AC vs DC Question

I have a Lincoln Weld-Pak 100 mig welder I have been using a couple of years and am now in the market for a stick box. I am trying to decide if I need an
AC/DC machine or just an AC buzz box. Would having DC capabilities be that beneficial for a part time home and farm welder? Any thoughts would be appreciated.
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Actually, having a DC-only machine would work even better. There are some inverter-technology power sources to be had which are fairly light (much lighter than a tombstone AC-only box).
On Wed, 10 Nov 2004 00:32:10 GMT, "John Craven"

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wrote:

The new small light efficient "inverter" welding machines inherently give DC output. It is expensive to make an inverter set give AC, as you have to do something complicated - which has no connection to the mains frequency (60Hz NAmerica, 50Hz rest-of-world).
In ye olde days of "iron and copper" welding machines, the cheapest, simplest and most robust ones were AC welding current *at the mains frequency*.
An inverter - to a good simplification, it rectifies the mains to DC, chops it up into a very high frequency AC (eg 20000Hz), which is put through the transformer (principle of physics - higher freq -> transformers can handle more current and become more efficient), then output is rectified back to DC - at which point is the easiest point from which to ship out welding current - hence inverter -> DC.
Hope my "explanation" OK with electrical and electronic folks.
Richard Smith
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wrote:

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Not an electronic folk but your explanation makes sense and I actually understand what you are saying. I can tell my welding teacher (40 year veteran) what they mean by inverter. I had asked him and he really didn't know the answer. I can say one thing from experience in class. The inverters kick ass and the ac dc tig boxes suck ass. Spent half the semester in one of the larger booths using a Miller syncrowave and having a very hard time, then went back to the small booth with the miller inverter and was amazed how much better they weld. I am comparing dc to dc here and I am a beginner. Thanks for the explanation on the inverter and sorry for the off topic ramble. Doug

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One thing to remembr about A/C is you totally get rid of arc blow using A/C.
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Since you have the low end Weld-Pac, I'll assume you are wondering about buying the 225 amp Linclon AC buzz box for $250 or the 225 amp AC/DC box for $350. Another response wandered off to talk about inverter welders, which are very nice and very expensive.
In the the low end boxes, the DC option is always nice, may not be necessary depending on what you are doing. There are some very nice rods (6011, 6013, and 7018AC) that run beautiful welds on AC. These same rods tend to run with less splatter on DC. And as soon as you need some of the other rods like 6010 (deep penetration root passes), hard surfacing, aluminum, etc you must have DC. http://www.mylincolnelectric.com/Catalog/consumableseries.asp?browse4|2030|Stick%20Electrodes%20-%20Mild%20and%20Low%20Alloy%20Steels&locale33
My home shop welders are an old 180 Emerson and a 225amp AirCo, both AC only. Plenty of tube bumpers and similar have come from those over the years. I'd like the DC but never really HAD to have it. I have access to a couple of nice MIG rigs and a 250 amp AC/DC box with wave shape options when I need it, I rarely bother to haul a project off to use these.
If it were me, I'd spend the money on the 225 amp AC only and the extra bucks on a good autodarkening helment.
cheers.
John Craven wrote:

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For what you describe, I second the recommendation to go with an AC machine. I have an ancient AC machine that welds sooooo smoothly -- when I took a class and finally had a chance to try welding with DC, I expected to see a huge difference, and I didn't. (Mind you, when I tried the AC setting on the welder at the school, there was a definite difference -- not nearly as smooth as my old monster at home.)
As Roy says, there are certain rods that you can't run with AC ... but so far I just haven't ever found a need to run them. I had planned to make a DC converter almost immediately after getting my old monster, but I just haven't had enough need. If I had DC, I would probably run 6010, but 6011 performs pretty similarly. I think I've seen a number of hardfacing rods that run on AC -- I might not be remembering that right, though, as I haven't yet had a reason to get any. (Someday I'll make that anvil ...!) I probably would have benefited from DC when I was having to weld some very thin tubing, but eventually I got the hang of it and was able to do a fairly decent job.
Hope you enjoy whatever you wind up with!
Andy

http://www.mylincolnelectric.com/Catalog/consumableseries.asp?browse4|2030|Stick%20Electrodes%20-%20Mild%20and%20Low%20Alloy%20Steels&locale33
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What exactly are the good and bad things about AC vs. DC?
I really appreciate all the good replies to my ac/dc question. Lots of folks seem to think that the AC buzzbox will work fine and that is definitely the least expensive option. Being a semi novice, as I see it AC and DC do about the same thing. Why do they make low end AC only or AC/DC boxes but not DC only? I guess one of my internal debates is that from my research it seems that DC gets better penetration, which I think is what I'm looking for.
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While I have been advised to buy a "name" brand welder i did come across this one that puts out 200 DC for $180. Anyone familiar with it? TIA http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumberD568

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Lousy duty cycle on the HF means it has small diameter wire inside. The equivilent Lincoln has 20% duty cyle at full rated output. The HF one has 15% duty cycle at half power. Wonder what it would be at full power? If you were to do any reasonable project with the HF unit you will be bumping up agianst the duty cycle, tripping the thermal cutout.
John Craven wrote:

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AC typically runs harsher and has more spatter than DC. Plus certain rods can only be run on DC. For hobbist use, you are unlikely to need the DC only rods very often.
Low end stick welders use a transformer which will give you AC only. Adding 4 big diodes will convert it to DC at some extra cost. Hence the lowest prices are AC only, next step up in price is AC/DC
I would NOT depend on DC for greater penetration. You need to think proper weld prep (clean, slight gap, V grove, etc) for getting good welds, not just turning it up to full heat and burning it in for "penetration" Granted, rods like 6010 have greater 'force' and are DC only but that is not the route to go.
John Craven wrote:

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My experience is limited, but not trivial. No commercial work, but 10 years of hobby work and a full year in welding school (nights).
The reason there is no low-end DC is because low-skilled people cannot/ will not/should not be using the rods that will need DC.
Sure, you can use 6011 at 150 amps to make welds through rust and paint, but why on earth would a novice want to do that? Can a novice do 6011 overhead? No way.
The novice, hobbist, and to a certain extent the pro, is better off making the joint clean, square, and flat and then running 6013. But the pro wants to save time and use his skill, so he runs 6011 with no prep, and still makes a serviceable weld.
6013 has been good to me lately. In my current project using 6013 on a $35 (yard sale) AC buzz box, I am in my 4th box of rods. With skill and practice you can make wonderful vertical-down welds very fast. With very little skill and a few minutes instruction the novice can make root-pass flat welds that are good. And slag clean-up is a breeze.

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As mentioned an AC welder is cheaper to make because a DC welder starts with an AC welder then adds 4 diodes and a choke/reactor and perhaps a couple of other components thus raising the cost. If you were to weld inside a steel box corner, residual magnetic fields in the steel may cause arc blow when using DC. AC doesn't have this problem so it can be handy to have AC as well as DC. Billh

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Bottom line is that you can't TIG weld with AC buzz box. If you want to TIG weld or try to TIG weld you'll need a new welding machine that has DC. If you are learning to weld with AC rods and plan on try it on job or shop you'll find a lot more DC welders than AC.
Your best buy is AC/DC or DC power source. A very good DC power is the Miller Maxstar 150s. The Maxstar 115vac/230vac, new price $585.
http://www.brwelder.com/indextemplate.cfm?file=shop/results.cfm&SubCategory=2

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It is certainly true that one can't TIG weld with an AC buzz box ... but then again, I don't recall that the OP was wanting/needing TIG capability. Meanwhile, one can't TIG weld with a DC arc welder either -- UNLESS one also buys a TIG torch, argon tank, and regulator. (And actually, I've always wondered -- could one TIG weld with an AC buzz box if one added an HF unit??)
In other words, even if you have DC, you're still going to be adding equipment and spending money to get TIG capability. And even when you do, you still won't have all of the TIG capability you might want (e.g., foot-pedal control, HF), unless you've bought a machine that already is set up with TIG in mind -- and that means even more money up front. Certainly, having DC is better than not having it ... but I personally would not spend the extra money to go from an AC-only buzz box (e.g., the Lincoln tombston) to the AC/DC version of that buzzbox if my primary goal was to have TIG capability. I'd still have a ways to go before I really have TIG capability ... and then I still won't have a foot-pedal, nor HF, nor any of the other useful things that might be found on a made-for-the-purpose TIG machine.
The Maxstar 150 is, by all accounts, a great machine, and some versions of it *are* set up for TIG, with torch, foot-pedal, and regulator (still have to buy/rent a tank) ... but *not* the one for $585. (The TIG welder version, the Maxstar 150 STH, is on sale for $1349 at the same dealer -- quite a difference in price!) If you buy the basic Maxstar 150s, you still don't have a TIG welder. And you don't have AC in case of arc blow, or for better aluminum TIG welding. And you don't have the extra amps that even a basic Lincoln tombstone would give you in case you want to weld up a battleship. (Okay, maybe that last one is a little unrealistic!) Note that you can get the Econotig, which provides both DC and AC TIG (and stick) capability, for $1299 at that same dealer. The Econotig does not have as good a low-end range as the Maxstar, but it does provide AC for better results on aluminum.
But that brings me back to the point: Is the OP wanting/ready to spend $1300 (actually more like $1500 by the time you add in the tank)? For what the OP is looking to do -- projects around the home/farm, IIRC -- I still think a basic 220v AC buzz box is a viable way to go. I especially think that if he looks around a bit for one at an estate sale or auction -- I picked up my old monster for $25, and recently helped a friend get one for $5 at an auction. (The nice thing about an AC buzz box is that there is very little to go wrong with them, so even the old ones can work perfectly well. I estimate that mine is 50 years old -- but it welds beautifully.) Even if you buy a new Lincoln tombstone, the cost is low enough ($230 or so) that it may be worthwhile to get a buzz box now to handle the mild steel farm/home repairs, and save up your money to get a really nice TIG machine down the road, when TIG becomes a desire or a necessity. That way you'll have the best of both worlds!
My $.02 ...

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"Would having DC capabilities be that beneficial for a part time home and farm welder? Any thoughts would be appreciated."
Any thoughts covers alot ground. I was just pointing out the lack of growth and limits of an AC only machine. You don't need to add HF or foot-pedal to TIG weld AL with DC. You can't weld with out electrodes, electrode holder, or other types of consumables, so whats your point. Don't be mad because you bought an A/C buzz box.

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Lance,
My apologies; I didn't intend to start something, nor did I mean to suggest that your comment was out of line. I certainly agree that DC does add some additional capability and potential for future growth. On re-reading my post, I realize that in trying to make my own point, I phrased my response far too much in terms of an attack on what you said. (I have to admit, I was not having a good day when I wrote that!)
I do stick by the positive parts of my input though -- my own opinion, for what it is worth, is that a hobbiest can easily do without DC, especially if cost is a factor. You are quite right that "any thoughts" means that cost is not the only factor that should be considered, and you were quite right to give a response accordingly. On the other hand, "would having DC capabilities be *that* beneficial" opens the door for weighing the cost-vs.-value equation. Certainly, different ones of us will weigh that equation differently, depending on our needs and resources. For me, a 220v AC-only machine gives far and away the best bang for the buck. To tell the truth, I kept expecting to wish for DC ... but I haven't ever found its absence to be a particularly limiting factor. Of course, that may just reflect the kinds of welding I do ...
I'm not mad -- the 220v, 275 amp AC buzz box that I bought is the best $25 I ever spent! :)
Andy

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