Strictly discussion about electrical/electronic improvement to an existing MIG set.
The areas of discussion would be power supply smoothing (adding capacitors to a transformer based set) and improvements to wire feed speed controllers.
I work with arc lamp rectifiers a lot day to day, and the design of the average MIG welder is similar in some respects.
ie you've got a step down transformer, and a rectifier section.
Recently I had to do a wee repair to the torch wiring of my Sip MIG, and was both amazed and horrified to find that there are only 2 diodes in the rectifier section, and no smoothing capacitors. The 'DC' output must be helluva lumpy!
4 diodes would of course cost more to build, but increase efficiency in terms of output power versus current drawn from the mains. It would also give a smoother DC output, which surely can only be a good thing?
Now smoothing capacitors... Again, more expense. Much smoother DC output, and also significantly higher output for a given input, ie more efficiency!
I know this is an old thread , but I found it searching for summat else and it caught my attention.....
....how do 2 diodes make a rectifier ? I thought that 4 made a bridge rec and thats how you got the DC ....of course this may explain why the rectifier blew up over and over on the SIP machine I had years back . It wasnt a base level one , it was a big machine with timed stitch and spot and frilly bits and I wasnt conversant/didnt have the time viz a vis the workings back then .
Still , how does that work ? DC with 2 diodes ?
yes, the center tap on the transformer makes all the difference here.....
aditionally, most SIP/Cosmo also use a choke ..... this smooths surges in the current, thus semi negating the need for voltage smoothing.
if you do add capacitors, then of course the open voltage and thus the welding voltage goes up. if you dont do something about switching them out of the circuit, then you will suffer horrible burn backby simply adding a capacitor bank to them.
Actually the choke is needed not for voltage smoothing. It is needed for proper dip transfer. The arc voltage actually will exceed the supply voltage at times and will vary wildly. The choke increases the average current and adds "wetting" to the weld pool.
All decent MIGs will have the choke. Some chinese MIGs don't and they can't do a smooth bead and will spatter like crazy.
If you add capacitors, the voltage will go up. A smaller value like 1000-4700uf will make the arc more stable (must be before the choke.)