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Making a working mechanical assembly

peter_sachpeter_sach Member Posts: 2 EDU
edited February 2018 in Using Onshape
I've trawled through the help files and looked on line but I've not managed to understand/solve this seemingly simple problem.
https://drive.google.com/file/d/1qIbVo1XMu_rYumKeuwH84RKBtIe32rGl/view

I want the levers on top of the cam followers to be linked/driven by the followers.  I have tried linking to the  pivot pin running across the  back.  When I make the mates it breaks the earlier ones.

If it helps heres the file
https://cad.onshape.com/documents/735c1f074b828b92a930b52c/w/f2f326afd4be90bf953dc888/e/fc400b47a3662f3ef4ae9784

Comments

  • brucebartlettbrucebartlett Member, OS Professional, Mentor Posts: 2,025 PRO
    For cams I'd be using the tangent mate. To get full rotation I'd make sure the cam shape was made with a spline, to ensure the cam shape is a single surface to make the mate work. 
    Engineer ı Product Designer ı Onshape Consulting Partner
    Twitter: @onshapetricks  & @babart1977   
  • philip_thomasphilip_thomas Member, Moderator, Onshape Employees, Developers Posts: 1,381
    @peter_sach - Onshape Mating is very powerful, but there are quite a few nuances.

    Here is how to build this assembly - please feel free to ask any questions here as others will no doubt benefit.
    The assembly structure and mating strategies are a model for you to carry forward to your other projects.



    https://cad.onshape.com/documents/24a6a73260c13a9d51c86578/w/febee0f34e27e4024910bf54/e/f097026f849ef0a27deb415f

    Philip Thomas - Onshape
  • peter_sachpeter_sach Member Posts: 2 EDU
    philip_thomas-
    Thank you so much for your reply.
    So the strategy is  top down-  child to parent once the first driving revolute mate is  made?

    This is interesting as  the "flow" for  this  was to  demonstrate the different outputs generated by different shaped cams- for young design students (12,-13 yrs  old) to experiment with.  So I  modeled the  "chassis"  put in the  axle, checked it would animate, added the  cams, made  the tangent mates to the  followers.  All worked  well then decided to attach some levers  to really amplify the  differences  in output movement.  At this point the  simulation broke.  From your part file is would appear
    1- make the animated mate
    2- make the tangent mates  on the levers to the followers
    3-make the slide mates to the  followers
    4-make the tangent mates to the cams

    BTW I was pleased to see that  the simple cams surface was  picked up (I did make  sure  that  the fillets where made in the sketch rather than rounding off after extruding.

  • philip_thomasphilip_thomas Member, Moderator, Onshape Employees, Developers Posts: 1,381
    @peter_sach - I would add to your list;
    • Add explicit mate connectors to parts that have 'difficult' geometry.
    • 'Tangent' mate is very expensive and you will note that i did not use it on the third arm (i used a slider) - faster and more robust.
    • Subassemblies subassemblies subassemblies (i think you're calling this 'top down') - keeps everything small and simple.
    Great example and thank you for spreading the good word of Onshape

    @KatieHuffman
    Philip Thomas - Onshape
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