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Tolerance Stack-up Analysis or GD&T Design Notes

Newbie

Tolerance Stack-up Analysis or GD&T Design Notes


Has anyone attempted to use Mathcad as a tool to analyize or help document tolerance stackup and accumulation. I would be interested in any template someone may have started. Both worst case and root sum of the squares method. I'm also interested in any GD&T related design notes.
17 REPLIES 17

Tolerance Stack-up Analysis or GD&T Design Notes

Attach the work sheet.

What you are asking is still obscure !

jmG

Tolerance Stack-up Analysis or GD&T Design Notes

On 12/22/2004 1:12:36 PM, jmG wrote:
>Attach the work sheet.
>
>What you are asking is still
>obscure !
>
>jmG
--------------------

What worksheet are you referring to? I do not have any Mathcad file/template created at this point in time. I have never used Mathcad before or the user forum either. Engineers at my workplace are being asked to better document our design and analysis so I'm investigating a means of accomplishing this. I'm trying to set up a basic template or document which we can use as a starting point and tailor as required to complete tolerance stackups for various projects. I haven't figured out yet what capabilities MathCad has, or if using a spreadsheet would be easier.

Tolerance Stack-up Analysis or GD&T Design Notes

On 12/22/2004 2:26:14 PM, MikeH wrote:
==What worksheet are you referring to? I do not have any Mathcad file/template created at this point in time. I have never used Mathcad before or the user forum either. Engineers at my workplace are being asked to better document our design and analysis so I'm investigating a means of accomplishing this. I'm trying to set up a basic template or document which we can use as a starting point and tailor as required to complete tolerance stackups for various projects. I haven't figured out yet what capabilities MathCad has, or if using a spreadsheet would be easier.

Do you have a document giving the tolerance calculations that you could post to the Collab? This would give members some idea of the type and size of the calculations.

My initial feeling, from the para above, is that this might well be the sort of thing Mathcad is particularly good at.

Stuart
Not applicable
(in response to MikeH)

Tolerance Stack-up Analysis or GD&T Design Notes

I have done many worst-case and "Root-Sum Squares" mechanical tolerance studies in the past. Off hand, I don't see any particular advantage to MathCad in this regard. For most cases, I think Excel works fine since usually only arithmetic and trig functions are involved. It's an interesting idea, however.
Garth

Tolerance Stack-up Analysis or GD&T Design Notes

For a relatively simple RSS, Excel works adequately, but for a more complicated scenario, Mathcad is superior due to the ability to use symbolic names and the ability to retain units.

We just went through this exercise with Excel and Mathcad for some analysis at work and Mathcad provided a clearer final document


TTFN,
Eden

Tolerance Stack-up Analysis or GD&T Design Notes

Eden,

How do you do this in mathCAD in excel there is a function for it?

Tolerance Stack-up Analysis or GD&T Design Notes

On 1/7/2009 11:39:32 AM, akahighlander wrote:
>Eden,
>
>How do you do this in mathCAD
>in excel there is a function
>for it?

Not sure what function you might refer to. The basic stuff are summations, squares, and square roots, all part and parcel of Mathcad.

TTFN,
Eden

Tolerance Stack-up Analysis or GD&T Design Notes

I too am very interested in finding how Mathcad could perform this analysis. It's easy in Excal but very slow. If you don't have more than 25 variables try a program called MITCalc Tolerance Analyzer. It does all you are looking for. However, with many variables and several intermediate results, the program will run for 30 to 45 minutes for an answer.

The problem with using Mathcad is my inability to find how to use tolerances. i.e. X=.250 +/- .001. To me this is the crux of the difficulty. I have a Mathcad worksheet started but it's very simplistic.
X=.250 Xtol=.001
Xp=X+Xtol
Xm=X-Xtol

You get the idea. It works but it's not elegant. If there's someone who has figured this out I'd be happy to hear from them.

Cheers,
Ken

Tolerance Stack-up Analysis or GD&T Design Notes

The usual problem with "tolerances" in a design
scenario is the need for choosing the many different
methods of combination between the different parts.

In some cases it will be (alleged) worst case, in
other 6 sigma (which version?), others a root sum
squared, etc. Along with knowing if the reported
tolerance is a reasonable map to actual tolerances..

For example it was common practice in optical
components for them to be machine 'thick', so that a
second pass could be attempted if the curvatures
were wrong. This would require careful
considerations (sometime to the point of miss
setting the nominal size & tolerance!)

Yes it can be a problem...

Philip Oakley