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12-12-2017 07:35 AM

Hello,

when I imported a step file to NX, is it possible to find out the tolerance value which has been used for creating the step file?

Or can I see it from the step file itself, without using NX?

As the standard value in our Environment for NX11 is some inch value, which is not supposed to be used, I want to make sure that the step files which are created have the correct tolerance setting.

Thanks,

Ralph

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11 REPLIES

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12-12-2017 10:16 AM

as I remember, it should be UNCERTAINTY_MEASURE_WITH_UNIT(LENGTH_MEASURE(xxx), ...

within the STEP file

As the standard value in our Environment for NX11 is some inch value

You mean that your precision is some inch ? =8-|

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12-13-2017 01:59 AM

Excellent, thank you very much!

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12-13-2017 08:05 AM

Actually I just found out, that in a step file I just exported from NX11 I have several entries with different tolerance values, although I entered 0.01mm for B-apline Tolerance:

#70412=UNCERTAINTY_MEASURE_WITH_UNIT(LENGTH_MEASURE(0.1),#70421, 'DISTANCE_ACCURACY_VALUE','Maximum Tolerance applied to model'); #70413=UNCERTAINTY_MEASURE_WITH_UNIT(LENGTH_MEASURE(0.1),#70421, 'DISTANCE_ACCURACY_VALUE','Maximum Tolerance applied to model'); #70414=UNCERTAINTY_MEASURE_WITH_UNIT(LENGTH_MEASURE(0.0455226515310176), #70421,'DISTANCE_ACCURACY_VALUE','Maximum Tolerance applied to model'); #70415=UNCERTAINTY_MEASURE_WITH_UNIT(LENGTH_MEASURE(2.E-5),#70421, 'DISTANCE_ACCURACY_VALUE','Maximum Tolerance applied to model');

That means NX is not using the value from the field B-spline Tolerance for all features but choosing a random tolerance value?

How can I make sure, that the exported step file has the quality I want?

Thanks,

Ralph

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12-13-2017 11:00 AM

I suppose this is the max. edge tolerance of your model.

Try Examine Geometry and check this value.

As for the 0.1, as I remember this is the max. range of the UNCERTAINTY_MEASURE_WITH_UNIT field

for exported model, which means that your edge tolerance in these models could be

higher. If this is the case , this is a problem, and you may want to check this with Examine Geometry.

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12-14-2017 02:49 AM

I checked the maximum edge tolerance in my model with examine geometry and the maximum value is 0.0105mm, but the UNCERTAINTY_MEASURE_WITH_UNIT value in the step file says 0.0222979980665933mm.

I don't understand that.

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12-14-2017 04:49 AM

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12-14-2017 09:02 AM

Unfortunately I cannot provide the model, but I don't see that this is a model issue anyway.

When I can set a tolerance / accuracy when creating the step file, I expect the system that this is used and not a different random value. Otherwise I do not understand what this tolerance setting is for.

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12-14-2017 10:39 AM

the B-spline Tolerance is just for refitting NX surfaces/curve that don't have a STEP equivalent (e.g. NX blend).

If you modeled your part with a loose tolerance you shouldn't expect NX to make it more precise, nor you

should want to, as NX (or whatever software) cannot know what you want exactly.

I checked the STEP format, and UNCERTAINTY_MEASURE_WITH_UNIT is defined as the "model closure tolerance",

that is the largest gap in your model.

If you managed to sew surfaces into a solid, that should be the gap prior sewing. When you sew surfaces and there

is a gap, NX enlarges the edge tolerance of the first selected edge to touch the second edge, so I expect the

max. edge tolerance to be basically the same as the max. gap, but maybe this is not always the case.

This why it would be interesting to see even a small portion of your model, just the one which is more problematic for you.

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12-15-2017 01:17 AM

Ok, thank you very much for your explanations.

My intention is, that the step files which are generated shall have a certain quality, e.g. a distance tolerance no larger than 0.01mm. This is our standard setting for all models. But apparently there is no option to influence the quality of a step file, besides the b-spline tolerance, which influences just a part of the model.

Thanks.

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