Patent Application
20230191658
This disclosure relates generally to machining and, more particularly, to ultrasonic machining.
Ultrasonic machining may be used to form an aperture in a workpiece. Various systems and method for ultrasonic machining are known in the art. While these known ultrasonic machining systems and methods have various benefits, there is still room in the art for improvement. For example, during known methods, material removal rate may slow and a tool tip may wear down quickly from constant impact of abrasive particles due to micro erosion mechanisms during ultrasonic machining of deep apertures. There is a need in the art therefore for improved system and method for ultrasonic machining deep apertures in a workpiece.
According to an aspect of the present disclosure, a method is provided for machining a workpiece. During this machining method, an aperture is formed in the workpiece using a machining system. The machining system includes an ultrasonic machining device, a slurry delivery device and a controller. The forming of the aperture includes delivering a slurry to an interface between the ultrasonic machining device and the workpiece using the slurry delivery device, and transmitting ultrasonic vibrations into the slurry using the ultrasonic machining device. A feedback parameter is monitored during the forming of the aperture using the controller. A slurry delivery parameter for the slurry delivery device is adjusted during the forming of the aperture based on the feedback parameter using the controller.
According to another aspect of the present disclosure, another method is provided for machining a workpiece. During this machining method, a slurry is delivered to an interface between an ultrasonic machining device and the workpiece. Ultrasonic vibrations are transmitted into the slurry at the interface using the ultrasonic machining device to form an aperture in the workpiece. The slurry and debris from the forming of the aperture are extracted through a passage that extends within the ultrasonic machining device to a tip of the ultrasonic machining device.
According to still another aspect of the present disclosure, a machining system is provided for forming an aperture in a workpiece. The machining system includes a slurry delivery device, an ultrasonic machining device and a controller. The slurry delivery device is configured to deliver a slurry to an interface between the ultrasonic machining device and the workpiece. The ultrasonic machining device is configured to transmit ultrasonic vibrations into the slurry at the interface to form the aperture in the workpiece. The controller configured to: monitor a feedback parameter during the forming of the aperture; provide a control signal based on the feedback parameter; and communicate the control signal to the slurry delivery device to adjust a parameter of the delivery of the slurry to the interface.
The slurry and the debris may be drawn from the interface into the passage using a vacuum.
The method may also include: monitoring a feedback parameter during the forming of the aperture; and adjusting a slurry delivery parameter for the delivery of the slurry to the interface during the forming of the aperture based on the feedback parameter.
The workpiece may be configured from or otherwise include a ceramic matrix composite material.
The slurry may include a plurality of abrasive particles within a carrier liquid.
The plurality of abrasive particles may be configured from or otherwise include a carbide and/or diamond.
The slurry delivery parameter may be a pressure of the slurry.
The slurry delivery parameter may be a flowrate of the slurry.
The adjusting of the slurry delivery parameter may initiate flushing out of the slurry at the interface by directing the slurry through the ultrasonic machining device.
The slurry may be pumped through the ultrasonic machining device to the interface.
The slurry may be drawn out from the interface into the ultrasonic machining device.
The feedback parameter may be a load on the ultrasonic machining device.
The feedback parameter may be a forming rate of the aperture.
The feedback parameter may be a size of a tool of the ultrasonic machining device.
The slurry delivery parameter may be adjusted based on a physics-based model.
The slurry delivery device may include a passage that extends within the ultrasonic machining device to a tip of the ultrasonic machining device. The slurry may be delivered to the interface through the passage during the forming of the aperture.
The slurry delivery device may include a passage that extends within the ultrasonic machining device to a tip of the ultrasonic machining device. The slurry may be removed from the interface through the passage during the forming of the aperture.
The workpiece may be configured as or otherwise include a component of a gas turbine engine.
The present disclosure may include any one or more of the individual features disclosed above and/or below alone or in any combination thereof.
The foregoing features and the operation of the invention will become more apparent in light of the following description and the accompanying drawings.
The workpiece support 26 is configured to support the workpiece 24 during the forming of the aperture 22. The workpiece support 26 of
The slurry delivery device 27 is configured to deliver a liquid slurry to an interface 34 at a gap 35 between an ultrasonic machining tool 36 (e.g., a bit) of the ultrasonic machining device 28 and a location on the workpiece 24 where the aperture 22 is to be formed. The slurry delivery device 27 of
The slurry delivery device 27 may continuously (or intermittently) provide the slurry to the tool-workpiece interface 34 during the forming of the aperture 22. By providing the slurry to the tool-workpiece interface 34 throughout the forming of the aperture 22, the slurry delivery device 27 may displace previously used slurry at the tool-workpiece interface 34 with fresh slurry from the source 38. This at least partial (or complete) replacement of the slurry at the tool-workpiece interface 34 may remove debris generated as a byproduct from the forming of the aperture 22, where the debris may be carried away with the displaced used slurry. The slurry delivery device 27 is therefore also configured to remove the debris from the tool-workpiece interface 34.
The slurry includes a plurality of abrasive particles suspended within and/or otherwise carried by a carrier liquid. The abrasive particles may include carbide particles such as silicon carbide particles and/or boron carbide particles or diamond particles. Examples of the carrier liquid may include water and/or oil.
The ultrasonic machining device 28 is configured to generate ultrasonic vibrations (e.g., vibrations with a frequency equal to or greater than 20 kHz) and transmit those ultrasonic vibrations via sound waves into the slurry at the tool-workpiece interface 34. Referring to
The ultrasonic machining device 28 of
Referring to
In step 402, the workpiece 24 is positioned with the workpiece support 26.
In step 404, the aperture 22 is formed in the workpiece 24. The slurry delivery device 27, for example, directs a flow of the slurry to the tool-workpiece interface 34 through, for example, the nozzle 40. This flow of the slurry may maintain a minimum quantity of the slurry at the tool-workpiece interface 34 such that the gap 35 between the tool tip 58 and the workpiece 24 remains full of the slurry. The flow of the slurry may also maintain a flow (e.g., a current) of the slurry into, through and out of the gap 35 between the tool tip 58 and the workpiece 24. While this slurry is present at, and/or flowing through, the tool-workpiece interface 34, the machining tool 36 generates the ultrasonic vibrations and transmits those ultrasonic vibrations into the slurry at the tool-workpiece interface 34 towards the workpiece 24. These ultrasonic vibrations excite movement of the abrasive particles within the slurry such that at least some of the abrasive particles repetitively contact and vibrate against the workpiece 24 at the tool-workpiece interface 34. This vibratory contact between the abrasive particles and the workpiece 24 may form microfractures in the workpiece material and erode away the workpiece material at the tool-workpiece interface 34. The aperture 22 may thereby be formed (e.g., machined) at the tool-workpiece interface 34 in the workpiece 24.
A formation rate (e.g., machining speed) of the aperture 22 into the workpiece 24 may depend on various parameters. These parameters may include, but not limited to:
A decrease in the formation rate may be caused at least in part to a decrease in a concentration of the abrasive particles in the gap 35 between the tool tip 58 and the workpiece 24 at the tool-workpiece interface 34. For example, as the tool penetration depth (e.g., the aperture depth) increases, it may be more difficult for the fresh slurry to flow into the partially formed aperture as well as more difficult for the used slurry with the debris to flow out of the partially formed aperture. In addition, as the same abrasive particles remain in the gap 35 between the tool tip 58 and the workpiece 24 at the tool-workpiece interface 34, those abrasive particles may decrease in size, become dull and/or otherwise wear. The worn abrasive particles may thereby become less efficient at machining away the workpiece material.
To mitigate or prevent the reduction of the aperture formation rate as the tool penetration depth (e.g., the aperture depth) increases, the machining system 20 of
The control system 74 is configured to monitor one or more feedback parameters for the machining system 20 during machining system operation and, in particular, during the forming of the aperture 22 in the workpiece 24. The control system 74 is also configured to provide control signals to one or more components 27 and 28 of the machining system 20 in order to control operation of one or more of those machining system components 27 and 28. At least some of these control signals may be generated based on the monitored feedback parameters. The control system 74 may thereby implement feedback control of the machining system 20 and its components 27 and 28. The control system 74 of
The sensor system 76 is configured to sense one or more operational characteristics; e.g., variables, values, etc. These operational characteristics may include or may be indicative of the feedback parameters. Examples of the feedback parameters may include:
The sensor system 76 may include one or more sensors 84. Examples of these sensors 84 include, but are not limited to, a pressure sensor, a force sensor, a flow meter, a position sensor and a dimension measurement device.
The controller 78 is configured to generate and provide the control signals to the machining system components 27, 28 and 76. Some of these control signals may be generated using (e.g., closed-loop) feedback control logic. For example, controller 78 may monitor one or more of the feedback parameters to determine the (e.g., real time) formation rate of the aperture 22. Where the aperture formation rate is equal to or less then a threshold, the controller 78 may signal one or more of the machining system components 27 and 28 to adjust an operational parameter. This process may be repeated until the aperture formation rate rises above the threshold and/or another one or more thresholds are met.
The controller 78 may be implemented with a combination of hardware and software. The hardware may include memory 86 and at least one processing device 88, which processing device 88 may include one or more single-core and/or multi-core processors. The hardware may also or alternatively include analog and/or digital circuitry other than that described above.
The memory 86 is configured to store software (e.g., program instructions) for execution by the processing device 88, which software execution may control and/or facilitate performance of one or more operations such as those described in the methods below. The memory 86 may be a non-transitory computer readable medium. For example, the memory 86 may be configured as or include a volatile memory and/or a nonvolatile memory. Examples of a volatile memory may include a random access memory (RAM) such as a dynamic random access memory (DRAM), a static random access memory (SRAM), a synchronous dynamic random access memory (SDRAM), a video random access memory (VRAM), etc. Examples of a nonvolatile memory may include a read only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a computer hard drive, etc.
In step 502, one or more of the feedback parameters are determined. The sensor system 76, for example, may sense one or more of the operational characteristics and generate sensor data indicative of/based on the sensed operational characteristics. This sensor data is then communicated to the controller 78. This sensor data may include or be indicative of the feedback parameters. Where the sensor data is indicative of the feedback parameters (e.g., further processing is needed to determine the feedback parameters), the controller 78 may process the sensor data to determine the feedback parameters.
In step 504, one or more of the feedback parameters are monitored. The controller 78, for example, may monitor the feedback parameter associated with the spatial position of the machining tool 36 and its tool head 72. A change of the spatial position (e.g., downwards in
In step 506, where the aperture formation rate is less than a formation rate threshold, the controller 78 may trigger a (e.g., adaptive) response. The controller 78, for example, may signal the slurry delivery device 27 to adjust one or more slurry delivery parameters. For example, the controller 78 may signal the slurry delivery device 27 to increase a flowrate and/or a pressure of the slurry to the tool-workpiece interface 34. The increased flowrate and/or pressure may increase the quantity of fresh slurry directed into the gap 35 between the tool tip 58 and the workpiece 24 as well as increase the outflow of the used slurry and the debris carried thereby from the gap 35 between the tool tip 58 and the workpiece 24. This slurry replacement may increase a concentration of the abrasive particles within the slurry at the tool-workpiece interface 34 as well as replace dull abrasive particles with fresh sharp abrasive particles. The increase in the slurry flowrate may thereby increase machining efficiency and, thus, increase the aperture formation rate. A setpoint for the new increased flowrate of the slurry may be determined using a physics-based control model implemented by the controller 78.
In step 508, the control system 74 continues to monitor the aperture formation rate in real time during the forming of the aperture 22. Where the aperture formation rate is (or decreases) below the formation rate threshold (or another threshold), the slurry flowrate and/or pressure may be further increased. However, where the aperture formation rate is (or increases) a certain amount above the formation rate threshold (or another threshold), the slurry flowrate and/or pressure may be decreased. This process may be iteratively repeated during the formation of the aperture 22 until the aperture formation rate is within a desired range. The control system 74 may thereby implement automatic feedback control of the slurry delivery device 27 and flow of the slurry through the gap 35 between the tool tip 58 and the workpiece 24.
In some embodiments, where the aperture formation rate decreases below a second (e.g., minimum) formation rate threshold, the control system 74 may control the machining system components 27 and 28 to flush out the partially formed aperture in the workpiece 24. For example, referring to
In some embodiments, referring to
While various embodiments of the present disclosure have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the disclosure. For example, the present disclosure as described herein includes several aspects and embodiments that include particular features. Although these features may be described individually, it is within the scope of the present disclosure that some or all of these features may be combined with any one of the aspects and remain within the scope of the disclosure. Accordingly, the present disclosure is not to be restricted except in light of the attached claims and their equivalents.
