7. Feed Functions
7.6 Feedrate Dsignation and Effects on Control Axes
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(Example)
When the feedrate is designated as "f" and the linear axes (X and Y) are to be controlled
using the circular interpolation function:
The rate in the tool advance direction, or in other words the tangential direction, will be the feedrate
designated in the program.
Linear speed is "f"
y
x
Y
X
i
P
2
P
1
In this case, the feed rate of the X and Z axes will change along with the tool movement. However,
the combined speed will always be maintained at the constant value "f".
When controlling rotary axes
When rotary axes are to be controlled, the designated feedrate functions as the rotary speed of the
rotary axes or, in other words, as an angular speed.
Consequently, the cutting feed in the tool advance direction, or in other words the linear speed,
varies according to the distance between the center of rotation and the tool. This distance must be
borne in mind when designating the feedrate in the program.
(Example)
When the feedrate is designated as "f" and rotary axis (CA) is to be controlled ("f" units
=
°
/min)
Rotation
center
P
2
(tool end point)
P
1
(tool start point)
Angular speed is "f"
Linear speed is :
c
π•
r
•
f
180
r
In this case, in order to make the cutting feed (linear feed) in the tool advance direction
"fc" :
fc = f ×
π
•
r
180
Therefore, the feedrate to be designated in the program must be :
f = fc ×
180
π
•
r