There was a episode of Eureka last night about 3D bio printing which the intended result was to be a living breathing human. Although quite a leap from where we are now, I believe someday it would be possible.
It depends on the length of the arms and the configuration of the robot. A delta will max out in a triangle and a quattro in a square. The really cool thing is that the configuration allows you to tilt the print head too, allowing for 4 axis machining. Not sure if this would be handy for additive CNC work but I'd be willing to experiment!