Z axis must be fast. ideally I want 50mS for 20mm travel.
12.5 mS to full velocity
maybe use a big NEMA14 stepper with rotor inertia 18g/cm2
Total lift weight – 16g (carriage) +20g( stepper mtging plate) + 120g (NEMA11 hollow stepper) + juki adaptor and nozzle (36g) + air fittings (20g) .
call it 220g
Driving sprocket size : 24 teeth of GT2
I plug the numbers into my spreadsheet-
Stepper pull out torque , lifting- 0.093Nm
Rotational acceleration = 5235 rad/sec2
Nozzle change – requires a >700g push down… = ~ 7N on the belt or 0.052Nm on the motor shaft.
Choose NEMA14 (35mm square) with 2x lifting = 2 * 0.093 = 0.186Nm…
Not included in calcs- rotational inertia of pulleys (not much) , and belt weight (not much) , frictional loads of the MGN9 linear guideway (not much).
glenenglish 