Physical Arc Stability

The arc must burn calmly and evenly. If it flickers or becomes unstable, you don't have clean heat input, and that causes defects in the weld, like porosity or lack of fusion. The cause is usually the settings on the machine or the power source itself, not the 'coil'. Adjust the current to your material and electrode and keep a constant arc length. If that doesn't help, check the contacts and the ground connection—those are often the culprits.