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Should cables with crimp connections be pull tested before leaving the Factory?

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No one should ever have to experience wires coming loose and pulling out of their crimp terminals.

While pull testing is a mandatory step in the set up portion of the manufacturing process, it is a destructive test and is not intended for production testing.

To insure that wires stay put, several steps must take place before production begins.

Crimp contacts have a pull force range, a Crimp height range, and an Insulation Crimp height range specified by the manufacturer.  It is the responsibly of the assembler to verify that the specifications will be met by test and validation during the job set up.

To do this the assembler takes the wire, crimp terminal and tooling (hand or automated crimper) that are for the specific job at hand and crimps a test lot.  The test lot is then measured for crimp and insulation height and finally pull tested using a crimp pull tester with a telltale gauge.

Results are recorded and compared with the manufactures parameters.  If all measurements are within spec the cable is then released to production.

If the test identifies any condition where the spec is not achieved adjustments are made to tooling and tests are repeated until the spec is met.

This insures that all cables made with the specified wire, crimp terminals and tooling will not pull out in the field.

 

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Can I save money by switching from Gold plated contacts in my cable connectors to Tin plated contacts?

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Before you can make that decision you have to look at the trade offs between the virtues of the two materials. While Tin plated contacts can be up to 4 times cheaper than the same contact plated in gold there are issues to consider regarding mating cycles, conductivity and resistance to oxidation.

Gold is very durable. Gold contacts can be mated and unmated many more times before degrading to the base metal than the same connector using Tin plating.

Gold is also very resistant to corrosion; Tin on the other hand is very susceptible to corroding over time due to environmental conditions (high humidity, direct exposure to wet conditions especially salty wet conditions).

Tin is also subject to a process called Fretting. Fretting occurs in environments where mechanical vibrations cause small movements between the connectors surfaces or where expansion and contraction through temperature is present. The Fretting process can wear down the Tin contact surface over time and expose the base metal, which is even more prone to oxidation.

Tin can also be subject to galvanic corrosion. If a tin contact is mated to a dissimilar type of contact material (usually gold) as current flows across the surfaces metallic oxides can form at that union. These oxides have a relatively high resistance, which can degrade current flow.

Gold also has a lower contact resistance than Tin. Gold has a mated maximum contact resistance expectation of 20 milliohms whereas Tin is 50 milliohms.

So how do you chose if you should switch from Gold to Tin plating on cable contacts?

If you go down this checklist and you can check all of these boxes you should be ok with the switch from Gold to Tin if the Cable Connectors will:

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*have a low number of lifetime mating cycles

*be used in a relatively Dry Environment.

*be free from continuous mechanical vibration

*be free from extreme temperature swings

* be mated to a similar (Tin) plated contacts

*operate above 50milliohm threshold

Should Cables be 100% tested before they leave the factory?

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In any cable manufacturing endeavor consistency in all aspects of the process is key but it is not a means to an end in itself.  Along with 100% consistency in process you must have validation of the process by a comprehensive testing methodology.

That means every cable gets tested 100% before it can be signed off to ship.  For some cables that means testing at the final step of QC but for others it also includes in-process testing.  Some complex harnesses may have several electrical tests before they reach their final test.

As you’d imagine the testing methodology you choose is as important as the choice to test.  Not all testing is alike and not all methods guarantee a proper working cable.

You can test all cables 100% for continuity (shorts and opens) but that doesn’t insure a proper pin-out.  You can have continuity but at what resistance level?

At PSC we’ve chosen the industry gold standard Cirris Systems CR Easy Wire Tester.

https://www.cirris.com/products/testers/item/8-cr

The Cirris CR allows up to 32,000 test points, resistance threshold can be set from 0.1 Ohm to 500k Ohm.  The CR tests resistors, diodes and capacitors.  It will test in process and at final QC.

The Cirris CR “learns” from a “golden” cable and stores each cables characteristic by a unique filename.  Operators are alerted to cable pass/fail status by audible tone and Pass (Green) and Fail (Red) notifications on their PC’s when performing tests.

What I like best is its test reporting features.  For some of customers, we serialize each cable and provide test reports with each cable.  Soft copy test results are archived on all results and can be called up at anytime.

It’s a powerful way to test and it get’s you the cable you want each and every time!