System and method for cavitation abrasive finishing of interior surfaces

Abstract

The invention relates to a system and method for cavitation abrasive finishing of an interior surface, a method of smoothing an interior surface of a tubular wall of a workpiece is disclosed, including immersing the workpiece in a mixture of a liquid and an abrasive, and inserting a cavitation shot nozzle into a cavity of the workpiece. The method further includes projecting a cavitation jet from the cavitation shot nozzle into the cavity.

Description

Background Technology

[0001] Additive manufacturing enables the efficient fabrication of new parts with complex shapes and features that were impractical or difficult to produce using previous methods. However, the resulting surface finishes are often much rougher than those produced by conventional manufacturing methods. Cavitation abrasive surface finishing (CASF) is a promising new method for mechanically smoothing such surface roughness. Cavitation bubbles are formed in a fluid by a transition to the gas phase due to increased flow velocity and internal energy, and then collapse and crush as the flow velocity and pressure around the bubbles dissipate. When the cavitation bubbles collapse, microjets are generated, which can provide energy to the particles of the abrasive material. However, using current CASF equipment, it is not feasible to generate a cloud of abrasive cavitation bubbles at a surface sufficiently close to the interior of a channel or other structure. Summary of the Invention

[0002] This disclosure provides systems, apparatus, and methods related to smoothing internal surfaces using cavitation abrasive surface finishing. In some examples, a method for smoothing the internal surface of a tubular wall of a workpiece may include immersing the workpiece in a mixture of liquid and abrasive and inserting a cavitation peening nozzle into a cavity of the workpiece. The method may also include injecting a cavitation jet from the cavitation peening nozzle into the cavity.

[0003] In some examples, the apparatus for smoothing a surface may include a first fluid source, a cavitation peening nozzle, a conduit connecting the first fluid source to the cavitation peening nozzle, and a pump configured to pump fluid from the first fluid source through the conduit to the cavitation peening nozzle. The cavitation peening nozzle may have an outer side and spacers extending outward from the outer side, and may be configured to generate a cloud of cavitation bubbles to smooth the inner surface of the tubular wall of a workpiece.

[0004] In some examples, the apparatus for smoothing surfaces may include a fluid source and a cavitation peening nozzle configured to generate a cloud of cavitation bubbles for smoothing the inner surface of a tubular wall of a workpiece. The apparatus may also include a conduit connecting the fluid source to the cavitation peening nozzle, a pump configured to pump high-pressure fluid from the fluid source through the conduit to the cavitation peening nozzle, and a slurry of liquid and abrasive within the tubular wall of the workpiece.

[0005] Features, functions, and advantages may be implemented independently in various examples of this disclosure, or may be combined in other examples, further details of which can be seen in the following description and figures. Attached Figure Description

[0006] Figure 1 This is a schematic diagram of an exemplary grinding cavitation system for an inner surface according to various aspects of this disclosure.

[0007] Figure 2 This is an isometric view of the nozzle assembly of another illustrative grinding cavitation system used for inner surfaces.

[0008] Figure 3 yes Figure 2 An isometric view of the nozzle assembly, with the inner surface of the finished pipe showing the nozzle through cut-off sidewalls.

[0009] Figure 4 yes Figure 2 An axial view of the nozzle assembly in the pipe, with guide vane attachment.

[0010] Figure 5 It is an isometric view of an additively manufactured part with two curved internal channels.

[0011] Figure 6 Used in systems with additional nozzle assemblies Figure 2 Isometric view of the nozzle assembly, thus enabling finishing. Figure 5 The inner surface of the two curved internal channels of the part, in which multiple sections of the part are cut off to reveal the nozzle.

[0012] Figure 7 This is a flowchart depicting the steps of an illustrative method for cavitation abrasive surface finishing of internal surfaces according to this teaching. Detailed Implementation

[0013] Various aspects and examples of systems and apparatuses for cavitation abrasive finishing of internal surfaces, as well as related methods, are described below and illustrated in the accompanying drawings. Unless otherwise stated, grinding cavitation systems and / or their various components according to this teaching may, but are not required to, include at least one of the structures, components, functions, and / or variations described, illustrated, and / or incorporated herein. Furthermore, unless expressly excluded, process steps, structures, components, functions, and / or variations described, illustrated, and / or incorporated herein in conjunction with this teaching may be included in other similar apparatus and methods, including those interchangeable between the disclosed examples. The following description of various examples is illustrative in nature and is not intended to limit this disclosure, its application, or use. Moreover, the advantages provided by the examples described below are illustrative in nature, and not all examples provide the same or the same degree of advantage.

[0014] This specific implementation includes the following sections, followed by: (1) an overview; (2) examples, components, and alternatives; (3) illustrative combinations and additional examples; (4) advantages, features, and benefits; and (5) a conclusion. The examples, components, and alternatives section is further divided into subsections A through C, each labeled accordingly.

[0015] Overview

[0016] Generally, a system for cavitation abrasive finishing of internal surfaces according to this teaching may include a nozzle assembly having a cavitation peening nozzle, a spacer, and a flexible fluid supply conduit, as well as a container filled with fluid. A part having an internal surface to be finished may be immersed in the fluid in the container, such that the internal space defined by the internal surface is filled with fluid. The fluid may include suspended abrasive microparticles and / or abrasive microparticles that may be otherwise introduced into the internal space. The nozzle assembly may be inserted into the internal space and used to generate a cloud of cavitation bubbles to excite the abrasive microparticles, thereby smoothing the internal surface and removing any manufacturing process material.

[0017] Examples, components, and alternatives

[0018] The following sections describe selected aspects of exemplary cavitation abrasive surface finishing apparatus and related systems and / or methods. The examples in these sections are intended to be illustrative and should not be construed as limiting the entire scope of this disclosure. Each section may include one or more different examples, and / or context or related information, functionality, and / or structure.

[0019] A. Smooth surface descriptive system

[0020] like Figure 1 As shown, this section describes an illustrative system 110 for smoothing inner surfaces. System 110 is an example of a system for cavitation abrasive finishing of inner surfaces, as described above.

[0021] Figure 1 This is a schematic diagram of system 110. A supply reservoir system 113, including a high-pressure pump 112, supplies pressurized water 114 along conduit 116. A control valve 120 allows precise control of the pressure and flow rate of the water supplied along conduit 116 to nozzle assembly 122. In some examples, system 110 may include multiple nozzle assemblies that may match or differ in size and / or shape. In such examples, the multiple nozzle assemblies may all be supplied by the high-pressure pump 112 along conduit 116, or they may have separate dedicated supplies of precisely controlled high-pressure water.

[0022] Nozzle assembly 122 is disposed in a pressurized tank 124 filled with a slurry 126 of abrasive microparticle material 150 mixed with water. A lid 128 of tank 124 can be opened to allow overflow from the tank into a collection container 130. The lid can be spring-coupled to tank 124, adjustable by a pressure relief valve, or weight-restrained to maintain pressure within the tank. The abrasive slurry 126 is also discharged from tank 124 along a conduit 132 regulated by control valve 134.

[0023] Nozzle assembly 122 includes a flexible conduit 140 and a cavitation peening nozzle 142. The flexible conduit 140 may include any structure suitable for carrying a high-pressure fluid that can be repeatedly buckled, bent, torsioned, and / or otherwise reconfigured. The conduit may include one or more flexible materials and / or buckling mechanisms, such as hinges or joints. Nozzle assembly 122 may include materials suitable for withstanding continuous exposure to cavitation and high-energy abrasive particles, particularly on the outer surface of the assembly. In some examples, the flexible conduit 140 may be connected to the cavitation nozzle 142 via a section of rigid conduit, and / or the assembly may be otherwise configured to achieve wear resistance or other desired structural properties.

[0024] The nozzle 142 of assembly 122 is inserted into the cavity 138 of workpiece 136 immersed in tank 124 to smooth the inner surface 144. More specifically, surface 144 is the inner surface of the tubular wall of workpiece 136. For example, the nozzle can be inserted into a tubular workpiece, such as a channel, hole, chamber, groove, hole, orifice, opening, and / or any channel-like feature. In the depicted example, workpiece 136 is a cylindrical pipe with a straight, circular central channel. The flexible conduit 140 of nozzle assembly 122 can also facilitate the cleaning of non-linear or curved channel-like features. System 110 can be configured specifically for smoothing the inner surface 144 of workpiece 136, can be configured for use with a range of similar workpieces, or can be configured for use with a wide variety of workpieces.

[0025] High-pressure water 114 is injected as a cavitation jet into the abrasive slurry 126 in the tank 124 through nozzle 142. The interaction between the cavitation jet and the abrasive slurry forms a cloud 146 of cavitation bubbles and abrasive particles. As the bubbles in the cloud 146 burst, the particles of the abrasive material 150 are excited and stimulated. The microjets generated by the bursting bubbles can jointly accelerate the movement of the particles. When the mixture of bubbles and particles contacts the surface 144 of the workpiece 136, the particles impact the surface and remove material. That is, the abrasive particles can be smoothed by the high force of the cavitation cloud on the inner surface 144.

[0026] Normal cavitation peening may also occur, as cavitation bubbles interact directly with the surface 144 of the workpiece 136. This allows for shot peening of the surface 144, thereby improving residual stress and fatigue strength, and cleaning the surface in preparation for painting or use.

[0027] The rupture impact force of cavitation bubbles is determined in part by the pressure of the injected water 114, the pressure of the slurry 126 in tank 124, the ratio between the two pressures, and the temperatures of the water 114 and the slurry 126 in tank 124. To optimize these parameters, pressure sensors, flow rate sensors, or temperature sensors may be included in tank 124 and / or in conduits 116 or 132. The high-pressure water 114 may be between 50 psi and 20,000 psi, or any effective pressure. The preferred pressure of the water 114 may depend on the pressure of the slurry 126 in tank 124, the diameter of the surface 144 of the workpiece 136, and / or the size of the cavitation nozzle 142. The preferred pressure may also be related to the design, geometry, and / or other characteristics of the cavitation nozzle.

[0028] To optimize these parameters, pressure and temperature sensors may be included in tank 124, or in either conduit 116 or 132. Control valves 120, 134, and cap 128, as well as the reservoir supply system 113 and temperature control system, may be connected to an electronic controller or other such components to allow for precise, coordinated control of pressure, flow, and temperature conditions throughout system 110.

[0029] In the illustrated example, the cavitation fluid is water. However, any desired fluid can be used. Properties such as the viscosity of the fluid used may affect the breaking force of the cavitation bubbles, and the fluid can be selected to improve impact or reduce the pressure required for the desired impact level. The fluid can also be selected based on the properties of the abrasive used and / or to achieve the desired properties of slurry 126. Any effective fluid flow device can be used to pump the pressurized fluid through nozzle assembly 122.

[0030] When high-pressure water 114 is sprayed into tank 124 by nozzle assembly 122, the water-to-abrasive particle ratio in slurry 126 may be affected. To maintain the desired ratio in slurry 126, abrasive material 150 can be added from source 152. Source 152 can be regulated by an electronic controller configured to coordinate the introduction of water, the introduction of abrasive material, the overflow of slurry 126, and the outflow of slurry through conduit 132.

[0031] The abrasive material 150 may comprise particles of any effective material, particles of any grit size, or a mixture of multiple materials. For example, the abrasive material may comprise metal, glass, ceramic, silica, alumina, pumice, nut shells, corn cobs, and / or plastic particles. As another example, the abrasive material may comprise natural or synthetic rubber, silicone, fluoropolymers, elastomers, fluororubber, Teflon, and / or fullerene-based carbon nanomaterial particles. All particles are preferably in the range of about 16 ANSI to 1200 ANSI grit. In this example, the abrasive material is garnet grit with a grit size of 150.

[0032] In this example, slurry 126 is preferably a ratio of approximately one-third abrasive material to two-thirds water. A suitable ratio can be selected based on the abrasive material and / or cavitation fluid used. The density or concentration of the abrasive material in the slurry can be selected to achieve the desired material removal rate (MRR).

[0033] Under the influence of gravity, the particles 150 of the abrasive material may detach from the suspension in the slurry 126 over time. To maintain the suspension of the slurry 126, a mixing device 154 is located in the tank 124. In this example, the mixing device 154 is a mechanical agitator, such as a rotating propeller, and is located at the bottom of the tank 124. Generally, any effective means of maintaining the suspension of the abrasive particles in the slurry 126 can be used, such as stirring, mixing, agitating, or otherwise. For example, an ultrasonic agitator can be used, which may be positioned at the top or side of the tank 124, and / or multiple agitators may be positioned at multiple locations throughout the tank.

[0034] B. Explanatory equipment for smooth surfaces

[0035] like Figure 2-6 As shown, this section describes an illustrative nozzle assembly 210 for smoothing the inner surface of a workpiece. Assembly 210 is an example of nozzle assembly 122 or cavitation nozzle assembly as described above. Assembly 210 can be used as part of a system, such as the grinding cavitation system 110 above and / or in the methods described below (e.g., inner surface finishing method 300).

[0036] Figure 2 This is an isometric view of nozzle assembly 210, including cavitation shot peening nozzle 212 and flexible conduit 214. The flexible conduit includes an outer metal-protected hose 218 and an inner polymer high-pressure supply hose 220. Nozzle 212 is coupled to the outer hose 218 and the inner hose 220 via a short section of rigid conduit 216, which can also be described as a metal protector.

[0037] The outer hose 218 may comprise a metallic material or metal alloy, braided material, pleated material, joined rigid sections, and / or any material that provides resistance to cavitation shot peening and impacts from high-energy abrasive particles. The outer hose may be durable enough to protect the inner hose 220 throughout prolonged exposure to shot peening and abrasive material impacts. In some examples, the nozzle assembly 210 may be configured to allow replacement of the outer hose 218 or the flexible conduit 214 once the outer hose 218 reaches a sufficient level of wear to impair the protection of the inner hose 220.

[0038] The inner hose 220 may comprise a flexible polymer or plastic and may be rated for high pressure. The inner hose may be sized to provide a desired flow rate at a pressure supplied by a selected pump or compressor, and / or to provide a desired pressure at the supplied flow rate. The inner hose 220 may also be adapted to the temperature and / or chemical properties of the liquid used for cavitation.

[0039] Nozzle 212 is depicted as a cylinder with a circular orifice. Typically, the nozzle can have any geometry or configuration that effectively generates a cavitation jet. That is, the nozzle is configured to dispense or eject a cavitation jet of fluid to generate a cloud of cavitation bubbles. For example, nozzles such as those disclosed in U.S. Patent No. 6,855,208 or specified in the American Society for Testing and Materials (ASTM) standard G134-95 can be used. The dimensions of nozzle 212 can be designed to allow insertion into one or more intended workpieces without obstructing channels or other channel-like features to be finished, as referenced below. Figure 4 To be further described. For example, the diameter of nozzle 212 can be between one-quarter and three-quarters of the diameter of the channel to be finished.

[0040] Figure 3 A nozzle assembly 210 in use is depicted. A nozzle 212 is inserted into the first end of a conduit 224 to smooth the inner surface 222. A flexible conduit 214 is connected to a high-pressure water source, and the conduit 224 is immersed in a slurry 226 of water and abrasive particles 228. The nozzle 212 ejects a cavitation jet 230 into the inner channel 232 of the conduit 224, thereby forming a cavitation bubble cloud 234. The abrasive particles 228 of the slurry 226 are drawn into the inner channel 232, where they are excited by the cavitation of the cloud 234. A portion of the excited abrasive particles impacts a region near the inner surface 222 of the cloud 234, thereby smoothing that region of the surface.

[0041] In this example, conduit 224 is immersed in slurry 226, and abrasive material particles 228 are supplied to cloud 234 by the suction effect generated by high-pressure water jetting via nozzle 212, which draws in the surrounding slurry and downwards into the internal channel 232 of the conduit. For the slurry to reach the cavitation bubble cloud generated by nozzle 212, sufficient clearance and any guiding structures are required around the nozzle. As discussed further below, the nozzle and(one or more) guiding structures can be sized and / or configured accordingly.

[0042] In some examples, the abrasive particles 228 may be provided by other means. For example, a nozzle assembly for smoothing a closed end orifice may include an abrasive supply hose in a flexible conduit 214 and an abrasive delivery opening in nozzle 212. In another example, a variable flow rate supply of slurry may allow for dynamic control of the material removal rate. In such an example, nozzle 212 may be larger than the diameter of the channel to be finished and / or the clearance requirements around the nozzle may differ from those in this example.

[0043] Nozzle assembly 210 advances slowly and smoothly along pipe 224 to achieve a uniform, consistent smoothness on inner surface 222. In the depicted example, inner channel 232 has a constant diameter, so the nozzle assembly can advance at a constant rate. In examples with variable geometry in the internal space, a variable advance rate of the nozzle assembly can be calculated to achieve consistent smoothness. In other words, the reduced smoothing effect intensity due to the greater surface distance from the cavitation cloud can be offset by an increased exposure time. For example, in a variable diameter pipe, nozzle assembly 210 can advance more slowly through sections with a larger diameter.

[0044] Figure 4 This is an end view of the nozzle assembly 210 in another conduit 236. The nozzle 212 is positioned in the conduit 236 by a guide attachment 240, which can also be described as a spacer. The guide attachment is configured to space the outer surface 239 of the nozzle 212 from the inner surface 238 of the conduit 236 while allowing water and abrasive particles to flow downwards along the conduit through the nozzle.

[0045] In this example, guide attachment 240 holds nozzle 212 in a centered or nearly centered position within pipe 236 and guides the nozzle through the pipe along a roughly centered path. This positioning helps achieve a uniform smoothness of the inner surface 238 and avoids excessive removal of material or areas of remaining roughness. The tolerance for deviation from a strictly centered path can depend on the desired uniformity of the resulting smoothness. That is, the flatter the desired smooth surface, the more precisely the nozzle may need to be positioned. In examples where only an overall average reduction in roughness is required, the nozzle may follow a roughly centered path and / or an average near-centered path. For example, the nozzle may be manually guided through the pipe without using guide attachment 240.

[0046] Nozzle 212 has an outer diameter 247, as measured in a cross-section perpendicular to the direction of fluid flow through the nozzle. In this example, nozzle 212 has a constant outer diameter. In some examples, the outer diameter 247 may vary along the nozzle. The constant outer diameter and / or the maximum value of the outer diameter 247 may be less than the inner diameter of pipe 236. In other words, the size of nozzle 212 may be designed to allow sufficient flow of water and abrasive particles through the nozzle to reach the generated cavitation cloud. Preferably, the outer diameter 247 may be less than approximately 75% of the inner diameter 248.

[0047] The guide attachment 240 may include a plurality of protrusions extending from the outer surface 239 of the nozzle 212. Each protrusion may have a major axis perpendicular to the direction of fluid flow through the nozzle 212 and / or perpendicular to the direction of the cavitation jet generated by the nozzle. The lengths of the protrusions may be equal to match the circular cross-section of the pipe, or may vary depending on the internal geometry of the pipe.

[0048] In this example, the guide attachment 240 includes four equal-sized triangular blades 242 equidistantly spaced around a ring 244 of the engagement nozzle 212. The blades can be described as arranged in two pairs of opposing blades. The distal end of each blade 242 contacts the inner surface 238. The guide attachment 240 can be described as having a span 246 between the distal ends of each pair of opposing blades. The span 246 matches the inner diameter 248 of the conduit 236.

[0049] The triangular shape of blade 242 reduces the cross-sectional area of ​​the conduit 236 obstructed by the guide attachment, thereby maximizing the flow of water and abrasive particles toward the cavitation cloud generated by nozzle 212. Any shape and / or number of blades 242 that allow sufficient flow and provide effective positioning of nozzle 212 may be included in guide attachment 240.

[0050] In some examples, the guide attachment 240 may be configured to conform to the variable geometry of the conduit 236 and / or the inner surface 238. For example, each of the blades 242 may be foldable, but springs are biased to extend outward from the ring 244, causing the span 246 to vary to match the variation in the inner diameter 248, so that the guide attachment 240 can hold the nozzle 212 in a centered position within the conduit 236. As another example, the blades 242 may include a flexible material configured to plastically deform in response to changes in the cross-sectional shape of the conduit 236.

[0051] Guide attachment 240 may be part of a set of guide attachments, allowing the nozzle assembly 210 to be configured for use with pipes and / or other channel-like features of various sizes. Guide attachments with a span matching the workpiece's inner diameter may be selected, and these attachments are mounted on the nozzle 212 prior to surface finishing. The ring 244 and nozzle 212 may include corresponding features that allow for snap-fit ​​engagement or other easy attachment and removal of the guide attachments.

[0052] In this example, the guide attachment 240 is made of polytetrafluoroethylene (PTFE) and is designed for periodic replacement. In some examples, the attachment may be single-use and / or disposable. Other materials that are susceptible to damage over time when exposed to cavitation peening and surface finishing with activated abrasive particles may be used for such limited-use attachments. In some examples, the guide attachment may comprise metal or other materials resistant to such exposure and may be suitable for scalable and / or long-term use.

[0053] Figure 5 An additive manufacturing (AM) part 260 is depicted, having a first channel 262 and a second channel 264. Channels 262 and 264 are manufactured from part 260, rather than being machined or drilled from the AM part. Therefore, the channels can have more complex curved shapes, but also possess the same surface roughness characteristics as additively manufactured parts. Cavitation grinding surface finishing can be performed on the outer surface 266 of the AM part 260 using a nozzle assembly 210 or a larger rigid nozzle assembly. However, as... Figure 6 As shown, nozzle assembly 210 may be needed to finish the interior of curved channels 262, 264.

[0054] In some examples, the nozzle assembly 210 can be used to sequentially finish two channels. Figure 6 In the diagram, nozzle assembly 210 is shown for use with second nozzle assembly 211. These two assemblies can be matched and each can have its own separate high-pressure water source, or both can be supplied by a single high-pressure pump.

[0055] AM part 260 is immersed in a slurry 270 of water and abrasive material particles. Each of the nozzle assemblies 210, 211 is inserted into the upper opening 272 of the corresponding channel 262, 264. When injected into the slurry 270, water is pumped through the nozzle assembly to form a cavitation jet, which in turn forms cavitation bubbles and a cloud 274 of abrasive particles. The inner surface is thus smoothed, finished, and shot-peened.

[0056] The cavitation jet also forces water and slurry 270 downwards along channels 262, 264 and out of the lower opening, not shown. Thus, slurry 270 is drawn into the upper opening 272, downwards along the channels, and through the nozzle assembly to supply abrasive particles to cloud 274.

[0057] Because channels 262 and 264 are matched in cross-sectional area and curvature, nozzle assemblies 210 and 211 advance synchronously along the channels. In examples with different channels, the nozzles can be controlled independently and advance along the channels. As each nozzle assembly advances along its respective channel, the flexible conduit 214 can buckle to conform to the curvature of the channel, thereby allowing nozzle 212 to remain centered in the channel. The flexible conduit 214 also allows nozzle 212 to reach multiple portions of the channel that are inaccessible to rigid tools.

[0058] C. An illustrative method for smooth inner surfaces

[0059] This section describes the steps of an illustrative method 300 for smoothing the inner surface of a tubular wall of a workpiece; see also Figure 7 The various aspects of the grinding cavitation system and / or nozzle assembly described above can be used in the method steps described below. Where appropriate, references may be made to components and systems that can be used to perform each step. These references are for illustrative purposes and are not intended to limit the possible ways in which any particular step of the method can be performed.

[0060] Figure 7 This is a flowchart describing the steps performed in an illustrative method, and may not describe the complete process or all steps of the method. Although the individual steps of method 300 are described below and in Figure 7 These steps are described, but not all of them need to be performed, and in some cases they can be performed simultaneously or in a different order than that shown.

[0061] In step 310, the method includes immersing the workpiece in a slurry of liquid and abrasive material. The slurry may be contained in a tank and maintained at a constant pressure and concentration of the abrasive material. In some examples, the tank may include a mixing device, such as a mechanical stirrer, to keep the abrasive material suspended in the liquid. In such examples, an optional step 311 may be performed to mix the slurry to keep the abrasive material suspended in the liquid. Additional abrasive material may also be added as needed to maintain the desired concentration.

[0062] Abrasive materials may include one or more microparticles selected from metals, glass, ceramics, silica, alumina, pumice, nut shells, corn cobs, plastics, natural or synthetic rubber, silicon, fluoropolymer elastomers, fluororubber, Teflon, and carbon nanomaterials. Preferably, the included microparticles can be in the size range of approximately 16 ANSI to 1200 ANSI. Abrasive media, media combinations, or mixtures of media or microparticles with any effect can be used.

[0063] For example, an additively manufactured part with through channels can be immersed in a mixture of garnet 150 gravel and water in a 1:2 ratio. When the part is immersed in the mixture, the mixture may fill the channels.

[0064] Step 312 involves inserting a cavitation peening nozzle into a cavity within the workpiece. The nozzle may be connected to a conduit supplying a high-pressure fluid, such as water. Preferably, the supplied fluid may be liquid-like with the slurry. Both the nozzle and a section of conduit adjacent to the nozzle may be configured to withstand exposure to cavitation and energizing abrasive particles. For example, the nozzle and / or conduit may have an outermost structure comprising metal or a metallic material.

[0065] The workpiece can be any part having an open-end cavity or a cavity having a first opening and a second opening. The cavity may include a tubular wall portion or a tubular section with a circumferential wall. Method 300 can be used on the inner surface of the smooth wall portion or the circumferential wall.

[0066] Step 314 involves injecting a cavitation jet from a nozzle into a cavity to generate a cloud of cavitation bubbles. The cavitation jet may include a high-pressure fluid supplied to the nozzle, which exits at a certain pressure and velocity through a nozzle geometry that generates the cloud of cavitation bubbles. The fluid may be exited under high pressure, preferably between 50 psi and 20,000 psi.

[0067] Cavitation jets can be injected into a slurry of liquid and abrasive particles filling a cavity, forming a mixture of cavitation bubbles and abrasive particles. The resulting bubble cloud can exhibit vortex motion, thus imparting velocity, momentum, and kinetic energy to the abrasive particles. The cavitation collapse of the bubbles can also collectively accelerate the movement of the abrasive particles to achieve high speeds and sufficient kinetic energy to remove material from the workpiece surface upon impact, thereby facilitating material removal from the inner surface of the workpiece to smooth that surface. The cavitation bubbles can then be used for further cavitation peening and cleaning of the inner surface of the workpiece.

[0068] Step 316 involves moving the nozzle through a tubular section of the cavity. The nozzle may advance along the tubular section while continuing to eject a cavitation jet from the nozzle. In this way, a cloud of cavitation bubbles and abrasive particles can move through the tubular section to smooth the inner surface of the tubular section. The nozzle may advance slowly to allow sufficient time for the cavitation bubbles and abrasive particles to act on the inner surface and achieve the desired smoothing and shot peening.

[0069] Substep 318 of step 316 involves varying the nozzle's movement rate through the tubular section based on its inner diameter. When the inner diameter of the tubular section remains constant, the nozzle can move at a constant rate, which can be increased for areas of the tubular section with smaller inner diameters and decreased for areas with larger inner diameters. This control over the movement rate promotes uniform smoothing of the inner surface of the tubular section due to the varying distance between the inner surface and the cavitation bubble cloud generated by the nozzle. In other words, when the cloud is farther from the surface to be smoothed, equivalent smoothing may require additional exposure time.

[0070] In some examples, the nozzle movement rate can be calculated based on the geometry of the tubular section. For instance, the nozzle movement can be computer-controlled based on a three-dimensional model of the tubular section. In some examples, the operator can evaluate smoothness and move the nozzle when the desired smoothness is achieved.

[0071] Step 320 includes using a spacer to maintain space between the nozzle and the inner wall of the tubular section. Sub-step 322 includes guiding the nozzle along a central path, which can also be performed using a spacer in some examples. Steps 320 and 322 can be performed throughout step 316 as the nozzle moves through the tubular section of the workpiece cavity.

[0072] The nozzle can be sized to allow space between the outer side of the nozzle and the inner wall of the tubular section. For example, the outer diameter of the nozzle may not exceed half the inner diameter at the narrowest point of the tubular section. Spacers can be removably or permanently attached to the nozzle and extend radially outward from the nozzle relative to the direction of fluid flow. The spacers may include multiple protrusions that prevent the nozzle from approaching the inner wall of the tubular section beyond a selected spacing distance by contacting the inner wall.

[0073] Maintaining space between the nozzle and the inner wall of the tubular section allows the slurry, in which the workpiece is immersed, to flow through the nozzle to the cavitation cloud. The pressure of the cavitation jet downwards along the tubular section causes a suction effect that draws the slurry downwards through the nozzle, thereby holding the liquid and abrasive at the nozzle to generate cavitation bubbles and a cloud of abrasive particles.

[0074] The spacing device can be configured to minimize obstruction of flow through the nozzle. For example, the spacing device may include openings, may include the minimum number of protrusions required for effective spacing, and / or may have any shape suitable for promoting slurry flow. The spacing device can also be configured to center the nozzle within a tubular section. For example, the protrusions of the spacing device may be arranged in pairs of equal length on opposite sides of the device.

[0075] Centering the nozzle within the tubular section and guiding it along a centered or substantially centered path through the tubular section allows for a uniform smoothing around the inner wall. In some examples, sub-step 322 can be performed by an experienced operator and / or by computer control based on a three-dimensional model of the tubular section, without any spacing devices. In some examples, the characteristics of the tubular section, such as its asymmetrical geometry, may require a non-centered path to achieve uniform smoothing; in such cases, sub-step 322 may include guiding the nozzle along such a path.

[0076] Optional step 324 includes removing the spacer from the nozzle and attaching spacers of different sizes. This optional step can be performed after the workpiece has been smoothed and before repeating method 300, between separate cavities or tubular sections of a single workpiece being smoothed, and / or between smoothing areas of different diameters within a tubular section.

[0077] The spacer may be one of a set of spacers, and / or may be described as a modular spacer. The spacer may be selectively attached to the nozzle, for example, by resilient or snap-fit ​​engagement. The nozzle may include grooves or other features to facilitate the connection of the spacer.

[0078] Illustrative combinations and additional examples

[0079] This section describes additional aspects and features of methods and apparatus for smoothing surfaces, presented as a series of paragraphs, but not limited to these paragraphs, some or all of which may be designated alphanumerically for clarity and efficiency. Each of these paragraphs may be combined in any suitable manner with one or more other paragraphs and / or disclosures from elsewhere in this application. Some of the following paragraphs explicitly reference and further limit the other paragraphs, providing examples of suitable combinations, but not limitations thereto.

[0080] A0. A method for smoothing the inner surface of a tubular wall of a workpiece, the method comprising:

[0081] The workpiece is immersed in a mixture of liquid and abrasive.

[0082] Insert the cavitation shot peening nozzle into the cavity of the workpiece, and

[0083] The cavitation jet is injected into the cavity from the cavitation shot peening nozzle.

[0084] A1. The method according to A0 further includes:

[0085] The moving cavitation shot peening nozzle passes through a tubular section of the cavity, wherein the tubular section has a circumferential wall.

[0086] A2. The method according to A0 or A1 further includes:

[0087] During the moving step, a radial space is maintained between the outer surface of the cavitation shot peening nozzle and the circumferential wall of the tubular section.

[0088] A3. The method according to A1 or A2, wherein the moving step includes changing the rate at which the cavitation shot peening nozzle moves through the tubular section relative to the change in the inner diameter of the circumferential wall.

[0089] A4. The method according to any one of A1-A3, wherein the cavitation shot peening nozzle has a cylindrical outer surface, the outer diameter of which is less than 90% of the inner diameter of the circumferential wall of the tubular section.

[0090] A5. The method described in A4, wherein the outer diameter is less than 75% of the inner diameter.

[0091] A6. The method according to A0-A5, wherein the mixture is contained in a tank, and further comprises mixing the mixture to maintain the abrasive material in suspension in the liquid.

[0092] A7. The method according to any one of A0-A6 further comprises:

[0093] Pressurized fluid is delivered to the cavitation shot peening nozzle.

[0094] A8. The method according to any one of A0-A7 further comprises:

[0095] By using a spacer between the outer surface of the cavitation shot peening nozzle and the inner surface of the tubular section of the cavity, the cavitation shot peening nozzle is guided through the tubular section of the cavity along a basically centered path.

[0096] A9. The method according to A8, wherein the spacer includes a plurality of protrusions extending outward from the outer surface of the cavitation shot peening nozzle.

[0097] A10. The method according to A9, wherein the plurality of protrusions comprises blades uniformly distributed around the outer surface of the cavitation shot peening nozzle.

[0098] A11. According to the method of A10, the plurality of protrusions includes at least four blades.

[0099] A12. The method according to any one of A9-A11, wherein the plurality of protrusions includes at least one retractable protrusion that is spring-biased to extend outward from the outer surface of the cavitation shot peening nozzle.

[0100] A13. The method according to any one of A9-A12, wherein the plurality of protrusions includes at least one protrusion comprising a flexible material.

[0101] A14. The method according to any one of A8-A13, wherein the spacer is configured to change shape according to the changing geometry of the inner surface of the tubular section of the cavity.

[0102] A15. The method according to any one of A8-14, wherein the spacer has a variable diameter.

[0103] A16. The method according to any one of A8-A15 further includes disassembling the spacer and attaching another spacer of a different size suited to the tubular construction.

[0104] A17. The method according to any one of A0-A16, wherein the abrasive comprises garnet gravel.

[0105] B0. An apparatus for smoothing a surface, the apparatus comprising:

[0106] First fluid source,

[0107] A cavitation shot peening nozzle having an outer side and a spacer extending outward from the outer side, and

[0108] A first fluid source is connected to a conduit of a cavitation peening nozzle, and a pump is configured to pump the first fluid from the first fluid source through the conduit to the cavitation peening nozzle, which is configured to generate a cloud of cavitation bubbles for smoothing the inner surface of the tubular wall of a workpiece.

[0109] B1. The device according to B0, further comprising:

[0110] A tank containing a second fluid is configured to contain an immersed workpiece, while a cavitation shot peening nozzle is used to smooth the inner surface of the tubular wall of the workpiece.

[0111] B2. The device according to B1, wherein the tank includes a mixing device for maintaining a uniform concentration of abrasive particles in a second fluid.

[0112] B3. The device according to B2, wherein the concentration is maintained between approximately one-quarter and three-quarters.

[0113] B4. The device according to B2, wherein the concentration is maintained between approximately 10% and 60%.

[0114] B5. The equipment according to any one of B1-B4, wherein the tank comprises a plurality of mixing devices.

[0115] B6. The device according to any one of B1-B5, wherein the second fluid comprises an abrasive.

[0116] B7. The device according to B6, wherein the abrasive comprises garnet gravel.

[0117] B8. The device according to B6 or B7, wherein the abrasive comprises one or more of (a) natural or synthetic rubber, (b) silicon, (c) a fluoropolymer elastomer, (d) fluororubber (Viton), (e) Teflon, and (f) a fullerene-based carbon nanomaterial.

[0118] B9. The apparatus according to any one of B6-B8, wherein the abrasive comprises nanomaterials.

[0119] B10. The apparatus according to any one of B0-B9, wherein the spacer is configured to hold the cavitation shot peening nozzle in a substantially central position within the tubular wall.

[0120] B11. The apparatus according to any one of B0-B10, wherein the spacing device includes a plurality of protrusions extending from the outside, the protrusions being configured to maintain substantially equal relative radial distances between the outside of the cavitation shot peening nozzle and the inner surface of the tubular wall of the workpiece.

[0121] B12. The device according to B11, wherein each of the plurality of protrusions has a long axis extending perpendicular to the direction in which fluid flows through the cavitation shot peening nozzle.

[0122] B13. The device according to B11 or B12, wherein the plurality of protrusions comprises at least four protrusions.

[0123] B14. The apparatus according to any one of B0-B13, wherein the cavitation shot peening nozzle has a cross-sectional diameter parallel to the inner diameter of the tubular wall, and the cross-sectional diameter of the cavitation shot peening nozzle is less than 90% of the inner diameter of the tubular wall.

[0124] B15. The device according to B14, wherein the cross-sectional diameter is less than 75% of the inner diameter.

[0125] B16. The apparatus according to any one of B0-B15, wherein the cavitation shot peening nozzle has a proximal end and a distal end, the proximal end having a fixing device for connecting the cavitation shot peening nozzle to a flexible tube portion of a conduit, and the distal end having an opening for distributing a cavitation jet of a first fluid.

[0126] B17. The device according to B16, wherein the flexible tube portion has a metal protector on a section of the flexible tube portion adjacent to the fixing device of the cavitation shot peening nozzle.

[0127] B18. The device according to B16 or B17, wherein the flexible tube portion comprises a metal-reinforced outer flexible hose and a polymer inner flexible hose.

[0128] B19. The device according to any one of B0-B18, wherein the spacer is removable, thereby allowing interchangeable spacers of different sizes to be used on the same cavitation shot peening nozzle to smooth different tubular configurations.

[0129] B20. The apparatus according to any one of B0-B19 further includes an abrasive material conveying mechanism.

[0130] B21. The device according to B20, wherein the abrasive material delivery mechanism is integrated with the cavitation nozzle.

[0131] B22. The apparatus according to B21, wherein the abrasive material conveying mechanism is configured to convey a slurry of abrasive material and water.

[0132] C0. An apparatus for smoothing a surface, comprising:

[0133] Fluid source

[0134] Cavitation shot peening nozzle,

[0135] Connect the fluid source to the duct of the cavitation shot peening nozzle.

[0136] A pump configured to pump high-pressure fluid from a fluid source through a conduit to a cavitation peening nozzle, the cavitation peening nozzle being configured to generate a cloud of cavitation bubbles for smoothing the inner surface of a tubular wall of a workpiece.

[0137] The liquid and abrasive slurry inside the tubular wall of the workpiece.

[0138] C1. The apparatus according to C0, wherein the cavitation shot peening nozzle has a circumferential outer surface and a spacer extending outward from the outer surface.

[0139] C2. The device according to C1, wherein the spacer includes a plurality of blades uniformly distributed around the outer surface of the cavitation shot peening nozzle.

[0140] C3. The device according to C1 or C2, wherein the spacer is detachable, thereby allowing interchangeable spacers with blades of different sizes to be used on the same cavitation shot peening nozzle to smooth different tubular configurations.

[0141] Advantages, features and benefits

[0142] The various examples of cavitation abrasive surface finishing systems and methods described herein offer several advantages over known solutions for finishing rough surfaces. For example, illustrative embodiments of the methods described herein allow for finishing of internal surfaces and features such as channels, holes, tubes, and / or hollow structures.

[0143] In addition, among other benefits, the illustrative examples described herein allow for the smoothing, cleaning, and shot peening of surfaces through a single process.

[0144] In addition, among other benefits, the illustrative examples described herein allow for surface finishing using safe and inexpensive materials such as water and ceramic abrasives.

[0145] In addition, among other benefits, the illustrative examples described herein allow for a smooth, uniform flow along the length of a narrow internal space, such as a channel.

[0146] No known system or apparatus can perform these functions, especially for such inaccessible surfaces. Therefore, the illustrative examples described herein are particularly useful for additively manufactured parts with internal surfaces. However, not all examples described herein offer the same advantages or to the same degree.

[0147] in conclusion

[0148] The above disclosure may include several different examples with independent practical applicability. While each of these has been disclosed in its preferred form, the specific examples disclosed and described herein should not be considered limiting, as many variations are possible. As for the section headings used in this disclosure, such headings are for organizational purposes only. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various elements, features, functions, and / or characteristics disclosed herein. The appended claims specifically point to certain combinations and sub-combinations considered novel and non-obvious. Other combinations and sub-combinations of features, functions, elements, and / or characteristics may be claimed in applications claiming priority to this application or related applications. Such claims, whether broader, narrower, equivalent, or different in scope from the original claims, are also considered to be included within the subject matter of this disclosure.

Claims

1. A method (300) for smoothing the inner surface of a tubular wall of a workpiece, the method comprising: The workpiece is immersed in a mixture of liquid and abrasive. Insert the cavitation shot peening nozzle into the cavity of the workpiece. A cavitation jet from the cavitation shot peening nozzle is injected into the cavity to generate a cavitation bubble cloud; The cavitation shot peening nozzle is moved through a tubular section of the cavity, wherein the tubular section has a circumferential wall; as well as Maintain the radial space between the outer surface of the cavitation shot peening nozzle and the circumferential wall of the tubular section during the moving step; The pressure of the cavitation jet flowing downward along the tubular section causes a suction effect, which draws the mixture of liquid and abrasive into the tubular section and downward along the tubular section through the cavitation peening nozzle to the cavitation bubble cloud.

2. The method (300) according to claim 1, wherein the moving step includes changing the rate at which the cavitation shot peening nozzle moves through the tubular section relative to a change in the inner diameter of the circumferential wall.

3. The method (300) of claim 1, wherein the mixture is contained in a tank, and further comprises mixing the mixture to keep the abrasive suspended in the liquid.

4. The method (300) according to any one of claims 1-3, further comprising: The cavitation shot peening nozzle is guided through the tubular section of the cavity along a substantially centered path by using a spacer between the outer surface of the cavitation shot peening nozzle and the inner surface of the tubular section of the cavity.

5. The method (300) according to claim 4 further includes disassembling the spacer and attaching another spacer of a size suitable for a different tubular construction.

6. An apparatus (110) for smoothing a surface, the apparatus comprising: First fluid source, A cavitation shot peening nozzle (142, 212) having an outer side (239) and a spacer (240) extending outward from the outer side. A tank (124) containing a second fluid (126, 226, 270) comprising abrasive, wherein the tank is configured to contain immersed workpieces (136, 224, 236, 260), and the cavitation peening nozzles (142, 212) are used to smooth the inner surfaces (144, 238) of the tubular walls (232, 262, 264) of the workpieces (136, 224, 236, 260); and A conduit connecting the first fluid source to the cavitation peening nozzle, and a pump (112) configured to pump a first fluid (114) from the first fluid source through the conduit to the cavitation peening nozzle, the cavitation peening nozzle being configured to generate a cavitation jet, and the cavitation jet being configured to generate a cloud of cavitation bubbles (146, 234, 274) for smoothing the inner surfaces (144, 238) of the tubular walls (232, 262, 264) of the workpieces (136, 224, 236, 260). The spacer (240) is configured to maintain a space between the cavitation peening nozzle (142, 212) and the inner surface (144, 238) of the tubular wall (232, 262, 264), such that in use, the pressure of the cavitation jet downward along the tubular wall (232, 262, 264) causes a suction effect that draws the second fluid (126, 226, 270) into the tubular wall and downward along the tubular wall through the cavitation peening nozzle to the cavitation bubble cloud (146, 234, 274).

7. The device (110) according to claim 6, wherein the tank (124) includes a mixing device (154) for maintaining a homogeneous concentration of abrasive in the second fluid (126, 226, 270).

8. The device (110) according to claim 7, wherein the concentration being maintained is between 10% and 60%.

9. The device (110) according to claim 6, wherein the abrasive comprises garnet gravel.

10. The device (110) according to any one of claims 6-9, wherein the spacer (240) includes a plurality of protrusions (242) extending from the outer side (239), the protrusions (242) being configured to maintain an equal radial distance between the outer side of the cavitation shot peening nozzle (142, 212) and the inner surface (144, 238) of the tubular wall (232, 262, 264) of the workpiece (136, 224, 236, 260).

11. The device (110) according to claim 6, wherein the cavitation shot peening nozzle (142, 212) has a cross-sectional diameter (247) parallel to the inner diameter (248) of the tubular wall (232, 262, 264), and the cross-sectional diameter of the cavitation shot peening nozzle is less than 75% of the inner diameter of the tubular wall.

12. The device (110) according to claim 6, wherein the conduit comprises a flexible portion (140, 214) having a metal-reinforced outer flexible hose (218) and a polymer inner flexible hose (220).

Images