Murex Tradesmig 251

[Weldingartisan]

simondrains
Don't know about the 251 Tradesman but my 320 Eland has 24 steps. Saturday is generally my 'play and maintenance' day down the workshop, so I'll try the low settings with a volt/ammeter and report back. The Kemppi shows all parameters on a lcd screen which is useful.

 

[malcolm]

can you or (anybody else) explain the relevance, if any, of minimum current output on a MIG set? As you say, a WPS has a voltage only and that as we know is because a MIG is a constant voltage machine.

Me me! Unless I have bitten from the wrong end of the stick in which case someone else please!

OK - Power is what melts the metal, and volts x amps = power. For tinny metal the power needs to be way down else holes are blown.

The power controls on a MIG alter the voltage. It's fixed voltage only for each power setting. Your actual amps are influenced by the wire diameter and speed, which is why 0.6mm wire running really slow is so good for welding Renaults.

The really technical stuff might need to come from someone else.

 

[malcolm]

Just noticed today feed roller wrong fer the wire (0.8). Its a 0.6 and 0.8 roller. Put in the wrong way round. still worked tho!

I've been known to do the same - ran 0.8mm wire through a 0.6 roller for about 10 years. Worked OK.

 

[Drains]

Me me! Unless I have bitten from the wrong end of the stick in which case someone else please!

OK - Power is what melts the metal, and volts x amps = power. For tinny metal the power needs to be way down else holes are blown.

The power controls on a MIG alter the voltage. It's fixed voltage only for each power setting. Your actual amps are influenced by the wire diameter and speed, which is why 0.6mm wire running really slow is so good for welding Renaults.

The really technical stuff might need to come from someone else.

Thanks for trying Malcolm, but akshally, I think ( I'm probably wrong), it's amps that do the melting, volts that sustain the arc. Which explains your next point re 0.6mm wire - fewer amps required to melt.
So again, does the minimum amps output have anything to do with anything, or is it irrelevant? Should MIG machines also have a quoted minimum and maximum OCV?

BTW Weldingartisan, I have an NBC 300A set with 32 settings! So Ner!
It also has volt and ammeters, which I will also examine, and report back with details...

And welderpaul, you should be able to weld fag papers with that thing!

 

[Welderpaul]

Si,

I'm trying to weld 2.5 box with 0.8mm wire, with adjusting the settings i'm either blowing holes or just resting a bead of weld on the surface. there doesn't seem to be a happy medium at the low end. (at the high end it's a top bit of kit) gonna have a go with 0.6 wire to see what that does for me.
What do you think?
Curse the mig!!. Where's me rods!!....

 

[Drains]

Might be a dodgy machine. Theres a thread here somewhere about the very same problem. It was suspected dodgy diodes but the lad never got back with results... Hmm.
Highwaystar might help. In that earlier thread he suggested testing the diodes, but you need to disconnect one end of each or you get a wrong reading. And they should all read the same on the open side.

But trying the .6 wire sounds like a good start. I dont get the blowing holes or no penetration at all, whatsoever thing.

I can understand how annoying it must be. I get the same with MMA - It's quicker for me to haul a big 300A set across the yard, plug in the wire feed unit, stick a bottle on a trolley and plug that in, go and fetch and fit a 15kg wire reel, and drag 100m of 3 ph power lead, all to do a couple of inches of weld by mig than it is to set up a little MMA unit and weld, grind, weld grind etc etc until its right! (At least it was until I did some practice. Ahem)

Oh, and weldequip might have an idea or two up his sleeve...

 

[Welderpaul]

Only dodgy welder is me!! - It's new(ish) so it should be ok! (He says, trying to totally disregard the suggestion that 700 quids worth of bright red welder could be faulty in any way!)
It's a time thing with me, I try and stick weld everthing, only time the mig comes trundling out is when its something that's got a good ten metres of weld or so to do.

 

[weldequip]

It's OCV that determines how smooth the arc is & how thin the material it will weld; back to my original post about the Tradesmig 251 having a minimum of 40amps & the Tradesmig 140 having just 5 amps less at 35amps, yet being much more suitable to thin sheet welding (and MIG brazing) because it has a lower OCV than the 251.
3 Phase machines do tend to run smoother than single phase, so that could explain weldingartisan's Eland 320 being better on thin stuff than the Transmig 110, but I'll bet the Eland has a lower OCV than the Transmig 110.
weldequip

 

[snowcat]

ey up.

What is the lowest amperage my Murex Tradesmig 251 will go down to? and what is the thinest section steel it will weld? Instruction manual long disapeared under inches of grime int workshop!
I seem to be blowing holes in 2.5mm wall box. Don't know how you boys get on welding thin stuff on cars! - I am afraid, tasked with fixing car panels, it would be an overlap joint and a nice line of pop rivets! But thats why i'm not allowed near cars!

No manual, Murex have fantastic support, all there machines have there manuals (past and present) in pdf format on there web site, or give them a ring , they have even given me mobile no.s of service techs in the field who can tell you anything about there machines.

 

[weldequip]

Si,

I'm trying to weld 2.5 box with 0.8mm wire

It should p*** that Paul, hardly thin sheet; when the lads on here talk about thin sheet they mean 0.8mm!
Are you using it on the very bottom setting? In which case switching to 0.6mm wire would cure the burn-through problem.
weldequip

 

[Welderpaul]

Thanks snowcat, i found it the other niight, nice to see they offer a service like that.

 

[malcolm]

it's amps that do the melting, volts that sustain the arc.

Naah - it's the power that does the melting, or strictly energy. Using science as a crutch here - power = energy/time. Heating stuff and transition between phases (melting) takes a certain amount of energy.

Get the point about volts though - nessessary for the arc to do the jumpy thing. Amps I guess are a necessary evil.

 

[Drains]

Only dodgy welder is me!! - It's new(ish) so it should be ok! (He says, trying to totally disregard the suggestion that 700 quids worth of bright red welder could be faulty in any way!)
It's a time thing with me, I try and stick weld everthing, only time the mig comes trundling out is when its something that's got a good ten metres of weld or so to do.

Time thing with me too - hence quicker to drag sets, bottles etc etc. I told you I cant stick weld for toffee. And you spent 700 quid? I don't know what to say mate.

Weldequips thing about 1ph vs 3ph is definitely true. Smoother on 3 by far - much easier to rectify. To be honest I don't know how these machines work, all I know is that little SIPs are difficult to use, big 1phasers are ok, and big 3 phase jobbies are really easy.

Keep at it mate, hope it sorts itself out. It's a bugger though. To me, welding 2.5 stock should be a walk in the park - as it would to you on another machine, I suspect!

 

[Drains]

Naah - it's the power that does the melting, or strictly energy. Using science as a crutch here - power = energy/time. Heating stuff and transition between phases (melting) takes a certain amount of energy.

Get the point about volts though - nessessary for the arc to do the jumpy thing. Amps I guess are a necessary evil.

I need to go back to school.


Paul. Try messing about with your tip to work distance. Get a blow holes setting and pull back a bit. See what happens.

 

[Welderpaul]

Si - Aye, the thing is tho, one job and it's paid for itself. That is something i count meself lucky on!
Weldequip - Lowest setting = kack weld; Next setting up = oohhh i can see inside the box section. - So it's me then?

 

[Welderpaul]

And while i'm on, just had a look on esab site for a manual for that old horse of a thing i was wittering on about t'other week. There aint one - typical. Does anyone know where i can get a manual for a Esab LHE260. I think Noah welded up his arc with it..

 

[Drains]

Si - Aye, the thing is tho, one job and it's paid for itself. That is something i count meself lucky on!

Best logic in the world!

Deffo 0.6 mm wire for you btw

 

[Drains]

Howdy folks. Had a look at the volt and ammeters on the NBC 300 today. Open circuit voltages from 12v to 42V in 32 1v (ish) steps.
So I put it onto the lowest setting and fired away on a bit of hidden steel. The amps went from under 100 with a big standoff to over 200 with the tip close up!

I did the same on high volts and got the same result!

The only thing I can derive from this is that, up to a point, the current rating is irrelevant. Not really understanding how MIGs work, I can't take it further than that. I don't understand the relationship between wire size and stickout, voltage, current, weld size, and the design of the machine.

I imagine a higher power machine, eg 500A can also work at a higher voltage, eg more than the 42v my 300A machine does.

I also imagine that the minimum amps makes no odds to anything, it's the minimum volts that matters.

Anyone want to tell me what the hell i'm talking about?

 

[weldequip]

Open circuit voltages from 12v to 42V in 32 1v (ish) steps.

Is that just the calibration on the meter or did you actually get readings at those figures?
weldequip

 

[Drains]

Hey Weldequip.
Those were the readings off the voltmeter and ammeter on the machine - thats OCV when not welding (switching in contactor without activating torch), and when welding. However i'm guessing about the steps - sorry, very unscientific. I assumed 1v steps, which may well be incorrect! Anyway, it is 32 steps, whatever.