User manual

PMAC User Manual
Writing Programs for PMAC 169
Note:
Feedrate is a magnitude and should therefore always be a positive number. A
negative Feedrate will cause the motion to be opposite of what is defined as
positive in the Coordinate System definition.
Short Moves
If a feedrate-specified move segment is so short in distance that it cannot reach its target velocity, it will
spend its entire time in acceleration (yielding a triangular rather than trapezoidal profile). The minimum
time for such a move is thus the specified acceleration time (TA or 2TS). For a single move remember to
add on the extra acceleration time to decelerate to a stop.
In a time-specified move segment, if TM is less than the acceleration time, the segment will be done in
acceleration time, not TM time.
In other words, the acceleration time is the minimum time for an individual blended move or blended
move segment. This is in part a protection against move times getting so short that PMAC cannot
calculate them in real time. If working with very short move segments and the move sequence is going
more slowly than desired, this acceleration-time limit may well be causing the problem.
Long Moves
The maximum time for one programmed move is 2
23
-1 (8,388,607) msec, approximately two hours and
20 minutes. This is the maximum value that PMAC will accept with a TM command. In addition, it is the
maximum value PMAC will compute for a feedrate-specified move when it divides the vector distance
for the move by the feedrate. If the vector distance for the move divided by the feedrate yields a time
greater than 8,388,607 msec, PMAC will use 8,388,607 msec as the move time, and the speed will be
higher than what was programmed.