18 – Fiber Laser Tutorial Video: Intertwined Parameters (53:00)

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 Fiber Laser Tutorial Video Russ discusses Intertwined Parameters.

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

All the work that Russ has done chasing colours has given him an understanding of how each parameter variable can affect the output. It has also given him an understanding of the more complex relationship between these parameters and how they are intertwined. Watch on for how these insights can affect your future laser marking performance.

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Fiber Laser Tutorial Video - Parameter Variables for Mopa  Laser
Fiber Laser Tutorial Video – Parameter Variables for Mopa Laser

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Transcript for Fiber Laser Tutorial Video: Intertwined Parameters

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0:00welcome to another fiber laser Learning Lab here we’ve got some D-Grade colors

0:07yeah I know I said I was never gonna go back and do any more color chasing and we’re not now I owe these colors one

0:16thing and that’s a big thank you although I am very disparaging about

0:21them and the quality of them and the durability of them and the time they take they have taught me a great deal

0:28about the parameters that are used to obtain these colors and they’ve given me

0:33a great understanding of exactly what the parameters do on this machine now although we’ve tackled parameters in

0:40various ways in different sessions up to now they have been independently looked

0:46at without trying to work out what the relationship between them is so today I

0:53want to look at all these parameters separately in a slightly more in-depth

1:01way than we looked at before but I also want to try and demonstrate the relationship between them now

1:07individually these are all separate parameters but I’m afraid you can’t just

1:14adjust one of these parameters and expect it to if you like move proportionately because some of these

1:20parameters as you change one parameter it changes some of the other parameters and that’s the interrelationship which I

1:26want to look at today and the lesson that these degrade colors have taught me

1:33now percent power is a fairly blunt tool and you may think that changing the

1:42power by 50 percent reduces the damage to the surface by 50 percent wrong

1:50because other things are happening when you change percent power as well as the

1:56watts let’s try and tease that apart and explain to you because I hope that the

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

2:02pictures that I’m going to show you today will give you a much clearer image that you can carry in your mind when

2:10you’re adjusting these parameters now the whole point about these degrade

2:15colors is that they are not interfering with the texture of the surface they’re

2:21only interfering with the thickness of the oxide film on the surface of the

2:27material and the oxide film is only a few nanometers thick so by definition we

2:33don’t need huge amounts of heat and energy into the surface of the material

2:39to modify this oxide layer so the whole point about these colors is it requires

2:47tremendous finesse and control of the parameters to manipulate the oxide film

2:56now jpt in their specification claim that they’ve got a seven millimeter

3:02diameter beam now I don’t know exactly what that means but let’s assume that it

3:08means what I’ve drawn here that we’ve got a beam which is seven millimeters in diameter total it’s claimed that there

3:14is a very near Gaussian distribution power within the beam and so here we’ve

3:20got a graph of the light intensity within the beam itself which follows

3:26this Gaussian distribution so we’ve got maximum light intensity right at the

3:33center of the core of the beam this central third of the beam is carrying

3:38about 70% of the light intensity on average I mean obviously the intensity

3:44in this area changes as well but there’s seventy percent of the light intensity which could be interpreted as power or

3:52energy or destructiveness is happening within a central section of the beam

3:58then there’s about another 27% I think it is around this next section and about

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

4:05five percent at the outside so we’re taking a seven millimeter beam and we’re

4:11going to put it through a lens which is 254 millimeters focal length now that’s

4:18quite a long focal length lens but once it gets down to the focal point it focuses down

4:24to something called a spot size which is point zero seven now I think in reality

4:30it’s point O six five but for convenience purposes as you’ll see in a few seconds I’m choosing to use a near

4:37equivalent point O seven because point O seven happens to be a hundred times

4:44smaller than seven millimeters so what this means is as I push this seven

4:52millimeter beam through a point O seven millimeter spot size what happens to

5:00this normal distribution aha it’s still

5:06a normal distribution even at the focal point I’ve drawn this normal

5:12distribution here and I’ve called this height of the graph one hundred percent power it doesn’t matter what the height

5:19is I’m just nominally calling that a hundred percent power so if I take this

5:24seven millimeter beam and compress it down to point O seven effectively what I’ve done I’ve amplified the light

5:31intensity within this graph by a factor of 100 if I look at what happens here

5:38when I multiply zero by a hundred I’m still going to get zero if I multiply

5:46these very small low intensity values by a hundred they’re still going to be low

5:53but as I move up this graph here and I take this high value intensity and I

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

6:00multiply it multiply it by a hundred I’m going to get something which is very

6:06interesting we’re certainly not going to get this same normal distribution shape

6:12at the focal point what we’re going to get is this now I’ve drawn this base

6:23line here away from the focal point just for clarity but look you can just see

6:28very small there the normal distribution curve that I’ve drawn well that’s not

6:33what’s going to happen this is what’s gonna and at that point we’re going to

6:39multiply the intensity of the light by a factor of a hundred as I said to you

6:45before zero multiplied by a hundred is still zero and so this base line will

6:52still be the same across here but what what happened is to the rest of the curve it’s going to expand in a very

6:59disproportionate way and effectively what we’ve got here is a very sharp

7:04point of energy now I do not want you to run away with the idea that this is a

7:11real thing like like a drill it is a graph of the light intensity within the

7:19beam and remember light intensity is damage the more intense the more the

7:26damage understanding this is not a drill but a graph of energy intensity and it’s

7:33got a very very very sharp spike of energy at the center as you can see there and that spike of energy remains

7:41pretty sharp for quite a long way back before it starts let’s call this

7:48softening shall we as the light intensity gets lower so it’s in ability to do damage gets less so that’s what

7:56happens at a hundred percent power and for comparison let’s take a look at 50%

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

8:0220% and 10% power now as we multiply that normal distribution by these

8:09numbers here’s what happens to the graph of intensity as you see it’s getting

8:16shorter and shorter but the one thing you can’t really see is that not only is it getting shorter but this point here

8:24at the end is getting softer it’s becoming much closer to this sort of

8:32shape here look we’ve got a huge range over which we’ve got very intense light

8:38and damage can be done here the range has dropped down quite considerably and

8:45here it’s even less and here it’s probably non-existent effectively this shape is containing 20

8:52watts now this shape here is containing 10 watts and this shape here is

9:00containing 4 watts and this shape here is containing 2 watts even though the

9:06power in total has dropped off the way in which that power is being applied to

9:11the surface is changing as well it isn’t just power we’ve got sharp power and

9:18we’ve got blunt power that’s the best way that I can describe it and the best

9:23way that you can visualize it the power is being applied very softly and gently here but here it’s a bit brutal a bit

9:32sharp a bit spiky exactly like the picture looks but I must insist you do

9:37not imagine this to be a drill this is not something solid this is just a graph

9:43of intensity ok now you will start to hear me using

9:48the term sharp and soft I’m talking of in terms of the way in which energy is

9:53applied gently to the surface or in a very sharp manner and I suppose the

9:59other way that you could imagine what I’m talking about when I say sharp and soft is this a sharp beam will produce

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

10:10damage to the surface like this where we shall have quite a deep hole in the middle and a little bit of a softer hole

10:17around the outside but here look here’s the shape of the pit that will be made

10:23by a sharp beam whereas when we get to the other end we can have the same

10:30diameter

10:35but the damage to the surface will be much more uniform and gentle and it

10:42won’t be aggressive like this so that’s the other way that you can imagine soft

10:47and sharp in all mobile Asus there are a selection of pulse width as that you can

10:55choose that’s what makes this different to a q-switched laser where you only

11:00have one pulse shape that you can generate you can vary the number of

11:05pulses and you can vary the power in the pulse but you can’t vary its shape this

11:11system here with its 16 different pulses allows us to have great finesse over the

11:18amount of power that we’d put down onto a surface now these are just a pictorial

11:23representation of all the pulses that are available you can see we’ve got the very shortest pulse here which is a two

11:29nanosecond pulse and then we’ve got the longest pulse here which is a 350

11:35nanosecond posts now the seconds are the billionth of a second so you know they’re not very long pulses even the

11:41longest posts but the most important thing about them is this bit here the

11:47rise time it’s a very very rapid rise time to get to its let’s call it peak

11:55power I mean the peak power for a very long pause is still about six kilowatts

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

12:02and the peak power for these shorter ones is up here in the 12 to 13

12:09kilowatts right at the top here so they’ve got a very sharp very powerful

12:14posts now the one thing that these fiber lasers at 20 Watts can do that you

12:21certainly couldn’t do with a 20 watt continuous power co2 laser it’s the damage metal and there’s a very

12:28fundamental reason for that you may remember a couple of sessions ago when I demonstrated the crystal structure or

12:35the atomic structure of various materials there were different stiffnesses because of the bonding arrangement between the molecules and

12:42the atoms now with all metals in their solid state

12:48they have got a very crystalline uniform structure and that crystalline uniform

12:53structure is very very difficult to oscillate and vibrate with photons so

13:01it’s very difficult to get heat into metal with light because most metals are

13:10in the 96 to 98 percent reflective that means you’re only able to push 2 to 4

13:17percent of energy into the material which means you’ve got to pump a hell of

13:23a lot of energy into the material very quickly to change it from solid to move

13:30to molten before it gets a chance to realize what’s happened now once the

13:37material is molten you have actually destroyed the uniform crystal structure and it will absorb the energy and can

13:43you can continue to melt that’s why I mentioned this rise time here it’s a

13:50very rapid rise time and not only is a very rapid rise time but look we’re

13:55talking about kilowatts from a 20 watt laser so the pulse that we’re

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

14:00stimulating the material with is extremely energetic and I’m absolutely

14:06sure this is the reason why you can damage metal with this laser that you

14:11can’t do with a 20 watt continuous beam laser so the rise time on a co2 laser is

14:18about a millisecond whereas the rise time on this beam is in the order of a

14:25nanosecond let’s take a look at one of these pulses and the one that crops up

14:31and keeps the widest range of this color that we’re looking at on here is down at

14:38the bottom end here as a very sharp pulse at 4 nanoseconds that green one

14:46there peak power on that is somewhere in the range of about 12 kilowatts and to do that you have to run the system at

14:53500 kilohertz if you run it at other than that you won’t get 12 kilowatts now

14:59depending on how good your memory is you might remember seeing that picture or something similar to it and one of the

15:04early sessions when we talked about how this fiber laser works now the scale

15:11across the bottom is the pulse repetition frequency all the kilohertz and that runs between zero and a

15:18thousand kilohertz the pulse that we want to look at is halfway across here

15:25at 500 kilohertz so that’s where that’s where our 4 nanosecond pulses so at the

15:34start of a new cycle the pump diode will switch on and gradually increase its

15:40intensity which its ability to convert electrons up to their higher state and

15:45eventually we should reach this point here where the charge will then be

15:50released and we will get out for nanosecond pulse if we choose a frequency higher than the 500 peak value

15:58then what happens is the power will still be available there we will still

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

16:04have 12 kilowatts available to us but what will happen is that 12 kilowatts

16:12will drop off in a nonlinear way as we

16:17get towards a thousand kilohertz I mean right down at this end here where it’s

16:23roughly 200 we’ve got about a 13 nanosecond pulse so we’re still talking

16:28about that pulse there which is still not a very long pulse but what happens is we could strangle that pulse before

16:36it even gets up to power by for instance we could decide to run it at a hundred

16:44kilohertz as opposed to 200 kilohertz no 200 kilohertz will be peak power and 100

16:52kilohertz will be approximately half power because it will be halfway up this

16:58linear charging so we have got the opportunity of playing with the power

17:04within the pulse by messing with the pulse repetition frequency now if you do

17:11it on the upside while it’s charging it’s fairly linear if you do on the

17:18downside where you’ve got a lot more pulses to work with you’ve still got the

17:24same amount of power but you’ve got to divide that power over many many more

17:30pulses so as we start going along this nonlinear scale here we’re actually

17:37producing a nonlinear rise in the power within this beam so right up here at say

17:44800 kilohertz we’ve only got a very small amount of energy that we’ve put

17:50into the beam so that’s what we’re going to get out now the net the reason I need

17:57to point that out to you is there are although you think you’re working down this side of the beam in reality you’re

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

18:04still only charging up on a linear a basic linear charge but you’re selecting

18:10points along that linear charge which are none linear because of this graph

18:16here we’ve got a relatively sharp beam here but as we start attenuating that by

18:26messing around with this frequency along the bottom here it will no longer be a

18:3313 nanosecond pulse with a sharp peak what will happen is it will start still

18:39be 30 nanoseconds wide but it will start coming down here and becoming softer and

18:44softer so the more you attenuate it the more you soften it and remember

18:52softening does less damage here we can do a lot of damage into the material but

18:59in a very short period of time here we’ll do a lot of damage into the

19:04material over a longer period of time because we’ve got some sustain on there so we should actually be able to do more

19:10damage with a 13 nanosecond pulse than we will with a 2 nanosecond pulse but if

19:15you soften a 2 now in a second pulse even right down here it’s still going to be pretty sharp whereas with the 13

19:22nanosecond pulse as you can see it’s going to get softer and softer I hope I’m showing you this strange

19:28relationship between pulse width and softness as you start attenuating it

19:34away from its peak value I keep coming back to this because we need soft power to heat the few nanometers of film

19:44because we don’t want to break through the film if we want to break through the film then we need sharp Peaks we need

19:53lots of hundred percent power and sharp points regardless of which one we choose

19:59I know these are already softer but you can soften them even more by first of

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

20:04all attenuating the power by not using the specified peak power frequency and

20:11you can soften them even more by messing around with the percentage power so you

20:20can put softening on top of softening or you can put sharpening on top of

20:28sharpening now I know these are very strange terms I’m using here but I hope they’re sufficiently diagrammatic and

20:34pictorial for you to carry in your brain and help you to try and understand what you’re doing when you’re messing around

20:40with these parameters so there’s three features here that you can mess around with to decide whether you want a puddle

20:47or a pothole power which is a very very

20:52blunt instrument but you can superimpose that on the top of the pulse choice and

20:59the frequency use with your pulse choice so we can strike off percent power we

21:07can strike off pulse width we haven’t talked about pulse repetition frequency

21:13completely because pulse repetition frequency is also linked to speed hmm

21:25let’s take a look at that relationship should we we’ve seen the relationship between pulse repetition frequency pulse

21:32width and power because there is a link

21:37between those but there’s a second here and here now I’ve drawn this

21:46picture before you before but we’ll draw again and try and explain it again for a

21:52two nanosecond pulse the pulse repetition frequency is 850 kilohertz

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

22:01now let’s not get too picky about that let’s call it a thousand kilohertz which

22:07is basically a million cycles a second so we’ve got all this time when nothing

22:14is happening hey yeah I’m some sort of comedian look a millionth of a second all this time we’re looking at things in

22:22relative terms here so two nanoseconds and this is one millionth of a second or

22:29a thousand nanoseconds no I’m not going

22:36to get another one of these pulses until here so we’ve got all this time in

22:43between when nothing is happening except cooling because this is heating and this

22:53all of this he’s calling on that basis

23:04we’re not going to heat the material up at all because we’ve got 998 nanoseconds

23:09of cooling and 2 nanoseconds of heating well that’s ridiculous innit the only

23:16saving grace is the thermal conductivity of the material is just not going to

23:22respond quick enough to drag the heat away in this short period of time so

23:28yeah there is a little bit of physics which will work for us in this case and

23:33my exaggerated cooling is not quite as exaggerated as I’m making it but what

23:39we’ve got here is one microsecond between the pulses I’ve made life easy

23:44for myself I haven’t covered all the combinations but I’ve covered the basic 16

23:50pulse widths that we’ve got there and what I’ve looked at mmm is that for a

23:57two nanosecond pulse operating at its proper 850 nanosecond period if we run

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

24:06at 1 millimeter a second we shall put down 850,000 pulses in that 1 millimeter

24:18because 1 millimeter a second 850,000 pulses a second because that’s what this

24:25says so if we raise the speed to 100 millimeters a second we’re going to get

24:318500 pulses per milliliter that’s still a lot of pulses per millimeter and if we

24:38increase the speed even more up to a maximum of 2,000 which is what the

24:44machine can do we drop that down to 425 pulses per millimeter so what I hear you

24:51ask this is 850 kilohertz remember I’m going

24:56to give you a very silly example now of 1,000 Hertz not a thousand kilohertz but

25:041000 Hertz one millimetre over one

25:10second so I’m travelling at one millimeter a second I’m going to produce at a thousand a thousand Hertz I’m going to

25:17put a thousand pulses down in one millimeter and that’s what it looks like that’s at 1,000 Hertz now at 1000

25:26kilohertz I’m gonna get a thousand times more pulses in the same distance in the

25:32same time so in terms of heating there’s

25:38a relationship between speed and pulse repetition frequency but of course pulse

25:44repetition frequency that I’ve shown you just here is just the maximum pulse

25:50repetition frequency you start adding that in to varying the pulse repetition frequency with the pulse width and

25:59you’ve got all sorts of combinations that can have happen so we’ve got this one which is linked

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

26:06into speed and then you can add power to it as well so you can change with four

26:15of these variables playing in together and then we’ve got this thing here pitch

26:20which is the spacing between the lines that you’re scanning now here I’ve got

26:28just a simple example of the point O seven beam moving half a beam width

26:370.035 35 microns most of these on here are round about

26:43one or two microns just imagine the overlap that we’ve got when we do all these pulses all this

26:52close together so we’ve got a tremendous heating effect that is potentially there but what do we do well we can kill it

27:01with speed we can kill it with power we can kill it with we can’t kill it with

27:07pulse width because we’ve got a fixed pulse width for our for our test but we

27:13can fill it we can kill it with pulse repetition frequency so we’ve fixed the

27:18pulse width because we said that most of these these are all done with a four nanosecond pulse that’s the only thing

27:24that was constant throughout all of those tests now with this line here we

27:30changed the pitch between the lines this one here we change the pulse repetition frequency this one we change

27:37the speed this one we change the power now I will explain to you in a few seconds what we did to get these results

27:43but just to show you that there is a big difference in manipulating the power

27:49with each one of these different parameters now this is not mixing the parameters this is just keeping them

27:56plainly one parameter at a time all the others are fixed and constant we did

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

28:02talk about in a previous session focus I mean this is about point five six stainless is our material base let’s

28:10call that as far as the machine setting is concerned that’s classed as zero that’s the table okay now when you

28:19go into easy CAD you can offset for your material thickness and my material

28:25thickness is 0.5 easy CAD will not allow me to decrease the material to less than

28:34zero it will only go plus okay so the

28:40very worst I can do is to push my focus down to the table which is minus 0.5 now

28:48I’m told that that is allowable let’s just come back to a second to this picture here now as I try to explain to

28:55you this is not a drill this is a graph of light intensity but what that does

29:02mean is to say that the intensity at this point is not uniform therefore when you’ve got

29:11a hundred percent power you can do damage maybe eight or ten millimeters

29:17below the focal point and equally well

29:22because this is a mirror image inside here as the beam squashes down you will

29:28equally well be able to do damage eight or ten millimeters above the focal point I’m told that you mustn’t ever go the

29:36way that aren’t going below the focal point I’m trying to get to the bottom of

29:41just why I can’t do focus I’m told that it’s all to do with reflections back

29:47into the laser I can’t explain it to you the moment because I have got no idea why or how it happens or it can happen

29:54I’m trying to get an explanation and when I do get an explanation I will point it out to you guys but in the meantime I’ve got to pass on the warning

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

30:02that I’ve been given don’t go below the focal point always raise the material up

30:08okay that said let’s just see what this means we’ve got ten millimeters plus or

30:16minus here maybe if you’re using full power if you start reducing it to 50%

30:24power then what happens is the focal point or the point at which you see

30:29to do damage gets closer and closer and closer to the real focal point which is

30:35there if you’re using low power you might be able to use a little bit of

30:40focus to attenuate the power even more if you’ve got 100% power you’ve got to

30:47move a long way plus and minus to get any effect of this end of the peak so

30:55although you can mess with focus it’s very much a bit of a variable because

31:01you don’t know where it is because it depends very much on your percent power so in general terms I would say don’t

31:07mess with the focus you’ve got enough control with these other features so what we’re going to

31:13take a look at now is the way in which these features affect color because

31:25remember color only happens under a certain set of conditions you start

31:31moving away from those conditions and I cannot tell you exactly what those conditions are we are working in this

31:37region here the puddle region we want everything soft to produce these colors

31:45we mustn’t damage and get through the chromium oxide film so everything that

31:53you’re going to see here is associated with this end the soft end of the power

31:59region now all these tests started off with exactly the same parameter for like a magenta color a degrade magenta now

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

32:07I’ve got these being viewed at a very low angle to the light so that you can

32:13see them but what I’ll now do is line up the parameters here for you now you can

32:18probably just about see that one on the end there which is 21% that is virtually

32:26invisible but when you catch it in the light it produces these iridescent

32:32colors like you see on a bubble then we move on to these oranges and then

32:37through sort of a pale move this one here 81 which is 20 three percent power is the standard that

32:44we shal use throughout so we’ve managed to go from 23 percent down to 21 percent

32:49before we lost it and we lost it actually at 22 percent so we were fairly

32:54close to the band where we could lose red as we came up the scale here and

33:00increase the power 24 25 30 50 70 90 and even 100 percent we’ve gone to a very

33:07dark blue as you can see here to navy almost and here’s our standard again in

33:13the middle which is the same as that one and as we increase the speed effectively

33:19what we’re doing is decreasing the power because we’re putting down less dots per

33:24unit of distance less dots per millimeter what we’ve then found is that

33:29we can actually stretch this color this orange through mmm quite a few more

33:35steps by changing the speed then we could by changing the power by changing

33:42the power it just dropped off the end of the scale here it was 21% whereas here we’re able to go down in a much smaller

33:49increments and follow the color down so as we start going up the scale we were

33:58going up in bigger increments now 750 700 600 500 400 300 when I say going up

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

34:05what happens is that power is going up as the speed is going down we’re putting

34:11more dots per millimeter down so we’re putting more heat into the material and

34:16we’re getting commonality sort of here but then when it drops off beyond this point here these colors we don’t drop

34:23off to pale mode and then dark mode we go through this dark mode and then we get through to green very dark green and

34:31this looks like a very drab olive so it

34:37looks as though we’ve got more control over the heat application if we want to

34:43regard that as what the term is by changing the speed we’ve got constant

34:48power we’ve got constant everything else the pulse is constant at 4 nanosecond

34:54so if you like the shape of the puddle is exactly the same the only thing that

35:00we’re doing is changing the in this instance we are changing the shape of the puddle by making the puddle softer

35:06and softer here we’re increasing the distance between the puddles now I’m

35:12using these crude terms which I’ve tried to associate with pictures so that you can try and understand that these are

35:18not doing the same thing although they’re changing the power they’re not changing the application of that power

35:26in the same way so now we’re going for the pulse repetition frequency now the

35:33maximum power is achieved at 500 kilohertz and so what we’re now doing

35:38we’re softening the power by going to 480 460 and at 440 we’ve softened it so

35:48much that it’s dropped off the end of the scale and then you may or may you

35:53can probably just about see that one that’s 600 so we’ve dropped off the end of the scale again and as you would

35:59expect with pulse repetition frequency whether we go up or whether we come down

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

36:04makes no difference we’re going to get a reduction of power and a softening of the peak and that’s

36:10exactly what we can see here basically the center is correct and then it’s dropping off either side so with

36:17everything else constant again here’s our standard which is the same color to start with and now as we basically what

36:25we’re doing this way we’re going 1.7 1.6 1.4 and 1.0 micron pitch we’re getting

36:34closer together now that means as we’re getting closer together we’re applying more power per square area and as we

36:42apply more power per square area we’re moving through purple into a dark purple

36:49or AM ov and effectively it’s achieving the same sort of result

36:56to a certain extent as when we’re increasing the power here okay and we’re

37:03doing something similar when we increase the power here by decreasing the speed but it’s

37:10happening probably quite quickly here 1.7 so from 1.8 to 1 millimeter 8

37:18microns produces quite a significant change of color now when we come the other way up to 2 microns and now we’re

37:26decreasing the power because we’re going from one point eight to two point eight and at two point eight we virtually lost

37:33it again we’ve gone through these oranges to something which is a very

37:39nice iridescent bubble clear color almost and

37:45we get that effect again when we decrease the power here and here and

37:52we’ve decreased the power here and we’ve gone through this series of oranges here but we didn’t go through oranges this

37:58way we did touch on an orange that way as we disappeared off the end we touch on oranges we disappeared out these ends

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

38:05of the range and we got to an iridescent color just there now as you’ve seen

38:11there is some vague similarity between these results when you decrease the

38:17power you tend towards orange and when you increase the power you tend towards

38:23moe and eventually green or very very dark blue that’s about where the

38:31similarity ends because you start mixing these and the results are very

38:37unpredictable now before we adjourn to the workshop here’s what I’m going to try and do

38:44we’ve started off with four colors in here one off of each of these charts and

38:49they’re all at the low end of the power so here we had percent power and we went

38:57down to start with from our nominal color we went down and disappeared off the end of the chart before we pushed

39:04the tough before we pushed the power up so a two which is that one is low power

39:11orange so we increase the speed to start with and as we increase the speed so

39:16we’re reducing the power and here we are b4 with orange again and then with the C

39:28range we were playing with the kilohertz and whether we went up the chart or down

39:33the chart it really didn’t matter we could have gone for either c6 or c10 and

39:40I went for c10 both of which are decreasing power then we went finally

39:48for pitch as you close the lines up the heat intensity increases and then as we

39:55open the pitch up we start getting cooler less heating per unit area so

40:00here we’ve got a d8 which is that one which is an orange all of the oranges

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

40:08represent the low end of the power range they’re totally different textures even

40:15though they look like the same color to the eye so the power that’s being

40:20applied to the surface is completely different for each one of these parameters the whole point of my

40:26exercise with these colors is trying to make them more efficient in terms of cycle time and the way that you make

40:32them more efficient in cycle time is to open up the pitch as much as possible so can I get back from a high pitch and

40:41trust me 2.6 microns is still not a very

40:46high pitch but it’s still better than the 1.8 that we started with just here

40:52can I drag that 2.6 orange back towards

40:57this color by attempting to move some of these other features at 2.6 microns I’ve

41:04cooled the job down because I’ve opened up the pitch so therefore the strategy is to try and

41:11heat the material back up again by changing some of these other features

41:16now if we decrease the speed we’re going to put more heat into the job or we

41:23could increase the power we can increase the power and decrease the speed we can’t really do anything with c4 we’re

41:30already on that the most efficient our maximum power for this color so if

41:38we catch those in the light right there’s an orange e-gold that we’re

41:44starting with on the bottom and there is a target color they were aiming for

41:49which is the magenta color at the top so we’re trying to move up this chart here towards that target

41:57color now we can do it by coming down this chart or this one I think the first

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

42:04thing we’ll try is will come down here from orange and we’ve only got to take a couple of steps and we should be back

42:11here at the correct color and we’ve done that by changing the power by just 1% so

42:20currently the power is 23% and we’ve got to increase the power to get a little

42:26bit more heat into the job so if we take it from 23 to 24 percent that should fix

42:33it

42:38what does you see the good news is we’re going in the right direction Rico but we haven’t got there yet with 1% we’ve got

42:46to a pink rather than a crimson or a magenta so let’s go up another 1% will

42:57let get us there well it’s getting

43:02closer but it’s still not a match as you can see with we’ve got two Pink’s that are the same almost let’s go another

43:10percent I think you’ll see that there’s no difference in the shade of those

43:15Pink’s so we go for 26 to 36 percent power now remember what we’re doing is

43:21we’re increasing the power we’re making the pulse sharper we’ve not changed

43:26anything else we’ve still got our soft everything else so increasing the power

43:34started to take us in the right direction but then started carrying us

43:40off in a completely different direction because now we got three Pink’s that were more or less the same but now we’ve

43:48got a pink here which you can’t see it unless I turn it round and now as I turn

43:56it around look what’s happened to my Pink’s they’ve disappeared but what about the one on the end that

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

44:02I’ve just produced as I pointed out to you as I was doing it we’ve increased

44:09the power we’ve made it sharper we’ve worked our way through the surface of the material now on what we’ve done

44:15we’ve produced a b-grade color that is actually quite resistant

44:21to the light so this time we’re going to start the test off with d8 again before

44:28is only a few steps away from b1 so how hard can it be to reduce the speed and

44:36increase the power to gradually push us back towards b1 there’s our starting

44:42orangey gold again we will now increase the effective heating effect by pulling

44:49the speed from 800 let’s just go down to 780 very

44:54small step well we’ve had no significant effect at the moment by pulling the

44:59speed down very slightly let’s go with a significant jump in speed maybe let’s go

45:06down to 750 so there we go maybe we’ve pulled it slightly towards a rose gold

45:13or a a slight pink let’s try 700 yeah we’re getting a

45:19little bit of pink eNOS in there let’s go down to 600 aha now we’re making a

45:25little bit of progress that’s a big jump but we’ve got a slightly darker pink now

45:32it’s very difficult but as you can see in this light have I gone too far it’s

45:40got more blue in it perhaps I should go backwards and check whether or not I

45:46could get a good match it’s very difficult to see in these lights in it I think we go and look outside in the

45:53daylight it is so difficult to compare them isn’t it because you could have catch them in just the right light so

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

46:00we’ve got a pretty reasonable match there with our speed so that’s 650 that’s gone a long way down from 800 to

46:07get to heat the job up now the question is what’s the texture of that and what’s

46:15the texture of that and in this normal light we’ve got a reasonable match looks

46:24as though we might have a reasonable match here as well

46:40well I think as well as kids and animals we must almost add colors to the things

46:46that you shouldn’t do live on camera to the eye they look a pretty good match

46:53what do they look like under the microscope at the end of the day you’re

46:58not interested in what’s under the microscope what you’re really interested in is what the eye can perceive now here

47:05on this screen we can see a live view of one of the colors now as you can clearly

47:14see on here we’ve got some stripes and those stripes you would immediately

47:19think that’s the pitch that vertical pitch at which the the scan lines are

47:26taking place no the scan lines are taking place at

47:322.6 micron intervals here when I measure it with my scale this is hundred hundred

47:40and ten microns there’s no relationship between the pitch that I was setting on

47:46the machine and the pitch of this pattern now over here on each one of my thumbnails at 50-times magnification we

47:54can see exactly the same pattern they’re all 26 micron pitch but they’ve all got

47:59roughly a hundred and ten hundred micron pitch between their striking patterns so

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

48:05here’s some paper printouts of what you’ve just seen these are 400 times magnification of the surfaces and on

48:12each one of these surfaces we can see the yellow which is the basic surface as far as I’m aware and I’ve focused in on

48:19the yellow to try and get some resolution to the yellow the Blues are

48:25well out of focus on each one of these so this is not a real degrade color

48:33although it might perform like one it’s not a real degrade color because we’ve obviously got depth and you can’t have

48:39depth in something that’s only a few nanometers thick this is probably a micron or two microns depth so we’ve

48:47definitely gone past the thin film side of the color

48:55this is the master copy which we set up to start with and this was our emulation

49:01by approaching it with speed it’s

49:07similar but there’s more blue in this one a lot less blue in this one there’s

49:14more yellow in here and this one over here which is a power copy there’s got a

49:21lot more blue in it not as much yellow and very little pink so what’s on the

49:29surface is not what we’re seeing although I was disappointed that I actually got a pretty good color match

49:36when we look at them in detail a moderately pleased that it shows that we

49:42do not get a copy of the master by approaching it with different parameters

49:49the parameters are acting in a different way on the surface well that’s only just

49:56touching the edge of mixing parameters with that little experiment we didn’t

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

50:03really mix them very much we only played with two or three of them so but you’ve seen the principle and if you’re really

50:09that interested then you can go away and start mixing and matching the parameters for yourself but trust me playing with

50:17colors will teach you a great deal about the parameters and I hope that the one lesson that’s come through is what sharp

50:23and soft is when you apply it to each one of these major parameters and the effect that sharp and soft will have on

50:30the surface of your materials now to finish up with I’m just going to take a look on the screen here at first of all

50:37this is raw stainless steel I’m gonna take a look at something that we started

50:42to hold of this color session off with and here we’ve got some yellow and now we’re moving into a slightly darker

50:49yellow and hey look we’ve got some crystal structures growing now we’re

50:54moving into a a darker yellow and we’ve got some Brown crystals growing

51:02that the interesting question that starting to grow in my mind now is as we move into this color are those blotches

51:09some sort of leaching from the background or are those blotches growing

51:16in the oxide film now we’re getting into

51:21a slight rate now we’re getting into

51:28very red and the crystal structure in

51:33the background is getting smaller and more distinct isn’t that fascinating and

51:42that’s I think as far as the color changes go no we’ve got a slightly

51:48different texture just there and what are we looking at that’s what you were

51:55looking at I thought you might be interested to see how that compares with

Transcript for Fiber Laser Tutorial Video: Intertwined Parameters (Cont…)

52:01all the things that we’ve been trying to create on the machine over the past few

52:06sessions now I couldn’t do that to start with because we didn’t have the services of this lovely microscope but now we

52:13have I thought it might be quite a nice fitting end to the project no not quite

52:19the end to the project I think we’ll give it one more shot because there’s some quite important stuff that I think

52:25you might be interested in and what I think will probably be the final color

52:31search because to be honest I’m getting a bit fed up with colors I have to say

52:38thank you very much for your patience because although some of this stuff has been fairly interesting for me because it’s a learning exercise it’s stupid

52:46tedious of boring but for you it must be like watching paint dry anyway until the

52:52next session when I can assure you it’s gonna be slightly more interesting thanks for your time bye – Lynne

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