Electrical Cable Harness Quality Control - Sampling Plan for Pull Test

[LesPiles]

Hello,


I need help. We do manufacturing of electrical cable harnesses (wire approx. AWG 16) and since we have had problems, we must do a pull test.

We have had 2-3 NC at customer sites. This was considered as a major NC.

I'm not an expert in pull tests but I know there are 3 standards : UL, MIL, and another. Since I have many other problems to resolve, I haven't found time yet to look at those .

We build the harnesses either by using a machine, and also with hand tool.

Question is : From the starting point that I know I have to do pull test, when, how and how much must I test ?

I plan to have a mechanical counter installed on a crimping machine and from this point, to test at the beginning of a lot, a few crimps after, in the middle of the lot, and at the end. Quite easy for automatic operation.

How can I control for the manual crimping operation ? Does someone has an example of log sheet ? Are those standards talk about monitoring ?
Idea I received is from store, when operator is picking its materials (crimps) to assemble the harness, we should issue some sheet to log at different intervals ...

Or we use SPC in a more traditionnal way e.g. we test one per x crimps that has been done ?

What should be the interval ? the method ? Major question is : for the manual operation, how will I be sure that operator really does its testing at the "correct" (predetermined) set interval ?

I'm surely not the only one that is facing this issue !

Thank you in advance for all your help !

 

[harry]

Check the discussions in this thread, especially the spreadsheet from Bev: Sampling Plan for Final Inspection and Process Verification

 

[somashekar]

Hello,


I need help. We do manufacturing of electrical cable harnesses (wire approx. AWG 16) and since we have had problems, we must do a pull test.

We have had 2-3 NC at customer sites. This was considered as a major NC.

I'm not an expert in pull tests but I know there are 3 standards : UL, MIL, and another. Since I have many other problems to resolve, I haven't found time yet to look at those .

We build the harnesses either by using a machine, and also with hand tool.

Question is : From the starting point that I know I have to do pull test, when, how and how much must I test ?

I plan to have a mechanical counter installed on a crimping machine and from this point, to test at the beginning of a lot, a few crimps after, in the middle of the lot, and at the end. Quite easy for automatic operation.

How can I control for the manual crimping operation ? Does someone has an example of log sheet ? Are those standards talk about monitoring ?
Idea I received is from store, when operator is picking its materials (crimps) to assemble the harness, we should issue some sheet to log at different intervals ...

Or we use SPC in a more traditionnal way e.g. we test one per x crimps that has been done ?

What should be the interval ? the method ? Major question is : for the manual operation, how will I be sure that operator really does its testing at the "correct" (predetermined) set interval ?

I'm surely not the only one that is facing this issue !

Thank you in advance for all your help !

Pull test is destructive.
Even if it passes, the tested item is not taken as good for use.
At begining, end and at periodic intervals, and when any setting or material or run change is made., you can do a pull test, find if it pass, discard it and continue crimping.
It is a validation test sample to be excluded from batch after whatever is the result.
If it seems there is a variation in your setting over a run, identify this and correct the machine / hand tool insert / replace handtool. Try to make bundles of small lot like 100's and identify the last piece of each bundle for the pull test to decide on that bundle, and to begin the next batch of 100. When consistency and confidence is built, do a skip lot.

 

[AgnieszkaSz]

Hallo,

the pull test is not a definite one. The non-destructive test is the measurement of crimp height. You can find the desired value of crimp height in the specification of the terminal you use. Besides, there is the visual control - you can find the criteria for example in Tyco prospect or you can use the the IPC standard 620 (I don't remeber its full number but 620 it is for sure). Combine this with pull test for beginning and end of the batch. Besides, for machine crimping, introduce the review of applicator, say, every 40.000 crimps - you can measure 100 crimps and analyse the Cpk then.
Hope this helps a bit.

 

[somashekar]

Also have a look at 'Understanding crimping' in this post attachment list search.