19 – Laser Cutting Parameter Optimization – Fact or Fiction (40:21)

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 session, Russ explains all about Laser Cutting Parameter Optimization and the key variables that effect the cut performance. He also explains why cut parameters are not transferrable across machines.

Laser Cutting Parameters - Fact or Fiction
Laser Cutting Parameters – Fact or Fiction

Contents

  • Cutting parameters are subject to many variables.
  • The things that affect the cutting parameters:
    • Material
    • Thickness
    • Power available for cutting
    • Cutting speed
    • Focal distance of the lens
    • Position of focal point with respect to the material
    • Air assist
  • Limitations of ‘Cutting parameter Table of Laser Machine’ which (to date) is supplied with Thinklaser machines. Care with PVC!
  • Suggested better table is Thunderlaser cutting parameters available here. Russ uses the 60W one here. Take care with plastics.
  • Value of practical experience as opposed to relying on parameter tables.
  • Important notes to be added to your parameter chart.
  • Example of cutting card three different ways, first on a steel bed…
  • Importance of keeping the material flat.
  • ‘Noisy’ engraving/low power cutting and quieter cutting at a higher power.
  • Having to clean off the residue left on the steel bed with white vinegar (Dri-Pak product here).
  • Setting up the table to get the best airflow across the card and testing it.
  • Altering air assist rate to reduce flaming.
  • Checking the results – much cleaner so a note should be made of this in the parameter table.
  • Airflow considerations with the honeycomb bed.
  • Performing a test with the honeycomb bed – a messy result.
  • Using stand-offs with the honeycomb bed.

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 Cutting Parameter Optimization – Fact or Fiction

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00:15

Welcome to another Lightblade Learning Lab. Today we’re going to tackle a

00:20

subject which has come up just recently when Thinklaser reported back to me on

00:28

my early videos, asking me, why am I so vague on setting up the parameters for

00:36

cutting. Especially as they have provided me with a data sheet which gives me all the

00:41

cutting parameters for a 60-watt tube. In fact, for all sorts of tubes. Now cutting

00:48

parameters in my opinion is a very inexact science at this moment in time

00:54

because there are so many parameters that affect cutting and any cutting

01:01

parameter chart that you see, only contains the merest hint of all the

01:06

parameters that could vary and affect your cut. Now “Oi mate, can you tell me the way to China?” “oh, that way.”

01:12

I think that’s a fairly good example of what

01:19

cutting parameters are. They’re just a pointer in the right direction. Let me

01:23

just show you for example, some of the things that can affect it. The first and

01:27

obvious thing that’s going to affect your choice of cutting parameters is the

01:30

material itself and then you’ve got the material thickness and then we’ve got

01:36

this one here which I’ve called power available for cutting. We’ve touched on

01:41

some of this stuff before when we talked about mirrors, when we talked about

01:46

lenses. The power coming out of the laser may well be 60 watts, but it’s got to pass

01:52

through three mirrors which, lets conservatively say they lose three

01:58

percent each and then it’s got to pass through a lens which might be another

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

02:04

three percent. So that 7.2 watts that we’ve lost out of our 60 before we start. So we’re

02:10

down to 53 watts. So we may well have started off with 60 watts but we’re

02:16

going to finish up with 53 watts. Now that’s what I’m talking about power

02:21

available and you won’t see anybody talking about power available on any

02:27

cutting parameter charts. They will talk about what your tube delivers, supposedly.

02:34

Not how your machine is set up. So if your mirrors start to get a bit dirty or

02:39

your lens gets fogged up, this number here can drop considerably and it can

02:44

affect substantially the performance of your cut. Now the next thing that affects

02:49

the cut is obviously the cutting speed which you have got control over. When you

02:54

look at the Thunder laser website they do mention different types of lens but

02:58

only one of them is specified as a focal length. The other thing that

03:04

can affect the cutting is, and I’m talking specifically about cutting now

03:08

and not engraving, is the position of the focal point. Now you can have the focal

03:15

point set on the surface of the material or you can drop the focal point so that

03:19

it’s actually inside the material itself and that has a significant effect on the

03:24

cutting performance and the final thing depending on whether you’re cutting

03:29

acrylic or whether you’re cutting some organic material like leather or wood or

03:35

MDF. Air assist is a very important factor which nobody ever seems to

03:41

mention much about. When we see a chart which tells us that for a given material

03:46

and a given thickness all we need to do is use sixty percent power and a speed

03:52

of X that’s only half the story and that’s really what I’m talking about .

03:59

Now to establish cutting parameters for your machine. Only your machine will have

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

04:07

all this set of parameters. This is the most important thing on your machine,

04:12

which is the power that you’re delivering because that’s under your

04:16

control. I suppose theoretically any supplier of cutting parameters cannot

04:24

legislate for the quality of your machine.

04:28

So consequently they give you best conditions, but we don’t know the

04:34

condition of their machine when they set it up. Maybe their machine was similar,

04:39

maybe it wasn’t? We just don’t know, so the whole thing about cutting parameters

04:45

is uncertainty and so what I’m going to do is to show you how you can generate

04:52

your own cutting parameters and populate RDWorks with information that is

04:57

pertinent to you and your machine. Now ideally you would like to know what

05:07

power your machine is delivering. Not what power percentage. Percentage is one

05:16

of the worst things I can ever imagine for power but there is no other way of

05:21

defining power unless you have a power meter and you generally keep using the

05:27

power meter as I do to check the power of the machine but that’s because I’m

05:32

purely using this machine to understand and expand my knowledge about this

05:38

technology. The title of this section is cutting parameters fact or fiction. I’m

05:45

sorry I’m going to be a bit hesitant there is a small amount of fact in this

05:51

table if you can find it, but there’s a lot of fiction. Let me point out why i

05:56

don’t use these tables and i use my experience instead. We’ve got a whole

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

06:00

range of laser tubes here, the one that i’ve got is a 60 watt tube so let’s just

06:05

focus on the 60 watt. First of all up in the top right hand corner we can clearly

06:10

see that it says use 95% laser power. Well I think we’ve already established

06:17

that ninety-five percent laser power is a killer, it’s not going to do your tube

06:23

any good at all. On my machine at sixty-seven percent power I shall be

06:27

over driving the tube and seriously shortening its life. That immediately

06:31

brings into question the validity of all these figures because if they were done

06:37

at ninety-five percent power in the factory on a machine which on the

06:41

particular day produce those numbers that’s fine, that’s fact. But they’re not

06:48

fact for your machine or my machine. Cutting parameters are a hugely complex

06:54

subject which I tried to stay away from up to now and there is no way that I can

06:59

begin to tackle cutting parameters in one session. If I was using a machine all

07:04

day every day for production. I would, I would focus in on just a few cutting

07:10

parameters that suited me and my machine and my production. I don’t have that

07:16

luxury, I’m an inveterate fiddler I like to understand how things work and as

07:23

such when I look at these tables they are practically meaningless. I keep using

07:31

disparaging terms about these tables and now I think I really ought to justify

07:35

myself by pointing out some of the reasons why I’m being so disparaging.

07:41

Let’s just take this first section here acrylic, I understand acrylic quite well

07:45

because I’ve done a lot of acrylic work. First of all this table is being in the

07:53

process, hopefully by the time you get your machine, this table will have been

07:58

completely revised and a bit more sense put into it, because I’ve already pointed

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

08:03

out a lot of problems to Thinklaser. First of all when we look down the

08:08

thicknesses there three millimeters three millimeters hang on shouldn’t that

08:15

be five millimetres or six millimetres or maybe four millimetres but it’s

08:21

certainly not three millimetres. We’ve already pointed out the ninety-five

08:24

percent laser power problem ok let’s look across the top column and let’s

08:28

just focus in on my particular 60 watt tube. We’ve got two columns there, two

08:35

speeds to choose from we’ve got highest speed and a best speed now what does

08:41

that actually mean? As an absolute novice you would come into that and think well

08:47

I can cut that at 20 millimetres a second if I’ve got a 60 watt tube. I wonder

08:53

what the best speed is? Why would I go slower?

08:55

Is it something to do with the surface finish? With acrylic there are two speeds

09:01

that you can cut at, one of them is high speed and you could put high speed with

09:07

a lot of air or you can go slower and you can get a better surface finish with

09:12

using less air. Let’s have a quick look at the notes and sure enough when we

09:19

look over at the notes it says please pay attention to the airflow. OK it’s a little

09:25

bit of Chinglish there, but basically what it’s saying is that if you run with

09:30

low airflow you get a better finish. So there’s a sort of erm, sort of logic

09:38

when you understand how to cut acrylic but as a novice it wouldn’t make any

09:45

sense at all. The machine is supplied with three lenses, a two inch, a two and

09:50

a half and a four-inch lens. I’ve added to that collection with a one and a half

09:55

inch lens of my own manufacture. What do these figures apply to, because they

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

10:01

don’t apply equally to every lens? Because the density of the power of each

10:08

lens and its ability to cut changes. So there’s one major piece of information

10:15

missing from this table and that’s the lens that they used to produce this data.

10:20

When you’re cutting thicker materials the lens narrows the beam down to

10:26

something called a focus point if you are engraving you need the focus point

10:31

set to the surface. If you are cutting different thicknesses of material you

10:38

need the focal point set to different depths in the material to get the most

10:44

efficient cut. I’m still trying to find out what Kinef is or kinEF? Should that

10:52

be Knife? Just a bad spelling? As far as I can find out Kinef is a Russian

10:58

oil plant! Umm I’ve got no clue what that means. Now when it comes to MDF and HDF

11:08

with my 60 watt tube they tell me I can run at 15 or 12 millimeters a second. Now

11:15

from personal experience I would never want to run at slower than the fastest

11:22

speed that I could possibly get out of the machine. You put the power up to its

11:26

maximum, you put the air flow, as I mentioned at the end here up to its

11:31

maximum and you see just how fast you can run. The faster you can run for the

11:38

maximum power, the least amount of charring you get on the edge. So why

11:43

would you want to run at slow speed? It’s a puzzle to me? Now this relationship

11:51

between speed and airflow is a subject that we will tackle in a future session.

11:58

It’s a very important subject and it has significant effects when it comes to

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

12:03

cutting and now we come on to something which is very very controversial. They

12:11

tell me that I can cut PVC in this table and they give me the parameters for

12:16

doing it. Yes, I can cut PVC, but no I would never cut PVC and i would advise you to

12:23

never cut PVC, because in cutting PVC the chemical reaction caused by heating PVC,

12:32

releases chlorine gas and also hydrogen chloride gas. When it comes into contact

12:39

with moisture it will turn into hydrochloric acid I don’t think I want

12:44

to cover my eyes or my lungs with hydrochloric acid thank you very much

12:48

indeed! And by the way it will have no good effects on the slide ways and the

12:56

electronics in your machine. Well I think that’s enough critical comment about

13:02

that table and one of the reasons why I don’t use the table that was supplied

13:06

with the machine. I must reinforce the fact that I said at the beginning Thinklaser

13:13

are no different than any other company, any parameter table that’s

13:20

supplied lacks information and is only a guide.

13:23

The fact that this one possesses some dangerous suggestions had been pointed

13:31

out to Thinklaser and they are in the process of correcting that. So by the

13:34

time you get your machine and look at this table it will probably be

13:38

unrecognisable. To justify what I’m saying about all cutting parameter

13:47

tables, I’m going to take you to one of what I consider to be one of the

13:52

slightly better researched sets of data out there and that’s on a site called

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

14:00

Thunder Laser now they provide you with set of parameters for these different

14:08

wattage tubes they haven’t tried to put them all on to one table they’ve kept

14:13

them on separate tables. So we take a look at the parameter table for my

14:18

particular 60 watt laser. Now these tables are slightly better than the

14:24

other set of data that we looked at, because first of all they tell me that

14:29

this is a standard later head and so this data applies to a 2-inch lens and

14:36

again we’ve got just one speed, maximum power and it says powering corners. Well,

14:45

I think as far as the setup is concerned that’s max power and min power. We

14:54

haven’t tackled this subject of Max and min power for cutting this is yet

14:58

another complex subject which which will deal with in a future session, but at

15:02

least there’s an attempt here to show you that there are two possible powers

15:07

that you can use. So this table is slightly more informative. Again we’ve

15:12

got thicknesses and we’ve got just one speed now and we’ve only got one speed

15:17

for acrylic. There is a catch-all at the top here which covers them to a certain

15:21

extent which basically says suggested parameters for some materials. They’re

15:24

not saying these are absolute parameters, suggested parameters and it says

15:30

again the parameters might be different according to different machines.

15:34

Now the other thing that you notice about this table is they do mention foam

15:41

in here, which depends on what sort of material plastic you’re talking about, it

15:48

could be producing toxic chemicals. Research it very carefully before you do

15:54

it. I have pointed out in the hazards of materials, that you should be very

15:58

careful with plastics and when we get down here they do mention plastics. Oops

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

16:07

we don’t suggest you do them. So with a two inch lens they’re only giving you

16:13

information regarding 2.3 millimeter thickness and 2.7 millimeter thickness

16:19

and five millimeter thickness. So they’re not really giving you too much

16:23

information here, these are very much more of an outline guide. They also

16:31

mention cutting with a four inch focal length lens but they don’t mention

16:37

cutting with what they call their high resolution laser head. Now the high

16:44

resolution laser head, I think, but I’m not absolutely certain. I think that

16:50

basically is a one and a half inch lens. Well here we are back at the machine I

16:56

promise I’ve finished my rant about the dubious nature of the existing cutting

17:02

parameter charts that are available, not just from Thinklaser, but basically

17:06

wherever you go they all suffer with the same problem. Too little

17:11

information to be of any serious relevance to you, to repeatably set up

17:16

your machine. I suppose in a strange sort of way I’d feel a bit like my mum used

17:24

to, I alwaysremember my mum being able to just go to the cupboard take out all the

17:29

ingredients for a cake throw them into a bowl and a cake magically appeared and

17:34

it was perfect every time. Now I don’t look at a recipe book, I don’t look at

17:39

cutting parameters. Within two years i have gained a great deal of, I don’t know how to word it.

17:46

Perhaps the word, “feel” is the right word to use. I understand how various

17:51

lenses affect the cutting, I understand how airflow affects the cutting. I

17:57

understand how speed affects the cutting and power affects the cutting and I mix

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

18:03

all these ingredients together in my head when I’ve got a problem, and I come

18:08

up with nearly the right solution most of the time. Now, as a novice you don’t have

18:14

that skill or that ability and I don’t know whether it’s something that’s unique

18:18

to me or whether I’m getting plain bloody lazy because I don’t want

18:21

to go through all the work of filling in cutting parameters that I’m just

18:25

about to demonstrate to you. We’re running out of time in this session to

18:30

actually do any real cutting parameter test work, but I promise you in the

18:35

next session we will spend the whole of the session going through ways in which

18:39

you should or methods to approach setting up cutting parameters and

18:44

filling them int o charts. Now the cutting parameters that I should be telling you

18:49

about will be complete they would be just like a Jamie Oliver recipe. You will

18:54

be able to follow them and provided your machine is the same as it was today when

18:59

you left it yesterday they will work and if it doesn’t work it means that

19:04

there’s something wrong with your machine and that’s the great thing about

19:07

having exact cutting parameters it keeps an eye on the health of your machine. No

19:14

today we’re going to finish off this session by looking at some of the rather

19:19

key features that your ought to add to the notes when you’re doing your

19:23

parameters set up. Because there are very important things that you need to

19:29

understand but they’re things that nobody ever mentions in any parameter

19:34

charts that I’ve ever seen. It all comes down to experience, but experience should

19:39

be included in your cutting parameter chart. I’ve put my glasses on to look a bit

19:44

more studious and away we go. Now how many cutting parameter charts have you

19:49

ever seen where they mention anything about the extraction? How many parameter

19:55

charts have you ever seen where they tell you exactly what you should do with your

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

20:01

air assist? There are some vague references to it in the Thinklaser

20:05

charts, but they are vague references. As a novice you would not understand what

20:12

they mean, as an experienced person i can read into them what I think they mean.

20:18

Right, now what I’ve got here are some of this card that I used for my focus ramps

20:23

and so that I don’t waste my time and effort, I’m going to make some more focus

20:27

ramps. Now I’ve got three sheets here to make three focus ramps in three

20:32

different ways and I’m going to demonstrate some very critical things

20:36

about performance of this machine using that piece of cardboard. I’ve got a two

20:42

inch lens in there. I’ve got a piece of card here, if I was sitting on the

20:46

honeycomb bed with the airflow on there’s a possibility, only a possibility

20:51

that it will sit flat, but bear in mind what we’ve just done

20:56

with focus. It’s quite important that you try and make sure that any job that you

21:01

put on here is flat. Now as you can see this cardboard is not flat and I can

21:07

turn it over and the ends are sticking up in the air well to be honest it’s

21:14

much easier to put the sticky up ends downwards and pull the middle down. We can

21:20

either put little teeny weenie pieces of metal along the edge here so now we’ve

21:26

got a flat piece of material. Key issue number one. The first thing I’m going to

21:30

do is to raise up the table to almost its highest extent so that it’s more or

21:34

less level with the top here.

21:39

And there’s a good reason for doing that which I’ll explain to you shortly. So I’m

21:45

going to set that to five millimetres so what I shall do, I will drop that down

21:53

on to the five millimetre step and lock it up. To make sure that my air supply, and I’m

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

22:02

going to take this off of it so you can hear it.

22:07

It’s running completely flat out, it’s off and it’s fully on. So I’ve got full air

22:16

assist and the only reason I’m doing that is because you can’t really hear it

22:20

under there. I’m going to turn the extraction system on now.

22:28

So we’ve got plenty of airflow passing through here,

22:34

it’s not as good as it could be because we’ve blocked off a lot of the flow

22:40

because of this table here but what I want to do is demonstrate to you one or

22:47

two things. First of all we still got good airflow through here and we’ve got

22:51

our air assist on here.

22:56

I’ve just, I can hear something, I’m sorry I’m going to stop that.

23:03

I’ve got the power set to fifteen percent for that engraving and I’m going

23:09

to turn the air off.

23:15

Can you hear how noisy the cut is? Hear it?Now I’m gonna stop that. Because I’ve got the

23:32

power set to fifteen percent. Now a completely different subject which I

23:37

will have to tackle at some future point in time is high frequency impact

23:42

engraving. It’s a very strange characteristic and a very useful

23:46

characteristic that you get with a laser tube of good quality. You will hopefully

23:51

see how clean the engraving is, there’s not much smoke damage on there. It is,

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

24:00

even though I’ve got the air assist on, I’ve got basically quite clean engraving,

24:05

that’s because I’ve got this noisy type of Engraving. Now I’m going to change the

24:13

power from fifteen percent to sixteen percent. In fact I’ll go to seventeen

24:18

percent to be sure that I’m clear of this zone.

24:23

Okay, now for the for the moment i’m going to leave the air off so that we

24:28

can hear the difference between this, I’m calling it engraving but it’s not, it’s

24:34

cutting at very low power so that it doesn’t actually cut through. It’s not

24:39

proper engraving.

24:53

See how quiet it is? Lets turn some extraction on now.

25:14

Now you’ll notice I’m cutting this straight down onto a piece of steel and it

25:20

is giving a slightly hissy effect which is not the laser beam itself but it’s I

25:25

think a reflection off the steel underneath.

25:33

There is a bit of um misting on that surface there, these, these lines look as

25:40

though they’re a little bit brown on either side but that’s where the smoke

25:43

has actually blown back onto the surface of the lines and made them just like

25:50

shadowy. But that’s not the only problem that we’ve got with this

25:54

approach.

25:59

We have two problems; number one we’ve blown out a huge amount

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

26:04

of tar, in other words the cellulose when it’s cut produces this tar like residue,

26:11

because it’s a wood it’s a resin in there and it’s all sticky on the table now

26:19

that’s a major disadvantage in one way but hey if it wasn’t on the table it

26:25

would be in the filter. That’s what’s not on the back of the product, so this

26:30

really is not a very satisfactory approach for cutting things. As I said, the

26:34

only good thing about it is, that with a little drop of this

26:53

it’s on there not in the filter but it’s not until you see something like that

26:57

you realise just how much stuff is going out into the filter.

27:04

It’s even worse with MDF, ten times worse with MDF and you also get a similar

27:10

sort of residue but it’s a white sticky clear residue or a coloured

27:14

residue when you cut acrylic, Acrylic produces straight um methyl acrylate

27:22

solution, which is a horrible white sticky

27:26

material or if it’s a coloured acrylate it’s a, it’s a coloured material. But now I

27:32

want to try and solve two problems at once. If we take a look at these you’ll

27:38

notice that they’ve got a sort of a bit of a shadow dusky hue to them. With

27:45

your air assist you’re actually blowing the smoke back and painting that smoke

27:51

debris back onto the surface, so the last thing you really want to do is to have

27:58

your air assist on. First of all if we turn the air assist off, which I

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

28:03

have done now, the problem is that we’re likely to smoke the lens. So what we need

28:10

to do is to make sure that we’ve got lots of air flow passing across the job

28:15

so that we don’t stand any chance of doing just that. The way that we’re going

28:20

to achieve that is by dropping the table down a bit the first thing I’ve done to

28:25

stop the rubbish from collecting underneath here so we should finish up

28:30

with clean surface underneath and now what we want we want air flow passing

28:36

underneath a small amount but we want a lot of air flow across the surface

28:43

because the smoke comes up and we don’t want to blow it back down again we want

28:48

to push it away as quickly as possible and the way that we’re going to achieve

28:52

that is by going into the Z-mode and dropping the table down so that the

28:58

table sits approximately level with this surface here. There we go, that has dropped on nicely.

29:11

and now what I’m going to do I’m going to move this as close as I can to the

29:17

front edge of the machine. So here I am within an inch or so of the front of the

29:20

machine.

29:23

On this lid, I have attached some 1/2 inch thick rubber pads, so the door has got a

29:31

half-inch gap underneath it and that will allow a jet of air to fly

29:37

across the top of the job and I’ve made sure that that happens

29:43

because I’ve got this solid piece of metal in here which has blocked off the

29:47

air that would normally pass down through the table. So the only way for

29:53

the air to get through this machine is to get out the back here to those

29:57

grills at the back there and to do that it’ll fly straight across the top of

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

30:01

this job.

30:04

And there we go we shall have to look through the window this time.

30:09

Unusual for me to run the machine with the cover down but in this particular

30:13

instance is essential. So I’ve turned the air assist off, I’ve set the focus

30:19

correct and we’ve got plenty of air flow zipping through this gap underneath the door.

30:29

Now I think you can see the smoke being drawn away at quite high speed.

30:47

Now when we get to proper cutting there is a moderate chance that we may actually

30:51

see some flames on top of the work because the smoke that’s coming up, bear in

30:58

mind has got a lot of fumes in it. Now we are okay at the moment we’ve got no fire!

31:11

You can see how well we’re drawing the fumes away.

31:18

There we go, Flames.

31:26

We could just stop that.

31:33

And what we’ll do, we’ll turn on just the merest amount of air assist

31:37

and the way to

31:40

check that

31:42

is to take this off.

31:47

and listen for it.

31:53

there we go just the merest amount to blow air out of the nozzle.

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

32:17

I mean all this stuff, the original stuff there’s no smoking at all and then let’s

32:23

take a look at the back

32:26

completely clean at the back and what have we got on the table?

32:31

Absolutely nothing because the smoke that’s been drawn away.

32:38

So there’s something about to set up of the machine that you

32:44

really need to make make a note of if you’re doing cardboard for example.

32:49

Make sure you cover the bed and you get a linear air flow across your job. Turn

32:55

off the air assist. We will now reinstall the honeycomb bed. And

33:07

you can feel or hear

33:11

although this is, got air passing down through it, it’s still not enough to suck this

33:18

completely flat.

33:24

That’s because we’ve got so much air around the outside that we don’t have

33:30

enough differential pressure here to suck this down onto the table. If it was

33:34

thin paper there may just be enough there.

33:39

Now the problem with this is we’re going to be working on this top surface here,

33:48

and most of our air is going to come in and go down through here. So we’re not

33:54

going to be able to use this honeycomb bed without any air supply. So we’re on

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

34:00

a loser to start with if we try and do engraving or cutting on a surface like

34:06

this which will smoke up.

34:09

But I will demonstrate that to you anyway.

34:16

Now you would automatically think, remember, remember how we produced

34:21

horrible tar-ry shapes on the flat metal surface?

34:26

There’s absolutely no reason why we won’t produce the same touring shapes on here

34:32

because there is no airflow underneath this table.

34:38

You might immediately think there is because there’s honeycomb under there but hey

34:43

all the air is passing down the outside we’ve got no air passing down here at

34:49

all and so each one of these little cells is a dead cell we’ve got virtually

34:56

no air movement underneath this piece of metal underneath this piece of cardboard at

35:00

all and even when we cut through it there will still be very little air flow

35:04

because the only air flow that we’ve got will be passing down through the cut.

35:10

So there’s a pretty fair chance that if we

35:14

leave it like this, we will still finish up with some tar-ry marks on the back

35:20

but we’ll try it and we’ll see what happens.

35:32

It doesn’t do it as it comes towards us, it only does it as it moves away

35:35

from us you notice. Something to do with the airflow.

35:44

That’s because the cut, the smoke that is coming out the back of the cut, that’s

35:49

what it is.

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

36:07

It might look a bit mucky and it is mucky for several things; first of all

36:12

we’ve got these cuts that have nearly come through so we mustn’t take any notice

36:16

of those but what you can take a look at are all these marks along here look

36:21

every time it crosses over a piece of the honeycomb table we get a mark.

36:29

Especially where the table has already been marked up and it burns off the,

36:35

off the honeycomb back onto this surface. All this debris that’s on here is

36:43

actually burning off back onto the back of the card so that’s another good

36:49

reason why you’d want to stand your job off of here so you get plenty of air

36:53

flow past it as well. Right so I’ve done a couple of things now, first of all we

36:59

put some stand-offs on there

37:04

So we’ve got air underneath, we’ve got air across the top, we’ve got no air assist

37:10

on.

37:13

I’ve wound the….

37:16

I’ve wound the um lets call it the engraving speed up to 180 millimetres a second and I’ve put the

37:23

power up to 18 percent to try and get rid of this hissy cut.

37:29

37:33

There’s a hint of that cut coming back, can you hear it?

37:38

And that’s even at 18-percent. See when the smokes blowing away from the cut, now

37:45

what happened is that the smoke is coming out the back of the cut towards us and

37:48

having to draw all the way around the nozzle, can you see that?

37:56

Now the smoke is coming this way. Well in the overall scheme of things

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

38:03

that’s probably the best one so far. We can compare that with a sort of typical

38:08

example of something that has been done with air assist. You can see the difference here

38:16

with the air assist how we’ve blown the debris back onto the surface and here

38:22

we’ve allowed the debris to come up and be drawn away by the rapid air flow in the

38:27

machine itself. Now those are the sort of subtle changes and subtle things that

38:34

you need to make a note of when you’re setting up your parameters but nobody

38:38

will be telling about these in any parameter library that I’ve seen. So once you

38:42

get your job right, you will need to make sure that you note the type of table you

38:47

are using, whether you are using stand-offs, whether or not you’re using air assist or not, and

38:54

somebody’s going to say ooh, using no air assist means we could smoke the nozzle,

38:59

we could smoke the lens. Yes I agree there is a possibility of that ,so

39:03

what we’ll do…. let’s just have a look at the lens

39:08

I would say there’s zero damage to that lens. There’s no smoke getting up in

39:14

there and why well I think it could be something to do with the power that we

39:19

were using. The fact that we had a flame there and the flame means that we

39:24

were burning the smoke and it was not getting a chance to go back up

39:28

inside the nozzle or when it wasn’t burning it was being drawn off so

39:33

quickly that it never had a chance to get back up inside there. Well thanks very

39:36

much for persevering with me today it’s been a bit of a grumble session but I

39:41

hope in the end we found out some interesting stuff and this is a prelude

39:45

of the sort of way that we will be tackling in the next session. We shall

39:51

be doing things that you probably won’t see demonstrated elsewhere but hopefully

39:55

I should be able to give you some tips on how to quickly get to the best

39:59

cutting parameters for the job that you want to do. The procedure is the same for each,

Transcript For Laser Cutting Parameter Optimization – Fact or Fiction (Cont…)

40:06

it’s just that you’ve got to spend a lot of time doing it and I don’t always have

40:11

that much patience. Which is why I just pick them out of the air. Thank you very

40:17

much for your time and I’ll see you on the next session

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