Here’s a brief synopsis of a few things.
General printer recommendations:
Extrusion width range (absolute min to max): 60% to 200% of the nozzle width (generous)
Layer height range: 25% to 75% of the nozzle width.
Origin of the “magic number” and where 0.04mm comes from:
Given: Driver using x16 microstepping, 4-start 2mm-pitch, 8mm lead screw, 1.8 degrees of rotation per full step of the stepper motor.
- 360 degrees in a circle / 1.8 degrees/full step = 200 full steps per rotation, x16 = 3,200 microsteps per rotation
- Steps per mm = 3200microsteps/8mm = 400microsteps/mm
- Minimum distance for a full step = 16(microsteps/full step) / 400(microsteps/mm) = 0.04mm/full step
The reason 0.04mm so called “magic number” is important is because when stepper drivers employ microstepping each microstep will have less available torque than a given full step. So there will be 15 weak steps followed by a strong full step (greatly oversimplified, the torque curve is sinusoidal).
The logical conclusion of this train of thought is that using layer heights of multiples of the magic number will sidestep the torque reductions of microstepping by ensuring at least a full step has occured to generate the full commanded motion.
I’m not sure this is all strictly necessary on the snapmaker. I have measured a minimum travel consistently around 0.015mm. There’s a number of possible explanations, but I believe it’s because of the large mechanical advantage of this particular lead screw system, combined with the particular driver being used. This may not be true on the new TMC drivers.
But the minimum motion is not 1/400mm. 6-ish (micro)steps seems to be around the minimum.