RTC
®
5 PC Interface Board
Rev. 1.9 e
8 Advanced Functions for Scan Head and Laser Control
175
Procedure:
(1) Adjust the correct mechanical distance between
the scan system and the z = 0 working plane and
– if applicable – the correct distance between the
varioSCAN and the scan system
(1)
.
(2) Load the desired 3D correction table via
load_correction_file and assign it via
select_cor_table.
(3) Use the command get_head_para to read out
the assigned coefficients A, B and C.
For the varioSCAN FC (also with an intelliWELD
®
FC),
steps (4) to (7) don’t need to be performed. In this
case, proceed directly to step (8).
(4) Use the command goto_xyz to move the laser
spot to the reference point
(2)
.
(5) Place a test object at the reference point.
(6) Use the command load_z_table(0, 0, 0) to set
the Z axis to the neutral (middle) position.
(7) Now adjust the laser focus
–with a varioSCAN or a varioSCAN
de
by manually
adjusting the focusing ring
–with a varioSCAN
FLEX
by adjusting the focusing
optic’s position via the command move_to.
(8) Move the focus to an arbitrary point
(x|y|z)
within the required image space using the
command goto_xyz
(3)
.
(9) Use the command get_z_distance to query the
focus length value l (in bits) set by the RTC
®
5 for
this point
(4)
.
(10)Optimize the laser focus at this new location.
Therefore, use the command
load_z_table(A=z
out
, 0, 0) to vary the Z output
value z
out
until the quality of the laser focus
meets your requirements
(5)
.
(11)Repeat steps (8) through (10) for as many loca-
tions
(x|y|z)
as possible
(6)
and write down the
values (l|z
out
) for each new point. If possible,
seek to thereby cover the entire working space
required by your application.
(12)Fit your set of (l|z
out
) values to a function of
the type z
out
= A + Bl +Cl
2
.
(13)Use the resulting coefficients A, B and C to adjust
the 3D correction table via load_z_table(A, B, C).
(14)Values loaded via load_z_table will be over-
written by a subsequent load_correction_file
command (load_correction_file sets the three
coefficients A, B and C to the default values of the
loaded correction table
(7)
). After each
load_correction_file, you should therefore also
call load_z_table(A, B, C) again.
Test for 3-Axis Scan Systems with F-Theta
Objective
• With the adjusted 3D correction table, mark two
identical large squares using 3D vector
commands (see page 172). Mark one of the
squares with the work piece in Z-position
z=z
min
, the other one with z = z
max
.
• These two squares should match exactly. If this is
not the case, your correction file is not perfectly
suited to your objective. To solve this problem,
measure the size (x and y) of both squares and
report these values to SCANLAB. You will then
receive a new 3D correction file.
(1) See the corresponding 3-axis scan system’s or the varioSCAN’s
user manual.
(2) The reference point’s coordinate values (in mm) are provided in
the “Readme.txt” file that accompanies your 3D correction file
or in the 3-axis scan system’s or the varioSCAN’s user manual.
If you are using an F-Theta objective, the reference point is
generally the origin
(0|0|0)
. The reference point is a point in
the z = 0 working plane for which a middle focus length value
is required for a sharp laser focus. The laser beam shall be
focused to the reference point when the Z axis is set to the
neutral position (Z output value z
out
= 0).
(3) If you are using a scan system with an F-Theta objective, it is
sufficient to select various points (0|0|z) on the Z coordinate
axis. The maximum possible working volume is specified in the
corresponding user manual.
(4) The focus length value l can be positive or negative.
(5) The optimal z
out
output value can be positive or negative.
When seeking the optimal laser focus, you can calculate a
starting value in accordance with A + Bl +Cl
2
by using the
previously read focus length value l and the previously read or
used values A, B and C.
(6) Note that larger z control values lead to shorter working
distances and that the focus will thereby shift toward the scan
system. The test object might have to be tracked accordingly.
(7) Each 3D correction table calculated by SCANLAB contains
values for the coefficients A, B and C (also see the respective
“Readme.txt” file or get_table_para).
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