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Author Topic: Steppers making noise but shafts not rotating  (Read 43713 times)

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Offline Tweakie.CNC

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Re: Steppers making noise but shafts not rotating
« Reply #10 on: August 07, 2012, 10:45:59 AM »
Hi CES,

Just a thought, but if (with everything switched off) you rotate the steppers by hand and can feel a magnetic detent (a sort of cogging) then they are probably good and it is more likely that it is the driver board which is bad. If the steppers rotate freely without any cogging that would indicate that the rotors are not magnetized and in that case they may well behave much as you have described.

Tweakie.
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Offline CES

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Re: Steppers making noise but shafts not rotating
« Reply #11 on: August 07, 2012, 10:01:25 PM »
Hey Woodspinner,
  Nope, the shafts are only vibrating as much as the motor housing.

So here is what I know:

  The correct port address is in place
  The port is outputting pulses
  The motors are being driven by pulses
  The pulse train may not be large enough to do the work - Caution - only using a DMM! Pulses reaches 3.38V on DC and about 6V on AC
  The pulse train is always positive on A+ to A- and on B+ to B-
  Lower Slow Jog Rate causes about the same effect as dropping the Steps per or Velocity, the motors whine or grind
  When whining, no shaft movement occurs and I can make the whining go so high pitch that I can't hear it
  When grinding, the shafts move in large jumps but not in a coordinated manor
  The DC supply outputs 24.08V
  The X axis output is connected to the X motor, Y to Y and Z to Z per Mach 3 setup. This checks out with the motors.
  Hood and Tweakie have been trying to help and now WoodSpinner has joined the group of helpers.

Offline CES

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Re: Steppers making noise but shafts not rotating
« Reply #12 on: August 07, 2012, 11:16:55 PM »
Hi Tweakie, I am not able to  turn the motors. I thought this not quite right. The steppers are very strong steppers (200 inch pound?) so I did not think I should be able to turn them.

Offline CES

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Re: Steppers making noise but shafts not rotating
« Reply #13 on: August 07, 2012, 11:25:22 PM »
Ah, the steppers have that good dent feeling when I use a vise grip. Even with the motors connected to the board and power on, the vise grip is able to rotate the shaft with ease. So, can I guess the driver board is bad?

Offline Tweakie.CNC

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Re: Steppers making noise but shafts not rotating
« Reply #14 on: August 08, 2012, 01:08:10 AM »
Ah, the steppers have that good dent feeling when I use a vise grip. Even with the motors connected to the board and power on, the vise grip is able to rotate the shaft with ease. So, can I guess the driver board is bad?

Hi CES,

That is perhaps not a good assumption to make. Steppers that have stalled can actually have less torque than when they are not powered at all.

The fact that you have 3.3 Volt logic output from your Parallel port card is more likely to be the clue to the problem. If it was me, I would obtain a PP card with 5 Volt logic output and try that before anything else.

Tweakie.

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Offline CES

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Re: Steppers making noise but shafts not rotating
« Reply #15 on: August 08, 2012, 09:57:44 AM »
Hi Tweakie,

  The pulse train is being amplified by the card and the pulses I measured were at the output of the PP card. With an amplitude of 5V and a duty cycle of 10% I think I would measure about 0.05V with my DMM directly from the PP. However, with a value 24V (or something close to it) and the same duty cycle I would expect to measure a higher value at the output of the driver card which I do.

CES 

Offline CES

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Re: Steppers making noise but shafts not rotating
« Reply #16 on: August 08, 2012, 10:22:12 AM »
What company makes a good PP card and what company makes a good CNC driver board? I'd like to get them ordered.

Any suggestions?

Offline Tweakie.CNC

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Re: Steppers making noise but shafts not rotating
« Reply #17 on: August 08, 2012, 11:50:09 AM »
Gecko makes good stepper drivers and the G540 is popular http://www.geckodrive.com/featured-products.html

Tweakie.
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Re: Steppers making noise but shafts not rotating
« Reply #18 on: August 08, 2012, 12:42:31 PM »
I'm just curious, when its "whiring" have you held the shaft and does it seem to vibrate? possibly a+ and a- are reversed?

John


It does sound like it, I've got the wires the wrong way round before and as Ces explained he gets the stepper jumping around at a low pulse speed- an out of phase situation.

Test for good pulses on all stepper wires.
Re: Steppers making noise but shafts not rotating
« Reply #19 on: August 08, 2012, 01:47:42 PM »
It does sound like it, I've got the wires the wrong way round before and as Ces explained he gets the stepper jumping around at a low pulse speed- an out of phase situation.

Test for good pulses on all stepper wires.

Its easy to check too, swap the a+ and a- wires on one stepper/driver and see, you can always put them back if it doesnt make any difference, and I'll shut up.
John