User's Manual

PMAC User Manual
Writing Programs for PMAC 177
Standard Planes
To specify the circles in the XY plane, simply command NORMAL K-1 (equivalent to G17 in machine-
tool code). Similarly, for circles in the ZX plane, command NORMAL J-1 (G18 equivalent); for circles
in the YZ plane, command NORMAL I-1 (G19 equivalent).
Clockwise Direction Sense
The directional sense of the normal vector is right handed; that is, in a right-handed coordinate system, if
pointing a right thumb in the direction of the specified normal vector, the fingers will curl in the direction
of a clockwise arc in the plane thus specified.
Circle Modes
To put the program in circular mode, use the program command CIRCLE1 for clockwise arcs (G02
equivalent) or CIRCLE2 for counterclockwise arcs (G03 equivalent). LINEAR will go back to linear
blended moves. Once in circular mode, a circular move is specified with a move command specifying the
move endpoint and either the vector to the arc center or the distance (radius) to the center. The endpoint
may be specified either as a position or as a distance from the starting point, depending on whether the
axes are in absolute (ABS) or incremental (INC) mode (individually specifiable).
Center Vector
If the vector method of locating the arc center is used, the vector is specified by its I, J, and K components
(I specifies the component parallel to the X axis, J to the Y axis, and K to the Z axis). This vector can be
specified as a distance from the starting point (i.e. incrementally), or from the XYZ origin (i.e.
absolutely). The choice is made by specifying R in an ABS or INC statement (e.g. ABS (R) or INC
(R)). This affects I, J, and K specifiers together. (ABS and INC without arguments affect all axes, but
leave the vectors unchanged). The default is for incremental vector specification.
Note:
The standard machine tool usage is for incremental vector specification even when
move endpoint specification is absolute.
A typical circular move command with a vector specification is:
X1000 Y2000 I500 J-500
Example:
Starting from the point X0 Y0, make a quarter circle clockwise in the XY plane to X20 Y20, then a linear
move to X40 Y20, then a three-quarters circle clockwise to X20 Y0. With the default modes of absolute
move and incremental vector specification, the program would be:
NORMAL K-1 ; XY plane
F10
CIRCLE1 ; Clockwise circle
X20 Y20 I20 J0 ; Arc move; I=20-0=20; J=0-0=0
LINEAR
X40 Y20
CIRCLE1
X20 Y0 I0 J-20 ; Arc move; I=40-40=0; J=0-20=-20