Sorry for the late response, I was travelling...
I bought this one: https://item.taobao.com/item.htm?id=531855133304&_u=1k1rlm99a40
A few questions:
You need an external 24V10A power supply, right?
It's included! It's really a crazy cheap package.
It comes with a GCode interpreter/controller, right?
Yes, comes with an Arduino-derived board with the 3 stepper motor controllers (and some extra I/O for optional spindle motor control / Z-mapping though you have to figure that out yourself).
How did you figure out how to put it together? Just watch a video, I guess?
Yes, the seller has put together a pretty decent video (on a Chinese video sharing site, so will be slow outside China) and they even sent me an English version of the assembly manual. Assembly wasn't too tricky but takes pretty much a whole day.
How are the items held down on the table? I guess something is fixed to the other side of the board - how does that work?
The table is made from "T-Slot" aluminium extrusion and you can use special screws to hold things down. There's many options, you can just hold things down at the edges with screws and washers. For PCBs, using double-sided sticky tape works well though it's a bit messy to clean up.
What software comes with it, if any?
The seller supplied a dubious copy of Artcam, which is a specialised software for generating G-code from 2D height map files. Fun to play with, you can make surprisingly pretty engravings in wood. Some other stuff too. I had to ask them for the link on the taobao chat. They also included some common open-source software for sending G-code etc.
Any idea of the total weight? (I'm thinking of bringing one back in my luggage ).
It was pretty heavy, I would guess close to 10kg. I don't have a suitable scale to hand unfortunately.
Any other tips, comments that might be useful?
The firmware used on the driver board is GRBL. The seller installed an older version but upgrading to the newest stable release worked no problem.
I've attached the assembly manual (with reduced image quality), I think that gives a good idea of what's involved in putting it together etc.
It is a cheap kit, and some of the component parts are of cheap quality (like the linear bearings), so I wouldn't expect it to last for years of heavy use. But it's a great start to experiment with CNC tools, and certainly "punches above its weight". I'm planning to modify mine to a glue dispensing robot as I have access to a larger CNC engraver now.
I used bCNC (
https://github.com/vlachoudis/bCNC) for sending g-code for PCB milling, which supports auto-levelling / z-mapping. You'll have to attach some wires with alligator clips to the controller PCB for this, one end attaches to the PCB and the other to the cutting tool so GRBL can sense when the tool touches the PCB. Flatcam for generating the g-code from gerbers. I covered the PCB in WD-40 to lubricate the cutting tool and cut down on dust. I used a nail-polishing pad to remove the burrs after milling.
Thanks!