Convert Your AC Stick Welder to DC - For better welds?

[wB8FUW]

Here are some pictures of my lincoln being converted.
http://picasaweb.google.com/111615940997608812749/WelderImages#

[John K5PRO]

I was just talking to an expert welder at work a week ago, and he said they use AC only for ____ metal and DC only for _____. The two words are steel and aluminum, but i cannot remember which was for which. Maybe someone else has experience here?
John

[W2PFY]

This looks like a way back machine with the original post from 2005. Lincoln made the same unit with ac or dc, perhaps an upgrade could be ordered from them?

[wB8FUW]

http://picasaweb.google.com/111615940997608812749/WelderImages#

 Check out my lincoln coversion project.   It is completed, but still testing it.  My open voltage is high using capacitors, even before the reactor coil.  I may have to remove them and just use the reactor coil for dc smoothing of arc.  I may try putting a ac capacitor on the primary of the welder to improve the power factor.  Stick starts good with the high voltage of 115 volts DC instead of 80 volts ac I had to start with.   But that is in the danger range for shocks.  Even 80 volts can bite in the right conditions.



 

Tom,

Like you I have a Lincoln 225 amp AC stick welder, it does a great job and even today is pretty cheap ($250 at Home Depot). Never had any of my welds break so it does the job for most stuff a non pro needs. However my welds never look as good as those pictures you see in welding books where the weld looks looks like coins laid on top of each other sideways with next to no splatter.

When we took a drilling rig to Turkey we had a new Onan generator/DC welder for the rig since we had to fabricate and repair our own stuff. Not cheap at 3K but when I first used it I couldn't believe it. My welds looked like the ones in those books. Basically I just did what I do with the AC welder but the welds look great and next to no splatter. DC holds a better and more uniform arc, and it's easier to do than AC welding. I was using 6013 sticks like I do for most stuff. I heard that reversing the polarity is useful for welding upside down, but I've never tried that.

Anyway going to DC will sure make your welds look better and with less skill than running AC. It's worth a try if you have some big rectifiers around. I think Lincoln's AC/DC stick (225/125) runs $450, so they are charging $200 for the rectifiers to get DC.

73

Marty WB2RJR

[Opcom]

the inductor helps stabilize the arc for DC.

[W2PFY]

many dc welders of the day had a device called a droop. It was a strip of bi metal of some sort that was about 1 inch wide and about 12 inches long folded back back to meet itself to another terminal and was in series with the positive cable. It really didn't matter what polarity it was in as long as it was above ground. When you struck an arc, the droop would take the surge and then the governor would pick up to meet the demand. That's how I recall it was done on motor driven welders and the same principal may have been used on rectifier types.

Is there anyone else out there who can shed some arc on this??

[WA2IXP]

  I've had a bit of experience with welders having used and repaired quite a few. Some of this info may have been already posted as I haven't read the entire thread.   Transformer operated ones use a bridge rectifier for d.c., no caps needed. Some controlled the current with a tapped inductor and a single winding on the transformer. Others used tapped transformers.  Some used aluminum windings. Smaller modern  motor driven units use alternator and bridge. Larger liquid cooled machines were and still are d.c. generators with tapped series field coils as well as a field reostat (or electronics) for current control. The generators work the best. Cost the most.
  D.C. works best for most work. Nessasary for aluminum stick welding. Stick welding of aluminum is difficult. MIG or TIG is much prefered. Of course this requires a costant voltage supply and more costly equipment. Also MORE EYE PROTECTION.
  Some times on D.C. you'll get arc blow or pulling caused by magnetic fields in work. Corners and tight places. Move ground clamp. Positive goes to ground. Called straight polarity. Reversed is neg ground.
  Tom, your conversion should work ok.  I don't think the caps will make a difference and as you mentioned will raise the  open circuit voltage higher than nessasary.
  For general purpose work on steel the a.c. is ok. Once you've used a good dc machine you won't use a.c. much. The output current will be lower due to the increased losses in the diodes. Just my thoughts, Jay-

[Opcom]

here is a fun intermission. An inverter welder was thrown in the trash. It was later fished out and sat in a barn for 5-6 years and someone had taken the case to use as a stool. I was shown it after we had been using Pabst Blue Ribbon and eating pizza at 2 AM in Illinois. It is a 208V 3-ph unit. The other guys did not know anything aboiut electricity so I had a free hand. It is amazing what you can get away with when no one else knows much about electricity. We cobbled it to a 240V single phase outlet and discovering mud dauber nests on the circuit board. removed it and chipped off the huge nests with a screwdriver, and using a wire brush and plenty of brake cleaner, polished up up nicely. Behold it worked, but not as expected. We waited for it to might blow up nicely, from the sounds it was making. There was a burnt resistor we could not tell what it was, maybe that is the problem.

http://www.bunkerofdoom.com/travel/ss2009/8109_build/fun/100_8622.mov (large file, best to download)

[Ed/KB1HYS]

I picked up a couple of welders from the dump. Someone cut off the power cords and chucked them (really).   One is an old Monkey Wards AC welder fairly large, 220 volt in-- I think its 190amp(?) out don't remember, it is big enough to weld anything I have around here, including automotive frames.
It has a big aluminum wired transformer with a sliding core current control and cooling fan. I cleaned it up and wired a dryer socket for it. Works pissa. I made a set of cables from jumper cables, and bought the electro and ground clamp at the local Homedespot. So far so good.

The same day I picked up a 110v sears "buzz box"  tapped transformer type.  Haven't messed with that one, Looks ok but is pretty rusted up. needs a good cleaning before I fire it up and I haven't had time to mess with it yet.  Besides, the montgomery wards job works fb.

[KL7OF]

Tom...  Have you tried "Jet Rod" (7024) with your AC buzz box? It works best for flat welds (horizontal) really a bitch to weld vertical and almost impossible to weld overhead with...But in the flat it really makes beautiful welds that are strong...It has iron powder in the flux and you can let the rod rest right on the work as you weld....Great for smalljobs tht can be positioned in the flat...

[Opcom]

That's what I got, the Sears 100A buzz box. Has a multi-turn knob on it but nothing else, no meters, all hard-wired, etc.. Would it be worth it to try and give it a DC option? Kind of smallish on the amperage for the pros but more than big enough for what I ever do. What would I really notice when welding steel with DC vs AC on such an inexpensive box?

No complaints about my welder once I seen what other have.

[VE7 Kilohertz]

I sure hope it's okay to resurrect a 7 year old thread  , but this was a great discussion and I am interested in doing this conversion to my Linde 295AC welder.

Tom, did you ever complete your conversion and how did it work out? Did you use an inductor?

I have access to the large diodes, massive rectifiers from locomotives, and should be able to come up with the inductors, if need be.

Has anyone else made the conversion and what parts did you use?  Does it need to be a bridge configuration or can you just use one big rectifier in the stinger lead, ie half wave rectifier?

Thanks

Paul

[K1JJ]

Tom, did you ever complete your conversion and how did it work out? Did you use an inductor?

Thanks
Paul

Hi Paul,

No, I never did follow up on it. I still use the straight AC arc welder.  However, if I still did a lot of welding, I would try that diode/ inductor DC idea.  There's no doubt it will give cleaner welds.

The next step up would be a MIG system that uses a shielding gas for even cleaner welds.

I even rented out a TIG welder once for aluminum work. It was as easy and beautiful as soldering - and as simple too.  We get what we pay for.

T

[Opcom]

Guys, what is the right welder to use if one is not highly skilled and wants to weld 8" diameter patches of steel over some holes in steel? All the steel is about 1/32" thick, or a little less. Does not have to be pretty just keep rain out, and will be covered with roll-on pickup truck bed liner.

[K3YA]

Guys, what is the right welder to use if one is not highly skilled and wants to weld 8" diameter patches of steel over some holes in steel? All the steel is about 1/32" thick, or a little less. Does not have to be pretty just keep rain out, and will be covered with roll-on pickup truck bed liner.

Pop-Rivets

Or a wire fed MIG, thin wire , turned down real low.  Hard to weld such thin steel.

[K1JJ]

Guys, what is the right welder to use if one is not highly skilled and wants to weld 8" diameter patches of steel over some holes in steel? All the steel is about 1/32" thick, or a little less. Does not have to be pretty just keep rain out, and will be covered with roll-on pickup truck bed liner.

If practical for the job, cut the 1/8" plates to size, clean surfaces well and then glue them on with a large bead of PVC.  Once dried, it should be pretty strong and waterproof.

T

[WBear2GCR]

You can braze with gas (oxy/acetylene)...

               _-_-bear