Quote Originally Posted by Davek0974 View Post
What about the torque reaction from the cutting tool on the Z axis, there must be a twisting motion too there.

HSM Advisor gives tool cutting force and torque etc.
That is your main force that you need to allow for. If you know what torque the cutter needs, you can then calculate the forces required to move the X & Y axis against the cutter, which is the force you'll need for any FEA. However for the axis motion system, you need to add extra to cover any friction/stiction and any inherent losses in the motion system.
It's the Z axis where things get a bit more complicated, but your main force there is going to be while drilling or rotary broaching. Do neither of those, and you're biggest force is going to be from spiral milling cutters continually pulling/pushing the axis down/up.
I've got a couple spreadsheets somewhere for drilling/broaching forces, which I made to work things out for my lathe, however for drilling it won't calculate pull through force, which can potentially pull the Z-axis straight down into the table if the drill grabs as it breaks through the material.