The Tangerine Tiger Series with Russ Sadler
In this Series, Russ has purchased a new 500 x 300mm, 50W laser machine from eBay with a view to modifying and upgrading it. In fact, he rips out the glass laser tube and high voltage power supply and replaces them with an RF laser source and PSU from Cloudray. Find out how the expensive RF laser source compares to a glass CO2 laser tube and prepare to get your hands dirty! So read on to learn about 3D Laser Engraving with Grayscale.
If you are considering purchasing a CO2 laser machine with an RF laser source from one of the big boy suppliers, I would suggest you check out this series before making a decision!
Contents
The RF Technology’s ability to almost instantly switch to different power levels, makes it well suited to creating a variable depth scan line. Add all these scan lines together and proper 3D engraving is the result. I have successfully mastered the process on my glass tube machine, but the PWM manner of tube control used by the RF technology appears to offer different challenges. I explained the process of “burning” wood with a laser beam in the previous session and showed that with well-chosen parameters it was possible to excavate a significant volume of wood and NOT leave a charred surface behind.
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Transcript for 3D Laser Engraving With Grayscale
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0:00 well thanks for joining me and my little
0:03 tangerine tiger here tonight um it’s a
0:06 bit cold in this workshop but
0:07 a the things i do for the love of
0:09 education
0:11 well i’m starting a little bit early
0:12 this year i’ve got my christmas mug out
0:14 trying to get a bit of christmas spirit
0:17 going i mean it’s been a funny old year
0:19 um whichever part of the world you’re in
0:22 i’m sure that you’ve been um
0:24 suffering a little bit whether it’s
0:26 through uh
0:28 a pandemic or whether it’s through
0:30 politics
0:31 um i’m sure we all suffer the same
0:33 problems so um
0:35 my heartfelt sympathies go out to all of
0:37 you last time
0:38 we tackled the what i call the flaky
0:40 part of grayscale engraving
0:44 you would think that grayscale engraving
0:48 and grayscale photographs would go
0:51 together
0:51 and make a perfect marriage i think we
0:54 demonstrated that
0:56 it was rather difficult and probably not
0:58 a very good
1:00 stable process today we’re going to
1:02 tackle the more credible part
1:03 of grayscale engraving and that is
1:07 3d engraving in the same way that
1:09 grayscale
1:10 photo engraving could only be done on
1:13 certain materials
1:14 there had to be materials that would
1:16 scorch grayscale
1:19 3d engraving can only be done on certain
1:22 materials
1:22 and it won’t be the same group of
1:24 materials for instance
1:26 we can’t 3d engrave a piece of card or
1:28 paper
1:29 it has to be a piece of wood with some
1:31 thickness on it for example
1:33 leather i’ve never tried to engrave
1:35 leather but i suppose it’s possible but
1:37 i’m sure it would be
1:38 very difficult to charcoal it by the
1:40 time you finished plastics
1:42 materials like corian for example which
1:44 are basically
1:46 a powder filled acrylic material you’ll
1:48 be able to
1:49 engrave acrylic all sorts of woods like
1:52 mdf
1:52 woolly grave plywood
1:56 ordinary wood many many ordinary woods
1:58 but
1:59 one of the problems with many ordinary
Transcript for 3D Laser Engraving With Grayscale (Cont…)
2:01 woods is the
2:02 huge change in the material texture
2:06 as you go within the wood itself because
2:09 you’ve got
2:09 resin you’ve got hard parts you’ve got
2:12 soft parts depending on the growth rings
2:14 that take place in the wood
2:15 the molecular makeup of the wood changes
2:18 and so consequently it’s very difficult
2:20 to get nice uniform
2:22 engraving with some woods now i’ve put
2:25 my little test pattern back into
2:26 photoshop
2:27 and i’ve converted it into a grayscale
2:29 image and then i’ve modified these first
2:32 five pixels here as you can see such
2:35 i’ve got black
2:36 three quarters black half black half
2:39 white which is mid gray
2:41 then we’ve got a quarter grey and
2:44 something that’s nearly white
2:46 so we’ve got a fairly reasonable quick
2:48 change over those first five pixels
2:50 but then when we look at the signals to
2:52 create the power
2:54 for these we should get an idea of
2:55 what’s going on
2:57 now i anticipate that for instance for
3:00 that pixel there it’ll be 100
3:02 on for this pixel here it’ll be roughly
3:04 50
3:05 on 50 off and this one here will be
3:07 nearly all off it’s not just a matter of
3:09 having this
3:10 grayscale on here we have to tell
3:13 rd works that we want to use grayscale
3:16 in other words we want to make
3:18 the signals for these colors
3:21 proportional to
3:22 the color and we do that by putting this
3:25 switch on here it’s called
3:26 output direct what we can do we can
3:29 choose here
3:30 min power and max power at the moment
3:33 i’ve got it set at one
3:34 for minimum power and a hundred percent
3:37 maximum power now what that means is
3:40 that i’m gonna use one percent to
3:43 represent white
3:44 two five five and 100
3:48 to represent 0 which is black so i’m
3:51 going to burn
3:52 as much as i can for black and as little
3:54 as i can for white
3:55 that’s fine until we look at the
3:56 calibration graph for this machine
4:00 now the tube itself is
Transcript for 3D Laser Engraving With Grayscale (Cont…)
4:04 it should technically be linear but in
4:07 reality
4:08 it doesn’t look as though the output is
4:09 linear it’s not bad
4:11 it’s it’s sort of linear but not
4:14 exactly if i was to choose 50 power here
4:18 i would get roughly 50 black and 50
4:21 white in other words i’d get a mid gray
4:23 it gets a little bit more complicated
4:25 than that
4:26 because below 10 we don’t mark the
4:28 material
4:29 so there isn’t any point in going down
4:31 below 10
4:33 so what we do we set that to 10 percent
4:36 and now what happens is this gradation
4:39 256 grades of black and white
4:43 are spread over 10 to 100
4:47 not over 1 to 100 so whatever range you
4:51 specify here
4:53 the grace go 250 divisions get divided
4:57 into the a scale that you set here the
4:59 max and min that gets subdivided into
5:01 256 parts
5:04 because of the pwm we have the choice of
5:07 a frequency of anything from 0 to 25
5:10 kilohertz
5:11 as a mechanical engineer i’m struggling
5:13 a little bit to try and work out
5:15 what the best combination is we’ll set
5:18 that to
5:20 20 kilohertz and we’ve got a speed
5:24 here of 100 millimeters a second
5:30 and there we go we’re expecting to see
5:33 if you remember
5:34 20 pulses per pixel
5:38 these are the first five pixels look
5:40 there’s a black one on permanently more
5:42 or less
5:42 this one is slightly lighter and it’s
5:46 off
5:46 for some of the time this one is mid
5:48 gray and it’s roughly 50
5:50 on 50 off this one is lighter
5:54 so it’s off more than it’s on and this
5:56 one is nearly white so it’s nearly off
5:58 most of the time and just a little bit
6:00 on
Transcript for 3D Laser Engraving With Grayscale (Cont…)
6:01 so if i change this frequency here to
6:03 say one
6:05 so that i get one pulse per pixel
6:08 and not not 20 pulses per pixel one
6:12 thousand
6:17 and there’s my first pixel there’s my
6:19 second pixel
6:21 there’s my third pixel my fourth and my
6:24 fifth pixel here are two things that are
6:26 exactly the same
6:27 relatively speaking they don’t look the
6:29 same but
6:31 i can either choose 20 kilohertz
6:35 and here are my pixels
6:39 we can see here the black one the dark
6:41 gray one
6:42 the 50 50 mid gray one then the lighter
6:45 gray one and the nearly white one
6:47 i mean the nearly white one is mainly
6:48 off and only just a little bit on and
6:51 here it’s 50
6:52 on 50 off but look i’ve got exactly the
6:56 same situation here
6:58 when i run instead of a 20 kilohertz
7:00 time base
7:01 if i run a one kilohertz time base i’ve
7:04 still got my power on
7:06 per pixel this is fifty percent power on
7:09 and fifty percent power off and this is
7:12 fifty percent power on
7:13 and fifty percent power off which of
7:15 them produces
7:17 the biggest burn let me try and put this
7:20 into some sort of humorous perspective
7:23 that helps me to try and analyze the
7:25 amount of damage
7:27 that would take place under these two
7:28 different circumstances
7:30 if i was intent on committing suicide i
7:33 could jump out of the ground floor
7:35 window
7:35 20 times or i could go to floor number
7:40 20
7:40 and jump out once now i know it’s a
7:43 fairly brutal
7:44 analogy but i’m going to do a lot more
7:45 damage when i jump out from the 20th
7:47 floor
7:48 than if i’m going to jump out 20 times
7:50 from the ground floor if i leave it set
7:52 at 20 kilohertz
7:53 then this will automatically adjust
7:55 itself to whatever size pixel and
7:57 whatever speed i’m running and it’ll put
7:58 an appropriate number of pulses
Transcript for 3D Laser Engraving With Grayscale (Cont…)
8:01 in to each pixel but it doesn’t mean to
8:03 say i’m getting the best
8:04 amount of power out of this machine into
8:07 every pixel
8:08 if i want to try and do the analysis
8:10 carefully as i’ve done
8:12 with my spreadsheet and calculate
8:15 what the optimum frequency is to get
8:19 one pulse per pixel as opposed to
8:23 20 pulses per pixel i think i’m going to
8:25 get a much more
8:26 efficient burn out of this machine
8:29 okay now i’ve devised a very simple test
8:32 we’ve got a mid gray test square 10
8:35 millimeter square
8:36 like this now i’ve got a four inch lens
8:38 in here because i know from
8:40 previous experience with 3d engraving
8:43 that you actually need a long focus lens
8:47 previously i’d used a two and a half
8:49 this time i’m going to try and use a
8:50 four inch lens so this first test
8:53 is the 20 kilohertz test
8:56 [Music]
9:03 wow there’s a lot of material being
9:05 removed there now we do the one
9:06 kilohertz test beside it
9:18 so we’ll just do a quick measurement
9:19 approximately a millimeter
9:24 no different color no different
9:28 finish no different so it appears i’m
9:31 worrying unnecessarily
9:33 they come out to the same result i had
9:36 the air assist on
9:37 so i was blowing the smoke back down
9:38 onto the job i’m going to turn the air
9:40 assist off now
9:42 and see what effect it has
9:48 okay so that’s good that’s hardly made a
9:51 mark on it at all look it’s
9:52 pretty clean so we’re not blowing the
9:54 crap down onto the job
9:56 so that’s the one kilohertz
10:00 as opposed to 20 kilohertz
Transcript for 3D Laser Engraving With Grayscale (Cont…)
10:04 let’s just try the 20 kilohertz beside
10:06 it this time
10:08 just to be sure that we’re comparing
10:11 eggs with eggs
10:13 now i look at that and i think to myself
10:14 i’ve got more damage along this bottom
10:16 edge here
10:18 with 20 kilohertz that i have
10:21 doing it the other way around i saw it
10:23 there and i thought
10:24 maybe that’s an exception but no it’s
10:26 repeated here as well so the one
10:28 kilohertz gives a cleaner engraving
10:30 result
10:30 we’re going to go and search on google
10:33 for
10:34 3 d
10:39 engraving
10:42 bitmaps and we get all these images to
10:45 look at so let’s just click on some of
10:47 these just click on the images
10:48 and these are special bitmaps you can’t
10:52 just
10:53 take any photograph and do an engraving
10:56 you have to have a special especially
10:59 prepared bitmap
11:01 because these bitmaps have got a strange
11:04 look to them they look almost like wax
11:06 this is a good example of what i mean
11:08 basically
11:10 if you could regard remember black is
11:13 zero and white is two five five
11:17 and there are all these levels of gray
11:19 in between those two numbers
11:21 so if you look at a survey map say a
11:23 mountain
11:25 there will be little rings around the
11:27 top of the mountain and
11:28 the size of the rings will tell you what
11:30 the shape of the mountain is as you go
11:31 further down the mountain
11:32 the rings will get bigger and they will
11:34 get all sorts of funny shapes but
11:36 the line that’s drawn that funny shape
11:39 is the height of the mountain it’s like
11:41 a slice
11:42 through the mountain well that’s
11:44 effectively what this is this is a 3d
11:46 object that has been sliced
11:48 this way and the lines that are on top
11:50 the layers that are on top
11:52 are white and the layers that at the
11:54 back are black
11:57 and that’s how we’ve got 3d nus into
11:59 this picture we’ve used the color
Transcript for 3D Laser Engraving With Grayscale (Cont…)
12:02 as a 3d feature
12:05 so you can’t just take an ordinary
12:07 photograph
12:08 and use it because it doesn’t have this
12:10 information in it
12:11 the color codes the third dimension
12:14 file import and there we go 100 no no no
12:17 no no
12:18 no we were running 100 millimeters a
12:21 second and taking big chunks out
12:23 i think we’ll run that around about 200
12:25 millimeters a second
12:26 i’m just guessing these parameters uh
12:30 advance it doesn’t make any difference
12:32 we’ll set it to 20 kilohertz
12:35 because we found that it makes no
12:36 difference and
12:39 minimum power here’s the difficult bit
12:42 because i don’t know at what level power
12:44 we shall see
12:46 nothing so i’m going to leave it set at
12:48 five
12:49 and a hundred we’ve got our output
12:50 direct switched on
12:54 and our swing um
12:57 i very much don’t we’re going to get
12:59 point one with a four inch lens it’s
13:01 probably going to be 0.2
13:04 so maybe
13:07 mind you if i do point one i should get
13:11 like a double cut
13:15 so yeah i think we’ll leave it at point
13:16 one the question is what should we
13:19 try and engrave if i engrave a piece of
13:22 plywood like this
13:24 then i’m going to get different layers
13:26 in it now that might be interesting
13:28 to see different layers in here
13:31 different colors
13:32 nice and grainless this popular plywood
13:34 this is very
13:35 soft so it should burn quite easily
13:41 i’m just putting the uh magnets on here
13:43 just to
13:44 just to hold it in place my focus should
13:46 be set to 15 but what i’m going to do
13:49 i’m going to set it to 14 so that is
13:54 probably going to go two or three
13:55 millimeters deep now this is a very long
13:57 focal length lens so it’s not going to
13:59 make a great deal of difference
14:00 to the focal distance if i change it by
Transcript for 3D Laser Engraving With Grayscale (Cont…)
14:03 a millimeter basically i’ve now set my
14:05 focus roughly one mil inside the
14:07 material this has got quite a big
14:09 program there’s a lot of information in
14:11 here
14:12 and i’ve probably mentioned to you
14:14 before what i do as soon as the pro
14:16 as soon as the head moves i’m going to
14:18 press pause
14:19 because the program is going to take
14:20 quite a long time to download
14:22 and i don’t like the machine to try and
14:23 walk and talk at the same time
14:25 okay so i’ve turned the air assist off
14:27 now because i don’t want air assist on
14:30 we’re just going to close the lid and
14:31 let the smoke get sucked away i just
14:33 remembered we did say that one
14:35 kilohertz was better because one
14:38 kilohertz actually
14:39 gave a cleaner result so we’re now going
14:42 to close the lid
14:43 getting a very very deep cut i think
14:46 it’s too brown
14:46 i think we should start again it’s
14:48 already doing a superb job
14:50 but i would like it to go faster not
14:52 quite such a deep cut we’ll change the
14:54 speed to
14:55 slightly less smoke because we’ll be
14:57 converting less
14:59 solid into gas so there’s our first pass
15:03 we’ve already got some quite nice
15:04 profile into it
15:06 and i’m just going to put a little mark
15:07 on here because that’s past number one
15:10 we have to do this multiple times you
15:13 could take a look in the middle here and
15:14 you’ll see there’s a little white
15:16 spot in the middle there where it hasn’t
15:19 cut
15:22 it’s the same as the outside here so
15:25 that has basically that’s the mountain
15:27 top
15:27 where we’ve got if you like no cutting
15:30 that’s five percent power which is not
15:34 having an effect at all
15:36 and this bit around the outside here is
15:38 100 power which is
15:40 digging away a lot deeper
15:43 so we just run the same program again
15:45 and again
15:46 and again to get deeper and deeper and
15:48 deeper because
15:49 whatever shape we’ve got there
15:51 proportionately the same percentage will
15:53 come off
15:54 every time so the more that came off
15:57 this time
15:58 the more will come off next time and so
16:00 the profile will gradually get more
Transcript for 3D Laser Engraving With Grayscale (Cont…)
16:02 3d as we take passes
16:07 okay we’re gonna run the fourth cut
16:10 and you can see it from the front
16:40 so there it is with all its information
16:44 looking at it front on you can’t really
16:46 see
16:47 how 3d is
16:52 when we look at it from the side
16:55 look at that using quite incredible the
16:59 definition
17:00 you’re getting on these features in the
17:02 middle here
17:10 well we did anticipate that this was
17:12 going to be one of the machines
17:13 strengths
17:14 because you only have to look at a
17:16 company called kerns
17:18 and they specialize in this sort of
17:19 stuff using rf lasers so
17:21 you know i knew that it was going to be
17:23 good but i have to say
17:25 that’s exceeded my expectations
17:29 took a little bit longer than i thought
17:30 but on the other hand it’s still not too
17:32 bad for 30 watts we found a way of
17:36 balancing the speed the material
17:39 extraction and the least amount of
17:42 damage
17:43 it’s a pale brown it’s not burned it’s
17:45 not barbecued
17:47 i’m very happy with the result and the
17:49 crispness and the the quality of it is
17:51 superb there isn’t even there’s no hint
17:54 of curtains on there at all
17:56 or those funny lines that i had
17:58 previously on my other machine
18:00 that only took about three and a half
Transcript for 3D Laser Engraving With Grayscale (Cont…)
18:01 minutes for a pass
18:03 and there was four of those so that’s
18:05 what 12 13 minutes
18:07 i suppose that’s not bad it’s nice to
18:09 find something really positive about
18:11 this machine even though it is rather
18:13 niche
18:14 well i think that basically concludes
18:16 our first very quick
18:17 preview if you like of what this
18:19 machine’s capabilities are
18:21 i think what we’re going to do now is
18:23 gradually go back to the beginning
18:25 start looking in much more detail at
18:28 things like photo engraving
18:30 and order engraving on different
18:33 materials
18:34 to see what the problems are and i
18:35 suspect that for that quality of work
18:38 on this price of machine kerns can’t get
18:41 anywhere near it
18:42 the only thing that limits us really is
18:44 30 watts
18:46 with 60 watts we’d ever been able to run
18:48 twice as fast we’d probably be able to
18:49 run it a thousand millimeters a second
18:51 thank you very much for your time and
18:52 patience again
18:53 and i hope this has been an interesting
18:55 session it certainly has been for me
18:58 and i’ll catch up with you next session
19:00 bye now
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