As my LASER is an attachment for my CNC router it isn't within a box with a tinted window, so I have to wear LASER-safety glasses whenever it's running. So I designed this simple shield with dark red windows (as the LASER is blue). It comprises a small frame that slips onto the LASER module (with a hole for a screw if needed to stop it sliding down) and a three-sided shield that slides onto the edge of the frame.
After printing the front and two sides need to have dark red plastic glued in: I cut mine from a plastic square photography filter I picked up cheap on eBay. Then those three pieces need gluing together at the front corners to make the shield. The shield is then easily removed for when you want to focus the LASER or for removing cut materials. And in case you need to make adjustments I've included the OpenSCAD file.
This design is also compatible with my simple LASER extractor system. If you're interested you can read more about that here:
Update 9th January 2019: I've updated the files here just to add a completely optional bottom component. I decided it would be useful for a couple of reasons, the first one being that it adds some rigidity, if you're worried about that. The second was more important to me: it stops air being sucked in from outside so much which helps extraction efficiency, especially when the shield overlaps the edge of the material being cut.
And if you're interested you can also read my blog-post about this project at the link below.
I printed this at 0.2mm layer height, 30% infill, slow speed and with thick shells.