Scanlab RTC 5 PC Interface Board - Speed-Dependent Laser Control

RTC
®
5 PC Interface Board
Rev. 1.9 e
7 Basic Functions for Scan Head and Laser Control
146
innovators for industry
Speed-Dependent Laser Control
For initializing speed-dependent laser control, the
command set_auto_laser_control must be called for
specifying which signal parameter will be readjusted
(via the
Ctrl parameter) and which quantity v
a
shall
be used as the calculation base for speed-dependent
corrections (
Mode parameter).
For subsequent mark and arc commands (also timed
mark commands), the RTC
®
5 will then perform an
automatic speed-dependent correction of the
selected signal parameter (i.e. a correction
dependent on the current speed): The 100% value
defined via set_auto_laser_control (
Value
parameter) will be multiplied by the correction factor
v
a
/ v
s
(exception: for the output period HalfPeriod ,
the correction factor is
v
s
/v
a
). Here, v
s
is the marking
speed defined with set_mark_speed, and
v
a
depends on the definition via
set_auto_laser_control:
•For
Mode =1, v
a
is the actual set speed derived
from the microvector’s step size (in set coordi-
nates).
•For
Mode = 2 (only selectable for iDRIVE
®
scan
systems),
v
a
is the current speed returned by the
scan system, derived as per (v
x
2
+ v
y
2
)
1/2
Notes
•For
Mode =1:
With mark or arc commands, the actual set speed
can deviate from the marking speed defined via
set_mark_speed because the marking time must
be an integer-multiple of 10 µs (the command is
executed via a corresponding number of
microsteps) and the step size (and therefore
effective marking speed = actual set speed) is
automatically adjusted thereto. Particularly for
short lines, the actual set speed is therefore
noticeably variable. Such length-dependent
speed variations – without speed-dependent laser
control – can, for example, cause hatching line
widths to vary.
For timed mark commands, the set speed is
generally determined in accordance with the
specified vector length and marking time, and
therefore usually differs from the marking speed
defined via set_mark_speed.
Speed variations within a marking command
cannot be compensated in
Mode = 1. Anyway,
most standard scan systems can’t supply the
necessary information to the RTC
®
5.
•For
Mode = 2, correction is always performed in
accordance with the current speed so that
automatic laser control can also compensate
speed variations during marking commands (e.g.
during acceleration or deceleration phases).
However, transfer times to/from the scan head
will delay evaluation of the current speed by a
few clock cycles.
This functionality is only practical for scan heads
equipped with special firmware. If you want to
use this functionality, but don’t yet have such a
specially-equipped scan head, then contact
SCANLAB.
• Variable laser impact resulting from explicit
changes in marking speed between two mark
commands via set_mark_speed cannot be
compensated through speed-dependent laser
control.
• Observe all notes on position-dependent laser
control in the section "General Notes", page 141:
the correction factor for speed-dependent laser
control will, if necessary, be multiplied by a
position-dependent laser-control factor and a
nonlinearity factor before being applied to the
100% value.
• If a negative LaserOn delay has been set to
preheat the material before marking (see
page 99), then speed-dependent laser control
might in some circumstances actually be counter-
productive, because this would attenuate laser
power in the acceleration phase at the beginning
of a marking operation. But this can be counter-
acted with the set_auto_laser_control param-
eters
MinValue and MaxValue .
• The speed-dependent laser control’s to-be-
controlled signal parameter, the 100% value and
its corresponding limit values can be specified not
only with set_auto_laser_control, but also via
set_auto_laser_params or
set_auto_laser_params_list.