Dimensioning in PCDMIS > SPC - Concern

[Underspec]

Hey all,


I have parts with +/-.005 and lower tolerances. Which means I have to use the 10% rule and use a .0005" or more accurate measuring tool (CMM).

My manager is telling me if the dimension only goes three spaces (.000") then I should only dimension to only three spaces (.000") in PCDMIS.

Here are my questions:

Shouldn't you be dimensioning four spaces (.0000") because of the 10% rule?

Does PCDMIS round up if using three spaces (.000")?

Does anyone out there do this?

I measure mostly diameters so use best fit dimensions. What do you guys think????

[Hilton Roberts]

I would printout my results to one decimal place greater than my blueprint tolerance if at all possible and analyze the results when out of tolerance results are printed.

H

[John Riggins]

3.7 MR3

PC-DMIS will round up.
If you have a deviation of .0006 and set dimensioning to 3 decimal places the report will show a deviation of .001.

John

[Matthew D. Hoedeman]

Well, it rounds 'nearest'.

0.0001 = 0.000
0.0002 = 0.000
0.0003 = 0.000
0.0004 = 0.000
0.0005 = 0.001
0.0006 = 0.001
0.0007 = 0.001
0.0008 = 0.001
0.0009 = 0.001

One step further:
0.00049 = 0.000

If he only wants you to report to 3 decimal places, it will make no difference since Pcdmis will STILL show it out of tolerance, even if it show a 0.000 out of tolerance amount. with a tol of +/-0.005, if you have an actual of 0.00549 (which will show 0.005 in 3-places) it will still give you the out of tolerance arrow and color. The only way to 'get around' that is to give it a tolerance that will only show 0.005 in 3-places, which would be something like 0.0054999999, which will show as only 0.005.

[Underspec]

I guess her concern is that when we start automating data collection to SPC with the control limits and all we should be matching the decimal spaces on print.