Setting up Laser

Questions/answers/discussion about initial setup of your CNC Shark

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Setting up Laser

Postby greenetw1972 » Sat May 05, 2018 11:25 am

I just got a laser add-on and started using it. I have been able to setup and run some designs but need some advise. I ran one to test on cardboard and you can see the lines, in other words it doesnt fill in like I think it should. Is there a setting to make it more of a solid design without seeing the individual lines so much? Does this change due to the species of wood?
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Re: Setting up Laser

Postby Rando » Sat May 05, 2018 1:23 pm

greenetw1972:

That would probably be in the raster stepover in your toolpath. Make it smaller, say on the order of 0.010" (0.25mm) or smaller and see if that helps.
Like with a v-bit, that will make it take looooooonger, though :D. With the hot laser closer together, I'd expect it to get darker, so maybe turn down
the intensity 10-25% as well, so you get better mid-tones back. Check that the surface you're burning is of consistent height, or that you've mapped
the toolpath onto a solid model of that uneven/carved surface. Check that it's at the RIGHT height for the best heat: with the center of the hotspot
just a couple thousandths above the surface of the material (for the finest lines), or about 0.015"-0.020" into the surface for a deeper, and slower
burn. Somewhere in there find what works best for you and what you're trying to do. Cutting is different from engraving, etc....

And, you're right: what results from a laser's burn has a LOT to do with how the material absorbs and dissipates the heat of the spot.
Cardboard burns much more easily than wood, and it obliterates at a lower heat. And since it's just a thin sheet in the corrugated board, the heat doesn't
have any place to spread into; no real bulk like solid wood, the spot doesn't make anything but hot air. Once the laser spot has burned through the top
and maybe one layer of the internal paper, the spot is defocused enough that it's ineffective because the bottom of the focus spot is in air. But, in solid
wood, there's more wood there that can be burned, making that mark darker and wider. Remember, the laser is NOT perfectly parallel rays of light; it's a
cone, converging on a spot. So, above and below that place of highest heat, it can still burn, but not as much. And as the beam burns further into the
surface, more of that beam hits the top, unburnt surface, and is absorbed before it can reach the focus spot below, lowering the ability to burn at depth
even more. The total of all this is that corrugated cardboard doesn't burn the same as solid wood, so there are some aspects of what you get from that
that might be different than what happens with the cardboard. It's reality. I can't cut aluminum the same way I cut oak. Sadly, what that means is that
for a truly realistic trial before you ruin that expensive piece of stock, you're going to need another piece/place on that stock to try it out first. Or, take
the time to run multiple passes....zzzzz :roll:

Hope that gives you some ideas which knobs to turn for a bit better results.

Regards,

Thom
=====================================================
ThomR.com Creative tools and photographic art
A proud member of the Pacific Northwest CNC Club (now on Facebook)
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