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Thread: Flowing gas CO2 laser conversion from sealed gas

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    Default Flowing gas CO2 laser conversion from sealed gas

    What is needed to convert a glass tube sealed CO2 laser to a flowing gas laser?

    This approach appears simpler than building a CO2 flowing gas laser from individual components and having to mount and align optics, etc. The conversion would keep all other factors the same, just change the gas from sealed to flowing.

    The sealed glass tube laser was rated at 60 watts maximum. It is still operational, though at very reduced power.

    At each end of the tube, just prior to the optics, there is are several inches where it is possible to insert a gas line. Perhaps drilling the glass will not shatter it if done carefully, then a gas adapter could be inserted.

    Is there a specific location required for flowing gas laser gas lines, or can they be placed anywhere in the system?

    Any suggestions regarding the minimum cost requirements to setup and test the flowing gas laser? I got a Synrad power meter on eBay a few months back.

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  2. #2
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    Please dont drill, you'll never get the glass dust off the internal optics. A glassblower has a technique using a fine pointed torch flame for placing a bubble in the glass at that point, and joining into the glass. The glassblower can use a dessicant, to keep their breath out of the tube when sealing on. Its called "GLASSBLOWING" for a reason.

    If you leave glass inside the tube, the electrostatic fields in the tube will take the glass to the mirrors or windows, where it will cause problems.

    You can use TORR SEAL or other vacuum grade epoxy to seal on, but you must keep any dust out.


    When you let the tube up to air, it must be done very, very slowly, or dust will rush in.

    What you may call clean, a laser tube calls dirty, so you must not allow normal dust in the air to be sucked in.

    Otherwise it will run like a normal flowing co2, except it has catalysts inside the tube to regenerate the gas, and thus may need a leaner mixture of Co2 to run. This effect is tiny.

    Find the seal-off point and have the glassblower tap on there. You really do not need a massive "flow", flushing the gas in from one end may be fine.

    Those tubes are inexpensive, perhaps it would be easier to replace it.

    The distance from the end of the tube to the mirrors is short, this is difficult for anyone other then a glassblower.

    At least I do not see a "getter" in the tube to ruin your day. Getters turn to powder when exposed to air.

    Steve

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    If you have access to a clean room or a laminar flow bench, it would probably make things easier to keep "clean".
    Those who fail to grasp art are the ones who criticize it.

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    Default Clarification

    Quote Originally Posted by mixedgas View Post
    Please dont drill, you'll never get the glass dust off the internal optics. A glassblower has a technique using a fine pointed torch flame for placing a bubble in the glass at that point, and joining into the glass. The glassblower can use a dessicant, to keep their breath out of the tube when sealing on. Its called "GLASSBLOWING" for a reason.

    If you leave glass inside the tube, the electrostatic fields in the tube will take the glass to the mirrors or windows, where it will cause problems.

    You can use TORR SEAL or other vacuum grade epoxy to seal on, but you must keep any dust out.


    When you let the tube up to air, it must be done very, very slowly, or dust will rush in.

    What you may call clean, a laser tube calls dirty, so you must not allow normal dust in the air to be sucked in.

    Otherwise it will run like a normal flowing co2, except it has catalysts inside the tube to regenerate the gas, and thus may need a leaner mixture of Co2 to run. This effect is tiny.

    Find the seal-off point and have the glassblower tap on there. You really do not need a massive "flow", flushing the gas in from one end may be fine.

    Those tubes are inexpensive, perhaps it would be easier to replace it.

    The distance from the end of the tube to the mirrors is short, this is difficult for anyone other then a glassblower.

    At least I do not see a "getter" in the tube to ruin your day. Getters turn to powder when exposed to air.

    Steve
    Thanks for the tips. A few questions...

    The original gas seal-off point should be available. It is a closed glass stump and I remember seeing it.

    There are neon sign makers in my area, are these guys qualified to open the original tap with their equipment? It may be a bit more challenging to find the glass blower.

    For the gas, it sounds like individual bottles are recommended to adjust the mix of CO2, rather than a premix. Any suggestions for this setup (inexpensive is preferred). Also, is laser gas grade required or can I get away with welding grade gases?

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    Quote Originally Posted by absolom7691 View Post
    If you have access to a clean room or a laminar flow bench, it would probably make things easier to keep "clean".
    I setup a small lab room with a bench, but it is not sealed from outdoor air. The air quality in my area is poor, contributed by significant pollution, dust and high humidity. An example of air quality problems are that the tools rust quickly. If locked in a cabinet they do better than outside the cabinet.

    I could put a door on the lab room and perhaps run a filter with activated charcoal and a hepa filter. I recently built a filter, but the blower motor is low quality and should not survive continuous use.

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    About six months ago I purchased this gas mixing box. It is sitting at a friend's place and shipping is too expensive. Perhaps you can suggest parts to yank off it then connect up to a new setup.

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    There is a good chance the neon shop will be able to do it .. whether they will or not you'll have to find out yourself. Usually the fill ports on these tubes are on the outer gas jacket, you'd need to create a new hole somewhere else in the actual tube.

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    Quote Originally Posted by Things View Post
    There is a good chance the neon shop will be able to do it .. whether they will or not you'll have to find out yourself. Usually the fill ports on these tubes are on the outer gas jacket, you'd need to create a new hole somewhere else in the actual tube.
    Unless the Chinese went really cheap, that tube will be pyrex. Pyrex or 7740 glass is much different then the 080 or 088 lead glass the rest of the world except Europe uses for Neon signs. Pyrex will not bond to to lead glass, the expansion characteristics are different, an dit crack when it cools. Europe does use Pyrex for much of their Neon signs, for some reason, probably due to the German and Dutch quest for perfection in their Neon work. That and the fact that Pyrex can be oven baked without cracking, making it easier to outgas the glass.

    If the metal to glass interface in the lead through seals is "moussy grey" its probably a Kovar seal to Pyrex, if the glass to metal seal where the wires is at is a off orange or copper color, its probably a Dumet seal and is leaded glass. There is a 80% chance what I'm telling you is correct, but if they used a rare alloy for sealing called Fernico, its lead glass, and silvery grey as well. Fernicois what was used on most of the old radio tubes, the Chinese still make much tube gear, and they may have some Fernico around. maybe 20% chance its Fernico.

    As for the box, I'm not sure if it can do a low enough flow for a small tube, but leave it as it is.

    Steve
    Last edited by mixedgas; 06-10-2012 at 10:43.

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    The gas port is attached to the outside jacket, very close to the output coupler as shown in the photo below.

    The glue for the output coupler is mouse-grey.

    The glue for the full mirror appears to be silicon glue. It is flexible and compresses to the touch. Note: there is no water cooling on this optic. All other 60 watt laser tubes I have ever seen have water cooling on both optics.

    I had visited this very small factory that makes laser machines and saw their operation to make the glass tubes. It was a typical factory that operates with windows open 365 days a year. They had two rooms. One room appeared to be the room to install the optics. There were two V-shaped holders per laser tube. In the second room is was darker and there were three large glass jugs (maybe 25 gallons each) on the floor with hoses. I recall the worker using a foot pedal to pump the gas.

    This factory knew very well that their laser tube manufacture was inferior and sold their machines, typically, with Shanghai made laser tubes that lasted much longer.

    In doing internet research, no information was found for the type of glass used in the manufacture of sealed glass CO2 lasers by Chinese companies.


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  10. #10
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    [QUOTE=GregR;234215]The gas port is attached to the outside jacket, very close to the output coupler as shown in the photo below.

    The glue for the output coupler is mouse-grey.

    No, that is Torr Seal... Aka Hysol C1 White two part epoxy and made in the USA. Hysol C1 and Torr Seal are very similar, only a small change is made in formula to make the vacuum grade version. So you can use C1 for making your tubes. Some tubes I've seen were so bad as to have Silastic HV RTV silicone.. Not my idea of good. However, to quote Stalin, "Quantity has a quality all its own", ie many cheap tubes to them are better then one lasting tube, because the tubes ware out quickly. This way they sell more tubes.

    What I'm talking about is the lead through for the wires. Look under the red wire for the glass to metal sealing material. Although at this point I would not be shocked if its more epoxy.

    Making sealed tubes in less then clean conditions with open windows, is just asking for it. Especially in terms of gas cleanup, impurities, and reject rate.

    Steve

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