Mechanics
Ok, so I wanted to make a 3d printer that could print with food dye in jelly, and I wanted to make one quickly, so I would probably have to use components I already have at home. The most common way to do a 3d-printer is to have some kind of x-, y- and z-gantry that moves either the printing head or the surface around. These gantries usually are based around linear actuators or steppers with belts, but essentially, any way to get a precise linear movement will do. You also want the gantries to have a reach that's as big as the biggest object you're planning to print. For my jello-shot-printer, that could be quite small: the reach doesn't have to be bigger than a shot glass.
So, where could I find a linearily moving thing that didn't need to have a huge reach? I looked through my things and found my stack of old cdrom and dvd drives:
These things need linear movement to position the laser, so opening them up should yield some usable parts.
In the end, the loot wasn't as big as I expected: it seems that a lot of cheaper
CDROM drives position their laser by using a standard, imprecise DC-motor and using
the laser tracking as feedback. That's a nice idea, but because I don't have that
precise feedback in my jello printer, these types of motor aren't that usable.
Luckily, some drives still had the more expensive but more precise stepper motor to
position the laser; because they give a precise movement with every step of the
motor, these were perfectly usable.
I decided to mount everything on a solid bit of wood. I started with the first of
my scavenged gantries, which would move the shotglass in the X-direction:
Now, how to get fluid out of the needle? The most obvious way was to do it the same
way as when I did it by hand: just push the plunger of a syringe. The carriage,
meant to only move around a laser, obviously wouldn't be able to support all that,
so I took a small bit of fine tubing and used that to connect the syringe and the
needle. To press the plunger in, I also recycled one of the parts of the cdrom drives:
the tray eject bit. It got cut down to the bare minimum: the motor assembly and a bit
of tray large enough for the syringe to sit on. As you can see from the splatter damage,
it's pretty important to make sure the syringe is well attached to the tubing...
With the mechanics out of the way, all I needed was something to drive everything.