Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: BarryB on April 24, 2011, 12:13:20 AM
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Hello, I have a stepper motor that seems to not run occasionally. Other times it works fine. Of course this motor is on a twin X axis, meaning that the x-axis has two stepper motors each with the same signal. When one fails, this moves only 1/2 of the machine, which is very very bad! Basically worst possible one to go out.
Is this a normal symptom that you guys have seen? I'm wondering if I need to order a new motor, or I need to investigate something else. When they go out, do they act flakey and then finally give up the ghost, or do they just go out immediately!
This is a NEMA 34, 1290 oz motor. It's moving a gantry that weighs probably 250 lbs.
Barry
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It is FAR more likely to be the controller, or wiring than the motor.
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The controller is the same for both X axis stepper motors, so if it works on one, it should work on both. I'll check the wiring. I hope it isn't mechanical. That's the part that scares me, and the mill is big and heavy.
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If you're really running two motors in parallel on a single controller, that could well be your problem. That will not work reliably.
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why wouldn't that work reliably Ray? The signal (from a C23 board) is split and both motor drivers (gecko 203v's) receive that signal. Or were you thinking I was using one motor driver for two motors?
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why wouldn't that work reliably Ray? The signal (from a C23 board) is split and both motor drivers (gecko 203v's) receive that signal. Or were you thinking I was using one motor driver for two motors?
"The controller is the same for both X axis stepper motors, so if it works on one, it should work on both." - So now you're saying it's NOT the same controller for both. Each motor has it's own G203V, right? So swap the motor wires between the two G203Vs. If the problem moves to the other motor, then you have a G203V that is either hosed, or improperly setup. If not, then swap the motors themselves. If the problem follows the motor, then you have your answer. If not, then the problem is mechanical. Steppers will almost always either work correctly, or not at all.
My money would be on a mechanical problem....
Regards,
Ray L.
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Yes, I think we got crossed on the terminology. I'll try and narrow this down. I did notice that a coupler was busted when tearing this down, so it could be that, or that could be causes by the motor not turning. Oh the joy;)
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When you connect two drives to one output, you pull twice the current from that output. If the current on one of the lines going to the drive drops below what the drive needs, the drive will act as if it is missing steps, or worse case, not work at all. It's not reliable because sometimes it works and sometimes it doesn't.
You should be running a slaved axis. Let Mach send step and dirextion signals to the A axis on the BOB and connect your A axis drive to the A axis on the BOB. You already have the parts to do it. You just need to rewire a little and set up the A axis in Mach.
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I have a 6 axis mill, all the axis are already taken up from the C23 board;)
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swap driver boards and see if it moves to the other motor.
And how long have you run it it before this started?
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I have a 6 axis mill, all the axis are already taken up from the C23 board;)
Then you can build an amplifier circuit that would provide the same output current to both drives.
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I'm just noticing this now. The mill did sit for about 4 months but didn't do this before. (I know, rediculous letting your mill sit that long). I've just made a new control box. Since the old mill wiring didn't reach the new box location, rewired the mill too, so I'm back to basically first time operation again. Fun stuff, not.
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You should be running a slaved axis. Let Mach send step and dirextion signals to the A axis on the BOB and connect your A axis drive to the A axis on the BOB. You already have the parts to do it. You just need to rewire a little and set up the A axis in Mach.
What he's done should work just fine. AFAIK, the only thing he's lost by NOT setting it up in Mach as a slaved axis is the ability to "zero" the slaved axis through the GUI.