Laser Fiber Marking: Epic Tutorial On Laser Marking Colours

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.”

Contents for Fiber Laser Marking: Is this Fools Gold?

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

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Highly Magnified surface of Stainless Steel after Laser Fiber Marking
Highly Magnified surface of Stainless Steel after Laser Fiber Marking

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Transcript for Fiber Laser Marking: Is this Fools Gold?

Measuring the Temperature of Material During the Laser Marking Process
Measuring the Temperature of Material During the Laser Marking Process

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0:00 welcome to another fiber laser learning lab

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

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

0:10 and consolidate that foundation a little

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

0:15 up all the walls of the house until

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

0:20 are a couple of big questions that I

0:23 would like to answer before I go forward

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

0:27 problems with putting color on to

0:30 stainless steel there’s a fairly narrow

0:32 range of parameters for each color well

0:35 I think last time we discovered that

0:37 there was a very wide range of

0:39 opportunity for gold now I only tried it

0:45 for nanosecond pulses but within that

0:47 four nanosecond pulse there was a huge

0:50 range of possibilities that existed for

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

0:54 other possible problems today as well

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

1:00 you like the thermal conductivity of the

1:02 material which will pull heat away from

1:04 the actual work surface and it will

1:07 change the color so unwarned and

1:09 unrelated to that thermal conductivity

1:12 is air temperature in other words if

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

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

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

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

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

1:27 thing that will resist changes of

1:30 temperature and changes of thermal

1:32 conductivity in the material as we saw

1:34 last time there are many types of gold

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

1:41 only in a certain light and there are

1:45 those sorts of gold here and here which

1:48 are pretty good at being viewed in all

1:52 sorts of lighting conditions now these

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

1:56 today I’ve searched through the color

1:58 swatch that I produce last time and

2:00 identified or highlighted here those

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

2:03 colors that were sparkling six or seven

2:07 of them which are what I call good

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

2:13 are there

2:13 any common factors that give us some

2:15 clues as to what produces what type of

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

2:21 bit of an odd one there at twelve

2:23 hundred and fifty millimeters a second

2:24 but most of the sparkly ones if you

2:26 notice are up here in the sixteen

2:28 hundred to two thousand millimeters a

2:30 second range and then we start taking a

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

2:37 then we had the slightly coppery colored

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

2:42 four three and two point five which

2:44 produces light gold and if you remember

2:47 when we looked at the pulse per square

2:50 millimeter density we’ve got numbers

2:53 here which are in that which are a

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

2:58 the parameters have tightened up quite a

3:01 bit although we had fifteen ninety seven

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

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

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

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

3:11 with a slightly smaller pitch one point

3:14 six microns and that gave rose gold as

3:16 well and again when we looked at the

3:18 pulses per square millimeter these are

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

3:22 appears to be a color difference that we

3:25 can identify from pixels per square

3:27 millimeter and tie that in with the

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

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

3:34 start off today by just reproducing this

3:37 result here which should be a nice rose

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

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

3:46 to carry out is using my thermocouple

3:48 here my k-type thermocouple which is

3:51 sitting directly under the heated area

3:54 now

3:58 this will just basically check the

4:00 thermal conductivity of the heat zone

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

4:03 through this very thin point five or 0.7

4:06 thick stainless steel so probably my

4:09 hand heat has pushed the temperature up

4:11 a little bit the air temperature in here

4:13 is around about probably 10 degrees C so

4:16 I’m a few degrees higher than the

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

4:21 about that

4:29 and hey you saw what the temperature

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

4:36 turn this little cold workshop into

4:38 summer should we turn this piece of

4:41 metal into something about 40 degrees C

4:45 it’s a pretty

4:52 there we go one warm summer’s day

5:05 warder 65 color change what do you think

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

5:16 water it’s not very temperature

5:18 sensitive at all

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

5:23 thickness of material now haven’t got

5:25 any really thick stainless steel but for

5:27 the purpose of this very very small test

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

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

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

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

5:38 middle right in the middle of the piece

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

5:42 amount of heat being sucked away this is

5:44 basically the heat being pulled away

5:46 from the surface by a much larger

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

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

5:53 producing it’s also a mechanically

5:55 polished stainless steel this time as

5:58 opposed to a piece of bright annealed

6:00 maybe slightly redder than these first

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

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

6:06 small degree of variation with

6:10 temperature or with heat sinking so

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

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

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

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

6:24 takes my fear away from the possibility

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

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

6:33 can work with general workshop

6:35 parameters and not worry too much about

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

6:39 2 microns it’s a pretty durable color

6:43 resisting both heat sinking and

6:46 temperature rise but what these results

6:50 seem to indicate sparkle over here and

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

6:58 the first four results between four

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

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

7:05 second three results here which are

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

7:13 pitch so the indication here is that if

7:15 we go from say

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

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

7:26 pitch that’s a fairly significant change

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

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

7:33 push this rose gold towards a purple or

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

7:38 pretty nice powder blue sparkly powder

7:44 blue

7:44 so my first shot will be to calculate

7:47 quickly how many pulses per square

7:49 millimeter it took to achieve that and

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

7:56 see whether we can repeat that color

7:57 with different parameters I’ve just

8:00 calculated post density for powder blue

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

8:02 and it’s six hundred twenty-five

8:04 thousand so I’ve done a quick

8:06 calculation and to check the extremes of

8:09 what we found before for spark cleanness

8:11 roughly two thousand and twelve hundred

8:14 the pitch becomes naught point four

8:17 microns and naught point six six microns

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

8:22 whether we can replicate powder blue now

8:25 that is weird because that’s sixteen

8:28 hundred millimeters a second half a

8:31 micron two thousand millimeters a second

8:34 point four of our on twelve hundred

8:38 millimeters a second point six sixth of

8:41 a micron a thousand millimeters a second

8:44 point eighth of a micron nine hundred

8:48 millimeters a second twenty nine of a

8:51 micron and eight hundred millimeters a

8:54 second one micron the rule seems to hold

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

9:01 with my calculations these are all done

9:03 with exactly the same calculation in a

9:05 spreadsheet I really don’t understand

9:07 why that should be different the

9:09 principle involved here is very simple

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

9:14 pulses per square millimeter which

9:17 technically means we should have exactly

9:20 the same heating effect per square

9:22 millimeter the only difference is we’ve

9:25 changed the relationship between the

9:28 pulses across

9:29 and the lines down in general it looks

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

9:35 but in this particular instance for some

9:37 strange reason it does

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

9:41 powdery blue I suppose and these are I

9:45 suppose edging towards a green rather

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

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

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

9:57 pulses in in the horizontal direction

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

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

10:02 would appear that the roughness or the

10:04 texture on the surface comes from

10:06 running at the higher speeds as I

10:08 anticipated before I mean to get blue

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

10:12 through this color range here to get

10:15 towards the hotter part of the spectrum

10:18 and obviously by closing up the pitch

10:20 we’re putting more heat into the

10:22 material I mean logically it does make

10:24 sense that I should move from here to

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

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

10:31 thought it would move from there from

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

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

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

10:39 these under the microscope okay so

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

10:44 a purpley gold so that was when we

10:48 changed to say point five five look a

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

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

11:00 micron it looks like the same picture

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

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

11:06 colour when you look at it in normal

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

11:12 image which is the starting image and

11:15 this time instead of changing the pitch

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

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

11:23 number of pulses in this horizontal

11:25 direction we’re giving a little less

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

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

11:36 lot more blue and a lot less pink

11:39 although the yellow hasn’t changed very

11:40 much

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

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

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

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

11:53 1600 and we’ve virtually lost all the

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

11:58 blue and green now and sure enough the

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

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

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

12:07 texture more green less blue no yellow

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

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

12:20 all these sort of blotches coming in and

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

12:28 flatter surface now this is what this

12:30 indicating although we’ve still got some

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

12:35 where the surface is basically flat and

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

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

12:45 surface there it is sparkly now what you

12:50 must remember is there is no green in

12:53 these temporary colors so these colors

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

13:01 combination of light rays which are

13:03 creating colors that are not really

13:07 there and these are the colors that we

13:09 can see at high magnification once they

13:13 get drawn away and get to your eye

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

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

13:20 done the calculations at the moment to

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

13:24 in the pulses per square millimeter

13:26 count across this range of colors I will

13:30 go and do that shortly

13:31 we’ve just come across coppery gold

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

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

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

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

13:49 certainly not sparkly

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

13:53 Sparkle into that by increasing the

13:55 speed which is the formula for spark

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

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

14:03 to 1600

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

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

14:14 copper color back again which is

14:17 virtually the same as these two here

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

14:22 putting the speed up leaving the picture

14:25 2 microns well yeah we’ve gone lighter

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

14:32 two there were done with a for

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

14:37 our nice coppery gold rose gold at 6

14:42 milliseconds as opposed to 4 nanoseconds

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

14:48 thousand and something like point five

14:54 point five of the micron well the answer

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

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

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

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

15:12 obviously part of the color spectrum

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

15:15 produce it at point zero at point five

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

15:21 can get nice color and relatively high

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

15:27 band let’s try eight nanoseconds which

15:31 will be at two hundred and fifty

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

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

15:41 well we got a a sparkly coffee color

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

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

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

15:55 speed up to 2000 and see what happens

15:59 so we’re decreasing the power which

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

16:01 means we might move too

16:03 – sparkly gold again yeah

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

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

16:12 some of these here and these down here

16:16 so we found rose gold again at another

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

16:23 vertical lines down to 6 micron 6 micron

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

16:31 which might drive us towards blue yeah

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

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

16:41 one more down to 4 microns which

16:46 increases the power permit per square

16:48 millimeter and that’s done something

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

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

16:58 that must create that must be created by

17:00 some really weirds heating effects

17:02 because we are scanning like this so it

17:09 means we’re getting double a heating

17:11 effect at each end like that hot there

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

17:21 this area and then as we scan across

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

17:26 zone and that’s exactly what that

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

17:32 sure you could see that in this light

17:34 let’s just zoom in on that

17:35 there we go look you can see that

17:37 clearly there now gold in the middle and

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

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

17:45 a sort of a peppermint green well the

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

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

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

17:58 something else in here as well look

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

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

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

18:06 different color to the center well

18:10 although this is very interesting and

18:11 we’re getting further and further away

18:13 from gold but we are

18:15 effectively trying to see if there are

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

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

18:23 or not there are any rules for colors

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

18:30 that’s at two microns

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

18:34 come across many times before and at two

18:38 thousand millimeters a second with a

18:40 different pulse now we came across this

18:44 lovely but very positive meter brown and

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

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

18:52 these little blobs on the surface here

18:54 little raised portions so let me just

18:57 bring one of them into clear focus and

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

19:07 that relates to the background right

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

19:16 three micron difference in depth which

19:22 is substantially more than the thickness

19:25 of the film itself so we must be

19:27 disrupting the surface of the metal to

19:30 make that amount of distortion so I did

19:34 the calculations for that mid Brown and

19:35 found it was sixty-two thousand five

19:37 hundred pulses per square millimeter now

19:41 I changed from two thousand at two

19:45 microns to one thousand at four microns

19:50 okay now that looks like a modern

19:54 artwork but even though that is

19:59 different it still comes out looking the

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

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

20:08 change in terms of the speed going from

20:11 two thousand two one thousand and the

20:14 line width from two microns to four

20:17 microns we get no apparent change of

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

20:22 significantly different down at this

20:24 level so here we are at three microns

20:27 and thirteen hundred and thirty three

20:30 millimeters a second again that we’ve

20:33 got these little raised blobs here but

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

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

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

20:42 still got the same apparent meat brown

20:45 despite this different slightly

20:46 different surface texture so we up the

20:50 speed again to sixteen hundred

20:51 millimeters a second and dropped the

20:54 pitching to 2.5 microns

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

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

21:03 background and gold and red the net

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

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

21:15 opportunity to get this lovely meat

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

21:21 have to produce a separate swatch with a

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

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

21:28 and what the lovely range of colors that

21:31 I should be able to put onto this

21:33 palette so although I’ve been supplied

21:35 with a recipe of colors from Lotus laser

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

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

21:45 colors with my method because I’m

21:48 looking for a different sort of color

21:50 that normally you see on these pallets

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

21:56 swatch because even in this white LED

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

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

22:03 not daylight this is this is a thing

22:05 that was defeating other systems that

22:09 should be green those should be I think

22:15 that’s pink and that one’s gold

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

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

22:27 think these are silver this one is

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

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

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

22:36 given is nothing like the recipe that

22:40 I’m

22:40 yet here no we accidentally came across

22:45 this setting doesn’t look particularly

22:48 different to some of the golds that

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

22:53 pieces in it yellow pieces a little bit

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

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

23:02 at that isn’t that beautiful

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

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

23:10 call that 90 well the bottom is just

23:13 here somewhere I’ll just bring that

23:15 little bit of brown into focus there and

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

23:22 difference what color would you think

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

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

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

23:42 mention it in your prayers tonight see

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

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

23:50 we’re doing the next session

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