Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: Daner on October 05, 2017, 06:55:37 PM

Title: One stepper Motor Acting Up
Post by: Daner on October 05, 2017, 06:55:37 PM
Hey all,

I have one stepper motor that likes to run backwards sometimes.
Its on the Y axis...with dual motors.
When I disconnect the the motor in question and the gantry runs smooth...no vibration or change in direction.

When I disconnect the good stepper motor and jog with the bad stepper in one direction on the key board> stop > hit same direction and some times it will go the opposite direction.
Also a bit of vibration.
Any tips or advise?

Thanks
Title: Re: One stepper Motor Acting Up
Post by: joeaverage on October 05, 2017, 07:29:15 PM
Hi,
sounds like either noise (possible) or a bad connection (probable) to the DIR terminal of your driver.

Can you connect your nominally 'bad motor' to the good driver?

Craig
Title: Re: One stepper Motor Acting Up
Post by: Daner on October 05, 2017, 07:40:54 PM
Hi Joe,
I conected the bad motor to the other Y driver, and it does the same thing.

It has a China # on it
Is this something that can be rebuilt in a local motor shop?
Title: Re: One stepper Motor Acting Up
Post by: Daner on October 05, 2017, 07:50:21 PM
Hers a pic of the motor
Title: Re: One stepper Motor Acting Up
Post by: joeaverage on October 05, 2017, 08:25:18 PM
Hi,
bad luck...I don't think it can be rebuilt. Some of the service information I've seen prohibits disassembly as it
can permanently degrade the 'permanent' magnets inside.

Craig
Title: Re: One stepper Motor Acting Up
Post by: Daner on October 05, 2017, 08:29:15 PM
Thats ok, Can I upgrade to new steppers?
Should I change both motors on this Y axis?

Thanks for your help


I would think both motors should draw the same amps
Title: Re: One stepper Motor Acting Up
Post by: joeaverage on October 05, 2017, 10:30:06 PM
Hi,
would have thought that having both motors identical would be the ideal.

Even if you found another motor with the same current rating would the  resistance and inductance of the windings
be the same?

Given that one motor is faulty would you consider another/better brand?

Craig
Title: Re: One stepper Motor Acting Up
Post by: Daner on October 05, 2017, 10:35:34 PM
I'm certain that motor is bad
I lay them both out on the table top
And it vibrates and switchs direction
The other side runs smooth.

I gather I should change them both
I'm ok with upgrading

Title: Re: One stepper Motor Acting Up
Post by: rcaffin on October 05, 2017, 10:51:02 PM
I find the idea that the motor is faulty with random direction changes almost inconceivable. Stepper motors just don't do that - they can't do that.
I would immediately expect that either the driver is faulty, or the Dir pin connections (between the PC and the driver) are faulty.

Hook the problematic motor up to a different driver and see what happens.

Cheers
Roger
Title: Re: One stepper Motor Acting Up
Post by: Daner on October 05, 2017, 11:04:42 PM
This motor is 1 of 2 on the Z axis.
#1 motor is bad
#2 motor is good

#2 motor connected to #1 or #2 driver motor runs one direction and smooth.
#1 motor connected to #1 or # 2 driver runs but with vibration also can change direction by jogging on keyboard.
I haven't checked parallel port cable
Title: Re: One stepper Motor Acting Up
Post by: rcaffin on October 05, 2017, 11:20:54 PM
> #2 motor connected to #1 or #2 driver motor runs one direction and smooth.
Good test.
Just checking: can #2 motor run in BOTH directions from either driver?

> #1 motor connected to #1 or # 2 driver runs but with vibration also can change direction by jogging on keyboard.
How very odd. I still say it won't be the motor itself. They just are not built that way.
Have you checked the connector on the motor cable? If one wire has a shaky connection, that MIGHT explain it. Maybe.

Cheers
Title: Re: One stepper Motor Acting Up
Post by: Daner on October 05, 2017, 11:54:56 PM
The 4 wires going into the motor look good.
The 4 pin connector looks good.
I will check the wire harness between the motor and the driver next

Thanks for your help

Danny
Title: Re: One stepper Motor Acting Up
Post by: Daner on October 06, 2017, 02:58:11 PM
Yes you were right!
It was 1 wire of the 4
Broke off the soldered joint
It's like a new machine now
Beers on me
Thanks for your help.

Danny
Title: Re: One stepper Motor Acting Up
Post by: rcaffin on October 06, 2017, 03:50:52 PM
We win some ...  :)

Cheers
Roger
Title: Re: One stepper Motor Acting Up
Post by: joeaverage on October 07, 2017, 12:17:12 AM
Hi,
that's good news. Excepting the rotor there are no moving parts in a stepper, it ought to be possible to make such simple devices without
fault. Roger was quite right to smell rat.

The only real quality issue I can think of that would separate good from not so good is insulation resistance, and not just the normal static tests
but the ability to withstand high voltages at elevated temperature working conditions for years at a time.
I bought Vexta 5 phase steppers for my mill and paid a real high premium for them. I wondered after I had committed to buy whether it was justified.
I also use Vexta drivers, they are 230V input with a switch mode supply to the driver.  The DC link voltage is 150V. This is the highest voltage
I've ever heard of for a stepper motor. Whether the premium I paid is justified I'm glad that Vexta quality is such that their motors withstand those
voltages under working conditions and have done for four years.

Craig
Title: Re: One stepper Motor Acting Up
Post by: rcaffin on October 07, 2017, 12:58:05 AM
Better add bearing quality to the list, plus quality of machining of the teeth.

Cheers
Roger