Depending on your printer, add a header to the L-Cheapo’s terminals. This will connect in place of your extruder’s heater.
If you have a CNC tool with a spindle, rather than a 3D printer, the LcheapoAssemblyCNC instructions show how to switch between laser and spindle.
Mount the L-Cheapo on your extruder, either by screws or zip ties.
Lower the Z axis. If you have a kickstand, lower it in place.
Screw the lens assembly on the bottom of the laser module almost all the way out — it should not come off (if it does, just screw it back in a little), but it should be all the way extended.
Put your protection plate on the print bed, if you have one (if you don’t, the laser will burn through Kapton tape, if you use it).
With protection goggles on, disconnect your printer’s extruder and connect the L-Cheapo instead.
Send the M104 S100 command to your printer (or otherwise turn on the extruder heat). The laser will light up. If it doesn’t, switch the + and — contacts around; the extruder heater is resistive, so there is no standard configuration for it. The L-Cheapo has a protection diode and is safe to connect backwards, although it won’t work, so just try again with the connector flipped!
Use the crown on the bottom of the laser assembly to focus the laser by screwing the lens back in. Optimal focal distance is 3 to 4 inches, depending on your printer or CNC setup. We recommend using a piece of paper or cardboard as the target — when you see smoke, your laser is focused!