Cad models to nominal or to print

So to those that draw models. Do you build them to print tolerance exactly or do you build them to nominal?
example a hole that is 1" plus .004 minus 0. Do you build the model so it's 1.002" or per the print 1" plus .004 minus 0? If you build to nominal is that affecting your pcdmis program?

Schlag over 1 year ago

Build it at nominal !!! YOu can adjust CMM prg easy if needed. More importaint that the CNC ( or mold or whatever) is shooting for the bullseye !
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Matthew D. Hoedeman over 1 year ago in reply to Schlag

yeah, but in his example, the bullseye is 1.002, not 1.000 for machining purposes. If the machinist tries to make it at 1.000, and is a touch under, it is bad, if he shoots for 1.002 and is a touch under, it is OK. The CNC guys need something 'different' for making than the inspectors needs to checking when it is a unilateral tolerance, as you will NEVER get them to understand it.
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browningdmis over 1 year ago in reply to Schlag

Thats the mindset of this shop. Not used to that.

As Matt points out I build my program to print and the machinist do mot understand why my report does not look like there cad.
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Lake Monster over 1 year ago

It's becoming very common to get prints that only have hole callouts and critical dims and everything else is basic profile or TP with basics pulled from the model
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Matthew D. Hoedeman over 1 year ago in reply to Schlag

it is too bad that you can't choose (in Pcdmis) how to display the tolerance limits. Maybe you can in newer versions, but simply getting the +/- values (in this case, +0.004/-0.000) it what the main issue is with the unilateral tolerance of hole sizes (and maybe in other cases as well).

It would be nice to be able to have the report show:

DIM DH009= TRUE POSITION OF CIRCLE H009  UNITS=MM ,$
GRAPH=OFF  TEXT=OFF  MULT=1.00  OUTPUT=BOTH  DEV PERPEN CENTERLINE=OFF  DISPLAY=DIAMETER
AX   NOMINAL     +TOL       -TOL       BONUS      MEAS        DEV      OUTTOL   
X    5908.354                                    5908.354      0.000           
Z     862.800                                     862.800      0.000           
DF     16.000     16.500     15.500      0.500     16.000      0.000      0.000 ----#----
TP        MMC      2.000                 0.500                 0.000      0.000 #--------
END OF DIMENSION DH009

instead of

DIM DH009= TRUE POSITION OF CIRCLE H009  UNITS=MM ,$
GRAPH=OFF  TEXT=OFF  MULT=1.00  OUTPUT=BOTH  DEV PERPEN CENTERLINE=OFF  DISPLAY=DIAMETER
AX   NOMINAL     +TOL       -TOL       BONUS      MEAS        DEV      OUTTOL   
X    5908.354                                    5908.354      0.000           
Z     862.800                                     862.800      0.000           
DF     16.000      0.500      0.500      0.500     16.000      0.000      0.000 ----#----
TP        MMC      2.000                 0.500                 0.000      0.000 #--------
END OF DIMENSION DH009

Matthew D. Hoedeman over 1 year ago in reply to Schlag

sad thing is, with Datapage RT, you can choose to show either the +/- value or the limit value, but you can't in Pcdmis itself.
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browningdmis over 1 year ago in reply to Schlag

Matt that would be cool.
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browningdmis over 1 year ago in reply to Lake Monster

Yep this is true. I am ok with it but do we program to print or model?
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Schlag over 1 year ago in reply to Lake Monster

I would say that is customer specific and not a universal 1 size fits nothing answer.
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