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Constraint for came follower


New Member

I have a came path and came follower but I don't know how to constraint it. Could you help me please?



Staff member
If you mean a Cam and Follower, there is no generic constraint in Alibre that will do this. It has been requested.

If the Cam profile is circular, then a tangent constraint will work.


Alibre Super User
There's no method to create a false path with polyline and follow it with the Z axis of the follower?

It sure would be handy.

Everything else I would need to get the valve train working in this engine is there, except for that one constraint. The cam ring to lifter roller constraint is currently just circle to circle, so the lifters won't respond to the lobe.

Maybe someday!

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Alibre Super User
Is it a limitation of the ACIS kernel or an option that is not implemented in the current version?
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Senior Member
Don't know if the following is of any help. I'm not exactly an advanced user and am normally the one asking for help.

I looked up an old cam follower tutorial I've got, after seeing this thread.

The cam in that tutorial was basically made with an elipse, and the follower can be made tangent to the ellipse.
However, most cams are not an ellipse so I tried making a custom cam shape from circles, ellipses, etc, then clipping to leave the finished cam shape.
Problem with that is I could not make a tangent constraint to the entire periphery of the cam lobe. Only certain "sections" of the periphery would select.
So then I tried to make a cam from a spline, and just like with an elipse, I could constrain a circle (follower) to the full cam periphery.
As per the tutorial, I rotated the cam with "Precise Placement" and the follower moved up and down, maintaining tangency to the cam.
Of course this requires you design the cam from a spline.

Tutorial attached and a screenshot of the "spline cam" and follower I did as a test.


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Senior Member
Awesome, thanks for the feedback. Feels good being able to help, after the help I've received.

And thanks for the link, I'll see what I can learn from that.


Alibre Super User
In case anyone wants to try this. You can drag the cam but it only works correctly with Precise Placement. Click the Apply button to gain focus on it and then hold down your Enter key to drive the animation. You can change the speed and also the rotational direction of the cam, whilst it's moving, by changing the Angle Degrees entry increments of Rotation Entry (using the up-down buttons or your mouse-wheel) Obviously, a 0 degree angle pauses the animation but it starts again once you have a negative or positive entry. Checking Reverse also changes the direction of the cam, even when it's going at full speed : )

Cam and follower.jpg


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Senior Member
Thanks Miles.
I'd heard about the continuous rotation but thought I only had to keep the mouse pressed on the apply button.


Alibre Super User
You just need to click Apply once to gain the focus on it, then holding down the Enter key keeps clicking it for you : )


Alibre Super User
So, if the sketch environment allows constraining a circle tangent to a spline, it seems that it shouldn't be difficult for Alibre to incorporate a cam type assembly constraint?

Like Inventors transitional constraint?

Or, is it not that simple?