Model vs Drawing tolerances (Y14.41 ?) & notes.
Model vs Drawing tolerances (Y14.41 ?) & notes.
(OP)
We are using models as the "master data", yet have drawings to clarify what is not on the model. My issue is with tolerances. Typically untoleranced dimesions on the drawing default to the title block tolerances (.xx, .xxx). However, when using the model as the data, how are the tolerances handled. I had placed a note saying that any model measurement shall be considered a two place decimal per the drawing title block. I also have a note that states that the (hard) dimensions on the drawing superceed the model data, so that there is no mis-interpretation between the model and the drawing. Is this the correct way to pursue this? Since I have up to now provided complete details on the drawing I did not have to worry about this. Where I'm at now, they have been mostly involved with prototyping, and have been able to get by without this kind of control. But they are now trying to apply the same method to high production, which makes me nervous.





RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
This defines how GD&T are applied to 3D models.
"Art without engineering is dreaming; Engineering without art is calculating."
Steven K. Roberts, Technomad
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RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
I do my best to make all dim's 3 place decimal nom, then add tol where needed.
Chris
Systems Analyst, I.S.
SolidWorks 06 4.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 06-21-06)
RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
"Art without engineering is dreaming; Engineering without art is calculating."
Steven K. Roberts, Technomad
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
You have to use surface and trimline tolerance and just add positional tolerance to key features like hole positions.
RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
This is the same problem you get when you have fabrication drawings with both metric and English dimensions. You have two sources of information, one of which is correct, and one of which you provide entirely out of the goodness of your heart, for reference only. There is no other way, other than not providing the second set of information.
Your master data must include a complete set of dimensions and tolerances, somehow. If you cannot implement ASME Y14.41-2003, then you must prepare complete 2D drawings, and provide the 3D model for reference.
I used to work as an inspector in the automotic parts industry. I never saw a drawing. As far as I can recall, the customers provided inspection fixtures. Maybe this is your solution.
JHG
RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
It is also common to show the areas where the part should be clamped for inspection and the datums.
RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
I can't wait for the day that the business I am in now, tool and die, can fully utilize minimum contest drawings. We have all the equipment to get'er done that way. Only thing standing in the way is the mindset of the people who only know one way of getting things done.
Regards,
Anna Wood
A former automotive sheet metal and interior trim senior designer, CGS jockey, Philpot and DeSmet grad.
RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
This is often the purpose of reduced dimension drawings. Only show the dimensions that are critical and must be held to a tolerance other than the general tolerance. Not everything needs to be dimensioned.
RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
As with any “new” technology some people grasp the concept and others play at it. To me at least to start creating 2D drawings from a model is like constructing a profile in CAD and then dimensioning it up so someone else can create the same profile, or drawing something in 2D printing it off and dimensioning it on a drawing board, you simply take away the main advantage of doing it that way in the first place.
The main advantage of modelling as I see it is poly patterns or castings can be made to them, simulations can be run on them, machining can be done to them, inspection can be done to them, they are the master for everything. I think many companies that fail to realise this will fall on hard times.
RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
If you are talking dumb (step, iges etc) models surely you need at least a reasonable drawing for tolerances, material, notes etc?
If the customer/supplier is able to read annotated models then I can see how MBD may work but I'm still struggling to get my head round it.
Maybe if I ever manage to get 14.41 it will all become clear.
RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
Our parts are in the size range where it's not important to define different tol's for different size features, so this general note works for us and we don't even need ISO-like conventions.
If you deal with parts/features of drastically varying ranges, then perhaps emulating the ISO tol convention might be advisable for creating standard tolerance on your solid models.
Matt
RE: Model vs Drawing tolerances (Y14.41 ?) & notes.
The designer selected block tol based on what he thought was going to be the most common/applicable/required tol on the drawing.
Any dimension needing a different tol was modified to be +- or mor normally limits.
Bad thing was you had to look at every dimension and think what tolerance was applicable.
Good thing was you had to look at every dimension and think what tolerance was applicable.
RE: Model vs Drawing tolerances (Y14.41 ?) & notes.