Specifications

14.3
Motion Control
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14.3.7 Speed feedforward
On YS 840DI system, speed feedforward is one of CNC functions. CNC specifies the speed
feed forward directly to the drive.
(The feed forward function housed in servo drives is not used.)
On YS 840DI, the speed feedforward is also used for switching the speed reference mode to
the positioning reference mode as well as for instructing the spindle orientation (SPOS com-
mand), you must specify the valid setting (MD32620 = 3) for every axis.
For positioning control of feed axes, in order to activate the speed feedforward, specify
Start/End code to CNC program as followings.
N1G91G01Y100.F2000
N2Y-100.
FFWON (
Feedforward starts)
N3G01Y100.
N4Y-100.
FFWOF (
Feedforward ends)
M30
On YS 840DI, however, for compensation of the machining profile errors occurred during
the cutting feed, predictive control is generally used instead of the feedforward. For the
usage of the predictive control, see 14.2.8.
CNC machine data for the feedforward is listed below.
• MD32620 FFW_MODE (For each axis)
Meaning: Feedforward setting
Setting value: 0---Feedforward is disabled
3---Feedforward is defined as speed feedforward.
You must specify "3".
Note: Setting value "1" is for compatibility with conventional systems and
causes no serious problem.
• MD32630 FFW_ACTIVATION_MODE (For each axis)
Meaning: FFWON command with program
Setting value: 0---enabled
1---disabled
• MD32810 EQUIV_SPEEDCTRL_TIME (For each axis)
Meaning: Speed feedforward time constant
This adjusts the machine data and checks radius for shrinkage, or over-
shoot.
Setting value: [sec]