Reference Manual

Turbo PMAC/PMAC2 Software Reference

Turbo PMAC Program Command Specification 456

where:

 {vector} is one of the letters I, J, and K, representing components of the total vector parallel to the

X, Y, and Z axes, respectively

 {data} is a constant or expression representing the magnitude of the particular vector component.

This statement defines the orientation of the plane in XYZ-space in which circular interpolation and cutter

radius compensation will take place by setting the normal (perpendicular) vector to that plane.

The vector components that can be specified are I (X-axis direction), J (Y-axis direction), and K (Z-axis

direction). The ratio of the component magnitudes determines the orientation of the normal vector, and

therefore, of the plane. The length of this vector does not matter – it does not have to be a unit vector.

The direction sense of the vector does matter, because it defines the clockwise sense of an arc move, and

the sense of cutter-compensation offset. Turbo PMAC uses a right-hand rule; that is, in a right-handed

coordinate system (I x J = K), if a right thumb points in the direction of the normal vector specified here,

the right fingers will curl in the direction of a clockwise arc in the circular plane, and in the direction of

offset-right from direction of movement in the compensation plane. In general, the negative normal

vector produces the clockwise/counterclockwise sense expected.

Examples:

The standard settings to produce circles in the principal planes will therefore be:

NORMAL K-1 ; XY plane -- equivalent to G17

NORMAL J-1 ; ZX plane -- equivalent to G18

NORMAL I-1 ; YZ plane -- equivalent to G19

By using more than one vector component, a circular plane skewed from the principal planes can be defined:

NORMAL I0.866 J0.500

NORMAL J25 K-25

NORMAL J(-SIN(Q1)) K(-COS(Q1))

NORMAL I(P101) J(P201) K(301)