Programming manual.
CNC 8070
6.
TECHNOLOGICAL FUNCTIONS
Feedrate related functions
·108·
(REF: 1709)
6.2.7 Feed-Forward control (G134)
Feed-Forward control may be used to reduce the amount of following error (axis lag).
Feed-forward may be applied via machine parameters and via PLC as well as by program.
The value defined by PLC will be the one with the highest priority and the one defined by
the machine parameters will have the lowest priority.
Programming
G134
Percentage of Feed-Forward to be applied
The Feed-Forward percentaje is set by G134 followed by the axes and the new percentage
of Feed-Forward to be applied to each axis.
The Feed-forward values to be applied may be defined with up to two decimals.
Considerations
The maximum Feed-Forward value to be applied is 120%.
The programmed percentages are absolute, in other words, programming a 50% twice
means that 50% will be applied, not 25%.
The value defined with G134 prevails over those defined in the machine parameters, but not
over the one defined by PLC.
Properties of the functions
Function G134 is modal.
On power-up, after an M02 or M30, EMERGENCY or a RESET, the CNC restores the Feed-
Forward set by the machine manufacturer for each axis.
Variable to define the feed-forward from the PLC
The write variable (V.)A.PLCFFGAIN.Xn may be used to set the feed-forward for each
axis from the PLC. The value defined by this variable prevails over the ones defined by
machine parameters or by program.
Setting this variable with a negative value cancels its effect (a zero value is also valid). This
variable is initialized neither by a reset nor when validating the parameters.
G134 X50.75 Y80 Z10 (Percentage of Feed-Forward to be applied:)
(On the X axis = 50.75%)
(On the Y axis = 80%)
(On the Z axis = 10%)
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