Whether using actual drawings or relying on the model, and whether using a highly controlled documentation system or nearly completely uncontrolled, one will find revisions are necessary. It is important to use them consistently. It is important to make sure each time another person sees a drawing or model, they understand which revision is in front of them. It is important not to reuse revisions. If there is a working copy that is incomplete, preliminary or draft, then stating such directly on the document is very important.
Also important is avoiding interpretation confusion. If using letters to represent revision iterations, avoid using letters that resemble numbers or that can have alternative meanings. ASME Y14.35M-1997 states that I, O, Q, S, X and Z should not be used as revision letters. In fact, other ASME engineering drawing standards also forbid the use of these letters for other purposes as well. The reason is that I, O, Q, S, and Z all can be misinterpreted as numbers 1, 0, 5 and 2. When X is used, it looks like a field that requires further input.
These rules where written before the Information Age (wiki) and our reliance on computer databases, back when documentation relied on handwriting. However, these rules are just as important in our current age as they have ever been before. Many different types of computer fonts exist. What looks like a 1 in one font will look like an I in another. Even with my 20/20 vision, I will confuse S’s with 5’s in small sizes in certain common fonts. Also, transcription errors still enter the picture, as a human who does not have direct access to the electronic database is usually involved at some point.
PDMWorks (soon to be renamed to SolidWorks Workgroup PDM by SolidWorks Corp) automatically assigns revisions to documents when they are checked-in. There are options for the PDMWorks Administrator to use dumb ranges, or to establish a list of revision identifiers from which to pull. Unfortunately, when using letters, PDMWorks does not automatically disregard the taboo letters. So, I’ve made an Excel file with a list of allowed revision letters. It can be copy-and-pasted directly into PDMWorks VaultAdmin’s Revision Scheme Listing fields. It is available here: Allowed Revision List.
Part 2 of this article series will address using PDMWorks ability to automatically revise drawings upon check-in.