10 – Understand and Care for your Lenses (51:11)

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 video, Russ goes into detail regarding conventional lens theory, including focal length, dot size and energy density. He also covers the procedure for the handling and cleaning a laser lens.

Cleaning a Laser Lens
Cleaning a Laser Lens

Contents

  • Focal length of lenses
  • Size of dot and energy density
  • Reason for having different lenses
  • Useable Focal Depth
  • Making a focus ramp to find exactly where your focus point is
  • Engraving – a first look, scan layers, engraving in reverse, speeds and power
  • Order of engraving, cutting holes and cutting the outside shape
  • More on grouping
  • Focal points relative to the material
  • Condensate on acrylic
  • Assembling the ramp
  • Using the ramp
  • Removing a lens (Zinc Selenite), cleaning it, Isopropyl Alcohol, lens tissue
  • Replacing the lens
  • Importance of air assist
  • Fitting a non-standard 1.5” lens in custom-made holder
  • Paper and detailed work and ideal focal length

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 Cleaning a Laser Lens & Care of Your Lenses

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00:13

Welcome to another Lightblade Learning

00:16

lab. Today I hope is going to be very

00:19

interesting session, it’s going to be

00:21

packed with lots of tips and features

00:23

and some very important facts about the

00:26

machine itself. Now before you get

00:29

started

00:30

I don’t want you to fall asleep i would like

00:32

you to put this on pause for a few

00:34

moments go and get yourself a cup of

00:35

coffee and while you’re about it

00:38

can you hunt down an old style wooden

00:40

pencil with a lead sticking out the other

00:43

end and make sure it’s nice and sharp

00:46

and then come back and we’ll restart the

00:49

session

00:53

great well hopefully you’re now going to

00:55

be fully aware because we said we’re

00:58

going to start benchmarking the Machine

01:00

now there are many different ways where

01:02

we can start benchmarking the Machine

01:04

benchmarking basically means putting a

01:05

peg in the ground so that we know what

01:07

the performance of the machine is now

01:09

because in six months time three months

01:12

time whenever our machine might degrade

01:15

and it would be good to have the tools

01:17

to know that the machine is no longer in

01:20

tip-top condition and you can either

01:22

have a go at fixing yourself if you feel

01:24

confident or if you’ve got the right

01:26

tools to demonstrate that something has

01:28

changed seriously you can probably

01:29

called Thinklaser in and they will fix

01:31

the problem for you

01:32

ok we could start the laser tube and

01:38

we’ve already discussed the laser tube

01:40

in quite great detail so you know how

01:42

important it is and how it works

01:43

once the laser beam comes out of the

01:45

tube it has to pass around the machine

01:48

via a series of mirrors

01:49

now the mirrors themselves we’ve touched

01:51

on a little bit with reflectance and the

01:53

danger of the beam etc we’re going to

01:56

concentrate on mirrors in a completely

01:57

separate session because they’re a big

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

02:00

subject all on their own and then

02:02

finally we’ve got to get to the lens now

02:06

the lens is the most important part of

02:08

the system because without the lens you

02:11

don’t have a useful machine so today

02:14

what I’m going to do is concentrate on

02:16

trying to give you a conceptual

02:18

understanding of what this lens does and

02:21

understanding of why you’ve got two or

02:23

three or four different lenses with your

02:25

machine there maybe some of you that

02:27

never did any science lessons there

02:29

maybe some of you that did attend

02:31

science lessons but at the point in time

02:32

when the science teacher was trying to

02:35

teach you about optical paths and bits

02:37

of glass and bending light your hormones

02:39

were probably to the fore and you

02:42

weren’t really interested you were more

02:44

interested in the um… the young lady at

02:47

the back

02:48

let’s just start from square one and

02:50

give you 1 or 2 very basics about lenses

02:52

because the way that I want to describe

02:54

them to you hopefully will be memorable

02:58

now I’ve got a picture on the screen

02:59

here of three lenses now they will look

03:02

the same because that’s just my laziness

03:05

the way that I’ve drawn them but they

03:07

have got something called a focal length

03:10

now depending on the shape of the lens

03:13

the laser beam comes in from the top as

03:16

a parallel beam it passes through the

03:19

lens and then its shape changes now

03:24

depending on the focal length of the

03:27

lens and here I’ve shown three different

03:30

focal length lenses we’ve got a

03:31

one-and-a-half inch lens thirty eight

03:34

millimeter at Owens lens which is 51

03:36

millimeters and a two-and-a-half-inch

03:38

lens 64 millimeters that each of those

03:41

lenses has got different properties the

03:46

Key property is the size of the dot at the

03:50

focal length now that determines

03:53

something called the energy density of

03:56

the beam itself now I don’t want to go

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

04:01

into too much detail on energy density

04:04

at the moment but you’ll hear me using

04:05

this word energy density quite a lot and

04:09

it’s very important that you understand

04:11

what energy density is now did you get

04:15

that pencil i asked you to find well if

04:18

you did then what I’d like to do is to

04:21

pick it up

04:23

and with the blunt end of the pencil

04:26

push it into the palm of your hand as

04:28

hard as you can

04:30

you can do it very hard and it doesn’t

04:35

hurt it might make a little mark but it

04:36

doesn’t hurt

04:37

okay now turn the pencil round and

04:43

cautiously pressed into the palm of your

04:47

hand point first now I guess that it

04:50

isn’t going to be very long before you

04:52

say all I can’t do that very hard

04:55

ok if you were to apply the same amount

04:59

of pressure that you did when you’re

05:00

pressing the blunt ending you’d probably

05:02

push the pencil right through your hand

05:03

what we’ve done we’ve concentrated the

05:08

energy that you have applied to that

05:10

pencil into a very very small area ie

05:14

the point and you can do a lot of damage

05:18

with the point but you can’t do much

05:21

damage with the blunt end of the pencil

05:24

now the key word here damage and energy

05:28

density sit side-by-side and that’s what

05:32

I want you to remember energy density

05:34

equals damage so the lower the energy

05:38

density the less damage you’re going to

05:40

do to the material

05:42

ok that’s an important lesson about the

05:47

concept of energy and bear in mind that

05:52

this energy that were firing at this

05:53

lens is invisible

05:55

it’s not light that you can see it’s

05:59

actually heat energy we’re concentrating

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

06:00

this energy this hate energy into a very

06:04

very powerful beam and at the focal

06:07

point it’s able to do a huge amount of

06:10

damage

06:11

ok so the focal points we’ve got three

06:14

different focal points here why do we

06:16

need three different focal points

06:18

well if we take a look carefully at the

06:22

shape of the paths that the beam is

06:24

taking you’ll see that the thirty eight

06:27

millimeter it has got a wasting it

06:30

doesn’t actually between doesn’t

06:31

actually cross over and come to a real

06:33

sharp nothing point it has some spot

06:38

size right at the 38 millimeters

06:40

dimension and it comes in and out very

06:47

quickly and I’ve drawn a dimension in

06:49

there 14.6 62 that’s rubbish

06:52

basically it’s more like in the real

06:54

world it’s more like 1.4 millimeters in

06:58

other words plus or minus about plus or

07:00

minus half a millimeter that’s what they

07:02

called the usable focal depth now that

07:06

basically means that the energy the

07:08

energy density is approximately uniform

07:11

over only points7 of a millimeter above

07:16

and below the focal point so you have to

07:18

be very accurate with your focusing to

07:21

get the best out of your beam now when

07:25

you get to the 51 millimeter 2-inch lens

07:28

you’ll see that that 1.4 millimeters and

07:31

let’s divide the numbers by 10 has

07:33

changed to two millimeters so we’ve got

07:36

plus or minus a millimeter now we’ve got

07:38

a little bit more flexibility in the

07:42

range that we can use the lens and then

07:45

we’ve got the 64 millimeter or the

07:47

two-and-a-half inch lens and you’ll see

07:48

that that’s gone up to two and a half

07:50

millimeters we’ve got an even wider

07:52

range of operating for instance the 51

07:57

millimeter lens has got less energy

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

08:01

density then

08:03

the thirty eight millimeter lens and

08:05

similarly the 64 millimeter lens has got

08:07

less energy density than the other two

08:10

if you want to do the same amount of

08:13

damage with a longer length lens you

08:15

have to have more powerful machine now

08:19

these are concepts that you want to deal

08:21

with in another session completely all

08:23

about energy density and the way in

08:25

which you could use your lenses today I

08:28

want to purely talk about the focal

08:30

length and what I’ve tried to describe

08:33

there is the usable focal length

08:36

changing and why it’s important to make

08:39

sure you get your lens set correctly for

08:42

the focal length on the job that you are

08:45

doing so this is not a subject that we

08:49

can just pass over you need to

08:51

understand about lenses now the machine

08:54

has got an autofocus system on it but so

08:58

I want to tackle the problem from the

08:59

grassroots section upwards and then will

09:01

work back into the autofocus system

09:04

ok so we’ve got to do two things when we

09:09

get to our machine

09:10

we’ve got to establish what focal length

09:14

lens as in the machine to start with and

09:17

secondly we’ve got to establish whether

09:18

or not the machine has got it set

09:21

correctly IE if its a 50 1 millimeter

09:25

lens is the lens set 50 million 51

09:28

millimeters above the workpiece that’s

09:31

important

09:33

how do we do that well I’m afraid there

09:37

is nothing really on the machine that

09:40

allows you to find that out you could

09:42

play around for ages with the spot size

09:46

and see if you can get the thinnest

09:49

possible line we’re going to use this

09:52

session again to make another very

09:54

useful tool that will help us determine

09:56

exactly where the focal length is for

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

10:00

the lens now what we’ve got here on the

10:02

left some paper targets and in the first

10:05

instance we don’t need those as I said I

10:08

always put my designs together in one

10:12

dxf file so that we can import them all

10:15

at once so first of all we delete the

10:17

half that they don’t need and then we’ll

10:20

also delete the material which is five

10:22

millimeter acrylic and and i showed you

10:24

how to cut vector text last time equally

10:28

well what we could do we could put this

10:32

on a separate layer and first of all

10:34

we’ll group it very important this key

10:37

grouping things because now all I’ve got

10:40

to do is touch on one part of that and

10:43

it brings the whole lot up and i’m going

10:46

to put that onto a blue layer and the

10:50

blue layer I’m going to turn this blue

10:53

layer this time instead of a cut layer

10:55

we’re going to turn it into a scan liar

10:58

so this is our first introduction to

11:00

engraving you’ll notice that I’ve got

11:03

the text backwards that’s because i’m

11:06

going to engrave and cut from one side

11:10

of the job but that side of the job is

11:13

actually the back side of the job so I’m

11:16

going to engrave on the back of this

11:18

acrylic so that when you look through it

11:21

from the front you will see a nice piece

11:24

of white text and first vote for

11:27

engraving you will always need to be

11:29

running at high speed now 200 300 400 it

11:35

makes some difference but not a great

11:38

deal of difference the main difference

11:39

it will make is to the depth of the cut

11:41

that you will achieve so I will leave

11:45

this 202 our well I would think we

11:50

probably need to push the pair up to

11:51

maybe river i’m guessing let’s just say

11:55

twenty percent i’m going to put these

11:57

numbers the same

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

12:01

and down here we get other options which

12:04

appear until we talk about it otherwise

12:08

leave / striking his son process and

12:11

leave scan mode as X swing and that’s

12:16

all we need to do so we’re going to cut

12:19

five millimeter acrylic let’s set the

12:23

parameters for cutting speed difficult

12:27

to say on this machine as i said i’m

12:29

guessing because i haven’t got much

12:31

experience with it

12:33

let’s play safe and go down to as little

12:35

as about eight millimeters a second and

12:40

sixty-seven percent power which I’ve

12:42

already used elsewhere which is the

12:44

maximum i can use for this machine so

12:47

all we’ve got to do now is to decide how

12:49

we want to order the cuts now here’s

12:52

where i’m going to show you a few more

12:54

tricks over and above what I’ve already

12:56

shown you what we’ve got to do is

12:57

probably engrave it first then cut the

13:00

holes and then cut the outside shapes

13:02

that’s the order that we’ve got to think

13:03

of but what I’m going to do I’m going to

13:05

grab hold of all of the holes there to

13:07

start with and they were turned into a

13:10

raid group but hang on I’ve also caught

13:14

focus ramp as well that’s turned rate

13:16

and I don’t want focus ramp in that

13:19

group

13:20

so what we do where is up to now I’ve

13:24

shown you how to add things to a group

13:26

by holding the shift key down press the

13:29

shift key down and touch on focus

13:33

and now with subtracted focus from the

13:37

group you can now let go of the shift

13:40

key and we got there more group and what

13:43

we grouped is just the holes so you can

13:47

use your shift key for additive or

13:49

subtractive grouping ok now in the same

13:52

way we can just grab the whole outside

13:55

shapes like that

13:57

hold down the shift key touch on touch

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

14:00

on a ramp touch on a whole group so we

14:05

don’t have to collect the pieces

14:06

individually additively we can also

14:09

collect the pieces by subtracting

14:11

something from the whole now that’s

14:14

quite an important time saving tricks

14:16

sometimes when you get very complex jobs

14:18

or when you select something wrongly and

14:22

you want to subtract just one or two

14:24

items from that grouping I’m going to

14:27

say this is focus one short name but

14:33

I’ve got another focus file to come out

14:34

as well so we save that has focused one

14:36

onto the onto the memory stick

14:40

have a good day then kill and this is

14:45

another trick now we really need the

14:47

other part of the file to do now but we

14:52

could markey this clear the page delete

14:57

it and import it again that’s tedious

15:00

look let’s just do controls it

15:04

123456 we can go back quite a long way

15:13

with controls it and get back to the

15:15

beginning of our import file and now we

15:19

can do the opposite

15:21

we can delete the bit that we don’t need

15:23

which is that bit delete the frame and

15:26

we delete the card specification now

15:28

what we’ve got here is scorched text on

15:34

a piece of card and it outside shape now

15:39

the outside shape again let me just show

15:41

you has got a gap in it at the top and

15:44

at the bottom so these pieces remain

15:47

attached to the card it looks very

15:50

complex to program this it’s not because

15:55

first of all we’re going to do this

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

16:01

and I’ve captured all the text will put

16:05

that into a group and put it onto a blue

16:08

layer now the blue layer is going to be

16:14

a cut layer so we need to make sure that

16:17

it’s cut but we’re not really going to

16:20

cut it what we’re going to do is scorch

16:21

it with cut lines so we’re going to cut

16:25

poorly basically and we’re going to do

16:28

that by talking taking the power down to

16:30

something like about maybe ten percent

16:33

very very low power as well as we can

16:37

get it and the speed well we need the

16:41

speed quite high

16:43

we tried to the hundred because we don’t

16:46

want to burn through we just want to

16:47

scorch the surface and now the outside

16:50

shape

16:51

well we’ve got to cut the outside shape

16:52

that’s only one of them how do we

16:57

collect the outside shapes well go back

16:59

to a trick collect everything

17:03

hold down the shift key and then click

17:06

on the blue layer and it’s gone so now

17:09

we’ve just got the outside shapes in a

17:11

couple of clicks and we can make those

17:13

into a group we click on the black group

17:17

up here

17:18

double-click and we can set the cutting

17:21

parameters now for cutting these shapes

17:24

out speed i’m going to set that to

17:27

something like about 50 millimeters the

17:29

second normally I’d run that about a

17:31

hundred but i’m going to say 50

17:34

millimeters a second and

17:39

we probably only need twenty percent

17:42

power so we’ve got to do the scorching

17:45

before we do the cutting

17:47

but remember we’ve only got two groups

17:50

that we’ve defined on here so we don’t

17:53

need to do very much up and come up here

17:56

to our edit cut property and look

17:59

there’s our two groups get simple we

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

18:03

want that cut first and then we’ll

18:08

do that element there

18:12

so we know save that to you file as well

18:18

ok now you will remember when we were

18:22

here last time that i was commenting on

18:25

the fact that i thought these cuts were

18:28

very wide another was the beam was

18:31

cutting far too wide

18:32

well that’s probably because it is out

18:35

of focus and as I just shown you on the

18:39

picture of the beam if you move away

18:42

from the true central position then the

18:44

beam starts to get bigger and the energy

18:47

density starts dropping off so that

18:48

means your cut is not as good or as

18:50

efficient so what we’re going to do now

18:53

is to make a piece of tooling to check

18:56

that one of the great advantages all

19:00

having an autofocus system although not

19:04

necessarily the pen is that when we get

19:07

it working properly and at the moment

19:08

it’s not working properly because I

19:10

don’t understand how to use it but I

19:12

will find out

19:14

we ideally need to do a graving on the

19:17

surface but when we come to do the cut

19:20

this is five millimeter material the

19:23

ideal place for the focus point we’re

19:25

cutting this material is going to be two

19:28

and a half millimeters into the surface

19:29

to get the most effective cut we’re not

19:33

going to do that today we’re just gonna

19:35

stay with it with the focus on the

19:37

surface more or less i think the focus

19:39

is actually about one millimeter down

19:41

into the material but it’s a compromise

19:43

that I’m using today

19:46

just check that it fits on the material

19:48

which it does and supply on

19:52

extraction on this engraving and it

19:55

takes a long time to do engraving

19:58

because this scanning action that takes

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

20:00

place backwards and forwards

20:03

and that’s why quite often it’s actually

20:05

quicker if you can do outline text

20:09

and if you want something rather special

20:12

now your engraving word and you

20:14

specifically want shape if you just want

20:17

to mark something up for identification

20:19

then outline text to put this way to do

20:22

it

20:26

this doesn’t help

20:30

and now we’re moving from engraving to

20:31

cutting sinceros that white flashes that

20:35

tells me that we’ve got enough power and

20:37

the the cat was going right through the

20:39

material and the extra energy is

20:41

reflecting hot zone section

20:45

now forgot the fits on this job right

20:47

then we might not have to do it it

20:50

should possibly just pressed together

20:51

and we good enough to do the job without

20:54

gluing

20:56

now credit is a very notoriously bad

20:58

material precise you by five millimeter

21:02

acrylic and it might be 4.8 it might be

21:05

5.2 if its cast acrylic it could

21:09

probably plus or minus half a millimeter

21:12

so you can get huge variations in the

21:14

fitness material even on a little piece

21:16

of material like this you get probably

21:18

half a millimeter variation very very

21:21

difficult to get good quality fits when

21:23

you’re trying to turn and grow

21:29

let’s see what we got

21:37

all the parts popped out

21:42

ok now we’ve got a piece of card in and

21:45

remember we’re setting the focus

21:48

manually now so I’ve got to set the

21:50

focus back onto the surface with my

21:52

little gauge

21:54

so we need to reset the bring the table

21:57

up a little bit

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

22:02

yup i think it will probably say how

22:04

much security is to just set the focus

22:06

manually than it is to use the pen

22:09

pointer but

22:11

that’s just what I’m used to

22:30

you notice that wherever possible i’m

22:32

using radius corners

22:36

we’ll just strip the protective film of

22:39

our pieces

22:40

now this is the interesting one because

22:45

you can see the way in which the content

22:49

site is settled on the outside of the

22:52

film there it’s even settled on the

22:54

inside of the components when we take

22:58

that off

22:59

we left with the middle of the letters

23:01

in which we’ve got to take off as well

23:02

it leaves a lovely clean surface across

23:06

the back of the machine there we’ve got

23:08

some LED strip lighting it really comes

23:13

alive but that’s another project we’ve

23:16

got two tongues which point downwards

23:19

well these tongues here match with it so

23:22

we’re going to put that one on the tall

23:24

end and this short one on the short end

23:28

and they’re going to find the other side

23:31

of the ramp which is here we’re going to

23:33

drop it on like that and we drop it onto

23:35

the base now doesn’t matter which way

23:37

round on the basic goes because it’s

23:38

symmetrical and there we go is plugged

23:41

into the base and the whole thing is

23:43

actually clipped together very nicely

23:45

now this piece here sits in the middle

23:50

and pointed towards the beginning and

23:54

you can put it on that way but that

23:57

would be wrong

23:58

so what we’re going to do is put the

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

24:00

slots on here towards these knobs that

24:04

are on this end

24:05

so this is the top of the ramp and the

24:08

idea that is that this point here this

24:11

age just hear that is the center of the

24:14

ramp if we take when our paper templates

24:16

that we’ve made we will find that we can

24:19

pop this on here like this and slip it

24:26

into position now at that position there

24:30

you’ll see that it says zero in line

24:32

with the end of this bar that is the

24:35

zero position right in the center

24:37

representing perfect focus and perfect

24:41

focus occurs on this flat plane here so

24:45

we’ve got a large area here that we can

24:48

use to set the focus up now that’s a 4.7

24:51

millimeter space of their i’m going to

24:55

use that just as a nominal spaces to

24:57

start with make sure it’s flat in there

25:07

we’re going to raise the table until we

25:09

get the table to touch on that surface

25:12

they’re just one touches it’s just

25:16

grippy down their looks so they’re that

25:19

these four point seven millimeters above

25:22

that surface there we can take this out

25:25

now because we don’t need this anymore

25:26

temporary and our focus gauge will sit

25:31

on here now if you look carefully you’ll

25:33

see that there are slots underneath

25:35

these tons which actually caused this to

25:38

click down and stay nice and flat and

25:42

you know that that’s the case because

25:43

this will just drop down inside these

25:46

lugs at the end here so we need to drop

25:49

it over the lugs and clip it in and

25:53

these holes here these marks on the end

25:55

tell you which end is which because it

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

26:00

won’t fit

26:06

the other way it completely mr. lines if

26:09

you line up the other way so it only

26:10

goes on one way but there are actually

26:13

two ways that you can put it on you can

26:15

put it on like that and make sure that

26:18

the center’s to flip down or and this is

26:21

a much better way to do it we can put it

26:24

on this way and that is the way that I’d

26:29

recommend that you use it

26:31

numbers down here so it’s rather strange

26:34

one else that because i can’t see what’s

26:36

going on

26:37

wait and be amazed right so we’ve got

26:40

our focus set up with as eight now we

26:44

need to come down here and we’ll check

26:46

power so we set max power it’s set to

26:50

twenty percent i like that twenty

26:52

percent is good

26:53

it doesn’t matter what power you have it

26:55

set to provided it’s quite low

26:58

once you set the power what we’re going

27:01

to do is play with the speed so we’re

27:04

happy with the power at twenty percent

27:06

inter let’s set the speed now we’ve got

27:10

the speed currently set to 200

27:12

millimeters a second

27:15

maybe right maybe wrong let’s set it 250

27:19

and we’ll see what we get

27:21

i’m showing you what I’m doing what I’m

27:22

going to do here i’m going to hold the

27:24

post button on them and drive it

27:26

backwards and forwards I’m going to turn

27:27

the pulse on and i’m going to drive it

27:29

towards me 250 millimeters a second

27:33

so this is looking actually quite good

27:36

because as we look here look you can see

27:39

the line is thick there it gets very

27:43

thin just here and then it’s not getting

27:47

thicker again

27:48

now that’s the thickness of the beam

27:51

changing with death

27:55

now what we’re looking for is the

27:57

thinnest possible point that we can find

27:59

no it’s difficult to find it here let’s

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

28:02

just turn the paper over and see what

28:03

we’ve got

28:04

lift the end there take it off

28:10

and hey that we’ve got a line on the

28:12

other side

28:15

you know that line is actually quite

28:18

long at the moment it runs from about

28:20

three at that end to about two and a

28:25

quarter maybe to the end

28:30

now what we’re trying to do now is we’re

28:32

trying to get that line as small as

28:35

short as we can so that we can find out

28:38

roughly where the most damaging point is

28:41

at the moment it’s damaging this paper

28:43

and i’m using the word damage you’ll

28:45

notice and damaging this paper over

28:48

quite a long li

28:51

but there’s only one point a very short

28:54

area where maximum damage will occur so

28:57

let’s go and see if we can find that

28:59

maximum damage section

29:05

we’ll put that back on again

29:09

and we’re lining this up

29:12

and this time I’m going to change of

29:14

speed up to 200 millimeters the second

29:21

ok now results are becoming clear look

29:24

we’re just about damaging it with just

29:27

coming through you see this line here

29:28

was really crispy clean this one is just

29:31

about making it through and if we look

29:35

for the point where it starts at around

29:37

about plus a half a millimeter and it

29:40

finishes at em just about one and a half

29:44

millimetres so that means a focus point

29:48

is actually

29:53

sitting there at about half a millimetre

29:55

is half a millimetre high or half a

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

29:58

millimeter low well bear in mind that’s

30:02

the top of the ramp with the two dots on

30:04

it it means our focus point is actually

30:07

half a millimeter below center so it

30:11

means what I’ve got to do I’ve got to

30:13

lift the nozzle up by half a millimeter

30:16

to get it spot-on

30:20

ok now we’ve got this little platform

30:22

here which we trying to establish the

30:25

gap between the platform and the end of

30:27

the nozzle and what I’ve got here is a

30:30

little tool that I’ve made previously

30:32

which is basically a 1 millimeter step

30:35

page

30:38

and so i can see that it’s 1234 goes

30:43

under there easily when I got here it

30:48

appears a half millimeter thick steel

30:50

very thin piece of stainless steel ship

30:52

and i would say i can probably just

30:54

about get that four millimeters step 1 2

30:58

3 4 millimeters step under so my guess

31:01

is that the gap is back 4.4 4.5 let’s

31:05

give it one last test and see how we get

31:07

on how we fix the focus problem

31:19

at the moment the line looks as though

31:21

it started about two

31:25

and goes through to about two

31:30

so I would say that we’re just about

31:31

spot-on with the focus into just put

31:34

this very soft piece of plastic up

31:37

inside until we touch the lens now be

31:39

very careful we don’t damage the lens so

31:41

I’m just going to very gently go up

31:43

until it just touches the lens and then

31:47

i’m going to market with my fingernail

31:52

about clamping it just there and that is

31:54

the amount that it’s up inside 33.5 plus

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

32:00

i think we said 5.5 is the clearance

32:05

under here 5.5 48s forty nine

32:12

millimeters which is a strange dimension

32:15

because they don’t make lenses that

32:17

sighs it’s got to be 51 let’s take a

32:21

look at the lens that’s actually inside

32:23

here things that don’t make sense

32:25

worrying me I like to understand how

32:28

things work

32:28

I think we’ll have that lens over there

32:30

and have a look at it you need to be

32:31

very careful handling these lenses and i

32:33

would suggest you either use the latex

32:36

gloves that they provide well I tend to

32:39

use cotton gloves to handle lends itself

32:42

so we should be able to just undo this

32:46

with the special tool that’s provided i

32:51

just got a natural curiosity I like to

32:53

understand exactly how things are and

32:55

what they’re I don’t trust anything I

33:00

think you probably see that in the like

33:01

Kanye this some sort of crap on their

33:04

sorry debris know you are supplied with

33:09

the lens cleaning kit and all the

33:11

instructions but costs like most lakes

33:15

and I’m not reading the instructions

33:21

there are two stages of cleaning lenses

33:23

one is gentle and i just put some

33:31

isopropyl isopropyl alcohol into there

33:35

and I use a cotton bud just like the

33:40

cotton but in that very gently and

33:46

didn’t take much to come off right

33:52

blonde the lens and it’s you can say

33:54

that it’s come off nice and clear on the

33:58

other side of the lens i can see there

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

34:01

is a haze can you see the haze on there

34:04

as well so if we get that off right okay

34:14

well the haze is gone now and then

34:17

within the pack that thing later provide

34:21

there are these things called lens

34:22

cleaning tissues now advise you to

34:25

handle this lens quite carefully because

34:27

the material that it’s made from is a

34:29

material called zinc selenide and it’s

34:32

very toxic you’re not you’re not

34:34

protecting your hands necessarily to

34:37

stop the damaging the lens i think

34:39

you’re protecting hands more to stop you

34:41

absorbing any of the tox it is toxicity

34:43

of that through your skin and the

34:46

chances are that there is not much there

34:49

to be exposed to zinc selenide is a

34:51

material is not very good at

34:54

transmitting the infrared light it

34:58

actually is only about seventy percent

34:59

efficient and the reason it’s only about

35:02

seventy percent efficient is because the

35:04

crystal structure of the material

35:06

reflects thirty percent of the light so

35:09

these lenses are covered in a special

35:12

anti-reflection coating which you

35:14

basically mustn’t damage because if you

35:16

take the anti-reflective coating off you

35:19

reduce the lens to a 70-percent quality

35:21

lens which is useless this particular

35:24

lens got a convex side on the top is

35:26

raised on the top and then it’s very

35:28

slightly dished underneath that gives

35:32

you slightly better

35:34

concentration of the focus point there’s

35:37

less what they call aberration which

35:40

means you get a cleaner focus pointed

35:41

slightly better than the simple plano

35:44

convex lens but it doesn’t matter when

35:48

you put it back in

35:49

you must make sure that the flatter side

35:53

or the con cave side is actually facing

35:56

the work so bear in mind that’s the way

35:59

that the lens tube sits you’ve got to

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

36:02

finish up with the curved side upwards

36:05

so we’re very carefully pop that on to

36:09

back onto its own ring seating like that

36:12

and then I suggest that you don’t try

36:18

and drop this in that way but what you

36:21

do is actually put it in this way put

36:25

the lens in and keep it upside down and

36:28

scroll the tube onto the lens that way

36:39

the lens will stay flat on its eating so

36:43

when it comes to it you’ll feel the

36:44

o-ring just beginning to buy don’t

36:46

over-tighten just just put the smallest

36:49

amount of tension on it to just feel the

36:51

o-ring is compressing now when you look

36:54

through it you should be able to see

36:56

through the lens like that

36:58

previously I couldn’t it with all cloudy

37:00

and that’s the sort of thing that i

37:01

would recommend you do probably take a

37:03

look at that lens once a week and if you

37:07

can’t see through it taken out and clean

37:09

it and keep stressing to you

37:11

the lens is actually the most important

37:13

link to make this machine work without

37:16

the lens you’ve just gotten laser which

37:19

does very little

37:20

it’s the concentration of energy from

37:23

that lens which is the thing that allows

37:25

you to do all the work that we do on

37:27

this machine I mean to replace that is

37:29

probably about 30 or 40 pounds maybe

37:31

even more than that

37:32

so you know you don’t want to get

37:35

through too many of those they have got

37:36

a lifetime and you will eventually have

37:39

to replace it but i suspect to it if you

37:41

treat it well it’ll last you one or two

37:43

years the other aspect of treating that

37:46

lens where

37:47

well is to make sure they always have

37:49

the air assist on don’t let debris and

37:52

smoke come up and filmed this top

37:54

surface this surface of the lens you’ll

37:56

see that we’ve got a hole in there a

37:59

mirror and then a tube that goes right

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

38:02

the way down

38:02

well this is sitting on the end of that

38:04

tube so equally well you can get debris

38:08

dust stuff in this end which will sit on

38:12

top your lens so there are two ways that

38:14

your legs can get dirty and hopefully

38:16

you should find that these two shoulders

38:19

sit against each other they should not

38:21

be a gap haven’t got an air supply on so

38:26

i put the air on

38:27

that’s important

38:32

and we go

38:36

we should be able to see the light on

38:37

here now and it starts at 1.5 it goes

38:41

through there and finishes up at just

38:46

about 1.5 so i think we’re probably

38:49

pretty well spot on with our focus now

38:53

well okay now fitted to

38:57

two-and-a-half-inch lens which they

38:59

supplied on internal measurement which

39:01

says 56 millimeters

39:03

I’ve got fifty six millimeters

39:05

internally and 63.5 is the actual

39:10

direction so that’s about seven and a

39:12

half millimeters and that’s 7.8 so

39:16

that’s a reasonable match for the

39:18

theoretical focal distance so i’m going

39:21

to put it under there and that worked

39:25

absolutely perfectly you can hear i just

39:27

cut off the air supply think back to the

39:31

logic of what i said earlier we’ve got a

39:34

longer lens it’s not God’s it’s got the

39:38

same amount of power going through the

39:40

lens but it’ll have probably half as

39:43

much penetration so i was using this at

39:46

225 millimeters a second to test the

39:51

2-inch lens i suspect i’m going to have

39:53

to drop this down to maybe a hundred and

39:55

fifty eventually but we do we’ll run it

39:58

to 25 to start with just approved the

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

40:00

point of loss of power

40:04

there we go so yes I expected it hasn’t

40:08

made it through so we’re gonna have to

40:10

drop the speed and I’m gonna drop the

40:11

speed to about a hundred and fifty so we

40:15

could run a bit faster because that’s

40:17

running far too long

40:19

I mean that’s running from

40:21

three-and-a-half nearly 4 to about two

40:26

and a half so that means our center

40:30

point is approximately 1 millimeter too

40:34

high

40:35

half a millimeter one millimeter too

40:38

high

40:41

so the way to imagine that is I got to

40:43

raise that focus point up to match that

40:47

one so I’ve got to raise the table up

40:51

those got to decrease the gap to get it

40:54

to come back down the slope so I’ve got

40:57

to come up about a millimeter so instead

41:00

of that gap which is a millimeter gap i

41:04

need to go down to something like a

41:05

seven millimeter gap there we go that’s

41:08

perfect

41:08

so that’s a seven millimeter gap now

41:11

Barry mind this has got a much longer

41:16

but depth of field so it’s always going

41:19

to have a much longer line i’m not going

41:22

to get as much as much contrast around

41:25

the middle but having said that we take

41:28

a look there it runs from about 2 to 1

41:38

so to get that to work

41:42

I’ve got to drop this down half a mil to

41:45

get them onto its ideal position so i

41:47

need to add half a mil to the gap so to

41:52

get a seven and a half mil gap i’ll put

41:55

my half-mile spacer in there and then we

41:58

go back to our seven mil step which is

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

42:00

that one and I’ve just set that now to

42:03

just a snug fit under there

42:06

go down just a shade

42:09

and an 80 millimeters the second

42:12

seven-and-a-half cap

42:16

it means to get to get that point to

42:22

here I’ve got to raise the table up

42:26

which is decreased the gap so instead of

42:29

seven and a half mil it probably is

42:31

going to be seven and a quarter

42:32

millimeters

42:35

I don’t you’re going to worry too much

42:36

about that that’s more or less where we

42:38

expect it so I’m gonna stay with seven

42:41

and a half then thought that’s not 56

42:43

inches that 56 inside 56 millimeters

42:47

inside plus 7.5 millimeters outside

42:51

gives me a total of sixty 3.5 which is

42:54

exactly 2.5 inches so that one is

42:58

absolutely spot-on

43:00

now I’ve got something else that I want

43:02

to try now they told me that I couldn’t

43:06

get a one-half inch lady I’ve modified

43:09

the inside of this nozzle it didn’t have

43:12

a very big shoulder in it inside so what

43:15

I’ve done up machined it out and i’ll

43:17

put a little teeny-weeny press the TV

43:19

when you ring in there and that ring is

43:21

enough to support a an 18 millimeter

43:25

diameter lens this was the 4-inch focal

43:28

length lens hold up which had a lens in

43:31

this back-end here my lens has got to go

43:34

flat side down inside there like that

43:40

and then on top of the lens I’ve got a

43:43

little compression ring spacer and that

43:49

spacer sits against the o-ring to give

43:52

me just the compression that I need when

43:55

I close the whole system down so

43:58

hopefully i should be able to win their

43:59

on and as I wander on at this point here

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

44:02

I should just begin to feel the o-ring

44:06

biting the lens is not rattling so

44:11

hopefully I’ve got a one-and-a-half inch

44:13

lens system now whether or not it’s

44:16

going to work and what the dimensions

44:17

are but I think about got it about right

44:20

it should come out approximately six or

44:25

seven millimeter gap this lens is going

44:27

to be very scalpel like it should give

44:30

me quite a long cut or a deep cut and

44:35

I’m i will have to increase the speed

44:36

quite a lot

44:37

let’s increase the speed to 225 maybe

44:43

you got to 258

44:47

ok

44:51

my calculations in dimensions came out

44:53

reasonably well because at the moment is

44:56

it running to about one millimeter and

45:04

about half a millimeter so I’m going to

45:08

come up about a quarter of a millimeter

45:10

to get it right so that’s still about

45:14

seven millimeters

45:17

I think seven millimeters is close

45:19

enough

45:21

ok so I’m going to do the ultimate test

45:23

of my one-half inch lens now that i’ve

45:25

just created this is something I’ve done

45:27

quite a few times this year on my

45:30

existing machine now what I’ve got here

45:33

is my pin table and a block of metal

45:36

with a couple magnets on it that will

45:39

actually clamp this is sufficiently

45:43

stable and it’s not going to move and

45:45

I’ve got this set the same height as the

45:47

pins so drop the paper onto the pins

45:55

and just drop the magnets on there to

45:58

stop the paper moving

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

46:42

now this is coming out the opposite way

46:43

around 21 normally used to with my

46:46

machine because this is not been written

46:48

for this machine been written for the

46:50

opposite hand

47:04

ok so what we do know is what that lens

47:07

over 2a to insurance and we’ll see what

47:10

happens with the two

47:25

there’s no effective than i thought but

47:27

the detail some of the detail is a

47:30

little bit fuzzy

47:32

some of the very detailed parts together

47:34

overlap and fold

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

48:12

two-and-a-half

48:16

37.5

48:22

now the interesting thing here is on

48:24

right up and about seventeen percent and

48:27

you can hear that hissing noise that the

48:29

cat is making that’s still too high

48:31

frequency impact engraving zone

48:42

well it has made it all the way around

48:45

we need to go and have a close look at

48:46

that to see the differences between the

48:48

lenses but i think that categorically

48:51

proves that we got the three lenses now

48:53

correctly set on focus because you

48:56

wouldn’t be able to do that and that’s

48:58

the focus was correctly set so we’ll

49:01

just take a look at the results under a

49:03

microscope have experienced while

49:05

looking at the quality but we need to do

49:08

some comparison so that you can make

49:10

your own judgment as to which lends you

49:12

would use for doing a job like this at

49:15

the moment you don’t have the choice of

49:16

a one hopping trains because they don’t

49:18

make it I’ve had to make my own but i’m

49:21

sure that in the near future i think

49:23

this will provide free providing with a

49:25

one hopping trains if you need it

49:28

so now we can reflect on the performance

49:31

of these three lenses now for comparison

49:34

what I’ve done I’ve shown you what I

49:37

would normally expect from my ebay

49:39

machine

49:40

the first thing I thought you to look at

49:42

is up at the top right hand corner

49:43

you’ll see that i put an arrow pointing

49:46

towards the line thickness that each of

49:49

the lenses produces is it as a

49:52

comparison

49:53

we’ve got a pencil for one-and-a-half

49:55

inch lens we’ve got a felt tip pen for a

49:58

2-inch focal length lens and we’ve got a

Transcript For Cleaning a Laser Lens & Care of Your Lenses (Cont…)

50:01

markup end for a two-and-a-half-inch

50:03

focal length lens so the lines get

50:06

thicker as the lens gets longer which is

50:09

what we said because the spot size at

50:11

the waist of the lens is bigger for each

50:14

of these when we start doing thicker

50:17

materials woods acrylics then different

50:20

depths of failed and different power

50:23

densities have a big effect and we

50:25

should be tackling those in a completely

50:26

different session

50:28

for graphics work when you’re working on

50:31

a surface or within material such as

50:33

paper you will need the shortest

50:36

possible focus focal length that you can

50:38

get because that gives you the Christmas

50:40

in the best definition

50:42

well thank you very much for your time

50:45

today we’ve covered a great deal on

50:48

lenses and hopefully this will give you

50:50

a better understanding of one of the

50:52

most important features of your machine

50:54

that lens is critical to the performance

50:57

of the Machine and the work that you

51:00

create with it so choose the right lens

51:02

and McCarthy lenses carefully thanks for

51:06

now and I should be seeing you next time

Transcript For Cleaning a Laser Lens & Care of Your Lenses

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Last updated August 26, 2021

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