Hey Rob, rather than edit agian I though I would repost. Your servo needs will be dictated by several things.
1. Linear rail design (friction)
2. Weight
3. Desired feed and rapid speeds
I can tell you that you want that sucker moving when it comes time for a tool change. 120" is a long travel even at 354 ipm which is my machine's max rapid. I will say that I am using steppers rather than servo's and could up that to around 500 imp with good servos.
Are you going to build your a/b axis or purchase? If you purchase, the $12,000 will get you about half way to the price of a new Colombo a/b head.
Spend plenty of time designing before you spend too much money and make sure you have good quotes on the machining. Don't ask me how I know.
Mike
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