The Ultimate A to Z Tutorial of Beam Setting

Or How to Align a CO2 Laser Beam

This special RDWorks Learning Lab Video takes you step by step through the stages of how to align a CO2 laser beam.

Contents

I recall the uncertainty I felt the first time I removed a mirror 7 years ago. Would the machine ever work correctly again?

Over an 18 month period I kept purposely upsetting my beam alignment in an attempt to understand the logic behind setting the beam perfectly and soon discovered that Chinese machine designers either didn’t understand the process or purposely made it difficult for “non-professionals”.

How to align CO2 laser beam - Mirror Mount assembly
How to align CO2 laser beam – Mirror Mount assembly

I suspect my first assumption is correct and naïve machine design is responsible for the MANY different beam alignment strategies people have proposed to overcome the mess Chinese designers have created.

This session deconstructs beam alignment and machine design. I have modified my machines to make beam setting simple with a series of logical and progressive actions that guarantee setting perfection. I have tackled this subject several times over the years but never in such all -encompassing detail.

As a young design engineer I was taught that “you must understand the problem before trying to design a solution”. It seems that very few people really understand what they are trying to achieve with beam alignment beyond making sure the beam passes through the nozzle.

Russ Sadler, July 2022

The ULTIMATE A to Z Tutorial of Beam Setting or How to Align a CO2 Laser Beam

Video Resource Files for the How to Align a CO2 Laser Beam

Tube and Mirror 1.dxf

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No 2 Mirror.dxf

Head and mirror 3.dxf

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Transcript for How to Align a CO2 Laser Beam

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Welcome to another article explaining that. Today I’m going to tackle a subject which I’ve played with several times before.

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I’ve seen so much. I’m going to be rude and say crap about how to set the beam up on one of these laser machines.

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Now, this session will finish up teaching exactly how to set a beam up, why you have to say it that way.

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And it’s a complete explanation. So you can choose to ignore if you wish,

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and just fiddle with the bits and pieces of screws forever and ever and ever and never get your machine set properly.

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So I’m going to show you how you must go about this task and why you have to go about it in a certain way.

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But before we do that, I’m going to create something that I’m going to call a beam simulator.

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It’s basically a dummy machine that allows me to show you in great detail how to set the beam up.

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So the first part of this video is all about creating that beam simulator.

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Now, if you don’t want to create a beam simulator for yourself, then just jump to halfway through.

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But if you’re interested in making something similar for yourself, the drawings will be available on the art on the WW R&D Works Lab Dotcom website.

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In this session, we’re going to take a look at a problem that somebody asked for my cooperation with a couple of weeks ago.

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They were trying to design a very simple beam simulation system that would enable teaching beam alignment without going anywhere near a machine.

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We’ve got a laser beam, I turn it off and on. And the idea that my correspondent had was a very simple idea.

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Basically, he wanted to make something out of chewing gum and string. Okay, so I exaggerate slightly.

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That would enable him to very cheaply show how to set a laser beam.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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And this is the basic principle that he was working on. And so I took it through to its conclusion to see just how far and how good it could be.

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Look, the idea is you’ve got a mirror at position mirror two at position one and mirror to that position, too.

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So, hey, we’ve got a pretty good simulation there of the Y axis movement and we should be able to set up the Y axis using this kit.

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And then in addition to that, once we’ve set up the Y axis, provided, we turn this kit around and hang it off the edge of the table.

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Look, we’ve got a half which we can plug in here as well.

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So we can simulate being close to mirror number two or distance from mirror number two, and we can set up the z-axis.

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When I first saw the design, I thought, well, the design is simple, but I could see all sorts of problems with it.

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So immediately I started working on this design. I ordered a couple of linear rails from China because I felt that the only way to simulate proper

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beam settings was to use linear rails because of the stability that’s required by stability.

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Let me just show you now.

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I think you should be able to see the beam in there, but because it’s got half a millimeter of clearance on it, it’s got a diagonal twist motion.

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And look, look, what the twist motion is doing is very difficult to get this thing stable.

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And of course, then in addition to that, look,

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you’ve only got a little bit of pressure on here and things start moving in this direction is difficult to set it.

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So you have to physically hold the thing down like this to make it stable.

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So that you can adjust to be. And then when we go and send a beam through mirror one, if we take a look what’s happening on mirror two.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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Now, if I adjust the laser beam and now look what happens when I just mirror one.

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So twisting mirror one, this whole thing is totally unstable.

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There’s no way that you can ever set the be into a fixed position and be confident that it’s there.

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And of course, it gets even worse when you try and send a reflection off with mirror to when it’s at its extremity.

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This is not a full simulation of a machine because we have got no gantry moving backwards and forwards.

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Okay. But we’ve got enough of a machine here to simulate setting up the path perfectly.

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But we’re going to do it with this fitted kit. The only thing that was successful about this was this bit here.

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The laser beam itself. Every sort of laser pointer that you get has got a big beam on it.

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Yes, you can generally focus the beam down to a small point.

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But you know what happens when you focus the beam down to a small point?

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You’ve produced a conical beam, which means that the beam will be big at mirror number one,

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get smaller at mirror number two, and eventually it would be a pinpoint down at the work.

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That makes it very difficult to set mirrors one, two and three up because you haven’t got a small beam.

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This very, very cheap diode laser that I’ve got in here.

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It’s not very powerful. Look, it runs off a little battery pack like all laser beams.

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It has got a Gaussian intensity distribution.

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And what does that mean? That means that right at the center of the laser beam, we have maximum intensity.

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And so consequently, we can mask the laser beam and hide it behind a very small hole.

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And that very small hole means that we’ve got look, a little matching pinprick, pinprick size, very, very visible laser beam.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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And as I move it further away, I’m now something in the region of about two feet away.

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It hasn’t changed at all. That’s how you can exploit the intensity profile of a diode laser.

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Just used the very intense central part of the beam.

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Now, after my first attempt, here we are with my pieces, my linear rails that have arrived from China.

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And I started to redesign this dummy machine.

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And you can see that it’s now a piece of 3D equipment rather than a flat sheet,

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and that’s necessary to give us total stability, everything nice and solid.

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So I’ve manufactured this strange shaped box out of five millimeter acrylic, and I’ve mounted my two linear x and y rails on here.

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So this is going to be wonderful. I can tell you that before I start now, I haven’t designed all the other pieces for this yet.

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I’ve had to design them little by little and gradually work my way round the system.

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So look, even as we go, I’ve discovered I’ve got to make a few small design changes.

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I’ve got a screw that’s going to fix through there, and I don’t want the nuts to twist because they’re underneath.

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So what I’ve got to do is to put a little nut play underneath there to stop the nuts from twisting.

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I’ve got another piece to go on the back there, but I won’t put it on for a minute.

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You see what I mean? I want a guide for this thing to slide backwards and forwards.

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What I really should have done has allowed these two tanks here to stand up an eighth of an each project through an eighth of an inch.

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And then I had my guide in there for free. Now, I didn’t show you how to assemble the main box up,

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because once you’ve got the pieces in your hand, you it’ll become obvious how the pieces fit together.

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The next set of pieces are slightly more complex, so I will go through the assembly of these with you.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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If you note with these pieces with their long legs on, two of them have got hexagons in them and two of them have got holes in them.

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Well, what we’re going to do, we’re going to put the put the hexagon in front of the holes.

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So we want one of each plate. And on the right hand side, you’re going to have the two square holes.

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And they were going to pick up this funny piece here. I made a popper in the back and that plugs through both of those plates like that.

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And then we’ve got this one, which is exactly the same hexagon holes in front of the round holes and then you can pop that into.

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Yeah, I’m using my favorite PTG crew, which is also an acrylic cement.

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But because it runs, because it’s designed for PTG, it goes off slower.

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It doesn’t cure quite as quickly. And that’s great because it means you don’t get any cracking along the edges when you glue them.

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Whereas with normal acrylic cement, quite often you get stress cracks along the joints and I’m going to pop some glue.

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Damn these tongues. And along the back edge.

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Then these tongues. And on the back edge.

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Now you’ll see that it’s come through.

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So if we move it around just a little bit for a few seconds, then the excess glue on the underneath is not there.

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It’s dried. I’m also going to put a blob of glue down these bracket supports.

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Now, I’m also going to run a bit of glue across the top joint here because I don’t want these plates to come apart.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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There is a possibility that I might have got something wrong when I calculated the height of this.

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This is made of ten millimeters thick material to take into account the fact that this bearing plate is ten millimeters thick, ten millimeters tall.

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And I want everything to line up ten millimeters off the deck.

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But when I look at this, I think I’ve made a small error in when I put my mirror on here,

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it’s probably going to be three millimeters too low because I’ve got an additional plate on there, which is used to fix to the bearing plate.

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So I may well have to add another three millimeter matching plate to the bottom of this.

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We’re just use a really 20 millimeter type screw package and we’ve got an 83 nut which

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will pull back into the hexagon housing and we do the same at the bottom there.

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Now, this is for mirror number one.

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This is typical for number one, two and three mirror holders themselves, not the frames,

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but the actual things that hold the mirrors and make it assemble them like that.

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We’ve got a 35 millimeter em three screw with a cross head, pan head will poke that through there.

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They’re going to put an m three nut on the back and the entry nut will disappear inside the hexagon.

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On the backplate just tighten up the screws. So the nut is actually only jamming the screw on the front plate.

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When you put the backplate on, it actually locates on the nut.

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So we need to make sure that when you tighten it, tighten up nice and square,

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and even so hold it by this back bottom corner by the screw, and then we’ll put some glue.

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In two or three places around there. And that would by capillary action, that would migrate between the plates.

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And then we can push the plates together and we’ll do this.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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Just press it to make sure it’s flat for about 30 seconds.

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And then we can just hold it together and squeeze it. You only need two adjusting screws to swing this mirror around.

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That one is just a pivot point. And so I’ve set that pivot point to a fixed position, and that will leave a gap of about one and a half millimeters.

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When we plug this through here like this, there’s a hole in the bottom there into which that pin fits like that.

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The act as a pivot now for the mirror and then we put a spring on there and name three net and then I can just tighten up the nut.

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So we’ve tightened that spring up in there so that we’ve got about two or three millimeters of movement left on that spring.

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Okay, now we can tighten up these two screws on the back here.

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Now those screws drop into little pockets.

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And as we tighten the screws up, we get movement this way, which is basically directing the beam up and down by adjusting the top want.

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So as you can see, we’re now just the top one.

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What happens is this fixed pivot and this screw o’clock hinge and they cause this plate to move like that.

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And then when I want to move the being from left to right, well, it just this one because this one.

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Move the plate like that because it’s pivoted between there and that’s grew.

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So we’ve changed the hinge from that direction to that direction.

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So we get nice clean motion. We don’t get if you have a triangular system, you get strange motion.

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Now you’ll notice also that I’ve managed to get this mirror working with just one spring strategically put into the right place, I might add.

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But it’s only one spring that’s required to make this mirror system work.

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I’ve now got to manufacture some 25 millimeter acrylic mirrors, nice and cheap, to fit into this system.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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I have got some molybdenum mirrors,

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but molybdenum mirrors will change the setup of the system because molybdenum mirrors will reflect off the front face of the mirror,

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whereas this mirror is sitting right at the back here and reflects three millimeters deeper.

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Now, that might not sound a lot, but it will make a big difference to the way in which the system sets up.

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We’ve got to make sure that the laser pointer is a snug fit.

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In this whole here. And it is too snug at the moment because I’ve purposely made that about 0.1 millimeter and the size to what it needs to be.

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So here I’ve got a six millimeter drill and I’m basically going to use that like a Rhema and I’m just going to put that through there.

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But you see how easy it went through. But I’ve got to rotate it several times to take just a little teeny weeny bit of material out of there.

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And hopefully that should be enough material removed to allow me to slide,

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not slide, but I’ve got to force now, make sure we put it in the right way round.

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So the Greenpeace goes on the front.

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There’s a little teeny weeny hole up there to round about 10:00, and that matches up on the center of that hole there.

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So again, we’ve got our screw to go through there, which will help line everything up.

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But before we do that, we’ve got to do two things.

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First of all, we must make sure that we put this through here to start with.

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Otherwise, we’re going to be in trouble. And then that should.

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If I’m lucky, I might have to use.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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My electrical pliers, which have got a nice curve in the end there, just to hold onto part of that and give it a twist and a push.

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And there we are. That’s nearly flush with the front of the whole now.

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So what we do is just put this piece of black plastic on this piece of opaque plastic on, which is important for that whole game.

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We need to line these up before we lock this screw up again.

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We’ve got to put glue down between these plates. And that should be sufficiently loose that it almost comes out the bottom.

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We just turn it over and put a little bit in the bottom. Okay.

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Now we do that same trick that we did before. Make sure you keep your fingers dry.

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Otherwise, a stick. The edge is nice and square.

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Put that into its pocket. If we put that screw right through.

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Spring on the back. So would you set the plate up square?

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Although that’s not the right target.

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Do you see that the center line should be about here somewhere so we can adjust it left and right on to center, nice and smoothly.

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Now, one of the important aspects that I haven’t spoken about yet, but we will when we come to setting it up,

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is the reason why I’ve got the laser and mirror one on the same plate.

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They’re not separate. They’re together because you’ve just seen me set the beam up onto mirror one.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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And look, no matter where I move the laser beam, it’s always in the middle of mirror one.

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You can’t do that with any of the laser machines that you’ve bought. I can guarantee that.

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Okay, so I’ve added my extra three millimeter plate on the bottom there and I’ve got to put this guide plate on the corner here.

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And I think what I’d do is just something like that, hold it against the edge,

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which is where I know it’s got to go and I’ll try and clamp it in that position.

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Make sure there’s none on the outside. Just make sure push it up against it tight.

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So that’s really just a reference age to keep this in a straight line and you’ll understand why I’m doing that at a later date.

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I also made two three millimeter acrylic mirrors. So the government target just sits in there.

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And regardless of how I move this around, the target doesn’t change.

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Now I’ve got an additional hole in here that passes right the way through and I’ll drop a screw into that because that represents the No.

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One to set up position for the mirror. Well, I have to say, things are going quite well so far because I’ve got my parallel here, parallel here.

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And my target is my laser beam is virtually in the center of the target.

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So I’ve only got the smallest adjustment to do on here to get it set right on the top spot on the center of the target.

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But what we have to remember is that this beam is not hitting the surface of the mirror.

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This beam is hitting the back surface of the mirror. So it’s not actually hitting the center of the mirror as that target indicates.

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Hit it. If it was a surface mounted mirror, it would be hitting the center of the mirror.

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Now, this is the frame of a mirror to it’s virtually exactly the same as everything else,

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except it’s on a different baseplate with four fixing holes on it to fix onto the bearing.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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So we then clamp it down while it dries. And look, we make sure we don’t stick it to the plywood.

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We’ll move it around a few times and again, make sure everything is nice and square and uniform.

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No poke the mirror through the hole and locate the mirror on its pivot point at the front corner here.

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If you remember, we spring the name through, not the parallel gap there.

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Parallel gap there. We ready to assemble now acoustic the mirror zoom with a piece of double sided, strong, double sided tape.

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Well, that’s not going to come out double sided tape, but if I wanted to,

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I’ve got a hole through the back there so I can actually push the whole thing out.

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This is only three millimeters thick. The hole in the bearing is about three, maybe four millimeters thick.

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So really, I could do with an end three by six long.

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Well, I haven’t got that. I’ve got this eight millimeter long thread.

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So what I’m going to do is to put a washer and a critical washer underneath it, and that should take up the difference.

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Oh, yes. Perfect. That’s nice and snug. It’s a great feeling when a plan comes together.

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Look at that. These are the pieces for the heat. These are the pieces of the hate mounting bracket.

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And these pieces you’ll recognize here for the mirror that goes on, the hate.

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So I think we might start off by mounting a mirror on this st hate piece.

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So if you remember, we have the hexagon holes in front of the plain holes.

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And we need to squares and the right hand side. Then we can put this in the back.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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Like that. And then that sits on there.

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So get my piece of estate material out. Piece of plywood.

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We put some glue down the edge of the bracket and along from the front.

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In the back. The plate.

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And while we’re here, we might as well. Sticks and glue.

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And between the plates as well. Okay, now you try and hold the whole thing together.

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Just move it around to make sure there’s no glue underneath it sticking.

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Okay, so now we can build the rest of the aid, and the sensible way to do this is to pick this piece up.

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Put it on its side. So put these two pieces to the top like that.

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Both the same way. Okay.

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So that’s fairly stable and then we can pop this side piece on.

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There is only one way for this to go. Square corner at the top here.

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All the others have got around the soft edge on the heat assembled, and it’s completely stable now.

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So it would kind of be rotated onto its front like that. And then we can hold this between the tongues.

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Don’t put your finger on the tongue because you’re getting stuck.

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This package and this front edge mean we can hold the whole thing together for around about 30 seconds.

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Now it’s reasonably stable. Okay, so what we can do now is we can pop glue round the top faces, these side pieces.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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One, two, three and two, three.

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There we go. That’s done. Those tongues pass through the slots like that.

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And then this piece lays on the back, put the tongues upwards, and it’ll sit all flat on the back then.

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And we need to drop some glue. Into these four tongues, and you’ll see that the glue will actually run between the plates as well.

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Something I haven’t done. I’ve just noticed. I should have counted.

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Sunk these holes here. And if we’ve got that right, that should fit on their.

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And give us a nice vertical adjustment, is it?

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And then I find this is a difficult task to get this backing off.

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But I generally find that a pair of tweezers is one of the best things for lifting it off with.

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When? Okay.

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And there we go. That’s never going to come out of nowhere.

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These holes in them are going on to the bearing block.

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We’re nearly there now.

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We could have put the screw in the nut through those holes spring and a nut to hold on with some in three by 12 millimeter co two some screws.

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Hopefully they should be the right size to pass through here.

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You know, maybe they’re too long gone. Can grind a couple of millimeters off the end of the screws.

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So just fix our mounting plate. So we’ve got one more job to do.

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Taking the 25 millimeter long screw and I’m winding and not on.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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And then we pass through that hole now and we’ve got another nut on the other side.

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Now, those two nuts, they form a solid a stop for this slide.

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You see the reason for having an adjustable. Why?

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Because all I’ve got on the head here as an adjustable Z.

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Whereas in the previous design, which we had, which was this one, remember, which climbed down to the top.

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What we had, we had an adjustable Y and an adjustable Z built into this bracket.

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Well, I’m pretty happy with that. It all feels lovely. No swap at all.

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So that’s a very good simulation of a machine. Not a complete machine, but enough to show and demonstrate how to set a beam accurately.

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Now, I’ve created these targets, and unlike normal targets, these are not going to get thrown away because we’ve got no lighter burning at Target.

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That little square reference in the center there is marked in one millimeter squares.

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And remember, the beam itself is about one millimeter diameter.

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So we should be able to get an idea pretty accurately of where the beam is at each end of the well.

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Before we go anywhere near the simulator, we need to understand what it is that we’re trying to achieve.

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Now, I have to admit, I was guilty of all sorts of misdemeanors about lenses when I first started playing with these laser machines.

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My ignorance was immense, and it’s only gradually decreased with time.

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So I’m going to give you guys a flying start. The first thing we will say is that a lens is manufactured with something called spherical geometry.

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Now, look, that means that it is part of a sphere, and a sphere has an axis about which it pivots and rotates.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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And look, that axis passes right through the lens.

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So that is the axis of the lens. It is the axis that would pass through the center of the sphere if the rest of the sphere was there.

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But we’re only going to use this part at the top here as the lens.

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Here is what we are trying to achieve without being set up.

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The laser beam hitting mirror number three and bouncing downwards so that it passes right through the axis of the lens.

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Now the lens works because it has parallel rays of light hitting this curve surface.

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And those parallel rays of light get refracted off that curved surface in various degrees to come down to something called a focal point,

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which is just here. That is perfection. It is very,

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very difficult to achieve that condition because the Chinese don’t make it

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easy with the design of their machines to allow you to achieve that setting.

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I’m not saying it’s impossible. I’m just saying it’s close to impossible.

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Now, the most likely situation that you’re going to encounter is that your beam hits the mirror at somewhere other than the sweet spot.

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Now, the sweet spot is that point on the mirror, which will reflect the beam perfectly downwards and through the axis of the lens.

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As you can see in this case, we’ve hit another spot, which is not the sweet spot, and we’re not passing through the central axis of the lens now.

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But I’ve just drawn a single line for my beam. But as I said, the beam is this wide.

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But this is effectively the path of the most intense part of the beam.

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And it’s the intense part of the beam that does damage to material.

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So if we follow this beam, you’ll see that it is not passing through the axis of the lens and is actually being refracted towards the

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focal point because all parallel rays will pass through the lens and get refracted to this focal point.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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But hey, look, this is the most powerful part of the beam, and it’s going to pass through the focal point at an angle.

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That means that your cut is going to be at an angle because this is the most powerful cutting part of the beam.

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This part here is relatively unimportant.

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And this bit here, well, it’s missed the lens altogether, and it’s probably heating up the inside of your lens tube.

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Now, here we’ve got another potential situation that happens, and that is that the beam.

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May not be coming in. Absolutely true.

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Although it’s running through the center of the lens at the contact point,

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although these rays are still coming in parallel, they’re not coming in at the correct angle to the face of the lens.

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They’re not parallel with the axis of the lens.

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And because they’re not parallel with the axis of the lens, they will fly off an angle like this and they will miss the focal point.

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So hey, you’ll probably find yourself hitting the inside of your nozzle if you’ve got a small home nozzle.

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And secondly, look, the most powerful rays are also running off at an angle.

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So again, there’s another reason why you produce an angled cut on the edge of your material.

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So these are the two things that we’re trying to overcome and ignore.

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This is what we’re after. This is setting perfection.

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If you get the beam passing through the central axis of the lens, it will pass through the center of your nozzle as well.

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You must not attempt to set the beam up through the center of the nozzle.

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You must attempt to set the beam up through the axis of the lens.

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Checking that it passes through the center of the nozzle is just a check.

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It’s not a setting point. Okay, now, here is a point that I was very ignorant of when I first started setting beams up.

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This is mirror number one. And here is the laser tube up here firing the beam at mirror number one.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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I believed that probably the best way to say it was to make sure that my tube, oh, my beam was running absolutely parallel with my gantry rubbish.

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It turns out that it doesn’t matter what angle you set your tube at.

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Wherever you fire the beam at mirror one mirror one has the ability to rotate and be set so that you can even this beam here,

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which is incorrectly firing at mirror one, you can rotate mirror one and make it come out in this angle.

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So it doesn’t matter how you set the tube up.

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The only thing that’s important about setting mirror number one up is that the beam

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should hit the center of the mirror to give you the maximum scope of use of the mirror.

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Let me explain. You probably have a 20 probably a 25 millimeter mirror.

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Part of that will be masked by the frame. So you may well only have as much as 23 millimeters clear mirror.

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But when you fire the laser beam at it at 45 degrees, this is what the laser beam sees.

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It sees 23 millimeters top to bottom. But from side to side, that is round about 13 or 14 millimeters.

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So we’ve got to be reasonably accurate left to right when we come to set up our beam.

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And the ideal situation is to set the beam at mirror one right in the center.

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But if it’s a one or two millimeters high or low, as you can see, it isn’t really going to affect anything.

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So don’t get too anal about getting it perfectly on the center of the mirror.

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Lots of people believe that is the only place to set the be wrong.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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You have some flexibility north and south when you set mirror number one.

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If you follow this through to mirror number two, it’s exactly the same picture.

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So you’ve got flexibility north and south for mirror number two.

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But of course, when we get to mirror number three, the situation is reversed.

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We’ve got a lot more horizontal flexibility.

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Mirror three and not much vertical.

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But on the other hand, as I just described to you when I spoke about lenses, there is something on this mirror called a sweet spot.

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You might normally be aiming for the center of the mirror when you set the beam up in this general direction.

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But what we really interested in is making sure the beam hits the so-called sweet spot that’s on that mirror.

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So let’s take a look at the first axis that we’re trying to align, which is the Y axis down side of the machine.

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The beam comes in, bounces off of mirror one, and ideally it passes along this line here,

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which is absolutely parallel and true to this white block here, which is the bearing rail.

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And that’s the aim of the exercise. We’ve got to get that beam running true to the axis bearing rail.

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And as you can see here, I’ve got absolute perfection. I’m bouncing off of mirror one and I’ve passing through mirror number two on its center point,

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both here with its close to mirror number one, and here when it’s furthest away from mirror number one.

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So that’s A and B are the two positions for mirror two.

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What chance have we got of doing that? Well, it’s a pretty difficult task that people just do not seem to understand.

Transcript for How to Align a CO2 Laser Beam (Cont…)

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And let me explain why it’s not a simple task.

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It’s a very tedious task that depends on a process of something called iteration,

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which means you don’t get it right first time you get it a little bit better than it was before.

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And then you try again and you get a little bit better again.

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And you try again and again and again. That’s what iteration is.

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And that’s what we’re going to show you here, how important that process of iteration is to setting the beam.

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You’re not going to set a beam up in one hit for the purpose of this exercise.

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I’m going to move my mirror one out of position.

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That’s where I had it set for perfection. And I’m now going to move it out of position.

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And this is this could easily be your machine. You don’t know the relative positions of Mirror one and mirror two.

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Hopefully, the Chinese have managed to get them reasonably close together, but you can’t be sure.

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So let’s tackle it from this position. Okay.

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The beam comes in batches of mirror one and reflects right down at the end of the stroke.

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Now this is not beam alignment, so we have to adjust mirror one so that our beam at least appears on mirror to at its extreme position.

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Okay, so we’ve got a target on here and we’ve probably just burned a little mark on the target.

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And when we move back to the beginning here, we’ll put a clean target on here and we will burn a mark.

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Now, if you look very closely, you’ll see that I have simulated a little burn mark on there with a circle.

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So that little burn mark there at a is what I will call the target mark.

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So when we move A to position B and there’s the target mark there, what we’ve now got to do,

Transcript for How to Align a CO2 Laser Beam (Cont…)

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we’ve got to adjust mirror one so that the beam hits the target mark.

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Let’s look what’s happened to the beam at Position A.

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So although we’ve moved this target mark to Position B and we’ve hit the target at position B because we’ve adjusted the mirror,

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look, it’s no longer on the target, mark. We’ve created a new mark here.

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We’ll move the mirror back to position A we’ll put a new target on and we’ll create a new target mark.

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Then we move from position to position B and look, our target is not matching the beam.

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We have to make the beam hit our target.

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But think about we’ve already been running this loop once because by adjusting mirror one, we’ve moved away from the target.

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Mark, bring the mirror back to position. We take a new target and we have to burn another target.

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Mark. And we move that target mark to position be look it means.

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So no, we’ve got to adjust the beam to hit this target.

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I have already seen as soon as we adjust the beam onto the target position, be look what we’ve done at position.

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We’ve missed the target again. We have not got the beam passing through the same point at A and B, so we’ve got to create yet another target.

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And we go through exactly the same process again and again and again.

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And eventually we get to this point where we’re getting a bit fed up and we still haven’t got it right.

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Look, there’s my final attempt. I’m going to say, damn, I’ve run out of patience.

350
00:39:51,650 –> 00:40:01,400
But look, I’ve run out of patience, but I still haven’t got absolute perfection between position A and position B,

Transcript for How to Align a CO2 Laser Beam (Cont…)

351
00:40:01,760 –> 00:40:08,150
which means that my beam is not perfectly aligned to the axis.

352
00:40:08,330 –> 00:40:13,190
It’s very nearly aligned to the axis, but not perfectly.

353
00:40:13,790 –> 00:40:23,510
And that can have an effect later on. The fact that we haven’t got that beam running exactly parallel to the axis, but you get the idea.

354
00:40:23,540 –> 00:40:32,990
Look, it’s taking me one, two, three, four, five, six attempts to get that beam parallel to the axis.

355
00:40:33,740 –> 00:40:36,920
I can’t cheat. It’s taking me six.

356
00:40:38,120 –> 00:40:42,170
If you can get it done in two. It means, well, you’re nearly there.

357
00:40:42,650 –> 00:40:47,570
But trust me, you can see that even with six attempts, I have not got perfection.

358
00:40:48,170 –> 00:40:53,930
You can’t see that degree of imperfection with a burnt beam.

359
00:40:54,920 –> 00:40:59,150
It’s very, very difficult to see that degree of perfection.

360
00:40:59,420 –> 00:41:06,080
So the chances are that after three, maybe four, possibly you will think, oh,

361
00:41:06,200 –> 00:41:13,400
I’ve now got perfection of demonstrated to you that six, seven, eight times, and you still have perfection.

362
00:41:13,790 –> 00:41:17,510
You’ve got near perfection three or four attempts.

363
00:41:18,440 –> 00:41:28,520
So this process of iteration is a very important point for you to remember when you’re setting up your be patients, patients, patients.

364
00:41:30,510 –> 00:41:34,890
Now, that process that I’ve just described there.

365
00:41:36,450 –> 00:41:40,390
Is from mirror one along the y axis.

366
00:41:41,010 –> 00:41:46,320
This could equally well be mirror two and this could be the x axis.

367
00:41:46,860 –> 00:41:52,260
This could equally well be mirror three. And this could be the Z axis.

368
00:41:53,910 –> 00:42:02,910
It doesn’t matter what axis you’re working on. This process of iteration is exactly the same for every axis.

Transcript for How to Align a CO2 Laser Beam (Cont…)

369
00:42:03,840 –> 00:42:11,460
Okay, so here we have beam simulator, laser tube out here with a beam coming out hitting mirror number one.

370
00:42:12,570 –> 00:42:16,980
Mirror number two, move backwards and forwards as per machine.

371
00:42:17,760 –> 00:42:21,690
And mirror number three, moves as a machine.

372
00:42:22,410 –> 00:42:27,120
Although there’s no gantry on here, this is a simulated position for the end of the gantry.

373
00:42:27,600 –> 00:42:30,030
So we should be able to simulate setting the beam up,

374
00:42:30,360 –> 00:42:36,810
passing through three mirrors and finishing up at this point here, which is the axis of the lens.

375
00:42:37,200 –> 00:42:40,769
I’m not going to be able to get that perfection that I’ve just described to you,

376
00:42:40,770 –> 00:42:47,610
that theoretical perfection that allows me to go five, six, seven or eight times to get the perfect beam.

377
00:42:47,970 –> 00:42:51,960
We’re going to find it after maybe three, maybe four attempts.

378
00:42:52,110 –> 00:43:00,960
And that’s about as much as we can go. And we just have to accept the fact that there is going to be a degree of imperfection in our settings.

379
00:43:01,320 –> 00:43:11,459
Now, the first thing that I must state is I’ve removed the acrylic mirrors because they were starting to become a bit of a nuisance.

380
00:43:11,460 –> 00:43:14,040
When I did a quick experimental test,

381
00:43:14,550 –> 00:43:22,740
bouncing off the back of the mirror is completely different to bouncing off the front face of these molybdenum mirrors that I’ve got in here now.

382
00:43:23,730 –> 00:43:28,950
So I’ve had to go for the real thing in the end, real bearings, real mirrors.

383
00:43:29,760 –> 00:43:33,959
So we’ve got a pretty good, real simulation, as you can probably see there.

384
00:43:33,960 –> 00:43:36,180
Look at switching the laser tube on and off.

385
00:43:36,180 –> 00:43:43,710
You see that this screw is not only the fixing for the spring on the back, but I’m using it as a location for the target as well.

386
00:43:44,040 –> 00:43:48,690
And I’m locating off the bottom here to keep everything nice and true and square.

387
00:43:48,750 –> 00:43:52,900
There is. It’s not in the center.

388
00:43:54,180 –> 00:43:58,409
So remember the way in which the laser beam worked?

389
00:43:58,410 –> 00:44:05,790
If I go to the top, I should be able to make it go up and down and I can do so.

Transcript for How to Align a CO2 Laser Beam (Cont…)

390
00:44:05,790 –> 00:44:12,060
Let’s put that on to center line. And now we go to the bottom one and that moves it left to right.

391
00:44:13,140 –> 00:44:17,250
And I can move it left to right, as you can see. So let’s put that on center as well.

392
00:44:17,250 –> 00:44:25,590
So there we go. That’s nice and easy. You can’t do that as easily with your beam, but that’s what you’ve got to ideally achieve.

393
00:44:27,870 –> 00:44:33,450
So now we backed the beam off of mirror one onto mirror number two.

394
00:44:34,560 –> 00:44:38,870
We’ve got a target there. And it’s way off.

395
00:44:39,410 –> 00:44:45,260
So let’s move it to position B and you can see that the beam is way off the center of the target.

396
00:44:45,380 –> 00:44:50,840
What we’ll do, we will set that so that it goes onto the center of the target like that.

397
00:44:51,140 –> 00:44:54,280
Okay. Job done. Or is it?

398
00:44:55,120 –> 00:44:59,710
Let’s move back to position. And you see that job is not done.

399
00:44:59,950 –> 00:45:03,489
We’re nowhere near parallel. Okay.

400
00:45:03,490 –> 00:45:11,380
So what we’ve got to do now is to say, well, look, if that is our target and it’s way off.

401
00:45:12,130 –> 00:45:16,080
But if that is our target, let’s just try and make a note of where it is.

402
00:45:16,090 –> 00:45:25,660
Look, it’s just above. It’s a bear on the end of the crosshair, and it’s just a single dot, maybe one millimeter above the crosshair.

403
00:45:25,960 –> 00:45:32,580
So it’s about one millimeter off the end of the crosshair and one millimeter above the end of the crosshair at position.

404
00:45:33,100 –> 00:45:41,770
Now, I mustn’t change that because that’s my target. So we know move to position B and of course it’s way off target.

405
00:45:42,190 –> 00:45:47,500
What we’ve got to do now is to move this beam about a millimeter above.

406
00:45:48,870 –> 00:45:54,450
Across here and a millimeter beyond the cross here about there.

407
00:45:55,350 –> 00:45:58,710
But let’s have a look what happens when we bring it back to position.

408
00:45:58,800 –> 00:46:02,640
A Well, we’re now about three millimeters.

409
00:46:04,360 –> 00:46:13,000
Off of our target. That’s our new target. So you’ve got to remember that one millimeter high and three millimeters wide.

410
00:46:13,480 –> 00:46:19,570
So we’re okay height wise, but width wise we’ve got to go to about three millimeters, which is about there.

411
00:46:19,750 –> 00:46:22,300
And that looks to be about right.

412
00:46:23,920 –> 00:46:33,400
So after three attempts, we’ve managed to get that about parallel, i.e. the target that A and the target a B are the same.

413
00:46:34,810 –> 00:46:43,800
Even though we know that they’re not. But within the scope of what we can see, they appear to be the same big problem.

414
00:46:44,310 –> 00:46:48,270
We’re not on the center of mirror number two. How can we deal with that problem?

415
00:46:48,540 –> 00:46:52,440
You cannot fiddle with the screws at mirror number one.

416
00:46:52,830 –> 00:47:00,870
You’ve just used those screws at mirror number one to set the beam parallel to the axis.

417
00:47:01,170 –> 00:47:07,050
You can’t ignore that and just twist those screws to make your being come to the center.

418
00:47:07,620 –> 00:47:11,670
It’s not going to work. So that’s another very important lesson.

419
00:47:12,210 –> 00:47:15,480
There are two parts to aligning a beam with a mirror.

420
00:47:15,990 –> 00:47:20,070
Number one, align the beam parallel with the axis,

421
00:47:20,700 –> 00:47:29,370
and then you have to make a physical mechanical adjustment to the mirror to put the beam onto the center of the mirror.

422
00:47:30,180 –> 00:47:33,600
You cannot steer the beam onto the center of the mirror.

423
00:47:34,200 –> 00:47:39,450
You’ve got to physically catch the beam by adjusting the mirror itself.

424
00:47:39,630 –> 00:47:45,990
In my case, the way that I’ve got my machine set up because I thought about this a long time ago,

425
00:47:46,530 –> 00:47:54,330
about how to best set a machine up and I haven’t yet seen any or me Chinese machines that adopt this process.

426
00:47:54,420 –> 00:47:59,670
I can loosen my screws off and let’s remove this nominal fixing screw.

427
00:48:00,090 –> 00:48:07,880
And this is why I want this reference edge along here, because I can now move this beam backwards and forwards like this.

428
00:48:08,370 –> 00:48:15,570
And hey, can you see the miraculous effect that is having on the position of the beam as it hits mirror number two.

429
00:48:16,020 –> 00:48:21,690
So I can now very accurately set onto the center of mirror to.

430
00:48:23,300 –> 00:48:32,640
Hopefully because I’ve made this a parallel motion along here, I will not have affected the settings on mirror number two.

431
00:48:33,170 –> 00:48:37,100
So technically, we can see there that it’s one millimeter high.

432
00:48:39,640 –> 00:48:44,410
I have made a slight difference because the beam was so far out here to start with.

433
00:48:45,340 –> 00:48:49,150
I was guessing where three millimeters was. I didn’t have an accurate assessment.

434
00:48:49,540 –> 00:48:57,760
So now I’ve got the beam back into the center again. So I’m one line high and half a square to the right.

435
00:48:58,090 –> 00:49:02,650
I’m one line high. And half a square to the right.

436
00:49:03,610 –> 00:49:11,020
The important thing here is that it’s parallel and it’s approximately in the center of the mirror.

437
00:49:11,440 –> 00:49:21,010
Okay. So now you are looking up at mirror number three and here we are at closest to mirror number two.

438
00:49:21,400 –> 00:49:31,270
So let’s first of all, make sure that the beam hits the target at its further most point.

439
00:49:32,050 –> 00:49:38,770
I must make sure that I keep my number two mirror jammed against its end stop.

440
00:49:39,460 –> 00:49:43,500
And to do that, what I’m going to do, I’m going to cheat slightly.

441
00:49:43,540 –> 00:49:48,460
I’m going to keep it against its end stop with a very powerful magnet on the rail.

442
00:49:49,090 –> 00:49:54,590
So I’m going to push that on there and that will keep that locked on to the end stop.

443
00:49:54,790 –> 00:49:57,790
There’s our target furthest away from mirror number two.

444
00:49:58,660 –> 00:50:03,730
And we could really do with adjusting it so that it’s nominally on center.

445
00:50:03,910 –> 00:50:08,290
That may or may not be the sweet spot.

446
00:50:08,320 –> 00:50:11,410
We’re not interested in getting the beam to the center of the mirror here.

447
00:50:11,770 –> 00:50:17,800
We’re more interested in making sure that the beam is running parallel to the x axis.

448
00:50:18,220 –> 00:50:22,209
So we’ve moved our target close to mirror number two.

449
00:50:22,210 –> 00:50:30,370
Now our laser beam is arriving at one square, one line to the right and one line above.

450
00:50:30,760 –> 00:50:35,710
So we’ve got to take that very slightly to make it one line above one line.

451
00:50:37,120 –> 00:50:42,250
To the right. Then we’ll check it again. That’s pretty well lined up now.

452
00:50:42,790 –> 00:50:50,110
We’ve got approximately right in the X-axis, but it’s not spot on centerline and there’s not spot on centerline in the Y axis either.

453
00:50:50,410 –> 00:50:55,690
But let’s not worry about that. We’ll deal with that at the next stage.

454
00:50:55,750 –> 00:51:02,470
The key point here is that we’ve got the beam running true to the x axis.

455
00:51:02,860 –> 00:51:09,310
Okay. So I’m now going to plug my target, the same target into this position here.

456
00:51:10,240 –> 00:51:13,390
Now, hopefully you can see the the red dot on there.

457
00:51:13,930 –> 00:51:22,360
It happens to be two squares to the front and one square to the left of the centerline.

458
00:51:23,140 –> 00:51:33,700
Now, if we’ve got our x axis set up correctly, then theoretically it should remain in this position here.

459
00:51:33,940 –> 00:51:37,060
As I move closer to the mirror.

460
00:51:37,090 –> 00:51:45,830
Number two. The dot is one square to the left and two squares to the front.

461
00:51:46,910 –> 00:51:47,490
So there we go.

462
00:51:47,510 –> 00:52:00,860
We’ve proved now that we’ve got our beam set correct to the x axis, but now we can see that the beam is not correct relative to this z axis.

463
00:52:01,430 –> 00:52:04,490
So here we are close to mirror number three.

464
00:52:04,910 –> 00:52:07,910
And as I said, we are what we are to forward.

465
00:52:08,270 –> 00:52:11,900
And one to the left, the beam is in the middle of that square.

466
00:52:12,710 –> 00:52:16,310
So let’s move that from the top to the bottom.

467
00:52:16,520 –> 00:52:21,290
The beam is a long way off. Exactly the same axis process.

468
00:52:21,860 –> 00:52:25,730
Closing, distant. Closing distant. Closing distant.

469
00:52:26,330 –> 00:52:32,809
So this is we’ve now got to match our target, remember, which was two forward and one to the left.

470
00:52:32,810 –> 00:52:36,020
So to forward, one to the left.

471
00:52:36,230 –> 00:52:42,470
Let’s put it on top again. We know one and a half forward.

472
00:52:44,440 –> 00:52:49,239
Then on centerline down to the bottom again on the centerline.

473
00:52:49,240 –> 00:52:54,850
And one and a half forward. Check. Check on the top on centerline.

474
00:52:55,570 –> 00:53:01,180
And close to one forward. You just tweak again and that’s one forward.

475
00:53:01,390 –> 00:53:07,210
And on centerline, we’ve now achieved the beam passing parallel.

476
00:53:08,590 –> 00:53:17,860
To the axis of the lens. It’s not on the axis of the lens because the beam is not passing through the crosshair.

477
00:53:18,250 –> 00:53:23,890
The problem is, how do we get. That on the cross here.

478
00:53:25,570 –> 00:53:29,200
Again, this is something that you will not have on your machine,

479
00:53:29,590 –> 00:53:34,600
but you really want it on your machine because the only way that you can achieve

480
00:53:34,600 –> 00:53:41,560
that perfection is to go all the way back to your laser beam and start fiddling.

481
00:53:41,680 –> 00:53:52,050
Let me just loosen the laser beam off and you’ll see that look, I can move the beam by adjusting the laser tube, but hey,

482
00:53:52,270 –> 00:54:00,940
that’s a nightmare, because as soon as you start adjusting your laser tube, you start adjusting everything else that you’ve just set up.

483
00:54:01,780 –> 00:54:08,200
So you’ve got to go all the way around the houses again to try and get the perfection that you’re looking for.

484
00:54:08,980 –> 00:54:12,250
But we’ve got two ways of correcting the error that’s on there.

485
00:54:13,240 –> 00:54:18,430
First of all, we’ve got to move it in that direction there, which is a Y direction.

486
00:54:18,670 –> 00:54:30,520
I pointed out to you before that I made my y axis adjustable, so it’s very easy for me to now adjust my y axis.

487
00:54:33,000 –> 00:54:39,480
To get rid of the error. I’ve made my Y-axis accurately adjustable, so I’ve got rid of the wire.

488
00:54:40,680 –> 00:54:47,910
This is. It happens. It’s pretty good in the other axes, which is, if you like, the x axis.

489
00:54:48,480 –> 00:54:57,720
But if it wasn’t, then I’ve got another form of adjustment to adjusting screws which allow me to adjust the height,

490
00:54:58,770 –> 00:55:02,100
the up down the z axis position of the head.

491
00:55:02,130 –> 00:55:10,950
As I move it up and down, I can move the position of the beam. So as you can see, I can adjust the height of that to bring the x axis onto centerline.

492
00:55:11,580 –> 00:55:16,240
And then as you can see at the bottom position, the beam is passing right through the crosshair.

493
00:55:16,830 –> 00:55:25,260
So we’ve set this up now so that the beam is passing down here and passing cleanly through the axis of the lens,

494
00:55:25,560 –> 00:55:30,390
which you get an upright cut with all the modifications that I’ve made to my machines,

495
00:55:30,780 –> 00:55:35,580
like linking the laser tube and mirror one together on a base frame,

496
00:55:36,060 –> 00:55:44,400
making the Y adjust all relative to the head and making the head adjust all up and down.

497
00:55:44,400 –> 00:55:49,590
So I catch the beam on this mirror. I catch the beam on this mirror.

498
00:55:50,190 –> 00:55:54,750
I don’t try to steer the beam by fiddling around with the laser beam.

499
00:55:55,170 –> 00:56:03,420
My machines have been like this for the past five or six years because I found out a long time ago the Chinese design was just unworkable.

500
00:56:03,690 –> 00:56:10,320
I notice as time has gone on, there are one or two machines out there now that have got adjustable seats.

501
00:56:10,740 –> 00:56:16,500
I mean, there may be one or two that have linked their tubes and mirror one together.

502
00:56:16,890 –> 00:56:25,170
This is a rarity. So you will find your machine is probably let me be crude and say an [INAUDIBLE] to set up.

503
00:56:25,710 –> 00:56:31,200
But you understand the principles now and you may wish to go forward and modify your machine

504
00:56:31,500 –> 00:56:37,590
to deal with some of the issues that I’ve demonstrated in this very interesting little up.

505
00:56:38,040 –> 00:56:40,559
It’s served its purpose extremely well.

506
00:56:40,560 –> 00:56:48,660
Even though it can’t do everything that a machine can do, it’s demonstrated to an immense degree how you have to set your machine up.

507
00:56:49,050 –> 00:56:52,680
So thank you for your time and good luck with your beam setting.

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