Help me to understand "focus"
Help me to understand "focus"
I am playing with a laser cutting/engraving machine. There is a small wedge with the machine, with 3 widths, each width having a text on it :
- cutting 7mm wood (close to the surface)
- cutting 5mm wood
- engraving and cutting 3mm wood (far from the surface)
It allows you to set the height of the laser. I try to understand what would be the best setting to engrave rock. I understand that to etch on wood, you want a large laser to burn it instead of vaporizing it. There are even toturials on defocussing the laser to get better blacks (larger laser, more burning, less vaporizing). Random example : https://www.youtube.com/watch?v=Xcg1y2cQl-o
Now, I want to engrave rock. I don't want a larger laser. I want the hotter tinniest spot on the surface of the rock. I start to get great results on black rock (1000mm/s, 10W, 3 passes).
To get the more focused spot, should I go with the setting close to the surface "cutting 7mm wood" or with the seeing far from the surface "engraving and cutting 3mm wood" ?
Has any of you tried to engrave rock ? Do you have tips ?
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Did you ever find the answer to your question?
It will depend on your lenses and their corresponding focal length. Normally for cutting you want that focal point to hit halfway through the thickness of the material you are cutting. For etching slate I would put that focal length right at the surface.
The standard focal length for a k40, which is the laser I use, with the stock lenses is 50.8mm I believe.
Thanks. Actually I tried mnémotechnique settings and the focus does barely nothing. At least compared to speed and power. And even to precisely etch wood, I can't distinguish any variations of focus. The laser beam is really thin.