If you are working one of those under-powered 115VAC units (MIG), you must use at least a 50 AMP capacity extension cord. Ive seen guys get poor results, simply because their power input to these baby sized welding units, lacked sufficient amperage. Also make sure your 115 VAC source, is rated at a solid 30 amps or more, the better the input amps the better the heat will be.
If you are using a CO2 & Argon mix, sometimes straight argon will better lessen the dross, depending on the quality of your welding wire. MIG welding is an art form that has to be practiced for months until you develop the "feed feel" that stems from arm motion smoothness, correct amps settings, wire gauge diameter, feed speeds, and the particular material you are attempting to weld. Dont ever get stupid, and try to better your work by looking directly into the arc without proper eye shielding, you will only end up blind this way. Wear heavy gloves, and cover up your exposed body parts like your upper chest, as a tremendous amount of UV is released during the arcing. You will "sun burn" bad otherwize.....
dave....