Motor stuck when setting steps per mm

jay_s_uk

@e4d sounds like you're trying to move your motors too fast for the steps per mm you need. try a slower move

kb58

@e4d It's the other way around; think of it in terms of distance rather than steps. You want it to move farther for each step, so think of it as mm per step that needs to be more. You can either figure it all out before hand mathematically, or try numbers and back out a correction, as you're doing.

You want to move 100mm but it only moved 30, so that means that each of those 30 steps needs to move 3.33 times further than it is now. So, that means that it needs less steps to move each mm. Try entering 400 / 3.33 = 120.12 and see what happens.

In addition, as mentioned, stepper motors do have a speed limitation. Regardless how many steps per mm it's configured as, if you try and turn it too fast, it will start missing steps and won't move as far as commanded.

engikeneer

@kb58 it's steps per mm, so if it's not moving far enough, he need to increase the M92 value

kb58

@engikeneer Sigh..., so it's back to a speed issue.

e4d

@jay_s_uk said in Motor stuck when setting steps per mm:

@e4d sounds like you're trying to move your motors too fast for the steps per mm you need. try a slower move

That solve my problem, thank you. I must be quite slow (max 2000 mm/mn), it may be due to the mechanical design

fcwilt

@e4d

Hi,

Post your config.g file using the </> tag.

Thanks.

Frederick

dc42

@e4d said in Motor stuck when setting steps per mm:

@jay_s_uk said in Motor stuck when setting steps per mm:

@e4d sounds like you're trying to move your motors too fast for the steps per mm you need. try a slower move

That solve my problem, thank you. I must be quite slow (max 2000 mm/mn), it may be due to the mechanical design

I suggest you use the motor EMF calculator to estimate the maximum speed.

Phaedrux

You can find the EMF calculator here: https://www.reprapfirmware.org/

And a steps per mm calculator here: https://docs.google.com/spreadsheets/d/1ts5fz73JQoQ4G0Z95nzfPDSS6HYEyczyZyccDZ5M6B4/edit#gid=0

Or here: https://blog.prusaprinters.org/calculator_3416/

e4d

I put the correct steps per mm in my config.g (1275) and I can only have really slow speed (max 700 mm/mn, 12 mm/s). I don't really understand why I can't go further. This is a really low speed.

I tried calculating with EMF Calculator, you can find my calculation here. I understand I may not be able to go to 150mm/s but 40-50mm/s should be doable. What am I missing here ?

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engikeneer

@e4d next two things are acceleration and friction.
Ball screws typically have quite high interia and so a whole bunch of the motors power is used just accelerating. Plus you also have the mass of the gantry/head to accelerate. What acceleration (and jerk/instantaneous speed changes) do you have in your config? Maybe try dropping them a bit.

Any friction in your system will also take power from your motors and limit your top speed. Make sure everything is well aligned and properly lubricated/greased. It should all rotate freely by hand when powered down.

Another thing to try is to reduce your motor current. That will increase your max speed the calculator gives! Also if you're running at 1500mA on a 1600mA motor, they may get quite hot which might make them less efficient (though I'm not so sure on that one)

Plan B is to get some 1.8deg motors as you'll be able to run them twice as fast for the same parameters

dc42

@engikeneer yes, 0.9deg motors make no sense when the steps/mm is so high.

e4d

@engikeneer Here's my config on this part :

; DRIVES CONFIG
M584 X0.0 Y0.1 Z0.2 A0.3 C0.4 E0.5                              ; set drive mapping

M92 X1275.00 Y1275.00 Z1275.00 A367 E420.00                     ; Set steps per mm assuming x16 microstepping
M350 X16 Y16 Z16 E16 I1                                         ; configure microstepping with interpolation

M566 X400.00 Y400.00 Z8.00 E2.00                                ; set maximum instantaneous speed changes (mm/min)
M203 X35000.00 Y35000.00 Z5000.00 A5000.00 C5000.00 E1200.00    ; set maximum speeds (mm/min)
M201 X6000.00 Y6000.00 Z1600.00 A2000 C2000 E250.00             ; set accelerations (mm/s^2)

M906 X1600 Y1500 Z1500 A600 C600 E800 I30                       ; set motor currents (mA) and motor idle factor in per cent
M906 E1000 I10                               					; Idle extruder motors to 10%
M84 S30                                                         ; Set idle timeout

I can rotate the system when powered down. I will look into 1.8 deg motors.

engikeneer

@e4d if you want to stick with these motors, definitely reduce acceleration (M201). Try 10x less for starters.
Your instantaneous speed change (M566) is reasonable, but I'd also try dropping that too.