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Animate Assembly Error- Unable to apply transform. Instance may be constrained.

monica_brunomonica_bruno Member Posts: 1 EDU
edited May 2022 in Community Support
In a student Automata project we are trying to animate the revolution of the axle/handle to see the cam rotate and the follower rods move up and down on the edges of the cams. We are getting the error "Some steps were computed, but there was an error. Unable to apply transform. Instance may be constrained." 

This process is pretty easy with other cam shapes, but snail cams always cause problems. 

We have tried changing the tangent mate to different edges/faces, filleting edges of the cam to avoid sharp corners, and much more. 

Any advice is appreciated!! We are beginner level users for a high school engineering course. Thanks in advance. 

Here is a link to the document that you can copy and experiment with: https://cad.onshape.com/documents/bcef9d432a31b71b91d337f4/w/9909ddeada9b80512dcca8c8/e/fe1f9709cda6559feacf189d?renderMode=0&uiState=6273d81bf50eaf6e2a4cf6b3


  • Domenico_DiMareDomenico_DiMare Member, Onshape Employees Posts: 85
    Hi @monica_bruno

    Nice job! your model is looking great.

    I took a look and the issue you are having is that the fillet radius on the cams is smaller than the radius of the follower.

    Take a look at the images below. The first image shows how at certain points on the cam path the follower is intersecting and touching many points of the cam. The Tangent mate is trying to keep them touching at only one location. When it hits this spot along the path where it would be touching in multiple points it can't solve for a discrete location.

    You can fix this by increasing the fillet radius of the cams to be greater than the radius of the follower. Check out the image below. You can see how it is only touching in one spot. You could also make the follower radius smaller than the cam radius instead.

    Here's a link to the document where I made the changes if you want to see what I did:https://cad.onshape.com/documents/0bdd0975a886d6dba9db9ea6/w/415e7993ea0ae2987a4b16a9/e/2f0006b4c6e57e6e8f7ec1f7

    An alternative strategy would be to change the Tangent mate selections from faces to a vertex and an edge so you don't have to worry about multiple contact points.
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