit“ problem, worn welding fixtures and an absence of weld schedules. The coil lead op

5、eration had no instructions that precluded the possibility of coil shorts. The QA coverage lacked a systematic method of keeping records and employing corrective action.Based on the deficiencies found in the manufacturing process and the inability to cull defective relays in a non-destructing manner

6、 from the existing flight lots, a re-procurement of flight relays was initiated. The modifications to the fabrication process include: (a) component part inspection prior to kitting, (b) development of weld schedules and weld inspection criteria, and (c) JPL inspection points established at critical

7、 stages of relay fabrication.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NOTE: This component was selected from the JPL Preferred Parts List.Additional Keyword(s): Wire WeldingReference(s):PARs 36074, 36841, 36861; Part Failure analysis Reports 2

8、494, 2496, 2603, 2622; IOM #342-76-B-028, Johnson, H. L., “Disposition and Status of MJS77 Power Subsystem 3SBM Relay Problems,“ 5 February 1976.Lesson(s) Learned: The discovery of defective component lots in welded module assemblies or at any point subsequent to completion of flight hardware fabric

9、ation results in major program impacts. There are unavoidable schedule slips due to the re-procurement and replacement of parts and welded modules. Flight hardware quality is jeopardized by the resulting rework and retest effort.The pre-cap visual inspection alone on a densely packed relay provides

10、little insight into the quality of its individual subassemblies. Screening tests are not 100% effective in elimination of defective units.Recommendation(s): Procurement of parts with a prior history of problem/failures should be specifically re-evaluated prior to re-use on a subsequent flight progra

11、m. Both design and workmanship of the current production output should be evaluated to establish the quality of the product and the critical points in the manufacturing process where JPL inspections should be negotiated into the purchase order. Special screening tests and/or additional special burn-

12、in tests may also be warranted.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Parts Materials & Processesa71 Test & VerificationAdditional Info: Approval Info: a71 Approval Date: 1996-03-07a71 Approval Name: Carol Dumaina71 Approval Organization: 125-204a71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-