Author Topic: 3 out of 4 motors behaving weirdly  (Read 667 times)

neilD321

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3 out of 4 motors behaving weirdly
« on: April 25, 2021, 09:12:28 PM »
Hi Folks,

posting here to see if anyone can point me in the correct direction.

Some background - in case it helps. I am finalising a new CNC build.
All the components have come across from a previous build and I have doubled in size and moved from a moving table to a moving gantry design.

In final testing - I have 3 out of the 4 motors behaving weirdly.
If I hold the jog button down - they shimmy a little and then take off as expected.
But if I quickly press the jog button multiple times they shimmy then move and sometimes change direction.

It's as if I'm loosing power intermittently on the Dir for some reason.
I've checked the continuity of all leads to the motors. All seems good.

The weird bit is that the new motor (bought because I now need 2 on the gantry) is working perfectly.

I'm using a PDMX-422 and new TB6600 drivers. (Although the motor that is working has it's own matched stepper driver)
Not that I think there is an issue with the PMDX-422. It doesn't matter where I plug the working motor in (X,Y,Z or A) it always works perfectly.

I've tried many settings on the steppers. Even though I want 3.0A and 1/8 microsteps. Nothing makes any difference what so ever.
I haven't changed the settings in Mach 4 from what was working previously (except to add a motor).

The motors are 3.0A Nema 23.

Does anyone have any ideas on what to try next?

Thank you - in advance.
Neil.



12strings

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Re: 3 out of 4 motors behaving weirdly
« Reply #1 on: April 28, 2021, 01:24:09 AM »
Are you sure you have the motor windings wired to the drivers correctly, and that both phases are connected?  I had seen these symptoms once long ago and I'm trying to remember what the issue was.  All I can think of now is the motor windings wiring - maybe one phase wasn't connected?????  My motor would start rough (like yours), and would seemingly pick a direction at random.  I'll post again if I can resurrect that neuron and remember exactly what my problem was.

Are these 6-wire motors?  If so, make sure you aren't using the center-tap wire.

neilD321

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Re: 3 out of 4 motors behaving weirdly
« Reply #2 on: April 28, 2021, 01:29:14 AM »
Thanks 12strings.

They are 4 wire motors.
I've triple checked the connections.
I was wondering what would happen if I swapped them (just to see) but haven't been brave enough to try that yet.

12strings

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Re: 3 out of 4 motors behaving weirdly
« Reply #3 on: April 29, 2021, 12:50:18 AM »
The 1 motor that works has its own driver that is not a TP6600, correct?

How do you have the TP6600s wired to the PMDX-422?

neilD321

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Re: 3 out of 4 motors behaving weirdly
« Reply #4 on: April 29, 2021, 01:39:34 AM »
Correct. I bought a "matched" motor and stepper. Not that that means much but it was set correctly when I got it.

Looking at say Y on J4 on the PMDX

com -> Dir -
com -> Pul -
4     -> Dir +
5     -> Pul +

to the motor

B-  -> Blue
B+ -> Red
A-  -> Green
A+ -> Black

neilD321

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(Solved) 3 out of 4 motors behaving weirdly
« Reply #5 on: May 13, 2021, 07:18:23 PM »
Found it.

Regardless of my multimeter saying continuity was OK - it wasn't.
Pulling the motors out of the machine and eliminating the new wiring from the equation has the motors running perfectly.
I have dodgy cables somewhere. Replacing now.

But thanks for your help none the less.

Cheers
Neil.
« Last Edit: May 13, 2021, 07:20:25 PM by neilD321 »