Weird question about the accuracy of detailing views and thus the DXF's

[Patriot_1776]

We are using an OGP Smartscope (though it seems to be not so smart, but that's another story...) to try and measure some parts. They need a 2D DXF file for optically measuring things like a profile of a surface. Since the part shape is complex and you're seeing a silhouette of a slight curvature BEHIND the surface we want, the view on the dwg and DXF has multiple lines, very close together, and sometimes one is visibly segmented. As we're trying to measure profiles of perhaps .002", this represents a problem because the OGP uses this DXF view to compare the measured data to.

Questions:

1. How accurate are dwg views compared to the model?

2. How accurate are the DXF files taken from the dwg?

3. Does the "Relative" or "Absolute" accurace also factor into this? (I'd guess yes).

Weird, huh? Anyone else have these issues?

Are you down with OGP? (Yeah, you know me...)

Thanks in advance......

This thread is inactive and closed by the PTC Community Management Team. If you would like to provide a reply and re-open this thread, please notify the moderator and reference the thread. You may also use "Start a topic" button to ask a new question. Please be sure to include what version of the PTC product you are using so another community member knowledgeable about your version may be able to assist.

[colmacpro]

From what I have seen, accuracy of the model does affect the ouput to DXF from a drawing view.

Should be easy to test.

Change the accuracy of the model

regenerate everything and

Re-export the drawing view. do the same process at multiple accuracies and compare the results.

Output DXF version does have an effect on what spline entities are converted too, posilby line segments. The higher the accracy of the model the more and smaller the line segments.

Joe

[TomD.inPDX]

Frank, I'm sure you tested this a bit but as for accuracy from a relatively generic part, I get 4 place accuracy exactly as I defined it (x2 for 2x view). All the values in the DXF file are 10 digits to account for view placement as well. I see no reason to think that you would have corruption from exporting drawings using the latest DXF export routine. Even the hole exported as a circle rather than line segments.

I exported as Autocadd 2010

I left model accuracy at the default Relative .0012

Default decimal accuracy was set to 4.

Since our drawing views are a literal viewport to the model, you shouldn't have any issues. The only time "parsing" would take place is when you decide to plot and parse overlapping lines when some lines would be removed by the plot process itself.

[James62]

It's not a wierd question.

I think low accurate exports are only good for the looks. Most of the CAD/CAM softwares can't import these properly which then results in many problems that are hard to explain.

That's why I always advice people from other companies that we deal with to give us highly accurate exports when we are going to need to work with this data.

Cause do they want us to make an accurate product for them on time or sooner than on time?

Well I could go on with this one but I think you might still see multiple lines close to each other even if you set your accuracy to high setting then it might be problem of your model having multiple one or two sided edges at that particular spot.

Is it a solid model you make DXF file from? Is it a native ProE model?

As far as I know ProE can't simplify shape of curves or merge multiple curves into one within specified distance/tolerance during the export to DWG/DXF.

[TomD.inPDX]

Jakub, drafting views are smart enough to eliminate overlapping lines in the background. The DXF export does not draw the "front edge" and the "back edge" for instance. That is part of the basic function of the pro/detail if you use a view other than wireframe. In some cases, the edge of "hidden" circle behind and edge will export. But indeed, the back edge is removed.

Since these are "windows" to the actual model, there is no reason to believe the views are anything less than accurate to the model. Autocadd 2010 also outputs splines so this should resolve the "segmentation" issues.

I use DXF for a lot of information and have never found a "proper" export to be lacking. 10 digits is more than significant in our world. If there is a requirement for DXF to the subordinate application, I would be comfortable using the drawing output from Creo/WF/Pro/e.

Then again, I do know what you are mean. It seems absolutely silly to have a perfectly good IGES or STEP file put through a parser to make a smaller file size. These often will not solidify and have all kinds of data errors where surfaces link completely wrong and makes the import completely useless.

When in doubt, look at the source and log file. It tells a lot about your export.

[Patriot_1776]

This inspection spftware needed an IGES files for certain measurements, and a 2D DXF file for others.

In some cases on the DXF file the inspection software was seeing the "double edges" that if you zoomed in far enough in the dwg you'd see as well. So, knowing exactly what the operater needed, I simply made a projected curve of the outline needed, created a layer for solid geometry, and in the new dwg I made strictly for DXF export, turned off the solid geometry in that view. Also, there were profile tolerances where a solid surface was split into zones with specific tolerance values for each zone, and so I trimmed those surfaces where needed (keeping both sides) and exported the solid model as an IGES using surfaces and curves instead of solid.

Tedious, but, it seems to have worked out well so far. I really think that the inspection software should be MUCH better so the CAD operators wouldn't have to go through as much time and trouble, but for now that's the solution. Like I said, it seems the "Smartscope" isn't very, well.........."smart"....

[John.Pryal]

Hi Frank,

at the risk of stating the obvious & being no help whatsoever, would creating area cross sections solve the issue of mutiple lines in your 2d views? that is what we do here when profiles are asked for.

Regards

john

[TomD.inPDX]

...and set the "model edge visibility" to "area" (view properties/sections). That will eliminate all silhouette edges.

[Patriot_1776]

'Morning John. Well, one of the problems is, that the edges I need, are not planar to the viewing plane for the view. So, a cross section wouldn't show. This is also one of the reasons the silhouette edges were showing up.