How do I make a pin follow a groove on the surface of a cylinder

[yash28101995]

I am trying to get a pin attached to a gear follow a groove cut on the wall of a cylinder using tangent relationships and different types of joints. I have tried cylindrical as built joint which lets me move the pin along the surface of the cylinder but when the groove turns upwards, the pin just suddenly goes to a new position and stays stuck there.

I have also tried using planar joint but i don't think it works on a curved surfaces. I have tried using revolute joint between the gear and the pin as well as a rigid joint. 

Any help would be appreciated.

Here's the link to my project: https://a360.co/4n7gogC

[davebYYPCU]

I suspect your deboss sketch construction.

Novel approach, multi point spline for a (mostly - half) straight line effect.

Test (if you have not already) by making the cut track construction with lines and tangent arcs.

Might help...

[yash28101995]

I did try that right after posting this. But that didn't work.

I got rid of the gear to pin because I realized the picture I had in mind was not really how things would work because the gear rotation adds another degree of movement for the pin that I hadn't calculated.

However, even without the gear holding back the pin, it doesn't follow the groove. 

Next, I will try this method and replace the spur with a rack moving up and down, driving a pinion: https://youtu.be/xz4VFDqcHlw?si=Smpv3dQOVF-W3Gg1

Hopefully that works.

[TrippyLighting]

You'd do this with a motion link and a bit of math.

The vertical raise of the helix has a constant/fixed relationship with the rotation of the helix.

The rotation of the gear via the pin can then be associated mathematically with the rotation of the helix.

You'd have to properly join join your components, first, tough 😉

Scratch all that!
The stuff is joined functionally and the helix isn't a helix.

The tangency relationship is theoretically the right thing to do but is not working here as expected.

[TheCADWhisperer]

@yash28101995 

Emboss does not create the correct cylindrical cam geometry.

This topic has been covered here many times in the past.

(Must be done either with sheet metal technique or Solid-Sweep.)

@yash28101995 

Edit:

I would probably have the Mount sub-assembly at the top level of the assembly and Grounded.

This is a long video and gets into other topics, but once you have your cylindrical Cam you can use Tangent.

https://www.youtube.com/watch?v=Wekmai5MqFM

[yash28101995]

Thankyou. I was having trouble finding resources for it because I didn't know what to call it (Barell Cam).

Your video along with a few others I found by using the right search terms gave me the solution.

[TheCADWhisperer]

@yash28101995 

I suspect that you will still have problems getting the motion to work.

This is an advanced topic.

Post back if you can't figure it out.

[yash28101995]

Oh how right you are. 

I did manage to make the groove thanks to your video. But yup, the motion still doesn't work. Here is what I have tried so far:

Cylindrical joint, tangential relationships, pin-slot joint, contact sets. I even tried to animate a simple version without all the other parts connected. Just a pin and the cam. But even then the pin refuses to follow the groove.

[TheCADWhisperer]

@yash28101995 

Attach your latest assembly here.

[yash28101995]

https://a360.co/4n7gogC

I took your advice for testing and made the mount ground to the parent. Applied a revolute joint between the mount and the cam, and made a pin and tried multiple things to make it move. Please let me know if I can provide any more details. 

I have also attached the file directly along with the link above just in case it doesn't open.

Edit: I had one other query about the video that you made. In that, the sheet metal that we used for making the groove profile was made on a portion of the cylinder. How do I make something that is exactly 360 degrees? Because when I make a cylinder that will be cut with that groove surface, it is not reaching accross the entire cylinder. I can bring it pretty close by making the straight part of the sheet very small, but maybe I am missing something.