You've been looking for the "killer application" to justify purchasing a 3D printer? Think about lighting fixtures, the unique ones that can't be found in "big box" stores. A 12 volt LED picture light and invisible wire (metal tape) will cost over $800. A lamp, socket, tape, transformer and plastic to make your own costs less than $30., which leaves $770. to purchase a printer. Install a few of these lights and, well . . .
First things first. Whether you "do it yourself" or "purchase commercially," the invisible wire is actually foil tape and the walls will have to be painted to hide the tape. This tape and its sticky backing:
is half the thickness of a sheet of printer paper (after you remove the paper backing). Obtain this tape and place a small piece in an unobtrusive place (or dummy sheet of drywall). Press it down firmly, then paint over it with two coats of paint. This will probably hide it. If not, try again with a smear of spackle before painting.
Now that you are confident that the tape can be hidden, print the lamp parts.
You will need a 12 volt 2.5 watt LED bulb:
and a long wire socket:
Insert the socket wires through the bulb holder.
Drill two pilot holes and secure the socket using 2-56 machine screws.
Push the wires through the arc.
Place the diffuser ring on the bulb (it stays in place using gravity).
Place the bulb assembly on the arc. Secure the swivel point with a 2-56 screw and nut. This allows you to aim the light and tighten it.
Take a servo motor extender cable:
and cut it so that about two inches of wire is left extending from the black connector.
Solder the two outside wires to the wires coming through the arc tube. Use heat shrink tubing to cover the connection.
Crimp space lugs on the outside wires of the other piece of connector.
Insert the cable and connector through the hole in the wall box.
Glue (super glue gel) the pieces together or melt them together with a soldering iron.
The fixture is now complete.
Secure the wall bracket to the wall. The screws should enter a stud or a plastic drywall screw insert.
Run two pieces of copper tape from the wall mount to the place where 12 volt power will be available.
Fasten the connector lugs to the tape using screws. I predrilled a starter hole through the tape so that the tape wouldn't bend and twist around the screw.
Press the tape (using your finger or something soft) until it conforms to the wall. Spackle and paint (or just paint) until the tape is hidden.
Unlike my example (done in the garage), I recommend using paint that matches the existing wall, unless you want to repaint the wall.
Attach lugs to the end of the wires from your 12 volt power supply and screw the lugs to the end of the copper tape. The 12 volt power supply should be capable of providing 250 milliamps or more of current.
Cover the power source end with the power box. Secure it using two screws.
Cover the screw holes using the printed caps.
Bring the fixture to the wall bracket. Plug the connector inside the fixture to the connector at the wall bracket. Push the wires inside the fixture, then slide the fixture over the wall bracket.
Apply power and tilt the lamp to suit your taste. Tighten the screw on the bulb holder so that the tilt angle will stay in place.
The foil tape should handle more than two amps, so you can place up to ten (12 volt 2.5 watt) lamps on one run of tape (this will require a 12 volt, 2 amp power supply).
Of course, you can design your own fixture using LED light strips or multiple bulbs--or you can print the fixture in different colors or paint the fixture.