GENERATION OF LARGE OPTICAL SURFACES THROUGH CNC THERMALLY ASSISTED DUCTILE REGIME GRINDING

DUCTILE CHIP FORMATION, UNLIKE THE BRITTLE CHIP FORMATION TYPICALLY OBSERVED IN DIAMOND GRINDING OF CERAMICS, DOES NOTLEAVE BEHIND SURFACE OR SUBSURFACE MICROCRACKS. ACCORDINGLY, MACHINE PROCESSES INVOLVING POLISHING CAN BE ELIMINATED FROM FABRICATION IF MATERIAL REMOVAL DURING GRINDING OCCURS THROUGH DUCTILE CHIP FORMATION. DUCTILE CHIP FORMATION IS ESSENTIALLY AN EXTRUSION PROCESS IN WHICH AN INSTABILITY IS CREATED AND A CHIP IS FORMED. HOWEVER, THIS METHOD OF GRINDING REQUIRES HIGH SPECIFIC ENERGY AND CAN CAUSE EXCESSIVE MACHINE VIBRATIONS, THUS AFFECTING THE ACCURACY OF SURFACE GENERATION. THE INNOVATION IN THIS PROJECT IS TO IMPROVE DUCTILE GRINDING OF BRITTLE MATERIALS BY INTRODUCING A PREDETERMINED PATTERN OF MICROCRACKS WITHIN THE INTENDED DEPTH OF CUT OF THE WORKPIECE. THIS MAY BE ACHIEVED BY INTRODUCING A SUITABLY PULSATING THERMAL FIELD IMMEDIATELY AHEAD OF THE GRINDING ZONE. THE MODULI OF THE CERAMIC MATERIAL IN THE THERMALLY INDUCED MICROCRACKED LAYER WILL BE CONSIDERABLY LOWER THAN THAT OF THE VIRGIN MATERIAL, AND EXTRUDING THE MICROCRACKED LAYER TOPRODUCE A DUCTILE CHIP WILL CONSUME SIGNIFICANTLY LESS SPECIFIC ENERGY. SUCH A PROCESS WILL NOT REQUIRE FURTHER POLISHING. MACHINE VIBRATIONS WILL BE SUBSTANTIALLY REDUCED, AND LOW SPECIFIC ENERGY WILL ALLOW THE USE OF SIC WHEELS, MAKING THE GRINDING PROCESS MORE ECONOMICAL. DUCTILE CHIP FORMATION, UNLIKE THE BRITTLE CHIP FORMATION TYPICALLY OBSERVED IN DIAMOND GRINDING OF CERAMICS, DOES NOTLEAVE BEHIND SURFACE OR SUBSURFACE MICROCRACKS. ACCORDINGLY, MACHINE PROCESSES INVOLVING POLISHING CAN BE ELIMINATED FROM FABRICATION IF MATERIAL REMOVAL DURING GRINDING OCCURS THROUGH DUCTILE CHIP FORMATION. DUCTILE CHIP FORMATION IS ESSENTIALLY AN EXTRUSION PROCESS IN WHICH AN INSTABILITY IS CREATED AND A CHIP IS FORMED. HOWEVER, THIS METHOD OF GRINDING REQUIRES HIGH SPECIFIC ENERGY AND CAN CAUSE EXCESSIVE MACHINE VIBRATIONS, THUS AFFECTING THE ACCURACY OF SURFACE GENERATION. THE INNOVATION IN THIS PROJECT IS TO IMPROVE DUCTILE GRINDING OF BRITTLE MATERIALS BY INTRODUCING A PREDETERMINED PATTERN OF MICROCRACKS WITHIN THE INTENDED DEPTH OF CUT OF THE WORKPIECE. THIS MAY BE ACHIEVED BY INTRODUCING A SUITABLY PULSATING THERMAL FIELD IMMEDIATELY AHEAD OF THE GRINDING ZONE. THE MODULI OF THE CERAMIC MATERIAL IN THE THERMALLY INDUCED MICROCRACKED LAYER WILL BE CONSIDERABLY LOWER THAN THAT OF THE VIRGIN MATERIAL, AND EXTRUDING THE MICROCRACKED LAYER TOPRODUCE A DUCTILE CHIP WILL CONSUME SIGNIFICANTLY LESS SPECIFIC ENERGY. SUCH A PROCESS WILL NOT REQUIRE FURTHER POLISHING. MACHINE VIBRATIONS WILL BE SUBSTANTIALLY REDUCED, AND LOW SPECIFIC ENERGY WILL ALLOW THE USE OF SIC WHEELS, MAKING THE GRINDING PROCESS MORE ECONOMICAL.