The Fiber Laser Learning Lab Series with Russ Sadler
In this Series, Lotus Laser have lent Russ a MOPA 20 watt fiber laser to “play with”. Although Russ has a moderate understanding of laser technology (his words) and how constant power glass tube systems work, pulsing fiber laser engraver machines are shrouded in a deeper mystery than the glass tube machines.
They have been designed for high speed marking and the technology has been well tried and proven. There are limited “tricks” that the pulsing laser technology can perform. You enter predefined parameters for each marking “trick” you wish the machine to deliver , then stand back in amazement. Most correspondents tell Russ that they have bought their machine direct from China and received a machine and EZCAD software, preloaded with a few default parameters. No other instructions beyond the EZCAD manual are forthcoming.
Russ states “I am neither a teacher or expert in this field so you join me in my learning adventure with the warning that I have a simple but inquisitive mind and will probably make mistakes on my way to discovering the truth. I WILL oversimplify and maybe distort the scientific detail in my quest to build a simple picture of why and how this technology works. I am not trying to reverse engineer anything, just to break through the seemingly impenetrable ‘techno cotton wool’ that surrounds this amazing piece of science.”
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Transcript for Fiber Laser Engraver: We are no longer Flying Blind
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0:00welcome to another fiber laser Learning lab
0:02today I’ve just been left in the
0:07sweet shop and I can have the pick of
0:09any sweets I like Wow well here we are
0:15we’ve pimped up my 40 year old
0:18stereomicroscope with a rather modern 41
0:22megapixel camera and they’re
0:25specifically designed for working on the
0:26eyepiece of a microscope and we’ve also
0:29put a nice LED lighting ring around it
0:32now the problem with the LED lighting
0:35ring is that of course it throws a light
0:36straight down now we’re looking for
0:39colors that are probably going to be
0:40seen from incident light and I don’t
0:43know how well this is going to work this
0:46is stage one and it does enable me to
0:49show you some of the things that I have
0:51seen so one of the first things I saw
0:54through here ever was these lines that
0:56I’ve edged onto this piece of stainless
0:59steel it’s a little bit out of focus at
1:01the moment and probably let’s put it
1:02back onto the center of the screen and
1:04one of the problems with this magic with
1:06this microscope is that first of all it
1:08isn’t mm super responsive it’s a little
1:13bit laggy and of course the focus that
1:19I’ve got on this stereoscope is not
1:21super fine it’s fairly coarse so let me
1:25just bring it into focus about there if
1:30I took a stick and dragged it through
1:33the sand I would finish up producing not
1:38only a groove but also a pile of sand on
1:42either side of my stick let’s remember
1:46that this groove that’s in here has been
1:49created with a laser beam a beam of
1:52light it has no solidity so how can it
1:55do that and force material out the side
1:58of the beam the only thing I can think
2:00of is that as it heats up and melts the
Transcript for Fiber Laser Engraver: We are no longer Flying Blind(Cont…)
2:04melt material is it’s actually boiling
2:07so hard that it actually bubbles out
2:10onto the sides and as it bubbles out
2:12onto the sides we’ve got this little
2:14raised section here this is the basis
2:16upon which I started to muse that we may
2:20well be able to put another line right
2:22beside it if if I was to work this way
2:25what I would do I’d be finishing it
2:27finish up with a series of these little
2:30ridges moving behind so I would finish
2:33up with something that looked a bit like
2:35a plowed field you know nice even ridges
2:39a pattern a uniform pattern all the way
2:41across the material now that was the
2:43basis upon which I started to consider
2:44this butterfly wing approach by which
2:47we’ve got a uniform pattern or regular
2:49pattern running across the surface that
2:52reflects the light both by a combination
2:54of thin film interference and if you’re
2:58like interference patterns between the
3:03thin film interference patterns so we
3:06produce these colors by a complex
3:08arrangement of physics now whether or
3:10not that actually happens we’re going to
3:14try and discover but that’s that’s the
3:16thought process behind how I think these
3:18colors actually come into existence
3:20because their colors that go beyond this
3:23flat surface thin film interference
3:25effect what happens when we start
3:28looking at some of these colored
3:29patterns that’s the thing that really
3:31interested me and to be honest when I
3:35started looking at some of them and
3:37let’s just pull one across for a minute
3:38now the problem that I’m having with
3:40this camera is that this is a sort of
3:45emerald green when you catch it in the
3:47right light we can’t see enough detail
3:50in here to see what’s going on with the
3:52surface texture this is the still and so
3:57you can see the steel is sort of gray
3:59this looks as though it might even be
4:01black but as I said it’s basically an
Transcript for Fiber Laser Engraver: We are no longer Flying Blind(Cont…)
4:05emerald green hue when you look at it in
4:08daylight so we get no idea what color is
4:14with this system so as I mentioned to
4:16you previously when I wanted to kit up
4:18to look at this we
4:20can’t do it with the standard
4:22stereomicroscope because there is just
4:25not enough magnification to see what’s
4:27going on down at the crystalline
4:29structure level on the surface of the
4:31material we’ve got probably around about
4:3340 maybe 45 magnification here and
4:37that’s about as much as we’ve got yeah I
4:40could spend time on the screen there
4:44setting the color balance up right but
4:47I’d have to do that every single time I
4:49switch the camera on I’ve been to visit
4:52a company down near Swindon they
4:54specialize in scientific microscopes now
4:57they’re not top of the range Zeiss or
5:00something like that microscopes they are
5:03basically from China but they have been
5:06specifically designed for a guy who
5:09understands scientific microscopes he
5:12has spent his life working with them I
5:15went down to visit the guy with one of
5:16the sample colour swatches he’s not an
5:19engineer he used to be a botanist so as
5:22soon as he he understood what I was
5:24trying to do which is the look for
5:25butterfly wing patterns he was
5:28absolutely in his element another guy in
5:30a sweet shop so he was able to
5:34completely out of this whole roomful of
5:37probably about four or five hundred
5:40different microscopes that he had there
5:42and he’s if you like demonstration
5:43laboratory he guided me towards
5:46something that I’ve got in the office
5:49we’re going to look at my even newer toy
5:52or big bag of sweets I’m such a happy
5:56guy so my other camera has got very good
6:01resolution and it’s K could take us a
Transcript for Fiber Laser Engraver: We are no longer Flying Blind(Cont…)
6:04good quality video the problem is
6:07without a brain it’s kind of
6:10faithfulness leaves a lot to be desired
6:13whereas this one has got some
6:15intelligence automatically built into it
6:17and when I went to see the guy at Brunel
6:20microscopes where I’d bought this from
6:22he demonstrated this and he demonstrated
6:24the sort of camera that I’ve got and
6:27there is no competition so despite the
6:31fact that this was painful
6:33I felt I had to have it to be able to
6:36show you guys what is actually happening
6:39under there now what I’m going to do for
6:42the last part of this is to look at some
6:44of the things that I’ve been talking
6:46about previously and said Wow look at
6:48this look at that sorry you can’t let me
6:51just zoom in on this a little bit
6:52several things about this camera it’s a
6:54lot it’s a lot Mysteria I don’t have to
6:56move the the sample around because on
6:58the side here this has got a proper
7:01microscope stage for moving backwards
7:04and forwards or left and right and I can
7:07do that down here so I get a nice steady
7:09movement under the camera the second
7:12thing it’s got it’s got a very very fine
7:14and calibrated focus so each one of
7:21these divisions on here is 2 microns so
7:24I can determine to the nearest micron
7:26the depth of focus and trust me when you
7:31get to high magnifications you can do
7:33some great vertical measurements with
7:35this system as I will demonstrate to you
7:37in a few moments now the other thing
7:40that it’s got this weird system at the
7:42back here now
7:44this is a normal halogen lamp in here
7:47because I mentioned to you before
7:49halogen lamp is a closed replication of
7:52sunlight there’s a wide spectral color
7:55range within the light whereas with LED
7:58lights it’s a very suppressed color
8:01range this light comes through here it
Transcript for Fiber Laser Engraver: We are no longer Flying Blind(Cont…)
8:04passes through some filters if I need
8:06them and then it goes down here and it
8:08appears through the lens down onto the
8:11surface that I’m looking at the problem
8:14that we have with the work that we’re
8:16going to be looking at is that we need
8:18probably incident light from the side
8:22because that’s how this phenomenon works
8:25in some instances I’m not sure it
8:28happens like that in every instance
8:29because some of these colors you could
8:31look at from all angles and they remain
8:34fairly stable but some of them you have
8:38to hold them just the right position to
8:40the light to see the color so in
8:43addition to this
8:44through the lens light which I can turn
8:48off or regulate up and down we’ve also
8:51got these separate LED side lights which
8:56allows us to put incident light onto the
9:00subject every possible combination that
9:02we need is built into this microscope I
9:05think we’ve got 50 times hundred times
9:11200 times and 400 magnification now I
9:19could have had 600 and a thousand but
9:22from the from the work that we did in
9:26his little experimental demonstration
9:28room it looks as though we don’t need to
9:30go more than 400 times because I will
9:33show you what 400 times looks like on
9:36the screen with some of these samples
9:37right so you’re know looking at the
9:39Canon software that’s available on my
9:42screen here let’s take a look at that
9:44green sample that we looked at before
9:46so there we go you can almost see the
9:50intelligence of the brain working there
9:54when it’s got just green on the screen
9:58it adopts a slightly different color to
Transcript for Fiber Laser Engraver: We are no longer Flying Blind(Cont…)
10:04when it’s got some other color on the
10:06screen to do comparison with but I don’t
10:08think got any doubt that that is a green
10:10an emerald e-type green and then we’ve
10:14got a pale blue here can’t make up his
10:17mind about that one can it and we turn
10:19the main light off I mean there’s the
10:23silver color of the stainless steel and
10:27we can see this yellow burning here and
10:32we can see the pale blue now sort of a
10:35gray slate blue which is approximately
10:37what I’m seeing here this one is more of
10:40a coppery color
10:47so that’s the main central light turned
10:51on and I don’t think there’s any doubt
10:53that you could say that we’ve got when
10:55we’ve got a full spectrum light and we
10:56can turn the side lights off now and you
11:00don’t even notice that the side lights
11:02have turned on or off so it does depend
11:06on the texture of the surface and the
11:09color that we’re producing as to whether
11:12or not side lighting is required
11:14incident lighting is required or not
11:16let’s take a look and see what it looks
11:18like at a hundred times we need to
11:21refocus again it’s got some interesting
11:26imperfections in the surface there let’s
11:30go to 200 times and how you were getting
11:34all sorts of very very small details
11:36coming in now will come into focus if
11:39you look particularly just there as I
11:41play with that look you can see in the
11:43bottom there’s a little there’s a little
11:45shadow here which comes in there to
11:48focus well that comes in and out of
11:51focus there at and let me tell you on
11:53the knob 41 microns and yet if I bring
11:58it up to the surface which is there
Transcript for Fiber Laser Engraver: We are no longer Flying Blind(Cont…)
12:05that’s 46 microns so there’s five micron
12:11difference in the depth between the top
12:15and the bottom of that pattern now that
12:18might sound just a number but I think
12:21that that number is very important to
12:24the effects that we’re going to find
12:26when we start looking at the texture of
12:28these surfaces so let’s go one
12:31amplification more which is to 400 and
12:34look now you can see as I fiddle around
12:37with the focus how certain parts of up
12:39are in focus and certain parts are out
12:43of focus to red bits on the top are the
12:47bits that are giving the coppery effect
12:49and there’s it mixing the bottom there
12:52with the yellow so it’s the mix of those
12:55two colors that look as though they’re
12:57producing our copper if
12:59so let me turn the side lights on and
13:03I’ll turn the lights off again no
13:09different
13:10I could also turn this main light off
13:14and put the side lights on now you can
13:18see that you know there isn’t the color
13:21spectrum available on that white light
13:24to give us the whole range that we’re
13:26looking for okay let’s take a look at
13:29that green what’s the difference between
13:31the copper and the green I wonder
13:34look at the texture difference it’s
13:36completely different texture what about
13:39the difference in the height between the
13:41blue and the green background let’s just
13:45have a look can I get anything they’re
13:49almost the same I don’t think there’s
13:51very much difference I’m trying to find
13:53a piece of clear
13:58maybe maybe here let’s have a look so
14:00what we can do here we’ll bring this
Transcript for Fiber Laser Engraver: We are no longer Flying Blind(Cont…)
14:03this black is obviously hiding down a
14:06crack somewhere
14:07we’ll get that little black mark there
14:09spot-on focus and we’re at about 85
14:14microns and let me see if I could focus
14:17up on some of the blue somewhere that’s
14:20about 83 at the most close to 84 so
14:27there’s only about a one or one 1/2
14:29micron difference in the texture on that
14:33surface now that’s the sort of thing
14:36that are convinced we’re going to be
14:37looking for to get different colors
14:40different types of texture on the
14:42surface now we can’t say in this light
14:45but just there the colors that I’ve been
14:47looking at are fairly why I call solid
14:50colors they’re not these speckly colors
14:53now when I look at this pattern here
14:56I’ve got several pinks and moves which
15:01are nice and and greens of pale blues
15:04which are nice and sparkly so let’s use
15:07this pinky color here to look at to
15:10start with
15:12get the idea now we’ve got a completely
15:14different surface texture completely
15:17let’s just look at the tops of the
15:19texture in fact what we’re doing at the
15:22moment we coming in at the bottom look
15:23at these because these little blue spots
15:25here then you’ll see that as I bring
15:27them into focus just about probably
15:32about there we are showing up as -6
15:39microns and now we’ll take it up to the
15:43top so we start looking at things like
15:50this yellow spot here as being on the
15:54top you can just see the tops coming in
15:59and that’s about minus 10 so that’s
Transcript for Fiber Laser Engraver: We are no longer Flying Blind (Cont…)
16:06about a 4 micron difference but that’s a
16:10completely different pattern for a
16:13different color if we change this back
16:15to 200 now we can probably get more of
16:18it in focus and I don’t think there’s
16:20any doubt you can see the underlying
16:21pink that’s in there the movi pink
16:24that’s halogen light directly on the
16:27surface and that’s white light from the
16:30side now the reason that they’re showing
16:32that pattern like that is because this
16:34white light is fairly concentrated at
16:38the blue end of the spectrum it’s not
16:41down at the red end of the spectrum
16:42whereas in fact the halogen light has
16:48got a much wider spectral range and
16:50we’re more likely to see what’s going on
16:53now the other thing that’s interesting
16:55apart from colors is as I said the
16:59amount of damage that we’re doing now
17:01there is one of my grid lines there’s
17:06the little pile of sand that I was
17:07telling you about that’s that’s piled up
17:10on either side of the groove and that is
17:12at a height of 62 microns let’s find out
17:18where the surface of the material is I
17:20would say the surface of the material
17:22focus is about
17:23they’re so 62 that ones 42 so that pile
17:33of sand on either side of the crew was
17:3420 microns tall okay so let’s now go
17:40down to the bottom of the groove and at
17:42the moment where as I said we’re reading
17:4442 let’s go down to the bottom of the
17:47groove and find out what depth the cut
17:50is look at it isn’t it amazing you can
17:54see every little ripple of the pulsing
17:58action does taking place 25 so that’s 15
Transcript for Fiber Laser Engraver: We are no longer Flying Blind (Cont…)
18:05that 17 microns deep that groove now how
18:10did that get 17 microns deep below the
18:13surface is it just the explosive energy
18:16with which the melting takes place
18:19because it’s cast it up onto the surface
18:22and it hasn’t run back so it must have
18:26cast it up onto the surface and
18:27instantly cools leaving that channel
18:31down in the middle I mean that’s
18:33fascinating isn’t it
18:34okay let’s just I’m loving this plane
18:37let’s just pop that off and pop that on
18:41just because I can and we can still see
18:45down into that groove from the reflected
18:47light it’s not quite as clear when we
18:50were messing around with the focus I
18:52generated this little pattern so that
18:54was with the focus on the surface and
18:57then we went point to five up point five
19:01point seven five and one millimeter we
19:04lifted the focus up by one millimeter
19:06above the surface and then we went all
19:08the way down to three four five six
19:19millimeters above the surface and at six
19:22millimeters above the surface you could
19:24begin to see there’s a change taking
19:26place here at just after five at five
19:28point two five five point five look
19:31we’ve got lines going along the side
19:36and then we’ve got this breakup okay as
19:44we’re running out of power this one has
19:46done at a different power where you can
19:51see much clearer what’s going on now you
19:54may remember when we talked about focus
19:56how I was trying to describe to how the
19:59focus was not that the beam diameter was
Transcript for Fiber Laser Engraver: We are no longer Flying Blind (Cont…)
20:02not going to change until we got to the
20:06very tip of the power of the beam I’ve
20:11used strange words there but I think my
20:13pictures really described what I’m
20:15talking about and if we look down here
20:17as we start raising the focus we still
20:20got power we’ve still got the same width
20:22beam we’re still doing the same amount
20:24of damage at two millimeters above the
20:26surface three millimeters above the
20:28surface okay we’re getting a slight
20:30change in the pattern now of the debris
20:33on the side of the groove four
20:35millimeters but we still got power there
20:38now we’ve got some color coming into the
20:40bottom of the groove now you’ll notice
20:41but now look at number five we’ve
20:44started to get a distinct thinning of
20:47the line itself and there we go look
20:52we’re now starting to lose power and
20:54lose line thickness now this is the
20:56effect that we achieved with the
20:59 co2 laser as we went faster and faster and
21:01faster we were painting with a thinner
21:03and thinner part of the Gaussian beam
21:08here we’ve got exactly the same effect
21:10but of course we’re not running faster
21:13and faster we’re running at the same
21:14speed what we’re doing is lifting the
21:16Gaussian beam up above the surface so
21:19the thinner and thinner power part of
21:22the beam is now taking over and we’re
21:24getting less and less power and now
21:27we’re just about to run out of power and
21:29now all you can see in the background is
21:32the ghosting effect of if you like the
21:35out-of-focus beam that was really there
21:38around the outside of this central core
21:40let’s just go and have a look at high
21:43magnification
21:47in that groove sounds I focus in on
21:50there I think you could see a lot of the
21:52tempering colors that we had seen
21:54earlier
21:55additionally there are some other colors
21:58in there like there’s a green in there
22:00which is not one of the natural
Transcript for Fiber Laser Engraver: We are no longer Flying Blind (Cont…)
22:01tempering colors so my shear material is
22:04obviously not flat because it’s going at
22:06a focus oh look at that when I change
22:09the focus I get the red and when I
22:13change the focus again the blue comes
22:15into focus so there’s different depths
22:18there along that colored line well I
22:22think we’re in no doubt now that we’re
22:24on the right track these colors come
22:26from surface textures and what we have
22:29to do is to develop the technique for
22:32finding the right texture for the right
22:33color now there won’t be a single answer
22:38to this question because some colored
22:40suspect colors as you’ve seen and some
22:43colors are solid colors so there’s going
22:46to be lots of different ranges of
22:48textures but the question is how can we
22:51define a range of settings for the
22:54machine to access these range of
22:57different colors and textures that’s a
23:01lot of work for the future but hey we’ve
23:04now got the tools to do the job
23:05I’m getting a bit over dosed on all this
23:07sugar and I’m a bit hyper so I think
23:10we’d better stop there now and I’ll come
23:12down to ground thanks for your time and
23:14I’ll catch up with you in the next
23:15session
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