Quick Q For all?

[Things]

Hey guys, well I've had my 40W CO2 tube for a while now, it's just a cheapy from eBay. When I first got it, I used it for a while on my 15kV 25mA NST, which I'm now thinking is what has me in trouble here.

I also did a few runs of the CO2 laser in my cutter without a current meter. The other day, I installed a current meter to see my tube was being run at 29mA, eek!

Anyway, after turning down the current to a more reasonable 18mA max (About 55% PWM), I seem to get slightly better cutting speeds, but they still seem a bit, well, odd.

I have some 5mm acrylic I've been cutting. Originally before I knew the laser was being overdriven, I could reliably cut it at 2mm/s at 100% power. I have turned the current down, and I seem to be able to cut it pretty reliably at 4mm/s. However, I've seen youtube videos of people cutting acrylic and even with a 40W laser, it seems a fair bit faster than what I'm getting. I also seem to have some weird inconsistencies in the cut, and I'm never really able to get the _perfectly_ clean edge, although I can get pretty close at really low speeds.

So I'm wondering, could anyone else with a 40W laser maybe post some speeds and powers for whatever acrylic thicknesses you've cut? I'm fearing I may have ruined my lasers output a little from it's previous abuse, however there is no visible damage such as burning, it just doesn't seem to be performing that great. On the other hand, maybe I'm just expecting too much for a mere 40W laser.

PS: I'm running it on a water cooler set at about 10C, it seems to like the lower temps. What temps do you run at?

Cheers,
Dan

[Tech_Marco]

Dan:

There are many issues that may cause the cutting problem. First of all, those "40W" laser tube you seem on eBay is NOT a 40W laser but 32~33W. A true 40W must have mini 850mm long where 1000m(1m) will get you full 40W power (45W max) at 18mA. Plus, low quality "40W" has bad divergence. If you shoot it on a pieces of cardboard the burn mark may not be in 'circle' but something non-round shape or even worst in "8" shape. I keep telling folks not buying those tube even though it's cheap. The price is unreasonable low, lower than I could imagine.

Second, the quality of acrylic made a big difference. If the acrylic is make in China then you would have hard time to cut it. But if it's from imported, then the cutting seems much better.

Third. Check the focus point of the laser.

Fourth: Add air-assisted to the nozzle

Oh..glad to go....
Will be continuous ...
Church...


Marco

[Things]

Hi Marco, yes, I know these cheap eBay tubes are pretty crap - I will save up to buy a nice tube from you at some stage - already still recovering from the XY stages!!

I cleaned all my mirrors and focus lens, realigned everything and also flipped the focus lens so the flat side faces the cutting surface, and it seems i can now cut 5mm acrylic at 6mm/s, which is a pretty huge improvement.

Cheers,
Dan

[waltfl]

Hi dan,
I got a40W CO2 chinese with the DSP. my temperature is set to 20C with a tolerance of 1 C.
I cut cast acrylic with 10mm/s and 45% power ( 16mA).
what I have experienced is if you set the DSP laser PWM to 10,000 it cuts better then with 15 or 20,000.
but a sure sign that the tube is on the way out is if you need to slow down the speed and watch the color of the corona
it should be dark purple and the more it goes toward light it lost more and more power and if it is whitish is gone. you still
can engrave for some time with it but cutting is pretty much impossible.
marcos power description is correct with this cheap ones you only get a max of 35W new and it mostly gets down pretty fast to 20 to 25W
gretings
walt

Hey guys, well I've had my 40W CO2 tube for a while now, it's just a cheapy from eBay. When I first got it, I used it for a while on my 15kV 25mA NST, which I'm now thinking is what has me in trouble here.

I also did a few runs of the CO2 laser in my cutter without a current meter. The other day, I installed a current meter to see my tube was being run at 29mA, eek!

Anyway, after turning down the current to a more reasonable 18mA max (About 55% PWM), I seem to get slightly better cutting speeds, but they still seem a bit, well, odd.

I have some 5mm acrylic I've been cutting. Originally before I knew the laser was being overdriven, I could reliably cut it at 2mm/s at 100% power. I have turned the current down, and I seem to be able to cut it pretty reliably at 4mm/s. However, I've seen youtube videos of people cutting acrylic and even with a 40W laser, it seems a fair bit faster than what I'm getting. I also seem to have some weird inconsistencies in the cut, and I'm never really able to get the _perfectly_ clean edge, although I can get pretty close at really low speeds.

So I'm wondering, could anyone else with a 40W laser maybe post some speeds and powers for whatever acrylic thicknesses you've cut? I'm fearing I may have ruined my lasers output a little from it's previous abuse, however there is no visible damage such as burning, it just doesn't seem to be performing that great. On the other hand, maybe I'm just expecting too much for a mere 40W laser.

PS: I'm running it on a water cooler set at about 10C, it seems to like the lower temps. What temps do you run at?

Cheers,
Dan

[Things]

Hi Walt, odd that you're stating 16mA is 1/2 power, was this a typo? Most 40W tubes are only rated to 18mA max power, so 16ma for 1/2 seems high.

I will try changing the DSP PWM settings and see if it helps.

I am pretty happy with how it performs at the moment though, 6mm/s on 5mm acrylic at 100% power.

The glow in the tube is kind of a light pink. Has been this colour pretty much it's entire life.

Dan

[waltfl]

hi dan
you got it wrong 16mA ( the safe max power) is not half it is about 75% because 55% is 18mA = 100%.
to the corona color if it was allways light purple from the beginning then you got a bad tube allredy. I
have used now 3 tubes in the last 2 years ( heavy load work) and not one had a light purple in the beginning
they all was dark. but all of them was the cheapo and they lastet around 1,200 to 1,500 hours, not bad for cheapos.
greetings
walt

Hi Walt, odd that you're stating 16mA is 1/2 power, was this a typo? Most 40W tubes are only rated to 18mA max power, so 16ma for 1/2 seems high.

I will try changing the DSP PWM settings and see if it helps.

I am pretty happy with how it performs at the moment though, 6mm/s on 5mm acrylic at 100% power.

The glow in the tube is kind of a light pink. Has been this colour pretty much it's entire life.

Dan

[wctx1977]

hi dan
you got it wrong 16mA ( the safe max power) is not half it is about 75% because 55% is 18mA = 100%.
to the corona color if it was allways light purple from the beginning then you got a bad tube allredy. I
have used now 3 tubes in the last 2 years ( heavy load work) and not one had a light purple in the beginning
they all was dark. but all of them was the cheapo and they lastet around 1,200 to 1,500 hours, not bad for cheapos.
greetings
walt

Hi Walt, odd that you're stating 16mA is 1/2 power, was this a typo? Most 40W tubes are only rated to 18mA max power, so 16ma for 1/2 seems high.

I will try changing the DSP PWM settings and see if it helps.

I am pretty happy with how it performs at the moment though, 6mm/s on 5mm acrylic at 100% power.

The glow in the tube is kind of a light pink. Has been this colour pretty much it's entire life.

Dan

Hi!, is there a way someone can post a video or image of a good tube color or arc and a bad one to compare them? that will help a lot to determine if we still have a good working tube or already dyed. Thank you! we all will appreciate it.

[Tech_Marco]

I don't quite agreed to use the 'color' to determine whether a tube is good or bad. It's true that the color always showing 'purple' but the deepest isn't the key to tell it's a good tube or a bad tube. The level of color deepest is depending on the gas mixture they used to fill up the tube. Different manufacturers come up their own formula. I withnessed a tube with red/purple while other brand a new tube was in light pink. One of tube they even have the internal tubing tinted. Note that the CO2 laser isn't really just "CO2" gas. It's a mixture of other gas that ended up different color (always purple though). I'll try to get more info about this color thing and will get more hints how to determine a tube is good or bad.

By the way, I'll carry a new series of 60W and 80W laser tube in about 2 month (through ocean shipment). it's VERY stable and in GREAT quality. It's well known one of the best in the South part of China as this manufacturer only manufacturing 60W and 80W tubes, noting else. The demanding of this tube is very high and need to 'line up' in order to get it. I can't believe it. We have to call 7~9 days in advnace to order. There is a daily quota how many they could make.


Marco

[wctx1977]

I don't quite agreed to use the 'color' to determine whether a tube is good or bad. It's true that the color always showing 'purple' but the deepest isn't the key to tell it's a good tube or a bad tube. The level of color deepest is depending on the gas mixture they used to fill up the tube. Different manufacturers come up their own formula. I withnessed a tube with red/purple while other brand a new tube was in light pink. One of tube they even have the internal tubing tinted. Note that the CO2 laser isn't really just "CO2" gas. It's a mixture of other gas that ended up different color (always purple though). I'll try to get more info about this color thing and will get more hints how to determine a tube is good or bad.

By the way, I'll carry a new series of 60W and 80W laser tube in about 2 month (through ocean shipment). it's VERY stable and in GREAT quality. It's well known one of the best in the South part of China as this manufacturer only manufacturing 60W and 80W tubes, noting else. The demanding of this tube is very high and need to 'line up' in order to get it. I can't believe it. We have to call 7~9 days in advnace to order. There is a daily quota how many they could make.


Marco

Thanks for the info marco! I'm glad to hear that.

[Things]

The purple/pinkish glow is caused by the nitrogen and xenon. The discharge inside the tube will only change colour in operation if the tube has a leak, or you're driving it hard enough to bury gas in the glass walls. Helium and xenon are added to help the tube run at a lower voltage, otherwise you'd need over 100kV to start the tube.