I see lots of posts asking how large a stepper or servo motor is required for a given size machine. I found this free program which takes all the parameters for a machine, and calculates the size of stepper or servo needed. It is intended as a tool for selling Parker motors, but it does show a graph of the required torque, so could be used for general motor selection. It takes into consideration the inertia of all the components. You put in all the parameters for your machine(leadscrew size and type, machine weights etc), and the desired acceleration and speed, and it outputs a graph of the torque required.
http://www.compumotor.com/scripts/su...s.asp#SIZINGCD
Look for "sizing and selection tools". You do have to register to download it, but registration is free.
Jeff