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

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