14 – Fiber Laser Marking: Is this Fools Gold? (23:53)

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.

They have been designed for high speed marking and the technology has been well tried and proven. There are limited “tricks” that the pulsing laser technology can perform. You enter predefined parameters for each marking “trick” you wish the machine to deliver , then stand back in amazement. Most correspondents tell Russ that they have bought their machine direct from China and received a machine and EZCAD software, preloaded with a few default parameters. No other instructions beyond the EZCAD manual are forthcoming.

Russ states “I am neither a teacher or expert in this field so you join me in my learning adventure with the warning that I have a simple but inquisitive mind and will probably make mistakes on my way to discovering the truth. I WILL oversimplify and maybe distort the scientific detail in my quest to build a simple picture of why and how this technology works. I am not trying to reverse engineer anything, just to break through the seemingly impenetrable ‘techno cotton wool’ that surrounds this amazing piece of science.”

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Fiber Laser Marking - Some of The Colours Obtained
Fiber Laser Marking – Some of The Colours Obtained

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Transcript for Fiber Laser Marking: Is this Fools Gold?

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0:00welcome to another fiber laser learning

0:02that last time we built a foundation on laser fiber

0:06the color gold today we’re going to try

0:10and consolidate that foundation a little

0:12bit more because we can’t really build

0:15up all the walls of the house until

0:16we’ve got a good foundation and there

0:20are a couple of big questions that I

0:23would like to answer before I go forward

0:25I’ve heard that there are three major

0:27problems with putting color on to

0:30stainless steel there’s a fairly narrow

0:32range of parameters for each color well

0:35I think last time we discovered that

0:37there was a very wide range of

0:39opportunity for gold now I only tried it

0:45for nanosecond pulses but within that

0:47four nanosecond pulse there was a huge

0:50range of possibilities that existed for

0:52finding gold but I want to look at the

0:54other possible problems today as well

0:56one of them is the thickness or the if

1:00you like the thermal conductivity of the

1:02material which will pull heat away from

1:04the actual work surface and it will

1:07change the color so unwarned and

1:09unrelated to that thermal conductivity

1:12is air temperature in other words if

1:15it’s a hot environment you will get

1:17different color results to have it’s a

1:19cool environment so we’re going to test

1:22the stability of the Gold’s that I found

1:24was it fool’s gold or is it the real

1:27thing that will resist changes of

1:30temperature and changes of thermal

1:32conductivity in the material as we saw

1:34last time there are many types of gold

1:38those that are gold but don’t show up

1:41only in a certain light and there are

1:45those sorts of gold here and here which

1:48are pretty good at being viewed in all

1:52sorts of lighting conditions now these

1:54are the goals that I want to look at

1:56today I’ve searched through the color

1:58swatch that I produce last time and

2:00identified or highlighted here those

Transcript for Fiber Laser Marking: Is this Fools Gold? (Cont…)

2:03colors that were sparkling six or seven

2:07of them which are what I call good

2:11quality gold what I want to find out is

2:13are there

2:13any common factors that give us some

2:15clues as to what produces what type of

2:18gold I think the answer is yes there’s a

2:21bit of an odd one there at twelve

2:23hundred and fifty millimeters a second

2:24but most of the sparkly ones if you

2:26notice are up here in the sixteen

2:28hundred to two thousand millimeters a

2:30second range and then we start taking a

2:34look at the gold we had a light gold and

2:37then we had the slightly coppery colored

2:39what I would call rose gold so we’ve got

2:42four three and two point five which

2:44produces light gold and if you remember

2:47when we looked at the pulse per square

2:50millimeter density we’ve got numbers

2:53here which are in that which are a

2:54hundred K now when we went to rose gold

2:58the parameters have tightened up quite a

3:01bit although we had fifteen ninety seven

3:03there that’s basically the same as 1600

3:05and they’re both the same so you would

3:07expect those two to be the same but then

3:09we’ve got this one here at two thousand

3:11with a slightly smaller pitch one point

3:14six microns and that gave rose gold as

3:16well and again when we looked at the

3:18pulses per square millimeter these are

3:20in the hundred and fifty six K so there

3:22appears to be a color difference that we

3:25can identify from pixels per square

3:27millimeter and tie that in with the

3:29microns that we’re using it gets us a

3:32nice rose gold color so we’re gonna

3:34start off today by just reproducing this

3:37result here which should be a nice rose

3:40gold okay so we’ve got a nice solid gold

3:43there okay so the first test I’m going

3:46to carry out is using my thermocouple

3:48here my k-type thermocouple which is

3:51sitting directly under the heated area

3:54now

3:58this will just basically check the

4:00thermal conductivity of the heat zone

Transcript for Fiber Laser Marking: Is this Fools Gold? (Cont…)

4:03through this very thin point five or 0.7

4:06thick stainless steel so probably my

4:09hand heat has pushed the temperature up

4:11a little bit the air temperature in here

4:13is around about probably 10 degrees C so

4:16I’m a few degrees higher than the

4:18ambient but let’s not get too concerned

4:21about that

4:29and hey you saw what the temperature

4:31went up to 70 degrees C okay so let’s

4:36turn this little cold workshop into

4:38summer should we turn this piece of

4:41metal into something about 40 degrees C

4:45it’s a pretty

4:52there we go one warm summer’s day

5:05warder 65 color change what do you think

5:14so there’s myth number two blown out the

5:16water it’s not very temperature

5:18sensitive at all

5:19let’s go myth number three which is

5:23thickness of material now haven’t got

5:25any really thick stainless steel but for

5:27the purpose of this very very small test

5:29we’ve gone from 0.5 to something like

5:32about 1.6 so we’re more than three times

5:35the thickness and what I’m going to do

5:37I’m going to do the test right in the

5:38middle right in the middle of the piece

5:40of material so I’ve got the maximum

5:42amount of heat being sucked away this is

5:44basically the heat being pulled away

5:46from the surface by a much larger

5:48thermal mass so let’s see whether this

5:51has an effect on the color that I’m

5:53producing it’s also a mechanically

5:55polished stainless steel this time as

5:58opposed to a piece of bright annealed

6:00maybe slightly redder than these first

Transcript for Fiber Laser Marking: Is this Fools Gold? (Cont…)

6:03two so it is possible that there is some

6:06small degree of variation with

6:10temperature or with heat sinking so

6:14we’re not going to dismiss it completely

6:17but what I would say is it looks as

6:19though it’s fairly resilient to the two

6:21extremes that I’ve just tested so it

6:24takes my fear away from the possibility

6:27that I may have discovered fool’s gold

6:30now I think it’s pretty real and that we

6:33can work with general workshop

6:35parameters and not worry too much about

6:37the color and we have just shown that at

6:392 microns it’s a pretty durable color

6:43resisting both heat sinking and

6:46temperature rise but what these results

6:50seem to indicate sparkle over here and

6:54color over here because here we’ve got

6:58the first four results between four

7:00three and two and a half giving us a

7:02light gold and then we’ve got these

7:05second three results here which are

7:08giving us a rose gold two and 1.6 micron

7:13pitch so the indication here is that if

7:15we go from say

7:17- which is what we’ve seen our nice rose

7:20gold s 2.05 in other words half a micron

7:26pitch that’s a fairly significant change

7:28in the heating effect that we’re going

7:30to see into the material are we going to

7:33push this rose gold towards a purple or

7:35a moe let’s give it a try that’s a

7:38pretty nice powder blue sparkly powder

7:44blue

7:44so my first shot will be to calculate

7:47quickly how many pulses per square

7:49millimeter it took to achieve that and

7:52then we’ll try a few more variables to

7:56see whether we can repeat that color

7:57with different parameters I’ve just

8:00calculated post density for powder blue

Transcript for Fiber Laser Marking: Is this Fools Gold? (Cont…)

8:02and it’s six hundred twenty-five

8:04thousand so I’ve done a quick

8:06calculation and to check the extremes of

8:09what we found before for spark cleanness

8:11roughly two thousand and twelve hundred

8:14the pitch becomes naught point four

8:17microns and naught point six six microns

8:20we’ll try those two numbers and see

8:22whether we can replicate powder blue now

8:25that is weird because that’s sixteen

8:28hundred millimeters a second half a

8:31micron two thousand millimeters a second

8:34point four of our on twelve hundred

8:38millimeters a second point six sixth of

8:41a micron a thousand millimeters a second

8:44point eighth of a micron nine hundred

8:48millimeters a second twenty nine of a

8:51micron and eight hundred millimeters a

8:54second one micron the rule seems to hold

8:58up except that one there’s nothing wrong

9:01with my calculations these are all done

9:03with exactly the same calculation in a

9:05spreadsheet I really don’t understand

9:07why that should be different the

9:09principle involved here is very simple

9:11we’ve got exactly the same number of

9:14pulses per square millimeter which

9:17technically means we should have exactly

9:20the same heating effect per square

9:22millimeter the only difference is we’ve

9:25changed the relationship between the

9:28pulses across

9:29and the lines down in general it looks

9:33as though it doesn’t make any difference

9:35but in this particular instance for some

9:37strange reason it does

9:40that’s a bluey green that’s a nice

9:41powdery blue I suppose and these are I

9:45suppose edging towards a green rather

9:48than a blue I can see clearly that that

9:51one has got a smoother effect to it as

9:55we decrease the speed we’re putting more

9:57pulses in in the horizontal direction

9:59and we’re producing a smoother effect it

Transcript for Fiber Laser Marking: Is this Fools Gold? (Cont…)

10:02would appear that the roughness or the

10:04texture on the surface comes from

10:06running at the higher speeds as I

10:08anticipated before I mean to get blue

10:10we’ve got actually got to drive right

10:12through this color range here to get

10:15towards the hotter part of the spectrum

10:18and obviously by closing up the pitch

10:20we’re putting more heat into the

10:22material I mean logically it does make

10:24sense that I should move from here to

10:27blue although I didn’t didn’t think that

10:30it was going to be as Extreme as that I

10:31thought it would move from there from

10:34that to rate first as we start moving in

10:36towards the hot razón we won’t know

10:38until we really go and have a look at

10:39these under the microscope okay so

10:42here’s a puzzling image it’s a sort of a

10:44a purpley gold so that was when we

10:48changed to say point five five look a

10:53half a micron and there’s no apparent

10:57difference so let’s go down half a

11:00micron it looks like the same picture

11:02because that’s what the color is on the

11:04surface it’s it’s exactly the same

11:06colour when you look at it in normal

11:08light okay so let’s go back to this

11:12image which is the starting image and

11:15this time instead of changing the pitch

11:18we’re going to reduce the speed to 1900

11:21which means we’re going to reduce the

11:23number of pulses in this horizontal

11:25direction we’re giving a little less

11:28mode and a little more blue so now we

11:32reduce it to 1800 though we’re getting a

11:36lot more blue and a lot less pink

11:39although the yellow hasn’t changed very

11:40much

11:41so now we reduce it to 1600 a little

11:44less pink we’ve got some green coming in

11:47a bit now but it’s still rough as you

11:51could see from the texture now we’re at

11:531600 and we’ve virtually lost all the

11:56yellow and we’re just in two shades of

11:58blue and green now and sure enough the

12:01color is coming out as a very nice blue

Transcript for Fiber Laser Marking: Is this Fools Gold? (Cont…)

12:03now we’re at 1500 still a nice sparkly

12:07texture more green less blue no yellow

12:12now we’re going out to 1400 ah now look

12:16what’s happening now 1400 can you see

12:20all these sort of blotches coming in and

12:24these blobs we’re getting much more of a

12:28flatter surface now this is what this

12:30indicating although we’ve still got some

12:32spark cleanness in there we’ve got areas

12:35where the surface is basically flat and

12:39now we come down to the final test which

12:42is 1,300 still got a moderately rough

12:45surface there it is sparkly now what you

12:50must remember is there is no green in

12:53these temporary colors so these colors

12:59that we’re seeing here there must be a

13:01combination of light rays which are

13:03creating colors that are not really

13:07there and these are the colors that we

13:09can see at high magnification once they

13:13get drawn away and get to your eye

13:15these colors don’t exist what you see is

13:18an amalgam of these colors I haven’t

13:20done the calculations at the moment to

13:22see what degree of variation we’ve got

13:24in the pulses per square millimeter

13:26count across this range of colors I will

13:30go and do that shortly

13:31we’ve just come across coppery gold

13:34again okay so let’s run again with two

13:39microns or I have to say it’s a bit

13:42difficult to say what that color is it’s

13:45it’s almost just a blank brown it’s

13:49certainly not sparkly

13:52so I think we’ll try and put some

13:53Sparkle into that by increasing the

13:55speed which is the formula for spark

13:58leanness so far we’ll push the speed up

Transcript for Fiber Laser Marking: Is this Fools Gold? (Cont…)

14:03to 1600

14:04okay now by pushing the speed up we’ve

14:09decreased the heat and we’ve got our

14:14copper color back again which is

14:17virtually the same as these two here

14:20let’s see if we can lighten the gold by

14:22putting the speed up leaving the picture

14:252 microns well yeah we’ve gone lighter

14:28and we’ve also gone spark Leah and those

14:32two there were done with a for

14:35nanosecond pulse but this time we’ve got

14:37our nice coppery gold rose gold at 6

14:42milliseconds as opposed to 4 nanoseconds

14:44so I wonder what happens if we go two

14:48thousand and something like point five

14:54point five of the micron well the answer

15:00is it gets us back to this strange brown

15:03color that we had here it’s not sparkly

15:07it’s it’s a dull brown so I’m not

15:11interested in that really I mean it’s

15:12obviously part of the color spectrum

15:14it’s going to take a long time to

15:15produce it at point zero at point five

15:19of a micron so I’m trying to see if I

15:21can get nice color and relatively high

15:25speed let’s jump up to another power

15:27band let’s try eight nanoseconds which

15:31will be at two hundred and fifty

15:32kilohertz and we’ll start off again what

15:36should we say 1200 let’s say 8 microns

15:41well we got a a sparkly coffee color

15:46there that’s nearly gold but not quite

15:48it’s like a a white coffee and we’ll do

15:53two things we’ll first of all put the

15:55speed up to 2000 and see what happens

15:59so we’re decreasing the power which

Transcript for Fiber Laser Marking: Is this Fools Gold? (Cont…)

16:01means we might move too

16:03- sparkly gold again yeah

16:06that’s actually not bad that’s even more

16:10that’s a bit of a copy but this one or

16:12some of these here and these down here

16:16so we found rose gold again at another

16:20set of parameters yeah we’ll take the

16:23vertical lines down to 6 micron 6 micron

16:26spacing so we’re adding some heat now

16:31which might drive us towards blue yeah

16:36there’s definitely a blue tinge in there

16:37it’s no longer copper so let’s push it

16:41one more down to 4 microns which

16:46increases the power permit per square

16:48millimeter and that’s done something

16:50really weird we’ve got a sort of a green

16:54on the ends and a gold in the middle now

16:58that must create that must be created by

17:00some really weirds heating effects

17:02because we are scanning like this so it

17:09means we’re getting double a heating

17:11effect at each end like that hot there

17:18turn round hot there so this is very hot

17:21this area and then as we scan across

17:23this middle area here we’ve got a cooler

17:26zone and that’s exactly what that

17:31pattern there seems to be showing I’m

17:32sure you could see that in this light

17:34let’s just zoom in on that

17:35there we go look you can see that

17:37clearly there now gold in the middle and

17:39green at the ends so does that mean if I

17:42go down to 2 microns I might be finding

17:45a sort of a peppermint green well the

17:48answer to that question is no we’ve

17:50we’ve gone to a very nice coffee color a

17:55very nice sort of a but you’ll notice

17:58something else in here as well look

18:00we’ve got the same effect that we had

Transcript for Fiber Laser Marking: Is this Fools Gold? (Cont…)

18:02here we’ve got the ends which are a

18:06different color to the center well

18:10although this is very interesting and

18:11we’re getting further and further away

18:13from gold but we are

18:15effectively trying to see if there are

18:18any patterns in the data that we’re

18:21getting I’m still trying to see whether

18:23or not there are any rules for colors

18:26and this one here again it’s a color

18:30that’s at two microns

18:32that’s a nice coincidence that we’ve

18:34come across many times before and at two

18:38thousand millimeters a second with a

18:40different pulse now we came across this

18:44lovely but very positive meter brown and

18:48if we take a look here look at the

18:50texture of the surface we’ve got all

18:52these little blobs on the surface here

18:54little raised portions so let me just

18:57bring one of them into clear focus and

19:02that’s 41 microns let’s just see how

19:07that relates to the background right

19:09there and that’s 39 38 so that’s about a

19:16three micron difference in depth which

19:22is substantially more than the thickness

19:25of the film itself so we must be

19:27disrupting the surface of the metal to

19:30make that amount of distortion so I did

19:34the calculations for that mid Brown and

19:35found it was sixty-two thousand five

19:37hundred pulses per square millimeter now

19:41I changed from two thousand at two

19:45microns to one thousand at four microns

19:50okay now that looks like a modern

19:54artwork but even though that is

19:59different it still comes out looking the

Transcript for Fiber Laser Marking: Is this Fools Gold? (Cont…)

20:03same mat made of brown now is a huge

20:08change in terms of the speed going from

20:11two thousand two one thousand and the

20:14line width from two microns to four

20:17microns we get no apparent change of

20:19color even though you can see that it is

20:22significantly different down at this

20:24level so here we are at three microns

20:27and thirteen hundred and thirty three

20:30millimeters a second again that we’ve

20:33got these little raised blobs here but

20:36they’re not as pronounced as they were

20:37in the first one but we still got lots

20:39of yellow in the background and we’ve

20:42still got the same apparent meat brown

20:45despite this different slightly

20:46different surface texture so we up the

20:50speed again to sixteen hundred

20:51millimeters a second and dropped the

20:54pitching to 2.5 microns

20:57we’ve got blocks here with modes and

21:00browns and we’ve got yellow in the

21:03background and gold and red the net

21:07result of this is still a meat brown so

21:12we’ve got a very very wide range of

21:15opportunity to get this lovely meat

21:18Brown blank color I think I’m going to

21:21have to produce a separate swatch with a

21:23record of each one of these colors on it

21:26so that we can see what our progress is

21:28and what the lovely range of colors that

21:31I should be able to put onto this

21:33palette so although I’ve been supplied

21:35with a recipe of colors from Lotus laser

21:39I have to say I’ve not opened the files

21:41at all I’m going my own way at finding

21:45colors with my method because I’m

21:48looking for a different sort of color

21:50that normally you see on these pallets

21:53now I’m feeling fairly happy with that

21:56swatch because even in this white LED

21:59light we’ve got some nice colors this is

Transcript for Fiber Laser Marking: Is this Fools Gold? (Cont…)

22:03not daylight this is this is a thing

22:05that was defeating other systems that

22:09should be green those should be I think

22:15that’s pink and that one’s gold

22:19that one’s gold I think these are

22:24supposed to be a pub a purple and I

22:27think these are silver this one is

22:29supposed to be like a sky-blue and it’s

22:32come out as a sort of a bit of a grey

22:33here the color recipe that I’ve been

22:36given is nothing like the recipe that

22:40I’m

22:40yet here no we accidentally came across

22:45this setting doesn’t look particularly

22:48different to some of the golds that

22:50we’ve seen you know it’s it’s got like

22:53pieces in it yellow pieces a little bit

22:56of pink in it some blue what color do

23:00you think that’s gonna come out to look

23:02at that isn’t that beautiful

23:04cuz look I can get that I can get the

23:07top of that lock into focus now let’s

23:10call that 90 well the bottom is just

23:13here somewhere I’ll just bring that

23:15little bit of brown into focus there and

23:18that’s only 88 so that’s only 2 microns

23:22difference what color would you think

23:24that that is going to come out at okay

23:32you’ve had enough time the answer is

23:34matte black don’t ask me why just

23:42mention it in your prayers tonight see

23:44if you get an answer so thanks again for

23:48your time and patience and I’ll catch up

23:50we’re doing the next session

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