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Old 12-05-2006, 11:25 AM
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Post Machine Design - Comparing 3D CAD modelers

Comparing 3D CAD modelers
What designers should know about history-based and "dynamic" schemes

CAD software with what is called a history-based approach to design has topped the field in market share since PTC Corp., Needham, Mass., introduced Pro/Engineer in the late 1980s. About a year ago, CoCreate Software Inc., Ft. Collins, Colo., started pushing an alternative approach to 3D product development it calls " Dynamic Modeling."

November 22, 2006 Issue, Pages 66-68
Leslie Gordon Senior Editor

http://www.machinedesign.com/ASP/vie...TISSUE&CatID=3

Click here to read more published articles about CoCreate.
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Last edited by dszostak; 05-04-2007 at 02:31 PM. Reason: Added URL
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Old 12-05-2006, 10:23 PM
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Re: Machine Design - Comparing 3D CAD modelers

Nice summary. Minor addendum, David - you're quoted of saying: "Yet this ease-of-use doesn't preclude companies from designing complex products such as printer/copiers, some with over 35,000 different parts." We've actually got customers out there handling hundreds of thousands of parts...

"You call that a model? This is a model."



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Old 12-06-2006, 05:09 AM
tim heeney tim heeney is offline
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Re: Machine Design - Comparing 3D CAD modelers

That link directs to utube 'call that a knife' - quite interesting but a little sad!
Was that the intention?

Tim
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Old 12-06-2006, 05:33 AM
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Re: Machine Design - Comparing 3D CAD modelers

Hmmm, well, I thought the video is quite funny... oh, and the original "THIS is a knife" line is, of course, from Crocodile Dundee (see http://en.wikipedia.org/wiki/Crocodile_Dundee).



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Old 12-15-2006, 09:06 AM
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Re: Machine Design - Comparing 3D CAD modelers

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A few Machine Design reader responses... December 15, 2006

To answer a reader's question, CoCreate Software Inc. made a video explaining how modifications are made to the design of a shelled part in a non-history (history-free) based modeler. We (Machine Design) have posted the video on-line at the end of the article, "Comparing 3D CAD modelers" (read the article).

Again, we welcome your comments or questions. Send them in and we might post them here (Machine Design Monthly Newsletter)!

- Leslie Gordon
lgordon@penton.com
RSS feed for Leslie's blog

Addendum
A reader remarked "I enjoyed your article in Machine Design but I am wondering if you can answer a question about non-history based modelers. In your example of a simple plastic housing you do a sketch, extrude, blend and shell. This is the same as a history based modeler. Now, in a history modeler the wall thickness in the corners is maintained because the blends are above the shell operation in the history tree. How does a non-history modeler prevent the system from assuming that the shell command comes first and then would limit the size of the allowable radius based on the stability of the model.
Computers are very linear and regardless of whether a history tree is visible the operations have to be conducted one at a time - do the non-history modelers just run operations in random order until they get something stable or is there actually a history record that the user just can't edit. Either way I would be concerned that the model would be unstable as complexity increases.
Any light you can shed on this would be appreciated."

CoCreate Software Inc. responds:
We are glad to see readers are interested in the differences between history-based and Dynamic Modeling-based approaches to 3D product development. Rather than trying to describe the differences in a letter, we thought it best to simply show how a history-free system easily responds to changes with an online video. Click here to see the video.

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Last edited by dszostak; 12-15-2006 at 09:15 AM. Reason: Added Addendum
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Old 01-02-2007, 05:48 AM
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Re: Machine Design - Comparing 3D CAD modelers

I think this is one of the better articles that mention CoCreate that I have yet read in his recent push of media coverage for OneSpace Designer. Previous articles have struck me has having been transcribed from CoCreate literature, but this one seemed well balanced, accurately, though briefly, describing the differences between history and non-history based systems.

I liked how the author called CoCreate on their "proprietary term" of "Dynamic Modeling", and correctly described how history-free modelers "perform ... Boolean operations on the 3D geometry". This editor called a spade a spade.

I liked the author's house-of-cards analogy to describe history-based models, and how they can fail to regenerate if the wrong card is pulled out, but I didn't like how when describing history-free modelers she said, "When users remove a feature, the model heals itself." In theory that's what happens, but as we all know, just as with history-based models, the more complicated the model gets the more likely it is that it will fail to regenerate when you attempt to remove a feature. But unlike a history-based model that can detect where the failure ocurred and why, history-free models simply report that the attempted operation could not be completed. This is perhaps one of the biggest shortcomings of history-free modelers - when they fail to regenerate they give the operator little guidance as to where or why the failure is ocurring, and the operator must rely on educated guesswork to delete suspect portions of the model until it regenerates. I wish this had been pointed out.

I also wish the author had delved more deeply into the differences that become appearant when you try to imbed design intent into history-based vs. history-free models. She did hint at this when she described how moving faces on a block could leave a hole uncentered, and that "operatiors can center the hole, but it takes a few more steps." I wish she had pointed out what those additional steps were, and that if you want to create a constrained model in OneSpace Designer you basically have to define features twice - once when you create them and a second time when you constrain them. I wish she had also pointed out that there are many instances where you simply can't add constraints to the geometry, such as controlling the basic diameter of a tapered hole, or the X and Y dimensions of a drafted and radiused pocket.

I thought it was amuzing how CoCreate glossed over these design intent imbedding limitations by trying to redefine what design intent is, when David Szostak said, "For CoCreate, design intent is not about relationships and constraints captured in a history-tree recipie. Rather, we say design intent involves haing a final product be exactly as a designer intended." Of course, users of all CAD software packages ultimately end up with with a final product as they intended. Successfully creating a final product is not what design intent is all about (though having this functionality is certainly a huge help in creating a product). Imbedded design intent is just that - data imbedded in the model that captures and preserves the designer's intent. It is the ability to imbed logic in a model that lead the author to note, "History-based models are often called "intelligent" because they encapsulate this design intent." I wish she had dropped the other shoe by noting that history-free models are likewise often called "dumb" because they don't do this, but I guess she didn't want to be that harsh.

Steve
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Old 01-02-2007, 06:38 AM
Steve Steve is offline
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Re: Machine Design - Comparing 3D CAD modelers

Quote:
"Yet this ease-of-use doesn't preclude companies from designing complex products such as printer/copiers, some with over 35,000 different parts." We've actually got customers out there handling hundreds of thousands of parts...
Every time I read this I'm highly skeptical. At my company, we've had problems with loading and working with some of our "larger" assemblies - and they only have about 1500-2000 parts in them. It wasn't until in the last six months, when we bought new 64-bit 3+ Ghz Optiplexes, loaded them up with 4GB of RAM, and, at the direction of CoCreate, forced Windows to load in a special "3GB Mode" that we were able to open some of them at all.

If someone is using OSD to work with assemblies with 35,000 parts in it I'd love to know the file size of their assembly as a package file and what kind of system they are running.

Steve
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Old 01-02-2007, 11:45 AM
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Re: Machine Design - Comparing 3D CAD modelers

I cannot share model specifics with you because the models which we receive from customers are usually shared with us on a strictly confidential basis. But we often see models with several 10000s of parts.

If you don't trust me, check out the kind of machinery which companies like Robbins (http://www.cocreate.com/press_rel_detail.cfm?PressRel_ID=177) and Liebherr (http://www.liebherr.com/at/en/default_at.asp) are working on to get at least an impression.

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Last edited by clausb; 01-02-2007 at 11:57 AM.
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