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
