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i was wundering if any one here has heard, seen, or done any plasma arc welding?how much harder is it the gtaw?is it worth the money?WELD TO LIVE LIVE TO RIDEA bad welder blames his equipment, a good weldor can lay a perfect bead on any thing
Reply:PAW is usually done as an automated process. I have never seen it done manually.We use a Deloro Stellite PAW for hardfacing at work and I believe it cost around a $120k.
Reply:In general, PAW appears to be used very little these days, and I think this is because there is only a small advantage over GTAW, and significant increased complexity and cost.I worked with automated PAW for many years in high production automotive component manufacturing.  The reason we used PAW vs GTAW is that with PAW you can maintain a constant low amperage "pilot arc" between the electrode and the nozzle which allows instant starting of the welding arc with no high frequency.  You can imagine that with GTAW it would be difficult to consistently get reliable arc starting for a short weld every 20 seconds.  We changed out electrodes at around 1000 welds.  Our welding parameters were setup to make a "conduction mode" welds similar to GTAW, no difference, but the reliabilty of arc starting and increased electrode life made PAW a good choice for automation.PAW is capable of producing a more concentrated energy density arc than GTAW, which spreads less than GTAW with increased arc length, which may be advantageous for precision, thin applications such as bellows welding.  PAW is not limited to automated processes, it can be done manually, just like GTAW.PAW can also be adjusted to produce very deep penentrating welds by producing a "key hole mode"  of welding.  This is a highly sensitive process best suited for automation, in which the intense concentrated arc density and plasma gas jet produce a molten hole fully through the workpiece, which closes and fills as the weld progresses.  The aluminum space shuttle tanks were welded with variable polarity, keyhole plasma. I have not done keyhole PAW, but from research I am aware that it can require a gas flow rate control to allow upslope of gas flow to establish the keyhole, and downslope of gas flow to ramp out of the keyhole.  For welds, such as plate seams, a run-on and run-off tab may be used to allow starting and finishing of the keyhole outside of the actual weldment.All that said,  I have a complete Thermal Arc PAW system availble for sale (gas slope control for keyhole).
Reply:I've done a mile or two of VPPA for Boeing. All automated.Two turn tables and a microphone.
Reply:I saw a video of a large cylinder being plasma welded, I believe it was 1" wall thickness, square butt welds (no groove/bevel) welded without filler in a single pass with 100% penetration. This was a fully automated machine  welding horizontally
Reply:Originally Posted by pulserThe reason we used PAW vs GTAW is that with PAW you can maintain a constant low amperage "pilot arc" between the electrode and the nozzle which allows instant starting of the welding arc with no high frequency.
Reply:Originally Posted by razerHow did it ultimately start and stop the main arc, or rather, what caused the arc to transfer to the workpiece (when you were using transferred arc)?
Reply:Originally Posted by PangeaYou bring the torch very close to the work and if it doesn't jump the gap, you manually pass a piece of tungsten between the torch and part real fast.
Reply:[QUOTE=pulser;52679  The reason we used PAW vs GTAW is that with PAW you can maintain a constant low amperage "pilot arc" between the electrode and the nozzle which allows instant starting of the welding arc with no high frequency. op not tryng to hijack..just that this comment by pulser struck a chord.. i find myself doing something like this with foot pedal when tigging to move around the workpiece..
Reply:Originally Posted by pulserSorry, but what are you talking about?  I recall we sometimes had issues initiating the pilot arc between the electrode and the copper plasma orifice, and yes you could get this to start as you described, but once we had a piliot arc there was no problem getting the welding arc to jump to the workpiece.  Since you have a pilot arc there is ionised gas at the torch tip which allows the main welding arc to easily initiate between the electrode and the workpiece.
Reply:Pangea, never saw the arc start problem you describe.  I assume maybe your electrode was recessed in the tip for keyhole welding, maybe that's the difference.  We had around 30 plasma systems running two shifts for 5 years, but these were set with the electrode flush, and we did conduction mode welds not keyhole.  I would guess maybe and increased pilot arc current may have helped the arc start issues, but I know our Thermal Arc units were fixed at 10 amps.
Reply:Is there really much difference between a $97 auto lens and a $300 auto lens. I know one is on/off and the other has a few fancy buttons, but I'm only talking about visual clarity of the puddle. Robert.
Reply:Originally Posted by [email protected] there really much difference between a $97 auto lens and a $300 auto lens. I know one is on/off and the other has a few fancy buttons, but I'm only talking about visual clarity of the puddle. Robert.