Making a detailed drawing of a complex harness?

[vonsteimel]

Greetings,
This is more of a drafting question I suppose, but it fits the electrical bill.

Has anyone seen, know, or have any examples of a detail drawing of a complex electrical harness. In particular one with multiple layers of heat-shrink (or similair) sealing various soldered connections layered over one another?

Just curious as to how others have handled the situation on a drawing. Where you have individual splices that are heat-shrinked, that are then bundled into groups that are heat-shrinked over the top of that, which is then heatshrinked into bigger bundles, that is then all heatshrinked together (in that particular area) and is then covered with a braided loom (in that particular area)....

If that makes any sense...
Not really looking to get into why one would do such a thing, or alternative to heat-shrinking all that, but merely how to sufficiently detail the situation on a drawing when it is encountered.

As of right now, it seems easiest to do it with more of a work instruction, nevertheless there will need to be an end-result [detail] drawing of what is produced.
Thanks,

VS

 

[mcgyvr]

There are numerous examples of wire harness drawings .. (google images with the keyword "harness drawing")..
There is no specific standard for the exact situation you posted that I'm aware of and most of that is "detail it for what works at your company"
This might include a step by step work instruction or multiview drawing,etc...

 

[IRstuff]

Our cable drawings tend to be specific to length and Ys. Connector ends, shielding, terminations, etc., are called out in separate detail views

TTFN
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[MikeHalloran]

The only way I've ever seen it done is with a harness board, basically a plywood wall with a full size blueprint of the entire harness stretched out over it, with strategically placed nails and temporary clamps.

The blueprint comes from the first article harness, which is built on the end product, then laid out on a big table and traced onto vellum.

Subsequent harnesses are built on the harness board, using precut and preterminated and premarked wires and precut lengths of sleeving, split loom, heatshrink, whatever.

There is usually a separate schematic,
and a separate wire list with wire lengths, terminations, and markings, for each and every wire.

I think modern CAD systems claim some ability to help in the process of generating a harness board drawing, but so far I haven't worked for an outfit that would cough up the money for a module like that.


Mike Halloran
Pembroke Pines, FL, USA

 

[mcgyvr]

I think modern CAD systems claim some ability to help in the process of generating a harness board drawing, but so far I haven't worked for an outfit that would cough up the money for a module like that.

We use Autodesk Inventor here (with its "cable/harness/routed systems module") and it has the ability to create what they call a "nailboard" drawing from a harness (but cannot really do a typical large size nailboard like most harness builders would be accustomed to..similar but it lacks many "fancy features" that it should have) with all the wire ends fanned out but it really doesn't include functionality for showing shrinkwrap/loom either.. Just the ability to include those parts as a "virtual component" where its called out in the BOM but not physically shown in the harness. Not my drawing.. but Inventor can create drawings like this from a 3d harness

http://forums.autodesk.com/autodesk/attachments/autodesk/78/272282/1/Sample Nailboard.png

frankly I find the whole tool to be virtually useless.

A multi-view regular 2d autocad drawing showing the harness at the various levels of its assembly process and sketching in the shrink tube is exactly how I would handle the OP's situation. And possibly a few notes on the drawing calling out any specific details that for some reason might not be able to be shown or grasped visually.

 

[VEBill]

Some assembly details might be defined in your company's "Standard Shop Practices" (SSP), or equivalent, documents. The cable assembly drawing might refer to a certain section of the SSP using a simple Note number. The SSP would have detailed sketches showing how to assemble things (e.g. heatshrink) in a company-approved and consistent manner.

The SSP approach can fall apart when combined with outsourcing, unless carefully managed.

 

[racookpe1978]

Why do you think you need to offer this much detail?
The shop doesn't need it.
The 3D graphics department only wants a fancy 3D image to put in the advertising
The final assembly dwg or final 3D assembly image 9for interference or routing purposes doesn't need it.
The BOM doesn't need it.

 

[MikeHalloran]

For a one-off or low production sort of thing, where you're only going to make a few, you can route and terminate the wires and wrap the harness right on/in the product. Don't expect any two to be identical.

If you're making more than a few, then you need considerable detail. The harnesses may be made in a different facility than the end product, so quick fit checks against the end product are not possible. Harnesses may also be sold as service parts to end users, in which case you also have to generate shipping documents and installation instructions.

I've never seen a harness drawing in advertising; they're just too damn ugly, and harnesses are typically omitted from images for advertising, I'm guessing at least because their visual complexity might intimidate a potential customer.



Mike Halloran
Pembroke Pines, FL, USA

 

[VEBill]

"...a complex electrical harness..." is likely to be in a product where the OP can't get away with not defining and documenting the details, perhaps avionics and/or military.

But, I'm reading between the lines.

 

[racookpe1978]

Oh no. I've had to actually "do" 3D CAD routing of electric power and control harnesses in place behind instruments (for Army radar and USN mini-subs) to do three things:

Calculate the cable lengths of each major cable and cable bundle for weight control and CG location.

Maintain the minimum bend ratio of the individual power cables and the final cable bundles, while allowing room for expansion loops behind the consoles so the different individual consoles could still be pulled out of the frames,

Generate the 3D interference zones behind, above, and below each console so other stuff (piping and structure and other bundles) never hit the bundles already laid; and so new bundles could "fold and unfold" themselves without getting entangled in already-laid bundles or already-designed pipes.

And - finally - when changes were made, go back and do it all over again. 8<)

So, "routing" individual cables and cable bundles makes a lot of sense in certain circumstances, but modelling tie-wraps and shrink wrap inside tie-wraps and shrink wrap????

 

[IRstuff]

Modeling diameter makes sense in certain applications. One of our products sits above the rotor on a helo. The standpipe cable is strictly limited to a fixed diameter, and if you can't use the wires, as is, in the existing standpipe, then a new one would have to be designed to point than you can pull about 10 ft of cable through the standpipe. If you're off by a few millimeters, that ain't going to happen.

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[racookpe1978]

Calculating diameter, and diameter clearances? Absolutely.

But Modeling each shrink wrap? Doesn't seem warranted in my experience doing similar work.

 

[vonsteimel]

There is not modeling here. Its AutoCAD...

And just how do you suppose the factory is going to know how to make it? And when someone bundles the wrong wires and causes problems with assembly, or leaves 1 or more layers of heat-shrink off, or does not get them overlapping correctly and it fills with water & cant drain, do I just argue with them about what I "think" it was supposed to be vs how they "think" it used to be?

Its a small mfg company (20 employees or so)... Its all hand-made, no automation. And unfortunately no peg-boards (whatever the harness fixtures are typically called). We make about 2x runs of 30 - 40 harnesses per year give-or-take.

I'm surprised by comments saying it doesn't need documented...? If it doesn't need documented, then it is not important, and if its not important then why do it? Get rid of it and same time and material...?

We have no requirements (govt, military or otherwise) that requires the documentation. It is the factory that requires information about what exactly they are supposed to produce. How else could expect it to be produced as intended?
Thanks,

VS

 

[IRstuff]

If you want cables that are well-behaved and repeatably buildable, then you need drawings as necessary to make that happen. If you claim to be ISO compliant, then there should be documentation on how to build that cable, particularly for new employees that have never done it before.

Various of our cable drawings detail the number of twists per foot for differential signals, how the shields are terminated, etc.

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[IRstuff]

In a few companies, such documentation is even accompanied by videos of an actual assembly being built.

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[mcgyvr]

pfft.. if its just Autocad then start sketching.. draw the shrink tubing and point a balloon to it. copy/create another view.. draw some more tubing and point another balloon to it.
Make a couple views showing each main assembly step..
In autocad its simple as you don't have 3d models that you need to fudge/modify/work around.. Just lines/arcs.

 

[vonsteimel]

I like this IRstuff guy. My thoughts exactly.

We're not ISO, but I have created our own ISO type of standards. I'm in a company that had none of it and all the problems that go along with not having it... and I've been fighting the uphill battle the whole way. Been making good progress with it, but its a little too slow for my liking.

Would you happen to have any examples you could share?

At this point, I'm essentially creating a work instruction, not a drawing.

See the attachment for what I released. (note: half the info has been removed, tolerances, BOM, titleblock.etc)
Thanks,

VS

 

[zappedagain]

We got to the point where for more complex cables we do work instructions in PowerPoint; basically one step per page. We also have a separate inspection drawing for incoming inspection if they get outsourced. The latter shows overall lengths and dimensions (diameter, etc.) as necessary.

Z