Mitsubishi Electric MELSEC iQ-R16MTCPU Programming Manual page 179

Controlling linear axes and rotating axes at the same time
Whether the controlling equipment controls linear axes or rotating axes, they are all treated the same way. When controlling a
rotating axis, the values given by coordinate language (A, B, C) are the angles, and the value given by the feed speed (F) is
used as the vector speed for all axes. In other words, 1[degree] for a rotation axis is equivalent to 1[mm] for a linear axis.
Therefore, when linear axes and rotation axes are controlled at the same time, the way in which every axis treats the value
given by "F" is the same as "when controlling a linear axis". In this case, the size of the speed component and direction for
linear axis control do not change, but for rotating axis control the direction of the speed component changes with the
movement of the tool (size does not change), and as a result, the composite feed speed of the tool advance direction changes
with the movement of the tool.
Ex.
Specifying the feed speed as "f", and controlling a linear axis (X-axis) and rotation axis (C-axis) at the same time
When the X-axis incremental command value is "x", and C-axis incremental command value is "c"
θ
End point
c
θ
Center of rotation
The X-axis feed speed (vector speed) "fx", and C-axis feed speed (angular speed) "ω" are as follows:
x
fx = f × • • • • •(1)
2 2
x + c
c
ω = f × • • • • •(2)
2 2
x + c
The vector speed "fc" for C-axis control is:
π × r
fc = ω × • • • • •(3)
180
When the speed of the tool advance direction at the start point is "ft", the speed of the X-axis is "ftx" and the speed of the Y-
axis is "fty", the following formula applies.
π π
ftx = -rsin θ × ω + fx
180 180
π π
fty = -rcos θ × ω • • • • •(5)
180 180
"r" is the distance between the center of rotation and the tool (unit: [mm]), and "" is the angle (unit: [degree]) made with the
start point and X-axis from the center of rotation.
From the formulas (1) to (5), the composite speed "ft" is:
ft = 2 2
ftx + fty
π
2
x - x × c × rsin
180
= f ×
2
x + c
Thus, the feed speed "f" to specify in the program is:
2
x + c
f = ft ×
π
2
x - x × c × rsin
180
Note that "ft" in formula (6) is the speed at the start point, and as the C-axis rotates the value for  changes and thus the value
for "ft" also changes. Therefore in order to keep the cutting speed (ft) fixed as much as possible, keep the rotating angle
specified in a block as small as possible to keep the extent of the change in  small.
ft
fc
End point
fx
fc
ft
• fx: Size and direction are fixed
fx
• fc: Size is fixed, direction changes
x
• ft: Both size and direction change
• • • • •(4)
2
π π × r × c
θ +
90 180
• • • • •(6)
2
2
• • • • •(7)
2
π π × r × c
θ +
90 180
6 AUXILIARY AND APPLIED FUNCTIONS
6.3 Feed Function
6
177