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Welcome to another Lightblade learning Lab.
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Today, we’re going to carry on a bit with Parameters, but we’re actually not going to
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do any parameters today.
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We’re going to look at some problems that we shall have as we tackle some more parameters.
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Particularly associated with engraving.
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Now we have already touched on some of these little problems in the last session on cutting
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parameters.
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But I didn’t enlarge on them too much at that point in time because there is a great deal
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that I don’t know about engraving.
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And so what we are going to do today is some exploratory work, that is new to me and probably
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new for most people because I’ve not found anybody else doing this sort of work.
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It’s a bit; when I say controversial… it can’t be controversial because we shall either
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decide that it does, or that it doesn’t work.
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The controversial element of it will be the fact is that we’re probably going to do quite
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a lot of work with no air assist.
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(draws in breath) Ooh well we touched on this last time, and
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err we got some quite staggering results.
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Hopefully we shall find similar sorts of things today.
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I indicated to you right at the beginning of this series that I’m not a tutor, I’m not
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a teacher, I’m an engineer who enjoys discovering things and as I discover things, you will
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learn.
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Um, and hopefully these sorts of things will help you understand more about the machine
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and the way in which you can look at things in a slightly obtuse way, to try and get solutions
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to problems, because I suspect that most of you guys will be using this machine for real
Transcript of Laser Air Assist or Not (Cont…)
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jobs and real work – earning money.
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And you will want to be most efficient that you can be at the job job that you’re going
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to do, and some of this knowledge and background information will help you make decisions to
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improve your manufacturing process.
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Before we dive in, a couple of things, first of all – ooh that’s nice and warm now, that’s
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my cinnamon roll mmm that’s absolutely delicious.
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It’s quite cold out here today, now I want to just draw your attention to this little
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thing that I’m holding here.
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I’m not likely to lose it as you can see.
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It’s a keep things warm or a keep things cold cup.
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And it’s got my normal black coffee in it, but the interesting thing about it is, this
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is stainless steel, and it’s been powder coated and the powder coating has been removed by
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a machine just like this.
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So you’re dealing with something here, with this machine, which is capable of all sorts
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of good things.
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Now something else I would like you to look at, this is what I call my wall of wind.And
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I hope, that we will be using this with some success today.
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It may be a total failure, I’ve only just recently made it, so I’ve not even had a chance
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to test it.
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It works, I’ve got it on a variable voltage transformer so I can change the amount of
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blow in it by 50 %. Ok now, to start this session off what I’ve got, is I’ve got the
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steel plate on here, um for a good reason as you’ll see in a second.
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I’ve got the 2″ lens in here, so I’ll just set that to 5mm gap and I’m going to run
Transcript of Laser Air Assist or Not (Cont…)
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a very simple program.
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The first part of this exercise is some engraving, some scanning.
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Followed by some cutting.
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Now this is a very cheap hardboard, very soft, this is not MDF, this is nothing like that
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laser board that we used in the last session.
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So, what have we got here?
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Well, yes it’s cut.
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But two things I want you to note: first of all, this is a right mess…..
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I mean it’s full of dust, we can take some of the dust off, but we’ve still got all this
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brown haze around the outside.
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Now what is that brown haze?
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Where did it come from?
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Well the answer is pretty simple actually, see this much here?
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Well this muck here is sticky,
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It’s basically condensed residue of the smoke that was generated when this was burned.
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If you take a look at the cut around the edge, the cut is pretty clean.
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That’s because all the smoke and residue, went downwards and condensed here.
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But when we were doing engraving on the surface here, where did the smoke go?
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– UP
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and then immediately down again because the air assist was forcing it back onto the surface.
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So, hence the reason we’ve got all this brown muck here sitting around the outside of what
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should be a nice clean engraving.
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How are we going to deal with this problem?
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Well, to be honest, I can’t answer that question at the moment because I’m certainly no engraving
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expert, and that’s the whole point of today’s session.
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We’re gonna see how we can change from this, I was going to be a bit crude with my language,
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but I’m going to say with this “not very good” attempt.
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To something that hopefully gets better.
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Now we’ll carry on at the moment, using this fairly cheap um fibre board, this hardboard,
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because we’ve got some references.
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Before we put this away, which I’m going to get rid of this now, lets just remove this
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horrible debris off of here with some white vinegar.
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Oh dear, white vinegar usually does the trick.
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But if it fails, I’m afraid we’re going to have to go for something a little more aggressive.
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This is acetone.
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Again, just a tip more than anything else, A steel plate, and it doesn’t have to be a
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plate like I’ve got here, it could just be a flat steel plate.
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It can be very useful to you, because first of all, as you can see it’s very easy to clean.
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I mention about the steel plate being easy to clean, because as you can see, after a
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little while all this brown crud, we’ve collected on that plate, is going onto this surface
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here, and this is a lot more difficult to keep clean.
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And what happens is this stuff here, will burn when you run the laser beam across it,
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and it will produce fumes.
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Which will come back onto the back of your job.
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So this is actually, in some ways it’s great, and in some ways it’s nothing but a pain.
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It has it’s uses and one of the great uses for it is that it has got a lot of air flow
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through it.
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Now if we leave the machine here, we’ve just got a great big cupboard cavity and that’s
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where this fits in to.
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You can see the pattern of the grill underneath there and look you can see my hands shadow.
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Now in here we’ve got a big extract tube that’s sucking the air out from underneath this area
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here, so this is like a big Plenum chamber underneath here and it sucks all the air down
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into it and extracts it into this amazing Purex unit.
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NOw I’ve always been used to throwing my waste products down a duct and to the outside world.
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But of course I’m also throwing heat away, if there was any heat in this cold workshop.
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Um, whereas this is a recirculating system, not only is it a recirculating system it gives
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me environmental protection because not only is it filtering out smoke, it’s filtering
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out through an active charcoal filter all the poisonous fumes that are in the atmosphere.
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So I can do some plastic cutting on this machine that I wouldn’t normally recommend you do,
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but with a certain amount of caution and care, and I would probably ask you to go back to
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thinklaser or to Purex and ask their advice about the product that you are going to cut.
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You can have products that are dangerous to your health, but not dangerous to the machine.
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And there are other hazardous products that are hazardous to you and to the bare metal
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work and electronics in this machine.
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So, you need to be careful we talked about hazardous materials in a previous session.
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Now I’m just going to mention it again, because it’s a very important subject that you mustn’t
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overlook.
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Back to this honeycomb table, same material, same program, let’s take a look at what happens
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this time.
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Now because I’ve changed the table we shall need to reset the focus and I can do that
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either with the Z/U button or in this particular instance I’m just going to let it drop onto
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my step gauge.
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Like that, that’s a nice simple way of doing it.
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Now if you remember what we learned last time, this edge looks pretty black and also look…..
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It’s got a lot of soot on it, now that would indicate to me that we could go faster.
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Now I’m standing them up side by side so that you can take a look at them and you’ll see
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that the one that was done on the flat table is in fact cleaner than the one that’s done
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on the honeycomb Table.
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Strange that isn’t it?
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And the back looks nice and clean again, although I could make this run faster as we said, I’m
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not going to, we’ll keep all the parameters the same.
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The only thing that we are going to do is change the way in which we feed air to and
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from this product.
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So this is all about how air can affect the quality of your product, and air flow can
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affect the quality of your product.
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OK so now we’ve got the job sitting on stand-offs, so that there is an air gap underneath the
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product as well.
Transcript of Laser Air Assist or Not (Cont…)
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Now I’ve got the lid open at the moment, which is something that you won’t have, you’ll be
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running this with the lid down.
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How does this one compare?
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Well I would say that probably, on balance, it’s not quite as mucky, there isn’t quite
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as much haze there if you notice, but I can take it off just as I did on the first one,
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and to be honest, there isn’t a great deal of difference between these two.
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This one is a lot whiter, these are both darker.
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Now the next variable that we are going to introduce is this….. we’re going to turn
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the air assist off completely, now we’re in for some fun.
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Oh dear…. that’s lovely isn’t it.
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Now what is that flame coming out of the back there do you reckon?
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What do you think to that one?
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Let’s put in down against our first one, which is the best we’ve had so far.
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Hopefully I’m making a point here, the importance of air assist or no air assist.
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The debris that’s coming up with this one is not being blown back down onto the job,
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it’s being allowed to come up and blown away by the air that’s moving past here.
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Even though it’s not necessarily the best air flow that we can possibly get, it’s a
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gentle airflow.
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The interesting question is, look at the edge, you might be able to see how this has got
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a shiny edge around here where the debris has settled onto the surface and it’s produced
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this… .although it’s not, it is a little bit brown around here, it’s not terrible,
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but when you turn it into the light, you can see the silvery edge that’s around here, the
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shiny edge where the resin has settled back down again.
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Now when you look at this one, there’s nothing.
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Why is there nothing?
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Well the answer is….. we burnt it, you saw it burning.
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If it’s burnt it doesn’t settle back onto the job, so in some ways burning it is even
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better than trying to blow it away gently.
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This is a burning process, it is converting a piece of wood into gas and gas is a lot
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more volumetric than the wood and so consequently it’s expanding up and producing all this debris
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which is in the air.
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And that’s the fundamental problem that we’ve got with engraving of any organic material.
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We’re going to produce this smoke, and that’s what we’ve got to try deal with.
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Now there are several ways that we can deal with it, one of them is to put masking over
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the top of that, which would be fine for something like this and let me just demonstrate, and
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I’m not going to do the cut, I’m just going to do the engraving to demonstrate the point.
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Now I’m going to turn the air assist back on because you know what happens when we put
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air assist on, we get all this muck on the surface.
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So lets go back to muck on the surface mode.
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I’m going to cut that in half like that, and peel off this piece here.
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So we’ve got a nice clean product.
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Well, I say clean, but you’ll notice that this is dark and this is light, because even
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though we’ve got a nice clean edge around here, we still finished up painting the text
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with all our rubbish.
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So we didn’t get clean text, we got resin coated text.
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Which in some instances might look quite good.
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Ok so we’ve basically discovered that we do not want the debris to be blown down and the
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best thing that we can do is to have the air assist off.
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But if we have the air assist off and we’ve got a composite job, cutting and engraving,
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I mean this is easy to do for engraving because all we have to do is turn the air assist off.
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Ok so now I’m going to carry out a test and we’ll stop it after the engraving.
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You will notice how the smoke has been thrown in the air and is getting carried away.
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That is exactly what we want, we don’t want it to go back down onto the job.
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Now I am going to turn this around, so that we can see the difference, if there is a difference
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between working at the front of the machine and working at the back of the machine.
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To be honest, it doesn’t really look very much different.
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Which is good news, because all we need is a waft of air across it.
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Now just look how beautifully clean that is.
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And that’s no air assist, if you remember last time, when I say no air assist, you can
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hopefully see that there is a small amount of air leakage across the valve, which is
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actually just keeping the lens protected.
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But it’s not enough flow to interfere with what’s going on with the air flow down here.
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Now we’re back with our piece of trial material, and what we are going to do now is to see
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if we can get a compromise whereby we get a nice clean engraving but also a fairly good
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cut.
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Now we’ve already had that situation once, which was basically this one here which was
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no air assist, it was on this honeycomb and it was on stand-off.
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So, we’ve already got this test in the bag.
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So we don’t need to do that again, we need something different.
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Now i’m going to lift this probe, right up out of the way, so that it’s not in the line
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of fire, if we get fire, because we’ve already got some sticky residue on here from the comet
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trail.
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Now this is where I want to play with my experimental “Wall of Wind” I want to see if I can introduce
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quite a high speed cross flow that will keep the flame extinguished and blow the debris
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away, I’ve put the voltage on this up to full volts “24 volts” and if we take a look, as
Transcript of Laser Air Assist or Not (Cont…)
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you’ll see, we’ve got a fair old wind blowing across there, so if you’re going to blow anything
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away, this is how we’re going to do it.
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So what we’re attempting to do here, those flames are caused by residues that are lifted
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out of this material and they are flammable residues that are being, they are being ignited
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by the laser beam itself, because we’ve got a very high power laser beam on there at the
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moment.
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And what the attempt will be to do here is to dilute those fumes to such an extent that
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they do not ignite.
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And nothing there, and well I think we’re getting a much smaller flame trail.
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And in fact it’s a very clean … we can go faster, but that’s a secondary issue.
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Ok well that was fairly successful, um the flame trail was very much reduced, but what
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I’m doing at the moment is forcing the air across the surface.
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Now maybe I can achieve the same result by blocking off the honeycomb table, because
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at the moment the honeycomb table is compromising our flow.
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We’ve got the cover going down, which is the way that you would have to operate this machine,
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and so now if you remember, I’ve got a 1/2″ air gap underneath the front of this machine
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here.
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I’ve put some fairly thick rubber feet under the end here, so I’ve got a nice air gap under
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here, which is blowing in and allowing a large amount of air, relatively speaking to flow
Transcript of Laser Air Assist or Not (Cont…)
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in and blow across the job.
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At the back of the machine, you can see these holes, this is where the only air is going
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down into the table beneath.
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There is a small amount of leakage around the edge of the table here , but most of the
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air is being drawn in and across the machine and going down through those holes at the
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back there.
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So what we’ve done, we’ve introduced basically a cross flow of air, both beneath and above
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the work.
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Lets see what the results are like compared to my “Wall of Wind”?
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Basically a very large comet tail.
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Now the end result compares well with our “Wall of Wind”.
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Here are our 3 no air assist samples, we’ve got the one with the big comet tail, and maybe
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it is sort of um, Just very slightly hazy in this area.
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This one is perfectly clean, this had big comet tails on it as well.
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This was the wall of wind, and that looks quite nice, but no significant difference
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between that and this.
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Except the flame, now as I said to you, you Shouldn’t really be worried about the flame,
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providing you are with the machine and there is nothing around here which is going to suffer
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from being heated, then that trail of flame is actually doing the best thing it possibly
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can do, which is burn up all the debris.
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So it never settles back on your job, now I did say that this was going to be slightly
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controversial and I’m sure Thinklaser wouldn’t want you to run your machine with a comet
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tail.
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So we’re going to have to find another way of doing it.
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Well I did say what we’re going to do next, you will not be allowed to do half of the
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things I’m able to do, so I’ve just had a bit of a think and a bit of a brain wave,
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and I’m wondering whether an adaption that I’ve made to the head will actually work.
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So I’ve turned the air assist back on, but as you can see the air assist is not exactly
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going where it went originally.
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Let’s press the button and see what happens….
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Well so far, so good.
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Well we still have a flame, but of course now it’s not doing any damage.
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Ok so that was a bit of a failure wasn’t it, um, the results were quite good, but then
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again as we’ve seen before anything with a fiery tail produces quite good results.
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Um not necessarily good for the machine as I said.
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It will certainly be frowned upon by everybody, including Thinklaser.
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You see, what was the thinking behind what I was trying to do.
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Well it was a small shroud that i put around the nozzle and on one side of the shroud I
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drilled a big hole like that, and on the other side of the shroud I put in a tube, like this,
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for my air assist and the idea was that the air assist was going to go out here and as
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it went out here with a sort of a Venturi effect it was going to draw air out from the
Transcript of Laser Air Assist or Not (Cont…)
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inside and hopefully produce a swirling effect as it did so.
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In other words, I was producing a sort of a Whirlwind inside that enclosure, the attempt
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was to try and draw air up and in, and produce a negative pressure inside there to pull the
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fumes up and throw them out the side.
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Rather than try and eject them up through like a vacuum tube or a vacuum cleaner that
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would need an external source I had hoped to use the positive pressure of this air assist
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to produce a sort of vacuum.
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Well, thinking about it, it’s got to be a hell of a vacuum, a hell of a suck to take
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away the fumes and prevent burning.
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Maybe upon reflection, not my brightest idea today.
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Now apart from a little bit of collateral damage here, which a little bit of acetone
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will very quickly cure, um no parts of this machine were harmed in the making of this
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video.
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Now as they say on kids programs, “Please don’t do this at home” and in a strange sort
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of way, I’ve got to say the same sort of thing.
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I’ve mentioned it before, I can do things with this machine that you will not be allowed
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to do because you won’t be able to get into this machine to use it in the way that I am.
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And I wouldn’t want you to do some of the things that I am doing today.
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I’m doing them so that you don’t have to, if you’ve got an inquisitive mind then hopefully
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I’m there before you and I will take away the need for you to do some of the things
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I’ve done today.
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But the fundamental lesson is, that we need full air assist when we’re doing cutting,
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otherwise we shall get comet trails and fire extinguishers at the ready.
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We need zero air assist for clean engraving, now that is totally contrary to most advice
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that you will get and you certainly won’t find anything about this information when
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it comes to parameters.
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So I’ve dealt with this as a separate issue outside the parameters because I don’t really
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want to go back and explain why I’m using zero air assist when we talk about engraving
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parameters.
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It’s a big enough subject all on it’s own as you’ve seen.
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Now I must hastily add quickly this applies to organic materials, acrylic is a special
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subject all on it’s own and it deserves a full session talking about cutting and maybe
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a full session talking about engraving acrylic because it is a very very interesting material.
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Thank you very much for your time and attention today and I hope you’ve enjoyed some of the
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fireworks.
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Fire extinguishers away now, and relax.
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See you next time.
