Proper polarity
 

I checked the Lincoln manual online and found that flux core wire feeders requires that the electrode be negative so..

Flux Core Welding
Electrode - Negative
Ground clamp - Positive.

Good luck.

This agrees with Domino11's info as well...

Possibly silly to some, but also there are those that really enjoy the construction part of the mechmate and I see from the threads that there are some that build more than one or plan to make more than one. IMHO if it is just one build why even purchase a welder in the first place? Just have it welded by someone who has the proper equipment?

Flux core is definately not the easiest to learn, but would be okay for the base table channel welds, if you were using the flux core in a larger size such as a 250amp. ;) (kiss)

I think when most were talking about the flux cored mig welder though, they were probably looking at a typical welder like this:
http://www.mylincolnelectric.com/Cat...t.aspx?p=59618
Which is what they sell at Home Depot and Lowe's.

Although the output range is 30-140 amps, take a look at the welder specifications near the bottom of the page,
it is 20% duty cycle,19.5volts,90amps. Okay.......that is not enough, 7" channel is 1/2" thick in the corners. You will have what looks kindof like a weld on the surface but the base metal will not get hot enough for even a minimal passing weld. Also at 20% duty cycle that is 1 minute of weld and 4 minutes of rest for the machine. (when I welded my table I used a 250amp Mig welder set at 25.5v and 260ipm wire feed rate) That is about 30% more than the max. capacity of the above listed welder.

I only chimmed in on this thread hoping to give back some knowledge, because I really apreciate all the shared knowledge here, hope I didn't offend anyone.:):)
To me a tool like a welder, air compressor, drill press, ect. ect. should be purchased with a mindset that it is an investment. I was taught by my father and always have firmly believed that with tools don't skimp......you get what you pay for. Why else would we be building the best cnc router?????:):)

Ed,

Very well said!

Those who have access to Craigslist:

http://www.craigslist.org/about/sites.html

Have an endless supply of used welders in the tools section. You can buy a used Miller, use it at your leisure, then sell it and get your money back.

But I bet you will keep it after seeing how handy it is.

When I was searching the internet I came across this MIG DIY Guide that maybe of some use for other people.

http://www.mig-welding.co.uk/

now for my 2 cents those of you that are new to welding i have one thing to say :D Practice you will have scrap metal fron cutting your parts so throw it up on the binch and practiece change the settings on the welder which ever you use and run flat beads until you get an acceptable weld then put 2 pieces together and weld them put them in the vice and try to break the weld if it is a good bead with good penitration it will bread the metal next to the bead then cool your weld down a little your making the metal brittle but above all practice practice practice

Wow. So my LincolnElectric 140amp MIG isn't going to cut it?!?! If thats the case my girlfriend is going to be pissed seeing that she bought that for me for xmas. I havent even got to use it yet.

I saw that DC stick welders 200amp+ cost in the thousands! Is this correct or am I not looking at the right welders? Can anyone reccomend a good stick welder for a decent price? I need to be able to weld atleast 1/4" steel.

I saw the Miller welders and they are like 2000 - 3000+. Thats crazy. Should I try and sell my 140amp and get a stick welder?!?!?

Your MIG should should be fine. Just use proper set up....If memory serves me right, that MIG is rated for upto 3/16" plate @ 20% duty cycle. You'll be fine. Just follow the directions.
Sean

I agree with ED in that a baby MIG welder is not going to be happy, particularly for welding onto the MM's main beams. The spec sheet for the baby Lincoln says: "MIG weld 24 gauge up to 10 gauge (.135") sheet metal in a single pass. Weld up to 5/16" steel using self-shielded Lincoln Innershield® wire (FCAW-S)."

So if I use the selfshielded I should be fine??? You know what im just goign to look for a used stick welder then. What amperage should I stay above to weld through 1/4" without problem. Im not about to halfa$$ this machine together.

For a stick welder, 140 Amp will manage.

Charles,
You could always weld together the leg sections and then bolt them to the main beam, therefore saving you the welding on that heavy channel. This has been done by many others for the sake of dismantling and transport possibilities. I think even some of Gerald's new tables are done this way from the pictures I have seen. :)

Our new tables have bolted cross-supports, but the legs and 2 other uprights are welded under the beam. The beam ends are also welded closed.

That 140 amp Mig will be fine. I have a 135 Miller and have built great projects with it. http://www.cnczone.com/forums/showpo...&postcount=239 (Yes ugly but strong) .

I also built several trailers with that unit that have been abused (Over Loaded) by their owners and they have held up to that abuse well.

So I think your GF did good and you should be able the build with that unit.

I too think you'll be fine with that MIG if you are using flux core wire. I have a 135 amp Lincoln and I weld 1/4" steel with it all the time. The duty cycle is low when you're at the highest amperage setting so you might have to let it cool every once in a while but that's okay. Plus, MIG welding is much easier to learn than stick welding.

It is simple enough to do a quick test on scrap to see if the welder will do it. Lay a 3/8" plate on the bench, stand a 1/4" vertically up, weld together, hammer the 1/4" till it bends over 90 dgrees without breaking off.

Will do:) But I am going to have to wait to do this though. The house in which my girlfriend and I are renting is not a good place for this kind of stuff. I would rather wait till I get my house with a garage.

We have actually been loking but have had ZERO luck. . . . . . .
Rest of this post copied to a new thread here:

Using Oxy-Acetylene Process to Build MechMate
 

Greetings,

This site has got me planning/dreaming about building a MechMate here in the Pacific Northwest of Canada.

I have an oxy-acetylene welding system and was wondering if one could use this process to build a MechMate? I see no mention of anyone doing this or suggesting this earlier in this thread. While I am not an expert welder, I have some experience making fairly decent welds with material up to 1/4" thick mild steel. To join thinner materials to thicker heavier beams I have often found braze welding to be easier. Would braze welding be acceptable in this application?

Thanks,
Doug

I think Gas welding of the parts would be fine. Very Strong in fact. Done correctly gas welding makes better (prettier) welds anyway. This process is used to build aircraft.

Heat control is always an issue even im MIG or TIG.

I don't think Braze welding will be strong enough. You need fully welded joints to support the rack and torque this unit makes.

Oxy-Acetyl Welding with a brass rod would not be strong enough for the table, but instead of using a brass rod, you can use a steel rod with flux and that will be stronger.

If price is an issue, usually ARC welders like the 225 Lincolns you can probable find a used one cheap. They can make a pretty weld with deep pentetration with some practice.

Mig welding, if it has enough amps can make a good strong weld with flux, Non flux welding makes the pretties weld, but has less strength. If I was using a mig then I would not use flux core wire, just solid wire with argon mix.

Just my thoughts.

Oxy-acetylene welding will be quite okay. None of the welds needed on the MechMate are critical - all of the welds are fairly low stress.

Selecting a good arc weld electrode for the Mechmate

6013 for the Y-Car
7018 for the table

A good read in spanish and read in english.

The 7018 (iron powder coated) sticks need quite a high Amperage and you seldom see them used by a DIY guy with a small welding machine.

If Gas welding is acceptable then brazing is strong enough. Alot of race car, racing karts, and racing bicycles have been brazed with good success. Brazing has a higher tensile strength than steel, 120000 - 130000 psi. The joints need to be fitted nearly perfect, as it does have strength in gap filling properties

Maybe its time for a new welder... With one of these babys everyone can weld like pro :)

Have it ever cross you mind that hiring a professional welder (person not machine) for a day? This would clear one hurdle of your build.

Sorry, Ken, I don't see your point.... ;)

You don't have to weld it yourself if you know you are not up to it. Hiring or ask a favor from someone who can weld better the me when its call for goes a long way for me.

My scenario.
I only have stick welder (borrowed). I know my welding skill is not up to par. BUT sufficient for horizontal welds & enough to keep the metal sticking together, (ugly but that still get the job done :o). I also know I can fit fairly well & I don't trust contractors to pay as much attention to fitting as I wish. So, I build the table top side down to eliminate overhead welding, Fit the gantry & Y-car as best as I could then did all the spot weld & haul the lot to a welding shop with MIG facility to finish off the full welds under my own supervision (make sure the welding sequence is followed) this cost me peanuts when consider the outlay for a MIG welder & hiring CO2 just for this job not forgetting that the weld quality is guaranteed.

In fact my total outlay for the welding
~US10 welding rods, with 75% left over
~US20 welding fee (for a familiar face :) )for 1/2 hour job.
~ 1 big favor to a friend who borrow his truck for sending the Gantry to the welding shop.

Compare to ~USD600 (this is cheapest local price for MIG) US30 hiring+deposit of CO2 cylinder, +XX for consumable...

BUT you can also hire a pro welding person or get a friend to do the welding with your equipment.

Acquiring new skill would be nice, but it depends on if it is your objective.

Michel, you will get used to welding after just a few inches. It`s not that hard, just a little bit of training.

Ken, I think you wrote this in another thread: " ...You only need that "can-do" attitude...":)
and like Gerals said: ...Welds don't have to be beautyful, they have to be strong...
I used only stick welding on my MM, and allthough I`m not a welder, everything went smooth and now I can weld.:)

can not agree more. :)

Not forgetting, there are more then one way to skin the cat. :)

I sell weldings alloys for a living, we have rods you can use without hoovering over the piece, you press the rod at the piece and it opens the arc, you keep pushing the rod at 45deg to the juncture and it keeps welding and the welds are pro-like.

The rods I sell are expensive, but what I learned from this technique is that you can do the same with brand name 6013 rods, these are cheap, just put 10A more than usual to the machine and try it on some scrap metal

Pablo, are those the rods with iron in the flux? (we call them "iron powder" rods)
That type of rod, and most others, need to be "fresh", or baked dry, before using them.

I also used the 6013. I also read this welding guide which was posted in some other thread. It helped a lot finding a good technique.

Gerald, that sounds like a pain for the DIY guy who will have rods sitting around in the garage for while before he needs them. What will happen if you use the rods after they have sat in the garage for a while without baking them? This is one of the reasons I went for a MIG welder initially.

I have a metal box that I keep my rods in... Inside is a 40 wat light bulb that burns 100% of the time. It keeps the moisture out and the rods baked and ready. I have both a mig and a stick welder... Different jobs need different equipment...

6013 is general electrode I use. It is the most common electrode used here. They are almost impossible to go wrong when welding structural or mild steel. Some times we also use them for pressurized vessels/pipes.
Even I can weld with these :)
Moist electrode... Its best to store them in sealed boxes or containers if you know you are going to stow them away for a long period, I personally like common plastic food containers. I've seen ppl storing theirs in large coffee cans.
But if you have a pack of damped electrodes, 2 ways, 1st the pro method, use drying oven, 2nd layman method, stick the electrode to ground for a few second until you see the electrode stats to glow... but there a limit to this recovory, if they are wet, I suggest to discard them.
I know this because I do need to supervise steel fabrication from time to time, I know how things are done & what should happen but don't have to do the muscle work... Yes, I'm that PITA guy who only know how to point his fingers :D

No, they aren't, and most of the product line repels moisture so they can be stored without much care. Brand name is Magna (www.magnagroup.com or my site www.peu.net) These are specialty rods for maintenance, not the usual alloys used in the industry, for example we have an electrode that can weld almost all steels, yeah, that include inox, low-med-high carbon steel, manganese steels, spring steel, etc etc, you have to see it to believe it.

Regarding keeping the electrodes moisture free, I also use the method described above, a wooden box with a 40w lamp inside does wonders to keep them in usable conditions for a looong time.
Unless you live in a place with high moisture all year round, 6013 is very forgiving, but there are others, for example aluminum rods, that degrade pretty fast due to moisture.
Also 6013 is cheap enough to discard if it looks degraded, but as I said, they are forgiving, keeping them in the box they came closed should keep them usable for a long time.

Then there is the issue of the welding machine you use, most common type is the AC transformer, a bit more difficult to the novice, but not that difficult either. The next type is the inverter, little machines that weight nothing compared to a transformer and have many advantages over them, for example, they stop current flow when your rod sticks, preventing overheating, the current flow is smoother and most of them also can be used as TIG welders (TIG is almost the same technique as MIG) and did I mention they are light? for example I have an ESAB Caddy, a 150A machine that can weld at 100A with 100% duty cycle and it weights less than 3kg (7lbs)

quote "(TIG is almost the same technique as MIG)"

This is a very misleading statement, especially since there are beginner welders here that might be confused.

guys guys, not trying to confuse anyone, I said almost!, both methods use Inert Gas to protect the area to be welded, both methods are electric, one has a wire feeder and the other is feed by the welding person, even can be used without consumables.
For the novice, ARC is the method of choice, you can do some nice welds without spending months to learn the technique.

Pablo, As a welder I understood what you where getting at, I think you should of used the word "process" instead of "technique". Technique infers physical manipulation in some way.

The TIG process is similar to Oxy/Fuel in technique. Novice/hobbiest tend to think more in the technique frame of mind instead of the process mindset.

I am just trying to keep the novices on the straight and narrow as there is a lot of confusing and conflicting information out there.