1HCL and "microstepping"

[ezr.design]

Hi,
I'm building a big (100cm print diameter, 120cm-ish print height) Delta printer. I want to use 1HCL boards with magnetic encoders on the XYZ tower motors.
When choosing pulley size what microstepping should I keep in mind? With normal 1.8° motors, 20 tooth pulley + 1/16 microstepping gives 80 steps per mm. And 1/16 is usually the highest microstepping a motor can do before it starts loosing torque and skipping steps.
With 1HCL and a 14bit magnetic encoder the real achievable microstepping is more? How much more? 32? 64? 128? Can I use bigger pulleys without sacrificing resolution?

[droftarts]

@ezr-design See https://docs.duet3d.com/Duet3D_hardware/Duet_3_family/Duet_3_Expansion_1HCL#microstepping

So it depends on the firmware you are going to run, and the resolution you can achieve depends on the encoder. This should inform your choice of pulley size.

Ian

[ezr.design]

@droftarts so for the magnetic encoder that goes with the 1HCL it's 14bit = 16384 positions per 1 full revolution? And each position of the encoder can be reached? With 100% repeatability? Without loss of torque?
And how does the step pulse frequency influences all this? With high microstepping you soon reach very high frequencies on fast travel moves.

[o_lampe]

@ezr-design
IIRC the strategy to deal with lost steps is to compensate during the next move.
IMHO the purpose of closed loop steppers is not to increase accuracy within microstepping range, but handle lost steps and layer shifts.

I wouldn't be surprised if the 1HCL cuts off two least significant bits to reduce AD-conversion noise. So the real resolution would be 4096/turn. Not much more then the regular 3200 microsteps/turn @ 1/16.