Repeated angle measurements between planes gives different results

[nelrod]

Hello, first time posting and was unable to find similar issue.  The attached file is a simple extruded bracket component done in direct modeling.  When I repeatedly measure the angle between the top plane and the  XY origin plane (which should be parallel) I get different results.  Sometimes is will be 0.00 and sometimes is will be 8.54 x 10 to the negative seventh.  Also, the lines that define the sides of the extrusion are drawn at and measure 90.0 degrees but the angle between the planes is less or more than 90 degrees (more on one side and less on the other side) in the fourth decimal place.  From prior experience I know these errors propagate throughout a design.  I cannot avoid this if I am conscientiously measuring yet getting inconsistent readings.  Any help is greatly appreciated!

[TheCADWhisperer]

What measuring instrument will be used to detect that in the real world?

Is there a logical reason you are not using history-based modeling techniques?

From prior experience I know that many examples of this issue posted here have been tracked to poor modeling techniques (but in other cases it is simply math processing).

[seth.madore]

I will chime in a little bit here; inaccurate measurements (even out to 8 decimal places) will flow into the CAM, as Hole detection will often fail. I've seen this in items that have been built properly, sadly. It's something we're aware of, but don't have any action on yet.

[nelrod · Accepted solution]

Thanks both for fast feedback!

I only use history for sculpting.  Direct modeling suits my purposes and is much faster than using history.

And if I understand Seth, the eighth and ninth place decimals should be expected to show up.  This is good to know.

Thanks again!