Patent Application
20240308015
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 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 tooling 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. A particulate slurry comprising a mixture of hard and/or 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 particles held in the particulate slurry between the tool and the workpiece to impact the workpiece surface causing material removal by microchipping. Since actual machining is carried out by the particles, the tool can be softer than the workpiece.
The UIG process has matured to offer true three-dimensional machining capability to process a wide variety of engineering materials including ceramics and hard metals. An important application of UIG is for drilling through holes and blind holes and for machining of slots and pockets. Hole drilling always stands as the most popular machining process for product manufacturing, and UIG shows a high potentiality in fabricating diverse holes, especially those with small diameters and high aspect ratios on hard and brittle materials, such as CMCs. However, despite all favorable attributes of UIG, its application has been limited due to very low material removal rates.
A method for machining a workpiece includes orienting a first ultrasonic impact grinding tool head relative to the workpiece such that a tip of the first ultrasonic impact grinding tool head is spaced from a surface of the workpiece above a first work zone of the workpiece. A first nozzle supplies a first portion of a particulate slurry to the first work zone on the workpiece. A second ultrasonic impact grinding tool head is oriented relative to the workpiece such that a tip of the second ultrasonic impact grinding tool head is spaced from the surface of the workpiece above a second work zone of the workpiece. A second nozzle supplies a second portion of the particulate slurry to the second work zone on the workpiece. The tip of the first ultrasonic impact grinding tool head is vibrated and the tip of the second ultrasonic impact grinding tool head is vibrated.
An ultrasonic impact grinding assembly includes a base with a mount for connecting a workpiece to the base and a first tool arm. The ultrasonic impact grinding assembly also includes a second tool arm. The first tool arm and the second tool arm each include a base end, a distal end, at least one joint between the base end and the distal end, and at least one actuator configured to move the at least one joint. A first ultrasonic impact grinding tool head is connected to the distal end of the first tool arm. A second ultrasonic impact grinding tool head is connected to the distal end of the second tool arm.
A method for machining a workpiece comprising ceramic matrix composite includes orienting a first ultrasonic impact grinding tool head relative to the workpiece such that a first tip of the first ultrasonic impact grinding tool head is positioned over a surface of the workpiece without contacting the surface of the workpiece. A first nozzle delivers a first supply of particulate slurry between the surface of the workpiece and the first tip. The first tip is vibrated along a longitudinal axis of the first tip to cause particles in the first supply of particulate slurry to vibrate and cut a first feature in the surface of the workpiece. A second ultrasonic impact grinding tool head is oriented relative to the workpiece such that a second tip of the second ultrasonic impact grinding tool head is positioned over the surface of the workpiece without contacting the surface of the workpiece. A second nozzle delivers a second supply of particulate slurry between the surface of the workpiece and the second tip. The second tip is vibrated along a longitudinal axis of the second tip to cause particles in the second supply of particulate slurry to vibrate and cut a second feature in the surface of the workpiece.
The present summary is provided only by way of example, and not limitation. Other aspects of the present disclosure will be appreciated in view of the entirety of the present disclosure, including the entire text, claims and accompanying figures.
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.
One way to improve productivity and yield of ultrasonic impact grinding (UIG) is to machine multiple features simultaneously with specially designed machine assemblies. The present disclosure is directed to UIG assemblies with multiple UIG tool heads that coordinate together to machine multiple features or holes into a workpiece at the same time.
Anchoring flanges 26 extend from bottom plate 18 and can be used to anchor fixed frame 12 to a floor. First rail 20 and second rail 22 are connected to bottom plate 18 and are spaced apart from one another. First rail 20 and second rail 22 extend parallel to each other and form a track for gantry 14. Pedestal 24 extends upward from bottom plate 18 and is positioned between first rail 20 and second rail 22. Base 28 is connected to the top surface of pedestal 24 and includes mount 30 for connecting and securing workpiece W to UIG assembly 10 for machining. In the example of
Gantry 14 is connected to first rail 20 and second rail 22 such that gantry 14 slidably moves on first rail 20 and second rail 22 of fixed frame 12. First support beam 32 extends upward from first rail 20, second support beam 34 extends upward from second rail 22, and crossbeam 36 extends from first support beam 32 to second support beam 34. First gantry actuator 38 connects a base end of first support beam 32 to first rail 20 and second gantry actuator 40 connects second support beam 34 to second rail 22. First gantry actuator 38 and second gantry actuator 40 work in unison to move gantry 14 along first rail 20 and second rail 22. First gantry actuator 38 and second gantry actuator 40 can each comprise a motor and mechanisms to drive gantry 14 on first rail 20 and second rail 22. In other examples, a single gantry actuator can move gantry 14 on first rail 20 and second rail 22. First tool arm 16a, second tool arm 16b, and third tool arm 16c are each connected to crossbeam 36 of gantry 14 and carry first UIG tool head 42a, second UIG tool head 42b, and third UIG tool head 42c respectively. As discussed below with reference to
As shown in
Second link 48, as shown in
Third link 52 is connected to an end of second link 48 by third actuator assembly 54, which forms a joint between second link 48 and third link 52. Third actuator assembly 54 can include a servo motor, gearing, bearings, or a combination thereof to rotate third link 52 about a shared center axis of second link 48 and third link 52. Third link 52 can be shaped as a clevis to receive fourth link 56 and house fourth actuator assembly 58. Fourth actuator assembly 58 is at a joint between fourth link 56 and third link 52. Fourth actuator assembly 58 connects fourth link 56 to third link 52 and causes fourth link 56 to rotate about an axis of the clevis of third link 52. Fourth link 56 forms a distal end of third tool arm 16c. Fifth actuator assembly 60 connects third UIG tool head 42c to fourth link 56. Fifth actuator assembly 60 can be a linear actuator that moves third UIG tool head 42c along a central axis of third UIG tool head 42c. Fifth actuator assembly 60 can make small adjustments to move third UIG tool head 42c toward and away from workpiece W without having to move the rest of third tool arm 16c. As discussed below with reference to
As shown in
UIG assembly 10, through UIG tool head 42, inputs electrical energy to transducer 68 which is converted to mechanical vibrations along longitudinal axis LA at high frequency (usually 20-40 kHz). When energized, transducer 68 transmits vibrational energy to tool tip 62 via horn 70. While UIG assembly 10 is in use and while tool tip 62 is positioned over a surface of workpiece W and is powered and vibrating, supply tube 66 and nozzle 64 supply particulate slurry 74 with particles 72 into a gap between workpiece W and tool tip 62. Supply tube 66 can be connected to a pump (not shown) that supplies the particulate slurry from a supply reservoir (not shown). Particulate slurry 74 includes particles 72 suspended in a liquid (generally oil or water). Particles 72 can comprise a hard and/or abrasive material, such as diamond or boron carbide. Vibration of tool tip 62 transmits energy into particulate slurry 74 to propel particles 72 at high velocity between tool tip 62 and workpiece W such that particles 72 impact and chip the surface of workpiece W to form feature 76. Feature 76 can be a through hole, a slot, a groove, or any other recessed feature in the surface of workpiece W. In addition to providing particles 72 for chipping feature 76 into the surface of workpiece W, particulate slurry 74 also flushes away debris from feature 76 and a working zone of tool tip 62.
Workpiece W can be formed of a CMC material. Workpiece W can be, for example, a SiC/SiC CMC having silicon carbide fibers disposed in a silicon carbide matrix. Because UIG assembly 10 incorporates multiple UIG tool heads 42, UIG assembly 10 is able to work on multiple workpieces W at time, as shown in
Side surface 124 of cylindrical drum 118 extends axially between top end 120 and bottom end 122 and extends circumferentially around cylindrical drum 118. First rail 126 and second rail 128 are connected to side surface 124 and are spaced apart from one another axially and extend circumferentially around cylindrical drum 118. First rail 126 and second rail 128 extend parallel to each other and form a track for first tool arm 116a, second tool arm 116b, and third tool arm 116c. Pedestal 130 extends upward from top end 120 of cylindrical drum 118. Base 162 is connected to a top surface of pedestal 130 and includes mount 164 for connecting and securing workpiece W to UIG assembly 110 for machining. In the example of
First tool arm 116a, second tool arm 116b, and third tool arm 116c are each connected to first rail 126 and second rail 128 and are configured to move on first rail 126 and second rail 128. In the example of
First link 132 of first tool arm 116a extends upward from cylindrical drum 118. Second link 136 is connected to first link 132 by second actuator assembly 138. Second actuator assembly 138 moves second link 136 up and down along a length of first link 132. Second actuator assembly 138 can include a motor, gearing (such as a rack and pinion), track, bearings, rollers, belts, or any combination thereof. Second actuator assembly 138 can include any mechanism that can move second link 136 in a linear motion along first link 132. Second actuator assembly 138 allows first tool arm 116a to move UIG tool head 154 and UIG tool 156 (both shown best in
In the example of
Fourth link 144 is connected at or near a distal end of third link 140 by fourth actuator assembly 146. Fourth actuator assembly 146 forms a rotational joint between fourth link 144 and third link 140 such that fourth link 144 can rotate around a central axis of fourth link 144. Fourth actuator assembly 146 can include a servo motor, gearing, bearings, or a combination thereof to rotate fourth link 144 about the center axis of fourth link 144. Fourth link 144 is shaped as a clevis to receive fifth link 148 and house fifth actuator assembly 150. Fifth actuator assembly 150 is at a joint between fourth link 144 and fifth link 148. Fifth actuator assembly 150 connects fifth link 148 to the clevis of fourth link 144 and causes fifth link 148 to rotate about an axis of the clevis of fourth link 144. Fifth actuator assembly 150 allows first tool arm 116a to adjust an angle of UIG tool head 154 and UIG tool 156 (both shown best in
As shown best in
As discussed with reference to
UIG assembly 110 also orientates UIG tool head 154 of second tool arm 116b relative to workpiece W such that a tip of UIG tool 156 of second tool arm 116b is positioned in a second work zone over the surface of workpiece W without contacting the surface of workpiece W. The second work zone where second tool arm 116b is forming a feature is a leading edge of workpiece W. A second supply or portion of particulate slurry is delivered between the surface of workpiece W and the tip of UIG tool 156 of second tool arm 116b. The tip of UIG tool 156 of second tool arm 116b is vibrated along a longitudinal axis of UIG tool 156 to cause particles in the second supply or portion of particulate slurry to vibrate and cut a second feature on workpiece W. UIG assembly 110 also orientates UIG tool head 154 of third tool arm 116c relative to workpiece W such that a tip of UIG tool 156 of third tool arm 116c is positioned in a third work zone over the surface of workpiece W without contacting the surface of workpiece W. The third zone where third tool arm 116c is forming a feature is suction side of workpiece W. A third supply or portion of particulate slurry is delivered between the surface of workpiece W and the tip of UIG tool 156 of third tool arm 116c. The tip of UIG tool 156 of third tool arm 116c is vibrated along a longitudinal axis of UIG tool 156 to cause particles in the third supply or portion of particulate slurry to vibrate and cut a third feature on workpiece W. Since UIG assembly 110 can simultaneously machine multiple features into workpiece W, UIG assembly 110 can machine workpiece W faster than a traditional UIG machine.
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, such as to encompass ordinary manufacturing tolerance variations, incidental alignment variations, transient alignment or shape variations induced by thermal, rotational or vibrational operational conditions, and the like. 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.
The following are non-exclusive descriptions of possible embodiments of the present invention.
A method for machining a workpiece includes orienting a first ultrasonic impact grinding tool head relative to the workpiece such that a tip of the first ultrasonic impact grinding tool head is spaced from a surface of the workpiece above a first work zone of the workpiece. A first nozzle supplies a first portion of a particulate slurry to the first work zone on the workpiece. A second ultrasonic impact grinding tool head is oriented relative to the workpiece such that a tip of the second ultrasonic impact grinding tool head is spaced from the surface of the workpiece above a second work zone of the workpiece. A second nozzle supplies a second portion of the particulate slurry to the second work zone on the workpiece. The tip of the first ultrasonic impact grinding tool head is vibrated and the tip of the second ultrasonic impact grinding tool head is vibrated.
The method 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 ultrasonic impact grinding assembly includes a base with a mount for connecting a workpiece to the base and a first tool arm. The ultrasonic impact grinding assembly also includes a second tool arm. The first tool arm and the second tool arm each include a base end, a distal end, at least one joint between the base end and the distal end, and at least one actuator configured to move the at least one joint. A first ultrasonic impact grinding tool head is connected to the distal end of the first tool arm. A second ultrasonic impact grinding tool head is connected to the distal end of the second tool arm.
The 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:
A method for machining a workpiece comprising ceramic matrix composite includes orienting a first ultrasonic impact grinding tool head relative to the workpiece such that a first tip of the first ultrasonic impact grinding tool head is positioned over a surface of the workpiece without contacting the surface of the workpiece. A first nozzle delivers a first supply of particulate slurry between the surface of the workpiece and the first tip. The first tip is vibrated along a longitudinal axis of the first tip to cause particles in the first supply of particulate slurry to vibrate and cut a first feature in the surface of the workpiece. A second ultrasonic impact grinding tool head is oriented relative to the workpiece such that a second tip of the second ultrasonic impact grinding tool head is positioned over the surface of the workpiece without contacting the surface of the workpiece. A second nozzle delivers a second supply of particulate slurry between the surface of the workpiece and the second tip. The second tip is vibrated along a longitudinal axis of the second tip to cause particles in the second supply of particulate slurry to vibrate and cut a second feature in the surface of the workpiece.
The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
