Upon completion of a fabricated wire, it is crucial to ensure that each of the wire’s components are suitable for use. Conductor Strand Blocking provides a method to determine if conductor strands of 7-19 count will adhere to each other in the finished wire. This test was developed as a process control test for silver coated copper conductors of MIL-DTL-81381 polyimide insulated wires, but it may be applied to other conductors and insulation types when strand blocking is a potential problem.
For the test, a central section of each wire sample is stripped without kinking or damaging the conductor. The sample is twisted, then untwisted, and then has its ends gently pushed together to create a “bird cage” effect. Non-separated strands are gently probed to examine them for fusing, and unbonded strands are counted. Pass/fail criteria are determined by the minimum number of unbonded pairs as defined in the product specification .