Help with Camming

[Julien404]

Hi everyone!
I'm starting out with motion and was given someone else's program to try and add features. Basically, there is a spool that turns and gets material fed on. It spins in only one direction and is sitting on a axis that goes from left to right, right to left, until the system is stopped. This distributes the product evenly on the spool. They want me to add a way to immediately change the direction (going left or right) from a press of a button, without stopping the spool from rotating. In the MAPC for the camming, the axis for the L-R move is set as a slave and the spool encoder as master. The encoder is reset to 0 at every cycle (L-R-L)
My issue is, I can't find a way to stop my slave axis and change the direction.

This is the sequence i've been trying to do:
1- find out if im going from L to R / R to L
2- MAS on my slave axis
3- when my axis stops(MAS.PC), check my encoder position for the master and calculate what it should be if it was at the other point of the path (If L to R, encoder will be set higher, if R to L, lower).
4- MRP to the encoder to the position found above
5- MAPC with the same settings the original MAPC, with the difference being the cam lock position set to the position found above so that it doesnt have to pass by the positions before

My MAPC gets an error 5 (Servo Off State Error) and it just start moving again towards the right, regardless of the direction it originally had and just rams into the side of the spool.
Am I in the right direction with what im doing?
Thanks for the help!

[Julien404]

I havent mentionned it above but I am using Logix designer Version 21.03

[Peter Nachtwey]

A cam will not work.

Why can't you simply tell the linear axis to go in the opposite direction? Basically you need to ramp down the gear ratio to 0 and then back up to the opposite gear ratio so the linear is going the opposite direction. The motion controller's state machine should ramp down then ramp up going the opposite direction with no problems. This should be easy.

You can make the ramp down and ramp up distance as short as is practical for your system.

[Julien404]

So I should stop the camming, move it manually until the end of the cycle, then start the camming back up again? I can't just override the direction of the axis while in camming right?

[Peter Nachtwey]

Originally Posted by Julien404

So I should stop the camming, move it manually until the end of the cycle, then start the camming back up again? I can't just override the direction of the axis while in camming right?

NO! The linear axis is geared to the rotation of the drum. The linear axis should move one width of what ever is being wound on the drum per revolution. If the material has a width of 10 mm then the linear axis should move 10 mm per revolution. The trick is what happens when the linear axis needs to go the other direction. If the drum has an 1000 count/revolution encoder then the gearing should be the linear axis moves 10 mm/1000 counts or 0.01 mm/count. To turn around the gearing must ramp down from 0.01 mm/count to -0.01 mm/count.
A crude way of doing this is to change the gear ratio by 0.02 mm/rev so the ramping is done in 1 revolution.

A cam table takes too long to change especially if the operators can change direction at any time.

A cam table could work if the operator isn't going to try to change the direction arbitrarily. If you aren't winding and just trying to spread evenly then you must worry about how much time the linear axis spends at any one place to avoid uneven spreading of material. The gearing method will spread or wind evenly.