CAD Standards

[nathan_hui]

Do any teams have a set of rules regarding how they name, format, and structure their CAD models? Any suggestions for compiling a set?

P.S.: Our team uses SolidWorks at the moment.

[Tristan Lall]

Do you use version control (or PDM, i.e. product data management)? You should, even if in a rudimentary form (like saving backup copies at important milestones, e.g. daily and before each major restructuring of the assembly).

There's also some debate over whether or not to use an ordered numbering scheme for part files, or just to number each one sequentially and let the PDM software handle it based on the part name defined within the file.

If I were setting up PDM, I'd go with sequential numbers, and let the names, part-to-part relations, etc. be defined within the files. This means that re-using parts is easy, and that the PDM software can always find the right file. It's also easy to duplicate and then adapt a part in future, and to switch between versions.

Absent dedicated PDM software, you'll probably be managing your files in Windows Explorer. Given that, you may instead want to give your files meaningful names for your own convenience.

Then again, maybe just set Explorer to view thumbnail tiles for identification purposes, and start using part numbers right off the bat, so as to pave the way for PDM adoption later.

[Tristan Lall]

Also, with regard to structuring the models themselves, it's often convenient to choose features that logically approximate the machining processes that you'll use. Use hole features for drilled and screwed holes (instead of cuts). Use cuts for cuts. Use subtractive features when machining from stock.

This will help guide you to design parts for manufacturability. However, there are many exceptions to this: it's just a suggestion, not a rule.

One other thing to keep in mind—and this one is pretty much a rule, not a suggestion: fully constrain your geometry. SolidWorks allows you freedom in leaving things unconstrained in your sketches. But this makes the sketcher a lot less powerful for use as a mockup, because you can't reliably adjust the sketch without other things being affected (sometimes subtly). You don't have to fully constrain it to start with, if you don't want to, but at some point it usually makes sense to freeze things.

[Garrett.d.w]

At the engineering firm where I did my internship we used the following to name the models:

Job_Assembly_Part Name_Part Number_Employee Name_Date Saved

Ill echo what Tristan said above with one addition, keep the model as "modular" as possible. Separate the design into subassemblies (drivtrain, arm, etc) that are completely independent of one another. This allows more than one person to work on the model without the fear of overwriting someone else's work. It also allows you to easily re use the assemblies.

[Paul Copioli]

This is a great question and an area that most people overlook or just take for granted.

Here are two systems that I currently use. The first one is at IFI and is structured based on the fact that we have three main engineering companies that share resources. We use a three digit numerical prefix system. Our SKUs, or items for sale to customers are seven digit numbers where the last 4 are unique no matter what the prefix. The 3 digit prefix is assigned based on company. VEX has the 200 series. That is why the VEX Robotics Design System items all start with either 275, 276, or 278 and VEXpro starts with 217. Rack solutions has the 100 series numbers and Hexbug has 400 and 600.

The last 4 are sequentially assigned based on the next available SKU. for sub items that are not to be sold to customers we use 10 digits. The first 7 are from the actual sold item and the last three are arbitrary numbers assigned in order.

This system helps is identify which product line and which actual product a part is from

On our FRC team we use a little different system. We use TC-yyyy-xxx-abcd where yyyy is the FRC competition year. XXX is the subassembly. For example, 100 is the drive base and 110 is the drive transmission. The last digits are assigned in order but the main assembly is always -000. For example last years drive base subassembly was TC-2012-100-000.

Paul

[inventor_phild]

Nathan,

As Paul has noted this an area that is overlooked and causes major issues for teams. It also cause problems for engineering companies! In the next couple of days I wil be posting suggestions for file management using Autodesk Inventor, however can be applied to any CAD package or related files.