12 – The Search for Colour Part 3 (41:12)

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 marking machines are shrouded in a deeper mystery than the glass tube machines. In this session, Russ looks at the effect machine parameters have on the color from a fiber laser.

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.”

Contents

In this video, Russ takes a stable color he generated during previous tests and investigates how changes to machine parameters will affect the colour. His goal is to find a predictable and reliable method to instigate changes to the color from a fiber laser.

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Color from a fiber laser - the base color
Color From A Fiber Laser – The Base Color

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Transcript for The Search for Colour

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0:00welcome to another fiber laser learning lab today we’re going to go on with our

0:06hunt for colors now in an earlier session we managed to eventually get to

0:13producing quite a few reasonable colors on this color swatch as you can see most

0:19of these colors are a bit fickle in that you know you have to look at them in certain types of light but there are one

0:25or two like these here which remain pretty stable regardless of how you look

0:31at them and what I’m going to do I’m going to use this color here as a starting reference for today’s session

0:38we’re going to make that the standard color and I’m going to vary the Machine

0:43parameters and see how we affect this color with various machine settings

0:50because I want to find out if we can control the surface in some way predictably if it is a pattern of

0:58surface disruption I’m fairly confident there will be various ways in which we

1:03can get to that disruption by playing with certain parameters so on this

1:09swatch I’ve got six columns and ten rows so I can get up to sixty tests on each

1:18one of my swatches so I’m going to be using the parameters from that maroon

1:23test and I’m going to start off each one of my tests either at or close to that

1:31parameter and then we’re going to change the parameter first of all I’m going to change the power then I’m going to

1:38change the pitch between the line spacing at the moment we’re still staying with a very simple horizontal

1:44line spacing there are many other combinations of line hatching that I can

1:50use I can use double hatching cross-hatching 45 degrees I’m going to keep it very simple at the moment and

1:56just hunt in this one simple straightforward area leaving the pulse width the same I’m going to be changing

2:02the frequency because I think that as I stay with the pulse width and reduce the frequency I should also be able to

Transcript for The Search for Color from a Fiber Laser. (Cont..)

2:08reduce the power in the post itself although I’m going to stay with the lines

2:13of 0.0 0.1 micron I’m going to then be changing the spacing horizontally

2:20between the pulses I’m then going to be changing over a frequency of 500 kilohertz which is generating peak power

2:28for a four nano second pulse and I’m going to drop that down to 300 which

2:33means I’m going to reduce the power of that pulse and in addition I’m then going to run down the speed range so we

2:39shall have a direct comparison between two sets of results for different power

2:45into the pulses the plan for these first two columns changed when I was in the

2:51workshop and what I’ve done column a and column B are exactly the same the only

2:58difference between them is the way in which the scanning was done the first section was done in the way that I’ve

3:05normally been doing the scanning which is starting from the bottom going backwards scan so it’s unilateral scan

3:13so I’ve arranged the scan pattern beside it in column two to be bi-directional

3:20scanning like this because I wondered whether there would be any difference to the heating effect or the way in which

3:27the surface was damaged by virtue of the scanning pattern these were 16% power

3:32these were 18 percent power this was 20 percent power which is our reference

3:37here and there’s virtually no difference between them if I turn these very slightly to the light you would get the

3:45this and this will be exactly the same color it just depends on how the light catches them so in essence there is no

3:53difference between the scanning modes for these first two columns and then we’ve got 80% and a hundred percent now

4:01there’s a large change of color down that column and that’s all due to the

Transcript for The Search for Color from a Fiber Laser. (Cont..)

4:07percentage power that we’re putting into the pulse these first five results here

4:13in columns see all the parameters the same as these first two columns except what we’ve done now this first result

4:20here is at 100 kilohertz then we’ve got to 200 kilohertz 400

4:28kilohertz 600 kilohertz and 800 kilohertz now as you can see as we get around

4:36about the 500 kilohertz which is where we should be for post maximum pulse

4:42power we should actually have to this result here just here but either side of

4:48it look we’ve gone for gold it’s very very sensitive to the kilohertz now these bottom five results here are

4:55all to do with the stepping intrument increment this one is half a micron

5:00which is half what we’ve used when we used these and it seems to make no difference at all this one has gone to

5:08two microns which is missing this one out which should be just here so that’s

5:13two microns three microns four microns and five microns so it’s fairly sensitive at this very low power to the

5:21step increment so here we’ve got our standard setting nice dark maroon and

5:27that that was with a point five focus which is on the surface of the material then we go to point six point seven

5:34point eight point nine and one millimeter so at one millimetre we still

5:40haven’t changed the color at all now we’re talking about one point five millimeters we’re now losing power in

5:47the beam now two millimetres two and a half and three millimeters so focus in

5:54this instance has a dramatic effect when it runs out of its power but we know

5:59that from previous focus test work that the power in the centre of the beam

Transcript for The Search for Color from a Fiber Laser. (Cont..)

6:05drops off fairly quickly when we get to longer pulses this pattern would extend

6:11right the way down but if we had longer pulses are done it would you’ll get colors but we shall experiment with that

6:17later on now these last two columns here are rather interesting because they’re

6:23both change of speed this one is a thousand this one is a thousand as well

6:29the difference between them is that this was done at the correct kilohertz 500

6:35kilohertz and this one is done at 400 kilohertz so

6:41we’re really very fine to a certain extent what we found out in column C so as we scan down this column here we’re

6:47talking about a thousand millimeters a second 900 800 700 600 500 400 300 200

7:00and 100 millimeters a second now gain when we look down this column we go from pale blue to purple

7:11so speed has quite a significant effect on the color result now he was our

7:18standard if we if we were to go to the lower power region above here we would

7:28get these colors as well of gold’s so the golds exist just above this mode

7:34there are at least two different ways that we can get to this gold color with

7:39very low power one of them is here by making sure that we don’t put enough power into the posts by suppressing the

7:46kilohertz we’ve also got it here when we drop off the end of the focus range

7:55we’ve proved that we’ve got it here because we were messing around with the kilohertz in this one and here when we

8:02drop off to very low power because we this is the percent power range and here we are at 18% just below this one and

Transcript for The Search for Color from a Fiber Laser. (Cont..)

8:10we’ve got gold again so there are several factors that allow us to get gold there aren’t too many factors that

8:19allow us to get green and blue but the fact that we get green and blue up at the higher power end of the range is a

8:27good indication of where we should go next to look for our next set of colors now much as I’d like to go and play with

8:36my new toy and study the surfaces of the colors that we’ve produced I think

8:43that’s a little bit premature because I think I’m more curious about something else that’s popped out of these results

8:50now bearing in mind what we’ve just said about these Gold’s here in particular what we’ve got is the standard colors

8:56here at a3 and b3 and also at e3 so

9:04these are all the same parameter but we’ve also got one which matches here at

9:11f8 now what’s the commonality between

9:16these two or these three sets of results so I said about trying to work out what

9:23might be a common feature because if I could find a common feature here maybe we could find parameters which would

9:30match this common feature but not be the same parameters as we’ve got here let me

9:37just explain for a moment now how pattern is made up of two main features

9:43first of all the kilohertz which is pulsing away at a steady rate all the

9:48time 10 kilohertz and if we change the

9:53speed across here then we should be changing the rate at which those pulses

9:59are being put down okay the slower that we run the more pulses which we’ll get

Transcript for The Search for Color from a Fiber Laser. (Cont..)

10:05per millimeter and the faster we run the less pulses which we’ll get per millimeter so we have got control of the

10:12number of pulses per millimeter with the speed as we’ve seen on this swatch here

10:18speed changes from ov to a sort of a a dark see green here the next thing that

10:24we have to look at is the number of

10:30lines in this direction which is basically the pitch per line because

10:36this also affects the density of the pattern if we finish up with a thousand

10:43pulses per millimeter across this way we could also set the pitch this way to one

10:50micron which means we shall have thousand this way and a thousand this

10:55way so that means within a square millimeter we shall have a million pulses

11:02so my question is provided we’ve got all the other features constant like the frequency the pulse width the power if

11:11we keep all those constant we only change these two features can we fiddle with these two features and keep the

11:17same color are we doing the same amount of damage to the surface by fiddling

11:24with these two features well that definitely didn’t play out as I expected

11:31at the top here we’ve got 100 millimeters a second then we’ve got 200

11:39millimeters a second 500 millimeters a second then the standard 800 millimeters

11:47a second then a thousand millimeters a second 1200 1500 1800 and 2000 and that

12:01little odd one there was I thought I just have a little Joker in here 500

Transcript for The Search for Color from a Fiber Laser. (Cont..)

12:07millimeters a second with a 1.6 micron spacing this one was still at 1.6 micron

12:15spacing but it was done at 800 millimeters a second this was 800

12:21millimeters a second as well but this time we changed the spacing from 1.6 microns to 1 micron go figure look at

12:30that little cluster there so I think we can probably see amongst this lot that speed ie

12:36horizontal dots is much more important than vertical dots

12:41I mean bear in mind these were all done with 20% power as well to match this

12:47here which is our standard and look we’ve gone from green to blue to maroon

12:53here we’ve got an orange and a yellow got a gold yellow here and then we’re disappearing to nothing down here so

12:59that didn’t go as expected did it got a think more now what is it that’s really

13:05causing this surface to change so this is now becoming a bit of a detective

13:11story and I think it might be Sherlock Holmes or Doyle that said something like when

13:18you’ve discounted all that’s impossible whatever remains however improbable must

13:24be the truth I think I might have got some of that wrong that’s the essence of the quote and in this instance none of

13:32our information here seems to make any sense we’ve shown clearly that pulses per square area is not the solution but

13:39somewhere buried in this table is the answer to our question it probably isn’t the vertical pitch it’s more likely to

13:48be this thing here which is speed because we have clearly seen that speed has a significant effect on color but

13:55why the only thing left is this thing here the on/off ratio so for four

Transcript for The Search for Color from a Fiber Laser. (Cont..)

14:04nanoseconds the ratio of on/off is roughly give or take the odd one or two

14:10here one to five hundred in other words we get one pulse and five hundred times

14:17that pulse length off so we get a tremendous amount of time to cool and not very much time to heat now how does

14:25that play into the speed equation well it’s pretty simple when you look at it

14:32and you think about it now having been pointed towards it at the high speed where we’re getting very little marking

14:39what we’re finding is we’re getting 250 heating pulses per millimeter and yet

14:48when we go to the top of the scale up here at a hundred millimeters a second we’re getting 5,000 heating pulses per

14:57millimeter we’re getting a lot more heating per millimeter when we run slowly even though we’ve got the same

15:04ratio of heating to cooling we’re putting more heat into the same area so

15:09therefore we’re going to do more damage at slow speed than we are a high speed

15:14because our pulse rate which is 500 kilohertz does not change the only thing that changes is the faster we run the

15:21more we spread the dots out and the less the heating effect so that accounts for

15:27why we’re getting a significant change of color because of the speed well we

15:33got there eventually what does it mean for us now how can we use it well you’re thinking where I’m gonna go from here

15:39I’ve had to just stop and stand back from the problem because one of the fundamental issues with this whole color

15:47thing is us an our perception of color

15:53now I’ve got some examples here that I want to show you under the microscope

15:58now look very clearly they’re not a perfect match but I think you could see

Transcript for The Search for Color from a Fiber Laser. (Cont..)

16:05that they’re both what you were considered to be move pink maybe for

16:11some people who knows what people see those colors is I see that as a slightly

16:16darker mode or dark pink it’s descriptive there’s no such thing as a

16:23color it’s what we imagined so let’s take a look first this piece of paper

16:29here which is plainly one of those people colors that I was describing earlier where we’ve got white light

16:35shining on it but you can’t see the white light all you can see is the reflected light that comes back which

16:42appears to be pinky move so let’s take a look at this under the microscope and as

16:47I bring this into focus you can clearly see that it’s a mode of color the more I get it into focus the more you realize

16:54that it’s not actually that move wait we’ve got some white which is obviously

17:00reflections off of the fibers I suspect rather than real white and then but

17:06we’ve got this general white background with a sort of up pinky hue to it it’s certainly yeah it’s got the same sort of

17:12shading as that but it’s certainly not dense like that color let’s zoom right

17:19in on the surface because that’s what we’re doing with this color swatch of mine we’ve got one five there although

17:24we’ve got moved around the outside of the fibre look what we’ve got in the center of the fiber there in various

17:30places we’ve got our thin film interference effect we’ve got the soap bubble the oil film effect okay so

17:37that’s not quite as pure as it looks I wonder what this one looks like we’ve

17:45seen this picture before on some of my surfaces it’s got up pinkie hue to it

17:52but it’s nowhere near as distinctive as some of the color that was in here let’s

17:57zoom in on that and see what it looks like well how did you can see there’s lots of depth to the surface on there

Transcript for The Search for Color from a Fiber Laser. (Cont..)

18:03but there’s no distinct move color not like we’re seeing with the naked eye

18:10sort of a bluey move it’s not that color what I’m really saying is what we see is

18:16not necessarily what’s on the surface what we’re picking up is a mixture of

18:23reflections of light in the same way that your RGB screen mixes light red

18:30green and blue to produce all of these different colors so light is a very

18:35funny thing let me just give you one more example let’s just take a look at this little business card and on here

18:41look we’ve got a perfect sky blue it’s a lovely pure blue let’s take a look at

18:47this at low magnification did you see any pink in that blue did you see any

18:52green in that blue that’s what this appears to tell us let’s look at it at

18:58high magnification so we’ve got reds greens dark blues yellow so my point

19:05really is your eye is very good at average anat see the absolute detail in

19:12a picture or color that’s how we get away we’d either in a picture which gives us the impression of a grayscale

19:18picture but it’s not it’s a series of black and white dots but somehow our brain patches all the dots together to

19:25make this wonderful grayscale image so now we’re talking about the same sort of

19:31thing but with color so does that mean to say I’m really chasing fairy dust

19:37here I’m trying to find some common factors which will allow me to predict

19:44what the color we see might be but I think the effects are going on at such a

19:51small microscopic level that I shall never be able to actually predict them it will always be

19:57a bit of an empirical assessment but it’s not going to stop me trying we’re

Transcript for The Search for Color from a Fiber Laser. (Cont..)

20:03going to still push on and see if we can get any sort of correlation between the parameters that we use for modifying the

20:10surface and I think the more I look at this the more I think that we’re only going to be messing around mainly with

20:17this surface film the thin film interference effects okay so having decided that you might be

20:24colorblind and I might be stupid for pursuing this rather endless venture

20:29we’ve got to go somewhere so knowing that we get the maximum number of pulses out of a speed of a hundred millimetres

20:36a second we’re still going to keep the power at twenty percent and we’re still going to stay with our four nanosecond

20:42pulse with 500 kilohertz to keep maximum pulse power even though we’ve actually dropped the power to twenty percent now

20:48what we plan to do now is to start off with 0.06 60 microns pitch between the

20:56lines and then drop it down 50 40 30 all the way down to two microns now most of

21:02the test work that we’ve done so far has been around about one micron because we found that that is that gives reasonably

21:09good colors so we’re going to run down and the reason why I’m going to run down is because okay can I get color in a

21:15line or is the color the result of overlapping lines which gives the

21:22impression that we might get color down here and maybe not get much color up

21:27here although logically on the basis of what we’ve said we should get color in a line

21:33okay now while I was at the Machine I did several tests the first test that I

21:39did was line a and as you can see the first line there is pretty weak and

21:44pathetic until it gets down to number 5 a 5 and then we’ve got when I classed as

21:51the standard color which is this one here which was done at 8 microns okay

21:58that’s one that we’ve seen before it was a dark I’d call it C green almost

Transcript for The Search for Color from a Fiber Laser. (Cont..)

22:03gray and then below there we’ve got nothing but really black now upon completing

22:11line a I brought them in to examine them under the microscope now this is low

22:18magnification and what I’ve done in addition to having the pattern just

22:24above the pattern I’ve now added a single line so that I can see what a

22:30single line looks like before it starts building up into multiple lines on the

22:35pattern now hang on that’s a single line

22:41these are 0.06 apart one beam width now

22:49they’re not touching just the little high-power tip of the beam is touching just there so they’re not joining up in

22:57any way shape or form so my first reaction was hang on these are not going to be valid results because we’re not

23:04getting the correct focus on the job so what I did I went back and I’ve dropped

23:10the focus down into the material by half a millimeter now look at all this color that we’ve got here

23:15that’s nothing to do with any engraved patch that I’ve done that’s the background that’s just the stainless

23:22steel what I’m going to do is just clean that now that was nothing more than a

23:29film of some sort of debris whether it’s a very very fine oil film or whatever it

23:34was on the surface of the stainless steel that just shows you how sensitive this whole process is okay so there’s my

23:41single test line and you can see that it’s not exactly consistent okay at the

23:47moment they’re nowhere near overlapping 0.06 so they’ve still got a big gap between them now I could drop the focus

23:54a bit more it’s already half a millimeter lower than the than the Lotus laser focus point well here we are at

24:00point zero three 30 micron and the lines are just about beginning to touch we’ve

Transcript for The Search for Color from a Fiber Laser. (Cont..)

24:08still got the high-power down the center but the lower power outsides are more or

24:13less touching so let’s go now to let’s go to 20 microns aha

24:22now we’re getting a little bit more color into it to the naked eye this is a sort of a gold color and yeah I think

24:31you could see that from the screen that that might come out as gold and the point I really wanted to make him look

24:37at here was to see whether or not my line was gold and whether I’m really

24:42producing gold lines or whether in fact I’m producing an interference effect of

24:48some sort because of the lines beginning to touch now so the lines are now touching when

24:55they weren’t touching we had virtually nothing so it would appear that touching

25:00lines in some way shape or form are essential that’s fundamental lesson

25:05number one I mean the color is not going to appear on a single line it is the as

25:11we anticipated with the butterfly wing effect that when we’re producing these if you like plowed field effect of lines

25:18behind lines we get some sort of color effect now here we are at ten microns

25:25and as you can see the line individual line thickness has not changed at all the light is reflecting off these

25:31overlapping lines in a completely different way now the question is can

25:36you guess from this image what color we’re going to see remember the blue

25:42card is it’s going to be a green is it going to be a pink is it going to be a

25:48blue well the answer is it is going to be a very very dark move but I mean

25:54let’s just zoom in on that I mean look what we’ve got there we’ve got orange we’ve got bright pink sort of them we’ve

26:02got moves we’ve got a lot of teal blue the sort of colors you might see on up

Transcript for The Search for Color from a Fiber Laser. (Cont..)

26:07on a peacocks tail you might just be

26:14able to see that that’s basically a very dark purple and the one underneath of it

26:21which is just dropped down by two microns

26:28is our very very dark see green let’s go

26:34and have a look at the hand of the microscope I think you would probably think that you could see green in there but you

26:41certainly can’t see any light green it is an almost a black when you look at it

26:46in daylight and there is no hint of any green in our single line along the top

26:52there again the same line combined at different spacing as producing these

26:57different effects so it must be a surface texture or thickening of the film between the lines that’s causing

27:04this problem because we’re running our constant speed now now this one doesn’t

27:11look a lot different to the previous one but in reality visually this looks like

27:18it’s black now this line at the top here has no spacing element to it at all so

27:25it cannot be affected by the parameters that we are setting for this so that’s why I’ve drawn that line there because

27:31that gives us a constant view of what’s happening we’re not changing anything except the spacing between the lines and

27:38we’re getting these strange effects the power is the same the frequency is the same that pulse is the same their focus

27:46is the same the only thing that’s changing is the line spacing and we’re getting all these strange effects but it

27:52does just show you how sensitive this whole process is because all we’re doing

27:57is rearranging a few of the molecules on that in it within that thin film

Transcript for The Search for Color from a Fiber Laser. (Cont..)

28:03stirring them up and making some come to the surface maybe some a few nanometers

28:10yet we’re making some of those and so we’re just changing the thin film thickness in certain areas because

28:18that’s why we’re getting different colors they can’t all be we’re not putting a uniform heat across the whole

28:24area we’re getting this very speckled effect because the thin film is varying in thickness and creating these colors

28:34well we’re going to run into this final section with a bit of a look at an idea

28:40of our head now first of all I’d like you to just note the grid on here and

28:46you’ll note that it’s a sort of a Goldy yellow just make a no that because we’re going to talk about that later but

28:52columns C and D and what we’re going to be looking at at the moment now there’s just about some sort of marks in C as

28:59you can see and you can also see the scratches on the surface in this site the d1 which is this top one was our

29:06supposed reference and it’s catch it in the right light and it’s a sort of a you

29:12can just see that it’s got a C greeny little green hue to it the one

29:17underneath there is definitely a copper color but the one underneath that is quite interesting first of all I think

29:23you can probably see that there looks as though there’s some depth to it as I move this in the light at the top you

29:29can see this one here which as I said it’s it’s probably it’s supposed to be a

29:35sort of a in certain lights it looks brown but you catch it in other lights look and it’s very definitely a movi red

29:44golds these colors here look at this lovely pale green but it’s only pale

29:51green and the one above it move in certain lights okay and that one at the bottom there is definitely sort of a

29:57dark green so column C was here where we

Transcript for The Search for Color from a Fiber Laser. (Cont..)

30:03kept everything constant except we changed the pitch between the lines in the vertical direction and it looked as

30:11though it was the overlap between the lines that was causing our patterns I say looked because that was the evidence

30:18that we saw at that point in time we’re going to go and look a little bit further at that in a few moments the

30:23other thing that we’re comparing is column D and in column D I went a bit

30:29bonkers because I wanted to look at a further relationship between this X and this y but maybe I was missing something

30:37out and the big something that I was missing out was percent power when I

30:43take the pulses per square millimeter which is what we were calculating here and multiply it by the percent

30:50power perhaps there’s a relationship that will appear then so let’s have a

30:56quick look at the calculations for that so here was column C so we’re not done I’ve taken the pulses per square

31:03millimeter and we’ve multiplied each one of those by 20 percent and we’ve come up

31:09with what I’ve classified as power density now I’ve made a big assumption

31:14here that the 20 percent power and the 80 percent power are a linear proportion

31:20across the range that is probably not true but it’s the best guess that I can make so where we had constant power we

31:31were generating numbers here for various colors so look faint gold 50,000 see

31:38green that color we had right at the bottom that I pointed out to you at the top of another column so see green was

31:45roughly 125,000 well there it is there here it looks like it’s called blue but

31:51in fact it’s the same it is the same number so you mustn’t be surprised that they come out as the same but here we’ve

31:59got this one at the bottom which we

Transcript for The Search for Color from a Fiber Laser. (Cont..)

32:05called very dark move catch it in the right light and maybe just maybe it’s

32:12the same as this blue or dark see green so there’s some sort of relationship

32:20there maybe hmm but then we come to this

32:25pink here which is a say pink it’s a sort of a fuchsia recolor 833 fuchsia here 75 there in the right

32:35sort of ballpark for the same sort of color do we have anything else here a hundred thousand for a fuchsia reread

32:41there hundred seventy-five eighty three they’re a long way apart so I don’t

32:48think we can claim any good relationship there the one thing we can say is we get very poor results when we get very low

32:55numbers look 3718 33:25 2016 all of these are very poor

33:04results so there’s some sort of very crude relationship but but to be honest

33:10I’m not sure that it’s good enough to use for predicting the colors that we’re

33:15going to get so I don’t think there’s enough correlation there to be X to get excited about now there are a couple of

33:22things that I want to finish off on these are interesting and they just basically round off what we’ve been

33:28seeing today so what you’re looking at there is one of the grid lines on my swatch plate that is through the lens

33:35like from straight above so as I turn down the central light that’s in the

33:41coming through the lens and let the side light begin to take over you can begin

33:47to see what’s actually going on there I could turn that I could turn that right down now so you’ve basically got almost

33:53just side light illuminating the picture and what we’ve got here is my grid line

34:00as I mentioned to you before it looks as though I’ve dragged a stick through the sand and I’ve pulled up debris on the

Transcript for The Search for Color from a Fiber Laser. (Cont..)

34:06other side of the groove then we go in and have a look at that closer in a few moments but one thing I want you to

34:13notice is this is the thickness of the cut line the beam width what’s this here

34:22around the outside because that is double the width well there we have it in high magnification

34:28I’ll bring the debris into focus and

34:33they’re not bring the bottom of the groove into focus and then somewhere in between those two we should find that we

34:44get the surface of the material now what I’m now going to do is turn down the

34:50side lights and we’re good to leave the

34:56halogen lights return the halogen lights back up okay so I’m gonna come in and

35:01from the top I’m going to gradually focus in on now you see these points

35:07just here and here not that one quite but these two particularly look these are sufficiently high that

35:15they’re just coming into focus can you see the colors on there gradually I’ll

35:23lift the table up look at all those lovely colors on there we’ve go past the

35:31peak of that debris and I’ll gradually bring the table up and as I bring the table up look the surface of the

35:36material is now coming into focus so this previous brought black band that

35:42we can see is now coming into view as a band of oxide that either side of my cut

35:47that has been heat affected there all the temper colors that we’ve mentioned

35:53many times before that’s the varying thickness of oxide that’s occurring on the surface that’s

36:00thin film interference for you at its best let’s drop the table again and

Transcript for The Search for Color from a Fiber Laser. (Cont..)

36:05bring these other things interview and here we’ve got the same thing look we’ve

36:11got thin film interference as the metal on the side is cooled it’s called in

36:19different ways and left all these colors on the material it’s not a flat plane

36:25system if we’ve got any sort of variation in the surface structure of

36:31the material these lights that we can see here are going to bounce off and

36:36they’re going to interfere with each other we happen to be seeing them here right close up you will not see the

36:42right close-up and you will see them you will see these as a mixture of colors because they will combine before they

36:48hit your eye remember I pointed out to you that this line looked as though it was gold

36:54can you see much heat of gold in there it’s all sorts of colors one of them is

36:59not gold what you’re saying Gold is a total resolution of all the mix of

37:04colors okay so there’s one thing that I wanted to show you okay now this is one

37:09of those cerise come dark pink come maroon whatever color you want to name

37:15it as this is the top of the color band let’s just quickly zoom to the other end

37:21for a minute now we’ve got a little bit of this coloration this oxide coloration

37:28that we were talking about just here this is the first sweep line that went across there now remember at the top of

37:35this pattern and I’m just going to zoom up just going to move up to the top of the pattern quickly so here is the

37:40single line that produced that pinky move swatch and it started from the

37:45bottom where I showed you we’ve got this slightly raggy pattern okay that was the

37:51first line at the bottom now we look at the last line at the top now what we see

37:59there is the same line finishing off the beam width across there but behind it

Transcript for The Search for Color from a Fiber Laser. (Cont..)

38:08we’ve got all these mysterious patterns the color patterns that are left behind

38:13when the but when the surface material cools down and oxidizes so these are

38:20already interference patterns before they actually come out as far as your eye so this is the thickness of the last

38:26line in the engraving and it’s that width because there’s no wake behind it

38:34so obviously it’s the trailing edge of the pattern that’s causing this effect

38:40when it’s cooling down behind the line that’s traversing up the pattern because

38:47that line that final line is still nothing like that line there which is

38:56the line that produced it so how come that line produce that line it’s

39:03presumably because the material was already preheated and warmed at that stage that’s why I wanted to show you

39:09one of my grid lines because it clearly shows you that just outside the cut area in the grid line we have got a cooling

39:15area which responds to this tempering colors and cools down and produces a

39:21varying thickness of oxide film on the surface so even though this might be a

39:27little bit of a plate up field it’s still cooling in the same way that all those curved lumpy pieces of metal on

39:34either side of my groove down the net result of my groove was gold the net result of this is a crimson

39:41so I think we’re beginning to understand the mechanism of where the colors are coming from now without any doubt at all

39:48but this is only the simple version of

39:54generating colors we have come across another one which is interesting and a whole new field to be looked at and

40:02that’s when we wide the power up so what color do we think that is going to

Transcript for The Search for Color from a Fiber Laser. (Cont..)

40:09produce that’s the line that I’m using to produce the patent now that’s a much

40:14more positive line than the previous line that we saw now there is the last

40:20line in the pattern which matches the line that we’ve just seen and there is

40:26our pattern which as you can see has got quite a bit about to focus on it I have to fiddle around with it to get the

40:32focus to both that surface which is there and some of the other pieces as well so that is a bit of a crinkly

40:38surface well there it is at low resolution to the naked eye that is a very pale green but it’s a glittery

40:45green it’s a sparkly green and I think you can probably see why it’s a sparkly green and in this instance you can see

40:52the last line here matches the line that we used to draw it with even the line

40:59itself is crinkled so it’s been a very good session because I’ve discovered several interesting points about how

41:05these colors start to come about I would thank you for your time and see in the next session

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