Mark @ Everlast,
This question is for you.
I have an old Lincoln AC 225 welder. I keep reading about DC welders and how people say that once you've used one, you'll almost never use/need AC again.
It was free, so I can't complain; however, what kind of cost is one looking at to "eat the greener grass of DC"? What size and voltage will be able to handle any sanely sized projects I might undertake? Are used one easily found and if so what does one look for as warning signs it's been used and abused?
Thanks for your 2 cents on this.
Big Wave,
There is a lot of difference in the welding arc and the quality of weld. The DC arc is generally more soft and stable. Until you weld with DC you don't know what you are missing.
Having DC means that the AC is converted into DC if it isn't a brush type generator, either powered by an electric motor or engine. The brush type generators are known to be the best of the best, and most of them are quite old now...Because it is expensive to manufacture and all the welding mfg'rs have figured out that they last indefinitely and that pinches their pocket book.
Enter Buzzbox welders with AC/DC current. These use the AC to convert to DC with rectifiers. They are usually much lower output on DC than AC, because of the conversion process. Duty cycles are not great either on the low end welders.
Lifespan is decent if they are handled and used correctly. But they offer little flexibility and are heavy to carry around and guzzle electricity.
Enter DC Inverters. I have talked to a lot of people about this, since this is what I sell. Many guys have still never welded with one. But the way the inverter is able to handle certain welding situations adds a different feel to the arc. Inverters are capable of "tuning" the arc because the arc is electronically generated. With DC transformer welders, as the arc gets tighter, the voltage drops and the overall watts required to burn the rod drops so the rods can stick. This requires a longer arc. The arc voltage then comes up and the watts increases....The problem with this is that longer arcs in some situations, especially out of position welds are not desirable because of weld contamination and lack of control of the arc, and mainly a stuck rod.
IF an inverter is so equipped, like the Everlast, the unit has arc force control. This, in the simplest terms, boosts the amps as the arc length shrinks....and the voltage begins to drop. The increase in amps is done synergically, in relation to the the arc length. This helps to maintain overall wattage and keeps the rod burning, even if it is held directly in the puddle. This means that the welder can be run at lower amps and it can offer a more controllable puddle, as the unit compensates to keep the rod burning even if it seems a little cold. This also helps prevent the formation of heat affected zones while welding, by running cooler.
Not all inverters have arc force control, but this is a definite advantage.
Inverters also can boost the starting ability of the rods with a "hot start" feature which sends an extra surge of current when the arc is struck preventing the sticking of the rod to the metal. There again, not all have it.
But even without the arc force control and hot start, the DC inverter can be made to mimic the old brush machines, where as the cheaper transformer DC machines are not as stable or as robust... Their DC arc is still better than any AC arc though.
The lifespan of inverters have been in question, thanks to early inferior designs. But with the addition of soft switch technology which makes the part of the welder that creates the arc last much longer. These parts that make the welding arc are called transistors..They are classified as IGBT or MOSFET. The IGBT's are the quarter horses of transistors, while the Mosfets are the thorough breds. Most welding companies have chosen IGBT's because of their ability to be abused, though they aren't quite as nimble. MOSFET units tend to be extremely lightweight, in comparison to equivalent IGBT units that I have found. They weld great, but I have seen, especially with the imported welders issues with the MOSFETS durability. But current IGBT's all seem to be fairing much better in dire conditions.
I don't guess I have directly answered your questions yet, but I wanted to give some very broad background.
The DC welders are more...but the price is across the board.. Our DC inverter is 350.00, other brands for similar level of performance are over 1000.00. But to get the best range of performance, I think you will need about 200 amps, but you could survive with 160 which would allow 5/32 rods.
