What is wrong with this 150W?

[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/showthre...-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:
IMG_2058.jpg

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/showthre...t=#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/showthre...t=#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.a...=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--
testsets.jpg

the result, drastic differences to 50%, then not so much...
a1.jpg

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,
a2.jpg

substantial depth differences from 10 to 50, then only an additional .010 deep from 50 to 80, but small changes in each...
a3.jpg

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

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).