I've always been interested in laser cutters but have never had the need for one so could never justify the big costs of the units.
These Chinese ones make it just doable for me as a hobbyist but I'm torn whether I should make my own or go with a 40W Chinese and try and mod it ...
My biggest problem with the 40W cheap ones is the size .
I would like A3 bed size rather than A4 so my first question is has anyone had any experience of extending one of the Chinese ones ? I know it would have to be taken out of the enclosure but basically all the bits would be there already set up. Could it be just changing the linear rails to longer ones ?

My second question is about power. The 40W ones seem to be on the bay of e for about £370 and at present this would be my price limit... However I want to be able to cut 6mm Ply and I know that is on the limits (depending on the brand of ply ) for a 40w machine. It should be able to cut something like the 6mm lit laser ply from HPC no problem but that stuff is pretty expensive. So If I went for a 40W could I at some point in the future add another 40W tube to it? Thus have a dual tube unit ?
Also reading about the dual tube units it seems that have their own mirrors and lens so that two objects can be cut at the same time or one does engraving whilst the other does cutting. What I would like to do is focus both lasers on the same spot so have a 40w for most of my work with redundancy if the tube pops but the ability to ramp up to 80W if need be and the bigger set up only cost me the price of a 40w tube and PSU.
Am I way off beam here fellas ?