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Author Topic: Lathe turret lost it's mind-please help!  (Read 4171 times)

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Lathe turret lost it's mind-please help!
« on: September 13, 2012, 12:47:33 PM »
Hello all,

Having a strange issue with my turret. Has been working fine for the past year or so, but now doesn't operate properly. To home, it rotates until it hits the hall sensor, then backs off a preset amount, like any other axis. On the off chance it does this correctly, it homes correctly. In the past day or so, it has decided that sometimes it will back off correctly, and sometimes it will advance by the preset amount, not back off. Sometimes, it doesn't rotate the correct direction to get to the switch either.

Once homed, sometimes it rotates the correct direction to do a tool change, and sometimes it rotates the other direction.

What the hell is going on? I've tried changing settings, eg step direction, homing direction, ang short rot., etc. but doesn't seem to do much. I've attached my .xml, hopefully someone can spot something.

Is it possible the stepper motor is going bad, or the stepper drive? I'm using a Gecko G251 to run it.

One slight issue is that the G251 is rated for 50v max, and I'm reading 54v no load to the drive. Am I cooking it slowly?

Please help!

Thanks,
Kevin

Offline BR549

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Re: Lathe turret lost it's mind-please help!
« Reply #1 on: September 13, 2012, 12:49:02 PM »
Almost sounds like a loose DIR wire where sometimnes it changes the state and sometimes NOT.

Just a thought, (;-) TP
Re: Lathe turret lost it's mind-please help!
« Reply #2 on: September 13, 2012, 04:26:59 PM »
Thanks for the reply. I checked, but that wasn't it.  Sometimes the turret raises up, and the motor whirs, but doesn't rotate at all. Motor or drive going bad? Don't know much about steppers, so does someone have any idea what that means?

Kevin
Re: Lathe turret lost it's mind-please help!
« Reply #3 on: September 18, 2012, 06:01:38 PM »
Got it fixed. Turns out the Gecko G251 went bad. Replaced with a Keling KL-8056D. Got a few more snazzy features, and the turret now indexes faster, stepper motor runs quieter.


Kevin
Re: Lathe turret lost it's mind-please help!
« Reply #4 on: November 07, 2012, 06:22:10 PM »
And, the problem is back. Found out I got coolant in the stepper motor. Wasn't dead-shorting, but read pretty bad with a megohm insulation tester. I took the motor apart, cleaned it, dried it, and retested, and it checked out ok.  Ordered a new Keling drive on the assumption that I had burned it out. New drive installed, and the problem is just the same.

Motor goes in whatever direction it feels like. I checked the direction wiring..no trouble there. Tried using a different output pin for DIR in case something went bad on the BOB. That didn't help either. Next I'm going to try to hard-strap the DIR in on the drive to either 5v or GND and see if it consistently goes in the same direction.

What gives here? Is it possible the motor was damaged and its actually the motor running whichever way it feels, regardless of the drive's commanded direction?

Help?

Thanks,
Kevin

Offline BR549

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Re: Lathe turret lost it's mind-please help!
« Reply #5 on: November 07, 2012, 06:49:46 PM »
NOT a good idea to remove the rotor in a stepper motor. It can KILL the magnets.  BUT that does not sound like your problem. I would unhook the dir input from your drive and see IF it still flip flops. IF not it can be a BOB problem OR you still have a bad connection OR wire between the LPT port and the drive.

Just a thought, (;-) TP
Re: Lathe turret lost it's mind-please help!
« Reply #6 on: November 07, 2012, 06:53:15 PM »
Tried with DIR wire disconnected, hooked to 5v, and hooked to ground. None of these made a difference. Still goes whichever way it wants. Keep in mind, this is with a brand new drive. Just came in the mail today.

Bad motor?

Kevin

Offline BR549

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Re: Lathe turret lost it's mind-please help!
« Reply #7 on: November 07, 2012, 07:06:16 PM »
Try it with a motor off the other axis, just change out the wires and route THAT drive to one of your other motors. TO me what you are describing is a bad drive IF you disconnect the dir input and it still flip flops. OR possibly you have a ground loop causing interference.

(;-) TP
Re: Lathe turret lost it's mind-please help!
« Reply #8 on: November 08, 2012, 12:28:38 PM »
Unfortunately, that's the only stepper I have. My X and Z axes use servos. I had a Gecko drive originally that worked for about a year before this problem came up. Switched to the Keling after that because the Gecko was at max rating for voltage and I wanted something a little more robust. That drive lasted about a month. Trouble is back. But I did get coolant in the motor. Cleaned and dried the motor, plugged in the new Keling (yesterday) and didn't fix a thing. In the meantime I built a cover for that motor so coolant will never be an issue again.

As far as a ground loop issue, I have the power supply ground on the drive, but I also am using the ground from the BOB to reference the Step and Dir lines to. Maybe that's an issue?  But really, if the DIR input is tied to straight 5v, what noise is a ground loop going to contribute that would overcome that?

Thanks!


Kevin

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Re: Lathe turret lost it's mind-please help!
« Reply #9 on: November 08, 2012, 01:01:52 PM »
HOw a ground loop could effect teh drive would depend on HOW the drive was designed internally.  IF you had +5vdc and noise created -3vdc what would you have ??.

When you say power supply ground did you mean CASE ground or Power supply common ?  Is you drive case GROUNDED as well and to where. Does your drive treat COM and Grd the same or isolate them ?

Electronics in the 0-5 volt range can get complicated as to noise and interferrence from ground loops.

BUT back to the problem IF you disconnect the dir input from the drive it should NOT flip flop direction when ran.  Try isolating the drive from GRD or try grounding it .  SOmewhere there is an answer.

COuld it be a bad motor NOW that you removed the rotor(assuming that you did) it is possible that weak magnets cause a problem .

(;-) TP