RE: Double-Dimensioning

I still follow the rule that you only dimension something once. Our CAD system doesn't do auto-dimensioning so it's still up to us to snap the dimension back on to the element after a change, so it makes sense to only have the one dimension. Although I'm getting more and more engineers demanding double dimensioning and also repeating information, for instance dimensioning equipment positions on a G.A. (!) and putting not just the valve number on a P&ID but also the size and valve spec (I mean, can't the guy read the line number and then the piping spec!).

The danger is people are getting so wrapped up in CAD technology that their forgetting basic draughting principles. These principles have evolved over time and some are just as applicable to CAD as they are to manual draughting.

Just my Monday morning rant <g>.

Nathan.

• Original Message from PipingDesign@egroups.com at 22/07/00 01:25
  >Since we were discussing drafting standards recently I thought I'd bring
  >this up.
  >
  >Double-Dimensioning: The appearance of more than one reference to a physical
  >dimension in a project. These days it would specifically refer to printed
  >drawings, as CAD models do not typically feature dimensions.
  >
  >In "the old days" double-dimensioning was a definite no-no. Multiple
  >references to the same physical object can cause major headaches when it
  >comes time to revise a drawing. Sure, the "plan" is correct but someone
  >forgot to update the detail drawing. When the fresh prints get to the field
  >this can cause a lot of confusion.
  >
  >Maybe it's just an isolated observation of mine, but it seems that with the
  >trimming of drafting staff (let's say checkers, for example) due to the
  >increased efficiency of CAD many times engineers are the ones doing the
  >checking. If said engineers are not familiar with the decades-old traditions
  >of effective graphical communication chaos can result.
  >
  >Any opinions out there?
  >
  >Paul
  >
  >
  >
  >
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