Circular References - The Cure
As my Great Aunt Eleanor always says: “An ounce of prevention is worth a pound of cure, stop bothering me while I am trying to sell my WoW gold on eBay!”
While I am not entirely sure what all of that means, she certainly is correct if she is talking about circular references. Preventing circular references from being created is much easier than trying to find them.
Going back to last Monday’s quiz, the first puzzle’s problem could be avoided if you remember this quote: “Always mate before you relate”. [I’ll wait until the sophomore class stop giggling.] What this means is if you always fully mate the part in your assembly before you add any external relationships, a circular reference of this type will never happen. If you think about it, this is your design intent anyway. The position of the part is what you care about, the mounting fastener holes need to follow the part, not vice versa.
I don’t have a cute saying to prevent the second puzzle’s problem. The trick is to always ensure you mate your parts with design intent. Adding your parts to your assembly one at a time in a logical fashion will make this task easier. “PartA” is a fixed part. “PartB” bolts to “PartA” so fully add mates between those two. Next add “PartC”. “PartC” is located via “PartB” so only add mates between those two parts, don’t add any mates between “PartC” & “PartA”. Try to define the location of a part with only one other part. Though it is not always possible, this method reduces accidental circular references and makes an assembly easier to work with if your design intent ever changes.
Bottom up design and horizontal modeling techniques are also methods that reduce the likelihood of accidentally creating a circular reference.