What is a SUSPECT 939 error caused by? 2

[Tetragrammaton]

Hi All,

Can anyone shed any light on this problem which occurs each time the file is opened?

SUSPECT939 Warning
Spline Check
WARNING: Splines with Bad Data Detected.
Look for splines with SUSPECT939 attribute.

Can anyone tell me how to located these 'bad spline' and fix or remove them.

Thanks in advance.

Dave

Best Regards

Dave

 

[Xwheelguy]

That's probably something that might require some technical support from Siemens, unless you wish to analyze every spline in the file and hope you can figure out which one is bad by the information NX gives you when you do an Info -> Object.

Tim Flater
Senior Designer
Enkei America, Inc.

http://www.enkei.com

Some people are like slinkies....they don't really have a purpose, but they still bring a smile to your face when you push them down the stairs.

 

[cowski]

I'm not sure what SUSPECT939 error is or what it is caused by, but here is one way to find the bad splines. Make sure all of the splines are shown on screen, now you can select (filter) objects based on user attribute (the "other" button on the class selection dialog in NX2, not sure where it is for higher versions). I'm assuming SUSPECT939 is the title of the attribute, type this in for the title. This would make it easy to move all the bad splines to a new layer for further inspection or change the object color so they are easy to spot.

 

[JohnRBaker]

What you have is a B-spline with some bad data, generally a singularity or 'sharp corner', which is considered an invalid condition for a B-curve. Now as to where this B-spline came from, I suspect it came from some external source (IGES, STEP, etc.) but there is also a small chance that you may have gotten hold of a VERY old Unigraphics part file (pre-V10.0) where the old cubic-splines could be created with sharp corners. Note that today it's almost impossible to create a B-spline inside of NX with any sort of singularity, which is why I suspect that this data came from some external source.

Now first, in order to find where the problem exists your best bet is to do an Information -> Object... and use the 'Select by Name' option entering the name 'SUSPECT939' and then hit 'Select all' and then OK. In the listing that gets generated, there should be some data about the problem contained in this SUSPECT939 attribute value. As to what you can do, there is no practical way to fix the bad spline, but you can extract the knot points and from that create a new spline. It's also possible that using the Insert -> Curve from Curves -> Join... might also get you a usable result. Also Edit -> Curve -> Smooth Curve... might be another approach to look at.

Anyway, you will need to do something because these curves can't used to create models such as surfaces or solids and get usable results. Even you managed to reuse the curve as is, it would eventually cause problems, which is why we flag them when they are detected.

So I hope that helps and let us know what you uncovered.

John R. Baker, P.E.
Product 'Evangelist'
NX Design
Siemens PLM Software Inc.
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

 

[JohnRBaker]

Let me make one correction here.

Actually there is NO need to mess with the 'suspect' spline since we have ALREADY fixed it, however that will ,in all likelihood, have altered the shape of the curve, therefore we tag it so that you can inspect the results and determine if the changes that were made are acceptable and whether the resulting model still meets your criteria.

John R. Baker, P.E.
Product 'Evangelist'
NX Design
Siemens PLM Software Inc.
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

 

[Xwheelguy]

John,

Good explanation as well as good information to know. Star for you.

Tim Flater
Senior Designer
Enkei America, Inc.

http://www.enkei.com

Some people are like slinkies....they don't really have a purpose, but they still bring a smile to your face when you push them down the stairs.

 

[hudson888]

Tim,

I'll go one further and I don't expect any congratulations just for being old, but the most frequent cause of suspect 939 errors is or was old parametric curves from pre-version 9 of UG.

Dave, check if you can whether your CAD file is well old!

Regards

Hudson

 

[JohnRBaker]

Hudson,

Yes, this conversion and message scheme was indeed originally developed as a result of the work we had to do during the V9 to V10 conversion where all old parametric cubic splines were converted to b-curves and old mesh or Gordon surfaces were converted to b-surfaces. And yes, the old cubic splines could have sharp corners (you created them by picking the same spline point twice in a row). I know some people who actually created models that way where they wanted a single surface which acted like it had two faces with a hard seam between them. Even the downstream codes, such as surface machining and such, all seemed to work OK, but with the advent of Bezier geometry all of that changed so we when we converted those old curves we had to convert them in such a way that they were now valid b-curves, but they had to match as close as possible to the old shapes, but since there were slight differences, we tagged them so that people weren't blindsided by that.

John R. Baker, P.E.
Product 'Evangelist'
NX Design
Siemens PLM Software Inc.
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

 

[hudson888]

John,

That's right the curve was actually given the name "suspect 939" and you could use that to find which one was the culprit. If it still does so then Dave would probably be helped to know that. I could check but then I'd have to find a DAT reader to get into my old V9 data.

Not only did we hit that hurdle and remember it but the reason why was that we had foreign surfaces which featured cubic splines with 99 knot points, and I think the problem was that the Bezier curves from memory only wanted to handle up to 80 knot points. Now I think these were knot points not poles because we also tried via IGES and found it was putting out two points on top of each other for ever intersection of curves on the surface. You could have made this thing through curves or perhaps even a ruled surface (same thing these days really I know), but anyway the code in IGES was describing a mesh. Not only did we have to hand edit the IGES file to fix it, but I never could open those files properly after V10.

And as for sharp corners in curves, sometimes you could machine the surfaces, but as often or not they'd gouge near the apex, especially if you ran the old parameter line method. We desperately hard to discourage people from using it. To this day I still hate a similar behavior that occurs when profiles with corners are used in the sweep function with any tolerance greater than zero.

Best Regards

Hudson