RTC
®
4 PC Interface Board
Rev. 1.3 e
4 Principle Of Operation
17
innovators for industry
LaserOn Delay
The LaserOn delay defines the moment when the
RTC
®
4 turns on the laser.
LaserOn delay
is automati-
cally inserted at the start of a mark or arc command
(first microstep). Thus, the laser is switched on only
after execution of the first few microsteps. This delay
can be used for several purposes:
• Many applications require laser marking without
variations of intensity, especially without burn-in
effects at the start or end of a vector. To achieve
homogenous marking results, it is essential to
scan the vectors with a constant velocity.
At the beginning of a mark or arc vector, however,
the mirrors first have to be accelerated up to the
defined marking speed.
shows that the laser focus initially moves only
very slowly. A burn-in effect may occur.
To avoid this, the
LaserOn delay
must be set to a
suitable,
positive
value. Thus the mirrors will have
already reached a certain angular velocity when
the laser eventually turns on. However, if the
LaserOn delay is too long, the first part of
the vector will be cut off.
• Some materials take some time until they react to
the exposure to laser radiation. In this case, it can
be useful to "preheat" the starting point of a mark
or arc vector before marking. This can be done by
setting the LaserOn delay to a
negative
value.
A negative LaserOn delay extends the total marking
time, because it is inserted
before
the actual mark or arc
command.
LaserOff Delay
• Due to the acceleration phase at the beginning
of the movement, a difference (
lag
) occurs
between the set position and the real position
of each mirror – see
After execution of a mark or arc command, the
laser should not be turned off immediately
because the scanners have not yet reached the
final set position. Therefore a
LaserOff delay
is
inserted automatically before the laser is turned
off.
Scanner Delays
The command
defines the scanner delays. The time resolution for
the scanner delays is
10
µ
s
.
Jump Delay
When executing a jump command, the mirrors first
have to be accelerated up to the defined jump speed.
Because of the inertia of the mirrors, a
lag
occurs
between the set position and the real position –
see
.
At the end of the jump, a certain settling time is
necessary for the mirrors to reach the set position
within some accuracy. To allow for the settling time
and for the lag, the RTC
®
4 inserts a
jump delay
after
each jump command, before the next command is
executed.
Note that the necessary settling time depends on the
selected jump speed. A higher jump speed usually
requires a longer jump delay. The total time needed
for the entire jump command is the sum of the actual
jump time and the jump delay. It can be minimized by
optimizing the jump speed and the jump delay.
• There are three different types of scanner delays:
jump delay
,
mark delay
and
polygon delay
.
After each vector or arc command, the RTC
®
4
inserts one of these delays before the next
command is started.
