Also very easy to convert to a 5th axis machine (;-) I know you want one (;-)

Like i mentioned earlier if you want a great do everything machine build a fixed gantry mill . It can do everything to a point.

(;-) TP

So that would be fixed gantry and moving bed?

Assume bed moves in 1 axis and the other axis is carried on the fixed gantry?

Also very easy to convert to a 5th axis machine (;-) I know you want one (;-)

\

5?

having enough getting to grips with three

4 axis is fun. 5 axis is expensive.

Like i mentioned earlier if you want a great do everything machine build a fixed gantry mill . It can do everything to a point.

(;-) TP

Thinking a little more, a fixed gantry/moving bed puts the motion for the bed in the dirt/coolant zone, ok on a big machine but probably dodgy on a small unit??

I was looking at an X/Y gantry with the rails mounted way up under the gantry so no side support columns on the gantry.

Dredging through the suppliers on Aliexpress, it looks like I'll get 3 sets of 600mm 1610 screws/nuts/supports and some 1m long HiWin's and just build the machine around the motion, it's far cheaper than getting custom lengths and easier than machining the ends of the ballscrews myself.

Both dependant on the overall size of the machine but…
A moving gantry machine can have a much smaller footprint.
A fixed gantry machine can have a lot less mass on the Y axis.

There are many other for’s and against’s for each design so it perhaps all comes down to personal preference. 

Tweakie.

Yeah, got that, space is very important so will be leaning towards moving gantry.

Thoughts during tea break....

My want is for a general purpose machine - wood, alloy, plastic, engraving, carving, milling, working envelope maybe 400mm x 500mm.

Now, I see plenty of builds with 100's of kg of steel in them, but for such small cutters, is it really needed or is it "just the norm" ?

Picture if you will, no box-section, use maybe 15mm x 150mm or 20mm x 150mm aluminium to make a shoe-box structure - 4 sides and a base (base can be thinner i think).

Mount 15mm HiWin rails to the tops of the long sides, 2 carriages on each side. Mount 1610 ballscrew on outer side of longer sides.

Make gantry base to span the opening, deep enough to take two carriages suitably far apart, drop plates down from ends to fix ballscrew nuts to - it would be an inverted U shape.

Build gantry as required from base up to hold Y axis and Z axis and brace down to base of gantry at rear.

Basically just build the whole thing from a slab of alu and screw it together suitably.

Probably just hogwash, but can you really get that much counterforce etc from such a small tool???



As i say, just thoughts, no bank balances were damaged during this process

Scrub all of that, bad idea

Been chatting to a builder that sells these things and got enough help to get going now.

Motion control...

Stick with parallel or go with my feeling of using something like a UC100 motion controller???