37 – Let’s Test our DIY Laser Engraver Rotary Attachment (29:23)

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 goes about testing his DIY laser Engraver Rotary Attachment.

Testing our diy laser engraver rotary attachment
Testing our DIY Laser Engraver Rotary Attachment

Contents

  • Looking at engraving a wooden rolling pin.
  • Looking at the drawing in RDWorks.
  • Leaving a small gap to account for errors in the circumferential measurement.
  • Checking the parameters and using ramp effect.
  • Gantry extensions and bar to prevent the head hitting the fixture.
  • Use of rubber bands to secure the fixture to the bar.
  • Maximum size of a rotary engraved graphic.
  • Placing the part in the fixture.
  • Centring the head in relation to the work.
  • Engraving the wood.
  • Engraving a wine bottle.
  • The process of engraving on glass.
  • Use of soapy water, wet kitchen towels, masking tape and Molybdenum Disulphide (MoS2) as potential aids to engraving on glass.
  • Looking at a graphic to engrave onto the glass.
  • Inverting the graphic.
  • Taking a bottle prepared with MoS2 and setting up the fixture.
  • Engraving the image.
  • Reviewing the results.
  • Changing the resolution, increasing the power and trying again.
  • Reviewing the results.
  • Summary.
  • (See Video 36 for notes on links to Cesar Medina’s videos)

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 Testing our DIY Laser Engraver Rotary Attachment

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0:14In the previous session we designed and manufactured a little rotary fixture for

0:21use on this machine and today we’re going to put it to the test. No this is

0:27not a weapon this is in fact a rolling pin and what I’m going to do I’m going to

0:32engrave on here a pattern for biscuit making first of all we’re going to take

0:37a look at the file itself in RDWorks and then we’ll come back to the machine

0:41and we’ll show you how we’re gonna set the Machine up. Well here’s the file that

0:45I’ve drawn it’s a pretty simple pattern and the rectangle that I’ve got here

0:52well first of all the width is the width of the roller and the height of this

0:59pattern here this rectangle is the dimension of the circumference around

1:05the outside of the rolling pin I’ve converted it into a flat surface and

1:09then I fitted an appropriate number of hole patterns into that rectangle now

1:14the key thing to look at here is the gap at the top and the gap at the bottom two

1:19very small gaps which will allow me to have a small amount of mismatch in the

1:25pattern without it showing. In other words if this gap that I finish up with

1:30is a little bit bigger or a little bit smaller it’s not an issue the last thing

1:34I really want is for the patterns to overlap so I can simplify life a lot

1:38by making that as the whole pattern now I have put the little green square which

1:45is the head position right at the top center there because that guarantees

1:50that I can align the nozzle with the center point on the rolling pin a quick

1:58look at the parameters I think speed wise we’re going to have

Transcript for Testing our DIY Laser Engraver Rotary Attachment (Cont…)

2:02that up at around about 200 millimetres a second, is blowing well this is an

2:08engraving process and I don’t have a blowing for engraving I turn it off so

2:14it’ll be no, it’s a scan, power well I don’t think we’re going to be we’re

2:23going quite fast we’re in a beechwood I want it to burn

2:28maybe a millimeter millimeter and a half deep here’s where we’re guessing

2:33I shall go for 40% now I think we’ll try and put some ramp effect in here put a

2:39slope on the side of the cut okay let’s go and see if we can make this happen

2:43here we’ve got everything that I need to do the job one of the most important

2:49things you’re going to need apart from the fixture is a flat surface to roll it

2:53on now I don’t mind what flat surface you use it could be a piece of acrylic a

2:58piece of glass a piece of steel a piece of MDF a piece of plywood anything

3:02that’s flat that will allow this to roll backwards and forwards so certainly a

3:08honeycomb bed or a slatted bed you’ll need to cover now you saw me manufacture

3:12these parts but I never did mention them the last time because they’re not

3:16actually part of this fixture now I mentioned how this worked before by

3:21pressing against the gantry now the only problem with that is in this instance

3:26the head is going to run to one side and to the other and smack into these

3:32depending on what length of job I do so I don’t want to run that risk so what

3:37I’ve done I’ve adopted a slightly different strategy basically what I’ve

3:41done I’ve extended the gantry forward how on earth can you do that but

3:45basically this piece here is a sliding shoe that sits on the Y rail and pushes

3:49up against the bearing block we have one for this side as well so let’s put the

3:58head towards the back and put that block on

Transcript for Testing our DIY Laser Engraver Rotary Attachment (Cont…)

4:03and now what I have here is a piece of square steel bar it’s quite heavy it’s

4:13about half inch square now before I drop that into place I’m just going to do

4:20something a little bit silly and I’m going to put four small elastic bands on

4:26it now you’ll see why when they come into play in a minute.

4:30so we drop the bar into there and basically what that bar is done it’s

4:37acted a bit like a cowcatcher on the front of a car or a bumper that

4:43is now sitting across the front here and make sure that when the head comes

4:49forward like this and of course it’s being pushed forward by the bearing

4:54blocks so it stays completely parallel and doing exactly the same thing as the

5:00gantry but it’s some four inches further forward it will then catch the rotary

5:07device and push the rotary device forward as you can see there if we go

5:12too fast and we nudge the rotary device

5:20it responds and bounces away from the bar I know we haven’t got any weight on

5:26here at the moment but this is very very light but that’s a risk that we can’t

5:30afford to take I have made sure that this bar and our fixture stay together

5:36and we’re doing that by hooking this

5:44over there like that

5:53now that means that when I send it forward

6:02it stays completely tied up to the bar okay it’s a bit crude a rubber band but

Transcript for Testing our DIY Laser Engraver Rotary Attachment (Cont…)

6:12it’s functional along with the rest of this fixture which is crude but

6:17functional and actually elegant in its simplicity. As far as it will go is when

6:25it hits the back frame of the machine now although this is a 400 millimeter

6:31depth machine the only depth that we’ve got to work with for rotary engraving is

6:37this depth here because the time this gets to the front here and hits that’s

6:42when we run out of stroke so we can’t engrave a picture or a logo any bigger

6:48than say 250 millimeters tall now I know the graphic for this is well and truly

6:54less than that so the first thing we’re going to do is to take it apart we’ve

6:59got to set this up on the lowest possible position because that means

7:05that then that pair and that pair are parallel to each other and I think from

7:11where it is at the moment it’s probably not far off

7:20the right depth, there we go, so the roller end stops are now set but what we do

7:26we push that against the back so that it’s just lightly against the back and then

7:30we’ll bring the head forward until it just touches and takes it away from the

7:36back so now we can guarantee that we’re nice and parallel we’ve got the bearing

7:42blocks all connected up to this bar and everything is running nice and true so

7:48what we’ve now got to do is to set the head so that the head is in the centre

7:52of the job that’s the most convenient way to set it up in the centre and say

7:57that’s 2 1 5 or 2 1 6 we’ve set that up to 108 so that’s where I’m going to set

Transcript for Testing our DIY Laser Engraver Rotary Attachment (Cont…)

8:06my datum my origin and I’ve already designed this so that the centre line of

8:15head always comes to the center line to the component so I don’t have to worry

8:19about looking at it this way because that’s part of the design when I

8:23manufacture the thickness of the arms and all of this I took this into account

8:26so we’ll put some extraction on and I will close it, because I certainly don’t

8:32want to put smoke anywhere onto the job I’d like to try and keep it nice and clean

8:55so we just watch what happens at the end of the stroke

9:01nothing began to get pulled away and leaves the

9:06job where it is well for a budget cost I think that jig was probably a success

9:14so I should just go away and wash that in soapy water just to get rid of the

9:20Burn smell but of course it won’t get rid of the cut. Okay well having met the

9:24challenge of rotary engraving on wood

9:28that was parallel that was quite an easy shape to deal with, maybe we should up

9:35the ante a bit and change the shape to something a bit more challenging and

9:43also the material which is glass this is one of my wife’s favorite wines she says

9:49it reminds her of me mainly because it’s a bit dry and fruity and nothing to do

9:56with the name on the label now before we start engraving on glass there are a

10:02couple of things that you really need to understand first of all glass does not

Transcript for Testing our DIY Laser Engraver Rotary Attachment (Cont…)

10:08cut and it does not burn but we can etch it and that’s because of some

10:14interesting mechanical phenomena that happens when you fire infrared energy at

10:21a glass surface now in one of the previous sessions when we were talking

10:25about engraving on stainless steel we talked about the laser beam either

10:32being absorbed by or being reflected by the surface that it hits so here we are

10:39with a nice parallel laser beam that passes through a lens and then focuses

10:50down to a very small area where the energy density gets huge. When we fire it

10:59at a piece of glass I’m going to look at that little spot there in a magnified

11:05way

11:08so here we are with the beam coming down to hit the surface now remember it’s a

11:15beam of light at this point in time it’s not heat and it’s not until it hits this

11:19surface and gets absorbed into here that it starts turning into heat now glass is

11:27a very very poor conductor of heat and so consequently what happens is this

11:33little teeny-weeny area here starts heating up at a tremendous rate of knots

11:39and it expands because it’s getting hotter and everything that gets hot

11:45expands but the background is still cool cool cool

11:51all the way around and what that causes is at this point here where my arrow is

11:59it causes a lot of stress to occur expanded glass / non-expanded glass and

Transcript for Testing our DIY Laser Engraver Rotary Attachment (Cont…)

12:07what actually happens is the there is a fracture that occurs between the hot and

12:12the cold zone and you get a little teeny-weeny shard of glass popping out

12:16the closest I can get to imagine that it’s like a stone chip on your

12:20windscreen this is a mechanism basically of little stone chips and of course when

12:29you get a stone chip you could see it because the light gets reflected and

12:34refracted off different surfaces within the chip and so what looks like clear

12:39glass all of a sudden becomes frosted glass when you start putting hundreds

12:45and thousands of little teeny-weeny chips beside each other now

12:49these chips are not exactly scientifically measurable or

12:53controllable every one could be slightly different it just depends how the glass

12:58shards if you’ve looked into glass engraving you will see that there are

13:04lots of hmmm Call them tricks for trying to engrave glass nicely I use the word

13:14nicely in inverted commas because how do you make something chip nicely

13:21now one of the oldest and simplest tricks for engraving glass is to coat

13:26the surface of it with soapy water now what does the soapy water do well first

13:36of all the soap in the water ensures that you get a nice even film across the

13:42surface of the glass but it’s really the water that you want hanging on the

13:47surface of the glass now a film of water will do a very good job of absorbing the

13:53the infrared light that’s fired at it and so therefore our beam hits the

13:59surface of the water and it is the surface of the water that is boiling and

Transcript for Testing our DIY Laser Engraver Rotary Attachment (Cont…)

14:04creating heat, that heat then gets transferred quickly but in a slightly

14:10less dramatic fashion to the glass that’s underneath but of course it’s

14:17almost instantly vaporizing the water and so yeah there isn’t a great deal of

14:24difference between firing the beam at the water and firing the beam at the

14:29surface of the glass so soapy water is not necessarily a very effective way to

14:35make the engraving action gentler so the next trick that’s used is to hold the water

14:42onto the surface in a different way and that’s with wet kitchen towel so now

14:48you’ve got two substances that are absorbing the energy the first one is

14:53the water which will immediately vaporize and then of course you’ve got

14:57the kitchen towel which will effectively start to burn and what’s happening is

15:03again you’re reducing the heat intensity to the surface of the glass underneath

15:09you’re absorbing the energy before it hits the surface of the glass but there

15:14is some transmitted heat that then passes to the surface of the glass that

15:19hopefully will cause a similar sort of rapid expansion and sharding but it may

15:26well take place over a larger area and so consequently it may

15:32have a slightly softer feel to the sharding that takes place now there is

15:38another technique that you can use and that’s this stuff masking tape now again

15:47let’s just examine what’s going on with masking tape same principle really

15:52you’ve got the masking tape sitting on the surface with a glue of some sort

15:56underneath it and the light arrives at the surface turns into heat energy as it

Transcript for Testing our DIY Laser Engraver Rotary Attachment (Cont…)

16:03starts to burn the masking tape and then that local heating effect has the

16:09sharding effect on the glass underneath it’s locally heating the glass

16:12underneath in every one of these instances the mechanical mechanism for

16:17engraving the glass is the same but what you’re doing is basically attenuating or

16:22moderating the heat to various degrees now a technique that I personally use is

16:28something I discovered after I’d experimented with molybdenum disulphide

16:34on the surface of stainless steel understanding how the molybdenum

16:40disulphide acts the same as all these moderating layers here but it’s much

16:46more efficient at converting the heat and then producing a much wider it

16:55absorbs the heat and starts to spread it out more because it is a metallic based

17:01substance and so consequently you get a much bigger wider pool of heat and so

17:10you get a much gentler sharding action with molybdenum disulphide than you do

17:15with any of these other techniques the problem with the masking tape is if you

17:19want to do a dot picture you’re going to finish up with lots and lots of little

17:24bits of masking tape on the surface that you can’t easily pull off if you just

17:29want to mask up for a logo then masking tape probably does a reasonable job I

17:34would steer clear of these two techniques personally that one has got

17:38some merit to it but this one is what we’re going to demonstrate

17:42today you paid your money and takes your pick right try to find something

17:49challenging to put on the bottle is interesting now this again brings up

17:54another interesting lesson this is a black horse on a white background

Transcript for Testing our DIY Laser Engraver Rotary Attachment (Cont…)

18:02basically as you all know when you frost glass it turns white or grey so we

18:10shall need to reverse this image eventually from white and black to black

18:17and white to get the desired effect on glass also the size of this picture is

18:24too big really to go on the bottle about 190 millimeters tall half that size

18:30would be more appropriate let’s check with a bitmap handle before we do

18:34anything and we find that the resolution is a hundred and sixty pixels per inch

18:38so what we’re going to do is we’re going to set the padlock closed and we’re

18:43going to reduce this number to fifty percent we’re going to reduce the

18:46picture to half its size okay now let’s go back and check what the bitmap handle

18:51now says it was a hundred and sixty now it’s gone up to a resolution of 320

18:57which is far too high for what we’re trying to achieve especially as I’ve got

19:04a two inch lens in this machine so we’re going to set the resolution down with

19:10this tick box here set the output resolution to 160 and then we’re also

19:16going to invert the color and apply to view and apply to source that’s what

19:24we’re going to get again you’ll notice that we have got this at the top now

19:29depending on which way we’re going to set the bottle up will depend on which

19:33way we set this picture round. So let’s go and have a look at how we’re going to

19:37set the bottle well you don’t think I’m going to use a full bottle of wine do

19:41know so here we’ve got our bottle prepared with Moly sulphide on the

19:47surface and looking at this we’re going to have to use

19:54this end for the parallel end and this end to try and keep it parallel we shall

20:03have to raise this up to several levels higher and also probably reset

Transcript for Testing our DIY Laser Engraver Rotary Attachment (Cont…)

20:10this so that the wheels are further apart maybe even five

20:15let’s just see what five looks like, five may cause the bottle to touch the bottom

20:22but let’s just give it a try. But bear in mind we’re trying to get a contact

20:26angle and probably somewhere around about ninety degrees that looks good

20:31I think this probably needs to go together one more so we set this in by one then we’ll

20:38find out the height that we have to be

20:43to get it running parallel now I’ve got a nice wooden spirit level here which

20:49won’t damage the surface of my material and that looks pretty good

20:56we’ll set the height in a minute but the whole purpose that this was if you

21:00remember to work out which way our drawing is going to have to go so we

21:06want ears to the right because this picture here will come out exactly the

21:13same as if we were engraving it on the table

21:16there’s no reversals no amplification of any sort in any direction in an

21:22anti-clockwise direction which is minus 90 like that

21:29okay now we’ve still got our start point in the center at the top so that’s good

21:36so that enables us to decide approximately where we want the picture

21:40on the bottle so we need to set the focus up to about seven and a half

21:48we’ll push the head further back and we’ll push the frame as far back as it

21:56will go and pull it forward just a shade and then we’ll bring the table forward

22:02and we’ll pull it forward just a shade more watch the bearings here because

Transcript for Testing our DIY Laser Engraver Rotary Attachment (Cont…)

22:08this is where it’s going to contact don’t look for anything here

22:14and there we go we’re just about to make contact now, there we go. And we’ve pushed it

22:18forward we can now make sure that it’s pushed back against the bearing blocks now

22:23you shall need to set it roughly towards the middle here let’s try that it’s not

22:32that important in this particular instance so we set the origin there air

22:37assist yeah I think we do need some air assist this time but maybe not complete

22:43full air assist so let’s think about our cutting parameters well they’re not

22:48cutting their engraving so it’s a bitmap and it’s scan so yes we’ve got scan on

22:55speed hundred, bearing in mind we are doing a dot image and I think therefore

23:02maybe it would be a good idea to keep that back closer to about a hundred and thirty

23:08maybe and the power well the power we need to keep that quite low because we

23:17don’t want to if you like crack through the glass so my guess is that we’re

23:23going to set this to probably something like about 15%, 15% maybe even lower than

23:30that so let’s try 12% if I get it wrong well I can soon empty another bottle!

23:36Pitch now that’s an interesting point because we’re doing a dot graphic we

23:41really ought to make the pitch match the graphic so 25.4 divided by 160

23:49pixels per inch equals point one five eight seven, point one five eight seven

23:59okay and I think we’re ready to go now as I

Transcript for Testing our DIY Laser Engraver Rotary Attachment (Cont…)

24:03mentioned to you before I don’t like the smell of molybdenum disulphide

24:09it’s a bit suspicious so I’m going to close the lid and let the Purex

24:13extraction unit make things safer I’ve not done this before so this is a

24:21brand-new experiment for me

24:47I think the first thing you can see, is we’ve got an image on there of some sort

24:52question is what sort of image let me just clean up half the bottle because if

24:59I need to we can try and image on the other side because it’s only gone a

25:04little way around

25:09well I have to say, on balance that’s not too bad

25:16a little bit pixelated but generally not too bad I wonder whether I could

25:21increase the resolution slightly

25:27and maybe increase the size of the picture

25:31but I’ve got room on the other side of the bottle so I think that’s what we’ll do

25:36for test number two okay well we’ve done several things this time

25:41we’ve changed the resolution to 240 dots per inch and the interval

25:47accordingly we just make sure that we press these

25:51up against the end stops there, we’re in roughly the same central

25:56position so we should be okay and I’ve increased the picture or rather instead

26:02of decreasing the picture to 50 percent, I’ve decreased the picture to 75 percent so

Transcript for Testing our DIY Laser Engraver Rotary Attachment (Cont…)

26:08we should get a bigger picture higher resolution and I’ve increased the power from 12%

26:14to 13% so we’ve got a fraction more power okay let’s see what we’ve got this

26:21time well I would say that’s looking pretty good before we take the Molly off

26:27I have to say I think that is pretty impressive

26:31now with the molybdenum disulphide this finish comes out silky smooth just as if

26:38you were to fine sandblast it or bead blast it and of course as I said the

26:44glass turns white because it’s basically what I call a binary material and the

26:49only way that you can see the black of the black horse that’s on there is by

26:54having a black background now sadly this is not wine that I’ve put in here this

27:03is black coffee that result there was a starting point a bit patchy not very

27:08good but it does show that larger size finer resolution even with a two inch

27:16lens in this machine I’m able to get some pretty good results with the

27:21pictures if you choose the right picture and get the sort of contrast factor

27:25right. All in all I’m extremely pleased with that

27:29um but of course we mustn’t forget the real star of the show which was this

27:37little piece of kit here so yeah it’s served its purpose and it also enabled

27:44me to test my dotting Theory on some glass which I’ve never done before and

27:51it’s a step in the right direction for what we should probably be exploring in

27:56a future session trying to improve the resolution of the pictures because my

28:01dotting stuff was all about working with organic materials now I know that there

Transcript for Testing our DIY Laser Engraver Rotary Attachment (Cont…)

28:06are great gains to be had when we move away from organic materials into

28:09minerals such as glass slate even things like anodized aluminium hold great

28:17promise so I think that’s all for a future session but for

28:22the time being I’m getting ready with another bottle to test so yeah I shall

28:28see you in the next session I think because yeah I am feeling fruity now

28:32bye

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