Unusal Z-axis arrangement?

[Voicecoil]

Whilst out tramping the mountains the other afternoon and pondering the best way to do a z-axis, I had a weird idea . Instead of the usual way of having a high gantry and dangling the spindle down from this on the z-axis mechanism, why not mount the spindle straight to the X carriage (I'm viewing the machine normal to the gantry when talking of X and Y) and move the whole gantry up and down? Yes, it will require more bits but perhaps could yield more rigidity at the lower extremes of Z (tool close to the bed - which is probably where it'll be used most of the time). Any "racking" problems should be avoidable using closed-loop Z motors I think.
Does anyone know of any machines that use this approach?

[routercnc]

There is a blue machine in Youtube like that made by a German builder (?)
Jazzcnc noticed it and posted comments on it in this forum. Yes it could be made to work. Would be worth sketching it out to see where the challenges were in construction from a practical point of view.

[Greeny]

here's a similar thread
http://www.mycncuk.com/threads/9147-...-gantry-design

and a video showing the machine mentioned going through the motions (there are a few other videos from the same bloke )
https://www.youtube.com/watch?v=9y7Y2abT-3M

Cheers

[Voicecoil]

Thanks for the links; so it can be made to work - that's one very industrial looking machine! If I was making a machine for cutting metal I'd be tempted to go that way, albeit with the Z slideway arrangement done slightly diffeently. I won't be doing it myself on the thing I'm designing at the mo. since having a conventional dangly Z-axis is actually of particular use to me when carving out large waveguides, since you can get the spindle down inside the workpiece to some extent.