The thickness range you plan on working within will should dictate the type of equipment. Anything under 1/2 inch should be a tiny-twin or single wire head with at least a 600 amp power source. Working in the usual range of 3/8 inch to 1 1/2 inches, a single wire head with a 600 to 1000 amp power source would do the job. If you're going into heavier plate fabrication, then a tandem-, triple- or double-tandem wire head arrangement with a larger power source would be required. Contact somebody like Lincoln Electric and their sales rep will bombard you with additional information.