I'm either doing something really stupid or my mig is shagged. Bought a cheap secondhand mig, £30, SIP 100. Big CO2 gas bottle, gas coming out ok. Working indoors, no breeze, new nozel and copper tips, on full power with medium feed speed, and all I'm doing is making long trails of melted wire on the surface of the sheet metal. Tried holding it at various angles and distances, not once melted the sheet. Even tried different sheets.

Sheet metal is clean - no rust - and <1/8in thick.

Any pointers would be useful. Not the end of the world if the MIG is shagged, just made £25 on the gene I bought last week any never used, laid power cable instead.

I reckon the MIG is shagged. In all the bad welding and f*** ups I've seen and done there's never been anythiing like the stuff you describe. If opening it up doesn't show an bvious fault, and you have good continuity between transformer and tip, then it sounds like you need another unit. It might be worth taking it to your local welding supplies shop. They might be able to fix it, or they might have a decent second hand unit you could buy.
John

Just a thought ! try turning the wire speed down, sometimes the current cant keep up with the wire speed, slowing down the wire will allow the arc to fully penetrate both surfaces with the wire. My cebora 130 will weld like crap if the wire speed is not spot on, when it is it hums like a bee!!!, infact it wont weld at all with the wire speed set at anything above 1/2 way. About 1/4 way seems the best for 1" box & 3mm plate.
hope this helps you , phil.

Have a look at the welding lead connectors,make sure they arnt burnt or getting hot,its usualy the earth clamp,also the lead that goes to the gun,make sure the current is getting to the welding wire,.6 mm i asume? .8 is too heavy

Cheers for the feedback, tried it on both slow & fast wire speeds, and yes its 0.6 wire. Will check all the connections again tomorrow, and then take it down the welding shop...

Before you take it back to the shop, reverse the polarity. You may have it set up for no gas welding. We had the very same problem with our SIP 105 turbo, welds looked like shit, reversed polarity, MK engineering, move over! (ok not quite).

Marcus

It's an old machine, can't be used for no gas welding, cheers anyway. Gonna take it down the welding shop in the morning, if it's shagged I'll just get a new one.

jasper when you do get going i noticed you mentioned Co2....use that for tacking up and you can weld with it if you wish, but for your final weld get your hands on some "argoshield" its a Co2 Argon mix, the welds will go down much neater and you will find welding with it easier too..."Argosheild Light" is the one i prefare......any others ????

Argoshield universal is another one we use, just depends on what the stockholder has in at the time, I can't tell the difference between that and light. BTW CO2 gives a very hot weld tending to burn through thin steel, spatters a lot too. Go for argoshield if you can.

Marcus

Cheers guys, will do. Ended up with an ex-demo Sealey 130 mig with a HUGE real of wire and gas for £100, very happy. Welding going fine so far, just tack welds, tho' I will get the argoshield, am I going to go through loads of little bottles? Renting a large bottle seems very expensive but may be better in the long run?

If you still have the knackered set I'll give you a tenner for it I could use some of the components to repair one of my old sets.

It's yours, are you local (brighton)? I want the wire and the new shroud and nozel I put on it, the rest is yours.

just for future info on possible MIG faults and solutions:
First of all I found my mig was trying to feed the wire but no wire was advancing, found that the wire had helical grooves on it which jammed in the tip - strpped out the tip, cut the offending piece of wire and got back to welding.
Second problem was that the quality of weld gradually decreased, thought it was me untill the motor stalled, if you turned the feed roller it would run again, basically the motor was nackered, so Clarke relieved me of £8 and £7 post packing & VAT and the welder works beautifully again.