28 – How to Prepare A Picture For Laser Engraving – Part 2 (50:35)

The Lightblade Learning Lab with Russ Sadler

The Lightblade Learning Lab is a series of videos that Russ did for Thinklaser Limited based on using the Lightblade 4060 Laser Cutting and Engraving Machine. Thinklasers Lightblade 4060 has a 400 x 600mm bed size and was supplied with a 60W EFR laser tube. In this session, Russ shows us How to Prepare A Picture For Laser Engraving.

How to Prepare A Picture For Laser Engraving
How to Prepare A Picture For Laser Engraving

Contents

  • Looking at pictures and photographs.
  • Making a test program in RDWorks.
  • Draw a square and convert it to a scan program.
  • Doing a test which shows that the lines lasered from left to right don’t line up with those
  • lasered from right to left.
  • How to correct this with an ‘offset’ in RDWorks
  • Moving to paper
  • Working with a bitmap in RDWorks rather than Photoshop
  • Changing the resolution of the output from 300 to 150
  • Using ‘Dot Graphics’
  • Creating the engraving
  • Looking at the picture under the microscope.
  • Experimenting by doubling the resolution.
  • How can we improve on the photo?
  • Looking at speeds, power and resolution.
  • Why a lower power laser may be better for engraving paper
  • The best picture is the one where individual dots are made with low resolutions and low speeds.
  • Spots sizes.
  • The best spot size is with a 1.5” lens which gives a spot size of 0.075 mm (0.003”). For this,
  • anything over 333 ppi is a waste of time. If the spot size is larger with your lens
  • Experiment using ‘Output Direct’ to achieve greyscale engraving.
  • Looking at the tube during the engraving process.
  • The way that greyscale images are created using a different power for each pixel
  • Using a non-organic material you can’t use greyscale. Greyscale is best used for 3D carving.
  • Using anodised aluminium.
  • A real project example involving Photoshop to make some drinks coasters decorated with the photo of a dog.
  • Editing the photo to make it more acceptable.
  • Importing it into RDWorks
  • Setting up the program for Marine Ply
  • Lasering the job.
  • How to keep the job and the table clean.
  • Use of ‘Briwax’ (which is mainly beeswax) to protect the wood.
  • Summary

My thanks go out to Tom at Thinklaser for giving permission to embed these videos on this site. If you are looking for a new laser machine from a quality supplier, then I would suggest you check out their website: www.thinklaser.com.

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Transcript for How to Prepare A Picture For Laser Engraving

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00:17

Welcome to another Lightblade learning lab, I’ve got the sun shining on my face

00:24

through my workshop window it might make me look like a film star yeah I’m a bit

00:33

delusional I have to admit

00:36

anyway today we’re going to carry on with something we started off last time

00:43

which is dots now today we’re not going to really be talking too much about the

00:50

dots themselves we did an in-depth analysis of how dots can be formed why

00:55

they should be formed you know exactly all the things we’re going to be looking

00:59

for in this session we had to do the preparatory work because there was a lot

01:05

to get through now this might look like white wine trust me it’s not

01:11

it’s just lime cordial

01:17

it’s been a very hot day and I’m looking forward to the cool of

01:22

the evening and settling down showing you guys something interesting today

01:28

we’re going to get into pictures and photographs and all our hard work from

01:34

the last time is going hopefully show some good results now there might be

01:40

some surprising results but I hope they’re going to be interesting for you

01:44

now before we start we’ve got a couple of very important housekeeping tasks if

01:49

you really must perform at some stage before you start using this machine for

01:55

producing photographs or even for logos so we need quickly to just to jump into

Transcript for How to Prepare A Picture For Laser Engraving (Cont…)

02:00

RDWorks and I’ll show you a little test program that you should design

02:05

yourself and you can use on this machine alright we’re going to select a square

02:11

and then hold down the control key I’m going to just draw a square doesn’t

02:16

matter what at the moment we’re then going to put a handle around it and

02:19

we’re going to come up here to the dimensions and we’ll close the padlock

02:23

and we’ll set one of these dimensions at the top here and there we go we’ve drawn

02:28

a 10 millimeter square and that’s all our tests program is going to be we’re

02:33

now going to come off across to the parameters I’m going to turn this into

02:36

an scan program we’re going to scan it at various speeds so we’ll just set this

02:43

to 400 millimeters a second which is one of the fastest speeds that we like to be

02:47

using on our tests power we’ll leave it at 13% at the moment

02:51

no ticks X swing which is important the interval at the moment I’m going to make

02:58

it half a millimeter point five now that’s a huge interval but you’ll see

03:06

why in a minute okay now I’ve got a small piece of acrylic in there at the

03:10

moment I always like to use acrylic for test purposes and what I’m going to do

03:14

is just set the focus up to the correct focus for this particular lens at seven

03:21

and a half millimeters before I touch anything in the program we’re going to

03:26

just run a test

03:34

the first line at the bottom there was done moving from left to right

03:44

and that is quite important to remember that if you remember these strange

03:49

pictures that I showed you before the actual beam itself carries on dying

03:54

white way much longer than the laser beam switching off now that’s important

Transcript for How to Prepare A Picture For Laser Engraving (Cont…)

04:00

to note when we look at this pattern here because this pattern starts off

04:05

here and it runs to this side here and you can see there is the end of the line

04:13

where it turns off hangs over the beginning of the next line so what we’re

04:19

going to have to do is we’re going to have to put in what they call an offset

04:22

correction and RDWorks allows us to do that and let me show you where it

04:28

happens, now we need to come up here to config

04:33

and in conflig we’ve got system setting and if we drag up system setting just

04:39

here we need to tick beside this scanning reverse interval and now we can

04:46

come into this list here and I have not got anything set up for 400 millimeters

04:51

a second which is the speed we’re running and it is important that you

04:55

always set up one of these parameters for the speed that you’re going to run

04:59

at now in this particular instance we’re going to run at 400 millimeters a second

05:06

now there’s something here called reverse interval which is an offset that

05:10

we can apply at the moment we didn’t have anything set up so the machine is

05:15

doing its own thing what I’m going to do is now that I’ve set 400 millimeters a

05:20

second up I’m going to leave it at zero and do another test and see what result

05:25

we get the other thing that’s underneath here is called offset replay now you don’t

05:32

need to touch that at all if you play with that all it would do is move the

05:36

position of this square pattern around so we don’t want that to happen so we

05:42

leave it alone and there we are we can immediately see

05:45

the difference I’ve now set the offset to zero and the machine knows now that

05:50

there’s an offset of zero I’ve got a point oh 3 shift in there which

05:53

is one thousandth of an inch I don’t think it’s made any difference it’s not

Transcript for How to Prepare A Picture For Laser Engraving (Cont…)

06:00

made it better and it’s not really made it worse, if we use X unilateral it will

06:06

take twice as long but we’ll only get scan lines going in one direction so we

06:11

won’t experience this problem now bear in mind we’re looking for the perfect

06:16

dots to get the perfect dots we must have the focus set onto the surface as

06:24

perfectly as possible what we’re going to do is we’re going to check the focus

06:29

I think the focus on here should be about seven and a half so what I’m going

06:35

to do I’m going to set it to eight and a half

06:41

and then I’ll set it to seven-and-a-half

06:49

and then I’ll run down at six and a half now thing if you study those lines

06:55

carefully you can clearly see that the one in the middle is the thinnest line

07:01

which looks as though it’s probably pretty close to the theoretical point

07:08

one because the gap between those lines the pitch between those lines is 0.5 so

07:15

just a quick estimate visually says yeah we’re doing pretty damn good the problem

07:20

is we’re not going to get dots that size we’re going to get sausages that width

07:26

and that’s going to be a bit of a problem when we run at 400

07:30

millimetres a second but that’s all going to come later when we start doing

07:34

some some actual photographs and some dots I’ve got to go and set some scan

07:39

offsets for various other speeds you know how to do it now you don’t need to

07:44

see me doing it now what I’ve got here is a piece of card which is one

07:48

millimetre thick and if we look at it you’ll find that it’s not entirely flat

07:54

it’s got a little bit of a bow in the middle all I need is a couple of small

07:58

neodymium magnets in the middle here and that will hold that sheet completely

Transcript for How to Prepare A Picture For Laser Engraving (Cont…)

08:04

flat because we changed the thickness of the material set this back up to seven

08:09

and a half millimeters which is the ideal focus that we’re after so I’ve got

08:15

the air assist turned off in the programme because otherwise any fumes

08:18

that come up will get blown down and paint the whole thing a brown hue

08:22

okay now despite the fact that I normally use Photoshop I’m going to be using

08:27

RDWorks in its entirety some of the tools are very clunky in here but I think it

08:34

will be better if people don’t have to use Photoshop I’ve got a 300 PPI picture

08:40

here I’m going to use the bitmap handle you can see up here it

08:44

says 300 pixels per inch well one of the things that I can do is I can change the

08:49

resolution of the output here so we’ll change that to 150 and we’ll let RDWorks

08:58

do the change for us so I can apply that to the view

09:06

doesn’t look as though it’s changed much

09:12

now dithering is the thing that will turn it into black and white dots so

09:16

we’re going to be using dot graphic

09:20

and we’ll now apply that to view

09:26

now it makes a big difference

09:31

and that’s what we need to start with apply to source and okay and now we should

09:36

find that we’ve got when we click on there

09:41

dottie graphics we’re now go and set the parameters that green is just a border

09:50

an a4 border which is not going to print it’s just so that I can locate in the

09:55

bottom corner let’s just show you I’ve got my zero set down in this bottom

Transcript for How to Prepare A Picture For Laser Engraving (Cont…)

10:02

corner here that’s where we’re going to start and we’re going to start across

10:05

the bottom of the picture because I want the scanning to move up the picture so

10:10

that any fumes get drawn across the paper and any picture that’s produced

10:17

remains a nice clean smoke free picture behind it we’re going to set the speed

10:23

to 50 and we’re going to set the power down at 11 which is about the absolute

10:29

lowest that this machine will run at you take all the ticks away from here we’re

10:33

going to set the resolution to a hundred and fifty {pitch} point one six nine three

10:40

make the line interval match the pixels okay let’s see what we get now bear in

10:46

mind that that’s a dotty picture at a hundred and fifty pixels per inch I have

10:52

to say that’s come out substantially better than I expected

10:58

that’s almost newspaper quality yeah but you see lots of dots in there but what

11:04

we really ought to do now is go and have a look at this under the microscope to

11:07

see just what sort of quality we’ve got on these dots I mean I can see all sorts

11:12

of little details in here despite the fact that they’re dotty I can see in hairs. Quite remarkable actually

11:19

by looking at that streak of hair that runs across her forehead and well I

11:26

think generally when we look at this picture all we can see are fairly even

11:33

brown dots which is actually very good news because we haven’t got gradations

11:40

of brown they’re more or less all the same color

11:44

there are some black ones which are obviously where some of the pixels have

11:49

been doubled up but in general the single dots are all about the same color

11:55

now they’re slightly sausage-shaped but not terribly so maybe one and a half or

Transcript for How to Prepare A Picture For Laser Engraving (Cont…)

12:04

two to one ratio we’ve got just a little bit of gap between those lines which I

12:10

suppose is good in a way because it does mean to say that well we put the pitch

12:15

at point one six nine and I suppose the lines the burns are about point one just

12:23

over point one maybe so it does make sense that we’ve going to get one or two

12:27

gaps between those lines while doubling the resolution has done absolutely

12:33

nothing for us at all except take all the color out of the dots as you can see

12:40

right this is 50 millimeters a second so we have still got dots but the dots have

12:48

lost all their color and that’s because we have basically doubled the resolution

12:55

doubling the resolution for 150 to 300 has basically half the amount of burn

13:02

time for each dot I know it’s a rather strange description but it looks as

13:07

though we’re almost getting greyscale dots now these are our first two

13:13

pictures we’ve sat them side by side so that you can compare them closely now

13:18

there’s always a temptation when you’re doing this sort of work to rush off and

13:22

say ah yeah but we’ve got this we can we can we can make that picture a lot

13:27

better by increasing the resolution we can go faster we can get it done

13:32

quicker you know there are so many things that you could play with so many

13:37

factors but what I want to do is just stop you in your tracks for a minute and

13:42

say look let’s have a think about this don’t rush into it we know a lot of

13:48

information now let’s put that information together and see if we can

13:52

start sorting out how we can get better or not pictures this picture here was

13:59

done at a hundred and fifty dpi in both x and y although the picture is 150 dpi

Transcript for How to Prepare A Picture For Laser Engraving (Cont…)

14:06

in both directions it doesn’t mean to say that you have to

14:10

do it 150 dpi in both directions we can’t change the number of pixels in

14:16

this direction and we can’t change the number of pixels in that direction but

14:20

we can in this direction if we want to change the interval and we could

14:25

effectively miss out every other pixel line so we’ve only got half the

14:29

information while I was doing this I imagined possibly that I could get

14:35

better results by increasing the resolution from 150 pixels per inch

14:41

to 300 pixels per inch so in other words if I increase the resolution

14:46

of the picture I’d better get a better quality picture well I think you can see

14:52

for yourself that isn’t the case but why not because we’ve kept the speed the

14:57

same 50 millimeters a second the only difference is we have in fact changed

15:03

the Y pixels per inch so we’ve we’ve scanned half the information so let’s

15:10

just stop for a second and have a quick think about what we’ve done well we know

15:15

that a hundred and fifty pixels per inch which is what this was done at it’s

15:21

likely to look like this because at 50 millimeters a second we’ll likely get a

15:28

dot which is around about point one and slightly sausage-shaped

15:33

now the ideal dot would be point one but at 150 pixels per inch

15:40

each pixel is point 169 and their dots are only likely to be

15:46

point one wide therefore we’re going to get some white extra white between the

15:53

dots so in this picture as we saw we had we did have a small amount of separation

Transcript for How to Prepare A Picture For Laser Engraving (Cont…)

16:00

between the lines because we’ve looked at this piece here across this piece of

16:04

hair across here and we did see that we’ve got a small amount of white

16:08

between the pixels it probably wasn’t as much as I’ve shown here but this is the

16:15

principle that we’re basically operating on when we’re working with this picture

16:20

now when I decided to do this picture at 300 pixels per inch but I made a silly

16:27

decision to only go down in Y at a hundred and fifty pixels per inch let’s

16:32

analyze what I’ve done so in this particular case we’ve got a pixel size

16:38

of 0.0847 which is nearly 0.1 which is approximately the size that we thought

16:45

our dots were going to be so if we look at how they sit in this grid they sit in

16:52

there we’ve got the ability at fifty millimeters a second to burn probably

16:58

every single dot maybe not fully black because we’ve got half the amount of

17:03

time remember and half the amount of time means we’re less likely to burn the

17:09

whole strength of the dot so that may will be black and that will make that

17:15

may well be only half black a gray or in this particular instance a half brown

17:21

and so consequently even though we’re running at the same speed because we’ve

17:26

got half the amount of time for each one of these pixels we’re going to

17:31

automatically get a lighter picture so there’s a good logical reason why this

17:37

picture is much much lighter than that one even though technically it’s at a

17:43

finer resolution although I’ve drawn these as dots as I’ve demonstrated on

17:47

here they could be single dots with a space between them or they could be

17:52

joined up dots I’ll just leave that to your imagination. I know

17:57

they’re not the same size but that’s because I’ve drawn the same number of

Transcript for How to Prepare A Picture For Laser Engraving (Cont…)

18:02

pixels this is a 10 by 10 pixel block this is a 10 by 10 pixel block and this

18:09

is a 10 by 10 pixel block but it’s at different resolutions and you can

18:13

automatically see how the size has changed quite dramatically but of course

18:19

the one thing that doesn’t change dramatically is this thing here the dot

18:24

size is influenced by the power but we’re keeping the power very low at the

18:29

moment so I’m keeping the dot sizes all the same so that you can see this

18:34

massive comparison as you supposedly think you’re going to get a picture a

18:38

better picture by increasing the resolution now all you’re going to do is

18:44

put the same dot if you choose you could in this particular instance look you

18:50

could at 300 pixels per inch as we tried to you could just use half as many

18:57

pixels or if you go to 600 pixels per inch and try and do every single line

19:03

you’re going to get dots sitting on top of dots sitting on top of dots sitting

19:07

on top of dots and you’re gonna get a very dark burn now I know this is a fact

19:13

because I have actually experimented with them but what I’m saying is you

19:18

don’t need to experiment with them if you just stop and think about it look

19:23

we’re going to compare these two pictures now this is 150 pixels per inch

19:31

and this is 150 dots per inch this one is 150 pixels per inch with 150 dots per

19:41

inch in both x and y now this picture doesn’t have anything like that picture

19:45

why not well two reasons why not first of all I’ve increased the power from 11%

19:54

up to 15% so in terms of power this 11% is probably something like about 3 watts

Transcript for How to Prepare A Picture For Laser Engraving (Cont…)

20:03

and this 15% has jumped all the way up to probably something like about 14

20:09

watts so there’s a huge difference in the

20:13

power for a very small percentage gain you need good control of low power you

20:20

do not get good control of low power if you’ve got an eighty or a hundred or a

20:24

hundred and fifty watt tube in. Your best choice for engraving is going to be

20:30

somewhere in the region of a 40 or 50 watt tube it’s not your best choice for

20:35

cutting but it is your best choice for engraving now I’ve got a 60 watt tube in

20:40

this machine and I can just about get good results but I have to be very

20:44

careful at the bottom end here just pushing the power up from 3 watts to 14

20:50

watts has caused this pretty gross over burning but in addition to that to try

20:58

and compensate for the over burning look what I’ve done I’ve increased the speed

21:03

to 150 millimetres a second from 50 millimetres a second so there’s two or

21:09

three variable changes and it makes a gross difference in the quality of the

21:14

picture that you get just to sort of reinforce this situation that I’m

21:19

talking about here at 600 dots per inch here is a 600 dots per inch image and to

21:27

try and stop it over burning which as you can see it’s got lots of gingereness and

21:33

burning and smoke stuff and I can I can feel her eyes are very nearly burnt out

21:39

when I touch her hair it’s got a 3d feel to it because of the way in which it’s

21:45

burned into the picture here and in fact let me just stop a second yeah that’s

21:51

exactly as I remember her… to try and compensate for the extra power that I

21:56

put into it because at 600 dots per inch I thought well I need to go a little bit

Transcript for How to Prepare A Picture For Laser Engraving (Cont…)

22:01

more powerful I also went very very fast of 400 millimetres a second yeah it

22:07

still works but the problem is when we start looking at the dots in here and we

22:13

will go back and have a look at some of the dots in these in these images you

22:17

will see that we do not have dots they’ve disappeared what we’ve got are these

22:25

what I call greyscale splurges different levels of colour caused by the fact that

22:35

we have got insufficient time at 400 millimeters a second and insufficient

22:43

space because we’ve got 600 pixels per inch those two factors are working

22:48

together to make the time scale infinitesimally small for any single

22:55

pixel so to try and get the pixels to burn you put more power in but that

23:01

means that when you do get blocks of pixels that are joined together this

23:06

power takes over and you get terrible burning so trying to find a compromise

23:12

you say right okay 600 pixels per inch we run 600 pixels per inch resolution

23:19

down the page as well and we’ll run slower to try and get a bit more color

23:25

into it but we’ll put less power into it at 12% it still doesn’t work at the end

23:33

of the day the most balanced picture that we can come up with is one made up

23:39

of dots these are not dots as you will see when we look at them under the

23:44

microscope the crispest picture is that which is done slowest 50 millimeters a

23:51

second and a very coarse resolution but the point that I’m trying to make here

23:56

is with photographs running fast running powerful and running with high

Transcript for How to Prepare A Picture For Laser Engraving (Cont…)

24:02

resolutions is not going to get you a good quality picture you’re going to get

24:07

your best results probably down at low resolutions and low speeds it’s probably

24:13

better to experiment with maybe 60 or 70 millimeters a second trying to keep the

24:19

dot as round as possible but increase the resolution maybe a

24:24

little bit up to 200 now the one thing that you must not forget is that your

24:30

lens has got a theoretical spot size let’s just look the best spot size that

24:37

we can think of which is a one and a half inch lens with

24:41

a spot size of point zero seven five millimeters well put it another way

24:52

point zero zero three inches now that means that basically the best that we’re

25:00

going to get if we put these dots together like this is three hundred and

25:07

thirty three pixels per inch anything above 300 pixels per inch resolution

25:17

picture and really I think you’re wasting your time now do not lose sight

25:23

of this fact because this is fundamental and the other thing that you must

25:28

remember is this is a theoretical spot size and when you come to put it on your

25:33

material whatever that material is if you do a test burn you may well find

25:39

that your spot size is not as you think that size but it’s actually that size

25:43

and you could be down quite easily at a hundred and fifty P P I for your picture

25:52

putting more than 150 PPI into the picture it’s not going to get you

25:57

anywhere now if you’re after an art poster this one looks quite a nice soft

Transcript for How to Prepare A Picture For Laser Engraving (Cont…)

26:05

dreamy effect hazy soft focus but if you want a good creation then you’re looking

26:14

at something like this where the dots are actually crisp and clear and it’s

26:20

your eye that gets fooled this is that curl across her forehead that I look at

26:25

as a reference every time and we can see clearly some lovely brown lines that run

26:31

across there and we’ve got separation between the lines so that means we’ve

26:35

got our scan lines which are actually quite well defined but the gaps between

26:40

them are because this is only done at a hundred and fifty dots per inch in the Y

26:45

direction and so these are exactly the same line separations that we saw in our

26:50

very first crisp clear

26:52

dot image the difference is that this is not a clean crisp dot image this is a pseudo

27:00

grayscale as I keep calling it because look with all these shades of brown in

27:05

the background where different amounts of time different amounts of power are

27:10

causing different colored dots so yeah this is not a grayscale picture because

27:17

we are using the same power Max and min and grayscale pictures come from using

27:23

different power Max and min so this has been created by a completely different

27:29

mechanism but even though it’s not part of this session I have a little bit of

27:37

curiosity that needs to be satisfied so I’ve imported this 600 PPI picture again

27:43

and we will just set up a different set of parameters speed same as it was

27:50

before 400 millimeters a second power well this time the minimum power that we

27:57

ever found that we could use was 11% and the maximum power that we used was 40%

Transcript for How to Prepare A Picture For Laser Engraving (Cont…)

28:04

now we need to come down to here and this time we’re going to output direct

28:11

and basically what that’s going to do it’s going to give us grayscale

28:15

engraving now I’m going to set the interval exactly the same as it was for

28:19

the last picture which is 150 dots per inch in the Y direction which is point

28:24

one six nine three well we can clearly see the beam is on virtually

28:31

continuously and stable the whole time except when it turns off right at the

28:36

end of the stroke and then back on today yeah we’ve only got about a 10 percent

28:40

variation in power across there because in the end I had to set it to between 11

28:45

and 20 percent because otherwise I was just burning through the picture so I

28:51

obviously haven’t got the correct parameters here but these are parameters

28:55

similar to the last picture that we created with dotting and this is really

29:00

all the comparison is about it’s quite entrancing isn’t to watch I’ve been

29:06

dancing around

29:13

ok now the one thing I keep meaning to say when we’re looking at this

29:16

picture that mauve is not the laser beam that mauve is just ionised nitrogen

29:26

it’s the powerhouse that drives the carbon dioxide to go into lasing mode so

29:34

just because you see that beam there does not mean to say you’re necessarily

29:37

going to get power out of your laser because if there’s no carbon dioxide

29:42

left in your tube you’ll get no power out but you will be able to see that

29:47

lovely mauve beam in fact that beam might go slightly paler and whiter as it gets

29:52

towards the end of its life because there’s more nitrous oxide from the from

29:58

the free oxygen that’s been released from the carbon dioxide when it’s broken

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30:02

down into carbon monoxide and oxygen so just bear that in mind the mauve is a very

30:09

good sign that your power supply is working but it’s not an absolute certain

30:12

sign that you’re getting power out at the end of the tube. What you’ve just been

30:16

watching is me trying to produce something called a grayscale photograph

30:21

when this picture started off life originally it was full of color the

30:25

first thing that RDWorks did to it was remove the colour and when the colour

30:30

is removed it left a black-and-white picture which is basically a mixture of

30:36

shades of grey and that was what we have tried to simulate here with this dot

30:42

picture we’ve created the same sort of thing we’ve fooled the eye into thinking they are

30:47

Shades of colour on that picture but there

30:50

are not we’ve only got black dots and nothing it’s just the different

30:55

densities of those dots are fooling your eye into thinking this is a photograph

30:59

now as we’ve already explained the way in which the laser produces this picture

31:03

is very simple it takes the power parameter 11% and it sets it at a fixed

31:09

value of 11% the dot every time we need a dot the power switches on and we

31:17

produce a dot and then it switches off then it travels along to the next dot or

31:22

in this instance group of dots and then it switches off dot dot group of dots

31:28

there is a very powerful function built into RDWorks it has the ability to

31:35

look at a grayscale picture and sort out every single pixel into a gray value now

31:44

the value of gray runs from white at 255 down to black at zero every one of those

31:52

shades of gray is given a power value and then this is where the clever bit

31:58

takes place when you run your program the first thing that happens is the beam

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32:04

switches on and it stays on for the whole of your program but every scan

32:13

line that goes across looks like this it starts off zero and then it looks at the

32:20

very first pixel and says oh yes that’s a mid gray that’s halfway up the scale

32:25

and so it produces a pixel value like that and then it looks at the next pixel

32:31

and says oh that’s nearly white white is not much power at all so we’ll turn the

32:35

power off then the next pixel is a slightly heavier shade of gray and then

32:39

a lesser shade of gray and as we go across every pixel

32:49

has a varying power obviously if you start running the machine too fast

32:54

ie 600 pixels per inch or at very high speed the machine is just not capable of

33:02

keeping up with your requirements even though the requirements are there the

33:08

power supply and the laser just cannot do it this is how we basically would

33:13

attempt to produce my grayscale photograph now obviously I can only hope

33:18

to perform something like this on a piece of organic material because with a

33:22

piece of organic material I can get different shades of brown when it comes

33:27

to a non organic material such as acrylic in this instance or glass or

33:32

stone or slate or granite or something like that then the only choice that

33:38

you’ve got is a colored dot of one shade or nothing

33:43

so there is no gradation that you can use with solid materials now how

33:50

successful were well there we are the answer is not very it’s a horrible fuzzy

33:59

picture yes it’s grayscale but no there is no definition in it at all so we were

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34:07

using the same resolution base picture 600 dots per inch we were using the same

34:12

scanning rate of a hundred and fifty dots per inch down the page we were

34:17

taking about a quarter of the information but that isn’t the reason

34:20

why it’s fuzzy because when we did it using the dot method exactly the same

34:26

picture looks like this so there is a huge difference between using dots and

34:33

using gray scale basically grayscale is not for producing grayscale pictures

34:39

it’s another completely different function that you can use grayscale for

34:44

it’s for 3d carving and we will get on to that subject which is a fascinating

34:50

subject in a future session the only way that you’re going to get a picture of

34:55

any sort onto a material is with the dot process now you don’t always

35:01

see the dots this is a smeared dot picture it isn’t a proper dot picture

35:07

this is a proper dot picture and you can see that there’s an element of crispness

35:12

about this that there is not there as soon as you start running at different

35:16

speeds and different different resolutions you could smear the dots

35:22

overlap the dots overlap the powers and you get all sorts of interesting

35:28

pictures some of them very soft focus something like this

35:33

no dithering at all all it is it’s basically a black-and-white picture now

35:39

here we have a completely different material this is anodized aluminium and

35:42

you see that we’ve managed to get a photograph down onto the surface it’s

35:47

only again a binary surface white and the background colour in this instance

35:53

we’ve got a silver background so you would expect that probably a silver

35:56

background wouldn’t show through at all but as you can see we get a sufficiently

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36:00

good contrast to see quite a reasonable photograph I will point out to you two

36:04

things first of all 80 millimetres a second very slow speed and 11% power

36:11

very low power now look what happens when I changed just 10% look at the

36:17

quality difference in the in the image again I’m reinforcing that control of

36:21

low power is an essential thing when you come to engraving well we’ve banged on

36:27

enough about dots and photographs and I think you’ve now got enough information

36:32

in your toolbox to go away and play for yourself so for the final part of this

36:38

session what I’m going to do is show you a real project that I had to carry out

36:42

for a friend of mine so it involves Photoshop I’m afraid or some sort of

36:49

photographic processing software because quite often you cannot get the correct

36:55

image that you’re looking for down onto the medium that you want to apply it to

37:00

now this particular project is basically going out of my comfort zone I’m gonna

37:05

have to go into Photoshop which okay I know my way around Photoshop but but I

37:10

am NOT a graphic artist in fact I’m not any sort of artist

37:14

except the up against the wall type so you’ll have to forgive me for some of

37:19

the liberties that I might take I’m an engineer not an artist and I make no

37:24

excuses for that at all so I hope that what we’re now going to see is a

37:27

practical demonstration of all the elements coming together that we’ve been

37:32

learning about I’ve got a real job to do for someone a friend of mine who has

37:37

asked me to immortalize her dog on some coasters as you can see this is not

37:42

exactly the best picture in the world to work with it’s not a studio quality

37:46

picture so somehow I’ve got to get the essential qualities of this dog’s face

37:52

onto a piece of wood now I’m not going to take you through every single step in

37:57

detail but I am going to show the outline of what I’m going to do to

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38:01

manipulate this picture so the first thing I’ve got to do is to physically

38:05

crop the head fairly tightly so that I don’t get too much of that bright red

38:11

coat in the background now let’s bring the picture up to a decent size so we

38:16

can see what we’re working with o M G is your immediate reaction look at the

38:21

state of his tongue saliva mud so we’ll choose that area there and there we’ll

38:27

start working away to try and put some pink once this goes into grayscale

38:34

it’ll be a shade of gray well that’s not a perfect tongue but at least it’s

38:39

better than it was so we then used the clone stamp to copy

38:45

the colors off of his muzzle here and try and get rid of those mud spots we

38:54

can do this with a lasso tool we can work our way around his head

39:01

approximately

39:10

so now we’ve got another layer which is

39:16

that layer there and you can see we’ve probably removed a large part of the

39:24

background we also removed some of his tongue but this is not what I finished

39:29

up with now the biggest problem that we’ve got here is if we take a look at

39:34

image adjustments we can check brightness and contrast and we what

39:40

we’re trying to do is to bring his eye up this eye here is not very prominent

39:50

even when I push the contrast up which is what I should need to do

39:59

that eye is not very distinct I’m going to capture this eye here

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40:11

rather carefully

40:19

edit copy edit

40:25

paste and you say well you haven’t done anything

40:30

well yes I have because if I select this layer and I now use the pointer look I

40:39

can pick up his eye

40:44

and I can now put that over there

40:49

so now I’ve got two fairly bright eyes to work with the other thing that I’ve

40:55

got to do is because I know that when these eyes are on wood they will not

41:04

show up against this black dark background and so consequently what I’m

41:12

going to do I’m going to choose some rather hideous color like that and I’m

41:19

going to turn him into a werewolf now you definitely wouldn’t want to meet

41:23

that dog on a dark on a dark night would you and so you can see how I had to

41:32

basically manipulate that oh one other thing I didn’t mention which I had to do

41:38

I had to take a clone stamp and I had to clone these little frilly bits of the

41:45

tops of his ears here and I had to put them on the crown of his head because

41:50

there was no definition between this white section here and the background so

41:56

although this hair isn’t real it just gives the impression it delineates the

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42:02

outside of his head so you can see if you look at that in detail it’s not

42:05

necessarily a very good quality picture okay now when we import that picture

42:11

into RDWorks it looks pretty scary doesn’t it so the first thing we’re

42:16

going to do with that picture is make it ninety five millimeters and then I’m

42:22

going to create a square 100 and then we’re gonna put that square around the

42:32

outside of the image and we’ll make that into blue

42:35

so the bitmap is black and we’re going to have a go at cutting that in a minute

42:45

at about a hundred and I think we’ll probably set the power to just a little

42:54

bit over the minimum I think that 12% is pretty good blowing no we’ll check the

43:01

cut speed the cut speed is about five millimeters a second because this is

43:07

going to be done out of probably five millimeter marine ply probably 67

43:17

percent 67 percent which is about as high as my tube will go okay so now

43:23

let’s go back to the picture itself

43:28

bitmap handle and you can see we’ve got a resolution here of over a thousand

43:38

think we’ll set that to 200 we’ll push the boundaries of what we’ve just

43:43

discovered and then we will do dither and we’ll set it as dot graphics we

43:52

could play with the contrast and the but at the moment I think it probably looks

43:58

reasonable so we say apply to view and immediately we lose all the detail

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44:05

so now we can play with these colors here contrast and brightness apply to

44:13

view

44:17

and there we go we can get some of the detail back here’s you see now that

44:21

looks like a reasonably balanced view so we can say apply to source now and then

44:27

when we look at this there we go

44:34

and this time you can see the smoke being pulled away nicely towards the

44:38

back of the machine where it’s extracted down the slots

44:47

well I’ve now put the cover down so that we get a good jet of air flushing across

44:51

the surface there and as you can see you can probably see hardly any smoke at all

44:56

it’s all being dragged backwards really really quickly

45:11

now what you’re seeing at the moment is a cut taking place where the air assists

45:16

has actually turned on automatically on its own

45:22

now if we take a look at the quality of that cut you can see that there is

45:25

absolutely no smoke burning on there at all except

45:33

the only hint of browning we’ve got is at the very very start point there and

45:38

the very very finish point but everywhere else is absolutely clean

45:45

and the reason why we’ve got a lovely smoke-free finish here is because the

45:50

smoke is passing all the way through this job

45:52

there’s nothing hitting the top surface it’s all going down underneath then is

45:57

either being drawn away by the airflow underneath or has been condensed on this

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46:02

surface here as you can see leaving a Hobby horrible sticky goo behind

46:07

now that’s another reason why I’m using a solid steel plate because when this

46:11

job is over all I’m going to do is to wipe that plate clean if I had been

46:15

using a honeycomb table I can’t clean the honeycomb table as you can see all

46:22

this muck on here look it’s all horrible Browns sticky muck that’s the stuff that

46:25

would have gone on to the top of your cut and onto the top of your job had you

46:31

have had the air assist on while you were engraving and that’s the stuff that

46:34

actually paints the surface of your wood Brown you don’t want it you want to get

46:40

rid of it before you blow it back down onto the job so basically for air assist you

46:45

only need it for cutting and you want to blow all your muck out of the bottom of

46:49

the job but for good engraving you want to let it drift up into the air and get

46:55

it sucked away and not blown back onto the surface of the job

46:59

See all this brown muck here? Well sometimes you can get away with something as simple and benign as a

47:04

white vinegar so let’s give that a try it really depends on the debris itself

47:16

now because that’s a natural wood and that’s probably just a normal resin it

47:21

came off fairly easily with white vinegar but here we’ve got

47:28

some acetone now obviously it’s not the sort of thing that you would let

47:32

kids play with and you would normally have rubber gloves on or plastic gloves

47:37

so that you don’t take the oil out of your skin

47:41

but I’m afraid at my age I’ve got a very tough skin I’ve been involved in

47:47

engineering for many years

47:54

for just a few seconds work it’s not a major problem but if I was handling this

47:59

stuff all day my skin would literally dry and crack so it’s not the sort of

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48:04

thing you normally use without gloves now here are our coasters and you may

48:08

possibly spot that there are two at the back look slightly softer they’re not

48:15

quite as crisp as these when you look at them with the light across them and

48:19

that’s because these are coasters and they are going to be subjected to

48:24

spillage whether it be beer wine whiskey something is going to be spilt on these

48:30

you can be assured of it if it’s me well it’s got to be black cock here I’ve got

48:35

some just natural beeswax this is called bright way it’s mainly beeswax with a

48:41

sort a little bit of sort of something like white spirits in it to make it

48:44

slightly soft it’s not hard beeswax as you can see in here it’s a sort of a a

48:50

slightly soft creamy mixture but it is a natural material and it sinks in to the

48:58

wood and so what I do with these I protect the wood

49:04

when you first put it on you think oh my goodness what’s happening here we’re

49:07

gonna fill in all the engraving

49:12

but because it is a wax and oils what tends to happen is over a few minutes

49:17

maybe 20 minutes half an hour you’ll find the the wax actually sinks into the

49:24

wood and here we are look

49:28

when you first do it it looks pretty horrendous but just be patient and all

49:34

will come good in the end paint the edges which sells any coloration that

49:40

may be wanting to come off it seals it in and then we do the backs as well, so just paint

49:47

it on with a brush don’t put it on with cloth because cloth will leave lint and

49:51

various other pieces of white in your engraving yeah it feels so real now I do

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50:00

hope that that lasts practical demonstration has brought the whole

50:05

thing together now it was no cheating with that at all

50:08

there was no practice I went straight in with a resolution I went straight in

50:13

with a speed I went straight in with a power and we got excellent results and

50:18

that’s what I hope this session has given you confidence to dive straight in

50:24

with a set of good maybe not perfect but good parameters so until the next time

50:32

Cheerio

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