Thermodynamics is releasing a new machine that is a MIG, TIG and Stick all in one compact box and its only $999 including the MIG and stick cables. TIG cable are extra. Played with it a little last week at a weld expo at my local welding supply place. Very nice, small and versatile. I want one.
Something like that would be ideal for and small workshop. The problem with choosing individual machines is that they have quite a lot of overlap so there isn't really any one 'best' solution.
As far as the individual processes are I would summarize them as follows :
Stick (MMA) :
-no gas bottle rental or refill to worry about, just electrodes and electricity
-good penetration even on greasy, rusty and dirty metal
-wide range of electrodes available
-good for thick sections
-machines tend to be inexpensive to buy
-can produce some interesting artistic effects
-good for building up sections quickly for repair and resurfacing etc
-good for outside and on-site work as teh shielding is less effected by wind and teh equipment tends to be samll and easy to move around.
-a fair degree of practice is required for positional welds, probably harder to learn than MIG
-struggles with thin sheet
-slag cleanup and changing electrodes can slow the process down a bit, although with practice this becomes much less of an issue.
-not so good for aluminium or stainless
-it can be hard to get neat welds without a fair bit or practice MIG (with gas shielding)
-easy to learn
-convenient to use
-easy tacking and gap/hole filling
-produces fairly neat welds
-good in all positions (flat, horizontal, vertical, overhead)
-requires gas bottle rental (gas tend to run out at inconvenient moments), if you don;t have a nearby supplier this can be a hassle.
-prone to cold starts
-limited control of weld appearance, especially with lower end machines
-machines are relatively bulkyMIG (flux cored wire / gassless)
-no gas to worry about
-wire is expensive
-welds tend not to be very pretty TIG
-High quality and good looking welds, in some cases welds can be virtually invisible when you know what you're doing
-excellent for thin sheet
-excellent control, especially with a foot pedal, this makes it ideal for welds with sharp changes of direction
-can weld thick to thin
-a machine with AC/DC output can weld most metals including bronze, a DC only machine will weld anything except aluminium and magnesium alloys
-TIG machines can also do stick welding
-machines are relatively expensive to buy
-a bit slow compared to MIG
-takes a while to learn
-requires gas supply (usually pure argon)
Uses bottled pure oxygen and a gaseous fuel (usually acetylene, sometimes propane or hydrogen), fuel and oxygen are mixed in a nozzle, producing a fine, high temperature flame. Filler metal comes from bare rods.
-Good control of weld puddle
-extremely versatile, can be used for welding brazing, soldering and general heating, with additional torch can also cut ferrous metals.
-Completely self contained and quite portable (depending on bottle size)
-Basic kit is relatively cheap to buy (excluding gas).
-Puts a lot of heat into the work
-Hazards associated with gas storage
-Bottle rental/refill costs
-Relatively expensive to run
-Not as economical as propane/air for general heating
-Tricky to learn