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SUMMARY
Arc voltage is a dependent variable. It is dependent upon cutting amperage, nozzle
size, torch stando, cut gas ow rate and cutting speed. An increase in arc voltage can
result from a decrease in cutting speed, an increase in cutting amperage, a decrease
in nozzle size, an increase in gas ow and an increase in torch stando. Assuming
that all of the variables are set as recommended, torch stando becomes the most
inuential variable to the process. Good and accurate height control is a necessity
in producing excellent cut quality.
LOW SPEED DROSS
Globular dross that forms in large
deposits. Comes o very easily.
HIGH SPEED DROSS:
Fine roll over dross that welds to
bottom of edge. Cleaning requires
chipping or grinding.
Fig. 19 - Top Dross Formation
TOP DROSS:
Splatter appears on the top edge of
both pieces of the plate.
Lower the voltage in increments of 5
volts dc (maximum) until top dross
disappears.
Fig. 20 - High Speed Dross
Fig. 21 - Low Speed Dross Formation
4.5 Dross Formation
Cutting speed, gas selection and variations in metal composition contribute to dross
formation. The correct cutting stando also has an inuence on dross formation. If the
arc voltage is set too high, the cut angle becomes positive. In addition, dross forms on
the bottom edge of the part. This dross can be very tenacious and require chipping
and grinding for removal. Setting the cutting voltage too low results in undercutting
the parts or negative cut angle. Dross formation occurs but in most cases it is easily
removed.
Top Dross
Top dross usually appears as splatter near the top edge of the kerf. This is a result of
torch stando (arc voltage) set too high or cutting speed set too fast. Most operators
use the parameter charts for recommended speed. The most common problem is
torch stando or arc voltage control. Simply lower the voltage settings in increments
of 5 volts until the top dross disappears. If an arc voltage control is not used, the torch
can be lowered manually until the dross disappears.
SECTION 4 OPERATION
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