My old Sears 230 amp arc welder is AC output only. The DC welders I've used seemed like they have a more stable arc, easier to start and control. Is there a difference in general purpose welding with AC vs DC, or was I probably just experiencing a difference in brands?
I could probably put a big mother rectifier diode on it if it would give me any advantage.
Thanks.
sometimes it depends on what kind of rod you're using. an AC machine doesn't do so well w/ a 6010 (DC+ rod only). in place of 6010 you should use 6011. 7018 runs on DC+ or AC. I think 6013 (a sheetmetal rod) runs on DC+ or AC. even so, I know what you're talking about...I've tried running 7018 on AC and it seemed like it wasn't penetrating as much (as I suspected) and it was harder to start. I'm not an electrician, but a diode might solve your problem too.
Actually, for best results you need 4 diodes to form a bridge, a choke (inductor, reactor, stabilizer are some other names for it) and possibly some sort of transient suppression like MOV and capacitors.
It can be done if you know a bit about it. If you are good scrounger you can do it cheaply. High current diodes are expensive but surplus stores can save you a lot, dumps even more. You can parallel lower current diodes but this has to be done with care to balance the load so you don't pop the diodes one after the other.
Im guessing the old sears unit did not have good ocv. Open Circuit Voltage. A miller sales guy told me higher ocv gives better starts with less sticking. Id guess that a rectifier is not going to improve ocv. Does anyone know?
The rectifier won't increase the OCV and in fact it will probably drop it by a couple of volts due to the loss through the diodes.
On the other hand, having DC instead of AC, especially if there is a choke in the system so the current doesn't go to zero, may improve the sticking problem.
I am not an experienced welder so take this part with a bit of caution. I understand current can be cut back 10-15% typically when using DC so there must be something to it not sticking as readily. My experience after converting my old Miller AC buzzbox was that sticking was less of a problem but my welding suffers from a lot of other variables so I can't be sure it was the DC doing it!
You can easily measure the OCV if you have an AC voltmeter. Just turn the welder on and measure the AC voltage at the end of the cables with no arc being drawn. My Miller is about 80V on the low current range and 55V on the high current range. I understand 80 is the maximum permitted OCV voltage for a welder due to shock hazard.
I have an owners manual for a Sears AC/DC welder and it says that the OCV is 71 on the low current range and 44 on the high range. That really isn't too bad at all; but yours may be different.
Leaving this electrical stuff out, what kind of rod are you using? As a newbie I found on AC 6011 and 7018 drove me nuts. I had a lot of sticking problems with the 6011. 7014 and 6013 were a joy to start and run a smooth bead for me. There is 7018 and 7018AC, I think mine was the DC one since it was hard to strike and it would burn well up inside the flux and I had to break it to restrike. When I ran it on DC it was just fine.
Bill
The welder I have says 80 volts open circuit. I used to do 6011 with it because that's what they recommended. Good penetration, but lots of spatter and a real drag to control the arc. The amps scales on the machine are calibrated for 6011 and 7014. Is 7014 what they called "contact rod", where the rod kinda burns inside the flux?
I don't know if you know it, but 6011 is run a bit differently from 7018. 7018 is a "fill-freeze" rod...you just drag or weave to create the desired bead and it will fill an area fast and will freeze in place so you can weld in all positions. 6011 is a "fast-freeze" rod...mostly used for places where you want deep penetration, and quickly. it'll freeze in place and will weld in any position or direction. with this you have to start the arc, build up a puddle, and then whip the rod away from the puddle in the direction you intend to make a bead. the distance of whip is only about 1 1/2 rod widths. then you move the rod back where you came from about 1 rod width. always keep the arc length short and a lot of the spatter won't be quite as bad.
Yes, 7014 is called a drag rod since you can just let it rest on its flux and drag it along the joint. Seems a lot of people don't like it because the flux is very smokey when it burns. Apparently it was one of the family of rods made so inexperienced welders could make ships in WW2. You don't have to drag it.
You mentioned the 6011 and 7014 settings on your machine. Get some info from your rod manufacturer or just look on Lincoln's site on what they recommend and try different current values. Nobody trusts the dials on old buzzboxes for current settings. If you have been using the 6011 setting then increase the current about 10A or so and try that. Low current is a cause for sticking on startup but you don't want to set it so high that the weld suffers.
There is a rough rule of thumb: when in doubt, try the rod diameter in thousandths for the initial current setting. So 1/8"=0.125" or 125A
3/32"=0.094" or 94A
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