METHOD AND APPARATUS FOR LOW-PRESSURE ABRASIVE FLOW FINISHING

Abstract

A low-pressure abrasive flow tuning system includes a source of pressurized, Newtonian, low-viscosity flow media. A known-flow path conveys the media to and through a channel of a workpiece to regularize the channel for a predetermined flow rate. The system includes a flow meter that measures flow rate through the known-flow path and workpiece and/or pressure sensors disposed upstream and downstream of the workpiece that measure a drop in pressure through the workpiece. A monitoring and/or controller interface presents indications of the rates and pressures, and permits control of the flow rate through the system.

Description

BACKGROUND

Current surface finishing methods are time dependent and are focused on achieving a specific surface roughness level and removing a specified amount of material from the surface of a workpiece. For workpieces created by additive manufacturing (e.g., 3D printing), the issue with conventional processes is that they are based on the assumption that the initial tolerances from part to part are identical and that the determined material removal will be beneficial to the overall part.

Abrasive flow machining (AFM, also referenced as extrude honing) is a finishing process used to remove material from surfaces, typically in situations where more common, hard-tool finishing methods are not possible or applicable, such as interior channels or complex geometries that are difficult to reach with tools. In conventional AFM systems material is removed by flowing through the workpiece a high viscosity viscoelastic medium in which abrasive particles are suspended. The AFM process is commonly used to improve surface finish, deburr, radius edges, and polish intricate and complex shapes.

However, in critical flow regions such as injector orifices and heat exchanger cooling channels, overall flow rate and pressure drop are critical driving factors. If these factors are inconsistent, even by a small percentage, the performance can vary dramatically. This inconsistency in performance can be critical in certain applications such as in reaction engines, particularly in applications that use more than one engine, such as a rocket. This variance is driven in part by the degree of repeatable precision and accuracy of the production method used. Even very accurate 3D printer(s) used during production can be inaccurate from one print result to another. For example, in two injectors produced on the same laser powder bed fusion metal printer (currently one of the highest accuracy printer types available), the inventors observed a cross-section area variance of +0.23% to −5.5% on inner orifices (central area of build plate) and +7.95% to −14.77% on outer orifices (outer area of build plate) from one critical flow region (e.g., orifice) instance to another. Conventional surface finishing processes maintain these tolerance variances to the finalized parts because the same amount of material is removed from all surfaces.

AFM utilizes “abrasive flow media” or “abrasive media.” This media consists of a “carrier fluid,” which, conventionally, is a non-Newtonian, polymer-based material mixed with abrasive particles. The carrier fluid's viscosity and other properties can be adjusted to suit the specific requirements of the machining process, such as controlling the flow rate, pressure, viscosity, abrasive particle size, abrasive concentration, particle density, particle hardness, workpiece hardness, and the ability to carry and distribute abrasive particles effectively. However, the viscosity of the carrier fluid is high in conventional systems, such that abrasive flow of the medium commonly requires pressure in the range of 3,000 to 10,000 psi (20,685 to 68,950 kPa). Even so-called “low pressure AFM” in conventional systems utilizes pressures in that range (e.g., 3,000 to 6,000 psi (20,685 to 41,370 kPa)).

The carrier fluid in conventional AFM systems is non-Newtonian, i.e., a fluid that does not follow the linear relationship between shear stress and shear rate described by Newton's law of viscosity. In other words, the viscosity of the carrier fluid in conventional AFM systems can change with the applied stress or the rate of deformation. Certain non-Newtonian carrier “fluids” used in AFM have a viscosity that decreases as the shear rate (the rate of deformation or flow) increases. This allows the carrier fluid to flow more readily when subjected to higher shear rates. As the fluid flows through narrow channels, intricate geometries, and around complex workpiece surfaces, it can adapt to these shapes, ensuring that abrasive particles are evenly distributed.

SUMMARY OF THE DISCLOSURE

This Summary introduces a selection of concepts in a simplified form in order to provide a basic understanding of some aspects of the present disclosure. This Summary is not an extensive overview of the disclosure, and it is not intended to identify key or critical elements of the disclosure or to delineate the scope of the disclosure. This Summary merely presents some of the concepts of the disclosure as a prelude to the Detailed Description provided below.

According to an embodiment, a method is presented for regularizing a passage in a workpiece using a low-pressure abrasive flow tuning system. The method includes an operation of providing the low-pressure abrasive flow tuning system to provide a low-viscosity abrasive medium to at least one internal channel of a workpiece. The low-pressure abrasive flow tuning system is to regularize the flow of the internal channel. The low-pressure abrasive flow tuning system has a known-flow path, and the low-viscosity abrasive flow medium has a substantially linear ratio of shear stress to shear rate and including a carrier fluid throughout which an abrasive material is dispersed. Another operation of the method includes defining at least one of a design pressure drop or a flowrate of the low-viscosity abrasive medium when passed along the known-flow path and through a calibration orifice related to the desired flow in the internal channel of the workpiece. A workpiece having the internal channel is fitted to the known-flow path, and the low-viscosity abrasive flow medium is conveyed along the known-flow path and through the internal channel of the attached workpiece. The method further includes monitoring a flow rate of the low-viscosity abrasive flow medium through the internal channel of the workpiece using a flow meter disposed upstream of the workpiece and/or monitoring a pressure drop through the workpiece via pressure sensors disposed upstream and downstream from the workpiece, and stopping the flow of the low-viscosity abrasive flow medium through the internal channel of the workpiece when the flow rate of the low-viscosity abrasive flow medium through the workpiece is substantially the same as the design flow rate of the low-viscosity abrasive flow medium as determined by at least one of design pressure drop or flowrate.

According to an embodiment, a low-pressure abrasive flow tuning system includes a source of pressurized, low-viscosity flow media, a known-flow path, one or more sensors, and a controller. The low-viscosity flow media has a substantially linear ratio of shear stress to shear rate and includes a dispersed abrasive material provided in a carrier fluid. The known-flow path is configured to convey the low-viscosity abrasive flow media under pressure from the source to a workpiece, the known-flow path ending in a workpiece holder configured to connect to a channel of a workpiece and to direct the low-viscosity abrasive flow medium into the channel of the workpiece. The one or more sensors may be disposed along the known-flow path and are configured to measure a rate of flow of the low-viscosity flow media and/or a pressure drop of the media within the known-flow path passing through the channel of the workpiece of the low-pressure abrasive flow tuning system. The controller may be electrically connected to the one or more of the source of pressurized, low-viscosity abrasive flow media and one or more sensors. The controller determines a rate of flow of the low-viscosity flow media and/or a pressure drop of the media through the channel of the workpiece. The controller compares the rate of flow to a design flowrate of the low-viscosity abrasive flow media and/or compares the pressure drop of the low-viscosity abrasive flow media though the channel of the workpiece to a design pressure drop of the low-viscosity abrasive flow media.

According to an embodiment, a non-transient computer readable medium stores instructions which, when executed by one or more computer processors electrically connected to a low-pressure abrasive flow tuning system, cause a display associated with the computer processor to present a graphical user interface (GUI) for monitoring and controlling the low-pressure abrasive flow tuning system. The GUI includes at least a first pressure field, a second pressure field, a flow rate field, and a pressure control. The first pressure field is configured to display a first pressure received by the computer processor(s) from a first pressure sensor disposed upstream from a workpiece in the low-pressure abrasive flow tuning system. The second pressure field is configured to display a second pressure received by the computer processor(s) from a second pressure sensor disposed downstream from the workpiece in the low-pressure abrasive flow tuning system. The flow rate field is configured to display a flow rate of a low-viscosity Newtonian abrasive flow medium through the workpiece when the low-viscosity Newtonian abrasive flow medium is conveyed through the low-pressure abrasive flow tuning system. The flow rate is received by the computer processor(s) from a flow meter of the low-pressure abrasive flow tuning system. The pressure control is configured to control a pressure inducing mechanism in the low-pressure abrasive flow tuning system, the pressure inducing mechanism being configured to convey the low-viscosity Newtonian abrasive flow medium through the low-pressure abrasive flow tuning system and an internal channel of the workpiece attached to the low-pressure abrasive flow tuning system.

While multiple embodiments are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. As will be realized, the invention is capable of modifications in various aspects, all without departing from the scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-described objects and other objects, features and characteristics of the present disclosure will become more apparent to those skilled in the art from a study of the following Detailed Description in conjunction with the appended claims and drawings, all of which form a part of this specification. In the drawings:

FIG. 1 is a block diagram of a low-pressure abrasive flow tuning system, according to an embodiment;

FIG. 2A is a block diagram of a low-pressure abrasive flow tuning system with a calibration orifice, according to an embodiment;

FIGS. 2B, 2C illustrate a cross section portion of a channel of a workpiece, according to an embodiment;

FIG. 3 illustrates a low-pressure abrasive flow tuning system with a workpiece, according to an embodiment;

FIG. 4 depicts a portion of a channel in a workpiece, according to an embodiment;

FIG. 5 depicts a portion of a channel in a workpiece with an ultrasonic transducer, according to an embodiment;

FIG. 6 illustrates a low-pressure abrasive flow tuning system with a workpiece with ultrasonic transducers, according to an embodiment;

FIG. 7 depicts a graphical user interface, according to an embodiment;

FIG. 8 is a flow chart illustrating a process of using a low-pressure abrasive flow tuning system, according to an embodiment; and

FIG. 9 is a flow chart illustrating a process of using a low-pressure abrasive flow tuning system with an etching process, according to an embodiment.

The above-described figures may depict exemplary configurations for a system or apparatus of the disclosure, which is done to aid in understanding the features and functionality that can be included in the systems described herein. The systems are not restricted to the illustrated architectures or configurations, but can be implemented using a variety of alternative architectures and configurations.

DETAILED DESCRIPTION

As discussed above, in certain cases the conventional approach of uniformly abrading all surfaces of a channel can be disadvantageous. Conventional AFM does not efficiently address the need for flow uniformity from one part's channel to another's and may require overbuilding a part to accommodate erosion of the entire channel.

In certain industries or applications, establishment of a predetermined flow rate through the interior channel of a workpiece at a particular pressure is sought, rather than merely smoothing the channel. For example, in the field of vehicle fuel delivery systems, achieving a particular fuel flow through a fuel delivery system may be desirable. A workpiece produced by additive manufacturing may require machining of its channel(s) to achieve such flow rate. With conventional AFM techniques, every workpiece created by additive manufacturing would require its own distinct, iterative process involving both machining the channel(s) thereof and testing the flow using a fluid intended for end use (e.g., fuel or coolant) in separate steps and then repeating these operations until the desired conditions are achieved. This process is inefficient, particularly when many parts are involved. The present disclosure addresses these shortcomings.

FIG. 1 is a block diagram of a low-pressure abrasive flow tuning system 100, according to an embodiment. The low-pressure abrasive flow tuning system 100 includes a source of pressurized, low-viscosity, abrasive flow media 110, a channel 130 configured to convey the low-viscosity abrasive flow media under pressure from the source of low-viscosity abrasive flow media 110, a flow meter 140, pressure sensors 150, 160, an end piece 170 affixed to the channel 130 for conveying the abrasive flow media 110, and a monitoring/control interface 180. The source of pressurized abrasive flow media 110 is configured to pressurize and supply a volume of the abrasive flow media through the channel 130 to an end piece 170. A flow rate of the abrasive media through the channel 130 may be monitored using the flow meter 140 disposed anywhere along the channel 130. A pressure sensor 150 may be disposed along the channel 130 to monitor pressure of the abrasive flow media within the channel 130. The end piece 170 may be affixed in fluid connection with the channel 130 to receive the flow of abrasive flow media. An exit opening 171 of the end piece 170 may be configured to release the abrasive flow media. A sensor 160 may be disposed at or near the exit opening 171, in some embodiments, and may be configured to determine pressure or flow rate of the abrasive flow media as it exits the end piece 170. The monitoring/control interface 180 may include communication interfaces (e.g., electrical, pneumatic, etc.) to at least one of: the source of pressurized abrasive flow media 110, the flow meter 140, and the pressure sensors 150, 160. The monitoring/control interface 180 may be configured to control power, pressure, and/or available media volume of the source of pressurized abrasive flow media 110. The monitoring/control interface 180 may be further configured to monitor one or more of a status of the source of pressurized abrasive flow media 110, a flow rate measure by the flow meter 140, pressure measured at the pressure sensor 150, and pressure or flow rate measured at the sensor 160.

FIG. 2A is a block diagram of a low-pressure abrasive flow tuning system 200, according to an embodiment. The low-pressure abrasive flow tuning system 200 corresponds to the low-pressure abrasive flow tuning system 100 of FIG. 1 and includes additional detail for particular embodiments. The tuning system 200 may include a tank 212 and a pressure inducer (e.g., a pump or piston) 220 together constituting a source of pressurized, low-viscosity abrasive flow media (e.g., 110), according to an embodiment. Tubing 230 constitutes a channel for conveying the abrasive flow media, and a volumetric flow meter 240 may correspond to the flow meter 140 of FIG. 1, while one or more pressure sensors 250, 260 correspond to the pressure sensor 150 and sensor 160 of FIG. 1. The end piece 270 may comprise a workpiece holder 272 and may alternately include a calibration orifice 273 and a workpiece 274. According to an embodiment, the flow tuning system 200 may further include a monitoring and control interface 280 having electrical interface to the pressure inducer 220, flow meter 240, and/or pressure sensors 250, 260. Those having skill in the art will acknowledge that the tuning system 200 may be configured using additional or alternative elements as discussed in paragraphs below for each listed element.

FIGS. 2B, 2C illustrate a cross section portion of a channel 275 in an exemplary workpiece 274. (Those having skill in the art will recognize that the illustrated channel 275 includes one of many possible channel configurations that benefit from the disclosed low-pressure abrasive flow tuning system 100.) FIG. 2B shows a flow (dash-dot arrows) of a low-viscosity abrasive flow medium 212 through the channel 275 without submersion of the workpiece 274, while FIG. 2C illustrates the flow of low-viscosity abrasive flow medium 212 through the channel 275 with submersion of the workpiece 274. In both instances the abrasive flow medium 212 increases speed at lower pressure through the channel 275. As the flow medium passes areas of resistance such as the corners 276, the abrasive material in the flow medium 212 erodes the corners 276 (erosion shown in dashed lines). Without submersion, the flow medium 212 is emitted from the end of the channel 275 at speed and erodes the corners 277 and a facing surface 278 as illustrated in FIG. 2B. This erosion of the facing surface 278 is typically undesirable and can result in unintended flow resistance. In contrast, when the workpiece is submerged as in FIG. 2C, the flow medium 212 ejected from the channel 275 is dispersed into the flow medium 212 already present in the channel from submersion. Consequently, the flow tuning operation dramatically decreases erosion of the facing surface 278.

The tank 210 may be sized and arranged to hold a low-viscosity flow medium 212 sufficient in volume to permit the outlet(s) of a calibration orifice 273 or workpiece 274 to be submerged in the low-viscosity abrasive flow medium 212 while a portion of the flow medium 212 is pumped through the pump 220, tubing 230, volumetric flow meter 240 and so forth and through the calibration orifice 273 or workpiece 274. The term “low viscosity” in reference to the present disclosure means viscosity in the range of 0-2000 centipoise (cP), e.g., less than the viscosity of SAE 60 motor oil. However, a viscosity range of 0-2500 cP might be utilized in some embodiments. In contrast, conventional AFM utilizes abrasive flow media having a high viscosity, e.g., 100,000 to 1,000,000 cP or higher (for reference, peanut butter to window caulking or higher viscosities). As contemplated in the present application, the low viscosity abrasive flow medium will be a carrier medium that is a Newtonian fluid with a dispersed abrasive medium. Examples of such a Newtonian fluid include water or motor oil. In one preferred embodiment, water is utilized. This use of Newtonian fluid differs from the use of high to very high viscosity, non-Newtonian flow media as is used in conventional AFM, to achieve the afore-mentioned uniform removal of material from a flow channel, which smoothes but does not achieve uniform flow characteristics. In contrast the use of low viscosity Newtonian fluid functions to produce uniform flow characteristic as is desired in accordance to the teachings of the present application.

In another embodiment of the low-viscosity abrasive flow tuning system 200, instead of the tank 210, the tuning system may employ means for circulating abrasive fluid media directly. For example, a closed system that circulates a fixed volume of abrasive media through a workpiece 174.

Although FIG. 2A and other figures illustrating embodiments of the low-pressure abrasive flow tuning system 200 show the calibration orifice 273 or workpiece 274 completely submerged, the openings from which the flow medium is expelled may be just below the top of the flow medium volume in the tank 210. The low-viscosity flow medium 212 may be a Newtonian fluid defined as a carrier fluid having a substantially linear ratio of shear stress to shear rate. The low-viscosity flow medium 212 may include a dispersed abrasive material, e.g., grit formed of particular-size particles of aluminum oxide, zirconium dioxide, or the like. The size of abrasive grit may be selected for a specific smoothness and can be iteratively applied in increasing smaller grit sizes to efficiently traverse from rough to smooth channel surface in less time than using only a single grit size. In such uses, the flow is monitored such that a grit size is changed before reaching an ultimately desired “target” flow rate. In this manner, the target flow rate is not overshot. The tank 210 may include an outlet 214 for fluid connection to the pump 220.

As the flow medium 212 has low viscosity, the abrasive carried by the flow medium 212 may settle out of the flow medium in the absence of agitation. Accordingly, the tank 210 may further include one or more agitating mechanisms 216 configured to agitate the flow medium 212. Exemplary agitation mechanisms 216 may include, but are not limited to, an aerator, a wiper configured to periodically traverse the bottom of the tank 210, a stirring bar magnetically coupled to an external magnetic driver, or the like. The agitation mechanism may also be an ultrasonic transducer having additional utility as described below. Those having skill in the art will recognize that, while not all of the figures showing the flow tuning system 200 depict an agitation mechanism 216, such mechanism may be included in any embodiment.

The pump 220 may include a pump inlet 222, a pump outlet 224, and a pump motor 226. In some embodiments, the pump 220 may include a pump controller 228 configured for controlling speed, power (on/off). The pump controller 228 may include a variable frequency drive (VFD) that controls the pump motor 226 by varying the frequency and voltage of a power supply of the pump 220. In some embodiments a portion of the pump controller 228 may output status information (e.g., power, speed, torque, and/or the like) to one or more indicators (not shown).

The pump 220 is controlled to produce a pressure of under 1000 psi, according to an embodiment. According to another embodiment the pump 220 is controlled to produce a pressure of 500 psi or less in the flow calibration orifice 273 and/or workpiece 274. According to another embodiment the pump 220 is controlled to produce a pressure of 200 psi or less in the flow calibration orifice 273 and/or workpiece 274. Notably, these pressures are substantially lower than pressures used in conventional AFM. This permits less (or in some instances no) mechanical machining of a workpiece 274 to ensure sufficiently robust mating with AFM machinery. Moreover, a workpiece 274 having delicate features and/or thin walls may be flow-tuned with the presently disclosed apparatus and methods whereas conventional AFM, with its much higher pressures and high viscosity flow media, would destroy a delicate and/or thin-walled workpiece. Further, the lower pressures permit the low-pressure abrasive flow tuning system 200 to be constructed with less concern regarding seals and element-to-element connections being able to withstand the pressures typical to conventional AFM.

In some embodiments the controller 228 may provide the status information to a monitoring and control interface 280. The pump inlet 222 may be attached in fluid communication with the tank 210 via the tubing 230. Operation of the pump pulls the low-viscosity flow medium 212 from the tank 210 into the pump inlet 222 and propels the low-viscosity flow medium 212 out the pump outlet 224 toward the end piece 270 via the tubing 230.

The tubing 230 may direct the low viscosity flow medium 212 from the pump 220 through the volumetric flow meter 240. The volumetric flow meter 240 may be configured to measure a volume per time of the flow of low viscosity flow medium 212.

The low-pressure abrasive flow tuning system 200 may further include one or more pressure sensors 250, 260. A first pressure sensor 250 may be disposed along the tubing 130 downstream from the volumetric flow meter 240 (i.e., between the flow meter 240 and the workpiece holder 270). A second pressure sensor 260 may be disposed downstream from workpiece holder 270. For example, a pressure sensor may be placed in the tank 210 at or near the outlet of a workpiece attached to the end piece 270 such that the difference between pressure at the first pressure sensor 250 and the second pressure sensor 260 may be monitored. According to an embodiment, the pressure sensors 250, 260 may be implemented as electronic or digital sensors configured to provide a pressure-representative signal. In other embodiments, one or both of the pressure sensors 250, 260 may include mechanical gauges. The inventors recognize that additional pressure sensors and/or flow meters may be placed at other locations to monitor pressures along the tubing 230, e.g., before and after the pump 220.

The workpiece holder 270 may include a structure for securing a workpiece to the tube 230, according to an embodiment. For some workpieces this might include a simple threaded coupling, while in others the structure of securing a workpiece may include one or more plumbing fittings or a manifold. The end piece 270 may include a fixture to which a workpiece may be secured such that one or more channels of the workpiece is in fluid connection with the tube 230 and substantially sealed against leakage at the connection between the workpiece and the fixture. The fixture may be a custom fixture corresponding to a specific workpiece or specific class of workpiece. For example, the fixture may comprise a manifold into which flow of the flow medium 212 is divided into plural channels corresponding to channels of the workpiece to be attached thereto. In practice, a fixture of the end piece 270 may specifically correspond to a workpiece for which the flow tuning is intended.

As described above, AFM tends to focus on smoothing without considering consistent flow metrics from one workpiece to another. The end piece 270 according to the present disclosure utilizes a flow calibration orifice 273, as illustrated in FIG. 2A, structured and tested to accommodate a predetermined flow rate of the liquid or gas for which a corresponding workpiece is targeted. For example, if a workpiece is intended for use in a fuel delivery system, the calibration orifice 273 is structured to accommodate a predetermined fuel flow rate for the fuel delivery system. The calibration orifice 273 may be used in the low-pressure abrasive flow tuning system 200 to determine a set point flow for the flow tuning system 200 for use in flow tuning the corresponding workpiece 274. The calibration orifice 273 is attached to the end piece 270 and the low viscosity flow medium 212 is pumped through it while a user monitors flow through the volumetric flow meter 240, and pressures at the pressure sensors 250, 260. As the calibration may be determined in short time period, the calibration orifice 273 is not significantly affected by the low viscosity flow medium 212. Alternatively, or additionally, the calibration orifice 273 may be composed of a material that is resistant to abrasion by the low viscosity flow medium 212.

FIG. 3 illustrates the low-pressure abrasive flow tuning system 200 with a workpiece 274. When the flow tuning system 200 is calibrated by use of the calibration orifice 273, the calibration orifice may be replaced by a workpiece 274 to be tuned by the flow tuning system 200. Once the workpiece 274 is in place, the flow tuning system 200 may be engaged, pumping the low viscosity flow medium 212 through the pump 220, tubing 230, flow meter 240, and pressure sensor 250. The outflow of the low-viscosity flow medium 212 from the workpiece 274 is measured by the pressure sensor 260. When the measured flow rate and pressures match the calibration set point within a predetermined threshold, the flow tuning system 200 may stop operation and the now-flow-tuned workpiece 274 can be replaced by a new untuned workpiece.

As illustrated in FIG. 4, as the low-viscosity flow media 212 traverses a channel 400 of a workpiece 274, uneven surfaces or pits 402 may cause turbulent flow 404 of the flow media 212. The turbulent flow 404 may limit the effectiveness of the low viscosity flow media 212 in such areas for smoothing the surface. Consequently, particles 410 (e.g., abrasive particles or removed media from the workpiece) may enter and be trapped in the uneven surfaces. FIG. 5 illustrates the portion of the workpiece 274 as in FIG. 4, with the addition of an ultrasonic transducer 500. The ultrasonic transducer 500 may be disposed and oriented to direct ultrasonic waves 502 to disturb and dislodge the trapped particles 410 and facilitate ejection thereof from the pits 402 into the flow of the flow media 212. This permits the flow media 212 to more efficiently smooth the uneven surfaces and pits 402. FIG. 6 illustrates an embodiment of the low-pressure abrasive flow tuning system 200 as described above, further including a plurality of the ultrasonic transducers 216, according to an embodiment.

The monitoring and control interface 280 may, according to an embodiment, provide a human-perceivable indicator corresponding to a signal received from one or more of: the pump controller 228, volumetric flow meter 240, pressure sensors 250, 260. For example, the monitoring and control interface 280 may control a visual indicator such as an LCD or LED and/or an audio indicator configured to notify the user when a predetermined condition is satisfied. The monitoring and control interface 280 may further include a control interface configured to modify operation of the pump 220. For example, the control interface of the monitoring and control interface 220 may include controls for powering the pump 210 on and off, and to control speed of the pump 220. In some embodiments, the monitoring and control interface 280 may apply logic or algorithm, based on inputs from one or more of: the volumetric flow meter 240, pressure sensor 250 and pressure sensor 260 in an algorithm for controlling the pump 220 via the pump controller 228. The monitoring and control interface 280 may additionally or alternatively provide manual controls for controlling the pump 220. The monitoring and control interface 280 may be receive signals from the pump 220, flow meter 240, and/or pressure sensors 250, 260 via wired or wireless connection. For example, each device providing a signal may transmit the signal via Wi-Fi, Bluetooth, Bluetooth LE, Zigbee, or proprietary wireless protocol. According to an embodiment, the monitoring and control interface 280 may include a general-purpose computer configured, via software, to execute operations for displaying a graphical user interface (GUI). The GUI may be configured to provide the above-described operations of the monitoring and control interface.

FIG. 7 illustrates a graphical user interface (GUI) 700, according to an embodiment. A non-transitory computer readable storage medium may include instructions which, when executed by a computer process may cause a display associated with the computer processor to present the GUI 700. The GUI 700 may include a graphical representation of an arrangement of controls, information displays, and/or indicators. The displayed controls, information displays and/or indicators may include instantiations that interactively change in response to user input or in response to data received from the low-pressure abrasive flow tuning system 200. For example, the GUI 700 may include controls 710 for controlling the pump 220 with a forward control 712, a reverse direction control 714, and a stop control 716. The GUI 700 may also include measurements and calculations 720, including at least a pressure 724 from the first pressure sensor 250, a pressure 722 from the second (downstream) pressure sensor 260, and a pressure drop calculation 728. In some embodiments that include an additional upstream pressure sensor (not illustrated), the GUI 700 may include a pressure 726 from such sensor. The GUI 700 may also include a flow rate field 730 configured to display a flow rate received by the computer processor from the volumetric flow meter 240. The GUI may include a set point field 740 to display a calibration set point data for the desired flow (e.g., a calibration set point determined from a calibration orifice. According to an embodiment, a user may manually enter the calibration set point into the calibration set point field 740 for comparison with the flow rate (in the flow rate field 730) of a workpiece. Alternatively, the calibration set point may be programmatically retrieved from a storage file or memory. In embodiments that utilize a variable frequency drive (VFD) controller for the pump 220, the GUI 700 may include one or more of a frequency control 760 and an auto/manual control 762. The GUI 700 may include a pressure vs time display 770 and/or a flow vs time display 775.

According to an embodiment, the GUI 700 may include a field 780 for entry of a file name to save a log of the measurements and/or results of the flow tuning operation. For example, the user may name a file corresponding to or identifying a particular workpiece 274 or workpiece type and storing predetermined flow rates and pressures obtained from calibration using the calibration orifice. The file may additionally or alternatively be used to store results of the flow tuning process for a specific workpiece.

Those having skill in the art will recognize that the low-pressure abrasive flow tuning system 200 may be scaled to accommodate multiple parallel operations. For example (not shown), the pump 220 may be one of plural pumps 220 each drawing flow medium 212 from the tank 210 and having respective pump outlets 224 each in fluid connection with respective tubes 230, respective volumetric flow meters 240 and endpieces 270. In such embodiments, respective pressure sensors 250, 260 may monitor each parallel operation.

FIG. 8 is a flow chart 800 illustrating a process of using a low-pressure abrasive flow tuning system (e.g., system 200 discussed above) to tune the flow rate though a workpiece constructed by additive manufacturing, according to an embodiment. An operation 802 includes constructing a flow calibration orifice having a predetermined flow rate equivalent to a desired workpiece flow rate. This may include constructing a flow calibration orifice having a substantially similar or identical cross-sectional area to an idealized workpiece opening. An operation 804 includes attaching the flow calibration orifice to a workpiece holder (e.g., 272) of a low-pressure abrasive flow tuning system (e.g., 200). An operation 806 includes conveying (e.g., pumping) a low-viscosity abrasive flow medium (e.g., 212) through the flow calibration orifice. An operation 808 includes determining a flow rate and/or a pressure drop of the low-viscosity abrasive flow medium through the flow calibration orifice. An operation 810 includes fitting in place of the calibration orifice a workpiece (e.g., 274) created by additive manufacturing and having an internal channel. An operation 812 includes monitoring a flow rate of the low-viscosity abrasive flow medium through the workpiece using a flow meter disposed upstream of the workpiece and monitoring a pressure drop through the workpiece via pressure sensors (e.g., 250, 260) disposed upstream and downstream from the workpiece. An operation 814 includes stopping the flow of the low-viscosity abrasive flow medium through the workpiece when the flow rate of the low-viscosity abrasive flow medium through the workpiece is substantially the same as the flow rate of the low-viscosity abrasive flow medium through the flow calibration orifice.

In some embodiments, before an additively manufactured workpiece is fitted to a low-viscosity abrasive flow tuning system (e.g., 100, 200), the workpiece may be subjected to pre-tuning processing. For example, additive manufacturing process in some instances leaves residual loose material, such as un-sintered powder within channels of the workpiece. Accordingly, the process of tuning a flow rate through a workpiece may include removing such residual material, e.g., by one or more of shaking, blowing, washing, twisting, and the like. In addition, some materials used in additive manufacturing may result in the finished product (workpiece) being porous to an extent, or the manufacturing process itself results in some porosity. Accordingly, a workpiece may be subjected to processing directed to densifying the workpiece prior to the flow tuning process. For example, a workpiece that is the subject flow tuning may be subjected to hot isostatic pressing (HIP) either before or after the flow tuning process.

In some embodiments, the workpiece may not be readily attachable to the low-pressure abrasive flow tuning system. In such cases, the process of tuning a flow rate through a workpiece may necessitate adding fixtures (e.g., plumbing) to the workpiece and/or the flow tuning system to facilitate fitting the workpiece to the flow tuning system. Although a calibration orifice may typically be originally formed for connection to the flow tuning system, it is recognized that there may be instances in which a fixture may be similarly added to a calibration orifice.

FIG. 9 is a flow chart 900 illustrating a process of using a low-pressure abrasive flow tuning system with an etching process, according to an embodiment. The operations 902, 904, 906, 908, 910, 912, and 914 may be substantially the same as the operations 802, 804, 806, 808, 810, 812, and 814 of flow chart 800 except as described below. The flow chart 900 differs from the flow chart 800 in that a chemical etching process is performed simultaneously on the workpiece with the flow of the low-pressure abrasive flow through the workpiece.

At operation 906, the low-viscosity abrasive flow medium may include an etching solution. The etching solution may include an acid (such as hydrochloric acid, nitric acid, or copper sulfate) or a base (such as potassium hydroxide, or another form of hydroxide). To dissolve the acid or base, the low-viscosity abrasive flow medium may be primarily water. The grit in the low-viscosity abrasive flow medium may be zirconium dioxide or another material which does not quickly react with the particular acid or base included in the etching solution.

Before operation 910, operation 909 may be performed. At operation 909, a resist material may be applied to one or more surfaces of the workpiece. The resist material may be silicone, or urethane or a similar material which is resistant or nonreactive to acid and/or base. The surfaces which have the resist material applied may include surfaces where it is not desired to have wear on the material of the workpiece by the etching solution, such as junctions for connection.

At operation 910, the calibration orifice is replaced with the workpiece. The flow of the etching solution through the workpiece may cause an increased wear by the grit in the low-viscosity abrasive flow medium by “softening” the material with the acid or base. Thus, the time which the workpiece has the low-viscosity abrasive flow medium flowing through the workpiece may be decreased. An electrical current may also be applied through the workpiece and acid solution to further decrease the time the workpiece has the low-viscosity abrasive flow medium flowing through the workpiece. For example, a 2 amp current from a 5 volt voltage source may be applied to the workpiece. The current may pass through the low-viscosity abrasive flow medium such that the acid or base of the etching solution dissolves material of the workpiece more quickly.

Operation 915 is performed after operation 914, where flow of the low-viscosity abrasive flow medium is stopped when flow rate of the low-viscosity abrasive flow medium is the same as the flow calibration orifice. At operation 915, the workpiece is removed from the low-viscosity abrasive flow medium and the resist material is removed from the workpiece.

Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read to mean “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof, and adjectives such as “conventional,” “traditional,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, a group of items linked with the conjunction “and” should not be read as requiring that each and every one of those items be present in the grouping, but rather should be read as “and/or” unless expressly stated otherwise. Similarly, a group of items linked with the conjunction “or” should not be read as requiring mutual exclusivity among that group, but rather should also be read as “and/or” unless expressly stated otherwise. Furthermore, although item, elements or components of the disclosure may be described or claimed in the singular, the plural is contemplated to be within the scope thereof unless limitation to the singular is explicitly stated. The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. Additionally, where a range is set forth, the upper and lower limitations of the range are inclusive of all of the intermediary units therein.

The previous description of the disclosed exemplary embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these exemplary embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Additionally, although the systems are described above in terms of various exemplary embodiments and implementations, it should be understood that the various features and functionality described in one or more embodiments are not limited to the embodiments with which they are described, but instead can be applied, alone or in some combination, to one or more of the other embodiments of the disclosure, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the present disclosure, especially in any following claims, should not be limited by any of the above-described exemplary embodiments.

Claims

1. A method of regularizing a passage in a workpiece using a low-pressure abrasive flow tuning system, the method comprising: providing the low-pressure abrasive flow tuning system to provide a low-viscosity abrasive flow medium to at least one internal channel of a workpiece to regularize the flow of the internal channel, the low-pressure abrasive flow tuning system having a known-flow path, the low-viscosity abrasive flow medium having a substantially linear ratio of shear stress to shear rate and including a carrier fluid throughout which an abrasive material is dispersed;defining at least one of a design pressure drop or flowrate of a low-viscosity abrasive flow medium when passed along the known-flow path and through a calibration orifice related to the desired flow in the internal channel of the workpiece;fitting a workpiece having the internal channel to the known-flow path;conveying the low-viscosity abrasive flow medium along the known-flow path and through the internal channel of the attached workpiece;monitoring a flow rate of the low-viscosity abrasive flow medium through the internal channel of the workpiece using a flow meter disposed upstream of the workpiece and/or monitoring a pressure drop through the workpiece via pressure sensors disposed upstream and downstream from the workpiece; andstopping the flow of the low-viscosity abrasive flow medium through the internal channel of the workpiece when the flow rate of the low-viscosity abrasive flow medium through the workpiece is substantially the same as the design flow rate of the low-viscosity abrasive flow medium as determined by at least one of design pressure drop or flowrate.

2. The method according to claim 1 wherein the defining at least one of a design pressure drop or flowrate is determined by providing a calibration orifice having a cross-sectional area substantially the same as that of an intended flow of the internal channel of the workpiece to the known-flow path and measuring at least one of flow or pressure drop to be established across the workpiece in the low-pressure abrasive flow tuning system to produce a calibrated value.

3. The method according to claim 1, further comprising, prior to fitting the workpiece to the low-pressure abrasive flow tuning system, removing residual manufacturing powder from the workpiece.

4. The method according to claim 1, wherein the viscosity of the low-viscosity abrasive flow medium is between 0 and 2000 cP.

5. The method according to claim 1, further comprising adding plumbing features to the workpiece for attachment to the known-flow path of the low-pressure abrasive flow tuning system.

6. The method according to claim 1, wherein said conveying the low-viscosity abrasive flow medium through the attached flow rate orifice, through the workpiece includes pumping the flow medium through the workpiece only at a pressure less than or equal to 500 psi.

7. The method according to claim 1 wherein said low-pressure abrasive flow tuning system includes a reservoir for containing the low-viscosity abrasive flow medium, the tank having an ultrasound transducer, the channel of the workpiece being located to have an output located within the low-viscosity abrasive medium, the ultrasound transducer dislodging abrasive material trapped within uneven surfaces or pits within the internal channel of the workpiece.

8. The method according to claim 1, further comprising: performing a chemical etching process on the internal channels in conjunction with the conveying the low-viscosity abrasive flow medium along the known-flow path and through the internal channel of the attached workpiece.

9. A low-pressure abrasive flow tuning system, comprising: a source of pressurized, low-viscosity flow media, the media having a substantially linear ratio of shear stress to shear rate and including a dispersed abrasive material provided in a carrier fluid;a known-flow path configured to convey the low-viscosity abrasive flow media under pressure from the source to a workpiece, the known-flow path ending in a workpiece holder configured to connect to a channel of a workpiece and to direct the low-viscosity abrasive flow medium into the channel of the workpiece;one or more sensors disposed along the known-flow path and configured to measure a rate of flow of the low-viscosity flow media and/or a pressure drop of the media within the known-flow path passing through the channel of the workpiece of the low-pressure abrasive flow tuning system;a controller electrically connected to the one or more of the source of pressurized, low-viscosity abrasive flow media and one or more sensors, the controller determining a rate of flow of the low-viscosity flow media and/or a pressure drop of the media through the channel of the workpiece, the controller comparing the rate of flow to a design flowrate of the low-viscosity abrasive flow media and/or comparing the pressure drop of the low-viscosity abrasive flow media though the channel of the workpiece to a design pressure drop of the low-viscosity abrasive flow media.

10. The low-pressure abrasive flow tuning system according to claim 9 where the design pressure drop is ascertained by providing a calibration orifice having a cross-sectional area substantially the same as that of an intended flow of the internal channel of the workpiece to the known-flow path and measuring at least one of flow or pressure drop to be established across a workpiece in a low pressure abrasive flow tuning system to produce a calibrated value.

11. The low-pressure abrasive flow tuning system according to claim 9, wherein the viscosity of the low-viscosity flow medium is between 0 and 2000 cP.

12. The low-pressure abrasive flow tuning system according to claim 9, further comprising an agitator associated with the source of pressurized, low-viscosity flow media, the agitator configured to agitate the low-viscosity abrasive flow medium to maintain or enhance distribution of the abrasive particulate in the flow medium.

13. The low-pressure abrasive flow tuning system according to claim 12, wherein the source of pressurized, low-viscosity flow media is a tank and the agitator includes, disposed in the tank a stirring device, a wiper device, and/or an aerator.

14. The low-pressure abrasive flow tuning system of claim 12 wherein the agitator is an ultrasonic transducer, wherein the workpiece is placed within the source with the exit of the channel in said workpiece being submerged within the low-viscosity abrasive medium, the ultrasonic transducer further dislodging loose particulates within uneven surfaces or pits within the internal channel of the workpiece.

15. The low-pressure abrasive flow tuning system according to claim 9, wherein the source of pressurized, low-viscosity flow media is configured to pressurize the flow medium to a pressure only less than or equal to 500 psi.

16. The low-pressure abrasive flow tuning system according to claim 1, wherein the one or more sensors include a volumetric flow meter and first and second pressure sensors,the source of pressurized, low-viscosity abrasive flow media is a pump, andthe controller is configured to receive the measured rate of volume of the low-viscosity flow medium per unit of time from a volumetric flow rate meter, the measured pressure from a first pressure sensor and the measured pressure from the second sensor and is further configured to control at least one of operation and speed of the pump.

17. The low-pressure abrasive flow tuning system according to claim 16, wherein the controller is further configured to automatically adjust the speed of the pump based on one or more of the received rate and pressure measurements.

18. The low-pressure abrasive flow tuning system according to claim 14, wherein the controller is further configured to control the one or more ultrasonic transducers to disturb particles stuck in uneven surfaces of the workpiece.

19. A non-transient computer readable medium having stored thereon instructions which, when executed by a computer processor electrically connected to a low-pressure abrasive flow tuning system, cause a display associated with the computer processor to present a graphical user interface (GUI) for monitoring and controlling the low-pressure abrasive flow tuning system, the GUI comprising: a first pressure field configured to display a first pressure received by the computer processor from a first pressure sensor disposed upstream from a workpiece in the low-pressure abrasive flow tuning system;a second pressure field configured to display a second pressure received by the computer processor from a second pressure sensor disposed downstream from the workpiece in the low-pressure abrasive flow tuning system;a flow rate field configured to display a flow rate of a low-viscosity Newtonian abrasive flow medium through the workpiece when the low-viscosity Newtonian abrasive flow medium is conveyed through the low-pressure abrasive flow tuning system, the flow rate received by the computer processor from a flow meter of the low-pressure abrasive flow tuning system; anda pressure control configured to control a pressure inducing mechanism in the low-pressure abrasive flow tuning system, the pressure inducing mechanism configured to convey the low-viscosity Newtonian abrasive flow medium through the low-pressure abrasive flow tuning system and an internal channel of a workpiece attached to the low-pressure abrasive flow tuning system.

20. The non-transient computer readable medium according to claim 19, wherein the graphical user interface is further configured to display a set point field, the set point field configured to receive from a user or prestored data an entry of a flow rate set point for comparison with the flow rate of the low-viscosity Newtonian abrasive flow medium through the workpiece.

21. The non-transient computer readable medium according to claim 20, wherein the flow rate set point is automatically determined and entered in the set point field as a result of a calibration test, the calibration test measuring a flow rate of a calibration orifice having a cross-sectional area substantially the same as the workpiece.