Author Topic: Problem with stepper motor  (Read 163 times)

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Offline Fusco96

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Problem with stepper motor
« on: January 28, 2019, 12:22:40 AM »
I have a 3 axis CNC.

There is a problem running only the X-axis motor. It sometimes misses rotation and in that miss there is a noise coming from within the motor which sounds like gears grinding against each other. At other times it just completely stops while running, with the same background noise coming from the motor.

Peculiarly it happens at only 2 spots along the X-axis. Y and Z axis run fine. Redid my wiring as earlier it was messy and I thought that some noise might be interfering with the signal wires going to the motor driver, but that did not help.

Any help is much appreciated.

Thank You

Offline joeaverage

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Re: Problem with stepper motor
« Reply #1 on: January 28, 2019, 12:30:12 AM »
Hi,
sounds like the X axis motor is missing steps and/or stalling. Losing steps,either intermittently or continuously,
is a result of overload. In your case it sounds like the X axis is binding at a couple of locations. Disconnect the shaft
of the motor and turn the ballscrew by hand throughout its travel to detect binding or tight spots.

Craig
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Offline Fusco96

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Re: Problem with stepper motor
« Reply #2 on: January 28, 2019, 12:33:02 AM »
We did that, but did not feel any additional torque requirement needed to rotate the ballscrew at any point

Offline joeaverage

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Re: Problem with stepper motor
« Reply #3 on: January 28, 2019, 12:41:29 AM »
Hi,
then you will have to reduce both the velocity and acceleration to bring your machine torque demands
back to within the specs of your motor.

Craig
My wife left with my best friend...
     and I miss him!

Offline Fusco96

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Re: Problem with stepper motor
« Reply #4 on: January 28, 2019, 12:42:56 AM »
Thanks, will try that and get back to you

Offline Fusco96

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Re: Problem with stepper motor
« Reply #5 on: January 30, 2019, 08:18:19 AM »
We tried that, brought it down to its lower limit, which is practically not feasible. Though as we kept going down the frequency of those stops occurring decreased, they were not completely gone.

Offline joeaverage

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Re: Problem with stepper motor
« Reply #6 on: January 30, 2019, 12:44:21 PM »
Hi,
that the stops/stuttering decreased suggests that the X axis motor is overloaded and decreasing the speed reduces the overload,
hence the improvement.

There are some possibilities that need to be worked through.

First the motor could be faulty. Can you swap it for either the Y or Z motors?
The driver could be faulty. Can you swap either the Y or Z drivers?

If neither help then you will have to replace the motor with a more powerful unit. Note that steppers are sold on the
basis of their holding torque. That is only half the picture. Often high torque comes at the expense of high inductance
so the motor can only produce high torques at low speeds. Thus often a seemingly good and torquey motor will actually
perform less well than another which despite having lower holding torque has lower inductance and out perform the larger
motor at speed.

What voltage are your drivers rated to? All steppers lose torque the faster they go. One way to try to counteract that is to use
the highest voltage your driver can handle. Good brands like Geko will be rated to 72V.

Craig
My wife left with my best friend...
     and I miss him!

Offline Fusco96

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Re: Problem with stepper motor
« Reply #7 on: February 07, 2019, 07:24:39 AM »
Hi,
We simply kept reducing the acc and velocity till we got smooth movement by the motor. Even though it works right now, I am not convinced with this solution. If there is anything else that can be done, pls let me know.

To answer previous suggestions, we did swap motors and drivers, but the problem's only there on the X-axis