21
8 CUTTING QUALITY
There are several parameters and combinations of them
that affect the quality of the cut: This manual shows the
optimal settings for cutting a particular material. How-
ever, due to the installation differences as well as pan-
tographs and the variation of the characteristics of the
cutting materials, the optimal parameters may require
changes with respect to those indicated in the present
cutting tables. The following points may help the user to
make the changes necessary to obtain a good cutting
quality.
As shown in these cutting tables, for each thickness of a
particular material can be used different currents cutting.
If prevail productivity needs, set the maximum allowable
current and the speed in the column V
production.
PROBLEM
CAUSE
SOLUTION
Oblique cutting
Electrode or nozzle worn out
Replace both
Stand off too high
Lower
stand off
Cutting speed too high
Adjust speed
Insufficient
penetration
Cutting speed too high
Adjust speed
Nozzle diameter too large compared to the
current set
Check cutting tables
Excessive plate thickness in
processing compared to the current set
Increase cutting speed
Ground wire not in good electrical contact with
the cutting plane
Check the tightness of the earth terminal to the
CNC
Presence of
“low speed
dross” *
Cutting speed too low
Adjust speed
Cutting speed too high
Reduce cutting current
Stand off too low
Raise
stand off
Presence of
“high speed
dross" **
Cutting speed too high
Adjust speed
Cutting speed too low
Increase cutting current
Stand off too high
Lower
stand off
Rounded cut
edge
Cutting speed too high
Adjust speed
Stand off too high
Lower the
stand off
* The low speed dross are thick dross, of globular shape, easy to remove. The kerf is fairly large.
** The high speed dross are thin dross, hard to remove. In case of very high speed, the cut wall is rather rough.
Before making any adjustments, verify that:
• the torch is perpendicular to the cutting plane.
• electrode, nozzle and nozzle protection are not worn
out and that their combination is responsive to the
chosen work.
• the cutting direction, in function of the shape to be
obtained, is correct. Remind that the best side of a
cut is always the right with one respect to the torch
motion direction (the plasma used has diffuser holes
in a clockwise direction).
If you need to cut high thicknesses, particular attention
should be given during the step of lead-out: in particular,
when trying to remove the accumulation of molten mate-
rial around the cutting start hole, so as to avoid double
arc phenomena when the torch comes by again to the
starting point. Moerover, keep the nozzle protection al-
ways clean from molten slag which sticked.
The following table shows some of the most frequent
problems and their solutions.
