June 2013 Design Tip

What’s in a Name?

There’s a lot to like about computer aided design. Changes to CAD models are easy to make. CAD files can be easily circulated for review or sent out for quotes. And once finalised they can be sent right to computer-aided manufacturing systems for prototyping or full-scale production. Later, if you need mo re of the same parts you can just pull out the CAD model or reference it if it’s held elsewhere, and produce all the parts you want.

But all that simplicity comes with a risk. Because it allows easy production—and reproduction—of files, CAD can lead to an abundance of revisions in various stages of development and confusion regarding which is the final or most current version of the design. There are many phases of development at which multiple versions can be produced. Here at Proto Labs customers often upload several versions of a design for ProtoQuotes. Similarly, we may produce parts from a CAD model which is then modified based on functional testing of those prototypes and resubmitted. In either case, if an outdated version of the design were inadvertently submitted for production, the customer would end up with the wrong parts, losing time and money in the process.

Simply numbering versions in sequence might, in some cases, be all that is needed to prevent problems. In some cases, however, changes need to be backed out, making an earlier model the preferred version. Or multiple reviewers could each return their own modified versions of a CAD model, neither of which would be the definitive next version until the changes are merged. Avoiding such problems requires two types of discipline. The first is a clear methodology for naming/numbering (and documenting) successive revisions of a file. The second is a shared approach to reviewing and handling revisions.

If designs are being produced by a single individual, virtually any logical system will work. Give succeeding revisions consecutive number or letters, or use a tiered system such as:

  • 1.0, 1.1, 1.2, 2.0
  • 1a, 1b, 1c, 2a
  • If you’re sure you won’t produce more than one version a day, you could track the most current version by making the date part of the file name, e.g. cam.april6, cam.april9

As simple as these schemes appear, they still require some discipline. If, for example, you revert to an earlier design, you’ll cause all kinds of problems if you revert to the earlier name as well. In other words, if revision 2.0 doesn’t perform as expected and you go back to 1.2, give it a new designation such as 2.1 or 3.0 unless you are certain that you can make 2.0 disappear completely. Figure 1 shows a typical naming implementation.

Figure 1: Naming Diagram

Figure 1: Naming Diagram

If more than one individual is involved in CAD development and review, it is critical to have one designated repository of current design, preferably under the control of one individual. We can’t tell you how to merge separate modifications to your design, but they obviously must be merged—reconciled if they conflict—and the resulting design given an appropriate label. We can, however, point out a couple of pitfalls to avoid:

  • Don’t let multiple, modified versions of a file share the same name, even briefly. This can easily happen if you send a file out for review and one or more reviewers alter it and send it back without changing the name.
  • Discourage people from inventing their own naming conventions. If one reviewer adds his/her initials, a second appends the current date, a third bumps up the version number, and another adds a ‘b’ to the name or number, you’re going to have a difficult time keeping things straight. A simple solution would be to request recipients to immediately rename the version they receive by adding his/her initials.

Note: While there are software packages for revision or version control, most are designed for managing very complex processes like software development and large web site design and might be overkill for part development.

Finally, in submitting designs for a ProtoQuote, your revision designation, whatever it may be, will be part of the file name you enter. And if your parts have both names and numbers, enter both (including your revision designation) in the “part number/name” field.

Do you have a different approach to control labels? If so, please share them with us for an upcoming Proto Labs Blog post. Send to: marketing@protolabs.co.uk.