Part Spun Outline Locally Inaccurate

[Kasey7]

Hola!
What could be causing a local discrepency between a model and its spun outline?
I have a spun outline that is inaccurate in one area. Please see the attached picture. I have checked and re-checked my model and can not understand why the spun outline is giving me this .0001-ish taper in the ID. The curves used in the model sketch are horizontal, the blends are tangent, and everyhting is constarined with no conflicts. If I measure each end of bore the model, exactly as shown in the attached picture, both ends are 0.615.
BTW, no where else is the spun oultine doing this; all values between the model and the outline are identical.

 

[Toost]

Is the revolution axis what you intended ? ( slightly off/ angled to the plane of the sketch)
Re-select and measure again.
- Is the pictures from a "section" , then is that section perfectly thru the axis ?

 

[Kasey7]

Yes, it was the correct axis. I had measured all the other "diameters" of the spun oultine the same way as in the picture, and all are consistent with the model (no tapers, all values accurate to >10 decimal places).

 

[JohnRBaker]

Instead of measuring the distance between curves produced by sectioning the model, since there are circular edges in your model at the points where you are measuring, I would instead compare the Diameters of those two arc/circles as selected from the ACTUAL solid model and not depend on objects created during a secondary operation (such as the section curves).

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

UG/NX Museum:

http://www.plmworld.org/p/cm/ld/fid=209

To an Engineer, the glass is twice as big as it needs to be.

 

[Kasey7]

Hi John,
I'm unsure which analysis tool to measure the circular edges at each end of the bore. However, I did use Minimum Radius to measure the cylinder (see the attached picture).
The radius was 0.3075 (or Ø.615). Is this enough to shough that there is no taper in the model?

 

[Kasey7]

Shough = show.
How the hell did I miss that?

 

[Kasey7]

Damn. Forgot the picture too.

 

[Kasey7]

Here is another picture measuring the diameter beside the tapered one. (I know this is contrary to what John just suggested, but I wanted to submitted it for comparison with the first picture.)

 

[JohnRBaker]

Go to...

Information -> Object...

...select the two circular edges and hit OK. You will get a full report covering the information about the two curves/edges including diameters and much more.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

UG/NX Museum:

http://www.plmworld.org/p/cm/ld/fid=209

To an Engineer, the glass is twice as big as it needs to be.

 

[Kasey7]

Here you go (see attached txt file).
Both arcs have the same radius.

 

[JohnRBaker]

When in doubt, ALWAYS go back to something which is part of the model itself rather then depending on objects created during a secondary operation.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

UG/NX Museum:

http://www.plmworld.org/p/cm/ld/fid=209

To an Engineer, the glass is twice as big as it needs to be.

 

[Kasey7]

I agree. I was going way back and checking the model sketch, and values and constraints within. Info > Object is much handier.

 

[Kasey7]

Well, I don't know why, but the corner radius is causing the Spun Outline to be tapered.
Nominal is R.016", and that is what I started with. If I remove the R.016" from the Sketch, the Spun Outline is updated and the taper is gone. Any radius, as small as R.001" causes the spun outline to be tapered. For fun, I added a radius to other portions of the sketch. All the curves that were creating and ID become tapered after adding a corner rad, whereas all the OD with a new corner rad remain cylindrical in the Spun Outline.
Again, all the diameters are cylindrical on the solid model, but they become tapered in the Spun Outline. >_<

Argh! And now the Eng-Tips smileys don't work!

 

[markrief]

What options did you use for the spun outline? What version?

Mark Rief
Product Manager
Siemens PLM

 

[Kasey7]

NX 8.0.2.2
The Turning_Workpiece geometry was generated using Automatic.

 

[JohnRBaker]

Since it appears that you're working in Imperial Units (inches), unless you've changed the Modeling Tolerance, it's still set to 0.001" which in this case, where you have objects whose parameters are approaching that limit, would be inappropriate. I suggest you change this by an order of magnitude (from 0.001" to 0.0001") and try creating your sketch over again.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[Kasey7]

No change. I even removed the blends from the sketch, and added them to the model as a feature.
When the blend feature is on, the taper shows up in the Spun Outline. Turn the blend feature off, the taper goes away.
Anyway, I'm sending the models and CAM setup to GTAC today. Hopefully they will find something.

 

[JohnRBaker]

Features created BEFORE changing the Modeling Tolerance settings will not be effected by the change even if you edit them and they update. The modeling tolerance setting is saved with the feature when it's first created.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[Kasey7]

Ah! I didn't know that.
In any event, I'm proceeding with my CAM work without the blend, and GTAC has already converted the IR to a PR with a very impressive sounding "priority code of 1 Critical".
I'll update this thread when I have some news.