It's time to start thinking about motor power and leadscrew pitches for my machine.

What's the best way to approach this?
I've seen people talk about target speeds, target accelerations (0.5g? 1g?), gantry weights, cutting forces, motor curves, etc.

I should say that I'll be using trapezoidal leadscrew, which will have a much lower efficiency than ballscrews. Before now I've been thinking about 3Nm motors, but perhaps I don't need all that power.

Practically speaking, having never done this before, where is the best place to start?
Acceleration seems more important than top speed for the relatively compact routing I'm going to do (many direction changes), but what should I aim at? What do you lot use?

Speed is much easier - I'd ideally like to achieve a jog speed of 120mm/s (~280 IPM), which is 900rpm on an 8mm pitch leadscrew. Can steppers do that speed? I'm thinking cutting speed will be less closely linked to motor power, more to router power, chip load, and machine rigidity.

Cutting force seems important too, but what figures should I use? Or should I worry about it less and just bolt some stuff together?

Kip, Smiler, Lee,
What do you think? How do you do it? :question: