Okay, if you mean you don't understand what I'm trying to build then it is this:
A device which will, at the pull of a single lever, cast obsidian on any number and distribution of tiles in a 20x20 tile section of the ground below it, based on the input from a bunch of levers placed elsewhere, and reset itself. The area below it will be deep enough that multiple layers can be cast on top of eachother, making it possible to 'print' many different obsidian structures.
With the next step being one which can cast multiple layers at the pull of a single lever, though I think that's going to be far beyond not worth the effort. If you mean that you don't understand what the machinery described in my last post is doing, then here is an explanation of how the printer works, with extremely crude diagrams:
Somewhere in the fortress are a bunch of levers arranged in a grid. Elsewhere in the fortress, below a rapidly flowing and infinite source of water (in this case an aquifer) are a set of chambers with the following structure:
# = wall, c = hatch, ^ = pressure plate, X = floodgate, = = bridge, ~ = water
###
#c#
#^#
#X#
===
~~~
The bridges are normally raised, and the hatches, which lead to a drain down into the caverns or hell, whichever is appropriate, normally closed. The floodgate is linked to one of the levers, and the pressure plate is linked to a floodgate which is sitting directly beneath the intake for a pump. The area around the pump looks like this, with the pump's intake being to the left, from the side:
~ = magma, %% = pump, * = gear assembly
## #*#
## # %%
##~=X##
#~~#*#
#~# %%
#~=X##
The bridges are normally raised, the floodgates closed, and the mechanisms unpowered somehow. As you can see, the pump-structure can stack vertically in a staggered manner, and can also be continued horizontally, resulting in rows of pumps which can pass magma onto any square in a rectangular area. The levers mentioned above are linked in such a way as to correspond with the place on the floor below which the corresponding pump will dump magma on.
The minecart setup, as pictured below, has the first pressure plate on the track linked to all the bridges in front of the water-filled area, allowing water to activate the pressure plates and lower the floodgates in front of the corresponding pumps before the bridges raise again, locking the water inside. It is also linked to a floodgate much farther down which lets water into the area the pumps hang over, up to a level of your choosing (based on what level of the construction you are printing. The next pressure plate causes the bridges separating the magma from the newly opened pump intakes to lower, allowing the magma some time to flow in before the bridges close again, preventing excess magma from being pumped. The third pressure plate turns on the pumps, which dump the magma onto the water (which by now has hopefully filled the chamber below) and forming obsidian. The last pressure plate opens the hatches, releasing the pressure plates that had been keeping the floodgates near the pumps lowered, and also draining the water from the chamber below.
The technical drawbacks of this design are that I'm still not sure if there will be enough time for magma to flow into the chambers before the bridges close, and won't be until I actually test it (and although it's not that difficult to fiddle with that part of the mechanism a bit, it is extremely difficult to clear the magma from the pumps), it requires an enormous amount of power to operate (about 7000 power, though this is largely my fault for making it so big) and there are some 3D things which must be printed in stages since liquid does not fall at a steady rate and thus you can't count on some supporting structures to be cast before the things they need to support, in the case where things are being supported from their sides. On the plus side, the mechanics are simple, the device is entirely self contained and can be modified to be of any given size and shape. It is also relatively cheap to build so long as you have access to sand, which I do.
As far as updates go, I'm currently distracted by besieging goblins wiping out my copper-clad army to the point where I've decided to just cheat myself some Adamantine, but I'm also just about done setting up the floodgates, so the next thing to do is to build the casting chamber.