18 – RF And Glass Tube Laser Cutting Comparison

The Tangerine Tiger Series with Russ Sadler

In this Series, Russ has purchased a new 500 x 300mm, 50W laser machine from eBay with a view to modifying and upgrading it. In fact, he rips out the glass laser tube and high voltage power supply and replaces them with an RF laser source and PSU from Cloudray. Find out how the expensive RF laser source compares to a glass CO2 laser tube and prepare to get your hands dirty! So lets investigate this RF And Glass Tube Laser Cutting Comparison.

RF and Glass Tube Cutting Comparison - Laser Cutting Acrylic
RF and Glass Tube Cutting Comparison – Laser Cutting Acrylic

If you are considering purchasing a CO2 laser machine with an RF laser source from one of the big boy suppliers, I would suggest you check out this series before making a decision!


Thinking that my RF laser was just 20 watts (with a bit of extra power for warranty purposes) I was surprised by the initial cutting tests on 3mm Baltic birch plywood. Perhaps there was something “magical” about the cutting power of an RF tube after all!!!!. Were the “big companies” marketing claims correct after all? The truth was required. In this session I set about comparing an RF tube and a glass tube running at exactly the same watts and with the exact same test conditions. Let’s see if I am confirming facts or shooting down myths.

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0:00welcome to another session with my

0:02little tangerine tiger here

0:04um hey look i’m matching

0:07we’re clashing um

0:10it’s a bit cooler now the autumn is here

0:13and um

0:15we haven’t quite reached steam point in

0:19here but it’s pretty cool in this

0:20unheated workshop

0:21now when i woke up this morning i had

0:24planned to

0:26make this session all about grayscale

0:30and maybe grayscale photo engraving

0:33and grayscale 3d engraving

0:36but something has been puzzling me

0:41and that is the apparent power

0:45that we’ve got from 20 watts in this

0:47machine to cut materials

0:49more efficiently than i thought was


0:53so i want to try and investigate that

0:56surprise condition

0:58by doing some comparisons of cutting


1:01this machine and my 70 watt

1:04glass tube machine now i’m sure that’s

1:07something that will interest not only me

1:09but many other people as well

1:11because the people have gas machines

1:13don’t normally have rf machines

1:15and the people that rf machines are


1:18about glass tube machines so they’re not

1:21going to do the comparison

1:22so there’s only one person around it’s

1:24likely to do that comparison and that’s

1:26probably me

1:27so let’s get on and see what we can find


1:31i’m puzzled at the moment now we’re

1:34going to start off here

1:36on the light blade machine although this

1:38is a 70 watt two i’m only running it

1:40with a 60 watt power supply so it’s not

1:42going to be delivering

1:44full power i’m running at about 95

1:48and it’s still only delivering it’s only

1:50still only consuming about 20

1:52uh 20 milliamps which probably means

1:56it’s working closer to

1:5765 ish watts

Transcript for RF and Glass Tube Laser Cutting Comparison (Cont…)

2:01so the first thing we’ll do is take a

2:03look at

2:04what the power is that’s coming out of

2:05here now i’ve got a little bowl of water

2:07here to absorb

2:08the energy so we’re going to start off

2:09with the temperature of 15.3

2:48and we’re finishing up at 50.8

2:53so very simply 50.8

2:57minus what we started with which is 15.3

3:0015.3 equals

3:04times two equals

3:0771 watts doing better than i thought

3:10so i’ve got 71 watts

3:16at my lens so here we’ve just got a

3:18simple piece of masking tape which we’re

3:19going to put over

3:21that hole there i’ve got my

3:24pulse power set to 95

3:2771 watts exactly the same as what we’ve

3:30just tested

3:33so now what i’m going to try and do is

3:35to burn a hole

3:37in there and i’m going to hold the beam

3:39on for long enough

3:41to find out what size the beam actually

3:45is because when i

3:46press just a simple pulse

3:49whoops let’s move it to the right place

3:59that might be better okay

Transcript for RF and Glass Tube Laser Cutting Comparison (Cont…)

4:09you can see that it produces a very

4:13a very intense power immediately and

4:16caught fire at the tape but that’s not

4:17what i want

4:18i’m now going to gently press the pulse

4:20button and you’ll see what happens to

4:22the tape i’m just pressing it and

4:29i don’t want it to burn too far with

4:31those little scorch marks

4:37and they’re going to hold the beam on


4:40oh look what’s happening and longer

4:46and longer


5:10so i think that’s probably enough

5:13and that tells us what size the beam

5:15actually is

5:16i think we’ll probably call that

5:1913 and a half should we let’s be


5:22so we check the power of the beam we

5:25check the size of the beam

5:28let’s see if we can find out what the


5:31burn for the beam looks like see if i

5:34can get that lined up

5:35naught one two

5:39three four five

5:42six seven eight

5:45nine ten now just look at that isn’t

5:49that beautiful

5:51that’s just about the perfect mode bird

5:55a lovely conical shape like that with a

5:57very very sharp point

Transcript for RF and Glass Tube Laser Cutting Comparison (Cont…)

6:01now that’s what a real tube should look


6:05okay now it doesn’t show on the end here

6:07you can see

6:08some of the low power stuff but it’s got

6:11a very high energy core as you can see

6:14so there’s our starting temperature 14.8

6:31with that


6:38minus 14.8 14.8

6:42equals times two

6:47equals 35 watts


6:54i i really can’t believe that this is a

6:5620 watt unit it looks as though it must

6:58be a 30 watt unit

7:02so anyway so we’ve got 35 watts


7:27i’m now going to hold it on longer


7:40and that’s about as much as i think i

7:41can get so don’t take the worst case

7:43shall we which is across there

7:49that’s about 10 millimeters so there’s

7:52our comparison

7:55so we’ll give this one a 10 second mode

7:56burn as well

8:00one two three

Transcript for RF and Glass Tube Laser Cutting Comparison (Cont…)

8:03four five six

8:06seven eight nine

8:10ten weird lump there at about seven


8:14and it’s not loud definitely not the

8:16best beam i’ve ever seen

8:17there’s our comparison should i set the

8:21other tube to 35 watts as well

8:24okay well i’ve just done some quick

8:25tests on this machine

8:27and what i found was if i set this to 38

8:29this machine

8:30i get 34.6 watts so that’s

8:34pretty close to 35 watts that we’re

8:35getting off the other machine

8:37so the first thing we really ought to do

8:39having done the wattage test

8:42is to see how that’s affected the beam

8:45diamond well it’s a lovely round theme


8:53just wait for the little glows to stop

8:59and i’ll hold it on


9:10off and it doesn’t want to grow anymore

9:14so that is lovely isn’t it so that’s

9:16about seven millimeters diamond

9:19not one two

9:22three four five

9:26six seven eight

9:29nine ten but i think you can probably

9:32see it’s a lot cleaner

9:33this is a reasonably good test of power

9:37because the penetration goes into

9:39approximately the same depth

9:40okay so we’ve got our basic standards

9:42set up now look for comparison

9:45we’re going to use this two and a half


9:49plano convex lens now i like plano

9:52convex lenses because

9:54they have a weakness and that is right

9:56down the center

9:58as you go through the axis of the lens

Transcript for RF and Glass Tube Laser Cutting Comparison (Cont…)

10:01it’s terribly out of focus which i think

10:04is excellent for cutting

10:06and that’s what we’re going to try and

10:07do with this machine now we’re going to

10:08do one or two cutting tests

10:09at 35 watts so this lens

10:13cuts well at five millimeters so here

10:16we’ve got a piece of five millimeter

10:18extruded acrylic so i’ve got this set

10:22to eight millimeters a second and 38

10:25percent power

10:26so all these tests will be done at 38

10:28power exactly the same as the other

10:30machine the good news is

10:32the smoke is coming out the bottom we

10:34now do nine millimeters a second

10:39and the smoke is coming out underneath

10:40the game as you can see

10:46so let’s try 10 millimeters a second

10:48smoke still coming out underneath

10:52and that is just going to pop out


10:57just a little hang up but nothing


11:00it’s probably just a corner not quite

11:02making it

11:04so let’s try 11 millimeters

11:08i don’t think i should be able to press

11:09that out no we have to regard that as a


11:12so here we are our samples eight nine

11:14and ten millimeters a second

11:16so we’ll take exactly the same lens

11:20and lens tube and we’ll transfer that

11:22onto the other machine

11:23along with this material so the whole


11:28is exactly the same going on to the

11:30other machine

11:35let that drop onto the five millimeter

11:36step there

11:44i’m gonna start this one off at seven

11:45millimeters a second

11:47but technically it should do it because

11:50the beams look the same

11:51the power is the same i’m now going to

11:54run this at 100 power

11:57it doesn’t matter what the frequency is

11:59because i’ve got no

12:00time base involved it’s just running

Transcript for RF and Glass Tube Laser Cutting Comparison (Cont…)


12:04well we’ve got smoke coming out the


12:09and it’s fallen out as you can see eight

12:13yeah and to cut

12:16nine millimeters a second

12:21still working oh

12:26and just about managed to

12:30push that one out nine millimeters a


12:35right on the edge of being okay it’s

12:38pretty poor at the bottom of the cut

12:40we’ll carry on

12:42we’ll try 10 okay it appears to be

12:45blowing out the bottom


12:52no no wait i can’t push that

12:57there we go

13:01there is no surprise

13:04this is the rf machine seven eight nine

13:07millimeters a second

13:09here’s the glass tube machine eight nine


13:13okay so it went a little bit better it’s

13:16a small difference

13:17the essence of it is there is no magic

13:20in this machine

13:21what is what’s you cut with what’s

13:26you don’t cut with hype or marketing


13:31you’ve seen it firsthand now

13:34comparison like with like so why would

13:37you spend a lot of money on a machine

13:39that can’t do cutting any different or


13:41than the cheap chinese machine you’d

13:43probably better to

13:45buy two machines what keep one of them

13:47for cutting and the other one for


13:49if that’s what turns out to be i’ve used


13:52because acrylic is one of the most

13:54difficult materials to cut you would

13:56think that because

13:57acrylic turns to liquid

14:00at 160 degrees c and then evaporates

Transcript for RF and Glass Tube Laser Cutting Comparison (Cont…)

14:06into what you would imagine as a cut but

14:08it’s actually evaporation

14:10at 200 degrees c so there’s very little

14:12difference in that temperature

14:14and they’re both very low temperatures


14:17the material doesn’t really want to

14:20accept co2 energy and so consequently

14:24it is quite difficult to heat up that’s

14:27why i’ve chosen this is a great material

14:28for testing

14:29but it’s also a difficult material to

14:32cut the claim

14:33i’ve heard that the rf does a superb job

14:38of cutting acrylic so we’ll compare the

14:40eight millimeter rf

14:42with the eight millimeter glass tube

14:44would you like to guess

14:45which one is which

14:51they’re both sitting under there

14:52together so you can do a direct


14:54what i will tell you is this strange

14:56striation here

14:58is something that happens just as you’re


15:01out of depth of cut this one is cutting

15:04through comfortably

15:06and you get this banding of striations

15:08which i’ve noticed before

15:10this is the rf2 you look at them in


15:14there isn’t a lot to choose between them

15:17neither of them are what i call flame

15:19polished okay now

15:21flame polishing an edge is not something

15:24that’s unique

15:26to any particular type of laser cutting


15:29flame polishing the smooth edge

15:32is all to do with the physics and the


15:36the chemistry of this material as i said

15:39at 160

15:41it turns to liquid at 200 it vaporizes

15:45we could run this remember at 10

15:46millimeters a second on this machine

15:48we’re going to run it at five

15:50millimeters a second to start with so i

15:51expect this piece to drop out

15:53because it’s cutting very slowly


15:57the great advantage of acrylic you can

15:58actually see what’s happening inside the


Transcript for RF and Glass Tube Laser Cutting Comparison (Cont…)

16:01but on this thinner material as i said

16:03we’re on a at five millimeters we’re on

16:05a balance point

16:07and i’m running here very very slowly at

16:10three millimeters a second as we run

16:13across the front of the cut here

16:15take a look just behind the cut

16:19no you can’t really see it

16:23basically two secrets which amount to

16:26the same thing

16:27when you understand what they are that


16:30going to give you flame polishing or

16:34a nice clean edge

16:39one of them is running very slowly

16:42and the other is very very minimal air

16:46assist i’ve just got enough

16:47whisper of air on there to protect the


16:51now this is eight millimeter material

16:54the thicker the material the easier it

16:57is to get a polished edge

16:59but you have to run pretty slowly so i’m

17:01running this

17:02at five millimeters a second


17:14okay now if we look carefully you’ll

17:18find that it is very

17:19sticky there you go

17:23it’s come out cleanly but it is very

17:27sticky why

17:32i hope you can see there how i catch it

17:35in the light just right

17:40you can see it’s virtually striation

17:42free it’s a lovely

17:44polished finish let me do exactly the

17:47same thing

17:48but this time

17:52we’ll put the air on

Transcript for RF and Glass Tube Laser Cutting Comparison (Cont…)

18:02there we go it looks pretty good but

18:04when you look at the right hand edge


18:07can you see how serrated it is that’s

18:10not the bottom edge as it was before

18:11that’s the top edge this time

18:14and that’s because of the airflow over

18:16the top edge


18:20and i’ll explain to you why that is it’s

18:23pretty easy to get this quality edge

18:25on a piece of extruded acrylic but it’s

18:27much more difficult to get the same


18:29on cast acrylic cast acrylic is very


18:33but the same principles apply you can do

18:35it but you have to run very slowly

18:38so as you’ve already seen there is no

18:40difference in the cut quality between

18:42these two

18:43processes one of them is

18:46continuous and the other one

18:50is also continuous to get maximum power

18:53out of the machine now regardless

18:56of whether you’ve got super smooth


18:59super smooth power it makes no

19:02difference at all to acrylic

19:04because it’s got a mind of its own there

19:06are two key properties

19:07of acrylic one of them is it turns


19:14at 160 degrees c

19:18it then vaporizes at

19:21200 degrees c

19:25so that’s what happens when you cut it

19:28you’re not physically

19:29destroying it what you’re doing you’re

19:32turning into

19:33steam effectively if it was water and

19:36water is a very good

19:37analogy of what this material is look

19:40we’ve got a block of ice here okay it’s

19:42a block of ice at room temperature and

19:44then it turns to steam

19:45or vapour at 200 degrees c doesn’t

19:48change its chemical composition

19:51because if you condense that vapor onto

19:53a cool surface

19:54you can turn it back into solid this

19:56does not go through a

19:57chemical change like a piece of paper if

Transcript for RF and Glass Tube Laser Cutting Comparison (Cont…)


20:01cut a piece of card paper or wood the


20:04do not turn back into wood because that

20:06is a chemical

20:07composition change this is just a change

20:10of state

20:11initially until it turns into flames as

20:14you’ve seen

20:15and then when it turns into flames you

20:17get a chemical composition change

20:19these two phases are very important so

20:21when we start a cut

20:23and let’s have a piece of material here

20:24that we’re going to cut

20:28the first thing that happens is as we

20:30burn in somewhere

20:33with a hole but the time it gets through

20:35to the other side

20:37not only have we got

20:40not only have we got a thin hole that

20:42goes right the way through

20:44around the outside of that hole

20:48we’ve got vapor

20:53okay now light when it hits the surface

20:58has no cutting effect on the vapor

21:00itself all it does is to heat the vapor


21:03further and sometimes turn it into


21:07because there’s a chemical composition

21:09change this little blue beam

21:11has to move forward

21:14until it passes through this

21:17vapor barrier that’s around the outside

21:20of the beam

21:21and only then can it start to cut again

21:24here and of course as soon as it starts

21:27to cut

21:29it produces a vapor barrier around


21:34and then it has to move on through that

21:36vapor barrier before it hits more

21:38solid material where it can start

21:40cutting again

21:41and so consequently what you’ll find is

21:43that you get these

21:47zones that are overlapping like this

21:51and hey what have we got here and here

21:55and here we’ve got striations

21:58they’re striations where the beam the

Transcript for RF and Glass Tube Laser Cutting Comparison (Cont…)


22:02cutting action of the beam is

22:04overlapping so that is

22:06why regardless of how you try and cut

22:08this stuff

22:09you will always get striations

22:12it’s a natural cutting property of


22:16okay so how come we managed to get

22:20a nice smooth edge on some of this


22:24the answer is this property here

22:28let’s take a look at the material from a

22:30side view now

22:31which is what we’ve just been looking at

22:33on the video

22:35as the beam cuts

22:38like this through the material

22:44what happens is we’re evaporating the

22:47material away

22:49but if we can keep enough heat

22:52in the material itself what you’ll find

22:55is that this

22:56zone here maybe two millimeters

23:00three millimeters behind the cut itself

23:03is liquid

23:07on the surface until it drops below

23:11160 degrees c and what happens to liquid

23:15when you put it into a cup

23:17when you put it into anything it levels


23:21so that is how you achieve a polished

23:24finish you try and retain the liquid


23:28of the acrylic long enough to allow it


23:33level out and hide these striations

23:37and that’s what it’ll do but to do that

23:41you need a lot of heat a lot of energy

23:44so generally the thicker the material

23:47the more the heat gets retained in the


23:50because you’re running slower when you

23:53run slower

23:54you allow more heat to if you like

23:57percolate and seep away around the edge

24:00of the cut

Transcript for RF and Glass Tube Laser Cutting Comparison (Cont…)

24:01so if you pick up a piece of acrylic

24:04that’s mirror polished

24:05you’ll find that it’s actually if you

24:07put it on your lips you could

24:08burn your lips it will it will feel very

24:11very hot

24:13a slow cut to build the heat up in the

24:15cut to keep this liquid phase

24:17on the wall of the kerf it becomes maybe

24:21slightly more obvious why i turned the

24:23air off

24:25if we get air passing through here air

24:28is cool

24:29and it will cool this liquid phase down

24:32much quicker and prevent it happening

24:33now we produced

24:34as you saw we produced two samples one

24:37with airflow

24:38and one without airflow i’m going to

24:41show you those under the microscope now

24:43now you can’t really see much of this

24:44one because this is the mirror polished


24:47this is the one that was done very

24:48slowly with no air when we looked at the

24:50previous pictures here

24:52the rf was on the left hand side here

24:55and the glass tube was on the right hand


24:58and the rf tube had all this debris

25:02i described it to you where the cut was

25:04just about to fail

25:06going through the bottom where you get

25:07this ragged bottom

25:09okay this is not the bottom this is the


25:13as you can see we’ve got a relatively

25:16smooth finish

25:18two thirds of the way through the cut

25:21but what we’ve got here

25:22is the effect of the air the air assist

25:26cooling that liquid phase right at the

25:30top of the cut

25:31and it’s turned into mush

25:35here’s the same thing without air assist

25:39we’ve got a nice clean mirror polish

25:42all the way down the cut i’m afraid you

25:46can’t believe

25:47the marketing hype which says you get a

25:49much better

25:50cut with an rf machine you don’t they’re

25:54the same thing

25:55once you start pulsing the cut you’re

25:58going to add striations into the cut

Transcript for RF and Glass Tube Laser Cutting Comparison (Cont…)

26:01and the only way you can get rid of

26:03those striations is to run

26:05slowly or with so much power that you’re

26:08heating the material around the edge of

26:09the kerf

26:10so you might be able to run faster if

26:12you’ve got an 80 watt machine but

26:14hey look i’ve got a 70 watt machine that

26:16i was doing these with

26:17i was running these at full power but i

26:19was still doing this eight millimeter


26:22at what five millimeters a second

26:25i mean i would normally cut eight

26:27millimeter at maybe 12

26:29or 14 millimeters a second so i’ve had

26:31to go

26:32at least half speed to get enough heat

26:35into the job

26:36to produce the mirror polished finish

26:39it’s a property of the material

26:41and the chemistry of the material and

26:43nothing to do

26:44with the machine that produces the cut

26:47i think that’s been quite an interesting

26:49session i think it shows you that

26:52again we’re not finding anything

26:56dramatic that would make me go out and

26:58want to buy one of these expensive


27:04at the moment it’s doing exactly the


27:07as a glass tube machine for cutting

27:10straightforward engraving

27:11i think we found that the switching

27:13speed the high speed switching

27:15is a definite positive advantage

27:19maybe but now that i understand how this

27:23machine works

27:25i’ve got half an idea about how i can


27:29the glass tube machines work faster as


27:33because we have got rf capability

27:37on those machines as well believe it or


27:41it’s well hidden away but hey that’s

27:44something that we do

27:46after we’ve looked at all the things

27:47that this machine potentially can do

27:49grayscale engraving

27:50well that’s something we will take a

27:52look at next time as i promised

27:56whether it would be gray scale photo


27:59i’m rather doubtful 3d engraving

Transcript for RF and Glass Tube Laser Cutting Comparison (Cont…)

28:02i’m much more positive about

28:04 [Music]

28:05 but it might take a long time because

28:07 we’ve only got 20 watts

28:09 i know that the glass tube can do some

28:11 pretty good 3d engraving

28:14 but then again i’ve got 70 watts to play

28:15 with i think i’m rapidly coming to the

28:17 conclusion that

28:19 i wouldn’t go out and spend my money on

28:20 an rf machine

28:22 it’s just not flexible enough for the

28:24 money you have to pay for it

28:27 the only thing that may persuade people

28:31 to go out and buy a machine like that

28:33 is the fact that they don’t have to

28:34 learn anything about the technology

28:37 all they have to learn is how to access

28:39 the menus

28:40 to get what they want because the

28:43 experience

28:44 and the knowledge has been built into

28:46 menus

28:47 you place your money and you takes your

28:50 pick

28:51 as somebody famous once said they were

28:54 so famous i can’t remember who they were

28:56 anyway on that lovely note i’m gonna

28:59 leave you now

29:00 and go and have a cup of coffee because

29:02 it’s pretty cold in here today

29:04 and i’ll catch up with you in the next

29:06 session bye for now

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Last updated April 25, 2024


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  • makeCNC who provide Downloadable Patterns, Software, Hardware and other content for Laser Cutters, CNC Routers, Plasma, WaterJets, CNC Milling Machines, and other Robotic Tools. They also provide Pattern Files in PDF format for Scroll Saw Users. They are known for their Friendly and Efficient Customer Service and have a comprehensive back catalogue as well as continually providing New Patterns and Content.
  • Cloudray Laser: a world-leading laser parts and solutions provider, has established a whole series of laser product lines, range from CO2 engraving & cutting machine parts, fiber cutting machine parts and laser marking machine parts.
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