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Thread: Correct tube running figures?

  1. #1
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    Correct tube running figures?

    Ok, I have a new tube installed in my china blue laser. The specs according to the ebay listing:
    Specifications:
    Max Power: 50W
    Wavelength:10600nm
    Length: 850mm
    Cooling System: Water Cooling
    Triggering voltage: 22KV
    Operating voltage: 16KV
    Operating current(mA): 0-20
    Outer diameter: 50mm

    Math says that 20ma is only 44 watts. To get 50w from this tube based on 22kv, that works out to 22.7ma which is above their spec. 40w which is what may here have said this tube is works out to 18ma.

    However, a statement like "Running an 800mm at over 14mA will kill it very quickly" makes be extremely cautious. I have also seen 16ma and 18ma also mentioned in places as a save max.

    This tube measures 31 1/2" long. That is 800mm. So the length as stated inside the ebay listing is WRONG. They state it 50mm longer than it actually is. However in the listing title it says the correct length "
    New CO2 Laser Tube 50W 800mm".

    Every ebay listing I can find for a 40w tube says its 700mm long.

    Laser lengths are all over the place depending on where you actually look.

    On Light Object (dot) com, their 40w tube is 850mm long.
    On Boss Laser (dot) com, their 40w tube is 720mm long.
    On Rabbit Laser USA (dot) com, their 40w tube is a whopping 1010mm long.




    ARRG! What is it REALLY and where would I look to find data to back that up? Its not that I don't trust yall. But, well, I like to understand why someone says "x" is what it is or what it should be.

    So far, 14ma is the lowest anyone has stated. So until I can determine otherwise, I guess that shall be the max setting being one to err on the side of caution. Which, with the meter jerry rigged until I can get a box done, that works out to 72.5% on the panel to give 14ma on the meter. Both the analog and a confirming digital one temporarily hooked in series. With both meters reading the same figure, I can trust the old analog as being reliable and correct. Yea, its not like I am overreving a vintage Duesenberg. Its a $150 ebay tube. I get that. But I would rather not piss $150 down the drain needlessly and would much rather set the machine up correctly so its both efficient and reasonably reliable long term. Even if that involves it not putting out 50w.

    So, next question along these lines...how to reset the power supply. There is no adjustment screw hole either on the top nor the front. There is a hole on the bottom of the PSU, completely unmarked and not easily seen except with a mirror. Again, erring on the side of caution, I resist the urge to blindly stick a screwdriver in the hole on the side of a 22kv PSU that could easily stop my heart as wink an eye. So, I suppose its time to dismount the PSU and see about looking in the hole or removing the case to see what lies within. Can this "50w" psu be set to only deliver 14ma (or if it turns out 18ma is safe) when the panel reads 100%? That way I can't accidentally set the power to greater than the tube's capability. I have lots of files that used to run 100% and that might have contributed to the early demise of the original tube. And I would like to set the machine so 100% correctly matches the tube so I don't have to worry about forgetting to reset the power on those old files.



    [SIZE=1]Generic Chinese 50w 300x500
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  2. #2
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    Like I said maybe a few weeks ago, there is no such thing as a 50 Watt tube. Now your finding out the size and mA don't match.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  3. #3
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    Quote Originally Posted by Bill George View Post
    Like I said maybe a few weeks ago, there is no such thing as a 50 Watt tube. Now your finding out the size and mA don't match.
    Which is why I am attempting to make sense of it all. Where can I find out the CORRECT mA rating?
    [SIZE=1]Generic Chinese 50w 300x500
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  4. #4
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    Quote Originally Posted by Mike Audleman View Post
    Which is why I am attempting to make sense of it all. Where can I find out the CORRECT mA rating?
    I would assume 40 watts or less, perhaps 35.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  5. #5
    Remember, you are measuring residual current not incident current. The tube is big negative resistor

    There are 50's Bill, 1,050mm long is a 50 peak these days at 60mm diameter from memory

    800mm tube is a 38 watt (peak 42 watt) hit it above 14mA and it's going to die very quickly, the bigger tubes tend to be both longer, have larger diameter resonator tubes and larger gas volumes available from the increased diameter so Photon saturation is avoided but do require more ignition current and run current to provide a stable lase.(especially if you get a dodgy one that is a hard-starter)
    You did what !

  6. #6
    There is no adjustment screw hole either on the top nor the front. There is a hole on the bottom of the PSU, completely unmarked and not easily seen except with a mirror. Again, erring on the side of caution, I resist the urge to blindly stick a screwdriver in the hole on the side of a 22kv PSU that could easily stop my heart as wink an eye
    That's the one demount the PSU, pop the top off to check for the pot, fire it up making adjustments when it's NOT running and away you go 22kv doesn't hurt much ,especially at low mA, I've had a few belts off of 200 watt PSU's and while annoying, unless you have a VERY weak heart and keep hold of the wires, unlikely to be fatal seeing as Taser is 60kv and 50 to 75mA (400mA at high volts DC is fatal in many cases)
    You did what !

  7. #7
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    And that is why Mikes OEM tube died its early death. Dave I have never seen the 50 Watt peak tube you have mentioned sold anyplace?
    They are sure not putting them in those eBay lasers sold as 50 watt machines!
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  8. #8
    the true 50's aren't common Bill, usually like you say they are over driven 40's, the 50's are pretty much the same price as the 60's so don't really get offered in new machines much as there is effectively no real world benefit over a good 40.

    HPC over here sell true 50's but very few mainstream dealers do due to the price differences and the need for bigger mounts (larger diameter)
    You did what !

  9. #9
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    Quote Originally Posted by Mike Audleman View Post
    Ok, I have a new tube installed in my china blue laser. The specs according to the ebay listing:
    Specifications:
    Max Power: 50W
    Wavelength:10600nm
    Length: 850mm
    Cooling System: Water Cooling
    Triggering voltage: 22KV
    Operating voltage: 16KV
    Operating current(mA): 0-20
    Outer diameter: 50mm

    Math says that 20ma is only 44 watts. To get 50w from this tube based on 22kv, that works out to 22.7ma which is above their spec. 40w which is what may here have said this tube is works out to 18ma.
    How did you do the math?

    16,000V x .020 Amps = 320 Watts. The tubes are very inefficient, without knowing the exact efficiency you cannot determine what the power output will be based upon those numbers. In order for this tube to be 50 W it would have to be about 16% efficient at converting the input power to useful beam energy.
    Shenhui 1440x850, 130 Watt Reci Z6
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  10. #10
    A really good tube like a GSI is 15% efficient,

    typically Chinese tubes at best push about 7 to 8%
    You did what !

  11. #11
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    Be conservative, and get more life from your tube. My EFR 80 watt supposedly has max output of 90 watts. Specs say max is 28mA, is that 80 or 90 watts? I assume 90 watts. I've run it up to 100% at 34mA for about 5 minutes cutting test samples to determine percentages when I first got it. That is way too much power.
    So, 28mA is 80% on my machine. I don't utilize over 75% which is 25mA and rarely go over 70% which is 23mA. I figure If I can't make it work at 75%, it probably won't work at 100% either. For sure not long
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  12. #12
    FWIW--
    My 80w RECI tube, according to the sticker, maxed at 110 watts...

    Awhile back I found a RECI website (haven't found it since) that stated they test their 80w tubes at 32mA, so I've always assumed my RECI is a 'true' 80w tube...

    My mA meter sticks exactly 27 at 70% power with 20*c water. So when cutting, 70% is my max. For engraving I've taken it to 80% once or twice just to see what happens, engraves wood very deep

    I've never worred about adjusting my power supply, I just figure 35 is 50%, 17 is 25%, etc... in practice it holds true...
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