42 – Setting the Laser Machine Autofocus Pen (24:38)

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 Laser 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 explains the process of setting the laser machine autofocus pen.

Laser machine autofocus pen
Laser Machine Autofocus Pen


  • All the lenses focus at approximately the same point.
  • RDWorks settings offset from ’Z Zero’
  • Need to change the switch position for each lens.
  • Replacing the Autofocus pen bracket for a new design.
  • Making the bracket (design in DXF format is here).
  • Drilling and tapping the holes.
  • Using a piece of O Ring to secure the pen which creates a friction adjustment system.
  • Fitting the assembly to the laser head.
  • You can go to Video 10 to find out how to focus a lens exactly.
  • Adjusting the assembly using the ‘Diagnosis’ feature which indicates when the switch is pressed or not.
  • Showing how to remove the lens and replace it.
  • Disadvantages of the autofocus pen system.
  • (When you start the machine or press reset it cancels auto-zero setting.)
  • Russ doesn’t move the focus into the job – he always sets it at the surface and adjust the speed (showing an example of why).
  • Russ doesn’t use the autofocus pen or the red dot pointer.

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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Making the bracket (design in DXF format is here)

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What can a laser cutter cut?

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Transcript for Laser Machine Autofocus Pen

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0:14Well welcome to another Lightblade Learning Lab. Today we’re going to tackle

0:20something completely different, we’re going to go back into the mechanics of

0:23the machine and we’re going to do a little bit of setting. The item that

0:29we’re going to look at is the autofocus sensor switch, otherwise known as a pen.

0:35Now I’m afraid you’re gonna have to put up with another one of my very high tech

0:39drawings. The lenses sit at different points above the work surface, which is

0:46here. The lenses in this particular machine always produce the focal point

0:51at approximately the same position. The idea is that the beam focuses down

0:58from any one of these lenses, this being a two inch, this being a two and a

1:04half inch and this being the four inch.

1:09They all focus down to this one point, which is approximately seven millimetres

1:17below the nozzle itself. I say approximately, because you cannot

1:22guarantee that to within better than probably half a millimetre, even when you

1:27change the lenses. If all the lenses were perfect then once you’ve set the

1:32laser autofocus system up, you would never have to touch it again. It would always set

1:36this seven millimetre dimension here. Built into the RDWorks software in the

1:41vendor settings, for this machine there is something called a five millimetre

1:48offset from Z-zero. What we’ve got here at the side,is a switch and I’ll draw it

1:56like this. The five millimetres that I’m talking about is relative to this work

Transcript for Laser Machine Autofocus Pen (Cont…)

2:03surface. The table will move up, it detects the switch at that position

2:09there and calls it Z zero. Then it goes into its software and it moves the table

2:16down by five millimeters and resets that to zero. So this table position is now

2:26Z equals zero and it’s seven millimeters below the work surface. Now the problem

2:33is because the lenses might not have exactly the same focal point as you

2:38change the lenses, what we’ll have to do is to be able to set this switch to suit

2:44the lens in question. So as you change the lens over we shall have to change

2:49the switch position to give us whatever this dimension is. It could be seven

2:56point five dimension, it could be six point five, we’ll have to

3:01wait and see. Okay well let’s dive in and get started should we. Okay now before we

3:10start looking at how we set this pen relative to the nozzle,

3:17I’m going to be a bit rude and say that I am NOT very much in love with this

3:24piece of engineering here. It’s aluminium, it’s very very fragile, I

3:29have actually got thumb screws in here as opposed to the cap head screws that

3:35were in there originally. Because you’ve only got to put the smallest amount of

3:38pressure on there with an allen key and you’ll strip the thread. I’ve always used

3:43these two thumb screw things,they’re not all that steady look, they you can

3:48still wobble it. You can’t, you can’t put enough pressure on it to clamp this

3:52really securely. So before I show you how to set this up, I’m going to make a

3:59radical change to this design and we’re going to replace this with my own design.

Transcript for Laser Machine Autofocus Pen (Cont…)

4:04Before you even start to think about setting up this system, the one thing you

4:12must know is what the gap is we’re supposed to have between here and here.

4:17Now for most of these lenses it’s around about seven millimetres. It would be a

4:24wonderful dream if all the lenses were set to exactly the same focal point, so

4:31that you only had to have to set this once and then after that you could just

4:35rely on the auto focus to set the correct focal point for whatever lens it

4:39is that you’re using. If we look in here, we shall see that the lens is set quite

4:43a long way back down that tube and that’s because it’s a two and a half

4:48inch focal length lens. Now what’s in here at the moment is a two inch lens

4:53and the lens will be much closer to the front of this tube. There’s also a 4-inch

4:58lens which sits right back here, so the lens will go up and down according to

5:02its focal length but the focal point will always remain approximately

5:07seven millimetres below this nozzle. Now even if you change from one, 2 inch lens to

5:14another 2 inch lens, I would advise you to check the focal distance, because not

5:20all lenses are exactly the same. One might be a Plano convex lens and the

5:25other might be a meniscus lens for example. |Whenever you change the lens in

5:29your system here in the tube and from time to time you’ll need to change that

5:33lens in there, it’s always worth carrying out the focus check. The irony of this

5:40situation is that before we can do any calibration on here, we have to have

5:46something to reference it against and so what I’ve got here are some little step

5:51gauges. This one runs in steps of 1 millimetre between 1 and 20 millimetres

5:59and this one has got an extra half a millimetre added to the bottom of it,so

Transcript for Laser Machine Autofocus Pen (Cont…)

6:05it runs from one and a half millimeters to 20 and a half millimeters. So with

6:10these two gauges we can set any gap between work and nozzle to within half a

6:15millimetre which will be good enough. Now the lens I’ve got in here at the

6:18moment is a 2 inch lens, for each one of my lenses I have already worked out what

6:24the gap is between here and the work piece and they’re not all the same.

6:28For this 2-inch lens it’s 7 millimetres, so the first thing we’re going to do is

6:35to set this gap here to 7 millimetres. Just undo that,

6:40lift the nozzle up as high as we can get it. Raise the table,

6:49when we’re raising the table you can’t really take the surface of this table

6:53any higher than the surface of the frame.

6:59Otherwise it will hit the micro switch. Okay, so we’re now going to cut our piece of

7:05acrylic and make a new bracket that goes on here.

7:17The top surface that we’re going to see is perfectly clean.

7:22Now these little nick’s in here are to make it easier for me to locate when I

7:30drill screw holes, I’ve only got to locate the drill across the work

7:35approximately in the centre, because the drill will automatically focus onto the

7:40V and hold it in the correct position relative to the centre line of the hole.

7:48So first of all I’ve got to set my piece of acrylic up at 45 degrees like that, so

7:56that my holes run vertically downwards. Now I’ve already drilled and tapped

8:01those holes m4, but what I will do is show you how I went about tapping those

Transcript for Laser Machine Autofocus Pen (Cont…)

8:07by doing the last one. the V will automatically line the drill up this way all I’ve got

8:13to do is concentrate on getting it approximately in the centre of the V,

8:19like that.

8:25I’m going to remove the belt from the drill spindle so that the Chuck is

8:28rotating manually, because I’m going to do a bit of an engineering cheat and I’m

8:33going to use this drill as a hand tap, but I’m going to do it so that it holds

8:38the tap perfectly in line and tapping my m4 hole in there. Now what I’ve got is an

8:46o-ring, I could have used a small compression spring but I decided that

8:50people probably won’t have a spring, but you certainly might be able to get hold

8:54of an o-ring very cheaply and this will do the same job. So what I’m going to do

8:58is to snip a piece of that o-ring out, about a quarter of an inch long. It’s got

9:03to be approximately half the distance to this edge here. We’re now going to remove


9:16undo this, take it off remove the pen. Wow,

9:26so now we’ve really upset the settings, that were supplied with the machine.So

9:33hopefully, if I’ve designed this correctly that will be quite a nice

9:37slide fit in there, which it is and what we’re now going to do is to put

9:41the piece of o-ring into the hole that’s at the back there, that flat hole,

9:52and we’ll put in a m4 screw in behind it. We should see the o-ring just start

9:59to come through the hole. What we’re trying to do is to get this so that it

Transcript for Laser Machine Autofocus Pen (Cont…)

10:08is, when you tighten that screw up, you can still move it like this. It’s clamped

10:16but not clamped. It’s clamped but still able to slide around like that.

10:23Okay, so what we’ve done we’ve actually put a small compression system in there

10:27that allows you to adjust this very accurately and it will stay put and then

10:33through here we can now put a cap head screw. Because A:

10:40we’ve got a lot of material here and B: we don’t need much clamping load and we

10:44shall do the same in there. We’ll put a cap head screw in there. We’ve only got

10:48one clamp screw in here this time instead of two and that’s because

10:52basically what we’ve got here is a V block. I’ve changed the design so that

10:56it’s located here and here and clamped just there. So now when I slip that on,

11:03and put that back in there,

11:09like that. I shall be able to clamp that up and feel it snuggle up like that, put

11:17just a small amount of load on it and that will be really a nice stiff

11:22positive fixing for this. But bear in mind that this we can still move it

11:30around you could go back and look at session 10 to find out how you would

11:36find the exact focus for this nozzle. It really doesn’t matter where you do your

11:45location and reference from and we’re going to set it off a block, we could set

11:50it off this surface, but it might be too low. So the first thing we’ve got to do

11:57is we’ve got to raise the table so that we’ve got approximately seven

12:01millimetres under here well in this particular instance I know it’s exactly

Transcript for Laser Machine Autofocus Pen (Cont…)

12:04seven millimetres. 10, 9, 8, 7 is there, I’m gonna drop that down onto the gauge like

12:15that. Hands off, just so that there’s no pressure on anything and then I’m

12:20clamping it up. So that’s my seven millimetre position.

12:24This has to be switching exactly five millimetres above the same work surface

12:32and hey look I’ve got a five millimetre gauge here and I can now adjust this up

12:40and down until it just touches the step, but that’s not going to help me.

12:46So now we’ll come across to the keyboard and we’ll press the Z/U button and

12:52we’ve got to use the arrow keys to go right the way down to the bottom and

12:57down this list as well until we find diagnosis.

13:06Enter, and in diagnosis we shall find that we’ve got a series of basically

13:13indicator switches and just here we’ve got Z plus and Z minus. So if we now

13:22tweak very carefully the limit switch, the pen, what we should find is that at a

13:31certain point it will change. Pull it up and just gently put it down again,

13:38until you make the switch go red and there we go. Okay, so now we can tighten this one

13:45up, we can feel it now, snuggled up and what we can do is test it. We will just

13:55exit, escape from this screen and we get back to this screen here where we can

14:00press the up arrow until we get to autofocus. Now I purposely moved the block

Transcript for Laser Machine Autofocus Pen (Cont…)

14:07out of the way, just in case there’s any risk of

14:12something going wrong. Better safe than sorry, so if we press autofocus, enter

14:27and then it drops away five millimetres, which is why we used that five

14:32millimetre step,

14:37and now if it’s all worked properly we should find that we’ve got a seven

14:44millimetre gap underneath there, just like that. Look, absolutely perfect,

14:51seven millimetres. If all of a sudden I decide I want to do something, I want to

14:58clean my lens for example. So I need to take my lens out, well rather than take

15:04everything out we leave that behind, we shall often need to take that off to

15:10clean the end of the the actual nozzle itself to keep that nice and clear.

15:14Because that’s an, if you like something that people tend to overlook. Now we’ve

15:19done that, we put this back on

15:26and the first thing we do is push everything right to the top, push

15:32everything right to the top and tighten it up again.

15:35We’re guaranteed that our clamp is sitting down on this shoulder which is

15:39most important. Okay and from now onwards we’ve got the autofocus set. It doesn’t

15:46matter that we’ve had it off and put it back on again because this point, switch

15:53point here relative to that shoulder has not changed. We’ve got lots of space down

15:58below now we’ve turned the block over and let’s just do another autofocus. Run

Transcript for Laser Machine Autofocus Pen (Cont…)

16:04to the bottom of the list, autofocus, Enter.

16:28So we’ll just use the real world to check again five, six, seven, they won’t go

16:37on eight and it’s just a lovely slide fit under seven. So that switch is set

16:44absolutely perfectly, now you’ll need to do the same thing for every lens that

16:50you’ve got in your system. Check where it’s true focus point is and come back

16:56and do this same procedure. Now if you didn’t make these the first time round

17:00and these are made out of five millimeter material just so that they

17:03stand on their edge and are self-supporting. If you find they’re not

17:07exactly the dimensions that are shown on here either you can tweak them yourself

17:12or leave them as they are because you’re not interested in real-world dimensions

17:18what you’re interested in is the numbers that are on these here. So for instance I

17:25don’t know whether that dimension that I’ve just set there is exactly seven mil

17:29it may be 7.3 it doesn’t matter because whenever I set it up I’m using this


17:37Some very observant person is going to say, “yeah but look I’ve got a screw here,

17:45if I undo that screw I can adjust the micro switch from up here”, yes you can do,

17:54but it’s a lot more fiddly and you don’t have the same precision control that you

17:59do down here with my friction system that I’ve introduced. This will be very

18:05much more difficult to actually set, so I would advise you not to touch this one

Transcript for Laser Machine Autofocus Pen (Cont…)

18:11and just do your settings down here with this one screw. Now I’m personally not a

18:16lover of the laser autofocus system because it gets in the way of me messing around

18:22with the Machine far too much and I’m going to give you an example of that now.

18:27Look we’ve just set this up to etch for example on this surface, fantastic.

18:39If I want to raise the job and I go to Z/U and I try and raise the job, I can’t.

18:47I can lower it, but I can’t raise it. It’ll only come up to zero which is the

18:55autofocus position. So all it will ever do now is come back and set to seven

19:03millimetres IE zero Z. So if I want to for instance go and engrave something on

19:10there what I’ve got to do, is I’ve got to go all the way through to Z/U and

19:17down to autofocus again.

19:40Which is fine, but I now want to set up for another job and I want the table up

19:47how do I get the table up because it’s already at zero. So when you start the

19:52Machine up when you press reset, it automatically cancels your auto zero and

20:05now you’ve got full control of Z and that’s how I tend to operate the Machine.

Transcript for Laser Machine Autofocus Pen (Cont…)

20:11Because if all of a sudden I want to bring for instance that surface into

20:15play Z/U button, raise the job up, I just

20:18drop my gauge under there with the seven mil step, let that drop down onto it, job done!

20:27The only reason I could see, that you’d want an auto focus system, is if you wanted to

20:33do some sort of in-process change of height. Now I don’t know what the in

20:40process change of height would be, I’d not discovered anything in the work that

20:45I’ve been doing over the past two years where you have to change the focus

20:48height during the process. There is a myth going around that if you want to cut

20:54thick material you should drop your focus point to something like about a

20:58third of the way into the material. Well all the experimentation work I’ve done

21:03shows that I don’t get any advantage. I leave my focus point set always on the

21:11surface of the job and just adjust the speed to get the cut right. Now although

21:16I’m not a convert to this system, I’m very happy to make it stable and to show

21:22you guys how to set it up. If you have a real need for it within your process

21:27then fine. In theory this is a good idea, in practice it’s about as useful as this

21:35other thing that I have strapped up. This is the red dot pointer, so when you’re

21:41not looking I shan’t be using this laser autofocus system. I

21:45can leave it like this, it’s not dangerous like this and I will be able

21:49to set this up in a tenth of the time that it takes for the

21:53laser autofocus system to work and it gets even worse if I’ve got a very small

21:59product that I want to put on there for instance let’s just say I want to

Transcript for Laser Machine Autofocus Pen (Cont…)

22:03autofocus on that now. Let’s just see what happens. All the way down to autofocus,

22:11press the enter button.

22:21Ah it’s now hit the limit stop for the table and so what it will do it will

22:26find its limits position there and then it will drop down to a safe position,

22:32like that and now I can drop this down until it just about touches the

22:39surface and then I can lock it up and now I’ve got to go through the whole

22:43process again. So we’ve got to set the Z/U button, go down to autofocus and

22:51press Enter.

23:09I’ve just wasted a minute of my life and at my age I can’t afford to do that. Well

23:17here we are at the end of this session and I’ve got to make it very very clear

23:23that some of the opinions that I have expressed are very personal opinions,

23:29there is no criticism of Thinklaser and the product that they are selling. This

23:35is a well engineered product and it is in demand by the marketplace, so all that

23:41Thinklaser are doing is satisfying that demand. It’s just that the marketplace

23:46doesn’t realise that there is very little use for this lovely feature. If

23:50you’re going to do some acrylic origami work and I’ve seen some great stuff

23:54online well I was quite excited at the possibility, but I’ve never got around to

24:00it. The need has never arisen, I haven’t got a business that would require it, but

Transcript for Laser Machine Autofocus Pen (Cont…)

24:05maybe you’re in a business where you have got that specialist niche that

24:10really requires this laser autofocus system, but I hope today that are demonstrated

24:15that those people that think they need it probably don’t really need it. It would

24:19be a lot quicker to set the Machine up manually. I don’t want to take anything

24:23away from the quality engineering that’s been built into this machine. Well thank

24:29you very much for your time and your patience for listening to the rantings

24:32of an old man. I shall see you in the next session.

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Last updated August 26, 2021


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