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  1. #1
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    Join Date
    Sep 2007
    Posts
    26

    Need basic advice on pierce time, etc

    Hello all,

    We purchased a laser tubing cutter with a Raycus 500 watt generator and Raytools head. We are cutting .065" wall tubing at a rate of about 60 IPM.

    We have been faced with multiple problems. They promised .002" cut accuracy, but the pull collet chuck was more like .030" accuracy. (We have a limit of +/- .007") We designed and built a push collet chuck with a servo drive and that problem is solved.

    Next problem is getting a clean pierce hole. The operation is run by a Mitsubishi FX PLC. We purchased the software and have tried several mods to the program.

    We programmed a timer and it takes about 7/100 second to pierce the tubing. However; when we run the program it generally blows a much larger hole, like it has melted a puddle which then gets blown out by the oxygen. Our programming sequence starts with Laser On, then a timer delay for Chuck Rotation (set at .07 sec), then another timer for Oxygen On (set at .1 sec). The laser stays at 1mm from the work, no Z travel. It was on a Z axis, but their movement was about 1/2" and what we considered as too violent with no way to soften the blow at the end of travel. With the laser at cutting position, the material cannot contact the tip so we eliminated the movement. Their interface also does not include any other communication with the laser such as power level.

    So, my real questions...
    Is it absolutely necessary to be at a higher Z position to pierce? It pierces great doing a static shot at 1 mm cutting height.

    After the pierce time of .07 seconds, the servo motion begins. The acceleration and deceleration are set fairly quick; is it a possibility that to slow acceleration rate might be involved?

    We are running about 4 bar O2 pressure with a 1.5mm tip. We have tried up to 8 bar and as low as 3 bar but 4 bar seems to be the smoothest cut. We have been trying different timer delay settings in case the initial O2 blast is the problem with blowout of the pierce hole, but have not found a sweet spot.

    After the pierce, the cut is smooth and pretty, so I'm not thinking it's a problem with the laser or the head.

    Any advice will be appreciated!
    Don

  2. #2

    Re: Need basic advice on pierce time, etc

    On that thickness I wouldn't bother with higher pierce height. I might get rid of a pierce setting altogether, just set a delay from the beginning of the cut...which you also might not need. I'm running a 1000W raycus for flatbed cutting and don't run the pierce on anything 1/8'' or thinner, because of exactly what you said with the blown out hole issue. I have also tried significantly lowering gas pressure for piercing and that works well also, but that assumes you have computer control of your gas setttings (some machines I have seen don't have that for some reason). The pierce height is to avoid back splash and molten metal from ending up in/on your nozzle and to save your protective window...but if you aren't getting that problem you don't need to solve for it.

  3. #3
    Registered
    Join Date
    Sep 2007
    Posts
    26

    Re: Need basic advice on pierce time, etc

    Quote Originally Posted by LaserCutCo View Post
    On that thickness I wouldn't bother with higher pierce height. I might get rid of a pierce setting altogether, just set a delay from the beginning of the cut...which you also might not need. I'm running a 1000W raycus for flatbed cutting and don't run the pierce on anything 1/8'' or thinner, because of exactly what you said with the blown out hole issue. I have also tried significantly lowering gas pressure for piercing and that works well also, but that assumes you have computer control of your gas setttings (some machines I have seen don't have that for some reason). The pierce height is to avoid back splash and molten metal from ending up in/on your nozzle and to save your protective window...but if you aren't getting that problem you don't need to solve for it.
    Thanks!
    I appreciate the reply. I will try to delay the air and maybe find a sweet spot there. We also tried less than 1 bar O2 and the cut is still fine.

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