mig welders can anyone explain ?

Discussion in 'Mech Tech' started by lowie, Oct 2, 2011.

  1. right i ve started doing a few bits of welding on diago i've never welded before hence my numerous posts on this subject i ve welded practice pieces up no real problems but when it came to the real thing just kept blowing holes in the bodywork like this [​IMG]
    this is my welder its i giant 100 i know its not the best but is this my problem or the :censored: behind the tourch [​IMG]
    any advice criticism or even sarcasm welcome
  2. Diddymen

    Diddymen Moderator

    Some times not matter how good you are at welding you will blow holes in metal.

    the metal on your bus is probably a lot older than your practice pieces so behaves a bit different to clean new metal.

    Blowing holes is usually caused by several different causes - not having clean bright metal to weld to, imperfections such as a small pitted area of rust of paint getting into the weld pool will some times do it, having your welder turned up too high or keeping the weld pool in the same place for a bit too long. some times welding onto an edge of metal will cause it to burn back (tricky to avoid some times on butt welds)

    out of interest is the holes your burning on the new or old metal? and are you using gas or gasless welding? - gas should cool the weld a bit better and reduce burning through IMO

    For very fragile metal I some times use a peice of copper behind the weld to act as a heat sink and give it a backing to stop blowing through - the weld wont stick to copper.

    also if you are butt welding and there is nothing behind it is easier to blow holes so where possible try to joddle your joins

    I sometimes try to arc up on the newer repair peice and drag the weld onto the older metal of the bus.

    Dont try to do long welds on the bus on the thinner metal try to do it in a series of tack welds and join the dots.

    Other than that its just a case of getting to know which power and feed settings on your welder are best for working on your bus and keep practicing.

    If you've chopped off some bits from your bus have a practice on them if your not sure of your settings prior to welding on your repair
  3. cheers diddymen
    its gasless i am useing and the holes are in the old stuff but it s clean i think the welder a 100 amp i ve had the power down as low as it can go i ve tried all ways arc ing up on the new short blasts which does seem best
  5. Poptop2

    Poptop2 Moderator

    i am getting on better with the mig than the stick welder ,having said that someone else sets up the mig for me , and i find a series of tacks as diddy once advised me is way easier .

    i'm finding it tricky too but persevere and people on here will advise without judgement .
  6. You won't want to hear this, But I'd be welding that on no.3 on my welder which equates to about 80A. On low power by the time you've got the metal melted you'll be blowing holes or not getting penetration. I NEVER use settings 1 or 2 on my welder (20 & 50A).
    Gasless is by all accounts rubbish - never tried myself.
    You may have cleaned up the metal outside, but could still be very thin due to rust inside or over grinding it to clean it up. If you blow a hole, let it cool before you try and fill it up.
    Practise makes perfect. :)
  7. You need to switch to gas mig (CO2), its much better for this kind of thin sheet metal work, gasless mig (flux core) burns too hot, here's a technique I often use for when welding thin sheet metal, its called "breaking the arc" where you give a series of small spot welds in quick succesion, pausing slightly between each blob of weld allowing the previous weld to cool slightly before applying the next, this way you can "built up" areas, holes etc, when done correctly it gives the impression of a continious weld, takes a bit of practise, a reactolite welding screen is best for this. hope this helps :)
  8. i think it would help if you said what power and wire speed setting you were using
    the theory is a bit vague now (20 odd years ago!!) as you just learn what settings work best on your own welder. i do recall its the wire speed that controls the power so turning the amps down wont help. torch angle to the metal and which direction you weld in all makes a big difference as does the time of each weld. you can sit at a bench with nice thick new steel and do a continuous weld really easily. welding thin plate to a rusty bus is far harder.
    i have also heard gasless is crap but i have never used it. you are far better to invest in a decent mig with proper gas, even if its 2nd hand and get a much cleaner weld
  9. That's the thing everything is turned down as low as it will go
    I Wong get out to the bus for a week or so now
    I think I ll give everything a good clean up behind aswell
    And if that don't work blame the welder and either borrow one (fletch)
    Or buy a another new one with a higher ampage
    The one I have now is 100 amps would 150 cut it
    I know the more the better
  10. I agree you need to change to gas , I use a 5% argon mix and it works a treat , I did use gasless as my mig does both but it was crap same problems as your haveing .
    If you want good welds then use gas :)
    I got my 150 mig from screw fix for 117 pounds did not think it would be any good but it's not let me down yet after 1 beetle build and now the camper
  11. can t find either of them
    think my welder came from screwfix but i got it off fleabay
    but i hink its more amps makes a happy camper yes
  12. I had a 90A welder first - terrible. Then I got an old bigger one and all was much easer. When I sold the little one I demonstrated it and found it was ok after all. Practise makes perfect, but a better welder means less practise.
  13. I carnt get on to screw fixes web site at the mo but it was on there I'm sore , it may have been reduced when I brought it but it's still a good mig
  14. that should weld a piece of cake ..... slightly too big gaps you only want max 1mm and start by a series of spots . what size wire ? i use 1mm .looks to me your getting too big a molten pool then it just falls through, welding up hill is also harder . just do a series of big tacks
  15. No I now carnt find it on screw fix
  16. as everyone says above gassless isnt much cop i would buy a regulator and normal 0.6mm wire (better than 0.8 on bodywork as you dont need as much power to melt the wire) you shouldnt need to have the power setting down to the min with good steel i generaly have my power setting on 4 or 5 <out of 8> on a 180amp set i only ever turn it down to 2 if the metal is really thin and grotty alot of welding is down to how clean you get your metal also try pulsing the trigger on and off to allow the last spot to cool a little before the next this can help and if done correctly will leave fish scale looking welds if you try a long seam on bodywor at best distorted panel at worst loads of holes all over my welder has a knob that pulses on and off automatically although i never use it. your 100amp welder should do most things on your van i had a clarke 100amp mig for my 14th birthday and it lasted for years and i welded everything from bike frames, cars, my first bay, go karts you name it i welded it :D think you just need a bit more practice what i find is anyone car weld thick steel cars are totally different to general fab work

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