I am also looking at designing a TMC2208 driver board mod for the Cetus3D MkII and wanted to know specs for each of the steppers including the extruder.
I reached out to “Moon’s Steppers” with a picture of their stepper on the MkII and the response I received was underwhelming.
I’m chasing coil specs, current limits and steps / revolution / step angle.
This is the closest stepper motor what I found on Moons webpage:
Cetus mainbord stepper drivers are set to 400mA and 32 microstep…
The specs are not disclosed, only the engineering team knows the exact numbers. Usually motor nema17 motors for 3d printers should work.
I don’t want to replace the steppers, I want the specs so that I can properly design and build a TMC2208 replacement board for each axis. Moons told me to contact TierTime for the specs.
Thanks - do you know if that is the same for the extruder stepper ?
Yes, the mainboard use the same driver chip and same current settings for all stepper motors.
Are the steppers definately 32 microstep ? I am trying to apply the calculations to work out steps/mm
Steppers don’t care about microstepping, only stepper driver and slicer does. But yes, you have to match the microstepping of the original drivers to replace them with TMC.
Biggest “problem” with the motors is the extremely high inductance, at least on the UP! series this is 30mH, and that makes a bad combination with trinamic unless you can crank up the voltage a little.
If you can supply custom g-code and measure the step/dir pulses you can work out the microstepping and steps/mm that way. Or if your Cetus has the “dumb” drivers configured by microstepping pins you can just look at the datasheet and determine which pins are tied high/low to find the microstepping that way instead.
I realise this but the mathematically work out steps/mm I need to know the microsteps
You could derive that from one full rotation and the full step angle.
(i.e. send random g-code til you observe 1 rotation of motor, then count step pulses. but looking at datasheet and pcb is probably easier)
Great! Thanks! I’ll have a look at my board tonight.
Curious to see what your ideas on intercepting the step/dir/en signals are? Stackable headers between the CPU board and Main board, soldering to pins or headers?
I contemplated doing something similar but I chose to replace the all the electronics to free up the choice of slicer as well as silent electronics.
Yes, it 32 microstep from the motherboard bechmarking.
Did you get to try this? Does the 2208 support 32 microsteps, or will you need to go with 2224 instead?
TMC2208 can support 32 microstep but you need to program it by serial… like here sergey made it:
https://forum.tiertime.com/t/tmc2208-on-cetus3d-mk3
Further reading seems to indicate you skip the tiny85 if you connect the drivers to a usb-ttl serial port and use https://learn.watterott.com/silentstepstick/configurator/ to set OTP bits
(although a $1 tiny85 doesn’t really break the budget on such a project)
You can set the StealthChop/SpreadCycle modes by OTP memory write, but the microstep resolution not: TMC2208 Datasheet 5.4.1 CHOPCONF – Chopper Configuration: MRES bits
unfortunately…
So thats why I plan to use the TMC2224 drivers
I use a TinyFab CPU on my mk2. In the Smoothieware (firmware used on TinyFab) we need to define the steps per mm. These are the working settings on mine. Note that I had to measure only extruder by measuring the extruded filament. But I have printed many engineering samples as well as many parts for cetus itself (e.g. this Y end stop,3D touch bed sensor holder or this Dual duct for Cetus) on mine, and always get exact measurements. So I can confirm that Extruder motor is different from xyz motors.
# Arm solution configuration : Cartesian robot. Translates mm positions into stepper positions
alpha_steps_per_mm 160 # Steps per mm for x stepper
beta_steps_per_mm 160 # Steps per mm for y stepper
gamma_steps_per_mm 160 # Steps per mm for z stepper
extruder.hotend.steps_per_mm 245
I also need specs for the MkII stepper motors, i just bought a nema 17 motor for my 3d printer.
https://www.oyostepper.com/goods-64-Nema-17-Stepper-Motor-Bipolar-09-deg-46Ncm-651ozin-2A-28V-42x42x48mm-4-Wires.html