Round coming out faceted in W4/W5

[treddie]

Howdie.

I am using Wildfire-5, F000, and just stumbled on a problem I have never encountered before.

Please see the attached image. The first shot just shows the overall part, and the second one zooms in on an edge to show that the round I am trying to make ends up looking faceted. This is not due to my shading quality as I have it at 10. Also, my part accuracy does not affect the result. It is not a display issue because when I export out as wavefront (surface model), the problem is definitely in the model.

The big revolve feature is about 18 in in diameter. The round is .005". Changing the round value does not fix the problem.

So I went back to W4, recreated the part there and the same problem occurs. This is a simple revolve feature. No other features present except the "failing" round.

I am assuming I have an option set wrong in my config file, but cannot find anything that might be set wrong.

Any ideas?

 

[jebiselucka]

Hi
Send part
I look what is problem
regards

Wildfire is very nice, if you know,
how work with him

 

[treddie]

Thanks for responding, jebiselcka.

Here is the part file.

 

[treddie]

OK, this is weird. After doing a bunch more tests, it looks like there are two issues.

I found that by reducing the shading quality down to 1, that visually on the screen, the problem appears to go away; the round looks fine. But I believe in fact it is because the shade quality has been set to its lowest value, so this poor display quality actually hides the problem. When you kick it back up to 10, the problem reappears. In fact, it is this version at quality 10 you see on the screen that is closer to what actually gets exported out in the Wavefront facets file. This all makes sense if it also means that there is a angular resolution limit with ProE's round system, or some similar problem (again, maybe a config file setting).

The odd thing is, I've never seen this before, so I'm still stumped. Something I have in my config must be set up wrong. But I use the same config file I've used for years.

 

[jebiselucka]

By me its the same
That happen by very small radius
to part comparison
Config file is OK

Wildfire is very nice, if you know,
how work with him

 

[treddie]

Maybe I just forgot about it happening before, but I certainly don't remember it in the past.

 

[seymours2571]

Treddie,

This is an issue with accuracy. By default (unless modified by your CAD system administrator) ProE starts with a 0.0012 RELATIVE accuracy. Meaning the accuracy of the part changes as the size (or bounding box) of the model changes. Therefore, as the part overall size is increased the accuracy is reduced. This was done when computers were not as powerful as they are today. Reason being, as the accuracy is reduce the computational time required to generate or regenerate features is reduced.

So in your instance with a large 18" revolve and a 0.005" round the 0.005" radius may be below the accuracy of the part.

A more optimal setting for today's PCs is to change the accuracy to ABSOLUTE. With absolute accuracy the accuracy of the part never changes. I regularly set my accuracy to be 0.0001 absolute. Therefore, regardless of the overall size of the part my small rounds and chamfers will always be correct.

This accuracy issues is also the leading cause to disconnected geometry during export of your model to another CAD package and meshing problems in FEA packages such as Mechanica. Also, when the accuracy issue becomes large you will get errors such as "cannot intersect feature with part". This is a sure sign things are amiss with the accuracy.

More information from PTC regarding absolute accuracy versus relative accuracy can be found here:

https://www.ptc.com/appserver/cs/view/solution.jsp?n=32869

Good luck,

Steve


Stephen Seymour, PE
Seymour Engineering & Consulting Group

http://www.seymourecg.com

 

[treddie]

Thanks Steve for your post.

I neglected to mention in my original post that I was in Absolute mode. I thought it was that too, but when I changed to Absolute at the default .0001 or even .00001 or as fine as ProE would let me, the problem still remains. That's why I am stumped. The only possibility I can think of is that when I do the sketch I have to be in Absolute mode with the appropriate accuracy, BEFORE I start. But it always seemed to me that ProE has never had any problems in Sketcher or Part mode when switching accuracy midstream, other than possible regen failures. At least it always seemed to recognize that it had to go into all features and sketches and make the appropriate adjustments.

 

[seymours2571]

Hmmm...strange. I will download the part and take a look. I don't think the accuracy necessarily needs to be set prior to the start of modeling, because it will regenerate the model after changing the accuracy mode. However....it is a PTC product.

I will take a look.

Steve

Stephen Seymour, PE
Seymour Engineering & Consulting Group

http://www.seymourecg.com

 

[treddie]

Ah come on, PTC fallible?

I don't think it's an issue of starting out in ABS Acc either. Pro is very religious about checking everything when things are changed midway through.

 

[seymours2571]

This is truely bizzare. I rendered your part with the maximum quality settings and it still showed the surface as faceted.

I changed the graphics mode from opengl to win32_gdi. I know this is a move backwards, but at this point I was trying anything. No luck here.

I tried various combinations of shade settings with no luck there either.

This is very strange.

I would be interested if anyone else finds a solution.

Steve

Stephen Seymour, PE
Seymour Engineering & Consulting Group

http://www.seymourecg.com

 

[treddie]

So I'm not the only one who is befuddled by this one. At least I'm not going crazy!

The only thing I could surmise was that at a lower quality of shading, the problem was masked behind the low quality. Then when the quality was increased, the problem becomes evident. But that is so counter to the way I have always known ProE to work. I'm wondering if there is a bug in the rounds code that doesn't give the round the proper level of detail under certain circumstances.