4t settings

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I have never welded with 4t, but as you may have heard, I am designing a control box that will add 4t functionality to my welder. So now I'm thinking about how to design that box around the ways that people actually use 4t.What do you use the "start amps" stage for? Is it typically down at a very low amperage that will just carry the arc to let you get ready to go, or is it actually hot enough that it starts to form a puddle? If you were welding at, say, 120 amps, what might you set the start amps to?What do you use the "end amps" stage for? Do you fill the crater during the "end amps" stage, or during downslope, or what? If you were welding at, say, 120 amps, what might you set the "end amps" to?Do you typically use different values for start and end amps? How so?Everlast PA160-STH... and that's about it!
Reply:For me if using the pedal isn't feasible then I'll always use 4T and as both my new Tigs allow 4T with a "minilogic" function where it allows me to cycle from high to low amperage continuously when needed without stopping the arc then that's the type of trigger arrangement I like.For me the starting amperage is always low, enough to initiate the arc but not high enough to start a puddle. It just allows me to get comfortable before getting into the actual welding amperage.I like a 4T setup where the actual welding stage is where the trigger is released so you are not having to hold the trigger down while welding.The "end amps" are enough to freeze the weld and you need a ramp down so your not immediately going from the high welding amperage to a stage that immediately freezes the weld pool with the resultant craters that form in the weld pool.Start and stop amperages need to be variable as different materials need different ways to approach what needs to be welded.For instance on Stainless you may need very low starting and stopping if the material thickness is very thin whereas Aluminium needs the opposite with a hotter start and finish.Hope this helps regards Andrew from Oz.We are Tig welders, gravity doesn't worry us.Miller Dynasty 350. 350 amps of awesomeness.OTC AVP 300 hybrid wave AC/DC inverter tig. (now retired)Kemppi MLS 230 amp for home, a sweet little AC/DC Tig
Reply:My miller dynasty has several options on 4t setups. Very adjustable,almost to much for the average Joe. The lincoln 355 squarewaves I use at work are very simple but very adjustable at the same time. What I like is when doing code out of position tig tube welding is being able to initiate arc at a low amperage and upslope at a chosen time but most important is being able to initiate downslope by clicking my button but having the downslope time being long enough that I can reposition myself then click my button again to begin upslope without ever stopping the arc. So you have no stop and start. Make sense?
Reply:Makes sense, yeah. Thanks.Everlast PA160-STH... and that's about it!
Reply:Joshua, Jody at http://forum.weldingtipsandtricks.com/index.php did a couple of segments on 4T.
Reply:The machine I use at the shop, Thermal Arc LT300, has fixed parameters for initial/final current. Both are set to be 1/5th of the welding current. The setting seems to work well for me. I weld mostly thin s/s tube and sheet and almost always working out of position. -rgfab