Laser Cutter issues once more

#14

Ideally folks in an emergency just open the lid and the machine will stop.

It’s not ideal to do a hard power off at the mains when the machine is running. We were specifically advised against it.

#15

I’ve added a note to the machine referring them to this post.

Cheers

1 Like
#16

I believe this document on the cleanup of broken ZnSe optics comes from the manufacturer of the lens:

http://www.iiviinfrared.com/pdfs/Cleanup_instructions-071806.pdf

The first and second sentences read

“Toxicity studies to determine the risks of handling or ingesting ZnSe have show that this material is not toxic. However, long-term effects of ZnSe dust inhalation are unknown.”

I have heard it repeated before on Discourse and at the space that zinc selenide is toxic. I am not sure where this information is coming from, as it would appear to be refuted by the manufacturer.

1 Like
#17

Thank you for this Andrew. I had a nagging suspicion that we’d convinced ourselves this was more dangerous than it is.

Unless someone can find other evidence…

3 Likes
#18

@tomnewsom what’s the ETA for the new lens?

#19
#20

If your desperate you can be my guest at Hackney?

#21

It was out the other day, is it back?

#22

This would be a good case study for handling chemicals, it’s something that we need to get better at.

Maybe we should have a hazardous chemicals induction.

#23

Anything hazardous should show up in a RA, and approximate action should arise from that.

This is happening with screen printing where there are a range of chemical used.

#24

But does not cover stuff that people use for a one off .

#25

It’s a good point – COSHH guidelines should be the starting point for all ‘chemicals’ used in the space. We need to make that explicitly, and easy to do.

1 Like
#26

It was working Wednesday haven’t been since.

#27

I am confused. What would be a good for a case study? The zinc selenide is not toxic.

#28

My point. …

But it does have a scary name

#29

Then we could use table salt, which is actually toxic. It is also cheaper and easier to get hold of than zinc selenide.

#30

But sea salt is not toxic it can’t be it’s organic.

What is interesting about the lens is that we guessed at it’s toxicity and it took years for someone to look it up .

1 Like
#31

It is not harmless. Or rather, Hydrogen Selenide is the real danger, which is the product of the reaction of ZnSe with any acid (eg. like that in your stomach). It is toxic in very low concentrations ie. 0.3 ppm.

ZnSe safety sheet:
https://www.thorlabs.com/images/tabimages/Zinc-Selenide_MSDS.pdf
H2Se safety sheet:
https://www.chemadvisor.com/matheson/database/msds/00244337000800003.pdf

So take precautions. Don’t sand or scrape the lens to make it fit. Wear gloves when handling damaged lenses. Don’t lick your fingers! H2Se smells strongly of garlic/rotten eggs so you’ll know about it if it’s around.

1 Like
#32

That is what I am talking about.

Looking it up is a fantastic thing .

An induction to help people look up stuff that is written in a unfamiliar language, and or a team of chemical techs who have at least "A level " chemistry or degree level would be better, to help people look stuff up .

#33

Can anyone confirm that one or more of the existing lenses that we have are manufactured by II-VI Infrared? I am writing a letter to them asking them to cite their sources showing that it is not toxic, given that we have conflicting information and I have not so far managed to turn up any scientific papers on the subject of ZnSe toxicity. I will send it to them if we can confirm that one of our existing lenses did indeed come from them. I think I recall their name on the packaging of the replacement lens that we got last year.

2 Likes