Help with Tool Changer Program

cartierusm · Feb 12, 2017

I'm trying to control a tool changer on my retrofit CNC lathe that I built. I have experience with PLCs, but not much. I'm using a click PLC.

The tool changer has 5 proximity switches, NPN, and a combination of 3 of those switches ON is a position.

Look at the pics. When I write a program for a single position, such as the first pic, it works of course, but I can't figure out how to program it so I can press a different button to have it stop on different positions.

The second pic show basically what I want to happen. Any help would be appreciated.

robertmee · Feb 12, 2017

You're close...your first pic is what you want but instead of set/rst the output set/rst a memory bit that represents go to position 1. Then make two more exactly like the first two rungs but set/rst a memory 2 bit and a memory 3 bit. Then use those three memory bits in parallel to turn on your output with an OTE not a set.

Doug-P · Feb 12, 2017

I would:

have each X00n transitional drive its own separate Y00n latch
include in the latch (set) rungs the OFF state of the remaining Y00n outputs ( Y001 can only be set if 2,3 and 4 are OFF, and so on)
parallel all the Y00n outputs to drive one Y motor enable
use the Y00n to enable the logic for the prox switches

YMMV

cartierusm · Feb 12, 2017

I get the general gist of what you both are saying, but as I said I'm a beginner with ladder logic.

A picture would be helpful.

Doug-P · Feb 12, 2017

One possibility

robertmee · Feb 12, 2017

I don't know Click well enough to know the internal memory tags, but this should be what you need.

EDIT: Doug posted as I did, but same thing...his rungs have interlocks in the PB rung in case any other mode is active, which I don't know from limited information if you need. Also don't know if you have any STOP PB's, but those would be put in parallel with all the RST rungs.

cartierusm · Feb 12, 2017

Awesome, thanks gentleman! I'll give that a whirl and see if it works. I'll also study it to understand what it all means so I know for next time. I've done latches before with help from others on here, but don't quite grasps how they work yet. I think I need a real work example, a physical example of how they work.

cartierusm · Feb 12, 2017

Thanks Chaps, works a treat.

Now if i can figure out how to get it to stop at the correct position. It's over running by a little bit.

Is there a way to have the click plc react faster? I know you can change scan speed, would that help?

ASF · Feb 12, 2017

I doubt PLC scantime is your problem. More likely it's physical/mechanical. Relays have to switch, solenoids have to physically travel, everything has momentum and inertia...I mean, without checking out your system I can't say for certain that PLC scantime is your problem, but I highly doubt it.

cartierusm · Feb 12, 2017

True, but this is the original setup and the old electronics did the job, and they were from 1978.

After I wrote this I realized that it probably was mechanical. I then figured that the original motor, which I'm using, probably was hooked up to a VFD of sorts and that would stop it instantly. I think what's happening is it's coasting a little after it shuts off. I've got a VFD so I'll try that.

cartierusm · Feb 13, 2017

BOOYA!! It's working. Thanks for the help. I hooked up the VFD and exactly what I thought. It's working perfect now. Now I just have to interface it with my CNC program. Which I have no clue of. Off to another forum.

shooter · Feb 13, 2017

A VFD only needs a direction and a run input.
when pos > setting go back otherwise go forward.

Help with Tool Changer Program

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