Siemens SINUMERIK 840Di sl Programming Manual page 297

Handwheel travel with velocity overlay, FDA[axis]=...
In NC blocks with programmed FDA[...], the feedrate from the last programmed FA value is
accelerated or decelerated to the value programmed under FDA. Starting from the current
feedrate FDA, you can turn the handwheel to accelerate the programmed movement to the
target position or delay it to zero. The values defined in the machine data are used for the
maximum velocity.
Example:
N10 POS[U]=10 FDA[U]=100
POSA[V]=20 FDA[V]=150
Note
With velocity override of path axes, you always control the path velocity with the handwheel
of the 1st geometry axis.
Traversing range
The traversing range is limited by the starting position and the programmed end point.
Manual override in automatic mode
The manual override function in automatic mode for POS/A axes has two different effects
that are analogous to Jog functions.
1. Path override: FDA [ax] = 0
2. Velocity override FDA [ax] > 0
Fundamentals
Programming Manual, 11/2006, 6FC5398-1BP10-2BA0
The axis does not move. Handwheel impulses received for each IPO cycle are traversed
directionally and path-specifically. When the target position is achieved, the axis
decelerates.
The axis approaches the target position at the programmed axis speed. This enables
target position to be reached even without handwheel impulses. Pulses received for each
IPO cycle are converted to an accumulative change in the existing velocity. Impulses in
the traversing direction increase the velocity. Velocity is limited to the maximum axis
velocity MAX_AX_VELO. Impulses away from the traversing direction decrease the
velocity. The minimum velocity is 0.
Feedrate Control and Spindle Motion
7.7 Feedrate with handwheel override (FD, FDA)
297