The Ultimate A to Z Tutorial of Beam Setting

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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 laser 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 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 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 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 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 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 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 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 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 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 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 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 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 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 laser 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.

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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…)

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which means that my beam is not perfectly aligned to the axis.

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It’s very nearly aligned to the axis, but not perfectly.

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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.

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Look, it’s taking me one, two, three, four, five, six attempts to get that beam parallel to the axis.

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I can’t cheat. It’s taking me six.

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If you can get it done in two. It means, well, you’re nearly there.

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But trust me, you can see that even with six attempts, I have not got perfection.

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You can’t see that degree of imperfection with a burnt beam.

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It’s very, very difficult to see that degree of perfection.

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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.