Some time ago, a visitor to SolidWorks Legion asked something similar to this: Now that we decided to use them, to what extent should my company comply with the ASME standards on our drawings versus our own internal rules?
That is a complex and difficult question. Purist will say, “Follow the standard exactly! Otherwise, why have a standard at all?” Internal traditionalists will say, “We already have a way that works for us. Why change what works?”
The answer, in my opinion, is in the middle. ASME Y14.100-2004 paragraph 1.1 states that the ASME standard establishes essential requirements for the creation and revision of drawings and BOMs. However, paragraph 1.2 then allows for “tailoring” of the standard to exclude unnecessary requirements. Though this is not an explicit statement that allows outright customization, it does provide a crack in the door that may be used to justify such customization of the standard. It is important to note that the ASME standard does not take the place of internal standards; it forms their foundation. The ASME standard still leaves options open for individual companies to define for themselves.
In a company’s internal drafting standard, I recommend including the statement, “Exclude from practice any portions of any standards (e.g., ASME Y14.100) that differ from instructions within this document.” This formalizes the effort to employ exceptions to the ASME standard. However, this must be used with caution.
One area that is a good case for exceptions is in how a company might handle BOMs within the context of a PLM. In such cases, it is often considered bad practice to list BOMs in two places (on the drawing and within the PLM). It may be advantageous to store and control the BOM within the PLM, rather than on the drawing. ASME does not address this. However, as long as the PLM displays the BOM in a manner consistent with the intent of ASME, I don’t personally see any issue with relying solely on that PLM for BOMs. The internal drafting standard should address such exceptions to ASME.
An area that is bad for exceptions is in the non-standard use of established symbols or abbreviations. This is because the symbols and abbreviations are already defined by the ASME standards. For example, if a company allows GD&T symbols to be used in a way that is not defined by ASME Y14.5-2009, a manufacturing vendor will not know how to properly interpret the custom use of the symbology. ASME does not allow ambiguity on drawings. However, if a company wishes to continue the use of a few of its own custom symbols and abbreviations, these need to be fully defined on each drawing or in an internal document that is referenced by the drawing.
In my opinion, this is the bottom line: leverage the ASME standards to save time and work (both in the creation and interpretation of drawings). Try to adhere to ASME as much as possible. Allow deviations that are necessary, but clearly state such exceptions within the company’s drafting standard or on the drawing itself (whichever works best for the situation).