Arc welding 0.8mm sheet steel

[malcolm]

Transformer?????Inverter?????? aaaaaaaaaaaaargh!!!!
heh, AC/DC is a rock band right?
HELP!! can you explain the difference Shenion? pleeeaaaassse?

I'm sure Shenion did explain it a couple of threads ago. Working from memory -transformers are great heaps of copper wire wound around a big bit of steel. When the electricity goes backwards and forwards through the copper wire it makes a magnetic field in the bit of steel. If you wind another big coil of wire around the steel a different number of times it converts the magnetic field back into electricity but a different voltage as the number of turns is different. The switches on the front of the welder pick up at different points on the second coil, so you effectively change the number of windings and get different voltages out for each switch.

AC is what you get out of the mains supply. Electrons go backwards and forwards all the time. In DC the electrons go in one direction only. Better for welding unless you are messing with aluminium using a TIG set.

Invertor welders are made from magic. Lots of little electrical magic components inside do all the same stuff that transformer based welders do. They are a lot lighter and you can do anything with them, but there's more to go wrong as magic is so much more complicated.

Think that was the gist.

 

[Sparkey]

Heh, if you guys don't mind i'll just stick with the reply from SRG...




(yes, i'm a natural blonde...)

 

[Sparkey]

THANKYOU, MALC!!

 

[SRG WELDER]

Heh, if you guys don't mind i'll just stick with the reply from SRG...




(yes, i'm a natural blonde...)

Always keep things simple

Ste .

 

[Sparkey]

Yes, yes i know.....blonde and a welder too!

oh, sorry George.....for hijacking your thread...

 

[snowcat]

Sparkey, an inverter welder can weigh as little as 10 kilos or less, the equivalent transformer machine would probably be somewhere in the region of 20 kilos or more, they contain an awful lot of coiled wire rather than the inverter's electronics.

10KGs wozzz where you been dude, thats so yesterdays weight....

 

[Sparkey]

10KGs wozzz where you been dude, thats so yesterdays weight....

unlike some people, woz knows that we talk kilo's in france...(not pounds)

 

[shenion]

20 kilos?

Mine is 340 kilos

 

[mishka]

Hi,

Interesting thread.

For arc welding thin material I would suggest an older oil-cooled arc welder as they tend to offer higher OCV - for example my 'little' Oxford RT110 goes down to 20A at 80V, which I've used to weld 0.8mm steel quite easily without a heatsink.

Oh, and modern inverter welders are sometimes called 'handbag' welders

 

[dutchman]

Btw, if you are interested in some of the magic going on inside the box, you may like the Feynman lectures on quantum physics

http://www.vega.org.uk/video/subseries/8

Or these MIT lectures on electromagnetism

http://video.google.nl/videoplay?do...IOdSM2UN4eUjQKy7e3GDw&q=electricity+mit&hl=nl

Be warned, it could make your head hurt

 

[jugs]

Thanks Dutchy for those links, they look a lot more fun than whats on TV.

jugs

 

[GeorgeB]

For arc welding thin material I would suggest an older oil-cooled arc welder as they tend to offer higher OCV - for example my 'little' Oxford RT110 goes down to 20A at 80V, which I've used to weld 0.8mm steel quite easily without a heatsink

Thank you for the information on higher OCV. I'd already guessed that a higher voltage might be better (a) because my inverter has a higher OCV and (b) because my arc rods say they need a minimum of 50 volts whereas I think my Wolf arc welder provides only 44 volts. So my plan is to try and modify the Wolf arc welder from producing 40 amps at approx 40 volts. Instead, I hope to install an 'option' by which it will produce 20 amps at 80 volts, or higher currents up to about 70 amps by moving the shunt. If it works, I'll report back.

 

[mishka]

The higher OCV helps maintain the arc at low amps - the arc voltage should be roughly the same.

Modifying a transformer sounds tricky. They are loosely-coupled to allow the output volts to drop to abut 20-24 volts, relying on inductance to limit/control the arc current. If there's room you could try winding on more turns to the secondary - this would increase the OC volts, and increase the inductance so reducing the arc current. As a first step I'd wind on about 10-20 turns of small-gauge enameled copper wire to measure the volts/turn for your transformer. That will guide you as to how many high-current turns to add to reach the OCV you are aiming for.

As always, be very careful working on mains-powered equipment.

 

[GeorgeB]

If there's room you could try winding on more turns to the secondary - this would increase the OC volts, and increase the inductance so reducing the arc current.

Thank you again. I'm sure you know a fair amount more about this than I do, but it seems worth a try. You guessed correctly. I'm going to take secondary wire from another arc welder and use it to add extra windings to my main arc welder. There is plenty of spare space around the core. It's tempting to add a tap at the new joint, so I can return to the old range of currents if I need to, notably to get it to produce the stated maximum of 140 amps or whatever it is. Otherwise the maximum would presumably shrink to nearer 70 amps. But I know a tap, and the joint itself, will introduce ineffeciencies/distortions/ wobbles or whatever in the current flow. I hope such effects will be negligible and that I'll get away with it.

Overall, my primary objective is to reduce the current. The increase in OCV sort of comes as a free bonus from my point of view. I hope a higher OCV will make it even easier to strike the arc.

 

[jugs]

Is it possible to superimpose a HF or HV down the cable to help strike the arc ?

 

[GeorgeB]

Is it possible to superimpose a HF or HV down the cable to help strike the arc ?

I wondered that too! It must be possible. Does anyone know how? I have a spare ignition module (pizzo type) from a gas heater and wondered if I could somehow use that.

 

[JayRS4]

I believe not, hence the different modes on inverters for TIG and MMA, think it`s something to do with the flux on rods

 

[snowcat]

decent inverters run hot start features all ready, The "magic" in the box does this automatically, as well as being able to essentially change the OVC so cell, rods can be run(needing a very high OVC)...

This is just one of the many benefits of these machines, a 6013 is an easy striking rod, get into lo,his or even hardfaceing and they become a pig, hence oxford quasi having two voltage steps, as well as making striking easier for low amps.....

Now I'm not suggesting that you all go and spend £100s on an inverter, BUT I don't know a single professorial, welder, fabricator, or even maintenance technician, who wouldn't agree that the benefits of these machines, out way any negative points tenfold.....

 

[mishka]

Sorry for waking up an old thread, but this is a must:

Spell AC/DC

 

[dannyweld]

hi, some people call it fish scales, i think, the welds in the picture could have been done on a turn table. a continous smooth weld could be done if you speed up the process and turn up the amps. a lot of welds seen on say large motorbikes with that type of overlapping weld could also be robot spot mig, or even robot tig.