Dynomotion

Group: DynoMotion Message: 6146 From: daveymahomh600e Date: 11/23/2012
Subject: Question of the Day... Running machine into limits
Hi Everyone,

Today's question is regarding what happens when you run a machine into the limit switches.

I have been trying to reverse the axis direction of one of my slide motors for the past few days and this has resulted in several cases where the limit switches get tripped. The settings I have are to allow driving out of the switches, but it seems that once they are tripped, the current level or something drops and the machine won't move.

I have even physically removed the switches so they are no longer active, but still no motion. Then I shut off Kmotion and the machine and restart, but still nothing. The initialization program won't even complete. So I unbolt the servos, stand them on their ends on the machine bed and the initialization program works fine. I bolt them back up and everything is normal.

So I got to wondering, is there some kind of power limiter that triggers once the switches are hit? It's almost like the servos don't have enough power, once they've tripped the limits, to turn the drive screws. However I can easily turn the screws by hand with the motors removed.

Any thoughts?

Thanks,
David.
Group: DynoMotion Message: 6149 From: Tom Kerekes Date: 11/23/2012
Subject: Re: Question of the Day... Running machine into limits
Hi David,

It doesn't seem logical that your axes will initialize normally, but not when in the limit with the limits removes.  That should be an identical situation.

It would be helpful if you make observations on what is happening.  There is a fault light on SnapAmp.  What is that doing?  Is an error message printed on the console?  Which axes are enabled before and after the Initialization?

Once a current fault trips, SnapAmp is disabled for 1/2 second.  If motion is attempted during this time it will fail and after the 1/2 second when SnapAmp is re-enabled there may be such a jerk (trying to catch up) that it trips another fault.  This normally isn't an issue.  But depending on what you are doing it may be.  All the axes should first be disabled, then delay so that any previous fault clears, then re-initialize.

HTH
regards
TK