# Fanuc Series 15i/150i-MA (Programming) Operators Manual

B-63324EN/03 PROGRAMMING 4.INTERPOLATION FUNCIONS
- 91 -
Explanation
- Involute curve
An involute curve on the X-Y plane is defined as follows ;
X(θ)=R[cos θ + (θθo) sin θ] + Xo
Y(θ)=R[sin θ + (θθo) cos θ] + Yo
where,
: Coordinates of the center of a base circle
θo : Angle of the start point of an involute curve
θ : Angle of the point where a tangent from the current
position to the base circle contacts the base circle
X(θ), Y(θ) :Current position on the X-axis and Y-axis
Base circle
Start point
Involute curve
(X,Y)
End point
θ
o
(Xo,Yo)
R
θ
X
Y
Fig.4.12 (b) Involute Curve
Involute curves on the Z-X plane and Y-Z plane are defined in the same
way as an involute curve on the X-Y plane.
- Start point and end point
The end point of an involute curve is specified using address Xp, Yp, or
Zp. An absolute value or incremental value is used to specify an Xp,
Yp, or Zp value. When using an incremental value, specify the
coordinates of the end point viewed from the start point of the involute
curve.
When no end point is specified, P/S alarm No. 935 is issued.
If the specified start point or end point lies within the base circle, P/S
alarm No. 936 is issued. The same alarm is issued if cutter
compensation C causes the offset vector to enter the base circle. Be
particularly careful when applying an offset to the inside of an involute
curve.
- Base circle specification
The center of a base circle is specified with I, J, and K, corresponding
to X, Y, and Z. The value following I, J, or K is a vector component
defined when the center of the base circle is viewed from the start point
of the involute curve; this value must always be specified as an
incremental value, regardless of the G90/G91 setting. Assign a sign to
I, J, and K according to the direction.
If I, J, and K are all left unspecified, or I0J0K0 is specified, P/S alarm
No. 935 or No. 936 is issued.
If R is not specified, or R0, P/S alarm No. 935 or No. 936 is issued.