TIRX, TIRY: Tolerance on Surface TIR
TIRX and TIRY are used to analyze tilts of a Standard surface along the X and Y axes, respectively. The Int1 value indicates the number of the surface, and this surface must be a Standard surface type. Surfaces other than Standard surface types may be toleranced using the TETX and TETY operands described later.
TIRX and TIRY are used to specify a tolerance on total indicator runout, or TIR, which measures the amount of "wedge" in a lens.
The min and max values are twice the amount of "sag" in lens units measured at the maximum radial aperture of the surface where the maximum radial aperture is defined by the clear semi-diameter or semi-diameter of the surface. The change in sag as a function of the x or y normalized coordinate for a TIRX or TIRY value is given by:
For example, if the TIRX tolerance is 0.10 mm, then the change in sag at the maximum +x aperture of the lens is 0.05 mm, and the deviation at the maximum -x aperture is -.05 mm, for a "total" TIR of 0.10 mm. A similar discussion applies to TIRY. The min and max values are used to model the tilt of the surface in each direction. The tilt angle that is actually placed on the surface is given by
where S is the clear semi-diameter or semi-diameter of the surface. Note that a sag along Y implies a rotation about the X axis, and a sag along X implies a rotation about the Y axis.
The analysis of TIRX and TIRY uses the Irregular surface type. For more information, search the help files for the discussion "Tolerancing with the Irregular surface type".
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