Part-holding fixture for grinding wedged optical flats

A grinding system for machining optical flats with wedged planar surfaces comprising:

• a rotatable work spindle having a central vacuum draw;
• a rotatable tool spindle for supporting a grinding tool;
• a feed system for relatively translating the rotatable work spindle and the rotatable tool spindle with respect to each other;
• a part-holding fixture having a first end adapted for rotation with the rotatable work spindle about a rotational axis and a second end adapted for supporting an optical flat having top and bottom planar surfaces;
• a central aperture formed through the part-holding fixture in communication with the central vacuum draw;
• a mounting land formed on the second end of the part-holding fixture surrounding the central aperture and having a closed shape for forming a vacuum seal against the bottom planar surface of the optical flat;
• and
• the bottom planar surface of the optical flat having a planar surface normal that is inclined to the rotational axis of the part-holding fixture when engaged with the mounting land formed on the second end of the part-holding fixture.

A method of machining optical flats with wedged planar surfaces comprising the steps of:

• mounting an optical flat having top and bottom surfaces on a first part-holding fixture such that the top surface is in contact with a mounting land of the first part-holding fixture;
• rotating the first part-holding fixture about a work spindle rotational axis;
• rotating a grinding wheel into engagement with the bottom surface of the optical flat about a tool spindle rotational axis;
• grinding the bottom surface of an optical flat into a planar form having a planar surface normal that extends parallel to the work spindle rotational axis;
• mounting the bottom planar surface of the optical flat in contact with a mounting land of a second part-holding fixture in a position that orients the normal of the bottom planar surface at an inclination with respect to the work spindle rotational axis;
• rotating the second part-holding fixture about the work spindle rotational axis;
• rotating a grinding wheel into engagement with the top surface of the optical flat about the tool spindle rotational axis;
• and
• grinding the top surface of the optical flat into a planar form having a planar surface normal that extends parallel to the work spindle rotational axis, but is inclined with respect to the planar surface normal of the bottom planar surface.

A method of machining optical flats with wedged planar surfaces comprising the steps of:

• mounting an optical flat having top and bottom surfaces on a first part-holding fixture;
• rotating the first part-holding fixture about a work spindle rotational axis;
• rotating a grinding wheel into engagement with the bottom surface of the optical flat about a tool spindle rotational axis;
• grinding the bottom surface of an optical flat into a planar form having a planar surface normal that extends parallel to the work spindle rotational axis;
• mounting the bottom planar surface of the optical flat on a second part-holding fixture in a position that orients the normal of the bottom planar surface at an inclination with respect to the work spindle rotational axis;
• rotating the second part-holding fixture about the work spindle rotational axis;
• rotating a grinding wheel into engagement with the top surface of the optical flat about the tool spindle rotational axis;
• and
• grinding the top surface of the optical flat into a planar form having a planar surface normal that extends parallel to the work spindle rotational axis, but is inclined with respect to the planar surface normal of the bottom planar surface,
• wherein the steps of mounting the bottom planar surface includes applying a pressure reduction against the bottom planar surface for holding the optical flat against the second part-holding fixture that is rotatable about the work spindle axis.