METHOD AND ASSEMBLY FOR SLURRY DELIVERY AND UTILIZATION DURING ULTRASONIC IMPACT GRINDING

An ultrasonic impact grinding assembly includes a vessel having an open top disposed opposite a base and configured to contain an abrasive slurry, at least one mixing mechanism disposed in the vessel, a fixture disposed on the base of the vessel and configured to retain a workpiece for ultrasonic impact grinding within the abrasive slurry, and an ultrasonic impact grinding machine having a tool tip disposed to contact the abrasive slurry in the vessel during an ultrasonic impact grinding operation.

BACKGROUND

The present disclosure relates generally to machining ceramic matrix composites (CMCs) and, more particularly, to ultrasonic impact grinding (UIG).

Lightweight ceramic matrix composites (CMC) are highly desirable materials for gas turbine engine applications. CMCs, and particularly SiC/SiC CMCs (having silicon carbide matrix and fibers) exhibit excellent physical, chemical, and mechanical properties at high temperatures, making them particularly desirable for producing hot section components, including blade outer air seals (BOAS), vanes, blades, combustors, and exhaust structures. Like components made from other materials, it can be critical to the performance, durability, and function of the CMC component to cool the CMC component to maintain appropriate operating temperatures. Features for mitigating thermal stresses can include cooling channels provided through the material. There have been challenges in developing an efficient and cost-effective way to machine CMCs with high quality. SiC/SiC CMCs have a hardness second only to that of diamond and the SiC fiber reinforced phase results in anisotropy and heterogeneity.

UIG has been used to fabricate complex hole shapes with high aspect ratios on hard and brittle materials, such as CMCs. In UIG, electrical energy input to a transducer is converted to mechanical vibrations along a longitudinal axis at high frequency (usually at 20-40 kHz). The excited vibration is subsequently transmitted through an energy-focusing horn to amplify the vibration amplitude which is delivered to a tool tip. Thus, the tool, which locates directly above a workpiece, can vibrate along its longitudinal axis with a desired amplitude. An abrasive slurry comprising a mixture of abrasive material (e.g., diamond, boron carbide, etc.) suspended in water or oil is provided constantly into the machining area. The vibration of the tool causes the abrasive particles held in the slurry between the tool and the workpiece to impact the workpiece surface causing material removal by microchipping. Delivery of a continuous stream of abrasive slurry with sufficient and uniform flow between the ultrasonic tool and the workpiece is necessary for consistent machining. Challenges exist in providing sufficient and consistent delivery of abrasive slurry when machining features on a workpiece that requires 5-axis machining or orienting the tool tip at different angles relative to the workpiece surface. Abrasive slurry nozzles must be positioned in close proximity to the workpiece and tool tip to ensure delivery at the point of machining. Oftentimes, the workpiece must be repositioned to locate the machining surface below the tool tip to allow the abrasive slurry to pool at the point of machining. During the machining operation, the abrasive slurry is collected, filtered, mixed, and delivered back to the machining surface of the workpiece through the slurry nozzle.

While the UIG process has matured to offer true three-dimensional machining capability, improvements in the delivery of abrasive slurry are needed.

SUMMARY

An ultrasonic impact grinding assembly includes a vessel configured to contain an abrasive slurry, at least one mixing mechanism disposed in the vessel, the at least one mixing mechanism configured to agitate the abrasive slurry, a fixture disposed on a base of the vessel, and an ultrasonic impact grinding machine having a tool tip disposed to contact the abrasive slurry in the vessel during an ultrasonic grinding operation. The vessel is open at a top. The fixture is configured to retain a workpiece for ultrasonic impact grinding within the abrasive slurry.

A method for machining a ceramic workpiece includes submerging a machining surface of the ceramic workpiece in an abrasive slurry, positioning a tip of an ultrasonic impact grinding machine in proximity with the machining surface and into contact with the abrasive slurry, applying ultrasonic vibration to the tip, and agitating the abrasive slurry with a mixing mechanism disposed in the abrasive slurry.

While the above-identified figures set forth embodiments of the present invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the invention. The figures may not be drawn to scale, and applications and embodiments of the present invention may include features, steps and/or components not specifically shown in the drawings.

DETAILED DESCRIPTION

The present disclosure provides an improved method and assembly for abrasive slurry delivery and utilization during ultrasonic impact grinding (UIG) processes, which can allow for efficient and consistent machining regardless of the orientation of a UIG tool tip and machining surface of a workpiece. As disclosed herein, the machining surface of the workpiece is submerged in an abrasive slurry bath during the UIG operation. Use of the abrasive slurry bath eliminates the need to deliver the abrasive slurry to the machining surface through a delivery nozzle and reduces the need to reposition the workpiece to maintain a sufficient flow of abrasive particles between the UIG tool tip and the machining surface. The disclosed UIG apparatus allows multiple machining surfaces to be simultaneously submerged and covered by abrasive particles.

FIG.1is a side view of a UIG sonotrode10configured to vibrate along longitudinal axis LA during a UIG operation to remove material from a workpiece. Sonotrode10includes transducer12, horn14, and tool tip16. Horn14is disposed between transducer12and tool tip16. Electrical energy is input to transducer12, which is converted to mechanical vibrations along longitudinal axis LA at high frequency (usually 20-40 Hz). Transducer12may include one or more piezoelectric elements that, when activated with electric current, produce vibrational waves that propagate axially along longitudinal axis LA. When energized, transducer12transmits vibrational energy to tool tip16via horn14. Horn14is mechanically coupled to transducer12. Horn14can include multiple sections. Horn14has a converging portion configured to amplify a vibration amplitude delivered to tool tip16. Horn can include features such as helical slots (not shown) to convert a portion of axial vibration to torsional vibration, while limiting excitation of undesirable bending modes. Tool tip16is disposed at a distal end of sonotrode10. Tool tip16is configured to impart vibrational energy to an abrasive slurry between tool tip16and the machining surface of the workpiece as further described herein. Tool tip can be shaped to form a feature of desired geometry in the workpiece (e.g., a hole having a tapered cross-section). In some embodiments, sonotrode10can include a tool having multiple tips to form multiple features in the workpiece simultaneously. Sonotrode10is one example of a sonotrode and tool tip for use in the disclosed UIG apparatus. As will be understood by one of ordinary skill in the art, the disclosed UIG assembly is not limited to use with sonotrode10.

FIG.2is schematic view of UIG assembly20for machining workpiece22. As shown inFIG.2, UIG assembly20includes UIG machine24, vessel26, fixture28, protective layer30, actuating platform32, abrasive slurry34, and mixing mechanism36. Abrasive slurry34includes abrasive particles38. Vessel26includes base40and side wall(s)41. UIG machine24includes sonotrode10(not shown) ofFIG.1having tool tip16. UIG machine24can include, among other features not shown, an electric power source and actuating assembly configured to position tool tip16in varying locations along a surface of workpiece22. The actuating assembly can include, for example, a robotic arm or other mechanical linkages configured to provide 3-, 5-, or 7-axis machining. UIG assembly10can include controller42, such as a central processing unit of a computer, to coordinate movement of tool tip16relative to workpiece22and to coordinate movement of actuating platform32relative to tool tip16.

Vessel26is configured to contain abrasive slurry34and workpiece22. Vessel26is configured to provide an abrasive slurry bath for workpiece22such that a machining surface44of workpiece22is submerged during operation of UIG machine24. Vessel26can include base40disposed on actuating platform32. Vessel26can be affixed to actuating platform32to limit movement of vessel26relative to actuating platform32. In some embodiments, actuating platform32can form base40of vessel26. Vessel26is open at a top disposed opposite base40to provide UIG machine24with access to a top surface of workpiece22. Vessel26can be sized to allow movement of tool tip16relative to workpiece22in vessel26. Wall(s)41of vessel26can be spaced from workpiece22to allow UIG machine24to position tool tip16along side walls of workpiece22. Vessel26can have any suitable shape (e.g., cylindrical, rectangular, etc.). Vessel26can have a depth suitable for submerging workpiece22in abrasive slurry34and allowing left, right, forward, back, and angled translation of tool tip16, while containing abrasive slurry during operation. Vessel wall(s)41can be configured to keep machining surfaces44of workpiece22submerged during actuation of actuating platform32. Vessel26can be sized to contain a plurality of workpieces. For example, in some embodiments, vessel26can be configured to contain multiple workpieces22disposed in a side-by-side arrangement. In some embodiments, UIG assembly20can be configured to machine multiple workpieces simultaneously with a plurality UIG sonotrodes10(FIG.1). Vessel26can be formed of any suitable material for long-term containment of abradable slurry34.

Fixture28is affixed to vessel26. Fixture28can be disposed on and affixed to base40and/or side wall(s)41of vessel26. Fixture28is configured to retain workpiece22in vessel26and to prevent movement of workpiece22relative to vessel26during UIG operation and upon actuation of actuating platform32and tool tip16. Fixture28can secure workpiece22to allow six degrees of freedom of movement of workpiece22with actuating platform32. Fixture28can include a plurality of cylindrical dowel pins and/or rectangular pads and retention mechanisms as described further herein to limit movement of workpiece22in all directions. Fixture28can be configured to retain workpiece22while exposing a plurality of machining surfaces44.

Protective layer30is disposed on portions of fixture28configured to contact workpiece22. In some embodiments, protective layer30can cover all exposed surfaces of fixture28. Ultrasonic vibrations carried through workpiece22can cause wear at the workpiece/fixture interface. Protective layer30is configured to absorb vibrations carried through workpiece22(e.g., provide a cushioning effect) to prevent wear of fixture28by workpiece22. Protective layer30can additionally protect workpiece22and fixture28from damage by abrasive particles38. Protective layer30can be a sacrificial or replaceable film barrier. Protective layer30can be any material suitable for protecting workpiece22and fixture28and preventing abrasive particles38from lodging or moving between workpiece22and fixture28during UIG operation. Protective barrier30can be formed of a material capable of conforming to the surface of workpiece22and to the surface of fixture28to effectively seal an interface of workpiece22and fixture28from abrasive particles38. Protective layer30can comprise a polymer. Protective layer30can be, for example, a reinforced rubber having aramid fiber to provide stiffness. Protective layer30can be applied to fixture28prior to UIG operation and can be removed and replaced following UIG operation or as needed.

Workpiece22can be formed of a monolithic ceramic, a ceramic matrix composite (CMC), or combinations thereof. Workpiece22can be, for example, a monolithic silicon carbide (SiC) or silicon nitride (Si3N4). In other embodiments, workpiece22can be, for example, a SiC/SiC CMC having silicon carbide fibers disposed in a silicon carbide matrix. Alternatively, the fibers and/or matrix may be Si3N4. While the disclosed UIG assembly is particularly suited for improving the efficiency and throughput of ceramic and/or CMC manufacturing, it is not limited to use on monolithic ceramic or CMC workpieces or to particular ceramic or CMC materials. Workpiece22can be a component of a gas turbine engine. For example, workpiece22can be a blade outer air seal, vane, blade, combustor, and/or exhaust structure configured for use at high temperatures.

Abrasive slurry34comprises a mixture of abrasive particles38suspended in water or oil. Abrasive particles38comprise a material capable of cutting into, abrading, or chipping away material from workpiece22when projected at machined surface44by ultrasonic vibration. The material of abrasive particle38can be selected based on the material of workpiece22. Generally, abrasive particles38can have a hardness equal or greater than a hardness of the material of workpiece22. Abrasive particles38can be, for example, diamond, boron carbide, or silicon carbide.

Abrasive slurry34can be supplied to vessel26after workpiece22has been secured to fixture28. Abrasive slurry34can be provided to cover one or more machining surfaces44of workpiece22. A height of abrasive slurry above one or more machining surfaces44can vary depending on the geometry of workpiece22. UIG machine24is configured to place tool tip16into proximity with machining surface44without contacting machining surface44of workpiece22. A level of abrasive slurry34in vessel26is set to maintain a constant layer of abrasive slurry34and, particularly, abrasive particles38, between machining surface44and tool tip16. The vibration of tool tip16causes abrasive particles38held in the slurry between tool tip16and workpiece22to impact machining surface44of workpiece22causing material removal by microchipping. Since actual machining is carried out by abrasive particles38, tool tip16can be softer than workpiece22. Tool tip16can be disposed a distance from machining surface22selected based on an axial displacement of tool tip16along longitudinal axis LA. The distance can be selected to limit or prevent direct contact between tool tip16and machining surface44during UIG operation.

Abrasive slurry34can be added or removed from vessel26to control a height of abrasive slurry34above machining surface44. A height of abrasive slurry above machining surface44can impact machining efficiency as abrasive slurry34absorbs vibrational energy of tool tip16. Tool tip16can be disposed in abrasive slurry34throughout UIG operation. The design of tool tip16and design and integration of the power supply for UIG machine24can be provided to accommodate a variety of submersion depths.

With tool tip16disposed in proximity to workpiece22, transducer12(FIG.1) produces ultrasonic vibration that axially propagates down horn14(FIG.1) and causes axial vibration V1along longitudinal axis LA (FIG.1) at tool tip16. In some embodiments, a portion of the axial vibration V1can be converted into torsional vibration V2via features provided on the tool or horn14. The axial vibration V1and torsional vibration V2cause abrasive particles38between tool tip16and machining surface44to abrade workpiece22and thereby locally remove material from workpiece22as shown inFIG.2. As material is removed, tool tip16can be advanced further toward workpiece22along longitudinal axis LA to form a deeper hole in workpiece22, and/or can be translated along a surface of workpiece22to produce a slot or other feature along a surface of workpiece22. Tool tip16can be advanced further into abrasive slurry34as material is removed from machining surface44and tool tip16is advanced along longitudinal axis LA. In some embodiments, UIG machine24can be configured to move tool tip16along each of the x-, y-, and z-axis. UIG machine24can also be configured to rotate tool tip16about any one or more of the x, y-, and z-axis. For example, UIG machine24can be configured to machine a plurality of holes in workpiece22disposed at varying angles. In other examples, UIG machine24can be configured to rotate tool tip16(e.g., in drilling motion).

Actuating platform32can be configured to rotate vessel26and thereby workpiece22about the z-axis. In some embodiments, actuating platform32can be configured to rotate vessel26and thereby workpiece22about the x- and/or y-axis to tilt workpiece22(as illustrated by arrows46and48). As previously described, wall(s)41of vessel26can be designed to accommodate tilting of vessel26without spilling abrasive slurry34. Vessel26can be tilted to expose additional machining surfaces44of workpiece22to tool tip16while keeping the additional machining surfaces44submerged in abrasive slurry34. In some embodiments, actuating platform32can be configured to translate workpiece22within the x-y plane and/or along the z-axis to position machining surface44in proximity to tool tip16.

One or more mixing mechanisms36can be provided in vessel26to agitate abrasive slurry34and keep abrasive particles38in suspension, deliver new abrasive particles38to machining surface44, and to displace removed workpiece material from machining surface44. Without one or more mixing mechanisms36, abrasive particles38will settle via gravity to the bottom of vessel26and, thereby, reduce the amount of abrasive particles38present between tool tip16and machining surface44available for machining workpiece22.

Mixing mechanism36can be, for example, a pump having an inlet and outlet disposed in vessel26configured to agitate abrasive slurry34through constant or intermittent circulation of abrasive slurry34. Abrasive slurry34, including used abrasive particles38and material removed from workpiece22can be drawn through the pump to cause circulation of abrasive slurry34at machining surface44and, thereby, replacement of used abrasive particles38with new abrasive particles38.

In other embodiments, mixing mechanism36can be an ultrasonic transducer configured to agitate or mix abrasive slurry34via ultrasonic vibration. Mixing mechanism36can be, for example, an ultrasonic probe disposed in abrasive slurry34and separated from tool tip16and workpiece22so as not to interfere with machining operation or to cause abrasive particles38to impact workpiece22with sufficient force to cause microchipping.

In yet other embodiments, mixing mechanism36can be a mechanical agitator or stirring device. In yet other embodiments, mixing mechanism36can be any combination of one or more mechanical mixing mechanisms. It will be understood by one of ordinary skill in the art that mixing mechanism36can be any suitable device or combination of devices suitable for maintaining abrasive particles38in suspension and, particularly, between tool tip16and machining surface44, and to continuously replace used abrasive particles38and removed workpiece material between tool tip16and machining surface44with new abrasive particles38.

Mixing mechanism36can be affixed to vessel26to maintain a position of mixing mechanism36in vessel26or can be affixed to a body outside of vessel26such that mixing mechanism36can be moved as needed with actuation of actuating platform32and/or actuation of tool tip16.

Abrasive slurry34can become loaded with material removed from workpiece22during UIG operation. The loading of abrasive slurry34can be monitored throughout one or more UIG operations. Once a loading limit is reached, rendering the abrasive slurry34ineffective or inefficient for UIG operation, abrasive slurry34along with material removed from one or more workpieces22can be removed from vessel26. Abrasive slurry34can be recycled by removing the workpiece material via filtering.

FIG.3is a flow chart of method50for machining ceramic workpiece22using UIG assembly20. Method50can include one or more steps not shown.

In step52, workpiece22is secured to fixture28in vessel26. Fixture28can include a plurality of retention elements including, but not limited to cylindrical dowel pins, rectangular pads, and clamps. As previously described, workpiece22can be secured to a plurality of cylindrical dowel pins and/or pads to prevent movement of workpiece22in all directions relative to vessel26. Workpiece22can be secured to fixture28to allow workpiece22to move with vessel26with six degrees of freedom (e.g., workpiece22can be rotated and/or tilted with vessel26).

Protective layer30is applied to surfaces of fixture28configured to contact workpiece22. As previously described, protective layer30is a sacrificial layer or replaceable layer configured to absorb vibrational energy transmitted through workpiece22to protect fixture28from wear by workpiece22, and to prevent abrasive particles38from damaging workpiece22and fixture28at the workpiece/fixture interface. Protective layer30is applied to fixture28before workpiece22is secured to fixture28. Protective layer30can be replaced as needed between UIG operations following removal of workpiece22.

In step54, one or more machining surfaces44of workpiece22is submerged in abrasive slurry34. Depending on the shape and/or size of workpiece22and the location of one or more desired machining surfaces44, all or a subset of workpiece22can be submerged in abrasive slurry34. Workpiece22can be arranged on fixture28to locate one or more machining surfaces44near the surface of abrasive slurry34to limit a submersion depth of tool tip16in abrasive slurry34. Preferably, a depth of abrasive slurry34above machining surface44can be greater than ⅛ inch (0.318 cm) or greater than ¼ inch (0.635 cm)

In step56, tool tip16is positioned in proximity with machining surface44of workpiece22and in contact with abrasive slurry34. As previously described, tool tip16can be arranged in any orientation relative to machining surface44accommodated by vessel26and UIG machine24. For example, tool tip16can be oriented 20-30 degrees relative to machining surface44to form cooling holes in a component.

In step58, ultrasonic vibration is applied via transducer12and horn14to tool tip16. Ultrasonic vibration causes abrasive particles38in abrasive slurry34to impact machining surface44and abrade workpiece22. Abrasive particles38are driven to penetrate into the exposed working surface44and remove microchips of workpiece material. A combination of axial and torsional ultrasonic vibration can cut and smooth machining surface44. As ultrasonic vibration is applied, tool tip16can be advanced along longitudinal axis LA and/or translated along the x- and/or y-axis to form features (e.g., slot) in a surface of workpiece22. In some embodiments, vessel26can be rotated or tilted to move workpiece22relative to tool tip16during application of ultrasonic vibration.

In step60, abrasive slurry34is agitated with mixing mechanism36. Step60can occur simultaneously with step58to ensure abrasive particles38are provided between machining surface44and tool tip16. As previously described, mixing mechanism can include one or more devices configured to agitate or mix abrasive slurry to keep abrasive particles38in suspension, to replenish abrasive slurry34between machining surface44and tool tip16with new abrasive particles38, and to displace material removed from workpiece22. In one embodiment, agitating abrasive slurry34includes drawing abrasive slurry34through a pump having an inlet and outlet disposed in vessel26. In one embodiment, agitating abrasive slurry34can include applying ultrasonic vibrational energy to abrasive slurry34in vessel26at a location separated from tool tip16and machining surface44. In some embodiments, one or more of the same or different mixing mechanisms36can be used to agitate or mix abrasive slurry34to ensure efficient UIG operation.

Vessel26can be rotated about one or more of the x-, y-, and z-axis to tilt workpiece22and/or turn workpiece22relative to tool tip16to position one or more new machining surfaces44in proximity to tool tip16. Alternatively, or additionally, tool tip16can be moved with 5 degrees of freedom (i.e., up and down on z-axis, left and right, forward and back, and rotated about both x- and y-axes) to position tool tip16in proximity to the new machining surface44.

As previously described with respect to actuating platform32ofFIG.2, actuating platform70is configured to rotate and tilt vessel78and thereby workpiece82. Swinging portion72is configured to swing or pivot about a fixed pin to tilt vessel78as shown inFIG.4. Rotating portion74is configured to rotate or turn vessel78about the z-axis. As previously described, walls of vessel78can be designed to accommodate tilting of vessel78without spilling abrasive slurry. Vessel78can be tilted to expose additional machining surfaces of workpiece82to a tool tip (not shown) while keeping the additional machining surfaces submerged in the abrasive slurry.

The disclosed UIG operation can be simultaneously performed on multiple workpieces22disposed in vessel26to improve throughput. Use of the abrasive slurry bath provides continuous flow of abrasive particles38between machining surface44and tool tip16regardless of the orientation of tool tip16and workpiece22.

The embodiments disclosed herein are intended to provide an explanation of the present invention and not a limitation of the invention. The present invention is not limited to the embodiments disclosed. It will be understood by one skilled in the art that various modifications and variations can be made to the invention without departing from the scope and spirit of the invention.

Although a combination of features is shown in the illustrated examples, not all features need to be combined to realize the benefits of various embodiments of this disclosure. For example, in some embodiments, actuating platform28can be a stationary platform or can be configured to only rotate about the z-axis (i.e., not tilt). A system designed according to an embodiment of this disclosure, therefore, will not necessarily include all of the features shown in the illustrated examples.

Any relative terms or terms of degree used herein, such as “substantially”, “essentially”, “generally”, “approximately” and the like, should be interpreted in accordance with and subject to any applicable definitions or limits expressly stated herein. In all instances, any relative terms or terms of degree used herein should be interpreted to broadly encompass any relevant disclosed embodiments as well as such ranges or variations as would be understood by a person of ordinary skill in the art in view of the entirety of the present disclosure. Moreover, any relative terms or terms of degree used herein should be interpreted to encompass a range that expressly includes the designated quality, characteristic, parameter or value, without variation, as if no qualifying relative term or term of degree were utilized in the given disclosure or recitation.

DISCUSSION OF POSSIBLE EMBODIMENTS

An ultrasonic impact grinding assembly includes a vessel configured to contain an abrasive slurry, at least one mixing mechanism disposed in the vessel, the at least one mixing mechanism configured to agitate the abrasive slurry, a fixture disposed on a base of the vessel, and an ultrasonic impact grinding machine having a tool tip disposed to contact the abrasive slurry in the vessel during an ultrasonic grinding operation. The vessel is open at a top. The fixture is configured to retain a workpiece for ultrasonic impact grinding within the abrasive slurry.

The ultrasonic impact grinding assembly of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:

An embodiment of the ultrasonic impact grinding assembly of the preceding paragraph can further include a protective layer disposed on surfaces of the fixture configured to contact the workpiece.

In an embodiment of the ultrasonic impact grinding assembly of any of the preceding paragraphs, the protective layer can include a polymer.

An embodiment of the ultrasonic impact grinding assembly of any of the preceding paragraphs can further include an actuating platform connected to the vessel and configured to rotate the vessel about at least one of an x-, y-, and z-axis to tilt the vessel and/or turn the vessel.

In an embodiment of the ultrasonic impact grinding assembly of any of the preceding paragraphs, the ultrasonic impact grinding machine can be configured to operate with six degrees of freedom.

In an embodiment of the ultrasonic impact grinding assembly of any of the preceding paragraphs, the vessel has a depth sufficient to contain the abrasive slurry when a machining surface of the workpiece is submerged in the abrasive slurry.

In an embodiment of the ultrasonic impact grinding assembly of any of the preceding paragraphs, the abrasive slurry can include a plurality of abrasive particles suspended in an aqueous solution and wherein the at least one mixing mechanism is configured to provide agitation sufficient to maintain a concentration of the abrasive particles between a machining surface of the workpiece and a tip of the ultrasonic impact grinding machine during ultrasonic impact grinding operation.

In an embodiment of the ultrasonic impact grinding assembly of any of the preceding paragraphs, the at least one mixing mechanism can be a pump having an inlet and an outlet disposed in the vessel.

In an embodiment of the ultrasonic impact grinding assembly of any of the preceding paragraphs, the at least one mixing mechanism can agitate the abrasive slurry by ultrasonic vibration.

In an embodiment of the ultrasonic impact grinding assembly of any of the preceding paragraphs, the vessel can be configured to contain a plurality of workpieces with machining surfaces submerged in the abrasive slurry.

A method for machining a ceramic workpiece includes submerging a machining surface of the ceramic workpiece in an abrasive slurry, positioning a tip of an ultrasonic impact grinding machine in proximity with the machining surface and into contact with the abrasive slurry, applying ultrasonic vibration to the tip, and agitating the abrasive slurry with a mixing mechanism disposed in the abrasive slurry.

The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations, additional components, and/or steps:

In an embodiment of the method of the preceding paragraph, agitating the abrasive slurry can include drawing the abrasive slurry through a pump having an inlet and an outlet disposed in a vessel containing the ceramic workpiece.

In an embodiment of the method of any of the preceding paragraphs, agitating the abrasive slurry can include applying ultrasonic vibrational energy to the abrasive slurry in a vessel containing the ceramic workpiece, wherein the mixing mechanism providing the ultrasonic vibrational energy to agitate the abrasive slurry is separate from the ultrasonic impact grinding machine.

An embodiment of the method of any of the preceding paragraphs can further include securing the ceramic workpiece to a fixture disposed in a vessel containing the abrasive slurry.

An embodiment of the method of any of the preceding paragraphs can further include providing a protective layer between the ceramic workpiece and the fixture, wherein the protective layer seals a contact interface of the ceramic workpiece and fixture from incursion of abrasive particles in the abrasive slurry.

An embodiment of the method of any of the preceding paragraphs can further include rotating a vessel containing the abrasive slurry and the ceramic workpiece about at least one of an x-, y-, and z-axis to tilt and/or turn the ceramic workpiece to position a new machining surface in proximity to the tip, wherein the new machining surface is submerged in the abrasive slurry.

An embodiment of the method of any of the preceding paragraphs can further include moving the tip with five degrees of freedom into proximity with a new machining surface of the ceramic workpiece, wherein the new machining surface is submerged in the abrasive slurry.