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Multi-level Motion skeleton?


Multi-level Motion skeleton?

I have a very large multi-level assembly. I'm trying to use motion skeletons to tie everything together, however, it is not working as I would expect. I've created one motion_skeleton assembly and placed them in each assembly. See the example structure below:












Now you would think if you moved the motion skeleton MOTION_SKELETON.ASM under ASM03.ASM the motion skeleton under ASM05.ASM would update as well after a regen or something as it is the same assembly. It does not. You can move either motion skeleton in either assembly independent from another as if they were entirely different assemblies. Is this how motion skeletons were indended to act? I've watched as many motion skeleton tutorials as I could find and nothing addressed multi-level assemblies. I would like to use motion skeletons as it has the benefit of mechanism analysis and regular skeletons do not. Anyone have any ideas on how I can get this to work?


Re: Multi-level Motion skeleton?

I would use Mechanism if you have it.......

Re: Multi-level Motion skeleton?

I do but obviously with large multi-level assembies this is not a solution if you do not want to use external references. These are models of a combine with hundreds of assemblies and thousands of parts. We usually use regular skeletons and that works as described in my first post but would like to utilize motion skeletons for it's additional features.

Re: Multi-level Motion skeleton?

Indeed this is how motion skeletons are supposed to act, just like mechanisms without skeletons.

If you would like copies of mechanisms to "synchronise", you could:

- use snapshot contraints

- forget about sub-assemblies and move all parts to the same assembly

- add regeneration positions in the motion skeleton contraints


Re: Multi-level Motion skeleton?

Thank you for your suggestions. As I understand the whole point of motion skeletons is that they act like a both regular skeleton and a mechanism. But according to your explanation motion skeletons are no better than a regular mechanism. If this is the case then motion skeletons would be redundant, which doesn't mean what you say isn't true.

As to your other suggestions

  • Snapshot constraints - These are difficult to maintain as they go out-of-date the moment anything in the model changes. I could setup the constraints each time but since I may have as many as 50 subassemblies that each contain the motion skeleton it would be very time consuming to setup the constraints each time I wanted to move a particular model.
  • No sub-assemblies - Moving all the parts that are contained in the model of a combine into one assembly isn't practical. There are thousands of parts, hundreds of weldments, and hundreds of other assemblies. We definitely need subassemblies to have any hope of organization. Regardless this isn't as option as the company has specific standards on how the model tree is to be organized.
  • Regeneration positions - Doing this would mean you could only ever see everything in one default position, you could never actually do any motion analysis. If I wanted to move something to other position then I would be back to square one - only one assembly will move while the surrounding assemblies with the same motion skeleton do not move.

Thanks again for the suggestions. I have also thought of these and tried them but they ended up being dead ends.

Re: Multi-level Motion skeleton?

I Believe tha advantage of motion skeleton is to quickly create a mechanism without investing time in solid modelling, especially useful for new concepts (of which you actually DO know how you want it).

perhaps you can share a bit about what kind of mechanism you want to work simultaniously with copies?

What do you mean with external references when mechanism was suggested?

I use mechansim all the time in large assemblies and I would use eg. a servomotor or initial force from the skeleton model to have eveerything work simultaniously in the main asm.

There is actally something in between: "mechanism connections". You can only create these in mechanism but they remain active in normal mode; eg. gears. You can link connections in the main asm using these, the motion skeletons dont even have to line up to be connected!

Re: Multi-level Motion skeleton?


Did you ever get your multi-level motion skeletons to work out?

I'm have issues making a bearing turn, trying to use motion skeletons as you did. I can place all of my skeletons, but cannot make it work when defining the gear pair inside the bearing assembly, yet I cannot define the pair in the high level assembly.


Re: Multi-level Motion skeleton?



I think you dont quite catch the idea and the implementation is wrong.

Try building something like:


- Motion skeleton.asm

- - Body skeleton.prt

- - Module 1 skeleton.prt

- - Module 2 skeleton.prt

- - Module N skeleton.prt

- Module 1.prt

- Module 2.prt

- Module N.prt


Any top changes of your architecture should be in one place (few sketch features). You can use body for creating cs for each module if you dont want to place each module in the center. This natural order should prevent any regeneration issues. You can test your skeleton motion through mechanism app before adding the solid geometry.