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Comment by jfim | Hacker News Reader

A few things with regards to safety that aren't mentioned in the article.

Get laser safety goggles that are appropriate for the wavelength of your laser, and get them from a reputable source. Always wear them whenever the machine is powered.

Make sure to have a way to easily and quickly de-energize the laser for when stuff catches on fire, be it an e-stop button or using an outlet with a switch.

And don't ever cut PVC. It'll generate chlorine gas, which will either injure/kill you or corrode your machine.

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Excellent stuff! I will update the article to add these items, one I actually thought off during the writing but forgot to include (the first) the rest I didn't think of but certainly should have. Thank you.

Edit: update the article.

i think technically it's hydrogen chloride, not chlorine, that makes cutting pvc hazardous

Alternatively, a machine with a proper enclosure and interlock makes the laser goggles unnecessary.

Something else I might add is don't try to cut plywood with phenolic resin. I'm not entirely sure how hazardous the fumes and residue are (probably the main risk is formaldehyde), but phenolic resin also just doesn't cut very well at all. At least, not with a CO2 laser. I'm not sure if diode lasers do better.

What seems to work well for me is to check the edge of the plywood -- if it looks like there's a thin black line between the plys, that means it's probably phenolic and it'll make a sooty mess if I try to cut it.

That's a good thing to know, I had not yet come across this information anywhere.

I haven't heard it talked about much either, it seems to be folk knowledge. Awhile back I bought a batch of the wrong kind of plywood and was having a terrible time cutting and thought it was something wrong with the machine. Eventually I stumbled on an online discussion thread about phenolic resin glues, and the plywood I bought had those thin black lines between the plys.

I found an old scrap of the plywood I had been using before and without those thin black lines and it cut fine. So, that's what I've been using ever since.

This is precisely the sort of thing that I'm aiming for with this article, a collection of all those little bits of lore in one spot. It's so incredibly diffused that you spend days just reading to get started. I want to reduce that friction to a minimum to get people up and running safely.

Most plywood is glued with phenolic glues whereas melamine glues will behave better with a laser: https://n-e-r-v-o-u-s.com/blog/?p=6042

I've found that plywood that comes in 4'x8' sheets usually uses phenolic glue, whereas the stuff that comes in 5'x5' squares usually doesn't. "Exterior grade" or "marine grade" anything is also a strong predictor that it uses phenolic.

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