Visual inspection is the key to 100% functional cables


OEMs rely on strong cable assembly quality control practices because field failures of electrical equipment are far costlier than the cable assemblies themselves.

But we’ve seen  enough cable assemblies that our customers received from previous suppliers to know that many cable assembly manufacturers aren’t performing satisfactory quality control.

Operations that produce cables at extremely high volumes can rely on statistical process analysis to predict defects per million opportunities (DPMO). But building cable assemblies for OEMs means our production volumes aren’t high enough for us to feel comfortable with statistics. We must take more hands-on measures to guarantee cable quality.

A huge piece of the quality control picture is visual inspection. It’s exactly what it sounds like: Someone with expertise examines the cable to make sure everything looks right. This simple step proves invaluable in helping us meet our customers’ standards as well as our own.

How Multi-Tek performs visual cable inspection

The visual inspection process starts at the outset of a project, when we build a first article and confirm with the customer that it’s exactly what they’re looking for. That’s our first step because all future visual inspection leans on detailed pictures of that first perfect cable assembly.

But visual inspection should take place throughout the production process. Too much can go wrong if you assume your equipment was, is and always will be perfect. Knowing that you can produce one perfect cable assembly is much different than confirming you’ve produced 500 perfect ones.

At every workstation on Multi-Tek’s production floor, an iPad contains pictures of the most current revision of every ongoing project. When an operator clocks into a job, they see the images they need to properly inspect their work, as well as the work of other operators.

MTI employee inspecting cable assembly with first article image including notes

Then, before shipping, the QA team gives every cable assembly a final inspection to make sure every last detail looks exactly as the customer asked for it.

How visual inspection complements cable testing

At Multi-Tek, cable testing and QA are two separate departments. We test every cable with Cirris testing equipment prior to a final visual inspection by our QA team. And performing both is crucial.

Just like a QA specialist can’t see the voltage running through a wire, electrical testing equipment can’t tell you whether a cable is properly labeled or whether there’s an issue with insulation that suggest the conductor is poorly protected from future damage.

cable quality testing

To deliver 100% functional cable, therefore, it is crucial that we perform both electrical tests and visual inspections.

And the two departments help each other. Sometimes a failed electrical test doesn’t tell the operator what in particular is wrong with a cable assembly. Sometimes a visual inspection can uncover the source of cable failure, which speeds up the repair and rebuild process.

If a cable tests within acceptable tolerances but with different values than other pieces in its batch, the testing team can flag it. Then the QA team can evaluate that cable with particular attention towards a potential problem.

Where in the manufacturing process visual inspection matters most

It’s not enough to take a good look at cable assemblies only when they’re finished. And this presents the biggest challenge in cable assembly quality control:

The most common failure point in a cable assembly is at the crimp. But the crimp itself isn’t visible on a completed cable assembly — the terminal has already been plugged into the connector.

There are plenty of tools that can test various crimp specs to identify bad crimps. But some crimping errors don’t come down to crimp height, crimp force or connection strength. Wire could be inserted too far into the terminal, or not far enough. Insulation could be caught in the crimp. The list goes on.

good crimp diagram
This diagram of a good crimp comes from an old Molex data sheet.

To evaluate crimp quality, you need to test crimps but also visually inspect them before they are assembled and plugged into connectors. At Multi-Tek, separating different stages of production allows a new set of eyes to inspect the work of the previous department.

After wire is processed and crimped, the assembly team visually inspects the crimp before assembling the cable and sending it for testing. They are the best-placed employees on the floor to evaluate crimp quality, so we empower them to recognize and point out questionable crimps when they see them.

Looking for a custom cable partner with robust quality control processes?

If you’re struggling to trust your current cable assembly supplier to deliver consistent, reliable cable assemblies, or you are looking for a supplier that can guarantee cable functionality on a new project, reach out to us.

We understand what’s at stake if you don’t get what you pay for. If you’re still in the cable design stage, check out our other resources or ask us for some help.