cable tolerances

[zappedagain]

I have a cable that is called out as 5.50" long, with our standard title block stating the standard tolerance for two digits is 0.01 (5.50+/-0.01").

When my QC inspects the cables I told them that +/-0.25" is acceptable for this cable. Is there a standard for cabling to define the design tolerance and the acceptance tolerance, or should I not be so hard on my shop? If not, what standard should I hold them to for an industrial application?

John D

 

[MacGyverS2000]

The standard is whatever you make it. The only time cable length really comes into play would be when you're dealing with time-of-flight stuff (e.g., antennas, delay networks, etc.). You may set certain conditions on length to, for example, prevent rack equipment from getting mired in a mass of cables, but that's usually a tolerance of a couple of inches.

If you force them to reach 10mil tolerances on cabling, you would need to specify if that includes the end of the connectors, just the shielded portion, etc. Also expect some seriously disgruntled workers short-changing you on a random cable, like cutting the shield back too far waiting for a break to happen in the field, etc.


Dan - Owner

http://www.Hi-TecDesigns.com

 

[VEBill]

One approach is to draw the preparation steps.

First view would show the raw cable, cut to length, stripped and prepared ends. This could easily have ±0.25-inch tolerance on the overall length (as assembly guidance, not a QA requirement). Then show the final product with slightly wider tolerances such as ±0.50-inch (a QA requirement).

You might need to put a diagonal line through the default tolerances in the title block of your drawing, unless there's already a "unless otherwise indicated" note.

 

[zappedagain]

That two stage approach seems the simplest. My ex-QC engineer suggested just adding an O.A.L. = #.#" (overall length) note in the corner of the drawing. That works well for drawings where the cable is cut to one length but the OAL is different because the connectors extend off the ends.

John D