Wire harnesses and looms are used everywhere in connecting electrical and electronic equipment, from aerospace to domestic machines. Whilst some are power conductors, many are signalling, connecting electronic controls and components. Predesigned for easy fitting, most are pre-bound and assembled with a variety of push-on connectors, and may include permanent splices. This enables rapid assembly in mass production lines, and complete electrical pre-testing of all connectors.

Application

The only way of really knowing the strength of a crimped terminal is to pull it. This can reveal production problems, where strand nicks, incorrect crimp height, or effects from changes in terminal supply, may not be clearly apparent. Assembling tensile test data in statistical process control (SPC) systems will also alert for tooling tolerance drift.

In design phases, it can also be valuable to see not just at what force a crimped joint fails, but the manner in which it fails. Strands can begin to break, a connector itself may deform and break, the whole conductor may break, or slip or pull out of the crimped barrel. Any elongation in the wire tail must not be construed as slippage in the joint. Factors such as these can be identified on a full force-time trace using our programmable tensile testers, as part of the development of jointing specifications.

Testing

At Mecmesin we offer a range of equipment for performing tensile testing on crimped wire terminals. Machine selection is dependent on the force capacity required, the amount of testing being done, and where.

When it comes to quality control, motorised pull testers are key to improving the accuracy of tensile test data by eliminating operator variants; as well as reducing operator strain and injury.

Our small, horizontal bench-mounted tester can apply a force of up to 1 kN, allowing operators to insert single wires quickly for rapid-throughput, safely pulling samples away from the user. A single button press runs a test, and just 4 multi-function buttons for all settings, operation and output to an RS232 statistical printer.

Peak force at break is displayed along with clear pass and fail indication. Four speed settings are available: 25, 50, 100 and 200 mm/min. to comply with all regular test standards. This makes our CrimpTest-1 kN a high-reliability everyday tester, requiring minimal training and maintenance.

Standard methods

The CrimpTest-1 has versatile fixtures for pull testing crimped, soldered or welded terminals, and cable ties, to 1 kN:

  • slotted rotary crimp receptacle with stepped loop pin (standard)
  • self-tightening cam grip (standard)
  • wedge grips for flat or round terminals (optional)
  • cable tie fixture (optional)

Applicable international test standards:

  • ASTM B913 : Standard test method for evaluation of crimped electrical connections to 16-gauge and smaller diameter stranded and solid conductors
  • SAE AS39029 and AS7928 : general specification for terminals, lug: splices, conductor: crimp style, copper
  • IEC 60352-2 : solderless crimped connections
  • BS 5G 178 (Part 1) : crimped joints for aircraft electrical cables and wires
  • DEF STAN 59-71 : crimped electrical connectors for copper conductors
  • ISO 1966 : crimped joints for aircraft electrical cables
  • NASA-STD-8739.4 : space applications, crimping, cabling and harnessing

For more information: http://www.mecmesin.com/crimptest-1