
PROGRAMMING
B–63014EN/02
4. INTERPOLATION FUNCTIONS
55
Spiral interpolation in the XY plane is defined as follows:
(X – X
0
)
2
+ (Y – Y
0
)
2
= (R + Q’)
2
X
0
: X coordinate of the center
Y
0
: Y coordinate of the center
R : Radius at the beginning of spiral interpolation
Q’ : Variation in radius
When the programmed command is assigned to this function, the
following expression is obtained:
(X – X
S
– I)
2
+ (Y – Y
S
– J)
2
=
(R+ĂĂL'Ă+ąąăQ
θ
360
2
where
X
S
: X coordinate of the start point
Y
S
: Y coordinate of the start point
I : X coordinate of the vector from the start point to the center
J : Y coordinate of the vector from the start point to the center
R : Radius at the beginning of spiral interpolation
Q : Radius increment or decrement per spiral revolution
L’ : (Current number of revolutions) – 1
θ : Angle between the start point and the current position
(degrees)
Block overlap between a spiral/conical interpolation block and other
blocks is performed only in simple high–precision contour control mode
(see II–19.6). In other modes, the movement is decelerated and stopped
in the block before the spiral/conical interpolation block, after which
interpolation starts. After completion of the spiral/conical interpolation
block, the movement is decelerated and stopped, then the next block is
executed.
For conical interpolation, two axes of a plane and two additional axes, that
is, four axes in total, can be specified. A rotation axis can be specified as
the additional axis.
The spiral or conical interpolation command can be programmed in cutter
compensation C mode. At the start and end points of the block, a virtual
circle around the center of the spiral interpolation is drawn. Cutter
compensation is performed along the virtual circle, then spiral
interpolation is performed about the result of the cutter compensation.
When both the start point and end point are at the center, no virtual circle
can be drawn. If drawing is attempted, P/S alarm No. 5124 is issued.
During spiral interpolation, the function for clamping the feedrate by arc
radius (parameters 1730 to 1732) is enabled. The feedrate may decrease
as the tool approaches the center of the spiral.
When the dry run signal is inverted from 0 to 1 or from 1 to 0 during
movement along an axis, the movement is accelerated or decelerated to
the desired speed without first reducing the speed to zero.
Explanations
D Function of spiral
interpolation
D Movement between
blocks
D Controlled axes
D Cutter compensation C
D Feedrate clamping by
arc radius
D Dry run