Coaching children’s recreational league basketball when my kids were growing up was

very rewarding—even if it was more like herding cats than playing actual basketball. There

is one thing that stands out in my mind, however, and that was when a play worked the way

we designed it. We first diagramed the play out for the kids, and then we practiced it

until they understood the moves. When it finally came together in a game, it was a

beautiful thing to see.

Today, as I work with wire harnesses that are built

for electronic devices, I am reminded of those days coaching the kids on how to put the

play together. First, the wire harness specifications are drawn up in the same way we would

diagram the play. Then, the harness is meticulously laid out, just as we demonstrated to

the kids how to execute the play. There’s a lot more to the process of course, and

thankfully, the wire harnesses usually don’t talk back to us. Here are more details of the

PCB wiring harness manufacturing

process that your contract manufacturer should go through when building your assemblies.

Input: What Your CM Needs for the Wire Harness Manufacturing Process

Contract manufacturers often build both flat ribbon cable assemblies and wire harnesses. To distinguish between

the two, a multicore cable assembly is

an external connection to devices and will have different environmental considerations,

such as their thickness, insulation type, and flexibility. A wire harness, on the other

hand, will provide the connectivity between systems in an electromechanical assembly, such

as connecting a power supply to a motherboard.

Wire harnesses are laid out and built on a panel that has pegs positioned strategically

where the wires will branch out into different directions, or connectors need to be added.

This way, the harness is laid out to the exact dimensions that are required. Usually, you

specify these dimensions, and contract manufacturers are used to getting a wide range of

information to work with. The information can be something as simple as a hand-drawn note,

or a series of complex 3D CAD models, as well as everything in between.

However, as with anything that is manufactured, the more detailed documentation and

precise specifications you can provide, the fewer problems there will be on the assembly

floor. Here is a sampling of the data that will best help your contract manufacturer when

building your wire harness:

Detailed connectors images that show pin locations.

Wire lists that specify wire colors, nets, and connector pin-outs.

Bill of materials with part numbers.

Full assembly drawing with label locations, assembly instructions and tolerances.

Finished harness test specifications.

Key Points of the Manufacturing Process to Build Your Wire Harness

With the documentation in hand, you should expect your contract manufacturer to follow

a general process in building your wire cable harness assembly:

Design review: First off, your CM will examine your bill of materials and other

documentation to make sure that everything they need is in place. They will also evaluate

your specified parts to see if those are the best choices due to cost, availability, and

performance. If not, they will search for available replacements.

Materials preparation: Once the bill of materials is finalized, the CM will next

purchase the components and materials needed for production and test of the harness.

Assembly documentation: At the same time as procurement, the CM will be creating

assembly documentation for the manufacturing floor based on your input. This will include

detailed assembly steps, images and illustrations, and test procedures. Additionally, the

assembly panel will be created with all the necessary pegs set at the specified locations.

Wire harness production: Now, the harness will be built. The assembly technicians will

cut the PVC insulated wires to

length, and lay it out on the assembly panel according to the build instructions.

Connectors will be added, bundles of wires will be tied together, and labels will be

attached.

QA: Once completed, the wire harness will go through the testing that has been prepared

for it to check continuity. The harness will also be checked for construction and labeling,

and tested for fit if the system that it is intended for is on-site.

The building of your wire harness is a pretty straightforward operation, but there are

some details you should be aware of to help to speed the assembly through manufacturing.

The Dos and Don’ts of Having Your Wire Harness Built

The component manufacturer usually provides termination recommendations for how the

high temperature wires should be

attached. Be sure, then, to use those recommendations—such as stripped and bare or

stripped and tinned—as that is what the component is built for. The same goes for torque

values on fasteners, in which you should also use the manufacturer’s recommended values.

You should also provide generic specifications for wires, such as 300V or 600V, instead

of a specific UL code. This gives the CM the flexibility to use what works best for the

harness requirements that is also readily available and cost the least. Specific UL-coded

wire may not be essential for the harness and instead could turn out to be difficult to

find or expensive to use.