I am in the design phase of a cnc foam cutter. I am wanting to use it to cut foam cores for model airplanes. My question is how large of stepper motors to use?
It depends on how heavy the parts of the CNC foam cutter weigh and how much force it takes to move it. If you are using drawer slides like in Dray's it hardly takes any force. Cutting cores is a slow process so you do not need to worry about high acceleration or high inches per minute. My first cutter used Vexta P266 steppers and handled it easily on a 12 volt power supply. I bet you could use 100oz just fine.