I have pained the back of a sheet of Lexan. I want to mill numbers through the paint and slightly into the Lexan. The numbers are already mirrored in my original drawing.

I did a test run. I had a fairly slow feed rate (6 inches per minute) and as high rpm as my toy CNC machine can go. It did OK but the edges of the numbers were a bit ragged. I was able to clean them up a bit with an exacto knife but I would like to improve the quality right out of the box.

Any thoughts on how I can do this? Perhaps playing with the feed rate or spindle rpm?

One thought was to freeze the Lexan to try an keep it cool for as long as possible. Not sure how long it would stay cold and if it would even be worth it.

 

Doesn't Lexan slightly resist normal hardware store paint? I know from years ago that when they painted car parts at the place I worked at that the ones made from Lexan/polycarbonate were painted with a different paint than the ones molded from ABS or other plastics.

I have seen people doing something similar without milling. They used stick on letters on the clear plastic, then painted it and peeled the letters off after the paint dried.

 

Seem to take paint OK. I will need to check to see if it is lexan or plexi. Not sure if it males a difference with paint. Whatever I have seems to take paint just fine.

I need clear numbers through a black background and I am pretty much stuck with a certain size so I pretty much have to mill.

 

Both will take paint OK. But the paint doesn't really bond like it should or does on other materials. That is part of the reason Rustoleum(I think that's the brand) started selling pains just for plastics. The surface of most plastics are just to smooth/shiny to get a good bond. Then you just end up with a paint "film" on top of the surface, not bonded to it. same reason paint on a car needs scuffed with fine sand paper before it gets repainted.

The paint made for plastics actually melts the surface to get a good bond.

 

I get all my panels made from reverse engraved lexan, using spray paint for the legends etc. Various colours if needed.
A local engraver does it on a small CNC table, but I've never asked him about feed rates, but it does make a good permanent panel.
I just supply him with a Autocad DXF file.
Max.

 

I get all my panels made from reverse engraved lexan, using spray paint for the legends etc. Various colours if needed.
A local engraver does it on a small CNC table, but I've never asked him about feed rates, but it does make a good permanent panel.
I just supply him with a Autocad DXF file.
Max.

Interesting. I never considered such a service. Sounds like a great idea. Do you pain the panels and take them in?

How did you get black and white?

What I did on my last project, I found a box with removable front and rear panels. I replaced one with a PCB (easier to cut large holes). I painted the PCB and used the toner transfer method to transfer my legend.

 

The engraver supplied everything, including reverse painting the panel, different colours are possible, he just engraves the reverse side until the clear front layer is reached and afterwards, spray paints the required colour.
I just supply the DWG file.
The main panel colour can be any from a selection.
The feature I like is there is no front engraving, which can be a cause of dirt and grease in the grooves.
Max.