Murex tradestig ac220a welding thin aluminium

  1. andypandy Member

    Messages:
    15
    Hi guys, on a roll starting threads at the minute!
    Has anyone got any experience of welding thin aluminium (1~1.2mm) on one of these machines? The issue is on start up, it's like the welder starts with a big surge of current and instantly blows a hole in the thin material. I can start the arc on a piece of heavier scrap and drag it over to then weld the thin piece, so it's that initial surge on start up is my issue, anyone got any ideas? Thanks in advance!
     
  2. Richard.

    Richard. Forum Supporter

    Messages:
    18,351
    Location:
    Cambridgeshire
    On a switch it is a little more difficult but with Alu at that gage you need a good fit up. And get a filler in there straight away. You have an option of slope up so you can set that to allow a gradual increase from 0-main current which should give you time to get your filler in when the pool forms and the slope down to control the solidification rate thus to avoid a crator
     
  3. hotrodder Member

    Messages:
    4,586
    SE England
    According to the internet it has a min output of 3A in AC or DC TIG and the minimum/initial/starting current is set as a percentage (0 - 99%, default 30%) in a 'hidden' menu along with preflow time and slope up time. Manual is here but at the moment the link will probably show an internal server error... http://www.murexwelding.co.uk/gb/en/support/upload/Tradestig-AC-220-AC-220a.pdf Worth checking in case someone has upped the initial amperage etc

    As said a good fit up makes life waaaaaaay easier with thin ally. IMO when this is the case trying to 'sneak' up on it for tacking is usually harder than really short arc length, hot and quick... the usual rule of thumb for ally is ~40A/mm, for tacking i usually go with 1.5 or 2x this, stamp on the pedal* (briefly!!) and be ready to add some wire when necessary. Obviously when there's gaps you need to be a bit gentler with it and be prepared for the arc to favour one side of the joint i.e. add a little wire and manipulate the torch to drag the weldpool over. Dither too much and, even if the amps are low enough to not blow a big hole, it often still doesn't end well as the backside oxidises and the edges start pulling apart and throwing loads of wire it usually makes things worse etc

    * without a pedal i usually set short (0.5sec or so) slope times for a similar effect with a quick tap on the button
     
  4. andypandy Member

    Messages:
    15
    Thanks for the response guys, I think hotrodders tip about the hidden initial start up maybe the first place to look , because I literally touch the trigger and puff I have blown a big hole in it! Why have that initial start up %? Would you just not keep it @0% all the time as your ramp up will soon get you there anyway?
     
  5. brokenbiker

    brokenbiker Member

    Messages:
    10,437
    Location:
    Llanbobyll, south wales
    If you are welding thick Ali then you may need the initial current to be higher so you can puddle quicker, then have it drop down to normal welding current so you can get on and weld? I don't do tig but I do know that thick aluminium drags heat out like an ice cube.
     
  6. hotrodder Member

    Messages:
    4,586
    SE England
    It's less about saving a few seconds (slope times can take care of that), more about personal preferences and arc striking IME. Bigger/blunter tungstens used for thicker stuff don't strike as easily thinner/sharper ones. Obviously setting the initial amperage as a % helps as the actual amperage used is automatically adjusted but a very low initial amperage can make it harder to strike an arc reliably with a large, blunt tungsten... an initial amperage setting like 1% would be very frustrating when trying to strike an arc with a blunt 2.4 or 3.2mm tungsten at 160+A for example while for properly, stuuuuupidly thin stuff (way under 1mm) lower starting % can be helpful

    Many (most?) inverters probably override some extreme settings? For example the finish/crater current on my v205 is set as an actual amperage rather than a %. I leave it set to min (6A) but the machine doesn't actually wind all the way down to 6A before shutting the arc off when welding at 200A
    Initial amperage i usually leave at 50% most of the time. I can adjust the HF intensity seperately but the two are kinda related i.e. with the HF set to min slightly higher initial % is needed for something that'll work from welding stuff thinner than 0.5mm in DCEN through to AC at 200A
     
  7. b4lamb Member

    Messages:
    26
    Location:
    Wales, UK
    I weld 0.8 mm alu sheet all the time on my murex ac 220a I run 40 A with 2 sec slope up 60 Hz keeping the arc short as practical. I generally can't use the foot pedal so I'm on the torch finger switch. I use 2.4 mm zirconiated (white tip) but grind the end thinner to about 1.5 mm dia and a short 2 mm point. It balls to round after welding a bit with 70% clean width setting. I also always use a lens and no 6 cup with 8 lpm argon flow. If I have a butt weld with a gap I start on a solid piece and run in to one edge and run a bead along the edge to thicken it and the same on the other edge and then I weave to bridge the gap on the next pass. I normally have to stop when the heat starts to run away and restart a few seconds later. With a pedal you could back off but I'm normally in some awkward position so can't use the pedal.
     
  8. Wonderweaver

    Wonderweaver Member

    Messages:
    281
    Location:
    Manchester
    This thread is nearly 4 years old you know :doh:
     
  9. bletchmonster

    bletchmonster Member

    Messages:
    489
    Location:
    Cheshire. England.
    So? It's all still valid information. What's wrong with a bit of necromancy if somebody finds it relevant.
    I don't get this making a fuss when somebody digs up an old thread. I just read though it and found a couple of points useful to dwell on.
     
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