Changing from .9 stepper to 1.8 stepper in K40

Machine: K40

Board: Cohestion 3d

Firmware: Latest Smootie

Problem/ Question: I have a stock stepper motor on my x axis that a wire pulled from the stepper motor board so I am looking to replace the motor. Problem is there is slim pickings when it comes to .9 degree stepper motors (at least from what i have searched for). Question is what is needed in the config file to make a 1.8 degree stepper motor function properly and if I do switch to a 1.8 is it as accurate as a .9? Or any idea where I can find a .9 degree stepper motor?


I don’t know the math as far as accuracy between .9 & 1.8 deg. steppers but in my experience with micro stepping either are plenty accurate for me in my hobby on both my cnc router and K40. You’d just need to adjust the steps and current for the new stepper motor if it were different than the model you have.

Here’s a .9° on Amazon I think would be ok for the K40.

the motor above - it’d be fine for X but the Y motor is a dual-shaft. I haven’t been able to find a dual-shaft 0.9° motor that would work in the K40.

In general a 1.8° motor will be just as accurate as a 0.9°. You can do one of two things to adjust the config for the difference: change the microstepping value (double it) or (not both) the steps per mm (cut it in half).

Ok, thanks to both of you. I think I may try the 1.8 Degree simply because there are more readily available. I just wanted to make sure I would not lose any function or acuracy.

One more question about the motors. The c3d board allows up to 1.2 amp to the motor, some motors say they are a 2 amp motor equaling 1 amp/ phase, and some say 2 amp and are 2 amp/ phase. does the board support 1.2 total amp equaling .6amp/phase or is it 1.2amp/phase? Sorry for all the questions but I don’t want to get the wrong one.

I think this one would be alright for the Y-axis if you were just looking to have a spare on hand.

IDK all the ins and outs of phase current on steppers but at a high level the amp rating on the motors is the max current the motor can handle before it starts welding itself together. The amount of current sent to the motor is controlled by the stepper driver and in our case will generally be set to .4 -.6 amps so it shouldn’t be a problem either way.

Microstepping is typically physically hardcoded on our boards (and you wouldn’t want to change it anyways), so doubling the steps per mm in the config file is the correct solution.

So I got the new motors today… I got a .9 and a 1.8, however the wire colors are different. I did get a wiring diagram though. What pin on the c3d board controls what? I can’t find a diagram for the c3d board. I don’t want to wire it up the wrong way.


Possibly nevermind, I found a picture on here of the back of the board that has the plug labeled… I will just add them in the screw posts.

config.txt (28.4 KB) ``
So what would I change in the config file if I changed to a 1.8 motor? I don’t see steps per mm for the X axis.

Alpha = X
Beta = Y
Gamma = Z

alpha_steps_per_mm                           157.575          # Steps per mm for alpha stepper
beta_steps_per_mm                            157.575          # Steps per mm for beta stepper
gamma_steps_per_mm                           157.575          # Steps per mm for gamma stepper
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Ok, that’s what I was thinking but wanted to know for sure.
Thank you very much for helping out.

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