If you have a broken string of LED Christmas tree lights, they're a great source of project LEDs. Usually they're 3.3-3.8V, 20mA bulbs.

Here's a simple (parametric) lighting U-mount for 6 LEDs that fits the thing-o-matic. No bolts are necessary, a built-in peg holds it to the z-platform.

• Print the mount
• Ream out the LED holes if necessary (a 3/16" drill bit works nicely) and fit the LEDs.
• Solder together the LEDs, resistors, wires.
• Apply some hot-glue and kapton to secure and insulate.

My LEDs pressure fit nicely into the mount holes. If not, apply some glue.

Using a 12V power connection, you can wire 3 LEDs in series with a resistor (for my LEDs, a 150 ohm resistor). The 2 set-of-3 are then wired to 12V and ground. I also put a switch in, so they don't have to be lit all the time.

After soldering (and testing!), cover the leads with some hot-glue and a layer or two of kapton. (My heater wires touch the mount, so the kapton helps a lot.)