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Laser marking inside of part rim?

T

terrysn

Aluminum
Joined
Sep 1, 2008
Location
Ontario, Calif
Has anyone here used mirrors to redirect the laser beam of a yag to mark a surface not inline with the marker head?
We have a Miyachi LM50 100 watt yag laser marker that is used mostly for marking carbide, and HSS cutting tools. But we have a customer asking us to look into marking on the internal bore of an aluminum part that resembles a dog dish in size and shape, approx. 8" ID. Are there specific mirrors that could be used for a yag to do this, or could it be done using some sort of prism to invert the letters back to their original direction, or is this even doable at all?
Thanks,
Terry
 
You need the correct type of mirror to do it. A normal house hold one won't work even then there is potential issues with distortion due to the changing focal length. Now if its set up with a c axis and only writes in a line on the part as the part rotates that will work. Keeping the mirror clean will be very important.

Playing with lasers and mirrors is a very dangerous game, particularly with a invisible beam like a yag, not that it makes much diffrence at 100 watts! Blinkings too late!
 
Safety is always my first concern. The laser is in an enclosed cabinet with a door safety switch that kills the laser when opened. I realize that the focal point is something I would have to experiment with, but with the built in laser pointer, I at least could get close to the area needing marked. What I wasn't sure of were the type of mirrors needed. I'll do some more research now that I know that they are more specific to lasers, and not just any mirror will do.
Thank you,
Terry
 
Something in my head says gold first surface mirrors, look at some were like Edmund scientific. or the gold mine surplus places. Basically its a gold flashed optical flat, the beam gets reflected of the surface it never sees the glass or the ceramic backing. unlike a normal house hold secound surface mirror were the light enters the glass gets reflected back by the silver before leaving the glass. Glass or quartz just is not very transparent at yag wavelengths if i'm remembering correctly.
 
Can you swap nozzles? I know that drilling nozzles can be in 0 and 90degree orientations. Make sure that if you do rotate the beam 90degrees you do it in an unfocused state, or you'll just be etching and pitting the mirror. After the 90 degree turn, put your focusing lens to set the final focus length.
 
Yeah forgot that, Weavjf is right, there's a maximum amount of power you can reflect with a given mirror surface. Too much and you can heat - distort the mirror, or as said cut into it. High power optics often have cooled mirror assemblies, but that's at power levels well above your 100 watts! Equaly the temp rises can distort mounts enough to throw things out of alignment. Unfortunately for you its a function of beam size - power density, wave length, mirror surface and mirror surface quality. A few more things for you to google!
 
Oh the final focusing lens does not have to be after the mirror, just you don't want the mirror at the focal plane of the beam. Ie reflect it before it becomes a tiny spot! Like this its power density is lower - its easier on the mirror.
 
That makes sense. So the proper way instead of just trying to add a mirror would be to make a right angle assembly to replace the focal lens, with the mirror inside and the lens remounted to the end of the unit. Then experiment with the power and focal settings. Thanks for all the help guys.
 
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