3.4 Cable and Wire Harnessing

Wire Processing: Cut, Strip, and Terminate

The process begins with the automated preparation of individual wires.

Cut and Strip: Programmable machines cut wires to length and strip insulation with sub-millimeter precision.
Defect Control: A critical failure mode is "nicked strands." If the stripping blade cuts into the copper conductor, the wire's current-carrying capacity is reduced, creating a hotspot.
Crimping: A press applies tons of force to deform a metal terminal around the wire strands. This creates a "gas-tight" cold weld, ensuring electrical continuity that will not degrade over time due to oxidation.

Harnesses are built on full-scale wooden or plastic templates known as Form Boards (or Jig Boards).

Physical Layout: Pegs and guides on the board dictate the exact routing, breakout points, and length of the bundle. Operators lay wires manually, ensuring the harness mimics the 3D geometry of the final enclosure.
Lacing and Bundling: Wires are secured using cable ties, wax lacing cord, or heat-shrink tubing to maintain shape and provide strain relief.

Validation of a harness is twofold: structural integrity and electrical mapping.

Pull Force Testing: A destructive test performed on sample crimps. The terminal is pulled until it separates from the wire. The force required to break it must exceed values specified in IPC/WHMA-A-620 standards.
Cirris/Continuity Test: An automated tester checks for continuity (open circuits) and isolation (short circuits). Every pin is electrically verified against the netlist to ensure no wires are crossed.