Engraving mirrors with YAG

[Joe Hillmann]

Last night I decided to see if the yag could engrave on a mirror. What I found is that the mirror has to be sitting on a piece of metal otherwise once the beam makes it through the backing it will start to burn what ever is under the mirror causing the mirror to become covered in soot. I also found that it takes two passes to completely remove the backing from the mirror and after the second pass the area that was engraved is crystal clear, whereas with a co2 the glass underneath gets etched. And I also found that it doesn't seem to matter if I do the engraving from the front or back of the mirror.(although when I engraved from the front I propped up one end of the mirror so if the beam did get reflected it would reflect into the ceiling rather then back into the laser). I know most people here don't have a yag but for those who do this might be useful information.

[Bruce Boone]

Good information to know.

[matthew knott]

Be aware that tipping the mirror won't insure a reflected beam won't return into the the galvo head, the beam comes out of the head at varying angles so there's always a danger! Ifyour focused its normally ok as the laser vaporises the aluminium but if it not the beam can return up through the focus lens and (in rare) circumstances damage the wiring and galvos (the optics are all fine, not like a fibre laser) I would recommend always marking on the back to avoid problems! I've seen inside a laser that was used to engrave the 'objects in mirror may be closer' that put on car wing (fender?) mirrors and the text was written all inside on the components of the galvo head!! Caused no real damage as it still worked fine! But better to be safe IMHO

[matthew knott]

heres another trick for you to try Joe as you like playing with your yag, get a sheet of aluminium (anodised or not) set the focus as you would normally then place a sheet of glass over the aluminium and laser through the glass into the metal, use a slow speed 100mm sec and high power and about 8khz. You will get a permanant impresion left on the glass, not sure if it has a comercial use but its a cheap way to engrave glass with a yag.