[microcarve]

The main thing a moving table design has against it is
the extra space it requires for the same cutting area.

Other than that, it's a stronger and easier to build
machine. As well as maintain.


Picture #1...

There are few, if any, moving gantry machines that'll be stronger
than that. There will be no twisting/skewing/racking of a moving
gantry...because it doesn't move.

The table rides on 4 widely spaced bearings, so it won't rack
either.

The nut can be supported to prevent whip at each end of the
table.

A finer pitched screw choice will give it all the mechanical
advantage it can use, though only slightly slower cutting
speeds, but still well within a range it can cut in any
practical manner anyway.

Well, that machine's a big industrial beast....


Picture #2...

Looking at that machine and asking why it's made like it is
points to a need for extreme rigidity. It must do some very
highly precise work to need that kind of strength.

It's pretty easy to copy the basic design of it for hobby
purposes and still get many of the advantages such a machine
can give.

Mine is just a big MDF version. The table is a separate element
in the design that can very easily be slightly adjusted to as
near perfect square with the gantry as possible.

The bridge can be built in such a way as to make raising or
lowering it a simple thing to do for doing something like
computer case or large electrical box work where project height
can matter. Just a few bolts will easily lower or raise the bridge.


Picture #3...

A prototype that proves it works Great. It's a lot more rigid
than my larger moving gantry machine. Easier to maintain...A
moving gantry can be a PITA to get square and adjusted to
prevent possiblity of skewing. This isn't. It's cheap & easy...


But it really all depends #1 and Foremost on what you need from
the machine. It can be useful to think of these type machines
as "special purpose" machines. There's a "right design" for any
particular type of project.

Mine will cut about 24 x 15 x whatever depth I want to adjust
the bridge to....so it's *Ideally* suited for something like
a guitar body....where things need to proceed as well as possible
on an expensive chunk of Nice wood....
(Do Not want any chance of things going wrong halfway through
a job like that! Things going wrong are minimal with a simpler
design)

Sure it takes a bit more space for the moving table/fixed bridge
design, but again, it depends highly on what the machine needs
to do. Large signs may very well need a moving gantry...just for
the large-ness of the project alone.

I don't build a machine any larger than it needs to be for any
type of work it'll do. The smaller the machine can be, the easier
it can be to build and maintain. The simpler it is, the less
maintaining needs to be done...

My $0.02


John