Quote Originally Posted by msacnc View Post
i do not determine certain speed but the faster choice is better for me

rack inf:
20 mm wide and 20 mm thick 1500 mm long Module 1.5 Pressure Angle:20°

commonly the machine is used for woodworking

I plan to reduce the gantry weight using one steel box 100*100*3 welded to two pieces of 150*100*3 gantry side



"this probably won't be accurate enough for machining aluminum" Why?
mod1.5 = 1.5mm dia per tooth so with 28 tooth pinion 1 rev = 28*1.5*pi= 131mm and direct drive gives 131/200 = 0.66mm resolution per full step

for reasonable speed on a rig of that size 4000mm/min would be a good minimum with 400mm/s^2 acceleration
so (to make math easier) 3930mm/min = 30rpm of pinion so gearing 2:1 = 60rpm, 3:1=90rpm, 5:1=150rpm with resolution of .33mm, .22mm and .132mm/step respectively

Assuming a 80kg gantry and ignoring minimal friction in linear slides, the force needed to get 400mm/s^2 (0.4ms^2) acceleration is F =ma = 80 * 0.4 = 32N, which gives the torque on a 28tooth, M1.5 gear is (radius =62.5mm) = 32*.0625 = 2Nm, geared 2:1 =4Nm at motor, 3:1=6Nm, 5:1=10Nm. This ignores losses so add 10-15% for safety.