Hello Guest it is July 24, 2019, 03:40:23 AM

Author Topic: Motors stalling, losing steps  (Read 21245 times)

0 Members and 1 Guest are viewing this topic.

Offline simpson36

*
  •  1,374 1,374
    • View Profile
Re: Motors stalling, losing steps
« Reply #10 on: December 30, 2008, 05:19:13 PM »
Unless i missed something, you did not say what you are driving the Kelings with.

If you are using Geckos, I can tell you that if you have the resistor set higher than the motor spec, the motor will stall randomly. I found this out by accident when I hooked a 4 amp stepper to a Gecko (203v) that still had a resistor for a 6 amp motor on it. Stall, stall, stall. Calculated and changed the resistor and all was well.

Just today I posted another accidental discovery. My wireless network adapter causes the steppers to behave exactly as you describe. I  don't know what part of the electronics it is effecting, but unplugging the wireless adapter cures the problem.

Offline Hood

*
  •  25,849 25,849
  • Carnoustie, Scotland
    • View Profile
Re: Motors stalling, losing steps
« Reply #11 on: February 05, 2009, 06:13:32 PM »
Its been a while since I set up steppers but I am curious where you have the resistors? You say its between pin 1 and 5 on the motor, are you meaning the drive? and if yes is that the current set pins on the G540 as I am not familiar with them.
Hood
Re: Motors stalling, losing steps
« Reply #12 on: February 05, 2009, 11:07:49 PM »
From Gecko:

RC

Offline simpson36

*
  •  1,374 1,374
    • View Profile
Re: Motors stalling, losing steps
« Reply #13 on: February 06, 2009, 04:53:25 AM »
Couple observations:

First, you have the motor set up parallel which is 4.2 amps. The 540 drive specs at 3.5 max

Second, your resistor is off by a factor of 1,000

You might consider wiring the motors as series and note the 'K' (thousand) next to the resistor ohm spec.

Offline Zaae

*
  •  115 115
    • View Profile
Re: Motors stalling, losing steps
« Reply #14 on: February 07, 2009, 10:45:22 AM »
Just for the sake of helping others, I'm going to post my latest findings.

After speaking with the very helpful tech support at geckodrives, I learned a couple things. First off, Parallel mode for these motors is supposed to be fine, though if I were to keep it in parallel, a 3.3 ohm resistor on the set pins would have worked, because the G540 will limit its output to 3.5 amps anyway.

I was getting a reading of around 80 degrees C, and it was making me nervous. According to tech support, this is normal, and acceptable (up to 100 deg C), however for the sake of not burning myself on the motors during tool changes, and the longevity of the motors and drivers, I decided to rewire in series.

My latest problem was this mysterious ticking noise coming from the motors (all of them, on any axis), with a steady, repeating 'skip' in the motor about every second or so.  This skip was (and still is) causing stalling when the motors are run at moderate speeds. I did everything I could think of to the computer. It's a 3 ghz pentium, with bare-bones windows xp on it. I did all of the performance suggestions from the support area here, along with every other tweak and setting I could think of with NO CHANGE. I just could not get rid of it.

More or less by accident, we found out in the end that it has something to do with the jog keys. I haven't found a way around it yet, but if I give a motor a G0X1000 command, it will run smooth as can be, but if I hold a jog key down, I get the ticking (and stalling) which still needs to be sorted out, as I can't have the motors stalling during jogging over for a tool change. I'm going to try a specific keyboard driver rather than the windows system one, and see if that helps.


Offline Hood

*
  •  25,849 25,849
  • Carnoustie, Scotland
    • View Profile
Re: Motors stalling, losing steps
« Reply #15 on: February 07, 2009, 10:54:48 AM »
Try setting a pulse width of 10 and see if that helps, or try sherline mode, I seem to remember some people needing Sherline for the g540's.
Hood

Offline Zaae

*
  •  115 115
    • View Profile
Re: Motors stalling, losing steps
« Reply #16 on: February 07, 2009, 01:35:24 PM »
Hood, I tried the pulse width, along with, or without sherline mode, but then the motor just turns very rough. Gecodrive says to use a pulse width of 2, which does seem to be the best.

You know, the more I work on this, the more I think I've got some sort of voltage drop, or signal noise. While a jog key being held does cause minor twitching of the motor, there's still something else. I thought we had it figured out, until I let it run some straight line programs, 300mm one way, 300mm back. Sometimes it's within 5 seconds of starting the program, sometimes it takes 30 seconds or more, but I can hear the motor 'twitch' once in a while, and it usually stalls if there's any load on it. If I put the motor on the table and run the program, when the twitch happens, it actually jumps, like it tried to change direction, or stop instantly for just a split second.

I've been reading looking for how to hook up a capacitor to filter the power supply, but the numbers I was coming up with weren't in the realm of reality. Geckodrive says:

(80,000 * I) / V = C
Example: Using a power supply of 65V and 5A, the equation would look as follows:
(80,000 * 5) / 65 = 6153µF
So, for me it's like this:
(80,000 * 19amps) / 48volts = 31666µF capacitor ... I think I might have a hard time finding a cap like that around here ..

The last thing I thought of is line noise, but I have a spare motor with the factory wiring, hooked right up to the driver, and the twitch is still there.

EDIT: I wanted to mention that this problem has existed ever since my first setup of this machine. I started with a hobby cnc drive, and that did it too. I've tried a completely different computer with a fresh install of windows xp and mach 3. I bought this new G540 drive. I have a couple power supplies, ranging from nothing more than a rectifier and capacitors on a transformer to an vending machine power supply, and several others. I've tried unipolar, bipolar, parallel and series wiring.

I may go bald by the time I figure this out >.<



« Last Edit: February 07, 2009, 01:48:30 PM by Zaaephod »

Offline Hood

*
  •  25,849 25,849
  • Carnoustie, Scotland
    • View Profile
Re: Motors stalling, losing steps
« Reply #17 on: February 07, 2009, 01:51:42 PM »
You can connect as many capacitors in parallel as you need to get the value required. So at the moment you have no capacitance at all?
Hood

Offline Zaae

*
  •  115 115
    • View Profile
Re: Motors stalling, losing steps
« Reply #18 on: February 07, 2009, 01:59:26 PM »
No, I'm using the vending machine power supply that is supposed to be regulated. Ooh, I found some 6800µF caps, I have 3 of those .. that gets me closer..
I appreciate your help more than you can imagine :)
« Last Edit: February 07, 2009, 02:04:30 PM by Zaaephod »

Offline Hood

*
  •  25,849 25,849
  • Carnoustie, Scotland
    • View Profile
Re: Motors stalling, losing steps
« Reply #19 on: February 07, 2009, 02:09:55 PM »
9 caps wired in parallel is not a problem, I had more than that on a machine a while back, see pic, there are 5 large caps and 6 smaller ones.
However your current may be on the high side, how many axis do you have?

Hood