Tool path generation for grinding a Φ1.45 m off-axis aspherical SiC mirror blank

Off-axis aspherical mirrors are growing in popularity in modern space-borne cameras having high resolutionand large field of view. Fabrication processes for these mirrors include surface generation by grinding wheel, free-abrasive lapping, and various polishing cycles. Surface generation by grinding wheel is the most efficient process among the whole fabrication processes. Therefore, technologies for accurately and cost efficiently generating the mirror blanks are highly indispensable. We propose, a single-point grinding mode and a four-step tool path generation technology to resolve the over travel problem, for directly machining the off-axis aspherical mirror blank. Technologies for surface geometrical modeling and wheel wear reduction/compensationare established. Using a commercial-available HASS-VF8 machining center, a silicon carbide mirror blank having a 1.45 m aperture is successfully generated. Result indicates that the main error source affecting the obtained grinding accuracy is wheel wear amount, other than the positioning accuracy of machining center. Therefore, error-compensation grinding is indispensable. We provide an alternative economical resolution to efficiently fabricate the large-scale off-axis aspherical surface. © 2014 Chinese Optics Letters.