RTC6 boards
Doc. Rev. 1.0.21 en-US
7 Basic Functions for Scan Head Control and Laser Control
170
7.3.4 3D Image Field
Carrying Out Adjustment
SCANLAB 3D correction tables are calculated such
that the plane of the middle focus position is
controlled with z = 0.
Therefore, the mechanical distance between
scan system and working plane must be adjusted
accordingly. With the varioSCAN series, a specific
distance to the scan system has to be maintained in
addition. The values are to be taken from the manual
of the respective 3-axis scan system or varioSCAN.
Deviations from these should preferably be set via the
user program by set_defocus, set_defocus_offset,
set_offset_xyz or the corresponding list commands.
Once the working distance and distance to the
scan system are correctly adjusted, then
subsequently the laser focus position should be fine-
tuned. For this, a test pattern is to be marked in the
middle of the z = 0 working plane. The optimum
laser focus position for processing results can be
achieved:
• With the varioSCAN series, by manually turning
the focusing ring, see corresponding Manual
• With a varioSCAN FLEX, by adjusting the focusing
optic position, see Manual for
“RTC5/6 varioSCAN 40 FLEX Extension” extension
board (#128683)
• With a varioSCAN FC and intelliWELD FC by
adjusting the coefficient A of the used
3D correction table
(1)
Checking the z axis Calibration
The optimum output values for the z axis also depend
on various parameters such as beam divergence of
the used laser and tolerances of the optical
components.
Such information is generally not available to
SCANLAB and therefore, are not included in the
calculation of 3D correction tables.
Therefore, in some cases the calculated
3D correction table might not fit optimally the
individual scan system. To test whether this is the
case, run a laser marking test that covers the entire
3D Image Field.
Check if the laser focus meets the requirements of
your application. If you find that the spot diameter
varies considerably, then a recalibration of the z axis
correction may help under certain circumstances.
The aim of the z axis calibration procedure is to
determine suitable coefficients A, B and C. These can
be transferred to the RTC6 PCIe Board by
load_z_table.
A, B and C are coefficients of the parabolic function
z
out
= A + Bl +Cl
2
(focus length value l in the RTC4 compatibility range
[–32,768…+32,767], see load_z_table_no;
See also Notes below).
They determine the relationship between the
z output value z
out
and the focus length value l.
For each point (x|y|z) in the 3D Image Field, the
focus length value l corresponds to the focus length
difference between the specified point (x|y|z) and
the point(0|0|0).
The ABC coefficient values of a correction file on the
PC can be read out directly with read_abc_from_file
and written into with write_abc_to_file, see
following Notes.
(1) Coefficients A, B and C can be queried by
get_head_para an
d newly set by load_z_table.
Only A should be modified. B and C should be passed
over unchanged – as queried – by load_z_table.
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