Transcript for Laser Cutting Material Hazards
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The Concise RDWorks Learning Lab with Russ Sadler.
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Session 33- Cutting: Check Material Hazards.
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Well, in today’s session, we’re going to carry on with cutting, but we’re not going to really do any serious cutting today,
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but it is going to be a serious cutting session. Because I’m concerned about your safety.
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One of the biggest problems with cutting a material. And let’s just take a few steps backwards.
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We’re busy shaking molecules remember that are already shaking and warm,
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and we’re going to make them even hotter by making them shake faster with light energy.
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Now, when we shake them faster, I know they heat up,
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but get rid of the heating effect because the real thing you’ve got to concentrate on is this molecular motion.
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If you shake molecules hard enough, they will start to break down into their individual atoms and those individual atoms
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will migrate around and they will form relationships with other atoms that are nearby.
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What materials are they going to add to your cutting process?
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Are they going to be dangerous chemicals or are they going to be safe chemicals?
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That’s the problem. You are dealing with a very, very difficult to manage chemistry set here.
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Shaking molecules can be very dangerous, and that’s what I’m going to introduce you to today.
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Your safety, because before we can cut material safety, you need to understand a little bit about what might be possible,
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how it can damage you and your health and your machine.
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So I will just dive in with a quick example here and say, Look, there is only one safe material to cut on this machine and that water.
Transcript for Laser Cutting Material Hazards (Cont…)
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Yeah, I know it’s pretty bloody, useless, but that’s the only safe material.
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You can actually fire the laser at. Everything else that you fire the laser at has got dangers of some sort.
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Now what those dangers are is something that you will have to assess because it’s you standing by the machine.
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It’s you breathing the gas that’s coming off of this stuff, it’s you that’s going to be damaged.
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Now you can go all over the internet and find all sorts of guidance about what materials you can cut,
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what materials you can’t cut, for what reasons, how some overclaim the dangers.
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Some don’t even take into account the dangers at all. Look, I’ve got three pieces of clear material here.
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Let’s take a look at them shall we? They all look exactly the same. I’ve got the machine set to its maximum power and I’ve got a certain speed running,
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which I’m fairly confident will burn through all of these materials.
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Let’s have a look at this first material and see what happens. Note the fumes, note the colour of the smoke.
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Remember what colour is? Colour is what you see reflected off of whatever that smoke is. If it’s white,
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it means all that is being reflected at you.
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If it’s a different colour, well, some of the light energy has been absorbed and only some of the colour is being transmitted to your eye.
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Now that’s a very important thing because it tells you quite a lot about the chemical composition of what’s being sent off of that material.
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You might not be a chemist. You don’t have to be a chemist. What you have to be aware of, is that those colours mean something?
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Sometimes it’s danger. Sometimes you can’t even see the danger because gases are invisible.
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So we’ve got white gas underneath the product.
Transcript for Laser Cutting Material Hazards (Cont…)
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Let’s just pop that to one side, and let’s put this one on next.
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And let’s see what this one does. Hmmm, still a whitish gas. Smells pretty horrible, to be honest.
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And it didn’t cut through. It must have cut through a little bit because some of the fumes went underneath, but it didn’t cut through.
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It didn’t cut through cleanly. And before I cut this one.
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I’m going to be sensible and I’m going to put my extractor on. Oh, oh, oh, look at the colour of that.
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The first question is, would you want to breathe it?
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Look what we’ve got down here. Look at the mess that it’s made of that product. It has cut it.
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But look, it’s produced horror, horrible, treacly fumes around the edge burning, and it’s produced all this yellow stuff as well.
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This one has produced. A little hint of yellow fumes, but nothing serious.
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It was mainly white and it has actually popped out.
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But look at the quality of the finish. I mean, OK, so it’s clean, but it’s very, very rough.
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It’s not a good cut. And this one. Well look at it, it’s superb.
Transcript for Laser Cutting Material Hazards (Cont…)
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It’s almost got a mirror edge on it and it’s clean.
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So there’s a good example of how three different plastics that look the same are not the same.
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I wouldn’t want to breathe this stuff, even this stuff. Even this stuff, as you can see, it’s got a hint of yellowness about it.
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OK, now and this one is completely clean. I’ve got a small amount of air assist coming through here.
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Air, that we breathe is 78 percent nitrogen, 21 percent oxygen, and the two do not mix together.
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They exist as a mixture, not as a compound in any way.
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They’re not associated with each other and the remaining one percent, most of it is argon.
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There’s a little teeny weeny bit of things like kryptonite. Wow. Kryptonite and hydrogen and helium and some xenon and some neon.
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There’s lots of trace elements that we breathe in. The two major elements of the air that we breathe are oxygen and nitrogen.
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And so when we fire air into our cut.
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We’re adding oxygen and nitrogen into the mix of chemical reaction that’s happening down in the product itself.
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Here is the construction of acrylic, which is this first one that
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we did. Carbon four of them, hydrogen six of them and oxygen two of them. All bonded together in a certain structure.
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Now PET, which is this polyethylene terephthalate.
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Excellent, Terry. Excellent light. OK, so you say tomatoes?
Transcript for Laser Cutting Material Hazards (Cont…)
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and I say tomatoes, and I can’t actually pronounce that at all. Look carbon, hydrogen oxygen, carbon, hydrogen oxygen.
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And then we’ve got this rubbish stuff over here that was absolutely abysmal to cut – polycarbonate,
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which you’re all familiar with. Riot shields, bus shelters, all those sorts of things where you want to be vandal proof.
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Then you use this stuff because it’s almost indestructible.
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Look, carbon hydrogen oxygen still the same basic composition of atoms, but in a different mix.
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And yet they perform completely differently.
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And they also mix with air completely differently as well, because look what we’ve done to these three products.
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This one produced a really horrible yellowy brown gas fumes.
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Now, I would not go near those fumes, and they say that you can cut very, very thin polycarbonate. Well you can cut 3mm polycarbonate.
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But look, it’s absolute rubbish. The thing about brown smoke or yellow smoke is, you know, all you’ve got to do is Google,
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“what produces yellow smoke” and you’ll find the answer is, it’s nitrogen dioxide.
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It’s a very common gas that we produce from engines and cars and things like that in small amounts.
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This is not a small amount. We’re producing huge volumes of it here.
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Although I said to you, nitrogen and oxygen exist together in the air, completely harmlessly because they’re separate.
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When you start heating them up or shaking them so that they decide to break down from one structure and form another structure,
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then hey, that’s a bit of a different situation. The only time that that happens here on Earth is when we get lightning.
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That’s the only time that maybe those two chemicals, oxygen and nitrogen can react with each other.
Transcript for Laser Cutting Material Hazards (Cont…)
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So nitrogen dioxide, where on earth does it comes from with these?
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Look, we’ve got no nitrogen in these at all.
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We’ve got some oxygen, but that’s about it.
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The only reason we can ever produce nitrogen dioxide, which is this stuff here NO2, is because somehow the nitrogen in the air,
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when it’s heated up with our lovely little chemical reaction that’s taking place in the product must have bonded with the oxygen.
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Strangely enough, maybe it did. Maybe it didn’t to a smaller amount take place here because this was just a hint of yellow on here.
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I don’t know what the gases that were produced here. It wasn’t as aggressive as the gas that we produced here. This horrible brown yellowish gas.
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So the point being is that oxygen and nitrogen have got an affinity for each other, and they can combine to produce all sorts of chemicals.
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These, particularly these three oxides of nitrogen, which were probably present in this gas here, particularly the NO2. In this one,
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it may well have been some of these other gases as well, a small amount of that and some of these.
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Now these are interesting gases because this one here, NO, which is nitric oxide is a natural product that occurs in our body.
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Men may or may not know about this because lack of nitric oxide in our system produces, hmmm, a dysfunction.
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Let’s put it that way you shouldn’t rush to breathe this stuff to become a stallion because we’ve got these other things in here.
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Now, this one: N2O is nitrous oxide, which you may or may not be aware of is laughing gas.
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It’s used as an anaesthetic, or if you give birth, then it’s a pain relief agent.
Transcript for Laser Cutting Material Hazards (Cont…)
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And then this third one here, which is the nitrogen dioxide, which is the brown gas, the main constituent.
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It is a pollutant. It is also toxic. Let me just say that you are 60 percent water.
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If you add water to nitrogen dioxide, you get nitric acid or nitrous acid or both of them.
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Not a good combination.
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If you breathe this gas in, to your watery respiratory tract or it happens to get into your watery eyes, am I making the point clear?
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You have got a very dangerous chemical set here. You need to be very careful how you use it.
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Now, I don’t want to turn this into a chemistry lesson because I’m not a chemist. I don’t really understand what the hell I’m talking about.
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I know enough to make sure that I stay safe, and that’s all I can ask you to do.
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Do research on any plastics in particular that you plan to cut on this machine.
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Acrylic is a fairly benign and safe plastic, it isn’t safe.
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Don’t spend a great deal of time breathing in the fumes. Always have your extractor on, because it comes from the same family.
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Remember as all these other plastic products that I’ve demonstrated to you.
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So there is an element of danger, even with methyl acrylate. But with PVC, there’s a particular danger, and that’s this stuff here, chlorine.
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OK, now here is carbon, hydrogen and chlorine.
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When you heat this up to high temperature, what happens is the chlorine and the hydrogen bond to make hydrogen chloride.
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Now, when you add water to that, which you, remember, your respiratory tract and your eyes.
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You get hydrochloric acid. Again, not something you really want in your body.
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So that’s why I’m just informing you that plastics are a particularly dangerous group of chemicals to cut on this machine or to shake on this machine.
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OK? ABS is another material you don’t want to put anywhere near this machine.
Transcript for Laser Cutting Material Hazards (Cont…)
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You can use abs on, for instance,
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a fiber laser at a different wavelength, because the different wavelength has a different effect on the structure of the chemicals.
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It isn’t actually burning the chemical, shaking them to death. It’s only making them a little bit soft and then rearranging them.
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So there are no golden rules for these materials. The golden rules depend on the type of laser that you are using.
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Okay. With a CO2 laser, which is what we’re talking about here, ABS is a definite no no. Acrylonitrile
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Butadiene Styrene is what it stands for, and it’s got a very, very complex structure.
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I’m not going to go into the dangerous chemicals that it will produce,
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but it will produce dangerous chemicals, which you shouldn’t go anywhere near. With this one,
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the hydrogen chloride is not only dangerous to you, it’s also dangerous to all the metal parts in your machine.
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So another good reason for not wanting this product anywhere near your machine.
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Now Urethane is another product, you are going to come across quite a lot?
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But let’s just say, for example, leather belts or maybe some shoe leather.
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It’s not really
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leather is plastic, something they call Pleather and that basically is urethane with some other additives to it that make it look like leather.
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OK. Again, a dangerous material to cut. Go and do your own research.
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I’m not going to tell you the answers to all these questions.
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I’m just going to warn you that plastics are not a safe material to use. Now to make life a little easier for you.
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Um, a lot of this stuff is housed together in one website where you can find never cut these materials,
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and it tells you all about the materials and why you shouldn’t cut them.
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And then you’ve got materials here which you can cut and stuff that you can etch.
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Now you don’t have to believe everything everybody tells you because hey, look 50 years ago,
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they said that this stuff was going to stunt my growth, make me ugly and make my hair fall out.
Transcript for Laser Cutting Material Hazards (Cont…)
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Well, they were partially right. I mean, I’m six foot and I still got quite a lot of hair.
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Not every piece of information on here is technically correct.
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The window of the laser cutter is made of polycarbonate because polycarbonate strongly absorbs infrared radiation.
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OK, now what they’re saying is not the window,
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but the cover on your machine may well be made of polycarbonate, because it’s good at absorbing infrared radiation.
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And that is true. As I’ve demonstrated to you in the safety video, I put my glasses in front of the lens.
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These are polycarbonate, and it absorbed the radiation. Nothing went through. That bit is true.
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Then it goes on to say this is the frequency of light. the laser cutter uses. True,
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we are using infrared radiation, so it is very ineffective at cutting polycarbonate.
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The whole principle of laser cutting, we’re sending light energy into the surface, and it is being absorbed,
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which it needs to do and being converted into mechanical vibrational energy within the material itself.
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So this is wrong. It does absorb the infrared radiation, which is what it’s supposed to do.
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But that doesn’t make it difficult to cut. That makes it easy to cut. There’s a lot of information out there.
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Some of it is good. Some of it is a bit dubious because not everybody understands the way in which their laser cutter actually works.
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And what I’ve been trying to educate you guys in, is the basic fundamental elements of how this machine works so that you can work back up.
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Materials that are suitable for cutting; wood, many woods – maximum thickness, quarter inch.
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Well, that’s not true.
Transcript for Laser Cutting Material Hazards (Cont…)
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It really depends on the power of your machine, the lens you’re using, and the efficiency or the quality of the beam that you put into the lens.
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Here, it says, avoid oily or resinous woods. Well, yeah unfortunately,
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all woods have oil, and all woods have resin in them, as I demonstrated before.
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Look at the muck that I’ve managed to produce on my machine with tar that comes from wood.
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It’s always there. You will always produce smoke when you’re dealing with wood.
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Certain types of wood can produce very nasty chemicals.
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Remember, this is a chemistry set. Wood is no different to plastic.
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It’s still made of carbon and hydrogen.
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It really depends on the mix of molecules in the wood as to what chemicals you produce, what fumes you will produce.
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So don’t treat any material as being safe, except water.
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I’m just trying to think of the things that you could make with water. Cup of coffee, that’s about it.
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If you do a Google search, which basically says, what materials can I cut with my laser?
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There will be several sites that you come across. One of them will be this one ATX hackerspace.
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Now this is basically the one that I showed you on the machine and this is the best and most reliable one despite a couple of errors.
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But this is the basis of many lists that you see on the internet.
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Now there is another one which I’ve looked at, which is in a strange way.
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It’s better, but it’s not better. It really doesn’t tell you a lot, even though it covers a lot more materials.
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List of woods that are safe, safety cut. It’s just non-information in a strange sort of way because look MDF.
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Laser power. Medium. Well, I always use high! Speed, low.
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Well, it’s as fast as it will go when you’re using high power. May char a lot when cutting.
Transcript for Laser Cutting Material Hazards (Cont…)
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No, it doesn’t if you do it properly, it’s not char, it’s colouration of the glue and the wood between them.
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They don’t char, they turn a brown. Contains a lot of glue.
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So avoid fumes. Sorry, you can’t avoid the fumes.
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The fumes are part of the product cutting. Do you understand what I mean?
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This is this is fairly meaningless information a lot of this stuff. List of plastics, list of plastics that are safe to cut.
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We’ve already shown that polycarbonate is not what I would call class as a safe material to cut.
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I did say that some people say that thin sheet polycarbonate cuts quite well.
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That may be true, but it’s the same chemical reaction that’s got to take place, when you cut polycarbonate.
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I don’t consider any polycarbonate as being safe to cut. List of plastics that are safe to cut: Teflon.
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No, PTFE is not a good material to cut. It is toxic.
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It produces toxic fumes, and it could also have a go at your lens as well.
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So why would you put Teflon in a list of plastics that are safe to cut?
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I’m puzzled. We’ll go and test a few materials ourselves in the next session when we talk about parameters and materials.
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Now this is very confusing because it says list of materials not to laser cut.
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I love this look, coniferous wood – uneven grain structure with soft and hard areas.
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Hard to find good power setting. Yes. So it’s hard to find a good power setting.
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That’s not a reason to not cut it. It’s just that
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it’s difficult to cut. Yeah. And then we’ve got this one here, oily and resinous wood – may catch fire.
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Well, it’ll only catch fire if you add too much heat in the wrong place and don’t put enough air assist into it.
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And then we’ve got hang on. This is true. ABS it makes dangerous cyanide gas true and melts.
Transcript for Laser Cutting Material Hazards (Cont…)
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True. Yeah, it’s safe to 3D print, which is not what we’re talking about here.
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Yes. You use abs for 3D printing because you’re only melting it.
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You’re not burning it. You’re not changing the structure of the material as you are with laser cutting.
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PVC emits pure chlorine gas, which ruins the optics.
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Well, it can do, but it’s more likely to corrode the metal of the machine and have a go at you. Thick
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Polycarbonate cuts poorly and could catch fire. Well, you’ve seen a demonstration of that today. It didn’t catch fire.
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It cuts poorly and produces a huge amount of fumes, which could be poisonous, but they don’t mention anything about that there.
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So there are two other things that you could check to be safe. One of them is, say, HDPE, H D P E molecule.
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And generally, you can get information from Wikipedia, chemical formula many kinds of polyethylene, most having a chemical formula
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(C2h4)n. And then the n means it repeats because it’s a long chain.
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Okay. Well, C2H4 no oxygen in it. C2 carbon and hydrogen.
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So that looks fairly benign. So we then ask a question polyethylene films.
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Is polyethylene toxic when burned? So it clearly says here there are only two products that are being produced carbon dioxide and water.
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Well, carbon dioxide is not deadly unless you breathe it completely.
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Now you can get carbon dioxide poisoning. Carbon monoxide poisoning. Carbon dioxide is a suffocating gas.
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You can’t breathe it. It’s not a toxic gas.
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It just means that you can’t live on it. So provided you’re extracting the carbon dioxide with a good extraction system,
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then the only thing you’re left with is water, and that will probably just evaporate.
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And it says there is likely to be some carbon monoxide. You know, which again, is going to get extracted.
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It’s not deadly poisonous to you unless you are subjected to 100 percent carbon dioxide or carbon monoxide atmosphere.
Transcript for Laser Cutting Material Hazards (Cont…)
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So this is basically the search protocol I go through whenever I want to use a material on my machine.
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I will check it out first and find out what the products of burning are likely to be. By a series of searches like you’ve seen me do here.
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You will eventually get to an answer. My general advice when you look at the internet is, you believe what’s written down.
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If somebody was standing in front of you giving you the same information,
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you would assess that person and say you’re trustworthy or you’re not trustworthy.
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I don’t believe your information or I do believe your information. You don’t have that choice when you read a document.
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So the only way to check out whether there’s credibility in a document is go and verify it in several places.
Transcript for Laser Cutting Material Hazards
