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Author Topic: Loud and slow steppers
lukasw
Newbie
Posts: 2
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Post Loud and slow steppers
on: December 23, 2016, 10:49
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Hi Everyone!

I finished putting together a brand-new Polargraph a few days ago, so first of all: Thank you for sharing the project, for the great documentation and resources, also in the forums here. I would love to share some drawing with you, but I am experiencing some troubles with my steppers. While they track across the drawing surface quite accurately, they are slow, get sprocket-melting hot and produce constant, high-frequency sounds that are so irritating that I can not run it longer than 15 minutes without being afraid of getting a tinnitus.

The specs of my machine:

  • Uno R3/AFMSv2.3
  • Steppers: Emis E547-52500 0.25 Nm 0.6 A (200 steps/1.8°)
  • Variable power supply with 1500mA usually set to 7.5V
  • most recent controller+firmware release from GitHub (March, 2016)

While searching the forum, there does not seem to be much love for the AFMSv2 but most of those posts are a bit old, so are there Polargraphs out there successfully running this shield now or is it just hopeless? Could it be the motors drawing to much power? I feel like the sounds have lower volume when the power supply is turned down to 5V..
Concerning the speed: The gondola takes more than a minute to move across an A3 page, which I guess is not right judging by various videos around here. The acceleration and max. speed settings in the controller do not alter the movement behaviour either, I'm afraid. Are these issues down to the AFMSv2 or is there a way to solve them without replacing it?

I am very thankful for your help and suggestions!
Festive holidays,
lukas

(edit: added more detailed motor specs)
lukasw
Newbie
Posts: 2
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Post Re: Loud and slow steppers
on: December 23, 2016, 12:56
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Quote from sandy on July 30, 2016, 22:08
The quick solution is to turn off microstepping, modify the line of code at https://github.com/euphy/polargraph_server_a1/blob/master/configuration.ino#L31 to be

const int stepType = INTERLEAVE;

And set up your spec as

stepsPerRev = 400;
stepMultiplier = 1;

in your controller default.properties.txt

Found this solution in another thread.. did not search for 'squealing' before, sorry. That got rid of the loud beeps, squeals and the speed limit, my ears (and probably my neighbors) are very thankful. But at the same time it introduced quite the rattle from the stepper motors and completely threw off the tracking. I think I can get the calibration dialed in again, but I am still not happy with the sound level. I will see what I can do, but still appreciate your ideas and suggestions very much!
sandy
Administrator
Posts: 1317
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sandy
Post Re: Loud and slow steppers
on: December 23, 2016, 17:28
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Glad you found some progress, and thank you for your support! I've never been a fan of the AFMSv2, but the simple reason is that I've never really understood how to tune it to get around this kind of issue.
It's actually no different to the v1 shield, because on that too, the only thing that could really be tuned was the supply voltage - and the motor size I guess. I've always used the same motors between the two drivers, probably similar to yours 0.6A steppers. I've never had great results, and I wonder if it's just a case of using the wrong spec of motor - the ones that Adafruit sell draw 350mA, perhaps they are a better natural match for the shield, and work at a more sensible voltage.

So if I was going to try and get this board running with Polargraph (or any other project), I'd try with a motor that draws much less current, and still use a variable voltage power supply.

The "cogging" that you get with the interleaved style is the reason I made microstepping the default style with this board. I'm sure it's possible to use the board well and get a good quality run from it, but I just haven't done the experimentation to do it.

The squealing is pretty awful. If the positioning is working ok, but the speed is low, then it's likely it's just the speed that's low, but it up to a couple of thousand and see what happens.

Good luck!

sn
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