Reference Manual

PMAC 2 Software Reference

52 PMAC I-Variable Specifiation

Before V1.16 firmware, an arc was added to an outside corner if the change in directed

angle were greater than 1

Example

If it is desired that an arc only be added if the change in directed angle is greater than 45

then I89 should be set to 0.707, because cos ∆θ = cos 45

= 0.707

See Also

Cutter Radius Compensation (Writing a Motion Program)

I90 Minimum Arc Angle

Range

Non-negative floating point

Units

Semi-circles (π radians; 180 degrees)

Default

0 (sets 2

-20

)

Remarks

I90 sets the threshold between a short arc and a full circle for CIRCLE mode moves in

PMAC in all coordinate systems. I90 is expressed as an angle, with units that represent a

fraction of a half-circle. It represents the smallest angle that can be covered by a

programmed arc move.

Any programmed CIRCLE-mode move with an IJK-vector representation of the center

which covers an angle smaller than I90 is executed as a full circle plus the programmed

angle change. Any such move which covers an angle greater than I90 is executed as an arc

smaller than a full circle.

The purpose of I90 is to support the circle programming standard that permits a full-circle

move to be commanded simply by making the end point equal to the starting point (0

degree arc), yet allow for round-off errors.

Most users will be able to leave I90 at the default value of one-millionth of a semi-circle.

This was formerly the fixed threshold value. However, some users may want to enlarge

the threshold to compensate for round-off errors, particularly when using cutter-radius

compensation in conjunction with full-circle moves. Remember that no arc covering an

angle less than I90 can be executed.

If a full-circle move is commanded with cutter compensation on, and the blending from the

previous move or into the next move creates a compensated outside corner without adding

an arc (see I89), PMAC will extend the compensated move past a full circle. If I90 is too

small, it may execute this as a very short arc, appearing to miss the move completely. I90

may have to be increased from its effective default value to cover this case.

For backward compatibility reasons, if I90 is set to 0, a threshold value of 2

-20

(about one-

millionth) of a semi-circle will be used.