Monday, July 25, 2011

Some Fun Direct Modeling with Chain and Sprocket

I hear the term "direct modeling" being used and abuse to describe many different things. To me direct modeling refers to a CAD systems ability to interact with edges, faces, features, parts and assemblies directly during the design process. It means that the CAD system is intelligent, not necessarily the geometry. It means that the CAD system can intelligently interact with geometry regardless of how or where the geometry was created – basically; “what you see is what you get”. There is already a lot of useful information in a solid body. A direct modeling system should be able to recognize this and take advantage of it. Here's an example.
Below is a video I created after doing some direct modeling with some drive chain and a sprocket using Creo Elements/Direct Modeling. As I mentioned in the video I am not sure how useful this is in the real world, but I found it interesting and wanted to share it. I personally have not done much design with drive chain since my brother and I designed and built a go-cart, about a thousand years ago. The chain kept falling off on those tight corners, (and I lost part of my eyebrow on another tight corner. "Wear a helmet, stupid" - Whatever!).
Chain is interesting simply due to the relationship from one link to the other. By recognizing the physical properties of the solid bodies that make up the chain, you can visualize some of these interesting behaviors, especially as it interacts with the sprocket.
For this example I started out by downloading the sprocket and chain in STEP format from a 3D content web site. I then created the simple shaft in the center of the sprocket. All parts are dumb solids, and there are no assembly relationships to begin with. In the “Position” function of Modeling there is an option called “Physical”. If you turn this option on, the system will recognize the physical properties of the 3D solid models, and recognize the relationships between models in real time (or very close to it). You will notice that I do eventually put a fixed relationship onto the shaft, but I apply no other relationships to the models or assembly. There are no “user defined” relationships defined between the chain and the sprocket, and there are no assembly references. What you see is what you get.

What I find interesting is the various ways of using the “Relations” capability together with the “Physical” option when moving parts. The system doesn't recognize gravity, acceleration or anything like that so it’s not doing kinematics. It simply knows moments of inertia, CG and the fact that these models are solid. And best of all – it makes no difference how the models were created or assembled, and on what CAD system they were created or assembled, (just had to throw that in).
Paul

10 comments:

Scott Morris said...

Very cool how the chain interacts with the sprocket. This could make a really nice video of how to add/remove the drive chains of a FIRST FRC robot ;-)

Paul Hamilton said...

Scott, You're the one that got me thinking about this :)

Don said...

Wow, very cool stuff Paul, thanks for sharing it.

Greg Matelich said...

Nice demo - thanks. I had to do a similar layout using igus cable chain using Modeling with Physical when our other CAD software couldn't solve so many constraints.

Paul Hamilton said...

Don, thanks for the comment.
Greg, great to hear from you, and thanks for the real life example. It's great to hear from a real engineer/user!!

Tomzone said...

HI PUAL I ALREADY DOWNLOAD FREE VERSION FROM PTC ALSO CAN DO SPORKET AND CHAIN MOVE YOURS ? ISEE UR CREO HAVE
Relations” capability together with the “Physical ME DON'T HAVE PLS HELP .. I WAITING UR REPLAY THZ.. :)

Paul Hamilton said...

Tomzone, the free edition does not include the functionality to do this. Sorry about that.
Paul

Anonymous said...

Hi Paul
thanks for sharing. This new functionality if ProE (Creo) can be very usefull for chain manufaturers or Machine manufacturers who use chains (sometimes hundres of meters of chains in there machine).

This video made me think of many new possibilities but also how Creo will actually a proper model of a chain (with a prt for each component, clearance between bush and roller, and bush and pin) etc...

I will ask our VAR for further demonstration and proper case study revelant to our business.

I see another good reason to move from WF4 to Creo.

Is this module (Physical ??) whatever his name is part of the standard licence or does it have its own licence such as AAX, Piping&Cabling etc...). Luckily this is part of Mechanism Design :)

Thanks

Paul Hamilton said...

Anonymous,
Thanks for the comments. Just to clarify, the product that I am showing in the video is Creo Elements/Direct Modeling, not Creo Parametric (Pro/E). What I do with the chain is made possible by combining a 3D parametric solver with direct modeling capabilities. When I select the “Physical” switch on, it engages the parametric solver in real time. This does require the Advanced Modeling extension to Elements/Direct to work (the parametric solver comes with this extension). Creo E/D Modeling is compatible with Creo Parametric, so you could take Creo Parametric models into E/D Modeling and perform this same function – the models can come from any source.

Hope that helps,
Paul

Anonymous said...

Hi Paul
Thanks for your reply (and sorry for so many typo and missing words :O)

I am not yet familiar with the new family of products for Creo but I'll let our VAR do our education :)

Have a good day