40 – Photo Laser Engraving Anodized Aluminium – Part 2 (52:09)

0:15Welcome to another Lightblade Learning Lab. Today we’re going to carry on and do the second part

0:22of our anodised aluminium photo engraving. Now we finished up the last session

0:29basically talking about energy density time and the amount of damage that we

0:34were doing to the surface of this material now we were trying to put just enough energy in to extract all the dye and without damaging the material

0:46underneath now I did mention last time that the gold anodized part that I had

0:52was likely to have the very thin anodized surface and I have done a

0:58little bit more work on this machine and I’ve got some examples here to show you

1:05exactly what I mean I was trying to get the detail around these teeth here and this one was done at 200 pixels per inch 15 percent power

1:16and 50 millimeters a second well 15 percent power may just have been in the

1:22solid power region I was using common mode for this and at 200 pixels per inch

1:2915 percent power I obviously had way too much power because look I’ve been graved

1:36right through the white and I’m into the gray which is the raw aluminium underneath you can just say a hint of the white down at the bottom here in

1:45places this one here was still done at 15% 200 millimeters a second exactly the

1:51same power settings but what I did on this one was to increase the resolution

1:57to a thousand pixels per inch now obviously a thousand pixels per inch

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

2:03gives me a little less time per pixel and as you can see I have not burnt

2:09through as much on this one but then I changed over to first of all I reduced

2:15the power to 12% as opposed to 15% and the speed remained at 200 millimeters a

2:20second so the only difference between that and that is 3% power

2:27I dropped the power down definitely into the pre zone so I had a pulsing power and I think as you can see if you look

2:35carefully here we’ve got very good distinct teeth on this skull and the

2:43quality of this picture is pretty good and this is a thousand PPI but of course

2:48this is not a photograph this is a slightly toned

2:56which is not quite the same as a photograph which is a lot more demanding and as you can see there’s lots of untouched spaces in between here whereas

3:06on a photograph we’re going to dot across the whole section in some way to produce shades of gray this material was pretty thin on its anodizing just a few

3:18more watts of power and you can damage right through to the aluminium the raw aluminium underneath now spent a long time thinking about why it is possible

3:27to get such high resolution on this material whereas I think anything else

3:33it would be nearly impossible to withstand this big change of power and

3:38speed an actual energy density per dot per time and remain constant color

3:46there’s something unique about aluminium oxide okay let’s take a look at the

3:53theory behind what we’re trying to do today because what I’ve just about to

3:58show you proves that we are totally going to fail now the best case dots that we’re likely to be able to get from the work that we’ve done so far and this

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

4:08is very optimistic not 0.1 millimeters diameter we’re talking about putting

4:17down a grid adults at a thousand PPI excuse my very

4:27accurate drawing but the essence of it is that each one of these pixels and here we have a pixel is at a thousand PPI the pixels are going to be not 0.025

4:45millimeters 0.025 in that direction so that’s the increment that we shall

4:53select to do our program with hmm and that’s the resolution of the dots that

4:58we shall have equals a thousand P P PI

5:06okay well let’s take a look at our first dot that’s 0.025 so that means if this

5:13is point one we get four pixels in the dot not one dot on a pixel so that means

5:22that once we put our first dot on here like this and bear in mind it’s four

5:27pixels one two three four pixels wide and it’s also one two three four pixels

5:34high so a dot effectively is about that sort of size and that’s the size of our

5:42pixel so when we move along to the next pixel this circle will only move along

5:50to here and then we move along to the next pixel etc so every time we move

5:59along a pixel we’re going to move along the dot 1/4 of a dot so that we’re never

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

6:05going to see separate dots so in producing this block along here what we’re doing the second time we’re burning 3/4 of the same block again and

6:15then we move along and it’s burned again so every time we move along four pixels

6:21we’ve got four burns on the same area so this fourth pixel along here will it be

6:28burned four times before we move into clear space and now we get

6:34exactly the same thing happening in this direction as well so we shall get four burns in this direction on that same pixel as we move down so we’re getting a

6:46huge amount of over burning now if we were doing this in wood or paper or card

6:55or any organic material where the burning color is related to the number

7:02of times that you burn the same area or if you like the amount of energy total

7:07energy that you’ve put into that one area you will get a darker and darker color and you will get more and more cutting or burning erosion taking place

7:18more damage we’ve already seen and we can interpolate that the sublimation or

7:25vaporization point for this die is somewhere in the region of may be anywhere between 150 and 250 degrees C it’s not very high before this dye will

7:38actually vaporize off but this white material in the background the aluminium

7:44oxide is actually not melting until we get to about 2100 degrees C what you can

7:52really imagine is that we can over burn this material many many times and it

8:00will still not get to 2100 degrees C so basically the background material is

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

8:06heat resistant unless it’s very very thin as we found in the case of the gold

8:12anodizing the success of this is that we can still have our point one resolution

8:18which really means we’re talking about a picture resolution of about 254 PPI

8:25theoretically that’s the resolution that we’re going to be producing even though we’ve got a thousand PPI picture and this is where the problem comes what are

8:36we going to finish up with 254 pixels per inch or a thousand pixels per inch when we’ve overwritten all of this we don’t get definitely clean thousand

8:47PPI pictures what we do get is a phenomenal result and I don’t know how

8:53that phenomenal result comes about other than the fact that the 254 PPI resolution picture is still pretty high resolution well I think that’s enough

9:02pessimism we’ve established that over burning this material is not going to produce variation in the quality in the background which is one really good

9:12piece of news that I’m prepared to hang on to optimistically so let’s get on

9:17with the picture that we’re going to modify and we’ll bring it back here and we will have a go at producing a miracle my daughter has asked me to manufacture

9:26a bespoke gift for a friend of hers that owns this horse and so we’re going to

9:31prepare this current photograph into a black and white image that we can put down onto anodized aluminium and we’re going to step through the process of

9:41doing that now I happen to be using Photoshop but there are two equally good

9:47free open source packages that you can download one of them is called

9:53photoscape and the other is called GIMP – GIM pee – I’m going to take you

10:01through the mechanical process of manipulating this picture I have to

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

10:06stress I am NOT a graphic artist I have almost zero artistic skills but I

10:13do understand the mechanics of how this software works now it’ll be down to your artistic skills and abilities to create something which will be different and

10:23better than what I’m going to show you but the procedure will be the same so

10:29first thing is to crop the picture to make it into something that is fairly

10:34well balanced now what I’ve done there I’ve cropped the head let’s just pull the nose in pull it tight to the nose pull it a little bit tighter to the chin

10:44save yourselves a lot of work it’s reasonably tight on the ears we’ve got rid of the green tree that’s in the background there we can pull it up just

10:51a shade more and crop what we’ve got on the right-hand side here that’s where I

10:57want to – now this picture on the right hand side here might look a bit like a grayscale photograph but if we go and

11:05have a look at it closely it’s not the grayscale photograph it’s actually a binary image and when I say binary it’s made of four black dots on a white

11:14background the first thing I’m going to do with this picture is to look at its

11:20resolution so its resolution is 96 pixels per inch now I want to do two

11:30things first of all I want to because of the material that I’m going to be using I want to suppress the height to 120 millimetres or 12 centimeters now I also

11:43want to change the resolution from 96 up to a thousand now that’s an unheard-of

11:52resolution for engraving images with a laser machine it’s illogical to be able

12:01to get a good picture at a resolution of a thousand pixels per inch but trust me

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

12:07it works I have no idea how it works I’ve done an

12:13in-depth investigation into this in Rd Works Learning Lab 130 if you want to go and search that out so here we created our thousand pixel per inch picture so

12:24the next thing we’re going to do is to try and get rid of the background and we’ll do that quite simply with the paint bucket tool before we use the

12:35paint bucket tool what we’re going to do is going to set the background color and we’re going to set it to pure white so if you look at these numbers down here

12:44RGB red green blue the mixture of red green blue 255 255 255 will give us pure

12:52white so we’re going to take that pure white and we’re going to set the

12:59tolerance up here – we haven’t got anything that’s nearly white here

13:04they’re all black gray brown yep so we can use quite high

13:12tolerance and we can pour the paint white into this background and there we

13:20go we’ve removed most of the background there’s a little bit just up here between the ears we could back up one we could change that to maybe 40% let’s

13:32just try 40% and pour the paint in the game yes take a little bit more away I

13:42don’t think it’s going to affect us at all well it has affected us down here in

13:54the mouth area so we shall have to back off the Paint Bucket down in the area it

14:02hasn’t affected us around the head to choose somewhere down here well that’s

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

14:07not too bad that’s taken most of it out without destroying anything to do with the brown and the black nope that’s not good take that one out but everything

14:23else is okay well we’ll just get rid of that

14:34a koala has not removed all the background but it’s taken most of the hard work away now we’ve got to go through a pretty tedious task choose a

14:44suitable size brush and it’ll be down to you to decide what you want but I would

14:50say you make it a fuzzy brush with a feathering on the edge and that way you

14:59can creep up on the edge and you can fairly accurately decide how much you

15:05want to trim off your edges and the soft edges will probably look better than

15:16sharp crisp edges and you can take all the rubbish out the background as well

15:22now I did say that this is going to be quite a tedious task which I’m going to

15:28skip so I’m going to work I’m going to carry on working with my messy picture just to demonstrate the various stages that you need to go through so once

15:38you’ve cleaned up your picture you need to then go back to the mode now

15:45different bits of software will describe this differently in my particular instance it’s pretty simple for me to just call for greyscale and it says do I

15:54want to discard the colour information well obviously I do and so there we go

16:00as an engineer it’s a pretty flat picture there isn’t much contrast to

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

16:07define the muscle structure that’s going to look very flat as well if we try and

16:14print that an exaggeration is one of the keys to finishing up with a half

16:20reasonable picture so how do we start modifying this picture well we go to

16:25image and there are all sorts of adjustments that you can use let me just show you one for example brightness and contrast now the problem with brightness

16:34and contrast is it acts on the whole of the picture in one go right now yeah

16:43you can fiddle around with it a bit but it doesn’t allow you to go in and

16:49manipulate the different levels of gray now what do I mean by the different

16:55levels of gray let’s just cancel that put it back to normal you’ll find that

17:02somewhere in your software you’ll have another set of figures called levels so

17:08you’ll have another adjustment called levels and if we take a look at levels

17:14what it will tell you is the amount of black and the amount of white in your

17:19picture now we’ve got a huge amount of white in this picture as you can see and that shows up here look we’ve got huge amounts of white if we want to play with

17:27this slider here for instance I can achieve much the same sort of result as I can with the brightness and contrast control but you can see it’s happening

17:35over the whole of the picture okay now at the moment it’s not affecting the

17:40white because the white is what it is it’s white it’s not affected by contrast

17:46but I can play with that by messing around with this other slider I can

17:51change the color of the background as well which I don’t want to do so this again is a very gross control and fairly crude control mechanism it shows you

18:02what’s in the content that shows you the content of the picture of gray levels in the picture but it doesn’t allow you to modify them okay let’s look at another

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

18:10feature generally you’ll find something else called curves and you’ll find a

18:17graph that looks like this now this is a very powerful feature which is probably

18:23the one feature that you need to learn to just play with a little bit now let’s go into the middle here and just pull it and push it and you can see we’ve

18:35achieved a sort of a an overall change it’s affecting the whole of the picture

18:45and let’s now put a little dot down there at the bottom which is we look there’s the white end of the scale and let’s just manipulate and pull that dot

18:55around a little bit now a lot

19:06now the further I push that dot up the scale the more exaggerated some of the

19:13changes become so we don’t need huge changes so let’s put it towards the

19:19bottom I will pull it a little bit towards the black let’s go to the top

19:29end the black end of the scale and let’s take some of the blackness away one of

19:35the areas I may be likely to look at is just here on the neck you can see these

19:41wrinkles skin wrinkles on the neck now that’s a good place to look for the way

19:48in which you’re changing the detail and there we go look you can see with all of a sudden by doing that we’ve pulled out those lines on the neck we’ve made the

20:01face quite light up here now so can we maybe change it a little bit and put

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

20:07some color back into the forage without losing those lines we’ve got the ability

20:16with this graph to amplify or decrease different gray scale sections of the

20:25picture so sometimes you need more dots in to hold the line where you want it

20:31and just exaggerate some other features so you can play for hours with this particular control but this is the key control that you want to mess around

20:40with so say okay look if we just zoom in on

20:46the eye you’ll see that there is a highlight in the eye and there’s also a

20:53little bit of white around the edge of the eye now there is another tool that you can mess around with here which is called a Dodge tool and that will allow

21:03you to especially as we’ve got this set up to white is to exaggerate

21:21a little bit of highlight in the eye

21:29they were just reinforced this little bit of white down in the corner here and

21:38this little bit of reflection off the the eyelid itself didn’t have to be too

21:47fussy because we’re working at a huge magnification here then we’ll put this

21:57back to full view there we go all of a sudden we’ve created some character in

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

22:06the eye and the eyes are one of the most important features in any picture it’s

22:11the one thing that people tend to look at first so concentrate on the quality

22:16of the eye and at this stage I would say save your work because the next stage

22:22you won’t be able to easily undo you might want to go back and change it so

22:29let’s take a look at image again mode we’re already working in greyscale and

22:34greyscale is not the same as black and white if we zoom in on here you’ll see

22:41that there aren’t any dots just a gradual transition from one color gray

22:48to another okay let’s now do one of the final steps

22:55which is to convert it into a bitmap we started off with a thousand pixels per inch and we finish up with a thousand pixels per inch

23:03now the good news is it doesn’t look any different but when we zoom in on it

23:08that’s what your horse is now comprised of just a series of black dots varying

23:15in density and it’s the varying density that gives the impression of grayscale

23:21now at this stage we’ve got a nice clean picture I would recommend you do this

23:27did ring in your software package rather than in our D works our D works can be a

23:35bit crude about how it does the dithering okay so let’s save that now and we can now move on to our D works do the next stages okay so we’ve now

23:46imported our picture into our D works and we really don’t need to do too much

23:51to it here we need to add a bitmap handle to the file and we should find

23:59that the resolution is already a thousand normally with your laser cutter you will be burning black marks on to a a white or a light background so as

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

24:12normally we would have to burn the black into the picture we’re actually burning the white into the picture and that means that we need

24:21to use this control here which is invert to color apply to view we need to

24:29produce a negative now let’s rather strange so when we look at this in the

24:35viewer yeah it’s a little bit exaggerated but it gives you the correct impression of what we’re actually likely to see on the page so the only thing

24:44left to do really is to put a little bit of a frame around this and we’ll do that

24:50by putting the lock on to start with then we will produce a square we we’re

24:59currently working on a black layer so we’ll change this to a blue layer to

25:05start with and we’ll draw our square where it’s not square what we’re going

25:12to do is line up the top left-hand corner and the bottom right-hand corner

25:18we’ll put handles on our blue square or a blue rectangle and we’ll change it to

25:29110 percent 1 1 0 we’ll take it off by 10 percent like that so now I’ve got the

25:37blue frame now to make sure that it looks nice and symmetrical all the way around we’ll just jiggle it with our horizontal

25:49and vertical alignment tools and there we go you saw it just jiggle into the shape so it’s nice and symmetrically now and what we’re going to do gonna

25:59make that second layer there a cut layer speed of 100 blowing yes processing mode

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

26:12cut to power we’ll put that up to 40 I think than 40 okay now the only thing

26:28that’s missing is the name so we’ll put a name on there for the horse and we do

26:35that in text Piron I’m using lucida calligraphy and five-millimeter yeah that’ll do

26:58so I just popped at the top there and we’ll change that to a yeah we’ll change

27:08it to a red layer and we’ll put that scanned 100 millimeters the second

27:17sounds good blowing yes scan mode power 40 hundred

27:25that should do all right they should be the same as cutting so that should produce a nice white piece of text at the top there and the resolution point

27:35one will be good enough because we’re only producing text it doesn’t matter what that resolution is okay now what we haven’t done is set the parameters

27:43whoops let’s turn that bitmap there the horse back to black layer okay

27:57and we’ll promote that to the top fact the pull of red down the blue down and

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

28:11we need to set the parameters for the black bitmap for the for the horse now

28:19um I’m really lost for words here because we got to run this at 250

28:25millimeters a second now that’s unheard of for producing sort

28:32of like photo scanning all experience I’ve had so far says this is ridiculous

28:38you can’t go that fast and produce good dots but having just recently

28:43experimented with this anodized aluminium yes you can under certain

28:50special circumstances which I’m going to describe to you

28:58so 250 millimeters a second blowing yes scanning power 50% power now that’s

29:08horrendous amount of power to produce a small dot but wait a second and all

29:18would become a little bit clearer now what we need to do then is to set the

29:23increment this interval value and we do that by calculating what the pitch of a

29:32thousand pixels per inch is and the answer to that question is 25.4 which is

29:40the number of millimeters in an inch so it’s twenty five point four divided by a

29:46thousand and the answer to three decimal places is 0.025 and that’s about as fine

29:56a resolution as your machine can achieve now the other thing that I’ve done as

30:03I’ve put the location point down at the bottom and I’ve done that by going to

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

30:09config dot sis settings and if you’ll notice look I’ve put the starting point for the head the centre at the bottom and that’s just to

30:19make it easy to locate the center of the picture on the center of my blank closed

30:30now the other thing that you’ll notice is I’ve already got parameters set in here for my scanning reverse interval now we’ve tackled this problem before

30:40about lines that do not line up if you run from left to right and right to left

30:46so this is a correction factor which should deal with that problem on this

30:52machine so we should save this program now well it’s such a big file I’ve had

31:02to put it down and reformat the memory in here and it’s taken probably about 20

31:09minutes to load this load this file into the machine I’ll set my material up

31:17square to the front edge of the machine and as you can probably see on here I

31:22put a mark for the center point now it’s difficult to line it up with my speed

31:28set high as it is so I’m just going to change the speed to 10 millimeters a

31:35second and all of a sudden becomes dead simple to perfectly line that up

31:44and then I’ll set the origin there and do a frame

31:54that’s good 250 millimeters a second and a thousand pixels per inch at 40% and

32:0240%

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

32:12I’ve still got this running in special mode like in 20 minutes and I’m the folk halfway through

32:33and here are those detailed creases on the neck look

32:47and there are those little pieces of white that we worked on the eye but I honestly believe that the quality of this picture is better on this machine

32:55that it was on my China blue machine I’m not using a 2-inch meniscus lens on

33:03this machine this is a two inch Plano convex lens and I’m still getting these

33:08fantastic results so this is the second part of the project we’re going to make a little stand so I’ve got some rather nice frosted perspex which I think

33:17probably might look quite nice the problem is it’s a cast acrylic it’s only

33:23a small piece probably only something like about a foot square but when I

33:29measure the four corners it varies in thickness anything from five point three down to four point seven so it’s going to be

33:39quite difficult to make a decision as to exactly what size we’re going to make these little pigs here well it’s not the pigs

33:46it’s the holes that the pigs go into we’ll have to just go and give it a try

33:51and see what sort of fit we get I mean I intend to glue these in but on the other hand if they’re a nice snug fit maybe I’ll just push fit them in okay

34:03now this is five millimetre Perspex so let’s just work out what we need speed I think we’re probably only going to be cutting this at around about probably

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

34:12eight ten millimetres a second so let’s play absolutely safe and go down to

34:18about six millimeters a second cut blowing yes I’ll have blowing thank you

34:24power we’ll sit it on to maximum 70% and that’s all we need is that put yes

34:31blowing yes cut 70 70 good okay now all we’ve got to do is order it now before

34:40we order this we need to make sure we just group these holes shift key down so

34:48we make all those red holes there as a group and now we can just come up here

34:54and we can select the holes to start with then we can do that one then that

35:04one and then finally the outside of the horseshoe and that’s ordered it in that

35:11out cut feet okay so we just saved that to a file and we go to the machine and cutter

35:20those faces drop the table

35:40set focus onto the surface about seven millimetres

35:51pretty well there

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

36:26well there we go fun too

36:31okay so let’s just have a quick look to see

36:37nothing I picked it now that one just it’s just snug

36:46that one’s a bit tight in there just swap them over because they’re different sizes that one is a perfect fit in there

36:58and that one’s a perfect fit in there and just don’t come out there perfect so a lot even a people in the room

37:08sits in there

37:14like that and there’s our little project finished where we spent time modifying this drawing to enhance some of its features or let me finish the project

37:24for this session we will just go through one more little exercise which is to satisfy my curiosity about what happens when we leave this drawing as unmodified

37:35as possible and we just pass it through our D works and put it through the Machine and see what sort of results we get so our D Works has imported the

37:44color picture and as its imported its turned it into a grayscale image so I’ve done nothing to the picture except crop it and we’ll leave all the tonal quality

37:52in that picture as it is so if we’ve brought this picture in and its native at 300 pixels per inch you’re going to set the output resolution and we’re

38:00going to change that resolution to a thousand then we’re going to do the picture with dot graphic so it will apply to image so we’re just zoom in and

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

38:09you can clearly see that it has turned it into a dot picture just black and white ignore the Gray’s because the Grays are

38:16a false image in this version of our D works and then finally what we’ve got to

38:23do is to invert the picture remember apply to view and apply to source okay so that was a much simpler procedure

38:40than messing around with Photoshop now I need to make this picture what size is

38:47it a hundred and thirty-four I need to make it about a hundred and fourteen now

38:55in doing that we will change the resolution so we’ll have to go back and reset the resolution and sure enough it’s changed it up to eleven seventy

39:03nine set the output resolution again to a thousand apply to view

39:13and applied a source and we’ve now got it back to a thousand PPI and the right

39:23size that I want a hundred and fourteen

39:31so now I’m going to add another layer and I’m going to add a frame around here

39:40from corner to corner and we just put handles on that

39:56and then we’ll change it by 10% so we’ll put that up to a hundred and ten percent

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

40:05and scale it up like that okay now we’ll make sure that those two pictures are

40:12perfectly lined up by putting a marquee around the whole lot and then doing center alignment that way and Center alignment that way and then finally

40:24we’ll put the text in it’s only two millimeters let’s make that about six

40:29millimeters and we’ll make that hundred-percent width okay

40:45and we’ll move that up to the center top there and we can make sure that that is

40:53centered as well by collecting the whole lot and just doing a horizontal Center

41:04like that there we go you saw it jiggle we’ve got both the

41:10frame and the text on the same layer which we can’t have so we need to select

41:19the text onto a red layer

41:31because the red layer has got to be a scan layer speed 100 power 30 40 it

41:47really doesn’t make a lot of difference we do 40 because the background is white and remember we can be quite harsh with

42:01the background it’s got a lot of temperature resistance and it’s not going to change color interval 0.1 that’s probably quite good enough we’re

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

42:13not doing the picture we’re just doing a piece of text and the frame that needs

42:19to be a cut layer because we just want a single thin line speed the gain will

42:28make that about a hundred and power we’ll make that again 30% maybe 40% the

42:4140% we don’t want later through power with a

42:48bitmap itself we were going to have that running at 250 millimeters a second scan

42:55mode 3030 I did it 40 40 before we’ll stay with

43:00the same value as 40 40 so that we can compare the actual output and a thousand

43:08pixels per inch the scan interval is point zero two five four it only

43:16registers three decimal places right we don’t want the output direct on okay

43:24we’ll just save that and back to the machine well it’s coming out it’s quite

43:31a nice picture but it’s not dark enough if we look at this very thin stripe just

43:38along the bottom here you’ll see that there’s that was where I started it off

43:44I’ve now run instead of 250 I’m running this at 400 millimeters a second

43:52and that darkened the picture off so to make it a little bit darker still

43:58basically what we’ve got to do is reduce the power now so that we don’t burn as

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

44:05much of the black off just remember this is the wrong way around

44:11you want more black normally they’ve increased the power or decrease the speed but we’re going the opposite way around so we’ve got to increase the

44:19speed and we were already at 400 so the only option left to us is to decrease the power

44:28decreasing the power hopefully we’ll need more of the black

44:46to 420 that’s a big change of power half the

44:53power that may be too much because we’re hardly making any mark down there at all

45:06I think there’s going to be far too black

45:12we’ll have to go for a compromise 30 yes that looks quite a lot better

45:22well here’s a print of the grayscale image that we started off with now this one here was done on my China blue machine with a modified picture this one

45:34was done on here the light blade machine

45:40with the modified picture difference in color well probably because this one was done at 50% on this

45:50machine and that one was done at 40% on the China blue machine so it’s a little

45:55bit darker and this one here this is just the unmodified picture so as you

46:01can see it looks completely different but then again this was an experimental test run we started off right down at the bottom here with 240 millimetres a

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

46:14second and then we change to 400 millimeters a second and you can see it got darker and then we did another run with 400 millimeters a second

46:27then we drop the power to 30% so that’s an unmodified picture

46:34that’s just a straight photograph which has been processed through our D works now I think you can see that it looks a little bit fuzzier you certainly can’t

46:45see these marks on the neck here which you can hear because we’ve sort of enhanced this photograph those marks are not really very clear on this one either

46:56and the horse looks a little bit on the dark side

47:05so I still think that this picture here off of the light blade machine which has

47:11been enhanced is probably the best image now you know how to engrave on anodized

47:17aluminium now some of you will have taken the basic lesson away from this

47:24session which is how to engrave and the fact that it is possible to engrave others of you might have been listing a little bit more carefully and understood

47:33why you can engrave on anodized aluminium and basically that’s what I’ve

47:41been trying to do over the past two or three sessions trying to explain to you the slight more technical details about how and why this machine can do some of

47:51the marvelous things that it can do just before I close and I go and get myself a top-up I want to leave you with a little image of me being silly trying to

48:02pretend it to be a laser machine first of all look there’s some instant energy

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

48:09happening my hand is a laser beam it contains when I’m moving it it contains something called kinetic energy don’t get in the

48:20way otherwise it will hurt don’t get in the way of the laser beam or it will hurt but the question is why does it hurt because here the laser beam is

48:31doing nothing it’s completely benign it’s only when it collides with

48:37something that it actually starts changing from being this invisible kinetic energy which is in my hand to something more tangible damage to the

48:49material now we talked about damage thresholds we talked about damage to the material I’m going to give you a classic demonstration of how my laser beam can

48:58damage material now here I’ve got a piece of perspex it’s an old scrap piece of perspex and here I’ve put a metal plate on the corner of the machine here

49:08and I’m going to reenact a scene from The Karate Kid

49:14well actually not true I’m more of a karate fossil and the reason why they scream yeah before they hit something is so that you don’t think they’re a wimp

49:23when they scream afterwards well I’m afraid I’m not a proper karate expert so

49:29oh yeah and that did hurt but two things have happened first of all I didn’t

49:38exceed the damage threshold for this material because I’ve done no damage to that the only thing I did was hurt myself but as I collided with that piece

49:47of material not only did I feel the pain but there was a small amount of heat energy that went into that surface there as I disrupted the surface of the

49:56material and wobbled some of the atoms and make them vibrate a little bit

50:01faster yeah okay so I can’t do a lot of damage with my laser beam you know it doesn’t exactly travel at the speed of light

Transcript for Photo Laser Engraving Anodized Aluminium Pt2 (Cont…)

50:12hang on I can amplify it the same amount of energy coming from my hand

50:22working through I know it looks like a hammer but really this is a lens and

50:27look exactly the same amount of energy

50:34well it’ll certainly damage the material and the only thing that’s happened is

50:39I’ve concentrated the energy and so the same amount of energy has been focused

50:45to do damage to a material that will no longer withstand the energy density that

50:51I’ve put into it and that’s what the whole principle of this machine is about

50:57light energy being converted into something that can do damage to this

51:03material now it cannot produce mechanical damage like I’m doing here it

51:11produces it converts into heat and produces heat damage so that’s all we can do with this machine produce damage by creating heat

51:21and that’s what these last two sessions have been be all about as we’ve seen heat damage to wood or an organic material and we’ve also seen

51:31heat damage to anodized aluminium and on previous occasions we’ve looked at the

51:37damage caused when the heat has been absorbed by a chemical on the surface

51:42and have produced a chemical reaction with the surface underneath so all of these different material damage mechanisms are to do with heat and in

51:53this next session we should be looking at the damage that we can cause by heating mineral materials well I’m off to get a top-up and also to get the

52:04damage to my hand repaired so I’ll see you in the next session