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atc reversing error

Posted: Fri Jan 26, 2018 12:06 pm
by mfry
Hi guys. I bought this machine knowing it had an issue with the ATC. Index the carousel and it would move about two tools then error out. Wasn't getting a tool counter signal. So i replaced the proximity sensor and now it indexes fine -- until it I reverse direction. Then it stops immediately, but alt+K shows it thinks the tool has indexed. The sensor is tripping before the motor has a chance to make a full turn.
I updated the control from CNC10 1.51 to 2.72, have I simply not installed the correct plc for the tool changer?
Can I do something like add a line telling it to wait 200ms or something before looking for a tool counter signal?

Re: atc reversing error

Posted: Fri Jan 26, 2018 6:15 pm
by mfry
So after some more poking around I found the carousel rotate routine in the plc source file. The following excerpt:
if true then set Car_Motor_En,

Since the counter shouldn't signal for at least half a turn of the carousel motor, can I just put a command to wait after Car_Motor_en? What would the syntax for that be?
Also, what's the procedure for updating the plc? Edit source file, compile, reboot?

Re: atc reversing error

Posted: Sat Jan 27, 2018 8:52 am
by diycncscott
At one time, the ATC was working. If that's the case, the last place you should looking is in the PLC code. The PLC code didn't change, the ATC did.

You have a mechanical or electrical issue with a sensor. Look there.

Re: atc reversing error

Posted: Sat Jan 27, 2018 1:05 pm
by mfry
Yeah, that's an excellent point. I thought the plc code may have changed in the update, but comparing them both in notepad++ I see it hasn't. I've replaced the sensor like for like and it seems to be doing its thing so there must be something else going on or something I inadvertently got wrong on the way. Time to retrace my steps I think. Thanks for the sanity check.

Re: atc reversing error

Posted: Sat Jan 27, 2018 2:09 pm
by diycncscott
Make sure you have quench arcs on your carousel motor power leads and/or on the reversing contactor(s). Also, look for a loose leg on you 3phase in the same places.

I think there is an error message in the status window that you are overlooking. Also, ALWAYS post a when looking for help. It contains information that we need to help you.

Re: atc reversing error

Posted: Sat Jan 27, 2018 4:32 pm
by cncsnw
These carousel motors often have a built-in brake, which is released when power is applied to the motor, and re-applied when power is removed.

If yours is like that, and the brake has stopped working, then perhaps it is overshooting the stopping point and coasting until the sensor changes again. In that case, the first transition after reversal looks like arrival at a new position, when in fact it is just getting back to the center of the current position.

Look at your sensor and cam. Some Geneva cams designed so that the sensor is closed or "made" when between positions, and open or "not made" when centered in position. Others are designed the other way around. Figure out which kind you have, then watch it in operation to see where the cam actually comes to rest after moving a position or two.

If it does overshoot into the next "between-positions" state, it is possible to write PLC logic to work around that. But it is better to fix the brake.