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Stepper motor selection

Posted by JustSumGuy 
Stepper motor selection
August 22, 2017 09:06AM
Hello, I am working on a printer build and trying to select the stepper motors for the build. Looking for NEMA17 0.9 deg 400/rev 45-50N.cm holding torque.

I am looking at 42BYGHM809 but I want to have a removable plug so the wires can be swapped rather than have them fixed into the motor.

This is for future maintenance, I don't want to have to replace a whole stepper when I can just replace the cable.

I cannot find a 0.9 degree stepper with a removable lead!!

Is there some reason for this that anyone might know of???


Also another question, the stepper motors voltage range around most appear around 3.05v I plan a 24v system running from DRV8825 drivers.
with the range of voltage tolerance I am wondering what I should be looking for....

Thanx

Edited 2 time(s). Last edit at 08/22/2017 09:11AM by JustSumGuy.
Re: Stepper motor selection
August 22, 2017 09:14AM
It's common to use motors with about 3V DC rating with both 12V and 24V power supplies. The stepper drivers are constant current so they don't actually receive more than 3VDC. The higher voltage supply to the drivers is needed to achieve high speeds, because the inductance and back emf of the motor have to be overcome.

DRV8825 drivers have known problems with some types of motor, especially with higher supply voltages. The symptom is either missed steps or a loud whining noise, depending on how the decay mode is configured.

Edited 1 time(s). Last edit at 08/22/2017 09:15AM by dc42.

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Re: Stepper motor selection
August 22, 2017 09:30AM
Quote
dc42
It's common to use motors with about 3V DC rating with both 12V and 24V power supplies. The stepper drivers are constant current so they don't actually receive more than 3VDC. The higher voltage supply to the drivers is needed to achieve high speeds, because the inductance and back emf of the motor have to be overcome.

DRV8825 drivers have known problems with some types of motor, especially with higher supply voltages. The symptom is either missed steps or a loud whining noise, depending on how the decay mode is configured.

Thanx for the reply dc42.

I thought that was the other way around? the 8825 having problems at 12v sometimes and ok at 24v.....

My current small box printer is 12v on A4988 step sticks. when I try to use a 0.2 tip I cant get down to .05 layers like I feel I should. I see some skipped steps and its very crude printing. I attributed this to the electronics not being able to perform refined enough moves with high enough holding torque.

So I thought going to the 8825 would help there, then I heard about problems at 12v (I may be remembering that wrong...) so I decided to go 24v
Then I decided 0.9 deg steppers would be the last part of the puzzle to make very fine movements clean.

Am I off base?
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