7.1.6 Synchronising the Laser and Scanners |
An ideal galvanometer scanner would accelerate instantly to some specified velocity when commanded to start scanning a vector.
Similarly, an ideal laser source would start emitting power immediately on being commanded to do so.
Given both of the above, and assuming that an ideal SP-ICE-3 Card could issue the go!
to them simultaneously, the two would be forever perfectly synchronised.
Unfortunately, we have to work with what we're given by the real world...
Scanner TrackingError Time Compensation.Real galvanometer scanners exhibit inertia, which basically means that they take some time to accelerate to the specified velocity when they are commanded to start scanning a vector. The time that elapses between the scanner receiving a position update and actually arriving at that position is called the Scanner TrackingError Time.
Most lasers, on the other hand, start emitting power relatively quickly after being commanded to do so. [Note 1]
Consequently, if the laser is switched on simultaneously with the initial position update command(s), it will tend to over-expose the first part of the vector, because the scanner is still accelerating.
We can compensate for this by introducing a delay between the start of scanning and the start of laser emission, and for this purpose the SP-ICE-3 Card implements the AxisParameterSetTrackingError property.
The TrackingError property should normally be set to the value specified in the scanner's data manual.
Occasionally, it may be desirable to fine tune the value for a particular application. However, marking quality may be reduced and the processing time unnecessarily extended if the value is not carefully optimised.
The following symptoms indicate a badly adjusted TrackingError value:
Laser Trigger Delay Compensation.
Sending a trigger signal or command (Start emitting now!
) to a laser will not result in absolutely immediate emission of energy: rather, there will be a (small) delay while the signal or command is transmitted to the laser source, and possibly a further delay while the source interprets and acts upon it. [Note 1]
The SP-ICE-3 Card can take this delay into account via the LaserConfigLaserTriggerDelay property.
The LaserTriggerDelay should normally be set to the value specified in the laser's data manual.
Occasionally, it may be desirable to fine tune the value for a particular application. However, marking quality may be reduced and the processing time unnecessarily extended if the value is not carefully optimised.
NotesThere are indeed some lasers, notably large CO2 types, which react slower than the average scanner.
For these lasers, the LaserTriggerDelay will be longer than the TrackingError.