NASA-LLIS-0465 : Lessons Learned - Crimped Electrical Connections - Scout Program

سازمان: NASA - National Aeronautics and Space Administration (NASA)

کلید واژه: Hardware , Parts Materials & Processes

سال: 1995

زبان: English

قیمت: 7500 تومان


Description of Driving Event:
Functional failures were attributed to varying resistance values through crimped electrical connections (contacts, splices, terminals). The variation was from several milliohms to open circuits. Microscopic examination of the cross-section of the crimped area revealed either insufficient crimping or excessive deformation of the wire strands.
Samples of the various combinations of crimp connections (connector pins, connector sockets, terminal lugs, or splices) and wire gauges were made using various crimp tools and settings. Crosssectioning of these samples indicated that the manufacturers' recommended settings and positioners did not always provide the best crimp conditions. Pull test results on similar crimp connections correlated with the cross-section conclusions.
In 1975 the Scout Program established its own crimping standard, which specified the crimp tool model, contact positioner, and setting (if applicable) for each connection type (manufacturer and part number), single or double leads, and stranded wire gauge. Crimping on solid buss wire was not considered acceptable. All applicable personnel were trained and certified on crimping and assembling contacts on connectors.
Each day a specific crimp tool (serial number, model) was used, two samples of the specific anticipated combination (contact part number, wire gauge(s)) were made and each sample was subjected to a pull test. Both samples had to meet the established pull test requirements, which were based on the wire gauge capability. After meeting the pull test, the production hardware contacts were crimped. If a sample failed, then the tool was rejected per established procedures.
Similar crimp contact controls have been imposed on applicable vendors and subcontractors.