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What are you planning on welding? Some things are a lot easier than others.

If you want to weld stainless, for jewelry or armor, I can tell you how to build a spot welder out of a dead microwave or broken computer UPS (uninteruptable power supply) and less than ten bucks in copper, using only a hammer, angle grinder, and maybe a vice, and a couple hours of your time.

I'm not sure about welding aluminum, if you can spot weld it just the same.

For silver, it depends on what you want. You can fuse fine silver or Argentium silver, but not ordinary sterling silver. Fusing requires a small torch ($12). That's not too bad.

If you want to build a welder like the ones TRL sells, (should be able to weld just about anything), you'll need some low-ESR capacitors (can easily be salvaged, plain computer power supplies or old monitors or TVs), and some way to charge them to the voltage you want, (Ebay Variac, $15?), then you'll need some diodes to rectify it, ($1, or salvaged from anything), some tungsten needles ($3 for 20 at a welding store), and a suitably-sized SCR ($20, electronics supply or Ebay). You can maybe actually skip the SCR, I know Brian's method on his is to just bring the needle closer, and it'll fire when it's close enough to jump. I don't recommend it though.

I'm going with a DIY TIG setup, but that might be a bit more complicated and a bit harder to salvage parts for. That's because you'd probably need a timer, since it'll be too fast for you to reliably control by hand. It's peanuts in electronic parts, but if you don't have any to salvage from, actually going an ordering 1 part is as expensive as ordering 100 usually. But you could do that too, especially if you have a dead stereo.

Lots of options, but, you'll need to better describe your needs for it first.

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:eek::eek::eek:

I am looking to make durrable chain armor/armour. For jewlery I use other methods.

I have access to electronics scrap and other cheap supply stores. Although I know little about wiring I already have a voltage adjuster I made. Wiring and electronics: the next chapter in AP Physics class. :D

The prices you named are ridiculously cheap. Just what I need! (College is going to be expensive so I'm saving up.) I am not willing to dole out $750 for a welder so your methods sound fantastic.

I will be dealing almost exclusively with stainless steel. So This "If you want to build a welder like the ones TRL sells...." Is the method I would like assistance with.

You are more knolegeable about chain than anyone I have ever met. Your wealth of information is much appreciated.

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Personally I think a resistance welder is far better for armour than a cap discharge one. Do a search on welders in discussion and you should be able to find Cynake's instructions on how to build one out of an old microwave transformer.

:beer::beer:

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Ehn.. long post. Been meaning to type this up into an article eventually.. figured I'd write most of it now...

Wiring and electronics: the next chapter in AP Physics class. :D

Physics classes will only screw you over when it comes to electronics. The point where physics helps you is at a very deep understanding of it. A superficial high-school level grasp of physics will only be misleading when applied to electronics problem solving.

I will be dealing almost exclusively with stainless steel. So This "If you want to build a welder like the ones TRL sells...." Is the method I would like assistance with.

Okay. Can do. But I'm with Freyr on this, capacitive discharge welders are not very good for this situation. They have little control over variables.

A cap discharge works by charging up a capacitor of whatever size to a certain voltage, then disconnecting it from the power supply and shorting it across the ring. The usual method is that one lead connects to one of your pairs of pliers and grabs the ring, the other lead is a welding pencil with a tungsten tip. You bring the tip close to the place you want welded, then tap a tiny switch that triggers an SCR to close the welding circuit electronically. BLAM!

Zap%20Blast%201.jpg

An SCR is a one-way switch. When you trigger it, you can't shut it off. It only shuts off and resets when there's no more power. It's kind of like blowing apart a dam.

That means that the duration of the weld pulse is determined by how long it takes the capacitor to discharge. The amount of energy stored in a capacitor increases as per the voltage squared /2, I think. Basically, higher voltage means more quantity of electricity stored, waiting to be dumped.

However, since a capacitor basically has bottomless current available (it drains in milliseconds if not microseconds), the voltage determines how high the current is. The problem with this is that too high of voltage causes too high of a current which causes too high of heat. Too high of heat and it *blasts away* the material at the joint, vaporizes or otherwise explosively expels it, and doesn't weld at all. Like so:

Zap%20Blast%204.jpg

Here's a couple videos showing too much power, you can even see dents from where material was removed. Vid1, Vid2. (DivX codec required).

"So why not just lower the voltage?" you would then ask. Well, because voltage is your only way of determining how much charge is accumulated and how long the pulse is. Too high of voltage you'll have too high of current. Too low of voltage and you'll have too low of energy being discharged to weld.

The welder TRL sells, (and many similar) gets around this a bit, by having 6 capacitors which you can turn on or off with their own switch. It's a bit ghetto.. but at least it gives you some control over how *much* energy is being dumped, not just how high of voltage.

Another problem of capacitive discharge welding is the weld pulse is diminishing. It starts off high as there's high voltage, then drops quickly as the voltage decreases and the charge decreases. Having a steady pulse of whatever length isn't an option.

There are two basic kinds of capacitive discharge welders. Some weld using pressure and resistance (spot welding or resistance welding). These ones have two prongs or two points of firm contact before the SCR is triggered, and all the heat comes from high current (caused by the short circuit and near-zero resistance of the metal ring). The Sunstone single and dual-pulse welders are like that. They start at $2,400, go up to about $5000 + accessories.

The second type use a tungsten tip and only one solid point of contact. They require the voltage to be high enough to jump through the air. This is similar to TIG welding. The heat comes in part from the high current, but also from plasma arc in the air (in almost all types of welding, the arc does almost everything, the resistive portion is insignificant). This is what the Mini Pulse III that TRL sells does.

Oddly enough, both types use the same voltage ranges, as the same voltages are required to push the amount of required energy. The setup differs only in the physical tips. For ring welding, people usually have their preference either way.

For a schematic.. this one probably has an error, but gives you the basic idea for how the SCR is triggered, I drew it up a few years ago:

Cap%20Welder%20Schematic%203.gif

Looks more complicated than it is. On top is your charging circuit. Variac (for variable voltage), your rectifier (1 component, two input leads two output leads), then your capacitor bank. The lightbulb's there so that it doesn't blow your breaker trying to charge the capacitor bank instantly, to slow it down a touch. The circuit charges until you flick the switch to deactivate the charging and activate the timing circuit.

On the bottom is your triggering circuit. Just a generic low-voltage power supply (just about any wall-adapter from just about any old electronic device will be fine, plugged into the wall). All it does is charge a tiny capacitor that is going to fire the triggering pulse to the SCR, to have the SCR dump the capacitor bank's energy. You have a simple dual-pole switch to disconnect the timing cap from the low-voltage power supply so it doesn't short that into the weld too.

The basic operation is flick the big switch to charge it up, then flick it off, and tap the firing switch whenever you're ready.

Seriously, it's not a lot of parts. Here's what my temporary charging circuit looked like:

Zap%20At%2030V.jpg

Dead simple. The only two parts you'd need to buy are the Variac and the super-sized SCR (capable of several hundred amps momentary).

I know a handful of people who've built them without incident.

...

But, like I said, it's not the best option, especially for stainless, especially for armor-sized rings.

It's an old thread, with outdated methods, but this will give you the basic idea of how to make a spot welder out of a dead microwave in about an hour: http://www.theringlord.org/forum/showthread.php?t=35786

If you go that route, let me know, there's a far easier way to go about it than what I described if you have access to an angle grinder for 1 minute. Cheaper and quicker too if you have access to a blowtorch.

Here's a picture of my temp setup, with the weld "prongs", just edge-on sheets of copper, held on with clamps:

Spot%20Welder%2036.jpg

If you thought the cap discharge welder was simple, the spot welder has literally 1 part. Just a transformer. That's it. If you want to get all fancy, rather than a pushbutton to trigger it, you can build a timer for pretty cheap, using mostly components found already in your microwave. The timer is really simple too, maybe a dozen trivial components. Mine is a bit fancy and souped up, dialable from 10ms to 10s, in 10ms increments. It's been sitting on my desk incomplete for 2 months too. I should get to that.

...

If you don't have a dead microwave, but do have a junk Uninteruptable Power Supply, Anon designed a welding rig that uses one. He never wrote an article for it, but you can read about it and see pictures on this thread, (I start you on page 4, he starts near the bottom, and finishes on page 5).

He uses a 30A relay to trigger several thousand amps of weld current and somehow doesn't fry it... I recommend just making your own heavy-duty switch out of two pieces of copper.

Knuut, of http://weldedchainmail.com/ , 3rd (?) largest supplier of welded chainmaille in North America, uses a design very similar to Anon's. His welders are also battery-powered, because the electrical grid in Vietnam where his "factory" (inlaws) are is inconsistent. However, he uses precision timers to control the weld time, by using *massive* electronic switching components that can handle, oh, ten thousand amps momentary. As I understand, he got the components up on Ebay for cheap (only $100 each, a tiny fraction of their value). Probably overkill for you. If you're going to spend that kind of money you're better off just buying a small comercial spot welder since you don't live in Vietnam where you don't know from one day to the next if you'll have power.

One caution about using batteries to weld.. they sometimes explode when shorted. So, best to keep them inside a (vented) case of some sort, at least as a splash guard so you don't get acid all over yourself. Perhaps not too unsafe, as you're only welding moments now and then and the battery shouldn't ever get hot, but.. just FYI.

Anyway, there's more information than you asked for. I'd still recommend the microwave oven transformer spot welder. One thing I haven't mentioned yet is that spot welders do not need a shield gas because there is no plasma arc. With capacitive discharge welders, TIG welders, whatever else, you don't *need* a shield gas, but welds may come out dirty or ugly or poor without one, and gas setups (CO2, Argon, whatever) can't really be done on the cheap. You need tanks, you need regulators, you need to buy the gas, you need to design a way to trigger the gas release as the right moment. TRL sells their welders with and without gas setups, and it works okay without, but, just a heads up. It's a lot harder to get good results without shield gas.

But, let me know what you're interested in, I'll walk you through it. Chance of failure is practically zero, even for a complete beginner.

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Ehn.. long post. Been meaning to type this up into an article eventually.. figured I'd write most of it now...

But, let me know what you're interested in, I'll walk you through it. Chance of failure is practically zero, even for a complete beginner.

FYI I can't seem to post replies unless I get to the reply screen by clicking "Quote"

Makes it frusterating..... :sigh:

Anyway. I think that the Microwave welder is the way to go. I don't know about getting a battery though.... I would prefer a wall socket but the battery would me much more convenient for portability.

Right. Battery it is!

I await your words of instruction.

As a side note.... I wonder if an induction welder could be made....

Maby shape it like 2 almost-loops folded on top of each other to leave an opening. Something for you to think about.

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Anyway. I think that the Microwave welder is the way to go. I don't know about getting a battery though.... I would prefer a wall socket but the battery would me much more convenient for portability.

Well it's one or the other, not both. (Well, both if you want one of each, but, each setup is completely independent).

Microwave is much easier (and cheaper) to set up a timer for.

What you need now, is, a dead microwave, or, a dead (or functioning) sealed lead acid battery. A dead car battery (and charger) would work, but it's a bit overkill and a tad dangerous, so I'd see if you could call up computer recycler places and ask if they have dead UPS batteries. UPSs have to change batteries every few years, and they actually cost money to dispose of. But a battery that is "dead" for backup-power purposes, is still plenty fine for your purposes.

As a side note.... I wonder if an induction welder could be made....

Nope. I had someone do the math for me once. Aside from practical considerations (lack of control, precision, direction, likelihood of melting entire rings), just not feasible to get that much power into that small an area. Also, no reason to, far better options out there... and I say that having ~7 or so chainmail welding projects on the go, some of which I'm almost certain won't work. So, if I'm turning it down, trust me it won't work :P

...

So, go salvaging. Next step for you is find the biggest and heaviest and highest wattage microwave you can find. Don't pay for one, a broken one is fine. If you have a choice of several, (at the dump), grab them all, you can always use the parts for something else. 3 or 4 at least. One of them might come with a part that is most of the cost of a good timer. (Or, go find a UPS or UPS battery).

Next, you'll need something to make the secondary coil our of, and the tips out of. Copper pipe will work for both, though poorly. You want something a bit thicker if you can. It's gotta be copper.

I didn't have enough copper pipe, so I stuffed my copper pipe fill of copper wire, blowtorched it and packed it full of solder:

Spot%20Welder%2030.jpg

Then I cut away two 45' into each of them folded them, re-torched them:

Spot%20Welder%2033.jpg

Note that those aren't the prongs.. I just wanted a large surface area to bolt plates/tips onto. Before I bolted the plates on, it looked like this:

Spot%20Welder%2034.jpg

... so, more on how to do that later, but, just to give you an idea of how much copper you need. If you know how to do sand casting or anything like that you could even just scrap copper and cast your own shape.

If you can't afford copper wire or pipe (if you follow my previous link on how to build a spot welder, that stuff cost me $7 and was about half as much as I needed), you'll need to salvage some. Junked house wiring will be fine if you strip it. You might get away with using almost no copper wire, if you've got a blow torch. But more on that later.

Next, for either setup, you'll probably find it useful to have some longer heavy wire. And dead CRT (TV or old computer monitor) will have enough, so nab one of those if you can. The bigger the better.

Next, you'll need copper for the prongs. You'll have to design your own prong setup. Some people overlap their rings a touch, and then use actual spot welding prongs, with pressure, to squish them together. Freyr can tell you more about that setup, Knuut does the same. Some people just have a slot cut into two edge-on plates that you push the closed (no overlap) ring against. Anon used a copper heatsink plate (1/8" thick) for this.

I don't like the overlap idea. It's hard to control, and while it is surely the strongest weld (the weld area is thicker than anywhere else), it's ugly, hard to control, and hard to set up. If you want that, it's not hard to figure out later. I don't really like the idea of the edge-on contact either, because it doesn't give you a lot of surface area to contact the ring. My ideal clamping setup is something like this:

Spot%20Welder%2042.jpg

With the clamp either being flat, or, in a magical land where everything is perfect.. a differently sculpted clamp for every wire and ID:

Spot%20Welder%2037.gif

Anyway, if you can find a slab of copper to play around with, you're in luck.

Off the top of my head I can't think of anything else you need to get started. Everything else should come with whatever you salvage your battery or transformer out of.

Lemme know when you've got your parts ready for disassembly.

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"or, in a magical land where everything is perfect.. a differently sculpted clamp for every wire and ID:"

I live in this land..... Because I only need 1 size.

Don't have a torch... =S :sigh:

Ok I have my checklist. It will most likely take a long tome for me to get some more spare time (Scholarship season is in) though. Also I have to finish my ROV robot for the underwater submersible robotics comp as I am the club president. (I don't know how hydraulics systems work... I need to find out what to buy.)

Anyway, I will post back when I have the materials.

Thanks a ton!

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Microwave is much easier (and cheaper) to set up a timer for.

I don't know about that. A simple R-C timeing circuit will control a car battery and one of those big ass IGBTs I pointed you to on ebay (I just scored 2 more 600A units at US$49 each. Smaller ones in the 300 A range are going as low as US$25) with more than enough acuracy for welding. You realy should try one.

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I don't know about that. A simple R-C timeing circuit will control a car battery and one of those big ass IGBTs I pointed you to on ebay (I just scored 2 more 600A units at US$49 each. Smaller ones in the 300 A range are going as low as US$25) with more than enough acuracy for welding. You realy should try one.

Hrm. It's on my list :P

Any idea what you'd need for spot welding current handling ability at various wire thicknesses and materials? (I could extrapolate, I suppose, if it's linear by cross-section). I've never found this information anywhere, my equipment can't measure it (I can only guess), and it'd be nice to have available. Also, any idea how long "momentary" is, with that respect?

I know my spot welder is theoretically capable of 2,333 amps max, maybe more like, oh, 1,500 by the time losses are involved. For batteries, I imagine it has to be even higher (even a UPS battery, Anon was saying he had to add resistance, because the 1/4 second that it took the relay to operate was melting 16G stainless rings).

You should be able to get a TRIAC out of the same microwave you salvaged the switch from. I know ghetto is ghetto, but, for only $25.. an IGBT *is* looking pretty slick.

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It' not exactly liniar with size because smaller wires lose more heat faster to the electrodes. There is also a range of nealy two orders of magnitude between the resistance of some of the bronzes (60% of Ag) and some of the titanium alloys(0.2% of Ag.). Weld parameters must adjust over a fairly wide range.

I don't have anything like acurate ampearages either. My bigest welder is rated at 2500A max on a 10% duty cycle but I have never needed anything close to that. I usualy run off one of the lowest taps with relatively short weld times.

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It' not exactly liniar with size because smaller wires lose more heat faster to the electrodes.

Right right, but, I could at least approximate.

I don't have anything like acurate ampearages either.

Hrm. Well, I'll just have to hook up an input-side ammeter and do some testing with my MOT welder, get some specs out there.

My bigest welder is rated at 2500A max on a 10% duty cycle but I have never needed anything close to that. I usualy run off one of the lowest taps with relatively short weld times.

How important do you think it is to vary the the current available? Like.. other than for heat dispersion.. there is technically no difference between:

10,000A for 0.01 seconds, and

1,000A for 0.10 seconds.

So, other than timing precision, do you find there's a need to be able to adjust available current? Generally, a "fast", or "cool" weld is preferred, but, are there other considerations?

Would any of this change if not applied to a spot welder, just resistance welding, (since I'm not overlapping and won't have much clamp pressure, just contact pressure)?

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If you dont have SOME weld pressure you tend to get a lot of explosions. If your weld time is much shorter than the responce time of the mechanical componenets (inertia and all that other silly old fshioned Newtonian stuff), you get the same efect as not enough pressure. Remember, welding is primarily a mechanical process. Electricity is just another way to provide heat for that process.

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Well, I was hoping ring tension would suffice.

And, there are no mechanical components to my welder. All solid state. No relays.

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Well, I was hoping ring tension would suffice.

And, there are no mechanical components to my welder. All solid state. No relays.

Good luck! Do the math for the magnetic field in a droplet of liquid metal a 1/16 inch in diameter carying a current of a thousand amps or so. Pinch efect turns it into a mini rail gun aimed everywhere EXCEPT where the current is going!

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.... there are no mechanical components to my welder. All solid state. No relays.

Just an afterthought but the welding circuit itself is 3 (or more) simple but very massive NC switches in series. If they don't stay closed while the curent is on, you get a big bright splat.

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