Thanks for the feedback guys.

I'm currently thinking that realistically we might well end up with a 60cmx40cm size. Or even 30cmx40cm

Any ideas for designs/plans for a machine this size that has enough rigidity to perform OK when going through aluminium? Building ourselves would be tempting, but realistically it's just not going to happen unless we have "painting by numbers" good instructions.

The KRM machine Building the KRMx01 CNC looks like it might have this combination of rigidity and detailed instructions. Any other options I should be weighing up?

One possibility I'm seriously considering is the 6040 machines from Yoocnc 3020 3040 6040 series - carving-cnc.com. They're Chinese and used to have awful electronics but now better. You can buy the main body alone which is a tempting option.

A lot of people on cnczone.com seem to think the mechanics on these is good, and that you'd be hard put to get the materials alone for less than what they cost assembled. What's your take on the value-for-money of the frames of these machines?

I get the impression they can mill aluminium, just slowly.

Jonathan