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PMAC 2 Software Reference

PMAC Program Command Specification 335

NORMAL

Function

Define Normal Vector to Plane of Circular Interpolation and Cutter Radius Compensation

Type

Motion program (PROG and ROT)

Syntax

NORMAL {vector}{data} [{vector}{data}...]

NRM {vector}{data} [{vector}{data}...]

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.

Remarks

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. PMAC uses a right-hand rule; that

is, in a right-handed coordinate system (I

x J = K), if your right thumb points in the

direction of the norma vector specified here, your 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.

Example

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)