You can see the two spots here.
Here they are from the top. Note that the lid was nearly 6" away from the bed.
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Sure looks like a burn/melt to me. (I’ve played around with diode lasers on plastic, and that looks not unlike some of my better results.)
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Whoops!
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Oh no - is your lid made out of acrylic?
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I’m guessing that’s what it’s made from. Either that or polycarbonate I bet.
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So for anyone planning on modifying pro or basic. Hirudin’s lid could have been your eye. a Class IV laser deserves a lot of respect and caution, so please think about these things.
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Another minute and it could have been @Hirudin’s eye. 
I shouldn’t give advice about this, but - maybe consider epoxying a piece of glass on top of the lid to keep the photons in?
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I believe this conversation has convinced me that I really don’t need to experiment with titanium. 
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I’m think an investment in good laser safety glasses and developing the habit of wearing them is warranted before fiddling with titanium. That material definitely looks worth some play time and whatever safety measures it requires.
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I wouldn’t be too worried about it, I was really horsing it.
Heheh! 
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I should clarity…
I wouldn’t worry about attempting to mark titanium in our Glowforges.
My lack of worry doesn’t mean it’s 100% safe or anything, proceed at your own risk, but the settings I used for marking and the settings that I was using when the spots on my lid melted were DRASTICALLY different.
My ill-fated cut attempt was going at a speed that was ~80 TIMES slower than when marking and even then the problem didn’t become apparent until at least 30 passes had been made on the same line. On top of that, the piece of titanium that I was recklessly trying to cut through was unreasonably warped. These three factors (very slow speed, many passes, and warped stock) are so far removed from a typical marking operation that I would discourage allowing my mishap to dissuade y’all from attempting to mark titanium. Just don’t go super-duper slow.
With regard to the passthrough slot and modifications…
Great point, I couldn’t agree more!
I’d emphasize the “caution” part. I say “mod away”, but don’t be an idiot and open up an unobstructed path between the inside of the machine and people or other living things… or flammable things. The beam IS invisible after-all.
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As my students informed me from a mishap while aligning the mirrors on the laser they built… the unfocused laser beam feels like putting your arm under a high pressure, near boiling water stream when it zips across your arm from 8 feet away.
So yeah, absolutely don’t let the beam out of the bag.
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That is something I would not want to experience.
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My friend sent this to me last night while discussing the GF passthrough. As I mentioned before he works for one of the premier laser producers in the US. He and his colleagues have been watching Glowforge but I don’t know how closely.
"Pass through is as dumb as my old Smart Car (I remember that your daughter thought they are dumb). Laser beams are invisible and they bounce around - pass through is a bad idea. Don’t do it. Please Google Laser Institute of America and research laser safety.
If anything is going to blind you it is the laser. If anything is going to kill you it is the crazy high voltage power supply that Glowforge and all glass tube Chinese lasers have."
He hasn’t changed my mind but he’s certainly drilling a healthy respect for lasers into me.
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I don’t know if he has the right image in mind for what the passthrough is.
If it were a table saw style feed through, where you are actively pushing material into the laser… that would be beyond stupid.
But you put material in, leave it in one spot, then start the laser, and do not touch the material again until cutting stops for feed advancement.
Combine the “no active pushing” with the narrow size and flap (which I am sure will be trying to push closed on top of your material, thus still providing a line of sight obstruction), and there is very minimal risk.
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It will actually burn a hole in your thumb even though it’s unfocused if you get between the mirror and the lens.
DAMHIK
Someone should make them add color to it like they add smell to natural gas 
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Yeah, I charred my fingernail a while back. Fortunately I only got the nail, but the flesh below felt warm for at least two days after.
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As I said, I’m not sure how closely he’s following. He told me nobody in the office thought they’d be able to get the filter to work well enough. From what Dan says it sounds like it’s already there.
He’s promised to come and visit once it’s delivered. (I’m sure he wants to get eyes on it as much as being willing to help me get up and running🙄)
I’ve no doubt he’ll be impressed and surprised.
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The other side is fun (not)…makes a very interesting hole (that didn’t go all the way to the other side with the fingernail) - it’s like running a drill into your finger but it’s a clean cauterized hole. Takes a long while to close back up. Still wondering if there’s a hole in my thumb tissue under the skin or if that closed up too.
/warning major digression ahead
Does anyone else wonder (or know even) what’s on the other side of your belly button? Pre-natal it was pretty critical. Afterward the outside dries up and falls away. But what about the inside? Is it connected to anything?
/end major digression
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