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Placeholder empty part - imaginary but present

Question asked by Tom Gagnon on Nov 3, 2016
Latest reply on Feb 27, 2017 by Bill Hanauska

I have one large assembly of 630 parts, and growing. Some of its simpler repetitions are driven by assembly patterns: mirror, circular, or linear as appropriate. As case in point, it has two identical plastic tanks with the same ports and nozzles, supporting structure, and anchoring hardware. Whether this is patterned or subassembly seems irrelevant to the question I'm about to ask, but that remains a mostly semantic alternative for repeated parts.

 

Now, I've added extra details of hardware that the client has asked to show, the tie down anchor cables on the tanks. I've added coated wire rope, turnbuckles, and sleeve clasps as parts for both visualization in drawings to the client and BOM quantity to be used in our purchasing processes. Those parts were either downloaded from McMaster-Carr or modeled for the cable. There was no download available for a small but necessary component, and I do not feel like modeling it because it is rarely used and mostly insignificant.

 

Here's what's different this time. I created an empty virtual part (Insert > Component > New Part). It is a Wire Rope Thimble, which needs purchased, but is visually insignificant at the scale of the drawings. I named it, opened it, defined its custom properties for data propagation to the BOM, then saved and closed it. It has no features, no bodies or mass, and no reference geometry beyond template defaults. I located it logically into the tree's subfolders along with the other hardware mentioned above. Then, I included it into the patterns as if it was included normally with the other associated hardware. What I expect from this is that it will be accurately counted in the BOM, even if pattern quantities change. It won't even require balloon annotation in assembly drawings, because there's only one application for this part and only a handful of those applications present.

 

Clearly, as scale varies among users' designs and organizations, this is not appropriate for all use cases. We have a small design team of users, only two, so communication of exceptions can be handled simply in my case, but I can imagine this potentially wreaking havoc in a larger organization. As a custom OEM, the manufactured quantity of any complete system we design is one or two at most. Also, this particular assembly for us is a very exceptional custom design which will not be reused because of non-standard variations.

 

Does anyone else do this? Which types of parts have you used this way? Are there repercussions to using this shortcut, or will it work simply and stably as I expect? Should I track these objects additionally, such as an exceptions list comment or other indication to other users or for future reference? I'm mostly wondering if this is going to cause problems considering the law of unintended consequences and all. Thanks.

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