Okay here was my secret plan that was a big part of the motivation for the Jackpot box design:
Some old filament I had from a long time ago…
There is some utility in this, but mostly I wanted to do this because I thought it would be cool!
Top is X, second row is Y, third row is Z.
The bottom two are probe and “aux” (rotary home or second X or whatever), neither of which are connected right now.
That is VERY COOL!!! I have some clear ABS, I wonder if that would work the same? I think I have some clear PLA as well…
Dude, you amaze me. That’s cool.
You made your own fiber optics!
I wonder how efficient the light transmission is, i.e. how far they could go.
The fiber optic light guide is very clever. Jamie, you come up with the coolest ideas!
@jamiek mind to show us how you have the filament strands at the board?
Dang!
Each hole is slightly oversized relative to the filament diameter, but the hole has a slight bend, so that it has friction to hold it in place. A precision diameter to press fit is not a winning strategy.
I use the same strategy on the backing for the front plate, so it’s held with a decent friction fit.
In the design I eyeballed the location of the LEDs but I was off a bit.
I could correct the design and then I could properly screw down the light pipe holder but for expedience I just have it a bit crooked and it seems okay.
The efficiency is pretty poor and this wouldn’t carry the light very far. It works because the LEDs on the Jackpot are rather bright and the light pipe is pretty short.
The fact that you can see the filament glowing green is testament to how poor it is.
This is what the filament looks like under the microscope:
I made a bit of an attempt to smooth it so that it would have better brightness on the display face, but I was unsuccessful with that and I gave up.
Amazing!
This is so cool @jamiek! Want to try this out now, do you think silver based ink and/or something else will help with light transmission? Happen to have some Silver based conductive ink, are you considering using small lengths of fiber optic cable, really like the idea of seeing endstop status lights, and maybe the ESP32 status light from front of the gantry given the box is closed.
He showed it’s clear filament! Not nearly as good as actual fiber optic cable, but good enough!
Just realized I misread your question. I thought you were asking if it was fiber optic cable.
Maybe another brand of PETG would already be nearly as good as an optical fiber for this application.
I don’t think a reflective coating is going to help. Total internal reflection is extremely good when it works, and a coating could ruin that effect. But I don’t know for sure. That’s my hunch.
That’s just another unnecessary complication that I now can’t live without! 
The real stuff isn’t outrageously expensive, and maybe the clear could make a neat little freznel lens to make the lights slightly bigger! 
Okay, you convinced me. I ordered some true fiber optic cable, 2mm in diameter.
I’ll have to re-do some parts to accommodate the difference in diameter, but it should be pretty easy.
I think the brightness will be worth it.
I think so - what a can of worms you have opened! 
Brilliant!
Yeah, I hate it. Now I need to add LEDs and Fibre Optics? Does it ever stop… 
But nevertheless, it’s amazing. I’d like to have that for my endstops as well. 
I love it. The probe light is the one I want the most. But having all of them like that would be awesome
This is interesting. I think actually good fiber optic cables use several rings of different refraction indices to get more TIR.
Adding a bright paint to the outside seems like it would have to reflect more, even if some was absorbed or reflected back towards the start.
But I am trying to imagine looking at the surface of water and the reflection at shallow angles compared to replacing the water with a brightly painted surface. You might be right. It might ruin that effect for no gain.
I like your light tubes from filament a lot more than buying actual fiber optic cable. It feels more macgyver. It will be unteresting as a test to see how well it performs compared to the real stuff.
Great idea though.
The best cables actually have an index gradient from the center out so can be made with fewer coating steps.
I was going to suggest painting the clear filament white and making sure the ends are sanded smooth for maximum light input and minimal edge scattering. Real fiber wins though.
I saw a project that used glue sticks to transfer light.
I do have some clear filament. Gives me some ideas!
