06 – Know your Laser Tube and Hazards (17:11)

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 gives a detailed explanation of the laser tube and it’s associated hazards.

Laser Tube with Heating Lamps
Laser Tube with Heating Lamps

Contents

  • The laser tube itself
  • Russ’s thermostatically controlled anti-freezing system
  • The parts of the laser – water jacket, containment tube
  • Gas flows
  • High voltage system – anode and cathode
  • Gas reservoir
  • Gas mix
  • How the laser works
  • Mirrors – full and partially reflecting
  • Power limits – avoiding damaging your tube
  • Current limits

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 Laser Tube and Hazards

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00:10

Welcome to another Lightblade learning

00:16

. Today we’re going to give you a bit

00:19

of a look at the anatomy of this vital

00:23

part of the machine which is the laser

00:26

tube itself now it’s quite important that

00:29

you understand how this basically works

00:33

because you need to look after it, now you haven’t

00:36

got to do anything to it other than treat

00:39

it well but why do you have to treat it

00:42

well if you understand how the tube works

00:44

you will understand how you can abuse it

00:47

and that’s the last thing I want you to

00:49

do because if you abuse that tube it’s going

00:52

to cost you several hundred pounds to

00:53

replace it and it won’t be under

00:55

warranty

00:55

you might be interested in a couple of

00:57

lights that I’ve got stuck in here at

00:59

the moment

01:00

these are just what i call my

01:02

winterizing kit tacked down here i have

01:06

a small temperature controller or a

01:08

temperature-controlled relay which is

01:10

looking at the air temperature inside

01:12

the Machine this workshop that I mean is

01:15

totally unheated and during the winter

01:17

months

01:18

I’m fearful that the water that’s inside

01:21

this tube may freeze so I’ve taken

01:24

special precautions of adding a hundred

01:27

watts of heating into this machine and a

01:30

hundred watts of heating down there to

01:32

the chili unit as well so that during

01:35

the cold winter months as a completely

01:38

separate supply this machine will heat

01:41

up water in this tube and circulated

01:44

through the pumping so there is

01:45

absolutely no chance of anything will

01:47

ever fries okay now this tube is

01:49

actually made up of three glass tubes

01:52

the first actor tube which is what I’m

01:56

tapping at the moment is the container

01:58

for the guests

Transcript For Laser Tube and Hazards (Cont…)

02:00

that’s a gas reservoir now inside there

02:04

you’ll see there is another tube and if

02:06

you look carefully you can see along the

02:08

top of that tube some little air bubbles

02:10

well that’s the water jacket that sits

02:12

inside this altitude here and then if

02:17

you look a little bit closer you may

02:18

find through the reflections that there

02:21

is a third inner tube you can see

02:24

now the third inner tube is the

02:27

containment tube for the ionized gas

02:32

ok they don’t this end of the tube we’ve

02:35

got this red cable very thick red cable

02:38

which is capable of taking I think about

02:41

40,000 volts but it’s a 25,000 volts

02:44

cable this one and this cable goes to

02:48

that blue electrode there which is the

02:51

anode but when this too was working the

02:55

guests tends to flow towards this

02:58

positive electrode it returns and comes

03:02

back

03:03

can you see that pipe there that’s going

03:04

across the top you can see the spiral

03:07

tube here now that basically is spinning

03:09

the gas round and then it deposits it

03:13

just underneath this label here

03:15

the gas is spinning around at that point

03:17

in time and it travels back along the

03:20

reservoir to the other end of the tube

03:23

so there’s always a circulating flow of

03:25

gas through this tube

03:28

ok now I talked about a gas reservoir

03:30

this out to to being a gas reservoir

03:33

trace gases like hydrogen and then on

03:36

and one or two other mixes maybe in

03:39

there as well to help certain aspects of

03:42

the tube but these are the Prince of

03:44

gases you need to imagine operating

03:46

within this tube the nitrogen is

03:50

actually the most important guess he

03:53

might say what is a carbon dioxide laser

03:55

surely the carbon dioxide is the

03:56

important gasps well yes it is but let

Transcript For Laser Tube and Hazards (Cont…)

04:01

me explain that the nitrogen is

04:04

absolutely fundamental to the way in

04:06

which this tube operates now I’m not

04:09

going to turn the tube on at the moment

04:11

but when we turn the tube on you will

04:14

notice it there as I’ve shown you in the

04:16

first introduction you will notice that

04:18

is a pink glow along the tube now that

04:22

pink glow is actually ionized nitrogen

04:25

all of these gases are non-conductors

04:28

naturally even as it’s sitting there

04:30

this tube is being bombarded by cosmic

04:34

rays from the Sun I know it’s nighttime

04:37

but they pass through the earth they

04:39

pass through anything and everything and

04:40

there will be some cosmic rays which

04:43

will actually be colliding with some of

04:47

the nitrogen atoms that are in that tube

04:49

there might only be one or two or three

04:52

that’s enough to start a chain reaction

04:56

off at any point in time that we wish to

04:59

turn the laser on now to get current

05:02

flow you need basically some free

05:05

electrons or electrons that are knocked

05:07

out of their orbital shells

05:10

let’s not get too involved with the

05:11

atomic physics because i’m certainly not

05:13

a physicist

05:14

so what’s going to happen is to get this

05:17

to kicked off into action at the end of

05:19

the tube over there

05:21

we’re going to put 25,000 volts DC and

05:26

that means that they’re 25,000 volts

05:28

difference between that end of the tube

05:30

and this end of the tube here which is

05:33

the cathode now that means that any

05:38

negative electron which is floating

05:41

around in that tube and as I said there

05:44

will be some floating around in there

05:45

just because of the natural action of

05:47

cosmic rays those free electrons will

05:52

immediately start flying a very high

05:55

rate of knots along the tube towards

05:57

that electrode at the other end there

05:59

and in doing so it’s like a fat man at

Transcript For Laser Tube and Hazards (Cont…)

06:03

the back of the room rushing to the

06:04

front of the room to get these free

06:06

hamburger as he goes he’s going to knock

06:10

people out of the way he doesn’t care

06:12

and that’s exactly what happens to these

06:14

free electrons they’re going to rush

06:17

towards the end of the tube there and in

06:20

doing so they’re going to not some more

06:22

electrons off of other nitrogen atoms

06:25

and what that’s going to do is cause a

06:27

cascade action which sets the whole

06:30

thing in motion and we can start to get

06:32

this process called ionization now when

06:35

the gas starts to ionize which is

06:38

basically lightning the gas changes from

06:40

a nonconductor into a conductor and can

06:44

conduct huge amounts of current we can’t

06:47

afford to let that to happen because the

06:48

two but just pop so built-in

06:51

to the built into the system there’s a

06:53

control system in the power supply which

06:55

limits the current to a very small value

06:58

so we get very small controlled currents

07:00

running through this very conductive

07:02

gasps okay so we’ve got nitrogen which

07:06

is no a conductor but it’s more than a

07:09

conductor because it’s no an ionized gas

07:12

and you don’t get ionized gas for free

07:15

it requires energy and energy produces

07:18

heat no lightning sets fire to trees

07:21

what we’ve got is controlled lightning

07:24

effectively i’m exaggerating slightly

07:26

but we’ve got controlled lightning in

07:28

that tube there the ionized gas can get

07:31

up to thousands of degrees C to try and

07:34

control that temperature what we’ve got

07:36

is two things the first thing we’ve got

07:39

is helium and we have huge amounts of it

07:42

in that mixture helium is a very very

07:46

good conductor of heat so the helium

07:48

will carry the heat out to this water

07:51

jacket and we’ve got water flow that

07:53

passes through the system to take the

07:56

heat away so that’s where the water

Transcript For Laser Tube and Hazards (Cont…)

08:00

jacket comes into play so the helium is

08:03

very important the nitrogen is very

08:06

important and we haven’t mentioned the

08:08

co2 yet let’s just go back to the

08:10

nitrogen for a second because I said it

08:14

was the most important gas without the

08:17

nitrogen ionizing we don’t get anything

08:20

happening the nitrogen atoms are in fact

08:23

being that let’s imagine excited my hand

08:27

is moving to imply excitement our height

08:30

and when this is running at a controlled

08:33

current let’s just say for milliamps we

08:37

got controlled excitement but as we

08:41

increase the current in that tube the

08:45

excitement level of the nitrogen starts

08:48

going up and so can she go to get higher

08:51

and higher energy levels and vibration

08:53

levels within the nitrogen itself and we

08:55

can control the level of that excitement

08:57

with the current flow that we put

08:59

through the tube

09:00

I can he get your patient yes i know i

09:03

don’t hear about night

09:04

you don’t want to know where the carbon

09:05

dioxide comes in and I like to imagine

09:07

the carbon dioxide is a very lazy gas it

09:11

doesn’t really want to do much but

09:13

unfortunately the nitrogen doesn’t want

09:16

to work that way

09:17

it’s getting very very excited and as it

09:20

gets excited so from time to time some

09:23

of these nitrogen atoms will collide

09:25

with the carbon dioxide molecule and as

09:28

it hits the carbon dioxide molecule it

09:30

will impart some of its energy to the

09:32

carbon dioxide and so the carbon dioxide

09:35

will all of a sudden have to be raised

09:37

up to a slightly higher energy level

09:39

yeah it doesn’t want to be there it’s

09:41

naturally lazy and so consequently what

09:45

will happen is once it gets excited

09:48

it says don’t be here and it finds any

09:51

and every opportunity to get rid of its

09:54

extra energy and go back to sleep again

09:56

now it is that process of getting rid of

Transcript For Laser Tube and Hazards (Cont…)

10:00

the energy and it gets rid of the energy

10:02

in the form of light photons of light

10:05

that process of giving off its energy is

10:09

basically the emission of photons to

10:12

give off energy three other parts of

10:14

this word laser and it’s called light

10:17

amplification by stimulated emission of

10:20

radiation well the stimulated bit is the

10:23

nitrogen raising the level the emission

10:25

is when it drops back down again and it

10:27

gives off this radiation which is light

10:29

in the form of 10.6 micron radiation

10:33

we’ve got this bit at the frontier

10:35

called light amplification so how’s that

10:38

been working hiding behind this water

10:39

jacket here right on the end of the tube

10:42

we have a mirror it’s a mirror that is

10:47

perfectly aligned with another mirror

10:50

right at the other end

10:51

now this is a hundred percent reflecting

10:54

mirror not this end of the tube

10:57

we’ve got a brass water jacket but

11:00

behind that brass water jacket just here

11:03

is another mirror that this mirror is

11:08

not quite the same as the mirror the

11:10

other end this one is a partially

11:12

reflecting mirror

11:13

I don’t know exactly what degree of

11:16

partially it may will be 70 it may will

11:19

be eighty percent reflecting but that

11:21

means that twenty percent of the energy

11:23

that hits this will come out of here and

11:27

will be the laser beam that we are going

11:30

to use we talked about the fact that the

11:33

co2 gets raised to a higher energy level

11:36

and then wants to get back down to its

11:38

lazy level now it only needs one of the

11:42

co2 molecules to lose its energy and

11:46

emit a photon and that photon will start

11:49

traveling along this tube in a direction

11:51

and will automatically persuade another

11:54

photon to come enjoy it

11:56

ye it will trigger a chain reaction and

Transcript For Laser Tube and Hazards (Cont…)

12:00

that chain reaction will trigger more

12:01

and more photons to join in and travel

12:04

in this direction all those photons will

12:06

start rapping along the tube and as they

12:08

travel they will gather more and more

12:09

photons and all traveling in that

12:12

direction so they get to that mirror at

12:14

the end there and then they start all

12:17

coming back now there’s a lot more

12:18

coming back then went down so those

12:20

coming back by this time of course we

12:23

should have more and more collisions

12:24

with nitrogen atoms which has promoted

12:26

more and more co2 Adams up to high

12:29

levels so as they come back they will

12:31

trigger more and more photon release and

12:34

you will get a bulk of photons that will

12:37

gradually be amplified every time they

12:39

bounce back and forward off this mirror

12:40

so we get this amplification of light

12:44

going backwards and forwards in this

12:46

tube it’s nothing to do with the light

12:49

that you see coming out of the center

12:52

tube which is the pink light from the

12:54

ionized nitrogen is completely separate

12:56

from this other invisible light which is

12:59

bouncing backwards and forwards inside

13:01

this tube so there’s several strange

13:04

processes going on here if you remember

13:07

this conversation beginning I said to

13:09

you that the current is being controlled

13:12

by the power supply and you in fact are

13:15

controlling the power supply through the

13:17

percentage power that you input through

13:20

the keyboard now if you put to higher

13:23

percentage power you will

13:26

more character flow through that tube

13:28

what’s actually going to happen is the

13:31

nitrogen is no longer going to do that

13:35

it’s going to do this it’s going to go

13:39

absolutely bonkers the more current you

13:42

put through it the harder it vibrates

13:44

the more energy it has now you get to a

13:47

certain critical point and that is the

13:50

limit specified by the manufacturer of

13:53

that tube and their energy level in the

13:56

nitrogen is so high that it won’t just

13:59

encourage the carbon dioxide to go up

Transcript For Laser Tube and Hazards (Cont…)

14:02

and not be lazy and have a little bit of

14:04

extra energy it will have so much energy

14:07

that when it collides with the carbon

14:08

dioxide molecule it’ll break it down

14:11

into carbon monoxide and a free oxygen

14:15

etem no carbon monoxide is not a lacing

14:20

gas oxygen is not a lacing guess so

14:24

now because of your enthusiastic use of

14:28

hundred percent power ninety percent

14:30

power at the keyboard you’re actually

14:33

destroying the tube itself the gases

14:35

inside the tube by overdriving the

14:39

nitrogen and making it far too excited

14:42

so that actually has killer powers I

14:45

don’t exaggerate that too much because

14:47

built into the system there is probably

14:51

some hydrogen is probably in that

14:53

particular to a catalyst which is gold

14:55

which actually partially reunites these

14:59

two back together to make that so there

15:02

is a hailing process that’s built into

15:04

some of the better quality tubes and

15:07

that helps to promote a longer life tube

15:10

the principle of a tube dying over a

15:13

period of time is basically this one

15:15

because even when you’re running the

15:17

tube under manufacturers specified

15:20

control limits there is a very small

15:23

amount of this association as they call

15:25

it taking place both gold and the

15:28

additional gas which is generally hiker

15:29

water vapor has got a catalytic effect

15:32

of recombining these two back to carbon

15:35

dioxide but

15:37

drive it too hard for too long and you

15:40

will permanently destroy the carbon

15:42

dioxide and what will happen is the

15:44

oxygen will tend to collect on the

15:47

cathode in there and change the color of

15:50

cathode and so it will be obvious that

15:54

you’ve been a naughty boy and you have

15:57

destroyed your tube x over driving it so

15:59

I can’t say any more than that now you

Transcript For Laser Tube and Hazards (Cont…)

16:01

know how the Tool Works and why you can

16:05

overdrive the tube you can make the

16:07

mechanism work harder than it should do

16:10

there’s a balance point that you must go

16:12

beyond I have to know that this tube is

16:15

made by FR laser and it’s a 1200 CL so

16:20

we can go to the website and we can find

16:22

out what current specification they

16:24

recommend for this tube now my guess

16:27

it’s somewhere in the region of 20 to 25

16:29

milli amps one of the quickest ways of

16:32

finding out the relationship between

16:34

this 22 milliamps and the amount of

16:37

power that we’re allowed to use is to

16:40

probably just use the pulse button we

16:42

can set the maximum power here to some

16:44

value and i will show you how to do that

16:47

shortly and we can check whether or not

16:49

the power that’s on here equals

16:51

twenty-two milliamps so it may be that

16:53

will only be able to put sixty percent

16:55

power into here and we should get 22

16:59

million amps now what that means is

17:02

you’ve already reached the limit at

17:04

sixty percent power at no time can you

17:07

ever program into this machine more than

17:10

sixty percent power

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