Curious

[Hemi]

Yesterday was the first chance i had to test my newly aquired secondhand mig, apart from a quick check that it actually worked when i picked it up. It`s a Clarke 130en, when i bought it the owner said that he had only used it 4 times and the condition supported that. When i went to change the wire to gasless, it had plain wire, an almost empty 5 kilo spool installed, i noticed that it was setup earth to +, does it actually matter which way round the terminals go ?

 

[malcolm]

For gasless wire the terminals should be earth positive, torch negative. For plain wire with shielding gas it's the opposite.

The polarity adjusts where the heat goes - into melting the wire or into the work. 2/3 of the heat is on the positive side (which is why gasless has better penetration than gas shielded).

 

[malcolm]

I'm perpetually confused by all this stuff no matter how many times it is explained to me.

Could you have a go at it, or point out exactly where I've gone wrong.

 

[Bsmith]

I'm perpetually confused by all this stuff no matter how many times it is explained to me.

Could you have a go at it, or point out exactly where I've gone wrong.

Hang on, I don't think its you thats confused its me!! I am thinking about arc welding where you get more (heat) penetration with the rod positive, I would have thought the torch positive with mig would be the same. My appologies. I should keep my opinions.

 

[malcolm]

There was a thread especially about polarity for arc welding in the past. http://www.mig-welding.co.uk/forum/showthread.php?t=10418 I think arc follows the same rules but you've got me confused again.

Geeze - soon as you think you've got something figured out.... They do say in that thread "oh no not again" and "it's complicated". I thing the same rules apply from other welders talking about using DCEN for the root in arc welding.

I'll have to try some more experiments myself. It's not like things don't work at all on the wrong polarity, only they don't necessarily work quite as intended.

 

[Bsmith]

I hav'nt only confused you Malc, scratching my head too. I'm amost sure what you said in that thread was correct DCEN for less penetration, it certainly works that way.
Someone suggests in the thread that mig is opposite, I never knew that and I have used the mig now for 20+ years, suppose its just that I never put my mind to the polarity as I never had need to.

 

[pidgeon chit welder]

I hav'nt only confused you Malc, scratching my head too. I'm amost sure what you said in that thread was correct DCEN for less penetration, it certainly works that way.
Someone suggests in the thread that mig is opposite, I never knew that and I have used the mig now for 20+ years, suppose its just that I never put my mind to the polarity as I never had need to.

Why not take apiccy of the setting on your machine and let us all see we can then print it off and when it is finally decided write on the picture what it finally turns out as.

 

[Omniata]

From my days in physics I think it works like this:

If the work is negative then there will be more "electrons" in the work undergoing resistance through the arc, so will heat the work more than the electrode...

If the electrode is negative then there will be more electrons in the electrode undergoing resistance, so thus heating it and melting it more rapidly than the work piece...


I think that's right based on what's been said...

 

[Hitch]

For most diy gasless, you need it setup DCEN, the wire on the - side, and the earth plugged into the +.

For normal gas shielded wire, you would setup DCEP. The wire on the +, and the earth as the -

The + side has more heat to it.

 

[Bsmith]

Why not take apiccy of the setting on your machine and let us all see we can then print it off and when it is finally decided write on the picture what it finally turns out as.

Now I'm totally

1 last go at it since I have already ruined Hemi's thread. apart from this I give up.
We have a dc arc welder, rod positive (+), its going to give a deeper penetration weld than with rod negative (-).
We have a flux cored mig, torch neg (-), its going to give a deeper penetration weld than a gas shielded mig with the torch positive (+).

Have I got it right

 

[malcolm]

Here's one from Al (FCV is flux core wire):

Malcolm
If you dont bother with the whys and wherefores

MMA
DC+ most common, best pen
DC- only when there is a chance of burn thro

MIG
DC+ always

TIG
DC- always
AC for Aluminium

FCW
DC- for gasless
DC+ for gas shielded

OK there are obscure applications that can prove me wrong but this fits 99% of the time.

 

[Bsmith]

Thanks very much Malcolm

 

[Hemi]

I`m sorry, didn`t mean to stir up a hornets` nest, i was just curious, the markings on the inside of the case were quite clear and it was set for gasless as per the accepted norm. I was wondering if the owner had used it to weld with plain wire without gas !!!!!!!!
I promise to shut up now

 

[malcolm]

It's got me thinking though - a good question.

You know how you go DCEP for your normal arc welding, but when you want a bit less penetration you reverse the polarity.

I've tried both polarities for gasless wire on thin steel. They both seemed to work for laying beads but I got disinterested after that. Didn't try a weld or check for slag inclusions or anything like that - I just gave the wire away to someone who likes slag and spatter.

I'm going to be controversial. People say always DCEN for gasless, but would there be any advantage in running DCEP with gasless wire if you wanted to botch up thin stuff out in the wind? Or, like with arc, would that make it worse?

 

[Bsmith]

I`m sorry, didn`t mean to stir up a hornets` nest, i was just curious, the markings on the inside of the case were quite clear and it was set for gasless as per the accepted norm. I was wondering if the owner had used it to weld with plain wire without gas !!!!!!!!
I promise to shut up now

Nooo no, You were right with your post. I promise not to interfere again unless I'm absolutely sure I know what I'm talking about.