What is wrong with this 150W?

[Patric Sandelin]

Hi everybody!

Can someone please enlighten a newbie what is wrong here. I seem to be getting the same power between 40 and 95%. Mirrors are aligned. Material is in focus. Settings have been checked by the manufacturer.

Cutting 12mm plywood:
357421357422


Did an engraving test and at 10-35 there are changes, 40-95 are the same. Unfortunately I didn't have anything to cut the board with so you can see it in profile.

357423

What seems to be the problem here?

[Bruce Volden]

Paul,

It would help us to know what type of machine you're using. On the rastered pic, what are the settings there. I'm saying more info would help.
The cutting part is quite puzzling 'tho..?

Bruce

[Patric Sandelin]

The machine is a Longtai 1390.

The settings on the rastered pic is 100mm/s on the first row, 500mm/s on the second row. Power number is on top of each "box".

[Keith Downing]

Did the laser previously work correctly, and now it doesn't? Or is it new?

Also, are you completely familiar with the software? It's not outside the realm of possibility that you've inadvertently used the same settings on all the blocks.

[Hannu Rinne]

Hi Patric,

To me it seems that you are using exterior plywood which is very hard to cut with a laser. Have you tried the same with any other material ?

Regards,
Hannu

[Wilbur Harris]

Your limits are set too low or the tube is going bad. Is there a mA meter on your laser? If there is, watch it to make sure the meter reading increases when you increase the power.

[Patric Sandelin]

Machine is brand new. All material is interior grade birch plywood (B/BB quality). The settings are not the same for all the blocks, it's been checked, rechecked and finally verified by the manufacturer via Teamviewer. Same min/max value.

I have done the test in 6mm acrylic also. 10-35 big changes, 40-95 barely any change.

[Keith Downing]

Your limits are set too low or the tube is going bad. Is there a mA meter on your laser? If there is, watch it to make sure the meter reading increases when you increase the power.

This was going to be my next question.

Assuming you have one, are you getting the same power output reading for all settings? If so, there is definitely a problem with the machine, tube or software. If not, it could be the material/focus/air etc.

[Patric Sandelin]

When the manufacture was logged in via Teamviewer, I saw a tube limit passing by on one of the screens and it was set to 99%.

Unfortunately I don't have a mA meter on the machine. If you measure it on the tube, I'm guessing it's very high voltage and not possible to use a regular amp meter?

Air assist is on.

[Keith Downing]

On my machine, the upper limit I have set to 95%, the lower limit I have set to 5%. Can you confirm your lower limit is not set to 99%?

And yes, if you are so inclined you can add an mA meter to your machine.

[Patric Sandelin]

Isn't the limits inside "Vendor settings", where you need a password? Quite sure that's where I saw the upper limit (when he logged in there remotely) or can you see it somewhere else?

But I'm quite sure it's correct. I've been testing how low you can go and the laser didn't fire under 8%.

[Keith Downing]

Isn't the limits inside "Vendor settings", where you need a password? Quite sure that's where I saw the upper limit (when he logged in there remotely) or can you see it somewhere else?

But I'm quite sure it's correct. I've been testing how low you can go and the laser didn't fire under 8%.

That's going to depend on the vendor. Mine, once activated, can be controlled by the user.

I also found this thread, 3 or 4 years old, but appears to describe a similar problem. He was vague at the end but said it was a wiring problem and he was able to fix it.
http://www.sawmillcreek.org/showthread.php?201280-RDCam-320-controller-1390-laser-150-watt-efr-tube

[Patric Sandelin]

Nice find! Thank you!
Too bad he didn't mention what wiring, but I will take a look tomorrow.

Also found the vendor password in that thread. My min power was set to 1%.

[Keith Downing]

Nice find! Thank you!
Too bad he didn't mention what wiring, but I will take a look tomorrow.

Also found the vendor password in that thread. My min power was set to 1%.

He hasn't been online in awhile, but he does list his skype username in his profile. He probably wouldn't mind answering questions via skype chat if you feel so inclined. Most SMC members are pretty helpful on and offline from my experience.

[John MacDougall]

Check out the Sarbarmultimedia YouTube channel. This guy is amazing. I can't find the particular video but he shows how the power output is not linear like the percentage numbers would suggest. The rise is very steep from 0 to 20 or 30% or so, then flattens out to a much lower slope from that point. That would explain the results you got in pic 3, 500 speed.

[Dave Sheldrake]

Check out the Sarbarmultimedia YouTube channel. This guy is amazing. I can't find the particular video but he shows how the power output is not linear like the percentage numbers would suggest. The rise is very steep from 0 to 20 or 30% or so, then flattens out to a much lower slope from that point. That would explain the results you got in pic 3, 500 speed.

Except power IS linear, the problem is that PSU's get set to over current by the manufacturer to make the machine seem more powerful than the tube really is, so what may be say 25mA for a safe limit on an 80 watt RECI may not be what it's getting at 100% or 30% I hear this comments about Russ's videos almost every day and the theory is flawed.

You MUST find out what current the power supply is giving out, until you know that you will be chasing your tail ...30%...50%...200%,2000%.....PERCENT of WHAT!

It CANNOT be checked by the manufacturer using teamviewer as it's a physical check that has to be done (the adjustment is made on a Potentometer inside the psu)

even a cheap junker Chinese supply can put out 50mA if the current limiter isn't set up properly when it's made, on a 40 watt tube that is supposed to run at 14mA even at 35% of 50mA you will be killing your tube.

The power distribution curve on a DC pumped tube is linear until you reach photon saturation or a state where there is no longer any gas at base state that can be excited by the plasma., at that point you will start to get a lot less for more input until the tube reaches it's failure point.

[Dave Sheldrake]

When the manufacture was logged in via Teamviewer, I saw a tube limit passing by on one of the screens and it was set to 99%.

Unfortunately I don't have a mA meter on the machine. If you measure it on the tube, I'm guessing it's very high voltage and not possible to use a regular amp meter?

Air assist is on.

Voltage and current are very different things, you can measure CURRENT using an ammeter but don't try to measure voltage :) a regular ammeter set to 0-50mA will work fie, disconnect the negative end, put the red probe to the tube and the black probe to the wire you just removed. isolate from metal surfaces. Press test and read the meter (analog meters are better as digitals don't always update fast enough)

[John MacDougall]

The power distribution curve on a DC pumped tube is linear until you reach photon saturation or a state where there is no longer any gas at base state that can be excited by the plasma., at that point you will start to get a lot less for more input until the tube reaches it's failure point.
Any possibility of a cheap Chinese junker power supply with cheap junker control software not providing a linear curve? Several variables beginning to end isn't there? Obviously still have to get mA meter to figure out your max setting. For disclosure, I'm NOT an electrical engineer.

[Patric Sandelin]

I also found this thread, 3 or 4 years old, but appears to describe a similar problem. He was vague at the end but said it was a wiring problem and he was able to fix it.
http://www.sawmillcreek.org/showthread.php?201280-RDCam-320-controller-1390-laser-150-watt-efr-tube

Got ahold of him and got this answer (for future reference):

I discovered the cooling water was running backwards it was put together wrong bought a new tube fixed problem, runs good now..

I saw in the beginning when there were bubbles in the system that it was running in the right direction. So that doesn't seem to be the problem.

Did another test today with 6mm acrylic, just to show that it's not bad or indifferences in the plywood:
357467

The manufacture so far says that their tests have shown the same as mine, which doesn't make sense to me. How can it be that there are no speed differences between 40% and 95% power? And no change in cutting depths between 40% and 95%? More power = faster speeds. More power, same speed = deeper. Sounds more logical to me :)

[Scott Marquez]

It boggles my mind why every Chinese laser doesn't come with a mili-amp meter installed, because all the power settings that you input from either the computer or keypad are displayed as a percent of.......nothing, because they are never set at the factory to a specific level.
You need a test probe and a milli-amp meter installed to really see what your machine is doing.
http://www.sawmillcreek.org/showthread.php?243119-Options-for-laser-power-meters&p=2569484&highlight=#post2569484
Scott

[Patric Sandelin]

It boggles my mind why every Chinese laser doesn't come with a mili-amp meter installed, because all the power settings that you input from either the computer or keypad are displayed as a percent of.......nothing, because they are never set at the factory to a specific level.
You need a test probe and a milli-amp meter installed to really see what your machine is doing.
http://www.sawmillcreek.org/showthread.php?243119-Options-for-laser-power-meters&p=2569484&highlight=#post2569484
Scott
Ordered! Thank you very much :)

[Kev Williams]

Just based on pictures, especially in the first post engraving @ 500mm/sec, your max depths are very close to my 80w Triumph's depths at "my" 70% power- "my" refers to the fact that with 20° water when vector cutting, at 70% power my mA meter holds a dead-on 27 reading. I can ENTER up to 95% and I'm sure the output will raise accordingly, but I won't :) --

This is why you NEED a mA meter, so that you know you're not overdriving your tube, and also, to know if your power supply is or isn't limiting the power to the tube...

Your results appear to be the result of a 'governor', your power output being limited by either the software, the PS or both. Check the software, somewhere in mine it states a 95% max. Your's may be set correct, or maybe it's set for 40%? Likely not...

If a meter shows your power stops at say 12mA, it's a good bet the PS is adjusted too low. Ask Dave how to fix that! ;)

If you find your meter is linear to the percentage of power, reaching 25 to 30mA but with no power increase, could be a wrong power supply, bad power supply, wiring...?

Get that meter installed!

[Patric Sandelin]

Alright, I've got some readings!

40% 15,7mA
50% 19,8mA
60% 23,6mA
70% 26,9mA
80% 30,1mA
90% 30,6mA
95% 30,4mA

According to the sticker on the tube, it should be an EFR F8 http://efrlaser.com/3-co2-laser-tube/200479
According to the sticker on the PS, it's this one http://www.jnhyec.com/en/productxx.asp?signid=115&proid=156

[Kev Williams]

Interesting that your 70% and my 70% are nearly a dead match as to mA output...

Seems next up is to measure the length of the tube to verify which one you actually have? Looks like the power supply is definitely the right one...

You should very well see a definite difference between around 20mA power and 30mA power, which it appears you're not.

I mentioned the looks of your engraving in the 50% range look like mine at full power, which I assume is somewhere close to 80w.
Also interesting is that at 20mA where you're engraving matches mine, if your tube should hit 130@30mA, 20mA- 66% of 130- comes to roughly 86 watts... roughly the same as mine.

SO, if you're getting an 85w burn at 20mA, that does indicate a 130w tube, but no additional power, but YES additional mA...

This is where I run out of knowledge!

[Patric Sandelin]

The length of the tube matches the F8, 1850mm.

[John Lifer]

PS working correctly, but output stops, bad tube?

[Kev Williams]

I was thinking 130w, oops-- re-do the math, 20mA is 66% of 30mA, 20mA looks like my 80w, but 66% of 150 is 100 watts-- I'm thinking you should be deeper...

Ok, just stopped and did my own test for comparison... I think I used maple, not sure to be honest--

here's my settings, from 10 thru 80 power, 500mm/sec, .06 was the gap on all--
357482

the result, drastic differences to 50%, then not so much...
357483

hard to see so I measured the depth of each,
I scraped the tail of the caliper a bit in each square to level the high spots a bit,
357484

substantial depth differences from 10 to 50, then only an additional .010 deep from 50 to 80, but small changes in each...
357485

Interesting to know... another factor at play here is the focus, the deeper you go the more out of focus, which means part of the reason for less depth at higher powers is less beam density to cut deeper as it gets deeper..

If you have some caliper mic's, measure your cut depths, might provide a clue!

[Dave Sheldrake]

40% 15,7mA
50% 19,8mA
60% 23,6mA
70% 26,9mA
80% 30,1mA
90% 30,6mA
95% 30,4mA

According to the sticker on the tube, it should be an EFR F8 http://efrlaser.com/3-co2-laser-tube/200479
According to the sticker on the PS, it's this one http://www.jnhyec.com/en/productxx.a...=115&proid=156 (http://www.jnhyec.com/en/productxx.asp?signid=115&proid=156)

Figures for Current are great, pretty much bang on the money, bit of a tail off at the top end but overall well within what they should be

Tube is a good make the F series original tubes are tough and reliable

The PSU is a mid range model, certainly a LOT better than most of the Chinese versions, no gains to be had by changing that if it's working properly and the tube residual current figures suggest it's running fine.
This is where it all gets a bit complicated.

Take a beam in the correct focus of 50 watts @ 10mm per second speed
Take a second beam at 100 watts, on paper it should be able to cut at twice the speed (twice the power being fired out)

It won't, that's nothing to do with the tube or power curve, it's to do with the materials and the fundamentals of the way a laser processes, in general once you approach the *sweet spot* of any given material you start to need the doubling factor, twice the speed needs 4x the power, of twice the thickness means going 4x slower etc etc.

Some of this is based on absorption rate, beam profile, material band gap vs wavelength photon energy and a number of other factors (that in general are pretty boring and mean little unless you REALLY need them)

At this point you need to start looking at other assisting factors (for acrylic not so much) but on wood air...lots of it travelling very fast (the CO2 generated by the lasing action blocks the IR wavelength like a brick wall) so you need to make sure the lasing point is clear of it

Carbon...there is a reason they use carbon tablets in cases of radiation poisoning, it loves electromagnetic radiation like a sponge loves water, get as much of that out of the cut path as possible (see above about fast air)

Kev is also on the money with focus, the depth of field of a lens set up isn't an area where the laser becomes a straight line, it's an area where the beam is within 1.4x the smallest spot size in the + or - direction (I don't know why it's 1.4x but it is for some reason) as you move away from the actual focal point the spot size changes, based on the gaussian curve of the beams profile, you move up or down and power density drops, you move more than 0.9mm in either direction and it starts to drop like a rock on a 50mm (2 inch) focal length lens) (the 1.4x figure for a 50mm lens is about (DOF) 1.8mm) the laser is still emitting more power (as you increase current) but that power is being spread over a bigger area so the density (power per sqmm is dropping)

A longer focal length lens will help you get a better depth of field, BUT it will also produce a bigger spot so your initial power density will be lower however it will keep an acceptable power density over a greater distance compared to a shorter focal length.

Where I get pinged daily is on the tests russ does where it demonstrates that increasing power achieves nothing or very little. If this were true then a laser over 80 watts on acrylic would never have been made as if you go above 80 watts the cutting ability never changes.If this was the case Synrad would not make 400 watt RF laser tubes and GSI would not make 250 watt DC tubes(and Mitsubishi would have sold me a 7.5kW CO2 if a 40 watt would do the same)

I've seen far more talented people than me produce good engravings with 100+ watt tubes but in general 100 watt+ tubes are cutting systems, they don't really make very good engravers as the density is often too high to achieve much depth control.

In Kev's piccys above the ability of carbon to suck up photons is demonstrated very well, soon as it starts to go dark, the ability of the laser to overcome the effect reduces...the darker it gets...the worse the effect (another reason why high power machines use inert gasses to prevent the formation of oxides on metal when they are cut) it's also a good illustration of why folks *generally* don't go over 80 watts for engraving tubes as the benefits of a tube costing 4x as much for a 150 just isn't there.

For Cutting...fast air, high pressure air and a longer focal length will increase speeds but don't expect to reach doubling until you start firing rather large amounts of energy at the materials (at massive extra tube/resonator costs)

An example, at XX speed a 220 watt SLC will cut 5/8th - 18mm MDF really nicely, to cut 25 mm at the same speed you need multi kilowatt power (start thinking 3k+)

This isn't a function of the resonators linear output, it's the science of the materials absorption coefficient and the photon energy you are shooting at it (PhotoChemical Vs PhotoThermal processes based on the materials band gap energy)

phewww.


Going back to your original pic Patrick, 12mm ply isn't going to cut well until you get a DOF of 1/2 inch, to get that you need to run an 8 inch focal length lens (not practical in most cases) or you will be hit by Kevs comments above (focal depth vs depth of field) as well as needing considerably more power to *force* the beam through something so thick with a much bigger spot size.

To cut 1/2 inch at decent speeds at 150 watts you would need an RF tube with it's much better beam profile and M^2 figures :)

You can certainly improve on what you are getting though, a small exit hole (1.5 - 2mm) with a 3 - 4.5mm standoff from the job (extended nozzle) running around 30 to 35psi of air will make a big difference.

[Patric Sandelin]

Thank you very much for that in-depth explanation. Much appreciated! Think I need to read it more than a few time to get everything :)

I am actually planning on dropping the supplied compressor for my regular shop compressor. Just need to figure out the filter situation and a way to turn it on/off in an automatic way.

Lets take the last test with the acrylic. Shouldn't I be able to see some type of difference between 40 and 90% power? There was actually a small difference between the 40% and 50%, the 14mm/s didn't "pop out" until I poked it. The protrusion on the underside from the cut on 16mm/s, feels the same.


In regards to Kev's question about depth:

500mm/s and I gently scraped off the "tops"
10% 0,2mm
15% 0,3mm
20% 0,5mm
25% 0,6mm
30% 0,9mm
35% 1,1mm
40% 1,15mm
45% 1,15mm
50% 1,15mm
55% 1,15mm
60% 1,15mm
65% 1,2mm
70% 1,2mm
75% 1,2mm
80% 1,2mm
85% 1,2mm
90% 1,2mm
95% 1,2mm

[Michael Henriksen]

You haven't accidentally set the max power on the controller display by chance? I once sold a laser and the new owner could not get it to cut anything even at 90% power. Turns out he had set max power on the display to 30 (Leetro controller).

[Patric Sandelin]

You haven't accidentally set the max power on the controller display by chance? I once sold a laser and the new owner could not get it to cut anything even at 90% power. Turns out he had set max power on the display to 30 (Leetro controller).
Unfortunately not. It's set to 95%.

[Jerome Stanek]

What is your max set in your software settings.

[Patric Sandelin]

What is your max set in your software settings.
Min 1%
Max 99%

[Dave Sheldrake]

14mm per second is about what you would expect from a 150 watt tube on 6mm acrylic at between 75% and 90% power, the ability to cut deep is a product of the materials rather than the tubes output. Acrylic is one of the cases when fast air won't help and may actually be detrimental.
To see the benefit of the bigger tube you would need to go to a longer focal length lens, problem is that's going to drop the power density as well so you will be back to tail chasing.

What you are up against is the properties of the material and the gaussian nature of focussed laser beams and that 6mm materials on a DC tube is at the upper end of what they will cut reliably at any sort of speed. For a better example, get some 2mm thick material and run the same tests, if the machine is running right then the 2mm will cut a LOT faster with a 150 watt compared to an 80 watt

[Keith Downing]

For a better example, get some 2mm thick material and run the same tests, if the machine is running right then the 2mm will cut a LOT faster with a 150 watt compared to an 80 watt

This is a good next step. Given that your power outputs at the different %'s look reasonably correct you should see a difference in the cutting at the very high end of the speed spectrum.

[Mike Lysov]

Do you mean 100mm/m?
100mm/s is a very fast speed that translates into 6000mm/m
and 500mm/s is 30000mm/m

To be honest I do not believe that you can cut through 12mm thick plywood on a 150W machine. I have a 280W laser with UK tubes(2x140W) and I cannot even cut through 9mm plywood at any reasonable speed. To cut 16mm thick MDF I use about 500mm/m and 90-95% power and for 9mm MDF I use about 1350mm/m and the same power. So you would guess that speed between 500 and 1300 will be ok for softwood interior plywood but it is not. I believe the thick layer of glue between veneer sheets contributes to very bad quality edges and timber knots make it hard to cut through. 19mm thick solid pine though is cutting like a butter at 1000-1200mm/m and I barely see any knots problems with solid pine.

[Rich Harman]

To be honest I do not believe that you can cut through 12mm thick plywood on a 150W machine.

I've cut through 1/2" ply at 80W with no problem, even 3/4" oak. Recently I cut through 6mm marine ply, charred edge, but it worked. I can absolutely cut 12mm regular ply on my 130W machine.


I have a 280W laser with UK tubes(2x140W) and I cannot even cut through 9mm plywood at any reasonable speed.

Not being able to cut, and not being able to cut at "any reasonable speed" are very different. A reasonable speed for one person may not be for another. I consider the speed to be "reasonable" if it is faster than cutting with a jigsaw. For example, I recently cut parts for a 20ft boat out of 6mm marine ply. For the long strakes (8ft each) the cutting was too slow. Instead I just used the laser to mark the lines then I cut by hand. However for the frames it was faster to let the laser do the cutting - I just had to sand the charr off the edges.

[Patric Sandelin]

For a better example, get some 2mm thick material and run the same tests, if the machine is running right then the 2mm will cut a LOT faster with a 150 watt compared to an 80 watt
The thinnest I have is 4 mm ply, but should still work?

357588357589

[Michael Henriksen]

Can you show us screen shots of your Cut settings and machine settings?

[Dave Sheldrake]

on 4mm Ply 45mm per second and you are at the limit of what it will cut at on anything under a 200+ watt machine with fast air, 50mm per second is pretty fair for a 150 watt running normally at it's peak power

[Patric Sandelin]

I’ll make a table to map my actual amp readings to watt:

30mA = 150W



90%
30,6mA
153W


80%
30,1mA
150W


70%
26,9mA
135W


60%
23,6mA
118W


50%
19,8mA
99W


40%
15,7mA
78W


I didn’t take a reading on 45% so I have guesstimated it to 90W.

I stop seeing changes around 40-45, so 80-90W.


4mm plywood:
90W it cuts through at 50mm/s
150W it cuts through at 50mm/s

6mm plywood:
78W it cuts through at 20mm/s
150W it cuts through at 20mm/s

12mm plywood:
78W it cuts through at 4mm/s
150W it cuts through at 4mm/s

15mm plywood:
-

6mm acrylic
78W it cuts through at 16mm/s
150W it cuts through at 16mm/s


There’s no wood engraving differences between 78W and 150W.


So what’s the benefit/difference of having a 150W over an 80W? :confused:

[Ron Gosnell]

You're not running your tube at 30ma are you? It will burn out much faster.
Most folks try to stay at 20% under max power and some say 30%
That's why a 150w over an 80w on a glass tube as far as power goes. The 150 will run a little more like 110w and stay at safe levels.
How hard were you running the tube before the amp meter ? Hopefully you didn't damage your tube prematurely.
I don't run my 130w over 24ma just to play it safe.

[Keith Downing]

I was told by the guys that sell our laser that 95% of the max power is just fine on the Chinese machines with a glass tube. It's just that you don't want to run it at max power (or higher); but I was instructed that a 5% buffer was fine. On my 60 Watt it maxes around 22-23ma output.

Maybe it's a little different on the higher wattage tubes, but 20-30% seems excessive even as a conservative estimate.

[Matt McCoy]

30mA = 150W



90%
30,6mA
153W


80%
30,1mA
150W


70%
26,9mA
135W


60%
23,6mA
118W


50%
19,8mA
99W


40%
15,7mA
78W




Without knowing which tube you have, it does look like you might be overdriving your tube if you're at 30.6mA @ 90% power. Am I reading that right?

[Jerome Stanek]

Without knowing which tube you have, it does look like you might be overdriving your tube if you're at 30.6mA @ 90% power. Am I reading that right?

On my laser I have to keep below 90% power or it is over driven. I have a 60 watt tube so now I have the max power set at 85% that way I over drive the tube even if I put in 90%

[Dave Sheldrake]

30.6mA is fine on a 150 watt F series,

% controls are worthless without knowing CURRENT...never trust percentages without knowing current.the 95% figure is right,and is for a properly adjusted PSU, it gives a 5% buffer for current spikes

The speeds are about right for an average 150 or a good 80, the 150 watt tube will do it for a lot longer than an 80 will (like running a 300hp engine at 2,500 revs or at the red line) to get the same speed in a lower gear

If you go to thinner materials you will get more speed, you will also need fast air (from a dry air supply on a shop compressor)

Engraving is a different animal, once you start generating carbon (why the engraving looks brown etc) you are trying to engrave a substance that sucks up lasers like a sponge does water.

For a demonstration of the above...try running 4mm plywood at 95% on an 80 watt tube at 50mm per second

nothing so far about any of your comments or figures is a surprise :) (remember, bigger tubes give smaller spot sizes are the incident beam is bigger hence higher power density)

[Mike Lysov]

I've cut through 1/2" ply at 80W with no problem, even 3/4" oak. Recently I cut through 6mm marine ply, charred edge, but it worked. I can absolutely cut 12mm regular ply on my 130W machine.


Sure you can do it but not at 100mm/s. That was my initial question if time unit is correct on the specified speed. It should be 100mm/m
I have also Synrad 100W machine, never tried to do thick plywood on it but have done a lot of 9mm MDF signs. The speed required for it is 1%. I cannot say exactly how much it in mm/m but I can guess that it is about 400mm/m top. So it is close to 1300mm/m speed on my 280W machine for the same material.



Not being able to cut, and not being able to cut at "any reasonable speed" are very different. A reasonable speed for one person may not be for another. I consider the speed to be "reasonable" if it is faster than cutting with a jigsaw. For example, I recently cut parts for a 20ft boat out of 6mm marine ply. For the long strakes (8ft each) the cutting was too slow. Instead I just used the laser to mark the lines then I cut by hand. However for the frames it was faster to let the laser do the cutting - I just had to sand the charr off the edges.

it is true, but I am talking about doing someone's order, not something for internal use. For me even at the speed where only knots a problem there is much bigger issue with edges. Not because they are charred but because the glue between timber sheets is so bad that when you look at edges you can see holes in a glue layer. I have had only one client who wanted a plywood sign for outdoor so bad that he said they would not care about quality of an edge as their priority to have a sign outdoor mounted. For all the rest who asks me to do thick plywood I have to explain that they will get a shape very bad edges and they usually do not want it to be made of plywood anymore.

[Joseph Shawa]

Crazy but I spent most of the wee hours this morning chewing on the same problem with my 150 W laser.
I am using LaserCut software.
I wanted to cut a bunch of small 1 mm x 5 mm square holes IN POLYESTER. I kept getting chads and wanted the cleanest cut with no debris left.
BIGGER pieces seemed to cut out cleanly but I thought that maybe it was melt keeping them from falling through.
So, I adjusted the settings on the squares and found that for the small squares the best setting on my machine was speed/power/corner power was 100/40/25.
I stretched the pieces to be 15 mm long and the best cuts came at at 100/60/25. 100/100/5 did NOT cut through nor 90 or 80 or 70 power. With longer cuts on bigger pieces I can run at 100% power and speed and for whatever reason there is NO issue.
I cannot figure out why. I just have to assume that it is the software or power supply but I'm not sure how to find out.
I did finally get rid of the chad problem, though. Rather than cutting just squares I used the entry path tool to start the cut in the middle of the cut piece and exit there as well. The cut was much smoother; almost unnoticeable at the beginning and end points.
So now I just slow the speed to a bit an all my cuts are clean.

[Kev Williams]

Lasers are funny animals. No two are alike, and many times what works once on one machine never happens again--

My 80w Triumph, with a 2" lens was able to cut thru this 20mm+ thick piece of cherry in one pass-- Slow, but one pass--
The burn is consistent. All was right with the world that day.
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So I put in the 3" lens, assuming (wrongly) that with the longer focal length, it should make it thru in one pass also, maybe even faster....
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--You can see the multiple burn depths, I think it took me 4 passes, and even then I had to snap off the corner. It just fell off after the 2" pass.

I've tried to cut thru other, less thick wood in one pass, pine and maple I think, wouldn't do it. Haven't tried this piece of cherry again, maybe it will, maybe not...
I'm thinking probably not...

So many variables involved with these machines. And they're finicky. And some stuff- like certain plywood glues- are like Kryptonite to lasers.
A few days ago I finally changed the X belt on my LS900. To do this required removing the mirror over the lens, which a few years ago I made 'adjustable' ;) ...
After getting it all back together, I found the beam spot was hitting a full mm off it's old position in both axis's. Easy to fix--
And now the laser seems to work better. Checking the mirrors, my laser's hitting the mirror and lens more centered than it was before. Good!
But for some reason, my red light is now so dim I can barely see it.. not good! Not sure why, as it's hitting the mirror good, and seem to be hitting the lens near the center...
So why is it half as bright? (FWIW this LED is normally not all that bright, on purpose, attenuated by the factory so the dot is smaller and easier to actually see where it is)
Even though it doesn't look like it, maybe it's hitting part of the mirror housing or the lens barrel..?

--changed the belt, and the whole machine's normal 'attitude' changed.

speaking of beams hitting things, you guys having trouble cutting thru things USING A LENS CONE, try removing the cone to see if that helps.
I found out my cone blocks some of my 3" lens's beam (partly why the cherry wouldn't cut) and it blocks a ton of my 4" lens's beam.
I haven't used my cone since about week 2. I firmly believe they're counterproductive. The 3 metal laser's I've owned never had one. Must be a reason... ;)

[Joseph Shawa]

"I haven't used my cone since about week 2"

How do you keep your lens clean? Seems backblasts of smoke would soil it quickly.

[Kev Williams]

The air hose normally connected to the cone I have wide open, running down the side of the lens tube to blow the smoke away from the lens when I'm cutting or engraving smoky stuff like leather, works okay. Lens still gets dirty but not all that fast, and cleaning it's a piece o'cake since I don't have to take the cone off! ;)

I'm always changing lenses too, I engrave leather with a 3" lens, most else with a 2", so it just works well for me with no cone.

[Rich Harman]

How do you keep your lens clean? Seems backblasts of smoke would soil it quickly.

I still have my cone on (it is part of the lens holder) but I have rerouted the air assist to outside the cone similar to what Epilog does. My lens remains much cleaner than when I had air blowing through the cone.

[Bert Kemp]

How does it keep it cleaner blowing on the outside rather then thru to cone, don't get how that works??



I still have my cone on (it is part of the lens holder) but I have rerouted the air assist to outside the cone similar to what Epilog does. My lens remains much cleaner than when I had air blowing through the cone.

[Rich Harman]

How does it keep it cleaner blowing on the outside rather then thru to cone, don't get how that works??

I think when blowing through the cone some sort of vortex is created which can suck things up into it.

[Dave Sheldrake]

I think when blowing through the cone some sort of vortex is created which can suck things up into it.

True, if the air enters at the side into the cone it works a little like one of those cyclone vac cleaners and stuff gets sucked up into the lens chanber

[Kev Williams]

My cone just screws to my lens holder, I assume most are the same way. I had Triumph make me several different (longer) lens holders,
one is 8" long, so I can 'reach' stuff I need to engrave with the table removed.
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I can put the cone on all of 'em if I want ;)
Another reason I don't use a cone, OR the auto-focus's on my other machines, is they're in the way-- I do a lot of engraving on things that are stepped, or otherwise have high places and low places, and I can't engrave the low places if the cone or focus plunger hits the high places! :D

...counterproductive... ;)


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[Joseph Shawa]

Seems that an air "ring" around the lens would keep clean air only at the lens but a cone tip would jet the air out and would disallow smoke entry into the cone/lens.

I have thought about running a small air line to each of my mirrors to keep them cleaner. Anyone do anything like that?

[Dave Sheldrake]

I have thought about running a small air line to each of my mirrors to keep them cleaner. Anyone do anything like that?

Yup, all of mine have it, it also helps to keep them cool on the more powerful machines. Especially if you tap off some air above the lens, it stops dust floating down through the beam entry hole in the head and settling on the upper side of the lens

[Bert Kemp]

ok Maybe I'll move my air to the outside and see if its better

I think when blowing through the cone some sort of vortex is created which can suck things up into it.