...but pretty close. The answer to the question last time was "steel". Even though some parts are still missing, i couldn't help but toss together a mockup of what the Moco head will look like when it's done, using scrap parts. So, what you see in the image isn't the real deal, but the overall shape is more or less correct, sans wheels and some other bits. The steel parts are 0.9 mm thick (the only option available at Ponoko), which isn't much. I was a bit worried about the rigidness, or rather the potential lack of it, but after bolting the parts together the resulting assembly feels rather solid.
I'm simultaneously working on another approach to the same thing: instead of 0.9 mm steel, it will be made of 5 mm thick plastic sheets. When i get that stuff, i'll compare the two for rigidness, weight, durability, look etc. properties. I hope one of these two approaches will work fine, but if not, the next thing i'll try will be aluminium, in 3 or 5 mm thickness. Ponoko can't supply that, but there's yet one more online manufacturer that does, emachineshop.com. I haven't ordered anything from there yet, but i did already download their CAD software and try it out. Works fine.
As a side note, i also made some progress with the DIY CNC / 3D printer. It will be built mainly from the standard Halsugrip aluminum profiles - actually that's closer to their original purpose in a way. I did quite a few tests for track / dolly alternatives back in the day, and some parts i gathered for that purpose will find a good use in this contraption. My dolly protos use skate wheels currently, but one option was to use slider bits instead. They are machined slippery plastic parts that run along the grooves of the aluminum profiles. The moves are very precise, but they required a bit too much force to be used in a dolly in my opinion, and they made a clearly audible swooshing sound which is a no no for any shoot with on location audio. But for the linear move elements of the CNC / 3D printer they will work nicely, i think. The force to overcome friction should be a non issue, my design uses 10 mm threaded rods to drive the XYZ stages, so each full rotation of the motor is translated to only 1.5 mm of linear motion. With that kind of transmission, there's plenty of force with me i hope.