DIY CNC Milling Machine From Scratch

[Jonathan]

Okay after managing to get on the computer i have made sure my plates are made of steel, and from what i can find the 2.2kw spindle is around 5.15kgs then the z axis is around 45kgs.

Just realised I forgot to reply to you about this. Using the script I posted here, the difference in torque required with and without the gas strut is around 20-30% and the absolute value is low enough for a 3Nm stepper motor to work well. I'm guessing a bit with some of the parameters, but suppose you put a 20T pulley on the motor and 30T on the ballscrew, the required torque (taking into account inertia of ballscrew, pulleys, carraige and motor, plus friction of bearings, ballnut etc) for 3m/s^2 acceleration is 0.87Nm without the gas strut which is well within the rating of a 3Nm motor below the corner speed. That means you'd easily get about 3.3m/min feedrate. The torque requirement for the same acceleration with 30:30T gearing is almost twice as much (1.67Nm), but if you use 20:20T it's 1.1Nm. The belt stiffness goes down with smaller pulleys, but it's still higher than the ballscrew torsional stiffness so not too big a concern ...

I'd recommend 20:30T pulleys on Z, as around 3m/min should be plenty for this size machine and you get higher resolution compared to 1:1.