Session 35 – Let’s Get Laser Cutting: Part 2

The Concise RDWorks Learning Lab Series

Welcome to Module 4 of the new Concise RDWorks Learning Lab Series with Russ Sadler. Module 4 will build on the information learned in the previous modules and will be targeted on the process of laser cutting. Russ will explain the science behind the laser cutting process and go on to demonstrate the techniques needed to consistently achieve great laser cutting results across a variety of materials. So, learn about laser cutting facts and work more safely.

In this Session, Russ starts with the dangers associated with using honeycomb beds. He also discusses air flow management and the importance of speedy fume removal. Alternative bed solutions and stand-offs to aid in air flow management are demonstrated. Finally Russ gives examples of deriving cutting parameters for different materials.

Release Date: 11th March 2022

Over the last 6 years, Russ has built up a formidable YouTube following for his RDWorks Learning Lab series which currently has over 200 videos.

The original RDWorks Learning Lab series on his “Sarbar Multimedia” YouTube Channel, follows Russ as he tries to make sense of his new Chinese laser machine and to sort out the truths, half truths and outright misleading information that is available on the web.

Six years later with over 4.5 million YouTube Views under his belt, Russ has become the go to resource for everything related to the Chinese CO2 laser machine user or wannabe user.

Laser Cutting facts: Acrylic vapour igniting under a honeycomb bed
Acrylic vapour igniting under a honeycomb bed

In this new series, Russ has condensed his knowledge and experience of the last 6 years to provide valuable information and insights into the purchasing, understanding, use, repair and maintenance of the Chinese CO2 laser machines and their key component parts.

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Session 35 – Let’s Get Laser Cutting: Part 2

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Session 35 – Let’s Get Laser Cutting Facts: Part 2

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Transcript for Let’s Get Laser Cutting Facts: Part 2

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Transcript for Let’s Get Laser Cutting facts: Part 2

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The Concise RDWorks Learning Lab with Russ Sadler.

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Session 35: Let’s Get Cutting – Part 2.

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Now here we are on part two of our adventure into cutting, with a fairly serious warning.

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Now I’m going to edit in some video that I’ve done previously.

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So I’d like you to settle down and watch the next few minutes of video very carefully.

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Now this honeycomb I’m in love with, but I’m afraid this honeycomb here, I’m 99 percent divorced from.

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Now, if you’ve been watching my series, you’ll appreciate just how much I do dislike this stuff.

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Remember, I said I’m 99 percent divorced. I do keep an occasional acquaintance with this stuff for the sake of the kids.

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Now this stuff looks as though it should be so amazingly good for use in this machine.

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But in reality, it’s bad in so many ways, and it’s also particularly dangerous.

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The thing you’ve heard me mention many times is about airflow management through your machine.

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Now,

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this particular machine has got some sort of concession to airflow management through the machine in that he’s got some grills across the frontier.

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Those grills are not particularly large when you relate it to the suction I’ve got coming out of my Purex extraction unit.

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Now, to solve that problem,

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I’ve got a couple of stops in the corner here which give me about a 25 millimeter gap across the bottom of my door when I close it.

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So I’ve got a nice stream of air being pulled into the machine.

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Now, once that air gets into the machine,

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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practical experience has told me, we need to get it across the work surface as quickly as possible and out the back of the machine on those grills.

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So we’ve got something, what I would class as a cross flow of air. Now what does this stuff do?

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Well, we got our extraction underneath here in this cupboard underneath the machine, and it’s busy sucking out from the back of the machine.

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You would think that this would be great at pulling air downwards and taking it away from your work.

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Let me give you a demonstration. So we’ll just turn on the extraction unit.

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Now I’ve got the door completely open.

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So what we should be able to see is how efficient this is at extracting air from underneath this job as we want it to. Now we can see several things.

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Can you see the fumes hanging in those pockets there?

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Now we can see that because this is a nice, clear acrylic. You wouldn’t normally see that if it was MDF or anything else.

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I’m sure, you will be able to see that, around the edge of here, we’ve got all sorts of strange marks.

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Well, that’s where you’re getting reflections of the honeycomb itself. Condensate is exactly what it sounds like, if you breathe on a window

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you get condensate. Because your warm breath condenses on the cold surface, and that’s what’s happening inside here.

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We’re getting acrylic condensate, settling inside here.

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And if we cut wood, we get all this horrible brown, condensate sitting inside here.

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When you look at this, logically, it makes perfect sense that

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this is really no good at extracting the air from underneath your job. The kerf is only something in the region of about 0.1mm thick.

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So we’re not exactly driving a great deal of air through the kerf.

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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So all this lovely air, we’re busy sucking through the machine, where is it going? When we’ve got the door closed,

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It’s coming in here and it’s immediately finding the quickest and easiest way it can out of the machine.

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Which is through there in the back of the machine.

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It’s going nowhere near our job, so we’re not going to get a lot of air, sucking through that cut line.

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OK, let’s temporarily improve the situation, should we?

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In fact, if anything, it’s worse. Look, we get more condensate.

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And then in addition to that, I don’t know whether you can see that from time to time, you get an orange glow.

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There’s some burning taking place in these cells. Now I’m going to put you inside the machine

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underneath the work table so you can see what’s happening inside the machine.

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I’m going to close the machine door and turn the extract system on.

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This is re-condensed acrylic vapour, and what you’ve been watching underneath there is burning acrylic vapour,

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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which builds up in the honeycomb cells and the excess energy from cutting is igniting those fumes, that are trapped in the honeycomb cells.

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Exactly the same sort of inflammable fumes happens when you cut wood.

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But you won’t have noticed that with wood because you can’t see what’s happening underneath the wood.

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Whereas, I can watch it. You can see orange glow explosions taking place through this clear acrylic.

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I’m very fortunate with this machine. In that, this is not a permanent fixture, and I can put some stability back into my life with this sheet of steel,

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which completely covers the table except for a small gap around the edge, which we’re not really going to worry about, that odd five percent.

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But what that does, that forces the air now, through the front of this machine and it’s going straight across that plate

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and out the back there. I’ve got some 10 mm thick acrylic blocks. We’ll place our work on those blocks.

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OK, now we’re looking through the gap in the door, at the plate and the gap underneath the plate.

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You can just see the black nozzle there. I hope you can now see the way in which the air is dragging away all those fumes underneath.

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They’re not getting a chance to settle and condense. They’re just being ripped away.

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This time, we’re going to cut it flat on the metal surface.

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And I’m sure you can see all that vapor settling down on my metal surface there. It’s condensing,

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as I told you, it would do. Let’s catch that
in the light. It’s got all the horrible acrylic condensate stuck to the bottom of the job.

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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Now I want to demonstrate something to you with my blow lamp here. So once acrylic is warm,

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it takes very little for it to ignite. It starts producing its own vapor, which catches fire.

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Now the reason I’m showing you all of this, as you see here, I’ve got this sticky vapor which is now condensed,

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and every time you cut acrylic, those fumes will start sticking to the inside of these honeycomb cells.

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Now, whenever you cut acrylic or any material, there will always be excess energy which passes through the cut.

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And if we look carefully at my table here, my steel table. Where I had the acrylic sitting right on top of the table.

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Look, there’s the excess energy that’s actually gone in there and actually marked my steel. About a year ago,

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I helped a guy install this machine in his factory. I gave

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him a few quick lessons. And off he went. And a year later, he’s decided to upgrade his machine, and he’s gifted this to me.

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How lucky can a guy be? Well, let me give you a quick tour of my new acquisition.

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I’m sure you’ll be very impressed. Well a little bit of damage to the paint work.

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But hey, nothing that a little bit of, a little bit of work can’t fix.

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And yeah, I think the door struts need a little bit of attention as well. Now,

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I think you can see here the remains of the job that he was doing.

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It was a piece of acrylic. Now, the main reason why I’m showing you this is to illustrate the dangers of fire and acrylic and honeycomb.

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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Those three things go together. How do I know that?

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Well, this is about the sixth machine that I’ve seen it three years.

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Yeah, now undoubtedly, there’s many more around the world, but those are the ones that people have said to me, Hey, Russ, I’ve been an absolute idiot.

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I walked away from my machine. And here’s the result.

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Fortunately, it was insured and I got it replaced under my insurance.

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I don’t know whether this was an insurance write-off or not, but that’s beside the point.

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The danger is there, whether your machine is insured or not.

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So just take this as a cautionary tale and look carefully at how you use your honeycomb.

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Don’t ever walk away from your machine.

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In this particular instance, it was a production machine, as you can see, the guy is not going to stand here and watch all of these pieces being cut.

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Words fail me! OK, well, in the last session you saw that we had a serious little chemistry set here, which could do your health a lot of harm.

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The second thing is, it’s also a fire hazard if you don’t treat it with respect.

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Now, you might need to clean this or replace it on a regular basis, depending on what sort of work you’re doing.

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The third and most important thing, you have one of those handy! On the one occasion that you need it,

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you’ll regret not having it. Now, I don’t want to make you paranoid or frightened of your machine just because you happen to have one of these in.

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Some people do not have the opportunity to take it out like I do.

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So you don’t have a choice? Well, you do have a choice. You could unscrew it and you could bolt in a sheet of steel.

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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The crap that sits on the sheet of steel doesn’t catch fire.

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It’s also a marvelous heat conductor, so you never build up any serious amount of heat to cause a fire.

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But that doesn’t mean to say you’re absolutely safe. What is the purpose of this stuff?

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I use it when I’m, when I need to be lazy.

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When I do my cutting for acrylic, making jigs. I’m not worried about what the edge looks like because this is not a show item.

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It’s much easier to lay out a sheet of Perspex and just let the pieces sit on top there.

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But that’s laziness. I could equally well do that with sheets of material.

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Sitting on spacers which lift the material off here, which allows airflow underneath, and there’s far less risk of that fire if you do this.

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But there are some times when you cannot use this sort of approach. So look sometimes when you want to cut paper like this.

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My targets that I use for aligning the beam. I mean, I lay that straight in there and you can see along the top here.

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Look, you can see the marks.

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It doesn’t matter in that instance because it’s an unimportant job, but it makes life a lot easier if I can just lay a sheet of paper on there.

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And maybe if the worst comes to the worst, I can just put a couple of magnets on the corner to hold the sheet down.

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I’m never going to be able to use pins for doing this sort of job.

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It’s a fabric material of some sort and I’ve got no idea what it is, so I’ve no idea what the settings are.

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This is the only way that I can deal with a piece of fabric like this to get it flat.

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We’ll set our focus up to 5mm, I’m not going to change the nozzle.

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I’m still going to keep my, I’m still going to keep my two and a half inch lens in here.

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We’re going to do a quick test. Remember what I said? Maximum power, even though this is a very, very thin material.

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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I’m going to set it to maximum power 90 percent and then we’re going to run my one inch square test.

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But this time we got to run it at what, 60mm a second? A hundred millimetres a second.

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Let’s try 60mm a second.

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I mean, as you hear, I’m guessing, but I know it’s going to be very fast because I’ve got a fairly thin material which is going to burn,

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and I’m hoping that it’s going to seal the edges when I burn it. I’ll tell you what, we’re going to run it at 100 millimeters a second.

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That’s pretty fast. And.

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Well, that looks pretty good, doesn’t it? Let’s do something silly and try 200mm a second shall we?

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Well, it looks as though it’s made it. Now,

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I’ll tell you what, I’m going to play safe and I’ll tell you, I’ll tell you why I’m going to play safe after I’ve done the job.

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I’m going to leave it at 100 millimetres a second. So I’ve got quite a big piece of material on here.

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It’s got a little kink in the bottom here. I don’t think it will be a problem, but if there was any kinks in here,

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I could very easily just put little magnets in the corner of the work like that.

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Now this is a stretchy fabric, so I don’t want to for any stretch in the fabric itself because otherwise,

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as it cuts, it’s going to pull away and distort. As this is a plastic.

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Let’s play safe. I don’t think there’s any dangerous fumes in here, but we’ll still play safe.

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Everything has worked by the look of it. I could sort of try and claim it’s a about posing pouch.

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But in reality, here’s what it is. It’s a new covid mask for me.

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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I’m just going to use this piece of 3mm birch plywood for test purposes.

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This is one of the problems you get with birch plywood.

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So I’ve got a small magnet there which will work on this stuff, and if I put it on the diagonal corners.

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It’s basically now flat. So we’ll just set this back up to 5mm. I’ve got this set to full power, and I’m just going to run this at 35mm a second.

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No, it didn’t. So let’s drop it to 25 nearly, but not quite.

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It’s a bit weird. It’s not particularly brilliant in there, that’s a bit mucky that lens. Now I do all sorts of silly experiments with this machine.

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So yeah, this is not normal use. Sometimes I have the air assist on sometimes the air assist off.

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So I have to keep an eye on my lenses normally, because I can get fumes up inside the nozzle.

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I’ve made these very handy, lens pliers. They’re clamps that enable you to hold the lens while you’re cleaning them. Open it up and pop it over over the lens – isopropyl alcohol.

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We do need to make sure that when you’ve cleaned your lens, you take the film off the surfaces with a lens tissue.

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Now, if you haven’t got any lens tissue, soft toilet tissue will do the job.

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Don’t use kitchen roll because kitchen roll has got an abrasive material embedded into it.

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If you catch in the light right. You’ll see what I mean. It’s got like a hole in the middle of it.

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I may well have damaged the actual anti-reflective coating on that which, as you can see, it still works as a lens.

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But hey, it may well have lost some of its performance. Now I’m a very lucky boy with lots of lenses so I can fairly quickly find another lens.

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The problem with these lenses is you can’t see through them.

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I can’t use my little gauge here, which I normally use for checking the focal distance of lenses that

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I don’t know what they are. I do know that, that lens that came out of there was a two and a half inch, and I’m going to show you a little trick now.

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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Can you see the difference between those three lenses?

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We’re looking at the LED array on the back of my machine there and reflecting it off the face of the lens.

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This is a two and a half inch. This is a this is a two and a half inch.

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Because look,

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the LED’s are exactly the same size on both. The curvature on both these lenses is the same. It’s producing the same refraction magnification.

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But look at this one. This one has got much smaller LED’s on there, and there’s more of them. Which means that the curvature on the top is greater.

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And if the curvature on the top is greater, it means that that one is a much shorter focal length.

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You might like to understand this very simple trick about lenses as well. Now some lenses have got a meniscus face.

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But if it’s a long focal length lens with a meniscus, the meniscus is very,

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very short and you won’t be able to easily see it. Use the flat face of your lens as a mirror.

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Put it right up to your eye so that you can see the side of your face and the background way behind you.

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Now, I’m looking at the mirror over in the other side of the workshop there, and I can see a perfect image of that mirror.

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If I happen to pick up a meniscus lens, here’s a meniscus lens, which you can’t see, and I do the same thing.

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What I shall see, is all the hairs on the side of my head, very nicely in focus.

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Not the background, the background, will be blurred,

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and that’s the quickest way that you can find out whether or not you’ve got a meniscus or a plano convex lens.

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Well, I may as well show you all my tricks while we’re on this little diversion. Although this is designed as a 20 millimetre lens holder.

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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I can use it for 18mm as well, buried in the bottom there.

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I’ve got another lens ring that I’ve popped in there.

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Okay, I’ll screw that lens ring right down as far as it’ll go.

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But that lens ring has been machined on the underside, not that side, but the underside with a groove in it.

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Look, I’ve cut that so that it takes and locates

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an 18 millimetre lens, so it centres up an 18 millimetre lens in a 20mm lens holding tube.

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So we now put an O-ring on top, and that stops the lens, that stops this ring from compressing the lens too hard.

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So you only have to use your fingernail in there and you can feel just a little

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teeny weeny bit of compression on the lens and it doesn’t rattle at all. We’ll set our 5mm up again.

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We’re running at 30mm a second. And look now. I am going to keep that as an example, because that didn’t quite come out.

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So we’ve got our cutting power back, and I’m going to push the speed up to 35 again.

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It’s just about made it. Now this one, I had to push out.

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It was cut perfectly all the way round at 30mm a second.

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Just here what we’ve got. We’ve got an imperfection.

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We’ve got an air pocket in the middle ply and that air pocket has basically destroyed the cutting power to the bottom layer. Look,

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you can see it’s cut, cut, cut, cut up to there and then it’s cut, cut, cut beyond there.

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But this little bit here, where we’ve got our imperfection has not cut.

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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What’s happened is, we’re just about cutting through very nicely, comfortably,

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and then all of a sudden we get to this air pocket here, which is going to fill up with smoke.

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And I described to you what smoke does it?

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It absorbs energy. So that smoke in that little air pocket has absorbed the energy and prevented the cut from completing.

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Now that’s a fairly common problem on plywood.

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Now here’s what honeycomb does to the back of your plywood.

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Look at all these marks around the edge here, where the beam has gone over the metal and actually caused a spark and over burnt the back edge in places.

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OK, well, the little problem with the lens was not something I planned to do in this session,

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but it was good that it happened because there’s no way I could have easily simulated that.

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Well, I’m going to take leave of this device now, and I’ll return to something that I trust.

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These are flexible standoffs that move anywhere that I want, but I’ve got another version as well, which I use now, which are these things look.

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A piece of thin stainless steel with a couple of magnets glued to them. Still allows the airflow to go right across the machine.

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We won’t get these marks on the back now. We’re going to do two or three tests, and then I’m going to ask you a couple of questions.

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We’re going to run a test at 25mm a second, which we know will cut.

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And that’s what I’ve cut a little square inside another square inside a big square.

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OK, let’s run the same test again at 40mm a second.

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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We’ve got no cut on the outer shape, but we’ve still got a cut on the inner shape and particularly on the corners,

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look how dark they are and look how dark this little middle one. Now,

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if I’m careful, I should be able to push the middle one out.

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But I certainly won’t be able to push the, I certainly won’t be able to push the outer one out.

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Why is it, the cut is still OK on a small square, but it’s certainly no good on a large square?

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Why are these black marks here, cut through and yet the rest of the cut not cut through?

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Hopefully, that is a clue that tells you what’s going on. This is something I like to call the Ferrari effect.

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Imagine you’re taking your brand new Ferrari out for a drive to impress your friends.

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OK, now I want you to use your imagination for a minute. This is a great big, long, straight road in the form of a square.

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It’s maybe a mile long. You live in a house just here, and it’s a great big straight road with no houses on it.

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So you can drive out of your house and you can boot it all the way down this straight road.

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Now, I reckon it’s probably going to be about here by the time you get to 200 miles

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an hour, because you can’t instantly go from nothing to 200 miles an hour.

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But your car is capable of doing 200 miles an hour, so you’re happily speeding along here at 200 miles an hour and then you see the corner coming up.

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You have to drop down to zero speed to turn round this sharp corner and then you can boot it again.

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And off you go! 200 miles an hour, 200 miles an hour down to zero again, now that’s fine.

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You can use the 200 mile an hour limit on your car if you’ve got a long, straight road.

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Look here, we’ve got an inner ring road. You try and do the same thing on this one.

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You might get up to 150 miles an hour or 120 miles an hour before you have to slow down for the corner.

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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Now we make the road even smaller.

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And here, if you’re lucky, you might get up to 60 miles an hour before you have to put the brakes on and turn the corner.

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Do you get the idea?

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We got a 200 mile an hour car, but we’re not able to use that 200 miles an hour here and here. Let’s bring this back to the world of laser machines.

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I’ve set a speed here to 40mm a second to do all of these cuts at this point here.

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Speed is zero. And it starts off, and the machine, just like the Ferrari, has to accelerate from zero speed to 40 millimetres a second.

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And as it takes off from zero, so it leaves a black mark here in the corner.

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And then it travels up and it gets to maybe 40 mm a second here and it travels all the way

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along here at 40 mm a second before it has to put the brakes on to go around the corner.

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Now 40mm a second is too fast for this

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wood. There is remember, a damage threshold on the wood and there is an exposure time that’s required to damage that wood.

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If you travel too fast, you are not allowing enough exposure time for the beam to burn through the wood.

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And that’s the situation that we’ve got here. We’ve exceeded the exposure time required to damage the wood,

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except on the corners where we’ve slowed right down to nearly zero speed and we’ve allowed the exposure time to increase.

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And when we increase the exposure time we cut through, and that’s why we cut through on these corners.

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We’ve got this set to 40 millimetres a second. We’ve got these set to 40mm a second,

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but we never making 40mm a second in the middle here because we haven’t accelerated fast enough to get up to 40 millimetres a second.

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We might be doing 30mm a second here, so it has just about cut through at 30 millimetres a second.

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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But here we’re probably only doing 25 millimetres a second or less.

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So you can see the effect of the dark corners, the very, very slow burn that takes place in the corner.

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And that’s why we were able to push this one out, because effectively the speed on here has self-regulated itself to maybe 20 millimetres a second,

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even though we set the maximum speed to 40mm a second.

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There’s just not enough distance for the machine to achieve the speed that you have set.

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And so it will run at a slower speed and therefore the cut will be more complete.

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We’ll get a longer exposure time. Now, that’s a very important point for you to remember.

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So using the one inch square test block is a very good way to determine your speed.

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But it could mean if you’re not careful, that on some of your very small parts, you might be over burning them.

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So if you do find that you’ve got overburnt very small shapes on your product,

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you might have to pull those very small shapes out onto a separate layer and you have to adjust the parameters to suit.

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You might have to reduce the speed, or you might have to reduce the power.

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And if we look carefully at these lines, you’ll probably see the perforations that I mentioned when we were doing the acrylic test.

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They’re not particularly distinct here. Sometimes I’ve seen them very, very distinct.

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This machine is not as bad as some machines that I’ve seen or worked on.

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So we know going to change to a piece of 3mm high density fiber board.

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HDF, now this is not wood. This is a mixture of wood, sawdust and plastic

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that’s been bound together with heat and produced this very nice fiber board.

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You might remember back when we looked at my big lens comparison data sheet and one of the things that we looked at in there,

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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the time that it took for a lens to penetrate X amount of distance into a piece of acrylic.

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Now you might say, well, that’s very good for comparing lenses against each other.

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But what does it really mean to me if I want to try and use it to assess what speed I’m going to use to cut this material?

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You may also remember something else I said. Plywood or ordinary wood, cuts roughly twice as fast as acrylic.

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And we found out that this stuff cuts at roughly 30 to 35 millimetres a second.

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Now, looking back at that chart, you’ll find that for 4 millimetre penetration into acrylic, this lens will take roughly six milliseconds.

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It takes 12 milliseconds to reach six millimetres deep.

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Now, the cut with the kerf width with this lens is roughly 0.2 of a millimetre.

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So here I have drawn, the beam doing a cut.

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And here I’ve drawn a larger version of that cut.

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Now, if I take the beam, which is 0.2 millimetres wide and I move across half a beam 0.1, point one, point one, point one,

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I’ve got roughly 10 cuts, 10 pulses, if you like per millimetre will allow me to approximate to a continuous speed a continuous cut.

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So I’ve got 10 of those pulses in a millimetre, and each one of those pulses takes six milliseconds.

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So therefore it takes approximately 60 milliseconds to cut one millimetre.

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This lens, this material, because this material is the same as acrylic.

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So let’s turn it on its head and we say right.

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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One second is a thousand milliseconds. How many of those 60 milliseconds are there?

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And the answer is sixteen point seven, about 17 millimetres per second.

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So that’s the speed that we expect to be able to cut this material at. Now it might turn out to be 15mm a second.

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But it should get us into the right ballpark of a speed for cutting this stuff,

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and I’ve achieved that from those penetration characteristics for this lens. So I’ve changed this to 16mm a second.

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I’ll turn the extraction on because we’re going to produce a lot of smoke this time, a lot more smoke. Turn my air assist on full.

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Let’s put it up to 20mm a second. Let’s try 25mm a second.

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There we go. Now, that’s how you basically find the optimum speed of cutting. That very simple experiment there.

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Now we’ll turn over and we’ll have a look at this one and see what’s happening on the back. Now as it happens.

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It’s not bad. Now, the problem we’ve got here is we’ve got a very thin cut on the bottom.

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It is a through cut. But remember what I said to you about the tapered cut?

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We’ve got a wide cut at the top and a very narrow cut at the bottom. That’s not very efficient cutting.

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Yes, it’s cut, but it’s not efficient cutting because we haven’t got much airflow through the cut.

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Now I will be able to find, undoubtedly that will push out.

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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Look, both of those will push out. OK, now those three cuts there, are all reasonably close to the cutting speed.

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As you can see. I’m going to do the opposite now. I’m going to drop that down to about 8mm, a second, maybe five millimetres a second.

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Now why would I want to drop it to five millimetres a second? Hopefully, I should be able to show.

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Now, look what’s happening here. Underneath there, look, I happen to have a piece of debris.

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That was busy burning. So, there’s still a risk of fire even

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with my steel plate. So you must make sure that you remove debris when you’re cutting.

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I’m going to do it again, just in case there was any affect with that smoke from underneath there.

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And we’ll also take a look what’s happening underneath the job as well.

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There are several things that I want to show you from this exercise. Remember, we went from 16 to 20 to 25.

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Take a look at the damage, the brown muck that’s been blown out of the cut.

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Remember, I said as we get as we get faster, we’re reducing the gap at the bottom of the cut into a V and

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we’re choking the airflow through the cut, so we’re not forcing the fumes out the bottom of the cut.

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Look, they’re coming out the top of the cut here and we can see them sitting on this edge here, brown debris. When we’re using very,

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very low, five millimetres a second. We’ve got no browning on the top because all the air is blowing right through the cut.

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We’ve opened the cut up so much that it’s allowing the air to flow through.

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And then when we look on the backs of the cuts, all these cuts are nice and clean on the back.

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But the ones that are going slowly here, look, we’re getting reflections back off the base plate. Because we’re going so slowly,

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the back reflection off the base plate is having a chance to burn the back of the cut. There’s

Transcript for Let’s Get Laser Cutting Facts: Part 2 (Cont…)

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one further observation I’d like you to

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look at here. I’m sure you can see which is the odd one out. Look at the colour on the one on the left that was done five millimetres a second.

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That was the one with the burning on the bottom of the back of the cut.

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Black means you’re not moving fast enough. As you get towards pale brown,

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like all the others, you’re into the right zone of speed for cutting.

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This is an indication that you’re running too slow, and that tells you absolutely that you’re running too slow.

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That’s quite a lot to take in for our first serious venture into cutting.

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We’ve got a lot more to go. In this session, we’ve covered most of the basic points. In later sessions,

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we’re going to experiment with different materials.

Transcript for Let’s Get Laser Cutting Facts: Part 2

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