PIN IN CURVED SLOT

gerald_friedman

Is there a way to put a pin in a curved slot and run it end to end?

gerald_friedman

Forgot to add...Without using the tangent mate.

Also need to be able to rotate the pin as it moves in the slot.

mahir

I'm not aware of any way to do this without some version of a tangent mate. Why are you opposed to using one? As a general solution to making a part follow a path, you would create a dummy slot surface and if necessary a dummy roller. To keep the pin centered in the slot you would offset the path slot surface accordingly. You then fasten the two dummy parts to the parts in question, add the tangent mate, and then hide the dummies. You'll also need a planar mate to keep the roller from moving axially. It should move smoothly as long as there are no indeterminate points where the roller can be tangent to two points at once.

https://cad.onshape.com/documents/57acdfaae4b005c413ed9b6f/w/3fd585a46d3af1b3ba413c53/e/c23e5f039ae4d2f5baec1c92

gerald_friedman

Never mind. Figured out a way to do it.

Used a bunch of tangent mates and a cam to turn the shaft.

Tricky application.

alnis

Here's a quick way to do it:

1. Create a dummy surface on the tip of the pin
2. Add a mate connector to the center of the dummy surface and offset it the radius of the slot (or create it in context at the center of the slots' arc)
3. Add a revolute mate between the dummy's mate connector and one at the center of the slot & add angle limits to keep it in the slot
4. Add a revolute mate between the dummy's center and the pin's center

Hope this helps!

https://cad.onshape.com/documents/507a0b6f5598526b0901568f/v/553abcc1fc688cff8743522a/e/96531f6f9ec76ed5689e4b08

matthew_stacy

@alnis_smidchens, that is an extremely clever trick placing an offset mate connector on the dummy surface.  I borrowed and expanded on your idea.  @gerald_friedman, is it your intent that the pin is just free to rotate?  Or is your goal to achieve rolling contact between pin and wall of slot?

I assumed the latter.  I widened the slot to provide positive clearance and positioned the pin such that it registers on the inner face of the slot. The model could just as easily be configured with the pin registering on the outer face (but not both).

I also added a gear relation between the two revolute mates based on the ratio of the radii of the contact surfaces (24mm/6mm = 4:1).  Animate the revolute mate labeled virtual pivot to set the assembly in motion:

• https://cad.onshape.com/documents/6fe2e1bf3963231e9daf9fed/w/ccf86c9f9b498ecb8114c46d/e/00ff6d0688667584ec3d6873

gerald_friedman

Mathew,

Not rolling contact. There's a cam driving an arm attached to the pin.

gerald_friedman

Tried to put movie in but failed. Obviously don't know how.

gerald_friedman

I down loaded LICEcap and tried to make a GIF of my pin in curved slot application to post.

LICEcap took a picture of the desktop right through the browser image.

Anyone know what I did wrong?

gerald_friedman

Finally figured out what was wrong with LICEcap recording.

So here is the pin in curved slot driven by a cam.

bert_fourie

I wonder if somebody can help me. I created a surface to define a path for a pin to follow. However, when I go to select the face mate of the curved surface it only selects a part of the face - I assume it is because of the vertices on my curved face. How can I get rid of that so that the entire curved face is selected?

bert_fourie

I was able to turn the shape into a spline and then extrude it.