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  1. #1
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    Default Plasma Cutter help

    Hi guys, I received my 50 amp plasma cutter and now trying to cut with it. Everything is working although the tip that came with it has been rapidly eaten by the plasma arc after a few cuts. Some extra tips will be on order shortly. My technique must be wrong surely. Short of using it as a lightsabre the cuts seem to be a bit rough and I'm wondering how you fellas with plasma cutters are holding the torch to start and then make the cut.

    I have read that for thin material <3/16" you can drag the tip directly in contact with the metal and this gives a fine cut but for thicker you lift the torch tip some mm above the surface. The instructions say to place the copper tip in contact with the material to be cut then push the button and off you go.

    I'm using the recommended 65psi compressed air supply. It could be oily and / or wet but will this cause rapid tip erosion? Also the electrode seems to burn at the same time.

    Peter.

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  3. #2
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    Quote Originally Posted by Swarfmaker1 View Post
    I'm using the recommended 65psi compressed air supply.
    I use closer to 90-100psi with mine. Tip life seems fine.

    I've heard that dragging the tip causes accelerated wear.
    Cheers.

    Vernon.
    __________________________________________________
    Bite off more than you can chew and then chew like crazy.

  4. #3
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    Oil and Moisture will be your enemy with a plasma,
    I don't think they will effect your electrode life but they will certainly put the torch head to an early grave,
    Check your amp settings, if you are running it flat out on thin material you will get less life from you consumables ,

  5. #4
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    Moisture is great for destroying plasma consumables. Clean dry air makes a big difference to consumables life, and give better cut quality.

    Piercing is best done as far away from the metal as practical. If the cut height for example is 1.5mm then a pierce could be done at 3 - 4mm. Piercing too close to the metal can destroy a nozzle in one hit. If you've got a scratch start plasma (never used one) then I'd imagine the best way is to scratch at an angle so the nozzle is tilted to the material so there is some distance between the nozzle hole and the material when the arc starts. Because of the angle the sparks will also be going away from the nozzle and not bouncing back towards it.

    It's the molten material being forced back into the nozzle that stuffs things. Pierce at a greater distance, cut at a closer distance, but I wouln't say touching/dragging unless the tip is designed for dragging. For instance my hand torch has drag tips but all these do is create some distance from the nozzle outlet to the material via a thickness of solid copper. Also just because it is a purpose designed drag tip doesn't mean I'd pierce while it's touching the metal. Mine is pilot start so I don't need to touch the metal at all but when cutting with the hand torch and a drag tip I still tilt the hand torch away from the metal when piercing then straighten up once I'm through.

    I would never just put the nozzle touching the metal and pull the trigger, never. Do whatever you can to keep those sparks flying AWAY from the nozzle, not back at it.

    Keith.

  6. #5
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    Quote Originally Posted by Swarfmaker1 View Post
    Hi guys, I received my 50 amp plasma cutter and now trying to cut with it. Everything is working although the tip that came with it has been rapidly eaten by the plasma arc after a few cuts. Some extra tips will be on order shortly. My technique must be wrong surely. Short of using it as a lightsabre the cuts seem to be a bit rough and I'm wondering how you fellas with plasma cutters are holding the torch to start and then make the cut.

    I have read that for thin material <3/16" you can drag the tip directly in contact with the metal and this gives a fine cut but for thicker you lift the torch tip some mm above the surface. The instructions say to place the copper tip in contact with the material to be cut then push the button and off you go.

    I'm using the recommended 65psi compressed air supply. It could be oily and / or wet but will this cause rapid tip erosion? Also the electrode seems to burn at the same time.

    Peter.
    As others have said, there are two basic tip types, drag and stand off. Most smaller plasma cutters use the former as they maximise the machine's capabilities.
    Moisture and oil destroy tips and to a much lesser extent electrodes, so verify that your air supply is good as a first step. At work, I can actually hear the moisture explosively decomposing, machine gun like in the tip while plasma cutting at this time of year, due to the high moisture content in our winter air, particularly on foggy mornings. The tips don't appreciate it either. Another factor in short tip life is initiating the pilot arc and then not actually cutting for prolonged periods, as this leads to rapid erosion of the tip by the pilot arc. Piercing is quite hard on drag tips, particularly over 5mm thick and to be honest is best avoided where possible. Does your machine have adjustable post flow? Insufficient post flow may be contributing to rapid wear.
    On the subject of air pressure, I would say you are pretty well on the money. You can actually run too much air pressure which will hinder arc initiation and can adversely affect cut quality, but doesn't affect tip life too much from what I've seen. The small plasmas with drag tips will actually cut surprisingly well down to 30 odd PSI, but it's not ideal.
    I suspect the Chinese sourced tips are somewhat more expendable than the genuine tips that they copy - just as Chinese knock off mig contact tips wear out MUCH faster than the genuine items. Chances are your plasma torch will be a copy of a Panasonic, Trafimet or Cebora torch,with the Panasonic and Cebora variants the more common.
    You will find that tip life should improve as you become more experienced and in tune with your machine. You will fry a few tips and electrodes while you are learning and getting comfortable with the process. Luckily they are a fairly cheap item for the Chinese machines.
    From personal experience, I find that a plasma cutter gives it's best results when combined with a guide of some sort, be it a straight edge, circle cutter attachment or some other jig as it is quite difficult to manually track a line at the higher cutting speeds that plasma produces, particularly on sub 3mm material. Such guides can be as simple as a piece of angle iron or flat bar to run along or even plywood cut to the required shape for producing a multitude of profiles.

  7. #6
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    Thanks for the info . I have a LOTOS LD5000 sourced from eBay undoubtedly of Chinese manufacture. From your replies I think it's my technique at fault. I seem to get a lot of metal spatter shooting out the top which is probably the reason why the tip is in such bad shape. I'll look into adding a moisture trap and oil filter to the setup as well. I have a smaller spare tank which I can press into service.

    Spare tips are on the way...

    Regards,
    Peter.

  8. #7
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    I'm not sure if this would help for drag tips, but for my pilot start torch I would always start on an edge, or drill a hole to start on. For thin metal it's no problem to drill a hole and for thicker stuff, it makes such a big difference, its worth the effort. If I try to pierce the metal, I find it usually sprays molten metal back into the tip as others have said.

  9. #8
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    Thanks for that, I did seem to have all the problems on the thicker material, probably moved to fast and then started gouging and spraying all the metal back into the tip. The orifice became distored and the plasma arc became a fan. At one stage I saw two arcs.

    Do all the tips have copper ends?

    Quote Originally Posted by sossity View Post
    I'm not sure if this would help for drag tips, but for my pilot start torch I would always start on an edge, or drill a hole to start on. For thin metal it's no problem to drill a hole and for thicker stuff, it makes such a big difference, its worth the effort. If I try to pierce the metal, I find it usually sprays molten metal back into the tip as others have said.

  10. #9
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    Quote Originally Posted by Swarfmaker1 View Post
    I'll look into adding a moisture trap and oil filter to the setup as well.
    Regards,
    Peter.
    You ideally want to condense moisture out of the compressed air BEFORE the moisture trap. A moisture trap won't do that, only collect what is already condensed.

    Keith.

  11. #10
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    Quote Originally Posted by Karl Robbers View Post
    You can actually run too much air pressure which will hinder arc initiation
    From my experience that hasn't been the case. I set my pressure to around 90psi and don't change it regardless of the thickness of steel I am cutting, however I do adjust travel speed (ie faster on thin, slower on thick). Cut quality is always good, tip life is good and have not had any issues with arc initiation, or blow out.

    If I was this bloke I would try upping the pressure and just see how it goes ... he can always turn it back down if he runs into problems.
    Cheers.

    Vernon.
    __________________________________________________
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  12. #11
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    Quote Originally Posted by Vernonv View Post
    From my experience that hasn't been the case. I set my pressure to around 90psi and don't change it regardless of the thickness of steel I am cutting, however I do adjust travel speed (ie faster on thin, slower on thick). Cut quality is always good, tip life is good and have not had any issues with arc initiation, or blow out.

    If I was this bloke I would try upping the pressure and just see how it goes ... he can always turn it back down if he runs into problems.
    Not to say that Swarfmaker couldn't run more than his current 65 PSI, but excess air pressure is a common cause of hard arc initiation often mentioned in plasma cutting tutorials. This is because an electrical current requires increasingly greater voltage to jump a given gap as pressure increases, the same phenomenon that those who play with spark ignition engines will have experienced - a compromised ignition system will spark outside the cylinder, but fail to spark in the pressurised atmosphere of the combustion chamber.
    The low air pressure switch cut out point on my 120A plasma cutter is set around 500 kPa or 75 PSI although I generally run it in the 6-700kPa range and I set the pressure at 500 kPa on my small plasma, so it probably wouldn't hurt for Swarfmaker to try a bit more pressure, although I am leaning towards technique and inexperience as the primary issues in his case.
    I have experienced arc starting issues caused by air pressure when using a plasma for demolition work and cutting in a confined corner area where the air flow is somewhat trapped and pressurised.

  13. #12
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    OK Thanks for that. I'll read the other thread on plasmas which I think condenser setup was described. I did mean a condenser using a second tank.

    Quote Originally Posted by beefy View Post
    You ideally want to condense moisture out of the compressed air BEFORE the moisture trap. A moisture trap won't do that, only collect what is already condensed.

    Keith.

  14. #13
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    Karl, I'll play with the pressure but the spare tips are yet to arrive so I can't do much until then. Hopefully tomorrow. The way the post works these days you never know when to expect things.

    We'll see how it goes.

    Quote Originally Posted by Karl Robbers View Post
    Not to say that Swarfmaker couldn't run more than his current 65 PSI, but excess air pressure is a common cause of hard arc initiation often mentioned in plasma cutting tutorials. This is because an electrical current requires increasingly greater voltage to jump a given gap as pressure increases, the same phenomenon that those who play with spark ignition engines will have experienced - a compromised ignition system will spark outside the cylinder, but fail to spark in the pressurised atmosphere of the combustion chamber.
    The low air pressure switch cut out point on my 120A plasma cutter is set around 500 kPa or 75 PSI although I generally run it in the 6-700kPa range and I set the pressure at 500 kPa on my small plasma, so it probably wouldn't hurt for Swarfmaker to try a bit more pressure, although I am leaning towards technique and inexperience as the primary issues in his case.
    I have experienced arc starting issues caused by air pressure when using a plasma for demolition work and cutting in a confined corner area where the air flow is somewhat trapped and pressurised.

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