Session 12 – Let’s Switch The Laser Machine On

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The Concise RDWorks Learning Lab with Russ Sadler: Session 12.

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Let’s switch the machine on. We’re now going to jump into the second section of this introduction to Chinese laser machines.

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We’ve covered all the major chunks, functional chunks of the machine in the previous 10 sessions.

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And, you note, that we haven’t even turned the machine on yet, really. Only just to have a quick look at various things.

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I’ve got two laser machines in this workshop at the moment.

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The glass tube machine that you’ve been, that you’ve seen me using in the first few sessions is a 600 by 400 millimetre machine.

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It’s halfway between the sort of machines that you might have, 700 x 500, or this one, is a 300 by 500.

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It’s a typical cheap starting Chinese machine, which I bought for just over a thousand pounds.

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But this no longer has a glass tube in it. This has been modified to include an RF tube in the back here.

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So this would normally be the sort of very expensive 20, 30 thousand dollar machine that you can buy.

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Well, it didn’t cost me anything like that, but I’ve got all the ability to experience raw RF technology.

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Not the menu driven RF technology that you tend to get on these very expensive machines.

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They will never really teach you much about laser technology.

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They will teach you how to use menus.

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We may well get into this RF technology at the later stages of these videos, but it’s not something I want to concentrate on.,

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certainly at the moment. Our main aim is to teach you about the typical Chinese laser, which contains a glass tube.

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Although this has been converted into an RF machine,

Transcript for Let’s Switch The Laser Machine On (Cont…)

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this is still basically a 500 by 300 Chinese laser with a CO2 beam that comes out here. The RF laser in the back there,

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is just a different way of producing a CO2 laser beam.

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So everything about this machine will be fairly typical of most Chinese laser machines.

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So what we’re going to do today is to turn the machine on for the first time.

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And we’re going to explain what happens before you even think about putting a program in here,

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because there’s a lot going on and you need to understand what’s going on,

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because remember, you are your only 24/7 service tech on this machine, which is why you need to understand how it works.

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OK, let’s turn the power on.

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Right, that’s it, we’ve turn the machine on and it’s ready to run now. But that very simple set of motions that you saw there, there’s a lot going on.

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So let’s try and break down exactly what we’re seeing. First of all, we’ve got two limit switches here.

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Any convenient piece of metal, and here I happen to have a small spanner. If you put it in front of these switches,

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you can see from the reflection in there, that it switches on and off because it’s got an LED in there, which tells you what’s going on.

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Now, we’ve got one over the back here as well. These are metal sensitive switches.

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They’re Hall effect switches. They do exactly the same job as a mechanical micro switch, which you might have on your machine.

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Let’s just turn the machine off for a minute. Now before you turn this machine on,

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there is already registered in the brain, the controller,

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which we’ll show you later the dimensions of the work area for this machine. Which happens to be 500 wide and 300 deep.

Transcript for Let’s Switch The Laser Machine On (Cont…)

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So the machine knows that much about its work area, but what it doesn’t know is where that work area is.

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For example, the head here at the moment is in a position.

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Now, if I turn the machine on and the machine said, OK, that’s zero, if it tried to move 500 that way, there isn’t enough room for it to move 500,

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this way. It’ll drive into the edge. And similarly, there isn’t 300 this way for it to drive.

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So it has to know where zero zero is because that’s the start of its work area.

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And so what it’s doing here is moving to this switch here, which is putting its head right in there.

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And then it’s moving to this axis here, which is putting the head right over in that corner.

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And now the machine says, ah, now I know there is zero zero and I can move 500 millimetres this way without crashing into anything.

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And I can move 300 millimetres this way without crashing into anything. Built into the brain,

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is this very simple start-up program to try and detect zero zero.

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So we turn the machine on again. I will try and explain to you what’s happening. Now,

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we’re only going to concentrate on one axis, which is this axis here. This axis will be doing exactly the same thing.

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In fact, what I will do, I will push this access to the back so that it doesn’t confuse the situation.

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We will only see one axis of movement when I turn the machine on now, which will basically be this axis here.

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Now you’ll see that this very slow, this fairly slowly creeps towards the switch,

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it hits the switch turns it off and it moves slightly this way, turns the switch off, then it goes back, turn to switch on and then off.

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So there’s a double action that’s taking place there.

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It creeps fairly slowly onto the switch, very slowly, creeps off the switch and you can see the light going off.

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Then it turns around and very, very slowly creeps back onto the switch and then very, very slowly creeps off the switch.

Transcript for Let’s Switch The Laser Machine On (Cont…)

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And at the moment, it creeps off the switch and a light goes out. That’s zero.

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So let’s watch that again. Now, I just pressed the reset button, which is going to reset zero. Creep onto the switch.

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Watch that off, on, off, and at the moment, it switches off.

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It knows where it’s zero is and it moves rapidly to a position of memory where it last was told to be.

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So the head stores its last position and goes to that last position.

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Let’s go and look at the controller and see what’s happening to the controller LED’s during this start up procedure.

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Now here’s the controller, the brain, and this is a 6442,

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which most people will have in their machine because this is a pretty standard Ruida controller for these sorts of machines.

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Your controller might be different. And so some of these instructions might be slightly wrong for your machine.

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But in principle, somehow the same sorts of things will happen with your specific controller.

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We’ve got a set of LEDs down here. You can see one of them is on solid and the other one is flashing at the moment.

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But there’s a whole row of 15 LEDs down here. Now, very confusingly, these legends here have got nothing to do with those LEDs at all.

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Those legends point to each one of these termination blocks.

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If you want to understand or work out what the LEDs are doing, you have to look down the center here, because down the center here,

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we’ve got a small table which explains what each one of these LED’s is doing. While the machine is turned on,

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and we just seen it set it’s zero zero position. I’m going to use my special switching mechanism.

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And we’re going to touch those two switches again. There’s the X switch,

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which I’m turning on and off, and there’s the Y switch which I’m turning on and off.

Transcript for Let’s Switch The Laser Machine On (Cont…)

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So I’m now turning the machine off.

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And everything’s gone dead. Number 15 LED at the top there basically tells you that there is power to this unit.

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So when I turn the machine on, you’ll see 15 come on. 14 will not be flashing.

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But what you will then see is two of these lights down at the bottom here, the two switch lights that I just demonstrated to you, will come on.

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There’s the Y-switch, there’s the X-switch.

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It’s now finding the zero zero position, it’s found zero zero position and it’s moved to its start position and it says flashing light.

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Now, most people consider that a red flashing light means something is not right.

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Well, in this case, I’m afraid it doesn’t mean that, it’s exactly the opposite.

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It means we’re all OK and we’re ready to start. I’ve now got my zero zero position and we’re fine.

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You notice that the two LED’s for the switches have disappeared. That’s it.

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They do not perform any other function other than setting zero zero. Even if I do this now.

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I’m not affecting anything. Those switches can switch on off as much as they like.

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We are now beyond the start up routine that’s built into this brain.

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We’re now going to take a look at the machine keyboard. There’s a big red button on the side here, which says reset.

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So when we press reset, here’s what happens.

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We’ve gone and we’ve reset zero zero again, you might ask the question, why would I want to do a reset? With these arrow buttons here,

Transcript for Let’s Switch The Laser Machine On (Cont…)

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I can manually drive the head around the machine.

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So what I’m going to do, I’m going to press one of these buttons now and I’m going to simulate something that might happen.

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So I’m going to drive the head towards my finger. OK, now that sounded pretty violent, as you can see, the head in the middle of the machine,

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we know that zero technically is over here when the head is over here.

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So let’s just have a look to see what position the machine thinks that head is in at the moment.

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Remember, this is a 500 millimetre machine. The brain thinks that it can move 500 millimetres this way.

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Now, at the moment, we’ve just seen that the head is at position zero in X. We know that this head is going to run out of its field of operation,

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so let’s make it run out of its operating field. Very slowly, we will creep up to the end of the stroke.

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Sounds terrible, doesn’t it? As I said, all that’s happening here is the stepper motor field is changing because it’s been told to step, step, step.

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It doesn’t know that the head is jammed because it’s still being issued counts, but the rotor is not rotating because the head is jammed.

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So you should be able to see that as well on the keyboard.

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As I press this button here, which is the right hand button, you can see that at the moment,

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it says it’s position 356. OK, the machine knows that it can travel to 500 and you can see the count going up,

Transcript for Let’s Switch The Laser Machine On (Cont…)

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the pulses are still being sent to the stepper motor. But the stepper motor is not moving, all you can hear is this horrible noise.

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But when we get to 500. Or in this case, I’ve got it set to 510.

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The machine says, ah, I know where I am now. So now it’ll drive all the way back to that switch. It says zero on the keypad.

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It’s gone back to where the zero position should actually be.

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Effectively, we’ve reset the zero. OK, but we’ve had to do that by running the machine out to the end of its count.

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Now, if you happen to hear at any stage a noise like that.

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Where it stops in the middle of a stroke, the first thing you should do is to press reset.

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And that would then go back and teach the machine where zero zero is and everything’s back and happy again.

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OK, so it’s important that you understand the mechanism by which all these bits and pieces work together.

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Now, the other one, the other reason why it’s important that you understand the relationship between these two switches and what

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they do and when they do it. Is because these are one of the most likely things on your machine to fail.

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This switch here is particularly vulnerable. This, switch is not vulnerable.

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Let me explain why. If we take a look at this switch here, you’ll see that it is a static switch, i.e., the cable does not move.

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Now, this switch here has got a cable that runs around the back there, down through this cable chain and then finishes up going back to the controller.

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This is part of a moving axis.

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The one over the other side is static.

Transcript for Let’s Switch The Laser Machine On (Cont…)

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And that means that the cables for this have to find their way back to the controller via this flexible link, this cable chain.

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Now, that means that that cable is continuously

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doing this. Flexing backwards and forwards. Now I want to give you a quick demonstration. Inside this cable,

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we’ve got some copper wire. Now, this is an exaggeration of the situation that exists. Now, you may think of copper as being a very, a very soft material.

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Now, what I’m going to do now is to bend this. And you’ll notice where it’s bent, right there.

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OK, I’m not going to straighten it out again, and bend it again and again.

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Now, can you see where it’s bending? It’s bending further and further away from where it did originally.

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The reason being, is because copper, when you bend it, goes hard and it gets harder and harder every time you bend it.

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Now, after a lot of flexing, this metal will break. It goes brittle and it breaks.

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Now, what that means is that inside your cable there, you’ve got a cable that may do this.

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Open, close, open, close, depending on how

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this is stretched. Depending on which cable is broken, it may well allow that the light to switch on and off,

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but not allow the signal to get to the brain or any combination of things in between.

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You can be confused by the light and the brain can be confused by not having a signal, even though you think it should have because of the light.

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That’s why I’m saying to you, you must look at the controller itself when you get a problem with your machine.

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And what you’ll find is that your machine, when you start it up, may or may not detect this switch properly.

Transcript for Let’s Switch The Laser Machine On (Cont…)

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It may or may not set zero properly. It may well make that horrible grinding noise that you heard.

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So when the machine doesn’t do what you expect it to do. Check this out.

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But as I demonstrated to you, all is not lost. Yes,

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you will need a new one of these, which doesn’t cost a fortune. They’re

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only somewhere in the region of five to ten dollars. And you can buy them off of eBay easily.

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You can carry on working with your machine. But instead of using this as zero, what you’ll have to do is what I showed you just now.

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You will run your machine to the end of its stroke and you hold it on there until your keyboard says 500 or 510 and this stops making a noise.

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Now, when this stops making a noise, you know that you’ve run this to its limit.

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You can then drive it back to the beginning because now that will be zero.

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So when it comes to replacing the switch, unfortunately, it’s not a quick fix.

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You can’t just splice a new switch into this existing cable because the problem is in the cable, remember?

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So what you’ve got to do is completely replace that switch and cable all the way back to the controller.

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What you’ll probably have to do is to just break the cable chain here, pop this cable chain apart, which it does, it unplugs.

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So you’ve got two separate pieces of cable chain temporarily, because it’s very difficult to get a piece of cable around this curve.

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But it’s very easy to get it into a flat piece of cable chain and then back

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along a flat piece of cable chain and then finally pop your chain back together again.

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I personally never had one of these fail in six years, but I’ve seen and spoken to many correspondents with this problem.

Transcript for Let’s Switch The Laser Machine On (Cont…)

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We’ve examined a couple of keyboard features like the reset,

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the switches that drive us backwards and forwards and left and right. This button in the middle called Z/U button.

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If we press that, it gives, it gives us access to another menu.

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Now, I’m not going to talk about those features on there very much at the moment.

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We can use, we can go backwards with the up arrow key and get to the bottom of the list.

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And we’ve got axis reset there. Let’s just have a look at that.

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What it does, that allows me when I press the reset button, it resets every axis if I want to reset for any reason,

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just one of the axis, I’ve got the ability here to just reset the zero on one of the axis.

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It’s not very useful, but you just need to be aware that there is a feature there.

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Escape. Now we step up, diagnosis it’s called. Enter.

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I’m now going to put my special piece of kit over one of the switches.

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Hang on. Look, what does it say. Y-limit switch and now go to the X.

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And I’ve got the X -limit switch, so we’ve got another mechanism on this machine for seeing

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how the switches are working? OK, so now we’re at my other machine and we turn this one on and we’ll see what happens. Hear

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the noise? That beep, beep, beep, beep, beep, beep is actually the water protect system because I haven’t got a reservoir and a pump on here.

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I’ve got an industrial chiller. So the audible warning tells me that I have got no flow.

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The fact that it’s gone quiet tells me that I’ve got flow. Now, something you might well have noticed while I was speaking.

Transcript for Let’s Switch The Laser Machine On (Cont…)

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This time, the head went to that corner, not the corner over there where you just see me going.

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So the datum on this machine is in the back right hand corner.

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The datum on the other machine is on the back left hand corner.

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I cannot say with certainty where your datum is.

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It depends on the machine manufacturer, where he decides to put the limit switches and how he, how he wants to set the machine up.

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But the position of the datum is important when we come to setting the programming system up and we’ll talk about the programming system in another session.

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Transcript for Let’s Switch The Laser Machine On