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*Genova, Jon
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model dimension tolerances

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11-21-2002 03:52 AM
It appears that you cannot have mixed precision tolerances display
properly in a part model. I'm trying to capture design intent in a
part where only a few features requre .1234 place precision. Normally
.123 place precision works for pretty much everything we do. For this
example, I'm making a cube with one precision hole reamed thru the
middle of it.

With Tools>document>Linear dim precision set to .123 places

Create a block 1.000 x 1.000 x 1.000
Bore a hole thru it with a circle extrusion of diameter .250

Switch to feature priority selection

Double click on the bored hole- the dimension of the hole pops up.
Select the .250 dimension, RMB, select Dimension Properties...
Change the Precision to 0.1234 (expecting the tolerance also to follow
this format)
Select Deviation from the Tolerance Type- Upper= .0005, Lower .0000

Hit OK

The dimension shows .2500 +.001/-.000

Shouldn't it display like: .2500 +.0005/-.0000 ?? Um... I think so!


Now try this:

Goto Tools>document>Linear dim precision set to .1234 places
Hit the Update button or select Tools>Rebuld All

Now you see four place precision (.1234) on both the dimension and the
tolerance.
Problem is, all your part dimensions are also shown as 4 place.

If you create a drawing of this block and ask to "Get model
dimensions", the tolerance for this hole feature is respected as .1234
precision in the drawing despite what the precision is set to in the
dimension styles. This behavior is expected, and seems to work
properly.


I think the model tolerance should respect the precision set in the
"Dimension Properties.." dialog to convey proper design intent.




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Jon Genova
Senior Mechanical Design Engineer
BioServe Space Technologies

A NASA Commercial Space Center (CSC)

genovaj@stripe.colorado.edu
Bioserve URL http://www.colorado.edu/engineering/BioServe/
Personal URL http://stripe.Colorado.EDU/~genovaj/
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