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Including document numbers in dash-number part numbering scheme

tim_hess427tim_hess427 Member Posts: 131 PRO
At my company, we're taking a look at our part (and document) numbering systems, and I'd like to know what others here think about the topic.

I've been reading Watt's book (Engineering Documentation Control Handbook), where he advocates for a dash number system. My understanding is that it would look something like this (please correct me if I understand this wrong!):
  • 123456 is the base item number and does not have any significance
  • 123456-00 = Drawing
  • 123456-01 = released part
  • 123456-02,-03,-04 = could be a variants (color, material), or non-interchangeable part revisions.
This seems like a reasonable approach. However, I have a few questions. What if I also have other specification documents I need to tie to this particular part (3D printer settings, material specs, etc.)? I suppose I could give those documents a dash-number. But, if I have a spec that is used for multiple parts, I'd want it to have its own document number. It seems like this inconsistency would be confusing over time.

On the other hand, some people recommend having a complete non-significant part number. In those cases, how do you manage part variants and document references? Do you just create cross-references on the drawing as necessary?



  • Cris_BowersCris_Bowers Member Posts: 281 PRO
    I've been involved in coming up with part numbering schemes for multiple employers. At first I was a big advocate for smart numbers where every portion had a significance. Eventually though you will run into a scenario you didn't think of and have to add a new dash to it and then you forget what something means and have to have a lookup table to figure out what it all means anyways. After that I jumped on the non-significant train. Every part/document gets a unique identifier and a detailed description which can include all the information needed to manufacture the part. If you have parts or documents that fall into a family I don't see a problem with adding a suffix, but you'll need to decide on how many digits you think you will need and add an extra digit because you will probably underestimate. So if you think you will never have more than 99 related parts, then you should use 3 digits, 000-999.  So your document number would end up looking like 123456-001, 123456-002 etc. I like only using revisions during the design and review process, where you just add an R1, R2, R3 etc. Once the part/document is approved drop the revision indicator. If something changes down the line, make a new part number that covers the changes.
  • tim_hess427tim_hess427 Member Posts: 131 PRO
    @Cris_Bowers - thanks for the feedback. I was thinking more about using the suffix to tie different document types back to the part. So, for example:
    • 123456-00 (or maybe just "123456") = part
    • 123456-01 = Drawing
    • 123456-02 = STL file export
    • 123456-03 = 3D printer build file, G-code, etc.
    • 123456-04 = Relevant specifications...
    • etc.
    I don't think I would say "-01 is always a drawing file", but rather, I would increment the suffix sequentially. The goal being, I want to look up "123456" in my system and see all the relevant information for that part without having to open up a lookup table or cross references.

    However, I can see issues with this system as well:
    • What if specification 123456-04 applies to other parts as well?
    • What if I change part 123456? Do I duplicate all of the documents just to give them the new number?
    In the case of the completely non-significant numbering system, where do keep the lookup table to know which documents go with which part?
  • owen_sparksowen_sparks Member, Developers Posts: 2,283 PRO

    Just throwing options around, we use a prefix to handle that:-

    Type Prefix - Project Number - Other Stuff - Revision
    eg MD-141-0001-A

    MD = Mechanical Drawing
    GA = General Assembly aka BOM
    3DP = 3D Printed Part

    Cheers, Owen S
    Production Engineer
    HWM-Water Ltd
  • tim_hess427tim_hess427 Member Posts: 131 PRO
    Hi @owen_sparks, thanks for the perspective! We've actually got the prefixes now, but reading some books had me looking at the suffixes. I'm likely thinking too hard about this :smile:

    Do you enforce a rule that files related to the same part share that part of the number?

    So, for example: Do MD-141-0001-A and 3DP-141-0001 refer to the same part?
  • Cris_BowersCris_Bowers Member Posts: 281 PRO
    In the case of the completely non-significant numbering system, where do keep the lookup table to know which documents go with which part?
    @tim_hess427 You'll want some sort of database/ERP system
  • tim_hess427tim_hess427 Member Posts: 131 PRO
    Agreed - and we are looking at a variety of systems. 

    One thing that's come out of that research is different systems have different levels of capability for dealing with the engineering documentation. They all reference part numbers, but don't always have ways to tie the part number back to all of the documentation that goes along with it (perhaps this is really the domain of a PLM system instead). This starts to bring me back to every part number having a drawing with the same number that calls out all of that documentation. 
  • Cris_BowersCris_Bowers Member Posts: 281 PRO
    Now this might sound kind of silly, but what about creating a part studio with a dummy part as a stand in for your engineering documentation, say an extrusion that is 8 1/2" x 11", representing a piece of paper. This can be inserted into an assembly and also show up on the BOM if it is something you need done. If you are using Google Docs, you can create a link to the actual documentation with the LinkTab app. I'm just not sure if there is a where used query in Onshape.
  • David van der MeerDavid van der Meer Member Posts: 1
    @tim_hess427 I have read Watts' Engineering Documentation Control Handbook front to back, and looked at the suggested part numbering in quite some detail as well and how this can be applied at the organisation I work for (we have something similar to what Watts describes). I think it has a lot of merit, but you would still need to be careful when/how to use this tab, because it's tempting to get a bit too clever with it.

    The book suggests to use this tab for "similar" items documented through tabulated drawings (with a dimensional variable for example), different colors/finishes, etc., as well as for non-interchangeable changes. If you combine the two however it starts to get more complex (what happens when you make a non-interchangeable change to parts on a tabulated drawing, with different sizes and different finishes?).
    At my organisation there have been attempts to add some significance to the "tab" number as well (e.g. -02 = primed, -08 painted blue, -21 = galvanised etc.), but this is also not helpful in the long run, and it would be better to number sequentially for the different finishes as required.

    What you are describing however is a need for different document "types". If your part has P/N 123456-01, and the corresponding drawing number is 123456-01 as well, wouldn't it be helpful if your STL file is 123456-01.stl, your DXF is 123456-01.dxf, and your 3D Printer build code file is 123456-01.xyz as well?
    Then if your design changes non-interchangeably and becomes PN 123456-02, then the relevant STL and build files will update to that number as well.

    The book suggests that a document-only part gets tab -00, so its part number is 123456-00. It would be a safe option to simply keep these documents standalone and refer to them on any component you might need them, and not risk the confusion of grouping the document with another part the first time you create it. Unless it applies uniquely only to that one part, similar to an STL file.
    If you consider that a specification document has a part number, then you can reference this document like you would any other part in a parts list. With a proper PLM/ERP system you will then get full used-on availability. This is covered in "Chapter 2 > Assembly Parts List" which has an example of what such a parts list would look like including reference documents which have part numbers, and again in Chapter 5 on BOM.
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