Welding conundrum

[Ahdammit]

I'm restoring an old car.Most of the time now when I'm welding,it's like the current isnt working properly.The weld has no penetration and the wire pushes back the gun.
I've checked the feed roller tension and I'm wire brushing and/or flap wheeling the metal,but it's still doing it.

I'm a bit lost.Should I use a chemical degreaser or something as well?
I had no trouble earlier in the project,everything was welding nicely so I dont think it's anything I'm doing,I'm open to all suggestions/help.

Cheers

John

 

[gavuk]

Try the welder off the car ,to make sure welder is ok,on new metal if possible ,if it works ok check your earth on car ,a bad earth can display the problems you describe,a good bare metal contact is needed on the earth lead or weld a tag of new steel to the car ,closer you are welding the better.....

 

[michael1703]

if no penetration and pushing the torch away then the power is too low and the wire feed is too high

are you using 0.6 or 0.8 wire?

0.6 is better for car bodywork

 

[Ahdammit]

Thanks lads,
Gav,it's doing it both on the car and at the bench.I've had the clamp right next to the workpiece and it still does it.
Metal is clean and bright and well clamped together.
Michael,I'm using both 0.6 and 0.8.I've tried altering both wire feed and current settings,within reason,no dice.

It's almost like the wire is pulsing or something,though it seems to feed all right when the trigger is pulled.
I've taken out the liner and cleaned it,it looks ok.

I'll keep at it.

 

[BillJ]

Worth a look inside to check all connections are tight and there is no sign of any of them having got hot. Mains disconnected first, of course...

 

[Justme]

Check the earth lead at the welder end.

 

[rikrobson]

Check that the open voltage is correct. measure the voltage between the tip and the earth clamp and check it is stable. Should be around the 20V mark depending on the settings. disable the wirefeed 1st to stop it feeding when testing.

 

[michael1703]

sounds like tensioners could cause it too, slip n grip would cause the feed to be a bit pulse like

not only do you have tension at the rollers but also at the wire spool

turn the gas off, with the machine switched on and side cover removed, pull trigger and watch the wire feed through, you dont have to cut the wire youve just fed through, just loosen the tensioner and wind it back on to the spool

make sure it flows nicely and doesnt try to over run when you let go of the button, make sure the wire is coming off the drum from above and not below also

 

[Ahdammit]

Thanks for all the advice,it's much appreciated.
I've tried it again and checked over the things I could think of,so I'm just reading the comments above now.What I checked was-
Feed rollers-the wire spools out smoothly when the trigger is depressed(not welding,just pulling the trigger)
I took the liner out again,blew it through with some wd40 in it,no appreciable dirt,some small flecks of metal.No damage visible.
New tip fitted,I had one spare.
When I try to weld,sometimes I get a nice tack,good penetration and a nice noise.
However,sometimes,I get a kind of mild bang bang bang,no penetration at all and a kind of jagged blob just lying on the surface.The wire feels as if it's kind of pushed back towards the gun slightly then melts on the surface.

Sorry for the poor description.

I'll be back down at the shed tomorrow and I'll investigate all of the suggestions above.
Again,many thanks

John

 

[mike os]

what machine & gasless or gas welding?

 

[Ahdammit]

It's a Portamig 185 and the gas is Coogas from Air Products.

 

[mike os]

first guess would be voltage up or feed down..... maybe a touch more tension on the feed

also... silly Q but you have got the gas on and set to about 10l/m? and have gas at the torch?

try on some 2-3mm mild steel until you get a feel for the welder settings

(personally I would try & run a weld on the earth clamp... but I'm known to be naughty)

 

[metalspanner]

I was having similar problems, with the portamig 185 (automig) that I recently obtained via fleabay, brand new liner etc, etc and it was stop start, spluttering and banging.
The wire would feed and stop and all sorts of aggro, it had me stumped for a while, till I decided to take the drive feed roller off and clean out the groove, not much muck in it really, replaced it and still slighty hesitant, till I played around with the wire feed tension and I heard what could only be described as a satisfying pop as the wire slid into the groove and no more problems.
Didnt post the first welds with the new welder, as they were done on a scrap bit of 25x25 box section without gas just to test her out.

 

[chap]

You may want to blow the liner through with some solvent to clean out the wd40.
Does sound like an earthing problem from my experience.

 

[malcolm]

I had a similar sounding problem caused by a batch of poorly made 0.6mm tips which would grip on the wire as soon as they got hot. Try a 0.8mm tip with 0.6mm wire to rule that one out. Maake aure you have the right feed roller grove - the roller is reversible.

Is there any rust on the wire? That wouldn't help - if there is rust a new reel or wind any rusty stuff out, give the rollers a clean and new liner.

Worth making sure everything is clean and you have a good earth connection (the clamp might need a wire brush to clear off rubbish).

Is the gas Cougar 5? If it was pure CO2 it would do what you describe on the lowest 2 settings but would be OK (if a bit spattery) on higher settings. It wouldn't be the first time a bottle had the wrong gas in it. Does the machine work on higher settings (and thicker sheet)?

Worth posting some pictures of the bad welds so we can see better what's happening.

 

[malcolm]

till I played around with the wire feed tension and I heard what could only be described as a satisfying pop as the wire slid into the groove and no more problems.

Same thing just happened to me. The wire speed was very inconsistent after changing to stainless wire. I thought the wire was lined up with the feed roller but obviously it wasn't - putting the slightest resistance on the reel would make the rollers slip.

Held the wire in the grove when locking down the top roll and all was sorted - back to normal again - good pull from the rollers and nice consistent welding again.

Did you get yours sorted Addammit?

 

[Ahdammit]

Sorry for the late reply,the computer had a fit.

I've tried everything I can think of,but it's still doing it.
The liner is thoroughly cleaned,I've wound off a lot of wire to ensure that it's clean and fresh,I've made sure the steel is properly cleaned.I've cleaned off the earth clamp and made sure I've got a good connection.Changed between 0.6 and 0.8 wire,no difference.
I'm stumped.

I'll try to define better what's happening
Pull the trigger,for about 5 seconds,it welds nicely.
After that,it's goes bang bang bang,spatter everywhere.
Stop,move slightly and it welds fine for 5 seconds or so,then same again.

I hope the machine is ok,I'm not even 1/3 of the way into my first reel of wire.

I'll get hold of a camera this weekend.

Thanks for all the advice so far,bloody thing's getting me down.

John

 

[Marty2005]

If it's ok for a few seconds and then starts playing up I wonder if you need a new tip. A knackered tip can 'grab' the wire when it gets hot. This would explain why you get a few seconds of good weld i.e. the tip hasn't yet got hot.

 

[Ahdammit]

Thanks Marty,I'll use yours and Malcolms tip from above and try a 0.8 tip with 0.6 wire tomorrow and see how I get on.

 

[Ahdammit]

Well,down the shed today and I decided to check the earth in the machine in case that was the problem.
I took off the cover and to my surprise,I found the blue wire from the power cable has come off.
The cable seems to have been assembled with insufficient slack,there's a clear witness mark where the bulkhead fitting was,I had to loosen the bulkhead fitting and bring the cable through about 3/4" to give it a little slack.

The big question-will this have damaged the machine?
I tried welding again,but there seems little or no difference.