[djknight]

I have just "invested" in an otc welbee pulse mig after many years using a reliable transformer cv welder.
Lots of practice on the bench has yielded good results with the different types of pulse.but when I am fabricating
4-5 m long frames SOME of the welds are acting strange while I am laying them down,I would describe it as a pulse weld suddenly becoming dip transfer!
Gas is12%co2 (perhaps try 5%co2?)
The return lead has been moved around and all millscale removed,New contact tip,flush stick out ........
Would multiple return clamps help?
The welds themselves look ok
A little more spatter than in pulse but has a rusty coloured residue around the affected areas
Tried my supplier but they insist it's a "bad earth"
I am hoping I have overlooked something but having not been brought up with pulse ,I am not entirely sure
What!

[weldin mike 27]

Hey, if it only afects some of the welds its possibly could be "arc blow" caused by irregular magnetic fields in the structure. To combat this, put the earth as close to the weld as possible. Also wrap it around the member you are welding. If possible. Welding towards/ away from the earth could help. If its really bad, and starts trowing molten metal around, there are other tricks to tr .

Mick

[Superiorwelding]

Mick,
Not sure if I just didn't read your post right but you always want your ground clamp behind the direction of travel. In front can/will compound/create arc blow. I am not sure that is his problem though. Generally arc blow shows up at higher amperage and usually in a groove weld or corner or a joint, but not always.

Define "dip transfer" as I am not sure what you mean. I have a very good friend and mentor who works at OTC and he might be able to help but the first thing we need is a little more info. Would a pic of a effected weld help us? Being a new machine you should not be having problems. Generally when I am pulsing I use 90% argon/10%CO2. I know OTC machines will pretty much run on any gas and they claim to be very effective with CO2 as it is cheaper and readily available, especially across the pond (from us). The brown smoke usually means contaminates of some sort. It could be atmosphere being siphoned in, bad material or a number of other items. Can you provide us the specs you are welding at and your gas flow?
-Jonathan

[djknight]

Ok,
Pulse to me sounds a little like a massive bumble bee!
When my problem starts,it seems to revert to a bad weld setting with spatter flying around almost like what happens when you forget to turn the gas on! Although there is no visible porosity.
The pulse setting is 4.2 m/min wire(so approx 40x4.2=168 ipm?)
127amps 22.3 volts.
The material is your bog standard 100x50 rhs mild steel
Also if I switch to normal dc mode at
3.5 m/min
146 amp
17.9 volts
It runs fine
Gas flow at torch end is 13 lpm (0.8 to you I believe)
Thanks for the input
Regards

[weldin mike 27]

You read it right, Jono. I knew there was a correlation between direction and earth, but i couldnt remember what dirction....lol.

How ever, if you have lots of different members going around the area, arc blow could still be an issue, but im not sure why it would effect pulse and not normal mig.

Mick

[djknight]

Sorry forgot to add
1.2 mm wire
Doors shut
Also sometimes while tacking the problem happens
But not on the first tack but on later tacks when you would think that a decent return had been established
I will ponder some more!