Cutting Quality - Cebora PLASMA PROF 180 HQC Manual De Instrucciones

4.6

Cutting quality

Various parameters and parameter combinations influence cutting quality: section 4.2.3 of this manual gives the opti-
mal settings for cutting a given material. However, the optimum parameters may vary slightly from those given in the
above charts due to inevitable differences caused by installation on different pantographs and changes in the proper-
ties of the materials being cut. The following points can help the user to make the minor changes necessary to achieve
a good quality cut.
As shown in the cutting charts, different sets of consumables are available depending on the cutting current and gases
used.
If high productivity requirements take precedence and therefore high cutting speeds are needed, set the maximum
permitted current and then the largest diameter nozzle. Conversely, if the focus is on cutting quality (more squaring and
a narrower cutting groove (kerf)), set the minimum permitted current for the material and thickness being processed.
Before making any adjustments check that:
The torch is at right angles to the cutting plane.
Electrode, nozzle, H2O nozzle holder and nozzle guard are not excessively worn and their combination is suitable for
the chosen work.
The cutting direction is correct for the figure to be obtained. Remember that the best cutting side is always clockwise
in relation to the direction of motion of the torch (the holes in the plasma diffuser used are arranged clockwise).
If high thicknesses are to be cut, particular care must be taken during the pierce phase: in particular, try to remove the
build-up of molten metal around the hole from which cutting is started in order to prevent double-arc effects when the
torch passes back over the starting point. In addition, always keep the nozzle guard free of any molten metal slag that
may have stuck to it.
Table 8 shows some of the most common problems and their solutions.
PROBLEM
Inclined cut
Insufficient penetration
Presence of
low-speed dross*
Presence of
high-speed dross**
Rounded cutting edge
* Low speed dross is thick and globular, easily removable. The kerf is quite wide.
** High speed dross is thin and difficult to remove. If the speed is very high, the walls of the cut are somewhat
rough.
124/128
CAUSE
Worn electrode or nozzle
Stand off too high
Cutting speed too high
Cutting speed too high
Nozzle diameter too big for the cur-
rent setting
Workpiece
too thick
for the current setting
Electrical contact between the earth
cable and the cutting chart is not
good
Cutting speed too low
Cutting current too high
Stand off too low
Cutting speed too high
Cutting current too low
Stand off too high
Cutting speed too high
Stand off too high
Table 8
SOLUTION
Replace both
Lower the stand off
Adjust the speed
Adjust the speed
Check the cutting charts
Increase the cutting current
Check tightening of the earth
terminal to the CNC
Adjust the speed
Decrease the cutting current
Raise the stand off
Adjust the speed
Increase the cutting current
Lower the stand off
Adjust the speed
Lower the stand off