Compare Geometry - can anyone get this to work?

[Simon205]

I often try to use this to see if changes I've made to a model have resulted in any subtle 'unexpected' changes elsewhere, but never have much success.

If they're really simple parts, fine, but as soon as I try running it with any semi-complex parts (mainly plastic mouldings) it take ages to compute and more often than not results in failing to compute the volume removed/added (which is what I need).

It'd be a really useful tool if it worked properly. Anyone have any suggestions?

 

[CorBlimeyLimey]

Maybe a faster CPU? More RAM?

What are your computer specs?

 

[Updraft]

Simon205,

1. Perhaps you could post a set of parts for others to try the same thing and share our results.

2. Are these different part files you are comparing or are they different "ages" of the same part?

3. Have you tried saving both files out as a parasolid and running the geometry comparison on those version?

- - -Updraft

 

[Simon205]

Hi Guys, thanks for the replies:

PC spec:
Intel Core i7 CPU 920 @ 2.67GHz
12GB RAM
ATI FireGL V7600
SW2010 SP

So I'd hope this'd be enough?

1) I'm afraid I can't post parts due to IP, but think injection moulded casings; similar to a pressure washer casing; curved geometry (but not ridiculous) with lots of internal rib/boss details, draft angles and radii on everything.

2) Yes, I'm comparing different 'ages' of the same part

3) I've just tried saving both as a parsolid, but the volume comparison still fails

 

[rstupplebeen]

I have found this tool to only work for prismatic parts. Swoopy geometry has issues because the surfaces wiggle slightly with changes and when doing a comparison 0 volume solids are created and it fails.

Rob Stupplebeen

https://sites.google.com/site/robertkstupplebeen/

 

[Updraft]

Simon205,

Since you are comparing two different generations of a part AND you are apparently familiar with the Cavity function you have available an option that will at least show you where there are differences. You can subtract version one from version two and then reverse it - version two from version one. If you have anything left from these subtractions then that is simply where you have differences.

- - -Updraft

 

[Simon205]

Thanks for the replies.

Updraft; I'm not sure how the cavity function can be used. Simply putting both bodies in the same part file and attempting a subtract results in the error:

'The feature failed to cut the body'. I guess the cavity command may try to do essentially the same thing, but may be wrong.....

 

[rstupplebeen]

My thought was that compare is simply an automated combine function using the different options.

Rob Stupplebeen

https://sites.google.com/site/robertkstupplebeen/

 

[cpretty]

Doing cavities or combines on similar parts to check for the issues explained rarely works. Zero thickness or invalid geometry are the end result often.

I have never used compare geometry. From the OP description I imagine it is a nice interface on the combine/subtract tools, so will suffer from the above.

The only method I have ever used that works but is very labour intensive is to put both parts into an assembly on top of each other and slowly work through sections on all 3 axes. By slowly stepping through the part looking at critical areas you will find these issues. It will help if the parts are different colours.

The above method has also been used extensively as a design check tool for electronics enclosures. When checking clearances etc in complex mouldings it is amazing how long it take to find some of these problems.

Craig Pretty
Tru-Design Plastics

 

[fcsuper]

When comparing two molded parts, I had a lot of success with creating an assembly and placing the two parts in the exact same location. Any surfaces that are exactly the same will be naturally zebra striped. Any surfaces that belong only to one or the other part will be the color of that part only.

Matt Lorono, CSWP
Lorono's SolidWorks Resources & SolidWorks Legion
Follow me on Twitter

 

[KirbyWan]

I've used fcsuper's idea with a section plane and it does a good job of showing any internal differences.

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

 

[EEnd]

As a work around, could you...
Use one version to create a cavity in a solid block.
Insert the other version into the cavity.
Use interference detection.

This would probably have to be done in both directions.

Eric

 

[hendersdc]

I have done it as Matt said with putting the two parts in an assembly and looking for the areas that are not striped. I find this works even better if you change the colors to make them contrast well. I usually end up with the default grey and red.

Doug

 

[Simon205]

Thanks for all the suggestions.

Yep, I too use the ad-hoc zebra stripe method which is pretty helpful, but easy to miss some small changes.

I'm suprised this hasn't been refined more by SW as it'd be really powerful if it worked properly.

I'll give the cavity/interference check idea a try; many thanks.

Cheers,

Simon