When cutting carbon steel up to 2 in. thick using optimum parameters, precision plasma systems, like the Spirit® II and ProLine™, are capable of consistently producing parts that are virtually dross free. However, it is not uncommon for those who are new to cutting with precision plasma, or even those who have years of experience, to have encountered dross buildup and the many hours of labor expense required to grind or chip away the dross before the parts can move to the next phase of production. The ability to identify the type of dross and understand the possible cause can help the operator reduce or eliminate the problem and, as a result, save their company the time and money associated with secondary processing.
What is dross?
Dross is molten metal that does not blow away during the cutting process and instead adheres to the bottom or top of the part in a re-solidified state. There are many factors that can contribute to the accumulation of dross. The most common are: cutting speed, torch standoff height or damaged consumables. In most instances, dross can be reduced or eliminated completely by adjusting the cutting speed to the optimum condition as prescribed in the operator’s manual. However, there may be times when a simple speed adjustment is not possible or will have little effect, such as when the thickness of the material or the cutting amperage requires a slow cutting speed. In this case, dross accumulation is inevitable and cannot be eliminated. Also, the quality, grade and composition of the material are factors that can increase the likelihood of dross and are outside of the control of cutting parameters. For example, a lower quality sheet of carbon steel may be more susceptible to dross buildup due to the increased level of impurities. Finally, as the temperature of the plate increases from the plasma cutting process, dross is more likely to stick to the bottom even with optimum parameters.