What should I look for in a used welder on Facebook Marketplace/eBay?

[trif55]

My experience is limited to flux-core on a "Display4Top" which is a pain on thin metal - pics attached - about 1mm thick steel barrel - I had limited success doing very short bursts and combined with an offcut of the same material "welded" to the back I did briefly manage one short strip of reasonable (for me) bead in the middle of the only blue pic, I'd obvious combined and built up enough steel not to just blow through

As such I'm looking for a MIG welder that can go reasonably low current - I have a vague memory of MIG from tech class at school being fine on fairly thin wall box section and making a nice bead fairly easily? - A lot I see online are just like mine and only have 3 switches, "Power On", "Min/Max" and "1/2" I guess Min and 1 are the low power setting?

Such as Clarke MIG145 No-Gas MIG Welder - I assume I'll have the same issues as I do currently?

I have been offered this gas welder "Wolf MMA-MIG160 Combination Welder 40-155 Amps 230V + Holder, Clamp & Torch" but I'm not sure if 40A is what I want? or if it's a reasonable model?

 

[gaz1]

leave it alone

if your going to pick one pick clarks gas and gasless option

clarke 151 blue not the red as thats an extra 100.00 new price

as its best of both worlds gas and gasless

 

[trif55]

leave it alone

thanks, the Wolf is that?

edit: Ahhhhh I thought I'd seen a Clarke but it's a 145 gasless only, sad

 

[Macleesh]

Ask for a picture of the ratings marks, that should tell you the current range. Whilst its nice to have one that has a low bottom gear you may find you use it less than you think. Welding thin sheet is done in a series of bursts usually. My machine goes from 25-170A in 6 steps. I find butt welding sheet is best done on 2 or 3, setting one is too cold and leaves a proud bead with poor penetration. With good panel prep I can get a flattish bead with full penetration on 3 , nice and strong and much quicker to dress back.

I would focus on getting a machine with a good reliable consistent wire feed.

Good luck with the search, if you know what you are looking for there are occasional bargains on Farcebook/Ebay

 

[gaz1]

if you want to learn welding gas is the better option gasless is bright and you can burn through for fun with it sort like using an arc welder

with practice you can arc weld the same its just gas is much easier to weld thin stuff

 

[aesmith]

Check if you can see it working.

 

[trif55]

Check if you can see it working.

sound advice, thank you

if you want to learn welding gas is the better option gasless is bright and you can burn through for fun with it sort like using an arc welder

with practice you can arc weld the same its just gas is much easier to weld thin stuff

I can believe it's possible but difficult with gasless, esp as my wire feed seems poor & fast on this welder, for thin sheet do I want really slow feed and low power?

 

[Jelly_Sheffield]

I can believe it's possible but difficult with gasless, esp as my wire feed seems poor & fast on this welder, for thin sheet do I want really slow feed and low power?

MIG and FCAW-S (Gasless MIG) are constant voltage processes.

The wire feed rate, effectively sets the "power", because the welder varies the current as you weld, to match what is needed to melt the wire and maintain the arc.

You need enough wire feed to get a stable arc (i.e. not stuttering or letting the wire suddenly stick or burning back to the torch), which generates enough heat for the weld puddle to actually penetrate the parent metal.



When you set very a low wire feed rates, it becomes very difficult to maintain a stable arc, and even if you can the "arc length" gets increasingly short, so the likelihood of burn-back, and/or the wire sticking on the contact tip goes waaaay up.

In practice this means that for very thin metal, it's easiest to either:
1) weld in very short sections to control how much heat goes in to the workpiece.
2) use a thinner wire (0.6mm solid wire), so you can maintain a stable arc with lower overall power input.

For most non-production applications, approach 1 is generally preferable as it's easier to ensure you get proper penetration.



As an aside, it's a common mistake to treat the Voltage setting on the welder as a "power" setting.

Voltage controls how focused the arc is, higher voltage results in a longer arc length and wider weld puddle, which will technically increase how much heat you put into the part... But it won't necessarily be putting that extra heat in in a useful place.

So the voltage should be set to ensure the puddle is the correct width, enough to give adequate penetration (or leg length with a fillet weld) of the joint, but not so much that:
- it's melting more parent metal than necessary causing the weld sink in or sag down, or
- the arc becomes so violent that the puddle is being disrupted and isn't consistently tying in, or is undercutting at the edges.