21 Replies Latest reply on Oct 12, 2016 6:57 PM by Rob Edwards

    Level of precision and dimension format - how to explain it to estimators and non-CAD professionals

    Darren Neupert

      We have been dimensioning our CAD drawings with two place decimals for more years than I care to remember.  It has worked well with seemingly no confusion between production departments.  Our business is packaging and, more specifically, protective foam packaging.  Our tolerance for nearly all items is +/- 1/8".

       

      To spice things up a bit, we also run a corrugated (cardboard) packaging division.  That division works in 16ths of an inch.  We have an industry standard format for dimensioning in 16ths and it does not use a decimal point.  (e.g. 12'01 = 12+1/16, 12'07 = 12+7/16, 5'15 = 5+15/16 and so on)  We ditched this dimension format years ago due to the confusion with people outside of our industry and switched to simple fractions in our corrugated design software (ArtiosCAD)

       

      Recently, one of our cost estimators read a Solidworks drawing with a decimal dimension of 1.06 and incorrectly interpreted that to mean 1+3/8" (or basically 1 + 6/16ths) when in reality it is 1+1/16.  We decided to change our dimensioning standard to fractions to avoid any future estimating errors.

       

      Here's the rub.  Instead of the senior cost estimator issuing a friendly reminder to the other cost estimators that we're using decimals on Solidworks drawings, it was thrown back at us as being our problem/error and now they want us to extend all dimensions out to four decimal places.  Naturally, we're not overly fond of this idea, as we feel it declares a level of precision we are not prepared to cope with.  (we're basically fabricating spongy foam).  We prefer the two place decimal format or fractions.

       

      How does one have a conversation about level of precision with people outside an engineering department?  Do other companies allow a cost estimating department to drive policy/procedures in engineering/design departments?  It's now to the point where a meeting will be held today to ask production people what they want to see in terms of dimensions and how they want it formatted.  I'm sort of SMH right now and on my second Ibuprofen.

       

      Thank you in advance for any input/advice.