Need Help Comparing Solids 2

[Updraft]

I'm looking for help comparing two solids. My situation is that we have a SWX part (SWX Target) that is used to program a CNC mill using a CAM package. The only solid output we can get from the CAM package is an STL file (CAM Result). We want to compare the two solids to verify the CAM programmer got everything.

We have tried subtracting one part from the other using the Cavity function, but it fails regardless of which part is used for the base. We have also saved the assembly out as a part file and tried to subtract one body from the other, but get similar failures.

We know the tesselation of the STL file will leave fine slivers of different geometry between the two files even if the CAM Result file is dead-on. This is okay, but probably also the cause of the failures, i.e., too many extremely fine bodies or "zero geometry" conditions. We are looking for differences of .010" or more.

I've posted all the files for your dining pleasure. You are welcome to feast on them and see what it takes to reveal the differences between the two.

By the way, no, our CAM software does not have any option to do this comparison. But I am pushing them for a solution too.

Thanks in advance,

- - -Updraft

 

[handleman]

Can you attach the file using the engineering.com upload rather than yourfilelink? That's blocked for me.

-handleman, CSWP (The new, easy test)

 

[Updraft]

Handleman,

I tried that first, but after three failed attempts I went to the FAQs to find suggested alternates. This site is a little wierd, but after waiting through some delays and looking around I was able to find the link to download the file so it does work (at least it does for me).

Do you have an alternate to suggest? I can post the zip file there.

- - -Updraft

 

[fcsuper]

Two easy options. First, the easiest. Create an assembly with the two parts placed exactly in the same place and orietation. Look at them and see where the surfaces intersect and where they do not. Second, if you have SolidWorks Professional, you can use the Compare Models function under Tools > Compare. See SolidWorks Help for details on how to use this function.

Matt Lorono
Lorono's SolidWorks Resources & SolidWorks Legion

http://groups.yahoo.com/group/solidworks & http://twitter.com/fcsuper

 

[Updraft]

Matt,

The first idea you mention isn't solid enough. I've already done this in the uploaded assy and combo part file, but there is too much detail to be confident of seeing everything.

The second idea I just tried and had high hopes for it. I had to create coordinate systems on each part to align the two using the Compare function. It took awhile and the attached screen shot here shows the result. Since these were dumb solids I compared on the geometry. The results says "Volume comparison (failed)".

Other ideas?

- - -Updraft

 

[ctopher]

Which CAM software is it?
I think I remember CAMWorks having the CAM data compare feature? Been a while for me...

Chris
SolidWorks 10 SP4.0
ctopher's home
SolidWorks Legion

 

[Updraft]

"By the way, no, our CAM software does not have any option to do this comparison. But I am pushing them for a solution too."

We are using FeatureCam and the version we have does not have this functionality. It is included in the $6500 upgrade to the next level. Yay!!

- - -Updraft

 

[CorBlimeyLimey]

Make copies of each part
Create a multi-body of both
Use the Combine function to subtract one body from the other

 

[Updraft]

CBL,

Last sentence of second paragraph in my OP - didn't work.


I had thought about using a third part to represent a block for the typical use of the cavity function, but I don't see how to ultimately tie that in with with both parts and see the differences.

My NC programmer just informed me that he found four holes that the automatic feature recognition (AFR) of FeatureCAM missed! He is pretty thorough, but this is by far the most complicated part he's programmed. If you take a look at it you can see it is large and involved. We show a machine time of just over 7 hours. The fact that the AFR missed something as simple as some holes and that we missed them in looking at the two superimposed solids in SWX highlights the value in being able to have SWX expose the differences.

I appreciate the thought going into this from you all. Please keep it coming!!!

- - -Updraft

 

[fcsuper]

Are these complete solids or do they have missing surfaces or other errors inside of SolidWorks?

Matt Lorono
Lorono's SolidWorks Resources & SolidWorks Legion

http://groups.yahoo.com/group/solidworks & http://twitter.com/fcsuper

 

[Updraft]

Both are good solids. SWX Target.sldprt was made from a parasolid of the original SWX part so it is golden. CAM Result.sldprt was made into a SWX part from the STL output of FeatureCam and it had one surface that needed healing, but that worked using the auto healing function.

I really think the problem hinges on the fact the STL file is faceted. As a result there are these tiny slivers of differences between the facets of CAM Result and the smooth curves of the SWX Target files. We've all seen the occasional "zero geometry" error and I suspect this condition is very much in that trench.

The zip file is big (12+M), but it contains all the files and attemps described in my OP. If you cannot access it from my link I'll gladly post it to another of your suggestion. I do not know why the Engineering.com did not load. I just tried a few more times, even putting the file on my desktop vs. the network, but no joy.

I look forward to the ideas and help.

- - -Updraft

 

[CorBlimeyLimey]

Oops ... Yup, I missed that.

Although the Import Diagnostics doesn't report any bad faces or gaps, there is something in the CAM Result.sldprt file which keeps locking up my machine. It opens OK, but seems flaky. Maybe too many facets created in the conversion from Feature Cam?

What format are you importing from Feature Cam?
What formats can it export?

 

[Updraft]

The only solid file format FeatureCam can export is STL. I do not see an option within FeatureCam to specifiy the resolution of the facets. We are stuck with the facets as they are, I'm afraid.

CBL, obviously we are both on SWX2010. What do you mean by "flaky"? CAM Result.sldprt is a large file due to the facets, but my machine is not having any problems with it.

- - -Updraft

 

[CorBlimeyLimey]

By flaky, I mean the facets will suddenly appear when I move the cursor, movement is jumpy like it is overloading my graphics card. It would not allow me to insert into the SWX Target part, and then for seemingly no reason, SW just locks up.

May well be my machine (P4 x32) but I just saved out as parasolid and re-imported and it is now stable.

 

[MikeWhitten]

Hello Updraft,

Mastercam has a function called "Change Recognition". This utility will compare solid models very nicely. My guess is that it works very similar to the one found in SW pro. I can not verify this as I only have the standard version. Mastercam's utility will basically check to see if the faces are coincident or not. The "CAM Result" model was created from an STL. As you already know, the faces are faceted within a specified tolerance. Most or all of the faces are not going to match the “SWX Target” model within Mastercam's system tolerance. “Change Recognition” will simply not work.

The normal way I compare models like this is to use Mastercam's "STL Compare" Function. I also have a similar function in Predator Virtual CNC(gcode verification and machine simulation software) called “CAD Compare”. They will both compare your models with ease. Please see the linked PDF for the comparison data.

Mike

http://www.cadcamcontractors.com

 

[MikeWhitten]

Hello Updraft,

I am wondering if you had a chance to look at the data I posted.

Thanks

http://www.cadcamcontractors.com

 

[Updraft]

Mike,

I just now reviewed the file. Wow, what a nice service you performed for me! It's a shame I can only reward you with one star! You gave me just the type of comparison I was looking for. The hole difference you identified on page 9 was due to my initially specifying an M10 X 1.0 thread and then changing it to M10 X 1.5 after it had been programmed. The bits revealed on pages 7 and 8 I'll look into. Thanks a ton as none of the efforts to do this in SWX worked.

For what it is worth to everyone reading this thread I have sent this to my VAR asking for them to look into it and to send to SWX corporate for them to make suggestions. There is nothing in the SWX documentation that speaks to limitations of the various techniques we tried. I'm not too happy about that. Something should have worked in SWX! I've been using this software since its initial '95 version and even before that was released (DesignView was the 2D predecessor and was awesome in its day!), but I feel SWX has let me down on this one.

- - -Updraft

 

[MikeWhitten]

Hello Updraft,

I am happy I was a help so all is well. Good luck with your project.

Thanks

http://www.cadcamcontractors.com

 

[wes5]

featurecam's part compare function is a part of their entry level surface milling product. i don't think it is a big upgrade from 2-axis milling.