Number 09 – RDWorks Learning Lab 051 – Laser Beam Alignment Procedures for Beginners Part 1

The Top Ten RDWorks Learning Lab Videos

These are the top ten RDWorks Learning Lab Videos ranked by average number of views per month. In this session, Russ shows us his Laser Beam Alignment Procedures.

Contents

  • Must ensure that mirror mounts 1 and 2 are true 45 degrees and same distance off the Y axis rail
  • Must set the laser tube parallel to the back and bottom face of the enclosure by using packing blocks.
  • Check entry into mirror 1 is central.
  • These tedious setting will only need to be done once.
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Laser Beam Alignment Procedure - Setting Mirror 1
Laser Beam Alignment Procedure – Setting Mirror 1

Transcript for Laser Beam Alignment Procedures

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0:00well welcome back to our D works

0:02Learning Lab we left off last time

0:04having just successfully tested my new

0:07baby it’s in it’s working and it’s

0:10powerful now all we’ve got to do is to

0:13set the beam up so that it gets through

0:16to the work I’ve tried several methods

0:18of setting the beam up in the past and

0:20every time I do it I find something new

0:23so I decided I would sit down this time

0:25and think about it completely logically

0:28what I’ve done hopefully this time has

0:30organized a complete logical set of

0:33steps that you should go through to set

0:35your machine up now the first thing you

0:38must do is mistrust the machine let me

0:42explain I want you to imagine yourself

0:44as a laser beam traveling down that tube

0:47and getting to that first mirror now

0:52although the mirror starts off life as a

0:5425 millimeter disc but the time you tip

0:58it through 45 degrees look what happens

1:01to it it’s turned into an oval now

1:05that’s what this picture is showing you

1:08what we’ve got here is a picture of the

1:11mirror as the laser beam sees it and

1:13this is the laser beam itself now the

1:17laser beam is only six millimeters

1:19diameter but by the time the mirror is

1:22tipped over okay although it’s still

1:24twenty millimeters tall as opposed to

1:26twenty-five millimeters tall because

1:28it’s just encased in a little enclosure

1:30there in the other direction we might

1:34have as much as 12 millimeters it might

1:37be 11 millimeters but it’s in that sort

1:40of region 11 or 12 millimeters now what

1:43that means is that we’ve got a very

1:45narrow target to aim at for a long time

1:50for some stupid reason I thought I’d got

1:53quite a large target to aim at and it

1:55wasn’t till I thought about it which I

1:57should have done before but I realized

Transcript for Laser Beam Alignment Procedures (Cont…)

2:00that it was quite a narrow target that

2:03we’re aiming at and we’ve got to be

2:05pretty accurate with our laser beam and

2:08our mirror alignments so

2:11if we got a six millimeter beam and a 12

2:15millimeter wide mirror we’ve got three

2:18millimeters each side maximum so I can

2:23only really sensibly afford to have my

2:25beam two millimeters off-center to play

2:30safe so I want you to keep that fact in

2:34mind we’ve got to get the beam within

2:36two millimeters of the center of the

2:38mirror all the way through the system so

2:41here we’ve got the laser tube with the

2:43laser beam coming out of it hitting

2:44mirror number one now ideally it should

2:49run along here absolutely parallel with

2:53this y-axis bearing rail that’s what

2:57we’re trying to achieve now we’re trying

2:59to achieve that parallel beam to this

3:01bearing rail in not only the plan view

3:04which is what we see here but also in

3:06the horizontal view as well so this beam

3:09has got to run true in both axes to this

3:12bearing rail okay that’s what we’re

3:17trying to achieve now let’s just take a

3:19look here at mirror number one now it’s

3:24coming off of mirror number one and for

3:27it to run along parallel with this axis

3:30here and hit the center of the second

3:32mirror the mirror has got to be in the

3:36same relative position to the y-axis

3:39bearing rail as mirror number one now

3:43that’s I can’t afford to have this

3:45mirror here out of line mechanically

3:48because if it’s out of line mechanically

3:51when I try and point the beam to the

3:54center of this mirror it’s not going to

3:56cleave parallel with this axis so as

3:59you’ll never be able to achieve the goal

Transcript for Laser Beam Alignment Procedures (Cont…)

4:02that we’re looking for which is

4:03parallelism in between the beam and this

4:05axis so the very very first thing that

4:09we’re going to have to do because this

4:12is like the foundation of the whole beam

4:16setup we must make sure that mirror

4:19number two and mirror number one are

4:21mechanically in line with this YX

4:25if they’re not we’ve got to fix it we

4:29can’t afford to have these out by more

4:31than a millimeter because otherwise if

4:34we stick with our plus or minus two

4:36millimeters we should be touching the

4:39edge of the mirror this is going to be

4:41an interesting problem and it’s going to

4:42test your engineering ingenuity because

4:46there are very few things on the machine

4:48that are what I call good enough to use

4:51as a reference I thought we might be

4:53able to use the Machine case here this

4:56this is the green machine case as a

4:58reference but when I put a straight edge

5:00along this surface here it’s probably

5:03out by a mill mill and a half but my

5:05original plan was that what I was going

5:07to do was to use this as case plane as a

5:10reference measure from there to the rail

5:13there to the rail and then from that

5:16same reference to the center of that

5:18mirror and that reference to the center

5:20of that mirror and with a little bit of

5:21maths we would been able to work out

5:23what the difference between these two

5:25lines was not possible so we’re going to

5:31have to think of some other method what

5:33I’m going to do to make to make more

5:36room for myself is to take the mirrors

5:38actually off of the block because the

5:41mounting block is the more important

5:42thing that I’m interested in at the

5:43moment

5:44if the mounting block is right then I

5:47can use that as a reference to set my

5:49mirrors up I’m no longer frightened of

5:54taking mirrors often messing things up

5:58there was a time when I first had this

Transcript for Laser Beam Alignment Procedures (Cont…)

6:00machine it was one of the most fearful

6:02things that I dreaded if I messed my

6:04mirrors up would I ever get them back

6:05into line what I’d like to do to start

6:08with is to actually check that this

6:12mirror plane here is actually sitting at

6:1645 degrees to the basic squareness of

6:20the machine now we’ve got to make some

6:22fairly mmm sweeping assumptions I

6:25suppose about the way that this machine

6:27is made the machine is obviously made

6:31with jigs all this lots welded together

6:34it’s all punched formed and welded

6:37together on some sort of jigs

6:38so we have to assume a certain degree of

6:40squareness and trueness about this frame

6:43what I’m actually checking at the moment

6:45whether this block is sitting here at 45

6:47degrees relative to the back face of

6:51this enclosure and the answer that

6:54question is yes so that’s a pretty good

6:58start the fact that we’ve got the block

7:00at the correct angle now this mirror

7:03block is exactly the same as the mirror

7:04block at the back the other thing that’s

7:06interesting is after two weeks

7:09well after nearly three weeks now

7:12there’s my copper mirrors do they look

7:15tarnished no so you just wind these

7:19screws back out away now it’s going to

7:23be a little bit more difficult to

7:25measure the 45 degree angle on this

7:28block I’ve either got to measure it

7:30against this rail and to be honest I do

7:35know that there is a very high degree of

7:39squareness between this rail and that

7:41rail so probably I better to use this as

7:44a measure of my 45 degree squareness

7:47than anything else now a nut doesn’t

7:50sound like a piece of engineering

7:51measuring equipment but this perspective

7:55lock has been machined and polished so I

7:59know that it is very good true and

Transcript for Laser Beam Alignment Procedures (Cont…)

8:02square so what I can do is to use this

8:08as a reference off the front surface

8:10there and slide my 45 degree against it

8:20and I can see that it’s probably maybe 1

8:23degree out it needs twisting slightly

8:28now it may well be not only that it

8:31needs twisting but it may need

8:34repositioning so that’s the next issue

8:36how are we going to check for the center

8:39well I don’t think we are going to be

8:41able to check for the center but what we

8:43can do well as far as I can see the

8:45block at the back is 45 point oh 9 wide

8:51and this block here is 44.9 one so if we

8:57said they were 45 millimeters wide those

9:00blocks that’s going to be probably good

9:04enough but I really have got to have

9:08this set at the correct angle before I

9:10can use what I want to use is one of

9:12these edges here or both the edges to

9:15set myself up a reference so you need to

9:20loosen the screw off underneath there as

9:31far as I can see as I slide that onto

9:33there that’s perfect so the angle is now

9:37correct to 45 degrees but we don’t know

9:44about the position of the center of the

9:47mirror so now what we’re going to have

9:50to do is be a bit inventive about how we

9:54achieve that well here’s my solution

9:58I’ve got some VHB s a very high bond

Transcript for Laser Beam Alignment Procedures (Cont…)

10:03strength tape there we go that’s a piece

10:07of tape on there and I’ll do the same on

10:10the rear block now not everybody will

10:17have this in their workshop but I just

10:18happen to have a piece of stainless

10:21steel square tube here which is around

10:25about 15 mil square and it’s just

10:28perfect for doing what I want to do I’m

10:32going to poke it through the hole that

10:34goes to the back of the machine there

10:35now ideally what I want to do is to pick

10:38up on that vertical edge there and sit

10:41my piece of two in line with that

10:45vertical edge which is what I’ve just

10:48done there

10:52I’ll just stick it down so that it

10:54doesn’t move and I’ll do the same on the

10:57back mirror okay so now I’ve got myself

11:01a straight line through the corners of

11:05these two blocks now if I shift it

11:07across by the same amount it will

11:09eventually get to the center of the

11:10mirrors so basically what I’m doing is

11:12checking the center line of the mirrors

11:15or these blocks and now I should be able

11:18to reference between here and here and

11:21here

11:21let’s go back to my big block of acrylic

11:24because that looks like a very useful

11:25size I can stand it on that rail if I

11:29put those two together there that should

11:33make a flat surface which it does so I

11:43can now move that to the back and see

11:50how that compares with what I find right

11:53at the back there now I can always I can

11:57tell you now before I look there’s about

Transcript for Laser Beam Alignment Procedures (Cont…)

12:01a meal and a half difference in the

12:04height it’s not quite as important in

12:06the up-and-down direction because

12:09remember we’ve got 20 millimetres to

12:11play with we’ve probably got at least

12:14plus or minus 4 or 5 millimeters from

12:16Center before we start having a serious

12:18impact on our beam collision with the

12:21edge of the mirror well as I mentioned

12:24before we started we’re gonna have to

12:25build a bit engineer ingenious about how

12:28we establish whether or not we’ve got a

12:31reasonable dimension here because

12:32there’s nothing to work with so what

12:36I’ve done what I’m going to do here I’m

12:38going to use the top of this rail as a

12:40flat reference I’m going to sit my block

12:44here on top of that rail and slide it

12:45across very gently until it just touches

12:49the rail and at that point there what

12:52I’m going to do is to measure the step

12:56difference

12:59to the rail which is three millimeters

13:02then we’re going to come to the front

13:03and trying to do exactly the same thing

13:07hold it square on the top of the rail

13:09layer and slide it across till it just

13:13touches and that’s 2.99 as opposed to

13:16three point zero eight so I think near

13:20is damn it those mirrors are in line

13:24which is very important so let me very

13:27carefully tighten these screws up I only

13:29just cracked them very gently do those

13:34nice and tight because we don’t ever

13:36want to have to fiddle with that block

13:37again this is a once-off setting now it

13:42might be crude but even if it’s a mill

13:45out it’s better than it being two or

13:47three millimeters out and you never

13:49being able to get your alignment correct

13:51it is not proper engineering as you’ll

13:54understand but I haven’t got a metrology

13:58lab to back me up so we have to we have

Transcript for Laser Beam Alignment Procedures (Cont…)

14:01to go to garage technology so the only

14:05error that we found in these blocks mmm

14:07basically is this one is a millimeter

14:09higher than the one back not a problem

14:13okay well we’ve now built our solid

14:16foundation upon which we can start our

14:19beam alignment it was important that we

14:21had these mirrors set at 45 degrees and

14:24it was important that a line joining the

14:27center of this mirror and the center of

14:29this mirror was basically parallel in

14:31both the vertical and the horizontal

14:32axis with this bearing rail okay we now

14:36put the we now fix the block back on and

14:39now comes the next vital trick what

14:42we’re going to do is to put some a

14:44little bit of movement on this block and

14:48then I’m going to put that in there and

14:50I’m going to undo the back line until it

14:52just nips like that

14:58now just tighten it up until I can just

15:01get my piece of wire out which is 1.5

15:04millimeters wide and then I’ll do the

15:07same at the front here our nip it in the

15:08front here

15:09under the screw until I nip it in there

15:14tie now till it just comes out there we

15:20go now do the same for the top now in

15:22doing that what I’ve actually done is

15:24set that block up absolutely parallel to

15:28this block so technically that mirror is

15:31now sitting at 45 degrees the same as

15:33the block we’re going to the same to the

15:36front mirror now and there we go so

15:40that’s the preliminary settings done and

15:45you notice we’ve not even turned the

15:47machine on yet now I know that these

15:49blocks are correct because when I was

15:51having problems before I managed to draw

15:54these blocks up and I checked the

15:55geometry of these blocks so they know

15:58that the center of the mirror is where I

Transcript for Laser Beam Alignment Procedures (Cont…)

16:00expected to be in the center of the hole

16:02so if we aim the laser for the center of

16:06the hole then I know that we’ve got it

16:08set up approximately on the mirror

16:11Center as well give or take half a

16:14millimeter or so I suspect when I made

16:17the holes to fix my clamps down I made

16:21them into slots although I’ve got this

16:24set to a nominal position I think I

16:27might need more than the three

16:28millimeters that I’ve got on here to

16:31find the correct position in the middle

16:33there so what I should do is loosen the

16:35screws off to start with to get a

16:36nominal starting position just like

16:40enough the nuts now so my tube the base

16:45plate for my tube is actually able to

16:48float around and for the first time

16:52we’re going to have a quick check to see

16:55where the beam is now many of you will

16:59be asking the question why am I not

17:02using my little red dot pointer well the

17:06answer is quite simple from experience

17:08the mark 2 and the mark 3 they were

17:13pretty good on a from scratch setup but

17:17many people won’t have the pointer so

17:20what I’m using here is the standard

17:22technique

17:23which I actually still find much to my

17:26horror is actually the easiest and best

17:29technique to use now what we’re going to

17:32do is turn the power right down on this

17:35tube to about 10% see what’s happening

17:38as I press the pulse button no that’s

17:41good now I just do a little pulse test

17:45and not far off center so I will just

17:52pull this across very very slightly at

17:54the front here

17:59because basically whatever I pull across

Transcript for Laser Beam Alignment Procedures (Cont…)

18:01here will appear there but it’s

18:05completely different at the other end we

18:07sort that out in a minute and I’ll show

18:09you what I mean so we just do a pulse

18:14test here slightly over cooked it

18:23just push it back a shade

18:32I would say that that looks pretty good

18:34for Center we can check it again the

18:38great thing about this is you can sort

18:40of it’s semi opaque you can see where

18:43I’m aiming so let’s try that one more

18:48time yeah that looks pretty good this is

18:55the back of the enclosure

19:03and what we’ve now got to do is to make

19:06sure that we set the tube parallel with

19:12the back face of the enclosure so what

19:16we’re going to do is make sure we’re

19:17going to measure or we’re going to put

19:19Packers which is the easiest thing to do

19:21put packing pieces down the back of the

19:23tube to make sure that it’s the same

19:26distance away there and there so then we

19:30can know that we’ve got the tube

19:32pointing 45 degrees near enough at our

19:37mirror which is 45 degrees and if we get

19:41that bit right then nearly we should be

19:45in the middle of that mirror we won’t be

19:48quite I guess we won’t be far out but

19:51let’s give it a try now I’ve got a whole

19:56box here of random packing pieces from

19:59for my tests 10 millimetre 4 millimetre

Transcript for Laser Beam Alignment Procedures (Cont…)

20:0315 millimeter and there’s a piece of 12

20:06millimeter

20:13and another pole another piece of 12

20:15millimeter so that is a perfect fit

20:21there two big pieces so we know come to

20:25the other clamp and we’ll see what we

20:29got here

20:30no look we can’t get two pink pieces

20:33down there so what we’ll do we’ll slide

20:35this across until we get two pink pieces

20:40down there just like that there we go so

20:43now we know the tube is set up nice and

20:47parallel but now that we know we’ve got

20:50the beam parallel to the back face of

20:53the machine

21:01we do a quick test

21:07and I think this neros makes no

21:09difference we regard that as being

21:12central up and down mmm but we haven’t

21:17happened down yet and it’s certainly

21:20central left to right which is great

21:22Lewis now we’ve got a piece of 15 mil

21:27there and look about a piece of four

21:32millimeter ply fits perfectly underneath

21:35there but another piece another piece of

21:39this 15 millimeter acrylic under here so

21:42if you need to undo the clamp and lift

21:45it up and we’ll lock it up in that

21:47position at the moment so that’s the

21:51next stage done which is setting the

21:54beam up parallel in two planes before it

21:59gets even to the first mirror we won’t

Transcript for Laser Beam Alignment Procedure (Cont…)

22:02have just one more quick pulse test

22:04there we go

22:05we’re happy with that so that’s stage

22:08one sorted I’ve still got my packing

22:13pieces behind and underneath the tube

22:15because we should be coming back to this

22:18area later on in the procedure but at

22:20the moment we’ve built a good foundation

22:23from which we can now start aligning the

22:25beam

22:34you

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