Problem Laser power "fatigues" during sustained cut


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    Default Laser power "fatigues" during sustained cut

    OK, I'm cutting 1/32" neoprene rubber (but have noticed this problem with other materials as well). I'm making a gasket, 14" x 1" with 100 rectangular holes that are approximately 0.125" tall and 0.075" wide. As the laser progresses further into the cut the power apparently "fatigues" so that while the first holes are fine, the last 20 or 30 do not cut all the way through. The panel meter remains steady as far as I can see. The outline cut starts out fine, but by the end (inch 30) the cut is not through. Speed is 10, power (set) is 60%. I found that if I "pause" after every five small holes and immediately restart, all holes are fine. If I pause every 5 seconds of the outline cut and immediately restart, it too is fine. What's the problem and how do I fix it? Thanks.

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    Default Re: Laser power "fatigues" during sustained cut

    Quote Originally Posted by RedDawg View Post
    OK, I'm cutting 1/32" neoprene rubber (but have noticed this problem with other materials as well). I'm making a gasket, 14" x 1" with 100 rectangular holes that are approximately 0.125" tall and 0.075" wide. As the laser progresses further into the cut the power apparently "fatigues" so that while the first holes are fine, the last 20 or 30 do not cut all the way through. The panel meter remains steady as far as I can see. The outline cut starts out fine, but by the end (inch 30) the cut is not through. Speed is 10, power (set) is 60%. I found that if I "pause" after every five small holes and immediately restart, all holes are fine. If I pause every 5 seconds of the outline cut and immediately restart, it too is fine. What's the problem and how do I fix it? Thanks.
    Check if the ammeter power is falling on it, if the problem is with certainty the power supply ....

    Now remains constant power on the ammeter during the cutting period there most likely be the laser tube ...

    The use of time has its laser tube?

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    Default Re: Laser power "fatigues" during sustained cut

    Smoke buildup in the machine?


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    Default Re: Laser power "fatigues" during sustained cut

    Quote Originally Posted by Dean448 View Post
    Smoke buildup in the machine?
    No, no smoke. The odor of the neoprene being cut is quite noticeable but any smoke generated is quickly and thoroughly exhausted. Probably fewer than 300 hours on the tube. I think the "telling" clue is that a "pause" of as little as 1 second "resets" the power for another 5-10 seconds of cutting before it starts to fade again. I'm leaning toward a problem with the high voltage supply but I don't know what the nominal value for that should be (and the docs don't help) or how to go about measuring it without a high range voltmeter. Even if that is the problem I would think the panel ammeter would show a noticeable decrease if the HV to the tube is also declining. I'm guessing from the quality of the cut that the delivered power to the material is falling by at least 50%.



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    Default Re: Laser power "fatigues" during sustained cut

    Other then the method you are using I haven't seen a safe way to measure the output of a PS. Any chance the control voltage into the PS is steady? Are all connections to the tube secure? Any leakage to surrounding metal?


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    Default Re: Laser power "fatigues" during sustained cut

    Are you using a CO2 laser? If so, how are you cooling it? Water temp might be too high.



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    Quote Originally Posted by jeepers94 View Post
    Are you using a CO2 laser? If so, how are you cooling it? Water temp might be too high.
    Sorry, should have said, yes it's CO2. Uses the factory water chiller which typically reads 34-35° C, just slightly above room temperature. Even if that is too high, I can't see a one second interruption every 5 seconds causing a recovery.



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    Default Re: Laser power "fatigues" during sustained cut

    Quote Originally Posted by RedDawg View Post
    Sorry, should have said, yes it's CO2. Uses the factory water chiller which typically reads 34-35° C, just slightly above room temperature. Even if that is too high, I can't see a one second interruption every 5 seconds causing a recovery.
    What is the power of laser tube? This temperature is too high, you should try to work at least 24 ° C ...

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    Default Re: Laser power "fatigues" during sustained cut

    Quote Originally Posted by RedDawg View Post
    Uses the factory water chiller which typically reads 34-35° C,
    34-35° C is much to high. Should be around 22° C or less.

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    Default Re: Laser power "fatigues" during sustained cut

    Quote Originally Posted by rodrigomartins View Post
    What is the power of laser tube? This temperature is too high, you should try to work at least 24 ° C ...

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    I misspoke, it's running at 28 deg. C, 80 watt tube. I still don't see that a "rest" period of 1 sec. is going to change the temperature of the water by any observable amount, hence I don't see that as having a variable degradation effect. Too hot and I can see an overall fall-off of the power, but it should be gradual over time and remain there and not "recover" from a 1 sec. off period. The manual says operate at 35 deg. C. or below, so it's in range.



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Laser power "fatigues" during sustained cut

Laser power "fatigues" during sustained cut