Method for machining ceramic workpiece with composite vibration

Abstract

A method for machining a ceramic workpiece includes providing a sonotrode that has a transducer and a horn arranged along an axis, and the horn has helical slots and terminates at a tip, bringing the tip into proximity of the ceramic workpiece and providing an abrasive media to a work zone around the tip, using the transducer to produce ultrasonic vibration that axially propagates down the horn and causes axial vibration at the tip, and the helical slots convert a portion of the axial vibration to torsional vibration at the tip, and the axial vibration and the torsional vibration causing the abrasive media to abrade the ceramic workpiece in the work zone and thereby remove a localized portion of the ceramic workpiece.

What is claimed is: 
     
         1 . A method for machining a ceramic workpiece, the method comprising:
 providing a sonotrode that has a transducer and a horn arranged along an axis, and the horn has helical slots and terminates at a tip;   bringing the tip into proximity of the ceramic workpiece and providing an abrasive media to a work zone around the tip;   using the transducer to produce ultrasonic vibration that axially propagates down the horn and causes axial vibration at the tip, and the helical slots convert a portion of the axial vibration to torsional vibration at the tip;   the axial vibration and the torsional vibration causing the abrasive media to abrade the ceramic workpiece in the work zone and thereby remove a localized portion of the ceramic workpiece.   
     
     
         2 . The method as recited in  claim 1 , wherein the horn includes a first section that tapers and a second section that has a uniform cross-section, and the helical slots are on the second section. 
     
     
         3 . The method as recited in  claim 2 , wherein the second section is cylindrical and has a solid core. 
     
     
         4 . The method as recited in  claim 3 , wherein the second section has a diameter and each of the helical slots has a constant depth, and a ratio of the diameter to the constant slot depth is 5:1 to 10:1. 
     
     
         5 . The method as recited in  claim 3 , wherein the second section has a diameter and each of the helical slots has a slot length, and a ratio of the diameter to the slot length is 1:1 to 1:4. 
     
     
         6 . The method as recited in  claim 3 , wherein each of the helical slots has a constant depth and a slot length, and a ratio of the slot length to the constant slot depth is 5:1 to 20:1. 
     
     
         7 . The method as recited in  claim 3 , wherein the second section has a diameter and each of the helical slots has a slot length and a constant slot depth, and a ratio of the slot length to the constant slot depth divided by the diameter is 1:1 to 1:2. 
     
     
         8 . The method as recited in  claim 1 , wherein each of the helical slots defines a first slot end that is distal from the tip and a second slot end that is proximal to the tip, the first slot ends are located at a first common axial position, and the second slot ends are located at a second common axial position. 
     
     
         9 . The method as recited in  claim 7 , wherein the second common axial position is no more than 12.7 millimeters from the tip. 
     
     
         10 . The method as recited in  claim 7 , wherein the first slot end and the second slot end are circumferentially offset by 45° to 135°. 
     
     
         11 . The method as recited in  claim 1 , wherein the horn includes a first section that tapers and a second section that has a uniform cross-section, and the helical slots are on the first section. 
     
     
         12 . The method as recited in  claim 1 , wherein each of the helical slots defines an angle of 30° to 60° with the axis. 
     
     
         13 . The method as recited in  claim 1 , wherein the horn is a step horn. 
     
     
         14 . The method as recited in  claim 1 , wherein the ceramic workpiece is a ceramic matrix composite. 
     
     
         15 . An ultrasonic machining system comprising:
 a sonotrode that has a transducer and a horn arranged along an axis, the horn having helical slots and terminating at a tip, wherein upon operation, with the tip in proximity of a ceramic workpiece, the transducer produces ultrasonic vibration that axially propagates down the horn and causes axial vibration at the tip, the helical slots convert a portion of the axial vibration to torsional vibration at the tip, and the axial vibration and the torsional vibration cause an abrasive media in a work zone around the tip to abrade the ceramic workpiece and thereby remove a localized portion of the ceramic workpiece.   
     
     
         16 . The ultrasonic machining system as recited in  claim 15 , wherein the horn includes a first section that tapers and a second section that has a uniform cross-section, and the helical slots are on either the first section or the second section. 
     
     
         17 . The ultrasonic machining system as recited in  claim 16 , wherein the helical slots are on the second section, the second section has a diameter, each of the helical slots has a constant depth, each of the helical slots has a slot length, a ratio of the diameter to the constant slot depth is 5:1 to 10:1, and a ratio of the diameter to the slot length is 1:1 to 1:4. 
     
     
         18 . The ultrasonic machining system as recited in  claim 17 , wherein a ratio of the slot length to the constant slot depth is 5:1 to 20:1. 
     
     
         19 . The ultrasonic machining system as recited in  claim 15 , wherein each of the helical slots defines a first slot end that is distal from the tip and a second slot end that is proximal to the tip, the first slot ends are located at a first common axial position, and the second slot ends are located at a second common axial position. 
     
     
         20 . The ultrasonic machining system as recited in  claim 19 , wherein the second common axial position is no more than 12.7 millimeters from the tip, the first slot end and the second slot end are circumferentially offset by 45° to 135°, and each of the helical slots defines an angle of 30° to 60° with the axis.