Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 472)

Programming Feedrates
Chapter 18
18-24
If any of the above considerations are not met during the G36.1 mode, the
control will overshoot positions, since the axis will not have time to
decelerate. For example, consider the following velocity curve if a drastic
change in direction is requested after the move from X5 to X5.1 when in
G36.1 mode. Note that the position X5.1 is overshot, and the axis must
reverse direction to reach proper position.
Figure 18.13
Drastic Change in Direction While in Short Block Mode
LINEAR
Deceleration
X5.1
Programmed Feedrate
Axis begins to decelerate at start of block
but is traveling too fast to fully decelerate
before end-of-move.
Tool overshoots
position
F
E
E
D
R
A
T
E
X5 X5.1 X5
Tool overshoots end-point of move because of drastic
change in block direction during short block mode.
Y
CAUTION: The programmer must take into consideration the
direction of travel and change in feedrates of transitions from
block-to-block in the short block mode (G36.1). If the
transition exceeds the deceleration ramp of the axis, damage to
the part or equipment can occur.
G36 and G36.1 are modal. The control should be in short block mode
(G36.1) only when executing a series of fast short blocks that contains only
slight changes in direction and changes in velocity. What constitutes a
slight change in direction and velocity is dependent on the Acc/Dec ramp
configured for your machine.
G36 -- Short Block Acc/Dec Disable
G36.1 -- Short Block Acc/Dec Enable