PVC and lasers.

[Clark Pace]

So I know PVC is big side effect for pvc and it can damage the lens and optics. My job might be pushing me into doing PVC even thought I told them It's a big no no. They want to know what kind of equipment would be required to make pvc cutting possible on a laser?

Pretty much told them a flat no way. But they of course might be a little insistant. What would you guys say or do?

[Mike Null]

If it's their machine and you have properly advised them then it's their call. If it's your machine it's your call. If you expect it to be a lot of engraving and it is your machine be prepared to pay the consequences.

[David Somers]

Clark,

Also keep in mind the possible health effects if you breath that stuff as well as likely physical damage to the laser.

Dave

[Scott Shepherd]

Dave nailed it. It's deadly to breathe that stuff. Ask them which one of them is going to come run the machine that produces toxic gas that kills you.

[Jerome Stanek]

Ask them to get Osha approval for that.

[Keith Colson]

Would a waterjet cutter work for this job you have?

[Gary Hair]

You can use any mechanical means to cut it - saw, shear, knife, router, waterjet, etc. Warn them about the dangers of PVC and then refuse to be the one to operate the machine - pretty sure OSHA would be interested if they insisted...

[Robert Walters]

Laser + PVC = Hydrogen Chloride Gas, aka Hydrochloric acid gas, aka HCL.







"Hydrogen chloride forms corrosive hydrochloric acid on contact with water found in body tissue. Inhalation of the fumes can cause coughing, choking, inflammation of the nose, throat, and upper respiratory tract, and in severe cases, pulmonary edema, circulatory system failure, and death. Skin contact can cause redness, pain, and severe skin burns. Hydrogen chloride may cause severe burns to the eye and permanent eye damage.

The gas, being strongly hydrophilic, can be easily scrubbed from the exhaust gases of a reaction by bubbling it through water, producing useful hydrochloric acid as a byproduct.

Any equipment handling hydrogen chloride gas must be checked on a routine basis; particularly valve stems and regulators. The gas requires the use of specialized materials on all wetted parts of the flow path, as it will interact with or corrode numerous materials hydrochloric acid alone will not; such as stainless and regular polymers.

The Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health have established occupational exposure limits for hydrogen chloride at a ceiling of 5 ppm (7 mg/m3).^"

http://en.wikipedia.org/wiki/Hydrogen_chloride#Safety

[Dave Sheldrake]

I cut PVC on a commercial industrial laser....if you don't have the correct purification equipment and filters just don't go there. As Rob, Dave and Scotty have pointed out, it's not the machine you need to worry about, the fumes WILL turn your lung fluids into hydrochloric acid and kill you. My fume cleaning unit for that machine is bigger than the machine itself.

cheers

Dave

[Scott Shepherd]

I cut PVC on a commercial industrial laser....if you don't have the correct purification equipment and filters just don't go there. As Rob, Dave and Scotty have pointed out, it's not the machine you need to worry about, the fumes WILL turn your lung fluids into hydrochloric acid and kill you. My fume cleaning unit for that machine is bigger than the machine itself.

cheers

Dave

And Dave's "Help Wanted" Sign is permanently mounted to the front window

[Brian R Cain]

Aside from the hydrogen chloride and benzine that PVC gives off, the fume contains hydrochloric acid that will wreck the machine in a short time. To give you some idea of what it's like, I supplied a new machine to a school with a stainless steel filtration system. They asked me to service it a year later and what I found was a complete mess. As an example, although the outside of the filtration system looked as new, open the door and the inside was red rusty. Rust on stainless steel that you could scrape off with your fingernails. Inside the laser cutter, the paint had held up well, but every bolt was rusted tight.

I asked what the hell they'd been doing with the machine and learned that it only had a few hours use each day, but they cut a lot of foam board which when we checked out was made from PVC. Seriously, you wouldn't want that doing to your lungs what it had done to that extraction system.

Lasers are used to process PVC, a lot of it is laser-marked in the packaging industry but only under controlled conditions. The major filtration suppliers offer special epoxy-lined extraction systems for it, but it clogs the filters as quick as you can wink and the fume is highly inflamable. Don't go there.

And on the subject of foams...

I've often been asked if a laser is suitable for engraving foam, and the answer is yes, so long as you can live with the fact that the foam will shrink away from the heat, but I've always asked the people who asked me to find out what chemicals the foam is made from, because that's what the fume will contain. I've heard that sometimes they can contain cyanide, but I'm no chemist, and I doubt too many of you are too. The bottom line here is that when you turn a material into fumes, you're releasing whatever the material was made from into the atmosphere and possible more if intense heat turns it into something else.

I remember when I was an youngster and an engineer was showing me how to precision machine PTFE. He said "you'll be safe enough so long as you ain't got a cigarette in your mouth at the time or the fume it gives off gets nasty when it gets hot."

While I think about it, it's worth mentioning that most plastics give off a lot of fume when they're new. I believe they call it out-gassing. By the time you get them in your shop, most of the fume has gone, but then you cut into them and start the out-gassing over again from the cut edges. People wonder whether their filtration systems are working properly when their workshops stink of acrylic, and it's a close call to say whether the filter needs changing or they ought to do something about all the acrylic off-cuts they have lying around along with the work in hand or if they have a filter issue. Remember, the extraction system can only deal with the fumes coming off the material while you're cutting it. It can't deal with stuff you leave lying around your shop. Acrylic will release fume for several hours after it's been cut, so good ventilation helps with that.

Time for a fag, I think having got that lot off my chest, and possibly as I enjoy it, I'll reflect that on her recent visit to Cuba, my daughher asked what I'd like her to bring me back and I said you'll know what when you get there. The thing that Cuba is most famous for. She came back with a couple of Che Guevara t-shirts, so clothes but no cigar.

[Brian R Cain]

Whoops! Took me longer to post than I realised. Dave's said all you need to know. It's more trouble than it's worth. Let you boss do it if he wants to to and go flip burgers so you can be at is funeral.

[Clark Pace]

Thanks,

It's their machine. Did accidentally cut pvc once. Person gave me a piece of acrylic to cut at work. Long story short it had white mask paper on it. Or that is what is looked like. It was acrylic, then white vinyl then paper mask on top. After cutting it the person said look what you can do? I said what? You cut vinyl. I was very upset. I told them if I had known if was pvc I would never have cut it as stated many times. I'm hoping they don't demand it of me.

[Dave Sheldrake]

And Dave's "Help Wanted" Sign is permanently mounted to the front window

how'd you guess Scotty

It's horrible stuff and the pro fume unit has to be serviced on a monthly basis, where possible I pass on the jobs or send them out for waterjet I'm always surprised by the number of people who say "it's only a little job" or "just this once"

cheers

Dave

[Robert Walters]

Actually, PVC out-gasses for 25 years.

As far as PTFE (Teflon) goes, once it hits about 550F it out-gasses too and is toxic to breath.
Wanna guess what temperature bacon gets up to when frying?


Brian,
You should have texted her a picture, I bet you won't make that mistake again =)