Common problems with Wire and Cable Harness drawings
By Nancy White, CEO Custom Interface, Inc.

There are three problems that show up repeatedly in wire and cable harness assembly drawings which cause the drawing to have to be reworked, resulting in days or weeks in delays before you receive your First Article. Help your contract manufacturer help you get your harnesses as quickly as possible by following some of these important tips below.

1. Sheet metal drawing templates, which are commonly used for cable assembly drawings, list a standard tolerance that is typically overkill for a wire harness. OEMs don’t want to pay for a cable built to 0.003” length tolerance.
Solution: Custom Interface typically recommends adding a note that states “IPC-A-620 tolerances should be applied to all dimensions unless otherwise noted”.

2. High voltage testing limits are determined by the connector manufacturer. Quite often an engineer will specify a voltage test requirement that exceeds what the manufacturer specifies for a particular connector.
Solution: Custom Interface suggests replacing the testing requirements with a note specifying that the “harness assembly should be tested to the maximum voltage tolerance specified by the connector manufacturer”.

3. It is very difficult to predict which size of heat shrink will work best on the transitions from a wire or cable to a connector.
Solution: Custom Interface suggests specifying the type of heat shrink desired and adding a note stating that “the size of heat shrink should be selected to provide best fit at the point of application”.