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MICRO ULTRASONIC ABRASIVE MACHINING SYSTEM

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MICRO ULTRASONIC ABRASIVE MACHINING SYSTEM

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    2. INTRODUCTION INTEREST IN HIGHER PRECISION MANUFACTURING ACTIVITIES PROBLEM WITH SMALLER TOOLS APPLICATION ON BRITTLE MATERIALS A PHYSICAL PROCESS

    3. ABOUT THE MACHINING SYSTEM

    4. PROBLEMS WITH ULTRSONIC MACHINING AND SOLUTION

    5. (A)TOOL BREAKAGE TOOL MATERIAL-WC COMPRESSIVE BREAKING LOAD=12N BUCKLING LOAD=0.42N d=50?m OPTIMUM MACHINING PRESSURE=10mN TOOL SHOULD BE APPLIED CORRECTLY FOR NO FRACTURE

    6. TOOL WEAR CAN BE AVOIDED BY TOOL ROTATION IF TOOL ROTATION IS ECCENTRIC: -CAUSES PARTIAL CONTACT WITH WORKPIECE -UNDESIRABLE FORCE IN TOOL RADIAL DIRECTION

    7. (B)MECHANISM OF APPLYING MACHINING PRESSURE MECHANISMS FOR MACHINING FORCE APPLICATION IN CONVENTIONAL SYSTEM: 1.HYDRAULIC HEAVY BOB MECHANISM -VIBRATION HEAD IS FIXED -USED IN SMALL MACHINES -APPLICATION OF UPWARD PRESSURE TO WORKPIECE TABLE BY HYDRAULIC CYLINDER 2.PARALLEL BALANCE HEAVY BOB MECHANISM -VIBRATION HEAD IS BALANCED BY BALANCING MECHANISM -USED IN LARGE MACHINING SYSTEM -MACHINING PRESSURE IS APPLIED BY THE BOB

    8. MINIMUM SETTABLE MACHINING FORCE -INCREASES DUE TO >BACKLASH OF MOVING PARTS >SLIDING FRICTION -IT EXCEEDS THE BUCKLING LOAD USE OF DYNAMOMETER -FOR CONSTANT MONITORING OF MACHINING FORCE USE OF NC FINE INFEED MECHANISM -TO CONTROL AMOUNT OF INFEED OF THE VIBRATION HEAD

    9. (C)SUPPLY OF ABRASIVE PARTICLES ONE LAYER OF ABRASIVE PARTICLES IS MUST AIR BUBBLES DUE TO CAVITATION: -DIAMETER BECOMES SIGNIFICANT FOR SMALL DIAMETER TOOL -AFFECTS MACHINING TOOL ROTATION

    10. MICRO ULTRASONIC ABRASIVE MACHINING SYSTEM

    12. (A)AEROSTATIC ULTRASONIC VIBRATION SPINDLE (VIBRATION HEAD)

    13. FED VERTICALLY BY SLIDING TABLE(Z-AXIS) DRIVEN BY BALL SCREWS AND AN AC SERVOMETER SUPPORTED BY AEROSTATIC BEARING OPTICAL NON CONTACT DISPLACEMENT METER TO MEASURE VIBRATION CHARACTERISTICS AT THE TIP OF HONE MOTION CONTROLLER-DMC1000,GALIL -A PC BASED MOTION CONTROLLER -TO CONTROL 3AXIS SIMULTANEOUSLY

    14. (B)MACHINING PRESSURE CONTROL DYNAMOMETER -ATTACHED TO XY-STAGE -CONTROL TOOL INFEED NUMERICALLY USING THE COMPUTER -MAINTAIN A CONSTANT MACHINING FORCE PIEZOELECTRIC DYNAMOMETER IS FOR MINIMUM SET MACHINING FORCE OF 10mN OR LARGER

    15. WHEN MINIMUM SET MACHINING FORCE IS LESS THAN 10mN: -INACCURACY IN MEASUREMENT COMES DUE TO DRIFT AND NOISE -A DOUBLE BEAM STRAIN GAUGE DYNAMOMETER IS USED MACHINING FORCE WAS MEASURED EVERY 10mS AT TOTAL OF 50 TIMES,AND AVERAGE OF THESE MEASUREMENTS WAS USED FOR MACHINING PRESSURE CONTROL

    16. (C)ON –MACHINE SHAPING OF SMALL DIAMETER TOOL TO GRIND FACE OF THE TOOL A DIAMOND WHEEL IS USED TORSIONAL ULTRASONIC VIBRATION -TO REDUCE GRINDING FORCE LANGEVIN TYPE VIBRATOR -GENERATE TORSIONAL VIBRATION HONE AND CONE AMPLIFY VIBRATION

    17. MACHINING EXPERIMENT

    18. (A)EXPERIMENTAL PROCEDURE DYNAMOMETER WAS INSTALLED ON XY-STAGE TRAY WAS FITTED ON DYNAMOMETER GLASS WORKPIECE WITH SiC SLURRY WAS PUT ON THE TRAY AND MACHINED SLURRY PREPARATION: -CENTRIFUGAL MIXING AND DEFOAMING SYSTEM WAS USED SLURRY WAS AGITATED BY AERATING THE SLURRY IN THE MACHINING AREA PERIODICALLY USING A SUPERFINE NOZZLE

    19. (B)DRILLING PROCESS POINT OF CONTACT WAS DETERMINED ABRASUVE SLURRY WAS FLOWN INTO THEMACHINING AREA AND CONSTANT PRESSURE MACHINING WAS DONE TOOL WAS THEN ROTATED VIBRATIONAL AMPLITUDE=15?m ABRASIVE PARTICLE SIZE=8?m SO,A SINGLE LAYER OF ABRASIVE PARTCLES WAS LIKELY TO BE PRESENT BETWEEN THE TOOL AND WORKPIECE ALL THE TIMES

    20. (C)INFLUENCE OF TOOL DIAMETER MICRO TOOLS OF 80,160,470 AND 730?m DIAMETER WERE PREPARED MACHINING SPEED OF SMALLER TOOL IS LOWER TOOL WEAR IS LONG FOR 80?m TOOL ABRASIVE PARTICLES GET REPELLED TOWARDS TOOL SIDES -PREVENT EFFECTIVE MACHINING -WEAR INCREASED -MACHINING SPEED DECREASED SO FURTHER INVESTIGATION IS REQUIRED FOR SELECTION OF APPROPRIATE ABRASIVE PARTICLE SIZE

    22. (D)EFFECT OF TOOL ROTATION RISE IS LEFT AT CENTRE OF HOLE PROTRUSION IS NOT FOUND FOR SMALLER TOOLS -BECAUSE OF WEAR AT TOOL TIP FOR LARGER TOOL PROTRUSION HEIGHT INCREASES WITH TIME BY TOOL ROTATION: -PROTRUSION HEIGHT REDUCED -RATE OF INCREASE REDUCED WHEN ROTATION SPEED=1000rpm,PROTRUSION HEIGHT REMAINED VIRTUALLY CONSTANT IMPROVED MACHINING SPEED

    23. APPLICATIONS MANUFACTURING OF ACEMENTED CARBIDE TOOL OF EXTREMELY SMALL DIAMETER BY WIRE EDM, WHICH HAS BEEN USED TO DRILL AHOLE OF 5?m IN DIAMETER IN SILICA GLASS AND SILICON IN OPTOELECTRICAL DEVICES OR MICRO-ELECTRO MECHANICAL SYSTEM TO MACHINE ANY MICROSIZED HOLES, APERTURES,ETC.

    24. ADVANTAGES ANY MICRO SIZED COMPONENTS CAN BE MACHINED BRITTLE MATERIAL CAN BE MACHINED A PHYSICAL PROCESS PROVISION FOR ON MACHINE SHAPING SYSTEM

    25. DISADVANTAGES DIFFICULTY IN SMALL DIAMETER TOOL MANUFACTURING FOR SMALLER TOOL MACHINING SPEED BECOMES WORSE AND TOOL WEAR INCREASES -CAN BE OVERCOME BY TOOL ROTATION MAINTAINING ADEQUATE SUPPLY OF ABRASIVE PARTICLE BETWEEN TOOL AND WORKPIECE IS DIFFICULT A COSTLY AFFAIR

    26. CONCLUSION MACHINING SPEED BECOMES AND TOOL WEAR INCREASES FOR A SMALLER TOOL PROTRUSION HEIGHT IS MORE FOR 730?m TOOL,AND IT INCREASES WITH TIME BY TOOL ROTATION PROTRUSION HEIGHT AND RATE OF INCREASE CAN BE REDUCED AT ROTATION OF 1000rpm,PROTRUSION HEIGHT WAS REDUCED TO HALF THE ORIGINAL,AND IT REMAINED VIRTUALLY CONSTANT WITH MACHINING TIME TOOL ROTATION APPROXIMATELY DOUBLED THE MACHINING SPEED,AND IT DID NOT DECREASE OVER TIME

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