Hi All - To discuss machine configurations a bit. 1) There is no ideal config. Each has a purpose and all machine manufacturers make several types of configs for different applications. If there was an ideal config we would have figured it out by now. We have been making CNC and manual machines for a very long time and evolution has not narrowed the configs it has broadened them. 2) The only "recent" thing that has changed mills and lathes is linear guides. Guides have opened up possibilities that did not exist with gibs and ways. Many different configs are possible with guides. Applications & production have driven development of VMC's and HMC.s in various ways 3) future machines will be influenced by 3D printed parts (lighter stiffer damper in steel and titanium) and composites (lighter stiffer damper, more stable over time).
I was convinced that a lifting gantry was to be my next build but this study has pushed me back to the moving gantry design. So Millis brief is a small benchtop or stand CNC Mill. With maximum stiffness which is not specified at the moment but all decisions have been made via the stiffest studied solution. Aiming at 20N/um which is quite a high target for a small mill. We shall see how that goes as the project develops... Peter