0:14Well welcome to another Lightblade Learning Lab. What we’re going to talk
0:19about today is mineral materials and I’m afraid we won’t be able to cut those, we
0:25shall only be able to mark them. But we need to understand a little bit about
0:30the material itself before we dive in and try and do something with it.
0:36First of all, we have to understand we can’t cut it, but I think that if I gave
0:41you a piece of granite and this machine, you would never attempt to cut the
0:44granite. You might not even think you’ll be able to mark with it, but we can. Now
0:52as I’ve told you many times before, I’m an engineer, so I will not pretend to be
0:58a geologist. Although I have to admit to having a passing interest in many
1:03aspects of geology. So what we’re going to talk about today is something called
1:06foliated metamorphic rock, come on in and I’ll show you what we’re actually
1:16talking about. Okay, so now I think you’ll recognise what I’m talking about,
1:21something we all recognise as slate. It has got some strange properties, in that it,
1:30as you can see here, it tends to flake and it’s used for roofing tiles for that
1:34very reason, it’s got flaky properties. That flaky property comes from a
1:39material that’s probably built into most of these called mica, which has got this,
1:45it’s got little shiny bits in it. So if we look closely at the surface of these
1:50various types of slate you’ll find little teeny-weeny shiny crystals in it,
1:55and that’s the mica. But in addition to that it’s also made up of silicates,
2:01which are like sandstones very fine sand materials. It’s basically a
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2:08sedimentary rock that was laid down millions of years ago in the bottom of
2:11an ocean, layer upon layer, and then it’s been compressed by huge pressures as
2:17it’s been subducted under further rock formations, and it’s pressed it into this
2:24rock. So it started off as silt and now it’s become metamorphosed, which is what
2:30this metamorphic bit is, it’s been changed into a rocky material, a stone. So
2:36the main producers of slate in the world are; this is from Spain, this is from
2:42China. It comes from North America and it comes
2:46from Brazil, we would know in the UK, a big slate producer as being Wales. Well
2:53it’s big in the UK but it’s not necessarily big in world production, but
2:58these two items here are both Welsh slate. But let me just do a couple of simple
3:04tests on this slate and we will see if they are all the same. Now I’ve got full
3:13power operating through the lens there and I’m going to hold a pulse on for
3:19probably two seconds. Nought, one, two. The Chinese slate, nought, one, two. You
3:28notice the difference in the colour of the burn and also the fact this was
3:31rather sparkly. Now here’s a piece of green Welsh slate
3:37Nought, one, two – and here’s a piece of Welsh plum slate, nought, one, two. Let’s just go and take a
3:47look at these under a microscope and see what we’ve done to this material.
3:51Well first of all, the Spanish slate. You can see the way that the edge has
3:57started to flake away, now you can also see this glassy volcano effect around
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4:03the outside here. Let’s just try and chip that off. So this is a particularly
4:15unstable material to work with, it’s all flaky. Where did the glassy material come
4:21from? This was fairly high in silicates this material, when you heat silicates up
4:26to a thousand degrees C they become a liquid, a bit like syrup, and then when
4:32you let them cool well you get glass and that’s what we basically created on the
4:37surface there. A little, a little volcano of glass around the edge and if we look
4:41carefully here you’ll see that not only did we produce a volcano of glass,
4:45there’s a little bead of glass that’s come out of the volcano. That’s a
4:49starting point for Spanish slate, doesn’t look like a very stable material does it?
4:53Let’s take a look at our Welsh plum slate, you can probably see it I think,
4:57that this edge round here is flaked up. Just here, and here we’ve got our glassy
5:04material again. What have I just done? In fact it wasn’t a glassy material, it was
5:10a glass bubble which I’ve just burst. Look there’s the little teeny-weeny
5:14flakes of it. You should look as we dig it into there,
5:19that’s glass all the way. Let’s look at the Green Welsh slate.
5:29Again, we’ve got our glassy structure on the surface here, look I’ve got a little glass
5:33balls ejected from the volcano and let’s see what we can do with this. Can we peel
5:38this glassy subjects substance off the surface? It’s slightly more crumbly glass
5:43than the other and finally we look at the Chinese slate. There are lots of
5:47little white spots, now those little white spots are reflecting the light and
5:53they, we don’t appear to have any glass formation here. So there’s a very high
5:59mica content in this material. Now mica melts at about 1600 degrees C, whereas
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6:09glass forms at about a thousand degrees C. But under normal daylight viewing with
6:15an eye glass, I can in fact see that this hole is glazed all the way around and in
6:22fact there is a small ring of clear glass around the edge.
6:26It’s hardly perceptible but there is a very small amount of glass there. Well
6:32here we are at the first hurdle, we’ve already found out that not all slates
6:37are the same. I think the only thing that we can do, is to go back to my good old
6:45standard test and see what size dots we can produce on this material. Now while
6:51we’re here and because I can. I have a small sample of granite here, let’s see
6:59what granite does. Nought, one, two. That’s producing the same
7:06glassy volcano as the three slate samples that I’ve tested So we’re going to
7:10carry out our small test pattern which has dots point one of a millimeter apart
7:16and we’re starting off at quite a high speed 200 millimeters a second and 30%
7:23power. But bear in mind that this machine has been set up for special mode so it’s
7:29still got pulsing power on it. We’ve got a nice row of dots along the centre,
7:38we’ve got a joined row of dots across the bottom and these dots are whiter
7:45than the background. So it’s pale grey as opposed to a light grey, so there is a
7:52bit of a contrast there that we can work with. So we might be able to do some
7:58pictures with this, whether they’re just going to be engraved logo type pictures
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8:02or whether we can actually get some photographic texture into it is
8:08going to be rather interesting. Well let’s see how the Chinese slate performs
8:12shall we?
8:17We can’t really see the individual pixels, so I think we’ll slow it down –
8:26let’s try 150, that’s a really nice line of pixels that just touch each other, so
8:38that’s point two diameter pixels, but they’ve got a little crisp holes in the
8:42middle of nearly every one of them. So maybe I should back the power off a
8:46little bit, see if we can get them even crisper.
8:54Well the dots are a little bit crisper but they’re also very faint, so I think
9:00we’ve gone the wrong way and I think we’re gonna have to stick with
9:04something like 30% and a hundred.
9:13Well I would say that’s a pretty good compromise, it’s a 125 millimeters a second and
9:2425% power with special mode and a 2 inch lens. So what we’re now going to do is to
9:32dig out my formula and calculate what the best resolution for the picture
9:38should be. Well I’m using my well-tried formula for photo engraving and we’re
9:43gonna try and adapt it to fit this particular material because this was
9:47designed for wood and card but we’ve got different parameters here on slate. I’m
9:54fairly confident this formula will work with a small amount of tinkering here
9:57and there. So from the little experiments we’ve just done, we found it the best dot
10:02that we can get is 0.2 and that means that we can keep, that means
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10:08we have to keep the resolution of the picture at about a hundred and
10:11twenty-seven. Well, I’ve pushed the boundaries a little
10:14bit and I’ve pushed it up to a hundred and fifty, I’ve reworked the picture and
10:18I’ve done it at a hundred and fifty PPI. All this work was done originally with
10:23common mode, but because we’re using special mode where we’re able to use if
10:28you like half the power twice the speed and we still seem to be able to get a
10:34dot, because that’s how I’ve managed to find my dots. We’ve done that in probably
10:40something like 1.5 milliseconds, so what I’ve done I’ve nominally chosen 1
10:47and 1/2 milliseconds as my parameter here, instead of 3 milliseconds. That
10:53brings me down to 7.5 milliseconds per millimetre and when I divide that
11:007.5 into 1 second it means I actually can run at 134 millimeters a second. I’ve
11:07pushed the resolution up a shade, so what I’ll do I’ll pull the speed down a shade
11:12and run it at the test speed that we established we got the best dots which
11:16is 125 millimeters a second. So hopefully those 2 things will start to cancel each
11:22other out
11:27and the power that we found we can use is 25% / 25% in SP mode and that’s how we
11:36established our test pattern. The paperwork where you’re producing lots of
11:40smoke, we need to turn the air assist down so that it doesn’t blow back down
11:44onto a job. But in this particular instance, I think we need the air assist
11:48on and set to maximum. That’s how I’ve tweaked my formula this time round. Now
11:55we must remember that we had a black background here and we were producing
12:02white cuts and here on slate we’re doing exactly the same thing we’ve got a black
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12:10background and we’re going to produce white cuts off it.
12:20I can’t smell too much in the way of fumes.
12:31Well there’s our end product and obviously that looks pretty good on
12:37slate, but to be honest when you look at it from a distance and compare it to a
12:42proper black and white image yeah it’s it’s a little bit weak, because the
12:50fundamental problem is we can’t get white, all we can get is light grey and we
12:56can’t get black, because all we’ve got is the background. So we’ve got a two shades
13:02of grey picture here, now I don’t know whether we can enhance that a little
13:06bit. So here we’ve got some furniture polish which will produce a slightly….
13:20so yes coating it with something does improve the quality of it, as you can
13:26see. Just a little bit of furniture polish has changed this from a
13:29grey to a dark grey and that has enhanced the blacks without actually
13:34taking anything away from the background.
13:38So that’s pretty good going for something like a hundred and fifty dots
13:43per inch.
13:48So the next question is, can we repeat that on Spanish slate?
13:57As you can see this, this Spanish slate is a different kettle of fish, it’s not
14:02very, um what can I say, it’s not very flat. It’s not very uniform. So I think
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14:08we’re going to have all sorts of problems with this, but we’ll give it a
14:10try.
14:21Well from that angle there it doesn’t look too bad, catch in the right light
14:26it’s not too bad, but when you look at it in front like that it’s pretty weak and
14:32so look there’s the difference. Now at the moment that’s the difference between
14:37the two slates but I haven’t enhanced this one. This was just two shades of, it
14:42was a grey and a light grey. This one’s a dark grey and a sort of… a sort of a
14:48funny muddy brown. Well I think even though we’ve enhanced it I don’t think
14:55there’s any doubt that this is a much lighter background than this one, this is
14:58a much better slate to etch on than this. Because this is definitely blacker, the
15:07shades of grey on the slates are not that different, but it’s the composition
15:12of the slate itself which doesn’t give the contrast when you put these little
15:17teeny-weeny burn marks on. Now I say burn marks because I think that what we’re
15:21doing we’re actually hitting this so hard that we’re again evaporating little
15:25pits. We’re not producing the glassy effect, because we’re not giving it long
15:31enough to erupt and turn into Glass. I thought that this process on here would
15:36have been a stone chip process I.e. like on glass where we heat the surface of
15:42the glass up and we pop a little stone chip out. This looks to be much more of
15:47a burning process because when we look at this under the microscope you’ll see
15:53that there are definite uniform little spots not random shards. So we’ve already
16:02established that this material is going to work very similar to slate. Now I’m
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16:06not going to change the settings I’m going to leave them exactly the same as
16:09they are 125 millimetres a second 25% power and well you know this is the
16:17same basic material even though it finishes up as a much harder and tougher
16:21material the basic structure of this material is still made from the same
16:25chemicals and elements. We’ll take a gamble on my one and only
16:30piece of material and we’ll give it a try. Now the great thing about this is
16:35we’ve got a black product to start with so hopefully the gray lines on here will
16:41give us a much better contrast when it comes to a picture.
16:53Now note that I’m doing all this work without any extraction on, there are no
16:58noticeable fumes at all with this.
17:04When we look at that under the microscope, we’ll probably find that we
17:09could’ve possibly increased the resolution, but I think when you look at
17:18it from sort of just a short distance away it’s still pretty amazing. I might
17:26pop down to my local stonemasons and see if they’ve got any reject granite that
17:30they could either let me have so that I could do some more experiments.
17:34I just noticed, one of the things that Iwas talking about and I can see on
17:39here…. now those little shiny crystals
17:41that are all across that vein there that’s the mica that I was telling you
17:45about. I catch them right, maybe you can just see that they’re shining in the
17:49light. That’s the mica, we’ll just go and look at these under the microscope. I mean
17:57we’ve got enough slate here to try another two or three so let’s go and
18:00have a look to see what we could do to improve this, if we could do anything. We
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18:06can’t change the colour remember, the colour is whatever it is. The only thing
18:13that’s affecting this, let’s call it white here if we were looking for
18:17something that was white we can only possibly just crush the pixels up a
18:22little bit closer together because I do believe there are gaps in the
18:25Y-direction, we’ll go and look at that under the
18:28microscope. All right well, while that’s going on
18:34what I decided to do was to change the resolution from 150 up to 300 PPI this
18:44machine is not running at one hit per pulse it’s running at a very high speed all
18:51the time and it’s putting a large number of pulses down for every pixel. The
18:56question is how many pulses is it putting down for every pixel and the
19:01answer is when you do the quick calculation the whole background pulsing
19:05system is running at 20 kilohertz so that means that I’m going to get 11
19:11pulses per pixel at 300 dots per inch. The sensible thing to do would have been
19:17to have set the parameters for this particular picture to the same
19:21parameters that I had before and only change one of the parameters ie the dots
19:26per inch. That would have meant that I would have had twice as many dots in the
19:33y-axis and twice as many dots in the x-axis
19:40but hey I’ve decided to go a little bit overboard, ignore the rules slightly and
19:47I’m running at 40% power as opposed to 25% so I’ve got heavier pixels. So I’ve
19:54got more power going into each pixel, but I’m running faster so in fact I’ve got
20:00less power going in per pixel it’s a very strange balancing act that I’m
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20:06trying to perform here and I’m second-guessing that I don’t compromise
20:10the clarity of the picture by blurring the pixels into each other. Now that
20:16didn’t seem to happen when I tried the same thing with anodized aluminium and
20:22we got up to a thousand pixels per inch. So let’s see what the results are. I have
20:30to say they’re looking pretty good so far.
20:36So stand here watching this picture and you’re so hypnotised by watching the
20:41picture you are not actually watching what the actual laser beam is doing. Look at
20:47that light, I mean that light tells us that we’ve got a huge amount of power
20:53going down instantaneously on pixel after pixel after pixel. That light
21:01doesn’t come for free from nowhere, that’s a huge amount of heat that’s
21:05being knocked out into every pixel and it’s quite phenomenal that this system
21:10can work that quickly. Now somebody’s going to ask me where did I get my
21:15Chinese slate from? Well the answer is from a cheap pound store.
21:24They would not be cheap and they wouldn’t be in a pound store unless they
21:28bought them in bulk from China.There’s no dust and there’s no fumes so it’s not
21:38there, we must be vaporising this material. Okay so the holes are very very
21:45small, there is a certain amount of 3D’ness on that picture. Perhaps it’s just
21:55my fingertips feeling holes and no holes but it’s pretty amazing isn’t it. Now I’m
22:03gonna try something a little bit different this time to see if I can
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22:06enhance it, this is basically a wax-based floor polish. Now when I paint this onto
22:14wood it soaks in,
22:20and I can actually see that it’s changing color as it slightly soaks into
22:24this.
22:29Well I have to say that’s pretty impressive I never thought that I would
22:35get to 300 pixels per inch, 240 millimetres a second on a piece of slate
22:42and achieve a result like that. I thought it was going to be rather fuzzy and
22:46blurry and I think the secret really is all coming back to power management
22:52through this special mode. Breaking the pulses down into very small increments
22:58so we don’t do too much damage at a time but we do lots of damage over time with
23:04small increments. I think even from this distance you can see how much clearer
23:10and crisper black and white that one is as opposed to this one and it can only
23:16be the crispness of the blackness not the amount of whiteness because this is
23:22the same texture it’s the same colour as this, but it just looks crisper.
23:30I mean the whiskers on here are not bad at all, but my goodness they don’t half
23:35stand out much better on this one. Well I hope that’s an interesting session oh we
23:43could go on and we could do some black and white logos and some text but after
23:50pictures that’s kiddie stuff, this is the difficult stuff getting images down with
23:59the right sort of crispness and clarity. Understanding how we can do that, if you can
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24:05understand how we can do that and you can second-guess what’s going to happen
24:08then hey you’ve got it cracked. Now I’m extremely pleased at what we’ve done
24:17here, I didn’t know what the results were going to be. I think you’ll agree that
24:22we’ve come to a very very satisfactory conclusion. Now I would like to get some
24:27more granite so that I can play around with some more polished black granite. Who
24:32knows what we could do with black granite, whether we get that up to 600
24:36dots per inch? But I think we’ve come a long way with photo engraving on various
24:40materials, over time we’ve covered card and wood,organic materials, now we’ve
24:45done mineral materials, we’ve done a little bit with glass when we did rotary
24:49engraving which is another mineral ish material but of course that was a
24:53completely different process. I was expecting this to be something similar
24:57to glass a sharding process, but it turns out not to be. This is much more of an
25:03evaporation process I do believe, but I think we’ll have a complete change of
25:08subject in the next session so until then cheerio.
