3D Dimensioning? 1

[jaykm]

Hi all,
I keep hearing about the new ANSI Y GD&T standards through which we can (fully)dimension the CAD 3D model itself without actually having a drawing for that model [I may be wrong!]. Could someone throw more light on this and tell me in brief how this new GD & T std. is different/an improvement over the existing one?

Thanks,
Jaya

 

[ctopher]

RedPen,
It is a nice thought and sounds like a great idea. But the vendor ever has to question how to make the part and has to contact you in some form, it drives the cost up. The more info you can give them up front, the better.
If you create only models and no dwgs, how are they checked? Does the checker know the CAD software and know how to check the model? How does inspection work?

Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP2.0 / PDMWorks 05
ctopher's home site
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[ewh]

RedPen,
Using a profile tolerance as a general tolerance is acceptable provided that you define the datums to which the profile tolerance is relative. We use six points on the part surfaces to establish the datums, and then use profile relative to those datums.

 

[RedPen]

Ctopher, your points are well taken. It all worked much better when we were a small R&D company with a captive machine shop in the back room. They used our SolidWorks models in CAMWorks and made the parts right even if they were designed wrong.

We do make drawings and are supposed to indicate critical dimensions (and tolerances) on the face of the prints. We are also supposed to indicate which dims we wish to have inspected. First articles are 100% inspected and then samples of each lot, focusing on the indicated inspect dims.

Models and assemblies are checked during our design reviews and we do have a model checker that knows the software very well. Drawings are also checked according to ASME and company standards (I'm the lead checker, hence "RedPen").

And yes, datums are indicated both on the model and the drawing for the profile reference.

Thanks for your input. More thoughts, ideas?

RedPen

 

[ctopher]

Thanks RedPen. Sorry for my short responces and answers. I don't have much time to do much writing here at work.
Thanks for clarifying.


Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP2.0 / PDMWorks 05
ctopher's home site
FAQ371-376
FAQ559-1100
FAQ559-1091
FAQ559-716

 

[tgmcg]

Interesting thread. I'm relatively new to the ASME Y14.5 and have been using SolidWorks for a year. We're outsourcing some investment cast aluminum parts which require secondary machining. While we show detailed dimensions and tolerances for the machined features (holes) on the drawing, we are a bit puzzled as to how best to locate the as-cast features (eg. ribbed pockets with draft and radiused edges) which do not require any machining. How should we do this?

It's not yet clear if the foundry can reference the solid model directly, but it's encouraging to see that supplying drawing and model appears to be common practice among the posters here.

I do not really want to provide a lot of detailed dimensions for the draft and radiiused features as the as-cast dimensions are generally not toleranced.

Any comments or suggestions are most welcome. Many thnks!

 

[ctopher]

tgmcg,
You should start a new thread with this question.

Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP2.0 / PDMWorks 05
ctopher's home site
FAQ371-376
FAQ559-1100
FAQ559-1091
FAQ559-716