Re: MIG upgrade, TIG or Oxy acetylene
Posted: Wed Feb 08, 2012 3:36 pm
Here's a word or two I wrote to Chris (Jury on here), when he was having welder issues, which were centred around the wire burning back inside the tip, but the principles are the same whatever the problem ...
"Anyway, as for the welder. The two main differences between the full pro-welders and the DIY ones are the wire feed mechanism, and the quality of the rectification to produce a nice DC. The DIY one's give a very iffy version of DC, which I gather if viewed on a 'scope look pretty messy. I've seen an old Sealey DIY MIG running on a couple of 12v batteries, and it ran rather nicely: true DC of course.
Anyway, the trick is of course to make the most of what you've got.
1) With the wire feed rollers loose, check by hand that the wire feeds very smoothly: sometimes the inner liner can be twisted or kinked within the outer. Also check the feed with the torch at various angles, just to make sure it's not kinking internally in some positions.
2) Change the tip regularly.
3) Make sure there's not too much tension at the reel end: on my Kemppi I modified it slightly to reduce the pre-tension. You want it just tight enough so that the reel doesn't run on (creating a slack bit of wire between the feed rollers and the reel itself), but not much more.
4) Roller tension: with everthing ready to go, hold the torch fairly gently around an inch or so from an object (ideally wooden, and certainly not earthed to the welder: you don't want an arc). Pull the trigger: you should have a small amount of pushback, but if it tries to shove your hand back, or it can buckle the wire, you've got too much tension. If you just get slipping straight away, you need a little more.
5) If all of the above, set up your wire-speed. With your power setting selected, start off with an obviously low wire speed: you'll almost have the wire tick, tick, ticking as it slowly feeds in, burns back, feeds in etc. Now in stages increase the wire feed bit by bit: you'll go through a smooth window where you're in the zone, and then back out the other side where you're clearly getting too much wire through: lots of noise and spatter, and the gun almost being pushed away. As you're getting burn-back, you want to have the feed slightly towards the upper end of the 'correct' feed window. This will give you a bit more grinding, but helps prevent the wire burning back.
I think that DIY machines can have times when they run really very well, but the difference is that the full pro ones need much more to be 'off' before they misbehave: i.e. the pro machines are much more forgiving. Like I say though, that doesn't mean you can't get good results with yours, you just need to take extra care over:
Wire condition (buy small reels, and keep spare ones indoors / in the warm and dry), rather than buy a 5KG or bigger: as soon as there's any roughness on the wire, it's had it.
Tip condition: change regularly, and before any really critical welds.
Don't run with the torch cable kinked around objects: work hard to get as smooth a route as possible.
Use big bottled gas (I think we've spoken about this before).
Roller tension.
I know what a right Royal PITA wire burnback is, but if you go through the above, it should help. The final thing is just to keep some tips in your pocket, with a small pair of pliers. That way you can just remove the fouled tip, swap it and carry on. When you're next at the bench you can sort out the blocked ones. Hopefully you'll avoid this if all goes well anyway .
All for now, and hope there's something in the above that may be of use!
Barry"
"Anyway, as for the welder. The two main differences between the full pro-welders and the DIY ones are the wire feed mechanism, and the quality of the rectification to produce a nice DC. The DIY one's give a very iffy version of DC, which I gather if viewed on a 'scope look pretty messy. I've seen an old Sealey DIY MIG running on a couple of 12v batteries, and it ran rather nicely: true DC of course.
Anyway, the trick is of course to make the most of what you've got.
1) With the wire feed rollers loose, check by hand that the wire feeds very smoothly: sometimes the inner liner can be twisted or kinked within the outer. Also check the feed with the torch at various angles, just to make sure it's not kinking internally in some positions.
2) Change the tip regularly.
3) Make sure there's not too much tension at the reel end: on my Kemppi I modified it slightly to reduce the pre-tension. You want it just tight enough so that the reel doesn't run on (creating a slack bit of wire between the feed rollers and the reel itself), but not much more.
4) Roller tension: with everthing ready to go, hold the torch fairly gently around an inch or so from an object (ideally wooden, and certainly not earthed to the welder: you don't want an arc). Pull the trigger: you should have a small amount of pushback, but if it tries to shove your hand back, or it can buckle the wire, you've got too much tension. If you just get slipping straight away, you need a little more.
5) If all of the above, set up your wire-speed. With your power setting selected, start off with an obviously low wire speed: you'll almost have the wire tick, tick, ticking as it slowly feeds in, burns back, feeds in etc. Now in stages increase the wire feed bit by bit: you'll go through a smooth window where you're in the zone, and then back out the other side where you're clearly getting too much wire through: lots of noise and spatter, and the gun almost being pushed away. As you're getting burn-back, you want to have the feed slightly towards the upper end of the 'correct' feed window. This will give you a bit more grinding, but helps prevent the wire burning back.
I think that DIY machines can have times when they run really very well, but the difference is that the full pro ones need much more to be 'off' before they misbehave: i.e. the pro machines are much more forgiving. Like I say though, that doesn't mean you can't get good results with yours, you just need to take extra care over:
Wire condition (buy small reels, and keep spare ones indoors / in the warm and dry), rather than buy a 5KG or bigger: as soon as there's any roughness on the wire, it's had it.
Tip condition: change regularly, and before any really critical welds.
Don't run with the torch cable kinked around objects: work hard to get as smooth a route as possible.
Use big bottled gas (I think we've spoken about this before).
Roller tension.
I know what a right Royal PITA wire burnback is, but if you go through the above, it should help. The final thing is just to keep some tips in your pocket, with a small pair of pliers. That way you can just remove the fouled tip, swap it and carry on. When you're next at the bench you can sort out the blocked ones. Hopefully you'll avoid this if all goes well anyway .
All for now, and hope there's something in the above that may be of use!
Barry"
