Dross
What is the primary mechanism that creates dross?
Molten metal is generated in the kerf, but the gas jet fails to eject all of it before it resolidifies on the cut edge.
How do you distinguish low-speed from high-speed dross?
Low-speed dross is usually thick and bubbly; high-speed dross is typically a harder, thinner bead or glob that is more tenaciously attached.
What is the fastest shop-floor correction sequence?
Verify the correct cut chart, inspect nozzle/tip wear, confirm gas pressure and purity, then adjust speed and torch height in small increments while test-cutting.
Dross is re-solidified molten metal that remains attached to a cut edge when thermal cutting processes like CNC plasma or fiber laser fail to fully eject melt from the kerf. Also called slag or spatter, it is the most common cut-quality defect in plasma cutting, appearing as low-speed, high-speed, or top-surface contamination.
In a fabrication shop, dross is not just a cosmetic nuisance; it signals the cut process is out of balance. During setup, an operator validates material thickness, amperage, gas pressure, standoff height, and consumable wear. They then run test cuts and examine bottom edges. If thick, bubbly dross appears, travel speed is usually too slow; if a hard bead forms, speed is too fast or height is off. The efficient goal is not absolute zero residue but a condition where slag falls off or comes off with a light scrape. Production cells frequently tune by small speed increments and torch-height corrections before releasing parts. In stainless, assist-gas purity is critical. Beyond slowing deburring, heavy dross can force grinding that disturbs edge geometry and welding fit-up, so operators monitor it continually.
Thick bubbly buildup: When travel speed is too slow, the arc dwells and over-melts the edge; assist gas can’t clear the extra melt, leaving gummy slag that flakes but still adds costly cleanup time.
Hard bead or glob: If speed is too fast or torch height is wrong, the kerf fails to expel molten material completely; this tenacious dross is much harder to remove and often forces grinding that risks base metal damage.
Inconsistent dross and rework: Worn nozzles, degraded tips, or contaminated gas destabilize the arc and reduce ejection efficiency, causing uneven patterns and poor corners that demand repeated test cuts and lower throughput.