Stepper motor skipping steps when going slow, runs smooth when moving fast.

[case...@gmail.com]

Hi all,

I've been trying to bring back an old 3D printer to life after the brains of it died 4 months ago. I've replaced the original PCB with a smoothieboard, and have almost everything working except for the stepper motors. I've been having weird issues! Here are the juicy details, and everything I've already tried. Stepper motors are Kysan 1124090

Using the Smoothieboard default settings, the stepper motors will move, but they are skipping tons of steps, and they "grind" as they move. This happens on every axis, as well as the two extruder motors. When the motors are not moving, I can push on the motor and it will resist the push of my hand with a fair amount of force. If I push the print head in the direction of movement while it's grinding along, it will smooth out and move properly. If I change the speed of the motors in the configuration settings, or use Pronterface to force a fast speed, the motors move much smoother, but still skip a few steps. If I change the acceleration to a lower value and tell them to move at a high speed, the motor will not move, then slowly start moving while grinding horribly, then move smoothly (but still skip some steps). Obviously that's not going to work for a real 3D print. The motors all do this even when I disconnect the belts.

I've ensured the wires are hooked up right. Of the 4 wires of the stepper motor, the first two (AA) are connected together (verified with a multimeter), and the third and fourth are connected together (BB). There are no shorts between any wires other than these. I've fiddled with the speed settings and the microseconds_per_pulse settings, but I can't get the system to move slowly! I've also tried different wire connection combinations, and none of them work any better.

I'll be at work tomorrow and can provide live updates if anyone has any ideas, and scope outputs if anyone really wants to get into it. I can also take videos of behavior if someone has some different settings for me to try. I've been fighting with this for days and am positively stumped.

Thank you!

[Arthur Wolf]

Do you have another PSU you can try in the machine ? Also do you have any other kind of stepper motor you could try ?

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[case...@gmail.com]

I've got another power supply, but I've checked the voltages while the stepper motors are going, and it's steady. No other stepper motors, but the behavior is the same among all 5 of them in the 3D printer. In the documentation it says:

Ideal stepper is (for reprap printers and similar small CNC using microstepping drivers on 12-24v supply) NEMA17 size, rated 1.5A to 1.8A or less, 1-4Ω winding resistance, 3 to 8 mH, 62oz.in (0.44Nm, 4.5kg.cm) or more of torque, 1.8 or 0.9 degrees per step (200/400 steps/rev respectively), for example the kysan 1124090/42BYGH4803 or the rattm 17HS8401 or Wantai

I might order some different stepper motors, but they'll take a while to show up. I'm hoping someone somewhere has the same model and can test it with the default configuration settings.

[Arthur Wolf]

On Fri, Oct 7, 2016 at 9:47 AM, <case...@gmail.com> wrote:

I've got another power supply, but I've checked the voltages while the stepper motors are going, and it's steady.

I know it's far fetched, but would you mind trying it anyway ?
 

No other stepper motors, but the behavior is the same among all 5 of them in the 3D printer. In the documentation it says:

Ideal stepper is (for reprap printers and similar small CNC using microstepping drivers on 12-24v supply) NEMA17 size, rated 1.5A to 1.8A or less, 1-4Ω winding resistance, 3 to 8 mH, 62oz.in (0.44Nm, 4.5kg.cm) or more of torque, 1.8 or 0.9 degrees per step (200/400 steps/rev respectively), for example the kysan 1124090/42BYGH4803 or the rattm 17HS8401 or Wantai

I might order some different stepper motors, but they'll take a while to show up.

You don't need to, this was just in case you had some around.

 

I'm hoping someone somewhere has the same model and can test it with the default configuration settings.

On Friday, October 7, 2016 at 12:43:01 AM UTC-7, Arthur Wolf wrote:

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[case...@gmail.com]

I know it's far fetched, but would you mind trying it anyway ?

For sure, I'll give it a try tomorrow. I've got a lab power supply that should work.

On Friday, October 7, 2016 at 12:52:09 AM UTC-7, Arthur Wolf wrote:

On Fri, Oct 7, 2016 at 9:47 AM, <case...@gmail.com> wrote:

I've got another power supply, but I've checked the voltages while the stepper motors are going, and it's steady.

I know it's far fetched, but would you mind trying it anyway ?
 

No other stepper motors, but the behavior is the same among all 5 of them in the 3D printer. In the documentation it says:

Ideal stepper is (for reprap printers and similar small CNC using microstepping drivers on 12-24v supply) NEMA17 size, rated 1.5A to 1.8A or less, 1-4Ω winding resistance, 3 to 8 mH, 62oz.in (0.44Nm, 4.5kg.cm) or more of torque, 1.8 or 0.9 degrees per step (200/400 steps/rev respectively), for example the kysan 1124090/42BYGH4803 or the rattm 17HS8401 or Wantai

I might order some different stepper motors, but they'll take a while to show up.

You don't need to, this was just in case you had some around.

 

I'm hoping someone somewhere has the same model and can test it with the default configuration settings.

On Friday, October 7, 2016 at 12:43:01 AM UTC-7, Arthur Wolf wrote:

Do you have another PSU you can try in the machine ? Also do you have any other kind of stepper motor you could try ?

On Fri, Oct 7, 2016 at 8:33 AM, <case...@gmail.com> wrote:

Hi all,

I've been trying to bring back an old 3D printer to life after the brains of it died 4 months ago. I've replaced the original PCB with a smoothieboard, and have almost everything working except for the stepper motors. I've been having weird issues! Here are the juicy details, and everything I've already tried. Stepper motors are Kysan 1124090

Using the Smoothieboard default settings, the stepper motors will move, but they are skipping tons of steps, and they "grind" as they move. This happens on every axis, as well as the two extruder motors. When the motors are not moving, I can push on the motor and it will resist the push of my hand with a fair amount of force. If I push the print head in the direction of movement while it's grinding along, it will smooth out and move properly. If I change the speed of the motors in the configuration settings, or use Pronterface to force a fast speed, the motors move much smoother, but still skip a few steps. If I change the acceleration to a lower value and tell them to move at a high speed, the motor will not move, then slowly start moving while grinding horribly, then move smoothly (but still skip some steps). Obviously that's not going to work for a real 3D print. The motors all do this even when I disconnect the belts.

I've ensured the wires are hooked up right. Of the 4 wires of the stepper motor, the first two (AA) are connected together (verified with a multimeter), and the third and fourth are connected together (BB). There are no shorts between any wires other than these. I've fiddled with the speed settings and the microseconds_per_pulse settings, but I can't get the system to move slowly! I've also tried different wire connection combinations, and none of them work any better.

I'll be at work tomorrow and can provide live updates if anyone has any ideas, and scope outputs if anyone really wants to get into it. I can also take videos of behavior if someone has some different settings for me to try. I've been fighting with this for days and am positively stumped.

Thank you!

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[wolfmanjm]

kysans work best at around 1 amp, 1.2 amp for extruders, make sure you have the current settings in config set correctly. or do M503 and look for the M903 line.

I presume you are using a genuine smoothieboard?

[case...@gmail.com]

Gotcha, I'll try that. Do the steppers for the XYZ axis work best at those settings too, or just for the extruders?

Also, I was looking into the datasheet of the stepper motor drivers, and I see that on the smoothieboard, there are jumpers for changing the microstepping to 1, 1/2, 1/4, or 1/16. Might that be contributing? I'm going to try changing them. I was also looking at the ROSC pin on the A4982 stepper motor drivers, but don't quite understand how they work. Might that be anything?

Datasheet: www.allegromicro.com/~/media/Files/Datasheets/A4982-Datasheet.ashx
Smoothieboard scematic: http://smoothieware.org/smoothieboard-schematic

I just got to work and need to take care of a few other things first, but I'll get working on the printer soon and give an update.

[wolfmanjm]

no do  not touch the microstepping. 1/16 is perfect.

I use 1 amp for XYZ and 1.2 for E

[wolfmanjm]

M907 is current setting (not M903)

On Friday, October 7, 2016 at 10:43:47 AM UTC-7, wolfmanjm wrote:

[Mark Rehorst]

Two possibilities:

1) Midband resonance in the motors.  You didn't say how slowly you're trying to go, but motors have resonance and when you try to run at the resonant speed, it will skip steps.  As an experiment, try making a gcode file that moves a motor back and forth at increasing speeds from 10 mm/sec to 200 mm/sec in 5 mm/sec steps.  You'll find the resonance pretty quickly.

2)  I have a bad habit of not ejecting the uSD card from the connected computer before rebooting the Smoothieboard after tweaking the config file.  That has lead me into problems twice (I should have changed my habits after the first time, and I should have known better the second time!).  Along the way I discovered that if the smoothieboard is doing something crazy and nothing seems to fix it, one thing to try is reformatting the uSD card and copying fresh firmware and config files to it then rebooting (after ejecting the card from the computer!).  If reformatting the card doesn't fix the problem, trying a different brand of uSD card may help.

[Triffid Hunter]

Fwiw microstepping  goes a long way to mitigating resonant effects, you just won't see an effect as strong as if you use full or half stepping. For most applications resonance is effectively eliminated.

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[Mark Rehorst]

I get it, but someone should tell that to the 64:1 microstepped ball screw in the Y axis of my printer...