Flex Testing

Actual flex-life testing is performed at Northwire to prove designs and is an ongoing activity. The flex test protocol has been standardized over the years and is known as the Northwire Standardized Flex Test Protocol (NSFTP). Flex-life testing is performed to prove new designs, to improve existing designs and to evaluate new materials and constructions.

There are now two test protocols in use:

1. "Mode A" the Tick-Tock Bending Test

The cable is flexed 180° over Nylon blocks that have a 3” radius. The conductors in the cable are daisy-chained together and the continuity of all conductors is monitored continually. A fault in any conductor will stop the tester. There is 1 lb. of weight hanging on the cable as it is flexed. The tester runs at a rate of just under 30 cycles per minute or a little over 40,000 cycles per day. (One cycle is a 90° bend in each direction)

2. "Mode B", the Rolling/Torsion Flex Test

The cable is pulled approximately 18” over a 3” radius wheel and twisted 360°. All of the twisting takes place in the 18” between the grip and the wheel. There is a 9 lb. weight hanging on the cable as it is twisted. The amount of weight is determined by the size of the cable and inner conductors. (The machine pulls it up and gravity pulls it back down. As above the conductors are chained together and continuity is continually monitored. The speed is the same as above. (One cycle is one up and one down stroke resulting in two 360° twists)