Helical motion using slot followers

[magneplanar]

To Mechanism Experts,

I have modeled a screw and a base plate. I also built in some constraints to simulate the screw assembly motion using a cylinder, and two slot follower points following a duplicate helical datum curve on the fixed part. I also built in servos for motion into the part and out of the part at different rates.

The motion works well in the center of the curve but gets lost and fails near the ends. I placed limits at 0.1 and 0.9 along the helical datum curve as stops for the slot follower.

I am wondering what can be done to improve this motion so I can go the full usable length of the curve. I am guessing my kinetic analysis is not set correctly.
View attachment 2862
Any comments?

 

[ecosgriff]

I would not use slot followers if you do not have to! If you only create a cylinder connection, the motion can be prescribed by a gear pair. Use a 'rack & pinion' gear pair, which requires you to define both a linear and a rotational axis. use the two axis from the cylinder, and set your stops in the same place. I'll try to make a demo model to explain it better.


-ecosgriff

 

[ecosgriff]

Here you go...


View attachment 2863


2006-11-08_112322_rnp.zip


-evcosgriff

 

[magneplanar]

Ecosgriff,

thanks for the tip...your model is WF3 so I cannot open it with my WF2, but the switch to rack and pinion seems to work better.

I started with rack and pinion, but was worried about setting the limits so I switched to a slot based on a coworkers comment.

I guess my coworker likes to do it the hard way...

have a good one,

Mag