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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Transcript for Laser Beam Alignment Procedures
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0:00well welcome back to RDWorks
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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