Dynamic Block - scissor arm movement - Please help

[Anonymous]

Hello Autodesk Community,

This is my first time asking for help and I hope for a good experience!

I have been working on a dynamic block of docking drawer hardware and i am trying to make it move the right way.  I have attached it so that the community can use it.

Currently I have the parameters set up to use chain actions and it works well except the point where the arm opens, that part keeps coming apart and it doesn't quite operate correctly.  Essentially, I need the the arm to stay connected and move in as it opens because the part that attaches to the back of the cabinet and the part that attached to the back of the drawer cannot rotate and need to be stationary.

I have the block in the drawing set up as separate blocks so the geometry did not get separated, both parts of the arm are using polar stretch actions on polar stretch parameters and those are chained to a stretch action on a linear parameter that is set to its midpoint.  This caused the arms to rotate perfectly where they are attached to the stationary parts but like i mentioned above, the arms won't stay connected.

Any help will be greatly appreciated and if you use my drawing and get it working, please include an explanation of how it works.

Thanks Community!

Tiffiny

[Libbya · Accepted solution]

I usually shun parametric constraints for their inconsistent behavior, added complexity, added block size, etc (IMO they should be a last resort) ... but this is one of the few times where parametric constraints can get the job done more easily.  Without parametric constraints, using dynamic parameters/actions to turn the vertical stretch into the proper rotational angles is difficult (impossible?).  After eliminating the polar parameters/actions, adding a couple additional circles to the arm blocks, and adding 3 coincident parametric constraints, the block functions as desired.  See attached.   

[Anonymous]

Wow, I can't believe my eyes; it works!  Thanks so much.  I will work on reverse engineering this solution for my others five docking drawers.  This will be my first time using constraints and I wonder if there might be bits of wisdom you could add?

[annawalter7NSSC]

I found this helpful. Thank you.