Operation
Spirit200a User’s Manual Rev J
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4-21
Cut Quality
Before the optimum cutting condition can be achieved on a particular material
type and thickness, the machine operator must have a thorough understanding
of the cutting characteristics of the Spirit system. When the cut quality is not
satisfactory, the cutting speed, torch height, or gas pressures may need to be
adjusted in small increments until the proper cutting condition is obtained. The
following guidelines should be useful in determining which cutting parameter to
adjust.
Note: Before making any parameter changes, verify that the torch is square to the
workpiece. Also, it is essential to have the correct torch parts in place and to ensure that
they are in good condition. Check the electrode for excessive wear and the nozzle and
shield cap orifices for roundness. Also, check the parts for any dents or distortions.
Irregularities in the torch parts can cause cut quality problems.
1. A positive cut angle (top dimension of piece smaller than the bottom
dimension) usually occurs when the torch standoff distance is too high,
when cutting too fast, or when excessive power is used to cut a given plate
thickness.
2. A negative cut angle (top dimension of piece larger than the bottom
dimension) usually occurs when the torch standoff distance is too low or
when the cutting speed is too slow.
3. Top dross usually occurs when the torch standoff distance is too high.
4. Bottom dross usually occurs when the cutting speed is either too slow (slow-
speed dross) or too fast (high-speed dross). Low-speed dross is easily
removed, while high-speed dross usually requires grinding or chipping off.
When using oxygen as the shielding gas, bottom dross can sometimes be
removed by increasing the shield gas pressure. However, increasing the
shield pressure too much can cause cut face irregularities (see below).
Bottom dross also occurs more frequently as the metal heats up. As more
pieces are cut out of a particular plate, the more likely they are to form
dross.
5. When using oxygen as a shielding gas, cut face irregularities usually
indicate that the shield gas pressure is too high or the torch standoff
distance is too low.
6. A concave cut face usually indicates that the torch standoff distance is too
low or the shield gas pressure is too high. A convex cut face usually
indicates that the torch standoff distance is too high or the shield gas
pressure is too low.
7. Note that different material compositions have an effect on dross formation.
8. If the material is not being completely severed, the likely causes are that the
cutting current is too low, the travel speed is too high, the gas pressures are
incorrect, the incorrect gas types are selected, the incorrect consumables
are installed in the torch, or the consumables are worn
