Session 17 Engraving – An Overview

The Concise RDWorks Learning Lab Series

Welcome to Module 3 of the new Concise RDWorks Learning Lab Series with Russ Sadler. Module 3 will build on the information learned in the previous modules and will be targeted on the differing types of laser engraving methods and the techniques needed to consistently achieve great engraving results. We’re about to learn how to laser engrave!

In this Session, Russ starts the “Doing Process” and starts us off with an overview of engraving. The 9 processes of laser engraving explained. Surface, Deep Cut, Relief, Line, 3D, Greyscale, Photo, Laser Origami & Lace Work. What materials can be engraved?

Release Date: 5th November 2021 (Bonfire Night in the UK)

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 3 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.

How to laser engrave fox head engraving
Laser Engraved Fox head on birch faced ply

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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Transcript for How to Laser Engrave – An Overview

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The Concise RDWorks Learning Lab with Russ Sadler. Session 17 Engraving – An Overview.

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Well, here we are, I think we are in session 16.

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Now, we’ve done nothing with this machine up to now except trying to understand the technology and the various parts of the machine,

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because first of all, you are the only one that’s going to be responsible for servicing and looking after the machine when it goes wrong.

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But I hope what we’ve done so far by taking you through the various elements of the machine would take some of the instant fear away.

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When something goes wrong, it will hopefully make you stop,

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think, look at the various things that may have gone wrong in the chain and work your way back to find out what the problem is.

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Now, the mechanics of the machine are not really an issue because they’re just bits of metal screws, wire, etc.

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The real problem comes in doing something with the machine.

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And today we’re going to start the doing process. Now, you bought this machine for two reasons, one, to cut materials, and two, to engrave materials.

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I don’t think you really understood just how big the subject is. So, I’ve got to make a decision,

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now do I start you off with engraving or do I start you off with cutting?

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Now that’s a big decision for me because they are two completely different subjects.

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They are absolutely diametrically opposite in every respect.

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Now sometimes you’ll have to find some compromise parameters because you’re going to do some cutting and some engraving on the same job.

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That’s where your skill will come in making a judgment as to what parameters you should use,

Transcript for How to Laser Engrave – An Overview (Cont…)

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what lenses you use, how much power you should use, what material you should use. Oh dear, the problems are endless.

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Now, I’ve made the decision, after all, that you’re going to start off with engraving now, engraving is a huge subject.

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You’re going to have to go back to that first or second session and start remembering some of the science that we spoke about,

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because now that science of both the laser,

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and the material is going to be very, very important to you. Yes, you can sit down at this machine,

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you can put a few parameters into the program, chuck a bit of wood under the laser head and you’ll get a result.

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It might look like a barbecued piece of wood, but hey, it’s a result and you’ll be very,

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very pleased with it until you get a bit more proficient and you look back at it in a couple of years time and you think,

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how did I manage to produce something that bad? It is practice,

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but hopefully I’m going to teach you some of the tricks and essential lessons that I learned that will stop you making too much barbecued wood.

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I’m not sure that even this list fully covers all the opportunities for laser engraving.

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The thing that you first imagined is probably number one. That’s the only thing that you think about when you normally see engraving.

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This is the sort of thing that you’d think about doing some text burnt into a piece of wood.

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Okay, well, that is just basic surface engraving. Now, here is deep cut engraving.

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It’s called incised text, because what we’ve done, we’ve cut deeply into this wood.

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And I don’t think it takes a genius to work out what relief engraving is.

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The text has been allowed to come up to the surface and we’ve taken away all the background.

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So it’s the opposite of this incised text. This is line engraving.

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Now, all the lines on here are different thicknesses and I’ve achieved the different thicknesses of lines on here.

Transcript for How to Laser Engrave – An Overview (Cont…)

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By virtue of changing the distance of the focus, it’s the same lens,

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but different focal distances produce different thicknesses of lines for different parts of the job.

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So you can see these lines down here are completely different thicknesses to these very,

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very thin lines here for the cables and then here’s something that you didn’t probably know that the machine could do, 3-D engraving.

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Wood and acrylic.

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Was that a surprise? I’m not going to go too much into grayscale engraving.

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That’s a rather specialist subject, which you have actually been using grayscale engraving to do 3D engraving.

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But there is a subject of grayscale engraving that we can deal with separately on its own.

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Because you can actually do sort of try and do photo engraving with grayscale engraving.

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The next subject, photo engraving is fascinating and a huge subject on its own.

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There’s a rather handsome guy there on a piece of slate, a lovely image there on a piece of card.

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So there’s a white photographic image on a piece of black acrylic. Here

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we’ve got an amazing photograph on a ceramic white tile.

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There’s my favorite fox again on a white tile. Sometimes you come across a subject using what on earth am I going to do with laser origami?

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Sure, laser origami, is bending and folding things.

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Yes. And here I had a need recently to do some laser origami work.

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This is five millimeter thick acrylic and I put a 90 degree bend in it using the laser machine.

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Basically, I’ve used the engraving process to heat the material up beyond its plastic limit

Transcript for How to Laser Engrave – An Overview (Cont…)

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so that it would sag and allow me to fold it and put a 90 degree bend in it.

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If you go to YouTube and you just put laser origami into the heading, you’ll find that

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there’s quite a lot of things that people do with this, which will probably whet your appetite for trying it yourself.

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There’s something that I’ve added onto the bottom here called lacework.

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Now here I’ve got some very thin card and this looks like a very delicate photo engraving.

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Let me just put it up to the light. I think, as you can see, this is not quite what it appeared originally.

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This is actually full of very, very, very fine holes that’s actually allowing the light to come through.

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That’s what I call lacework. They’re just subjects.

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Now, the other thing that we haven’t talked about is what materials can we engrave?

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So you’ve only got to go back to the first science sessions. When we talked about materials and we said all materials are made up of atoms,

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but the way in which atoms combine together to make little groups called molecules, the combination of atoms to produce molecules is gazillions.

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All the gazillions of different combinations produce these different materials, and every different material has got its own properties.

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As we talked about, there are two or three special groups of materials, metals which we use for mirrors.

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These rather special transparent materials which we use for lenses and then everything else.

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Well, what we’re talking about here is everything else, because everything else will absorb or react with the ten point six micron light.

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And remember, what’s happening is we’re really stimulating the surface molecules to make them vibrate.

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And the faster they vibrate, the hotter they get.

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And they get to a certain temperature or a certain energy level where the bonds between the molecules can no longer be sustained.

Transcript for How to Laser Engrave – An Overview (Cont…)

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They break and the molecules fly off and we change from one material to another material.

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You must keep remembering that basic philosophy of how materials react.

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You cannot attack the inside of a piece of wood or any other material.

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You can only attack the surface with light. So whatever’s happening is always happening

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on the surface. It might be getting deeper and deeper and deeper, but it’s still the surface that’s being attacked, not the material inside.

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So, we will start talking about these different materials when we start doing the engraving process,

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but we’ve got these organic materials now, organic materials have got, they’ve got a rather special property.

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They will burn. They will chemically transform from something into nothing.

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Gas, they will vaporize. There are lots and lots of different woods which are made up of different molecular structures.

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So every wood is basically a different material. And it gets even worse than that because,

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look! This is all the same settings.

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Look at all these different structures of wood in this bamboo, and as you go across here, you can see that as we move from this basic structure.

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To a different piece of wood here, look at the different texture.

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This wood is reacting differently to exactly the same light that this wood was doing,

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because there’s something different about the molecular structure of this part of the wood than there is to this section here.

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You can see this is made up of strips that have been bonded together. Within parts of a millimetre,

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this wood is changing its material structure. This is really the point I’m trying to make.

Transcript for How to Laser Engrave – An Overview (Cont…)

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There is no such thing as wood. Wood is a continuously variable material.

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It’s just a family group. OK, stuff that burns.

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Now, card is basically just wood pulp that’s been bonded together,

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and one of the things about wood, card, leather, MDF is they have something that I would like to call a range of colour available to them.

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You can either very, very lightly scorch a piece of wood or you can make it black.

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So between black charring and light scorching, you’ve got a colour range of brown.

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And that’s what you can see in this picture here. But that range of colours looks like the old sepia photographs,

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and it’s very pleasing to the eye, even though there isn’t a white dynamic range in there.

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So that’s one of the properties of these materials, these organic materials.

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They have got a colour range that you can work with. Now, this next range of materials,

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I call them mineral materials because they are stone type materials, slate, granite, marble, glass, ceramic tile.

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I showed you an example there.

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Now, this next section here, mineral’s: slate, granite, marble, glass, ceramic tiles, they are what I call binary materials.

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There is no colour range on these materials.

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When you hit them with the laser beam, you produce a colour, whatever

Transcript for How to Laser Engrave – An Overview (Cont…)

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that colour is, and in this instance it’s a sort of a light grey. Okay.

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Now we appear to have a tonal colour range here, ranging from black to fairly light grey.

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So we’ve had to do some trickery to put a photograph on here.

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Now, Glass is another interesting material which we’ll talk about later on, along with granite and marble.

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Now we’ve got some more materials, plastics. There are a limited number of plastics that you should be working with on this machine.

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Some of them produce really nasty and dangerous fumes. So before you do any plastic work, do some research

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work on Google and find out what happens when you burn the material, what sort of toxic fumes you produce.

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The same problem exists with plastics as it does with mineral materials.

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You only have two colours

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normally. This is basically changing black acrylic into white acrylic so that we can produce a white image on a black background.

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Now, here we’ve got clear acrylic. Yeah, so what’s so fascinating about that?

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Well, of course it’s rubbish because you can’t see it unless you do something like this and you put a black background behind it.

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OK, so again, this is a binary material, it can only produce white marks on clear acrylic.

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Now, I haven’t got any Corian at the moment to show you, which is used for worktops

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normally. You can sort of do 3D engraving, with it even. It’s basically acrylic, which you can engrave, as you can see, but it’s filled with a powder.

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And so what you do, you’re basically melting or evaporating the acrylic away, leaving the powder behind.

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It’s a very messy process. Then we’ve got things like synthetic rubber, which is really a plastic, even though it’s a rubbery material.

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And here’s an example of that. And I’ve been successful in making rubber stamps with this material.

Transcript for How to Laser Engrave – An Overview (Cont…)

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OK, and this is relief engraving. So here’s an example of this polyester powder coating that I was talking about.

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These stainless steel flasks have been painted with an epoxy powder coat resin.

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And then what you do, you burn the resin off to leave the stainless steel finish underneath.

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And then we come to the last group, which is engraving metal. Now, remember, metal is very, very reflective,

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you cannot engrave it. In the pursuit of science and proving to you guys that you cannot engrave metal, I’ve done it.

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I’ve messed up lenses. What you can do, there are ways of changing aluminium, plain aluminium into a different material.

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This is a black surface, but underneath, if you look, we’ve got white.

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Now this white material here is basically aluminium oxide and aluminium oxide.

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It’s the sort of stuff that you use for grinding wheels, sandpaper.

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It’s a very hard material.

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And you can take aluminium, put it through this process called anodising, and it converts a very thin maybe two to five micron,

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maybe 10 microns thick layer on top of the material into aluminum oxide.

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Now, question: is aluminium oxide. Metal?

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No. It’s a, it’s a metallic compound, but it is not metal, and because it’s not metal,

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it comes into this everything else group of materials that will absorb energy.

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You can fire the laser at this material without it reflecting. Now.

Transcript for How to Laser Engrave – An Overview (Cont…)

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When they, when they finished the process off, before they finally seal the process, they allow dye to infiltrate the surface of the aluminium oxide.

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So this black on here is just a water based dye that’s been soaked into the surface of

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this metallic material. The structure of this aluminium oxide is a bit like grains of salt.

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They’ve got little teeny weeny pores or gaps between the grains, and that’s where the dye infiltrates.

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And that’s what you can see here, a dyed surface of white aluminum oxide.

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If you’re very careful about this process, you can heat the dye up, make it evaporate and left the aluminium oxide behind.

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So we’re not actually working with raw metal.

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We’re working with an oxide of the metal. And that allows us to do things like that.

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We can put photographs on here, we can put text on it, we can engrave on it.

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And then finally, we’ve got stainless steel. Now, again, stainless steel is very, very reflective.

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It’s probably in the 96, 97 percent reflective range.

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The only thing we can do is stainless steel is to chemically mark it.

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Here’s just an experimental test piece. It’s the only thing I can dig up at the moment.

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And you can see here, this is very shiny stainless steel. But I painted something on here and then I did some etching.

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When I take this grey stuff off, what’s left behind is a black mark.

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And that black mark is very, very durable. So some of the chemistry of this material has etched itself and bonded into the surface of

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the stainless steel because it’s reacted with some of the chemicals in the stainless steel.

Transcript for How to Laser Engrave – An Overview (Cont…)

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So that’s the only way you can mark stainless steel.

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You cannot engrave it. That’s a quick preview of what you’ve got coming up over the next many sessions.

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So each one of these materials and processes requires its own special knowledge.

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As I said, this is a very, very wide subject. Not only do you need to understand the laser beam technology,

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you need to understand something about material technology as well, because you’re trying to disrupt molecular structures

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remember, from the surface down. Never forget that fact, surface damage

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only. Now we’re going to start doing a section with a little demonstration.

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And I’ve got I’ve got the machine cover down for a good reason.

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I’d like you to observe some things that are going on. First of all, can you see the way in which the flame is blowing backwards?

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Secondly, I think you might be able to see that very, very bright light. Now at the moment.

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We put this piece of tape down here so you could see something else.

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The tape is, first of all, probably marking slightly wider than the beam.

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Certainly up here, look you can see that the tape, has burnt away a lot wider than the beam.

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We’ve got different damage. For different materials.

Transcript for How to Laser Engrave – An Overview (Cont…)

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This one is masking tape, which is so thin that it has no effect on the focus, but look what it’s done to the beam here.

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When I’ve got lots and lots of power very, very slowly. It was able to just burn through and basically hardly have an effect on the cut width.

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Here, it’s starting to have an effect on the cut width. Here it’s having a significant effect on the cut width.

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Here it’s virtually wiped out and absorbed all the power before its started to cut the wood.

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So that all the energy now, has gone into cutting the tape and nothing has gone into the wood.

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This is an interesting fact, do you remember this from a few moments ago?

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If we get the balance of power and speed right, we should be able to just remove the paint and do virtually no damage to the

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material underneath. There’s a huge amount of information in this very simple test.

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Which I want you to try and remember. Question one: Why are these lines A, changing width and B, changing colour?

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The next question is, why if we got a different level of damage here and here?

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Than we have here and here, but on this one, look, we got quite a large mark at the end and a little teeny weeny burn mark there.

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And then we’ve got a little blog here, which is bigger than the beam.

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I’m going to put my hand in that flame. How brave is that?

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Look, it even damaged me, you see, it’s even put a mark across, a black mark across my fingers.

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I could feel the heat from that flame as I move my hand across there.

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And it marked my hand. What happens if I do this?

Transcript for How to Laser Engrave – An Overview (Cont…)

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Apart from the fact that I’ve blown it out. I can hardly feel the flame.

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Why is that? I think you could answer the question the other way round.

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Would I do this? Come on, stop. Would I actually pass my hand through that plane at that speed? Ha Ha Ha

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I think you know the answer to that question and why, but try and analyse why I’m not able to run my hand through that flame slowly.

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I have got a damage threshold on my skin.

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If I move my hand through that flame very, very slowly, I shall A: exceed my pain threshold and B: I shall exceed the damage threshold

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of my skin and the molecules will start flying apart and do stupid things.

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Anybody familiar with photography will know what exposure means and that’s what I’m doing here.

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I’m exposing my hand to a certain amount of power in a certain amount of time.

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Now, if I reduce the time by going faster, I’m reducing the exposure time and reducing the exposure

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time, keeps my skin above the damage threshold for the flame.

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Now, I can pass that card through that quite quickly and it doesn’t mark the card.

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And now I go really slowly. And I’m in trouble.

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That’s a good demonstration of damage threshold.

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And exposure time,

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the material has a certain damage threshold and I’m exposing that material to a certain amount of power for a certain period of time,

Transcript for How to Laser Engrave – An Overview (Cont…)

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a certain exposure period. OK, so power and time equals exposure.

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So that begins to explain why we’re doing less and less damage as the speed increases.

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We’ve got the same power. And yet we’ve got and we’ve got the same damage thresholds on these two materials.

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But we’re exposing the material to a lower power per unit of time.

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And so consequently, the damage is less. That explains why the lines are getting lighter.

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There was less damage, so therefore we’re going to get less browning.

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Why are these lines thick and these lines thin? That’s for something completely different.

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That’s unique to the laser beam.

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We’ve talked about it before, but we’ll discuss it again because it’s an incredibly important feature of this machine.

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Now, you remember my little light here, how it’s very,

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very intense in the centre and it gets less and less intense as I move away from the centre of the light.

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And I said that was an exact simulation of the laser beam.

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Now, I’m going to start using a word that’s really very important.

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Intensity now some people technically will use the word energy density.

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I don’t think the word energy density conveys the right impression, whereas light intensity,

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you immediately know what it means, it’s brighter than anywhere else if it’s more intense.

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Well, the light at the centre of this beam is more intense than it is at the edge of the beam.

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This is just a graph of the light intensity within our laser beam.

Transcript for How to Laser Engrave – An Overview (Cont…)

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And as I said to you before, this is something called a Gaussian distribution.

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That’s the ideal shape of the intensity within a laser beam, not all laser beams conform to that pattern.

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If yours doesn’t, then it might be close to junk.

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I know that the beam on this machine is pretty close to that intensity distribution.

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Another very important factor, which I’ve mentioned before,

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but I’m going to keep stressing this because it’s, it’s just the most important thing that you can remember about this laser beam.

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The more intense the light, the faster it will do damage to the material.

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So the height of that graph represents the intensity and the more light intensity we have, the faster we can damage our material.

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How much damage are we going to be doing to the material just here?

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You’re absolutely right. Zero.

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And as we start climbing up this curve, we’re able to do a little bit more damage to the material provided we give it enough time to do the damage.

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If we want to do the same amount of damage from the power down here,

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we’ve got to allow that light to be exposed longer so that it can do the same amount of damage as that light up there.

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Can you see how down the centre here we’ve done a huge amount of damage and yet as we get to the edge here,

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look, it drops off fairly quickly to less and less damage to just a faint brown mark just here.

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We’ve allowed enough time for that,

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width of line there to do damage.

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There’s enough power here and there’s enough power here right at the edge of the beam width to do some browning just here, scorching.

Transcript for How to Laser Engrave – An Overview (Cont…)

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But in the centre here, this look, this section here. Which you can clearly see.

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On here. That farrow right down the centre, there’s so much power there that it’s able to do a huge amount of damage.

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Just there, but once we get outside that damage zone, the damage gradually creeps off like this.

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So we’ve just got lots of browning here, but we’ve got lots of damage in the centre.

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Now you can’t see in there, but that damage has gone in and done something like that. Now as we get towards this faster speed,

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only the highest amount of intensity, this bit just here.

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Will be able to deliver enough damage to the material in the time that’s available to it.

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So what we shall finish up with is a line width that

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is that wide. But look at the change of intensity across the top of that shape.

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It’s virtually a flat line.

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So we’re going to have no change of intensity. All we’re going to do is get like a paintbrush effect, just a very slight browning across that zone.

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And that’s why it is a thin line and not a

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thick line. I hope that this explanation gives you some sort of feeling for this concept of exposure time.

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This also explains why we’ve got these blobs at the end here, because the velocity of this beam starts off at zero,

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accelerate up to 240 millimetres a second, and then drops back to zero.

Transcript for How to Laser Engrave – An Overview (Cont…)

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And as it drops back to zero. So what we’re doing, we’re getting closer and closer to this situation

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again. We’re increasing the exposure time right at the end of the lines.

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Now, I’ve done this without any lens in the system because it shows this very clearly when we’re looking at a naked beam.

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This situation does not change when we put a lens in. Now, as I’ve explained to you before.

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There are two types of lens. We’ve got these which are flat on one side and curved on the other.

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They’re called Plano Convex.

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Now, this is one way that you can use a Plano convex lens, which everybody steers away from because it’s got, and this is grossly exaggerated.

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This has got something called spherical aberration.

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The actual shape of this lens as part of a sphere causes this problem here to happen to the light rays.

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We do not focus down to a sharp point. The rays that come in from the outside focus here and the rays that come down the centre focus down here.

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So we’ve got a huge range of focus. Now, if we turn the lens over, things start to change.

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The light comes in here. It’s refracted twice, once into the lens and once out of the lens.

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And we get a much smaller range of spherical aberration.

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There is still spherical aberration, because this is part of a sphere and it never comes down perfectly to a focal point.

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And that’s why you will be told this is the correct way to install a lens.

Transcript for How to Laser Engrave – An Overview (Cont…)

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And in general terms, it works for most things most of the time.

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And one of the ways that you can get rid of, nearly get rid of

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the spherical aberration. Is to put another spherical concave surface, it still doesn’t focus it to perfection,

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it only does an improvement on this situation that you can see here.

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We’re going to go for one final demonstration in this session. We’ve been using a beam full power, so we’ve been using it in sharp mode.

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It’s been doing a huge amount of damage at the centre and not much right at the edge of the beam.

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As we reduce the power in the beam, we’re changing the relativity of intensity between the edge

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and the centre. We can reduce a sharp beam to a blunt beam under control by reducing the power.

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So I’m going to run this same test, but this time we’re going to do it 20 percent power.

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He’s the imagined shape of our laser beam intensity diagram at 90 percent power.

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We’ve got a huge amount of intensity right at the centre of the beam, and we’ve still got nothing at the edge. When we reduce the power to 20 percent.

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We’ve still got nothing at the edge.

Transcript for How to Laser Engrave – An Overview (Cont…)

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But what we’ve got, is a much, much lower intensity right at the centre. So we haven’t just changed the power of the beam from 90 to 20.

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We completely changed the damage ratio of the beam itself.

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Its ability to damage has been changed because the intensity shape is completely different at 20 percent than what it is at 90 percent.

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And I hope you can see that from this diagram, when you change from 100 percent power to 50 percent power,

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you’re not really changing to 50 percent power.

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You’re changing all sorts of intensity things within the beam which are having an effect, a non-linear effect on the output.

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If you wish to have a linear change to the power of your beam.

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You don’t change the power, what you do, you change the exposure time, so if you change the speed from 120 to 240,

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you’ve actually doubled that, doubled the speed at which the beam is traveling and you halved the exposure time.

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You’ve halved, linearly halved the amount of damage you’re doing to the material.

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So I think you can clearly see here, the shape of the beam at this five millimetres a second.

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We’ve still got most of the beam width available to us here. But as we get a little bit faster, a little bit faster,

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we very quickly run out of beam width. By the time we get to our intensity just here, at 40 millimetres a second.

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We’ve run out of intensity.

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Now with this one, we may well have gone as far as 300 millimetres a second before we matched the intensity level of this one.

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And this one reached its intensity peak at 40 millimetres a second.

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So I hope this is sufficient proof to show you that this diagram is very valid.

Transcript for How to Laser Engrave – An Overview (Cont…)

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And you should imagine this diagram when you think about changing the power of

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your beam and also consider whether or not you’d do better to change the speed,

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then the power. I’ll leave you with all those complicated thoughts and the fact that we haven’t even put a lens in yet.

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Are you sure you want to keep your machine? Is this the time to send it back?

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I’ll catch up with you in the next session.

Transcript for How to Laser Engrave – An Overview

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Last updated August 26, 2021

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