Hi everybody, 
My project to build the cockpit of the Cessna 172 goes on and, after programming the Arduino Mega cards one for buttons and switches, one for the throttles and one for the knobs for the instruments, I am going to build the annunciator panel. Inspired by an idea other member I will build, with the printer 3d, the frame where to insert the LEDS but I dont know how I will make the decals with the writing, you have any idea for me? 
How and where I must print the written (normal paper, transparent sheets or other? )
Hello and thanks

Pietrogramma, I'm also doing a C172, but I'm using Bodnar interfaces.

To make illuminated legend annunciators the best method is traditional wet photography. It is possible to photograph artwork (or, possibly, a computer screen; I've not tried this) using monochrome film so that the negative, if neatly cut from the film strip, forms the mask itself with no further work needed. This process is capable of exquisite accuracy and has few limitations as cameras up to 5x7 or even 10x8 are readily available.

If you can find someone who still has a photosetter the output from this is even better than film, as it is thicker and stronger with very dense black, but the process gives only a limited choice of fonts. I used it to produce legends (not illuminated, but placed on a white background in a black panel) for the dashboard of a sports car I built in the 1980s.

Engraving a black-coated acrylic or other transparent panel would produce masks directly. If done in reverse the whole panel could be dimly sidelit with individual legends appearing as required.

Failing these one can print onto some kinds of transparent film using an inkjet printer. Unless the printer is expensive the black probably won't be very dense.

A more modern method would be to use a tiny colour screen and display a graphical annunciator array on it, then arrange to view it through the 3D-printed frame. I believe  this is should be possible using AirManager, as it has a standard 'instrument' which is the C172 annunciator array.