Nelson,

Stay away from discount house TIG or plasma units, they'll only give you headaches. TIG is all about control, and cheap units don't have the fine control necessary to do precision work.

Since you want to work with copper, you're going to need a pretty robust TIG machine, on the order of 250-300 amps I'd guess. Copper takes a BUNCH of heat! All that heat into the work also means a lot of heat into the torch, which can result in operator discomfort and reduced life of consumables, so get the water-cooled TIG torch option. You'll be really glad you did.

Plasma cutting is a really filthy nasty process, generating fumes, dirt, dust, spatter and stink. It's best done over a water table or at least outdoors. You'll also need an air compressor, don't forget. Personally, unless I was going to drive the plasma torch with a CAD/CAM arrangement, I'd probably invest in a good bandsaw instead. More versatile and cleaner all the way around.

TIG welding is not particularly well suited to outdoor applications, due to problems with breezes blowing your shield gas away from the weld puddle. To TIHG welde outdoors, you need to rig a windbreak and you may need to increase your shield gas flow, too. TIG welders also work fine as stick welders, so I'd just use stick for outside work. The nice thing about TIG is that it is so clean you can do it right in milady's parlor without stinking up the place or burning the drapes with sputterballs. By comparison, MIG is a very messy process. With MIG though, you can switch to flux-cored wire for outside work, but not so with TIG.

For TIG welders, if money is not an issue, look at the Miller Dynasty inverter TIG units. The smaller ones will run on either 110v or 220v, making them really nice for installation work on-site, and they'repretty compact and lightweight. The bigger ones will handle the h igh current needs of working with copper and aluminum, but the water cooling tower will make them less portable. You can always get separate regular torch if you need portability, of course. If the Dynasty is a bit rich for your budget, look at the Synchrowave units. They're transformer units and pretty heavy, but rock solildly built. If you plan to ever do any aluminum welding, you must have a unit that has AC welding capability. Keep that in mind, as it changes the price considerably.

I've only mentioned MIller, but Lincoln also makes decent welders. Again, whichever one your local dealer supports is the one to get. Stay away from discount brands and big box stores! If you want to save money on the Miller or Lincoln, check out Indianapolis Oxygen Company. They sell on Ebay and have great prices and service. You can Google 'em. I've dealt with them and been very happy.

For a plasma cutter, stick with the big names like Hypertherm or Thermal Dynamics or Miller. Yep, they cost more than the cheapies, but they last a long time and you can always get parts and service down the road when you need them. The off brand units get orphaned at a depressingly rapid rate, leaving you high and dry. It just isn't worth it, in my opinion.

I hope this helps somewhat. Other will no doubt have differing opinions, so listen to everyone before you decide on a course of action.

A lot of good comments already.

I Tig quite a bit of copper, 0.043 inch thick (1 mm). I generally have my Synchrowave 180 welder set at 90 amps or so. Periodically I wish that I had a bigger welder, but I have yet to turn my current welder past 120 amps, so I don't need it. Somebody I know just picked up a Synchrowave 250, I had a little envy there, especially when he brought it to my shop to test it out. I assume that the amperage is more or less proportional to the thickness, so 5 mm copper would require perhaps 400 amps. Stainless requires less current, of course.

TIG and use outside are more or less incompatible, as has already been said. MIG, using a shielding gas, would be the same, I would think. The problem is the shielding gas blowing away, unless you have zero wind velocity, rare where I live. Stick and flux core are preferred if there is a breeze.

You may find a bit of a challenge welding rod to sheet, or at least I have in the past.

I would not totally discount MIG of copper, although I have never seen it done. The first google hit found Welding depot, which sells spools of 0.035 inch deoxidized copper wire. MIG welders are generally cheaper to buy than TIG welders, and of course much faster. TIG welds generally look nicer. Note that one reference I found said that 0.035 copper wire is generally used in the 145-185 amp range, 23 to 25 volts, 400 inches per minute, 30cfh argon, so forget 110V welders.

Before you invest in a welder, if you have a friend with a decent MIG, buy a spool of deox copper wire and give it a try. A little trial and error to dial in, but it should work. Obviously you would use pure argon gas, not the mix they use with steel.

I recently got a MIG, I may need to try copper with it sometime.

Richard

http://www.fergusonsculpture.com
Sculptures in copper and other metals