This is a basic clip that allows to mount a single 5 mm LED onto the X axis of a FlashForge Creator Pro, Dreamer, or similar printer (anything vaguely looking like a Replicator probably). When using a high performance narrow-beam LED like a Nichia NSPW500GS-K1 driven at 20 mA, this can add a nice amount of sideways lighting (see the second photo for a “before vs. after”), that moves together with the Y position. The LED is aimed such that it will provide optimal lighting for the middle X position.
This is especially useful if you have mounted something that blocks the light from the printer's own LED strip, like my dual fan duct. Now I no longer need to check with a flashlight whether the first layer is OK or not.
You will need to route some additional wires coming from the base of the printer. You can zip-tie them to the existing cables that go to the X stepper. Do not attempt to skimp on wiring by powering the LED from the 5 V line of an endstop, I tried it and although it seemed to work at first, after a while some fuse tripped or a circuit got overloaded, and shut down the line for several hours (which luckily had as only effect that the endstop LED did not light). It did recover after a while, but occasionally the LED doesn't light up. Luckily it is only cosmetic.
Your best and safest option to power the LED, is to hook up a completely independent supply to the mains line (you can piggyback on the screw connectors of the PSU, which will also switch the LEDs together with the rest of the printer). This is what I initially did, it eliminates any risk of overloading the PSU, or blowing up something non-protected on the rather expensive main board. After I had installed a Raspberry Pi for my variable fan speed controller, I simply tapped into one of the 5 V pins of the Pi's GPIO pin header. (You could take this a step further by actually making the LED switchable through a GPIO pin, but then you should not drive the LED directly from the pin but do it through a MOSFET board of some kind.)
More risky options are either hooking up an LED driver to the 24 V output of the PSU, or (most risky) tapping into one of the 5 V points of the mainboard. I cannot tell whether those points are all fed by the main regulator or by a much weaker regulator inside the microcontroller. I also don't know how much margin the regulator has, so hooking up anything that draws more than a few dozen milliamps is risky. If you overload something, your entire board may be toast or require difficult repairs. You have been warned. Again, a separate supply is a much safer solution, and not much effort.
Things tend to get pretty warm near the X stepper, therefore I would recommend ABS for maximum heat resistance. PETG is probably also OK.
A brim or raft may be needed.
Whatever material you print this in, you will probably need to blast it with the cooling fan at full power even if it is ABS, because this is a small part and the layers might not cool quickly enough on their own.
If the LED doesn't fit, use a 5 mm drill to ream the hole.
Added v2 version which is aimed slightly lower so it lights up more of the print. This is also a tad longer so it has less risk of colliding with modded carriages, and the overall shape has been made such that it is less likely to warp when printed in ABS.