TECHNICAL FIELD

The present disclosure broadly relates to methods and systems for vibratory surface fmishing/abrading of a substrate.

BACKGROUND

Methods of modifying a surface of a workpiece include, for example, methods of finishing the surface of the workpiece and methods of hardening the surface of the workpiece.

In the case of molded parts (e.g., especially cast metal parts), it is common practice to subject the workpiece to abrasive post-processing to remove burs, mold lines, and otherwise smooth the surface of the workpiece. Examples of such processes include vibrating and/or blasting with abrasive media propelled by high velocity gas (e.g., nut shells, ceramic particles, steel balls, or sand). In these processes, unwanted raised surface features are reduced overtime.

Shot peening is similar to sandblasting, except that it operates by the mechanism of plasticity rather than abrasion: each particle functions as a ball-peen hammer. In practice, this means that less material is removed by the process, and less dust created.

Shot peening (i.e., peening with shot particles, hereinafter "shot") is a cold working process used to produce a compressive residual stress layer and modify mechanical properties of metals and composites. It entails impacting a metallic surface with shot (i.e., round particles typically made of, for example, metal, glass, or ceramic) with sufficient force sufficient to create plastic deformation. In machining, shot peening is used to strengthen and relieve stress in components like steel automobile crankshafts and connecting rods. In architecture it provides a muted finish to metal. Typically, in shot peening a stream of shot is directed toward a workpiece.

Various vibratory devices have been used modify the surface of a workpiece using certain media particles such as, for example, shot particles (e.g., used in shot peening) and abrasive particles (e.g., used in surface finishing).

Some vibratory devices operate in an oscillatory path that is arcuate or random, while others use reciprocating linear paths. Certain vibratory devices of the latter type, marketed by Resodyn Acoustic Mixers, Inc., Butte, Montana (e.g., under the trade designation "LabRAM"). These devices use reciprocating linear motion to agitate a container and its contents at or close to conditions of acoustic resonance, wherein energy is efficiently coupled from an actuator to the container and its contents.

SUMMARY

During agitation, the working bodies are accelerated along the path of linear (e.g., vertical) motion and collide with each other and the workpiece. While this method is effective, the present inventors have discovered that, quite unexpectedly, the rate of surface finishing of certain faces of the workpiece is substantially enhanced by including one or more elements in the processing chamber of a finishing vessel that impart motion in a direction other than the linear motion to the working bodies.

In one aspect, the present disclosure provides a method of finishing a surface of a workpiece, the method comprising: providing the workpiece disposed in a processing chamber of a vibratory finishing system comprising: a finishing vessel comprising the processing chamber bounded by a bottom surface, at least one sidewall surface, and atop surface, wherein the finishing vessel has at least one deflecting element disposed within the processing chamber, and wherein the at least one deflecting element is capable of deflecting a working body moving in a first linear direction, in a single collision, to a second direction that is oriented at least 30 degrees different than the first linear direction; and an actuator for linearly displacing the finishing vessel in a linearly reciprocating manner; disposing a plurality of the working bodies into the finishing vessel; and displacing the finishing vessel in the linearly reciprocating manner along the first linear direction such that the working bodies repeatedly contact the surface of the workpiece.

In another aspect, the present disclosure provides a finishing vessel comprising: a processing chamber bounded by a bottom surface, at least one sidewall surface, and a top surface, wherein the finishing vessel has at least one deflecting element disposed within the processing chamber, wherein the at least one deflecting element is capable of deflecting a spherical working body moving in a first linear direction, in a single collision, to a second direction that is oriented at least 30 degrees different than the first linear direction, and wherein the finishing vessel further comprises a mounting member for securely and reversibly fixturing a workpiece within the processing chamber.

Features and advantages of the present disclosure will be further understood upon consideration of the detailed description as well as the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic exemplary process diagram of an exemplary method 100 of finishing a surface of a workpiece according to the present disclosure.

FIG. 2A is a schematic perspective view of an exemplary finishing vessel 200 according to the present disclosure.

FIG. 2B is a schematic perspective view of insert 265.

FIG. 2C is a schematic cross-sectional view of insert 265 in FIG. 2B taken along line 2C-2C.

FIG. 2D is a schematic cross-sectional view of finishing vessel 200 in FIG. 2A taken along line

2D-2D

FIG. 3A is a schematic perspective view of an exemplary finishing vessel 300 according to the present disclosure. FIG. 3B is a schematic cross-sectional view of finishing vessel 300 in FIG. 3A taken along line 3B- 3B.

Repeated use of reference characters in the specification and drawings is intended to represent the same or analogous features or elements of the disclosure. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the disclosure. The figures may not be drawn to scale.

DETAILED DESCRIPTION

As shown in FIG. 1, methods of finishing the surface of a workpiece according to the present disclosure involve moving a finishing vessel 100 having a mounting member 130 securing a workpiece 190, and working bodies 180 in a reciprocating fashion along linear direction 170 , thereby causing the working bodies to impact the surface of the workpiece. Deflecting element 120 redirects the working bodies in directions at least 30 degrees different than the linear direction 170, thereby increasing their effectiveness at surface finishing the top and sides of the workpiece.

Since it is necessary to place the workpiece within the finishing vessel, and remove it after processing, in preferred embodiments, the finishing vessel preferably comprises at least two portions that can be separated to provide access to the workpiece. In some preferred embodiments, shown in FIG. 2A, the finishing vessel 200 comprises a lower portion 230 and an upper (lid) portion 220 that is adapted to securely and releasably engage the lower portion (e.g., by a snap or press fit or screw threads).

While in some embodiments, the finishing vessel may be a two-part vessel having a lower portion (e.g., a cup) and an upper portion (e.g., a cover) that releasably engages the lower portion to define that processing chamber, it is also possible that the finishing vessel may further include a sleeve that conformably engages the lower portion and comprises one or more of the deflecting elements. As used herein, the phrase "conformably engages" means that the out surface of the sleeve has a topography that is a least substantially complementary to the inner surface of the upper and/or lower portion absent the sleeve. The sleeve may be fixed (e.g., by tape, mechanical fastener(s), friction fit, or glue) to the upper or lower portion of the finishing vessel or it may be held in place by its size and shape alone. In either case, the deflecting element(s) forms at least a portion of the surface of the processing chamber, and hence also of the overall finishing vessel.

Without wishing to be bound by theory, the present inventors believe that while the working bodies ricochet off the sides, bottom and top of the sealed mixing vessel during vibration to an extent that the workpiece is bombarded from all angles, inasmuch as the motion of the finishing vessel is linear in nature, the working bodies also move predominantly in the same linear direction (excluding, for example, other directions caused by collisions of working bodies with themselves and the workpiece). Addition of the deflecting element(s) increases the momentum of the working bodies in directions other than the linear direction and thereby increase the rate of surface finishing on portions of the workpiece that would not normally be impacted by a particle travelling in the abovementioned linear direction. Referring now to FIGS. 2A-2C, exemplary finishing vessel 200 comprises a lower portion 230 and an upper portion 220 that releasably engages the lower portion Sleeve 265 is conformably disposed within lower portion 230. Processing chamber 210 is bounded by bottom surface 212, sidewall surface 214, and a top surface corresponding to the inner surface of the upper portion 216. The finishing vessel has at least one deflecting element 266 (see FIGS. 2B and 2C) disposed within the processing chamber. Each deflecting element is capable of deflecting a working body (shown as 180 in FIG. 1) moving in a first linear direction (shown as 170 in FIG. 1), in a single collision, to a second direction 172 that is oriented at least 30 degrees different than the first linear direction.

Preferably, the side of finishing vessel has a top, a bottom, and at least one sidewall extending therebetween that is substantially aligned with (i.e., with 8 degrees, preferably within 5 degrees, and more preferably parallel to) the linear direction associated with reciprocating motion during use. In some preferred embodiments, the finishing vessel is at least substantially cylindrical in shape.

While in some preferred embodiments, the finishing vessel further comprises a mounting member as described above, this is not a requirement.

Referring now to FIG. 2D, mounting member 235 is secured to the finishing vessel and disposed within the processing chamber 210 for securely and reversibly fixturing a workpiece (not shown) within the processing chamber.

If a mounting member is present, the workpiece is preferably reversibly fixtured to the mounting member. Exemplary mounting members may include clamps (e.g., screw clamps and/or spring clamps), threaded fasteners, quick-connect fasteners (e.g., bayonet mounts and/or snap-on fasteners). The mounting member(s) may be a secured to any part of the processing chamber inner surface. Examples include a lid/top, sidewall of bottom surface.

Various configurations and positions of the deflecting element(s) may be used. For example, any shape capable of deflecting the working bodies consistent with the description hereinabove may be used. Likewise, combinations of deflecting elements with different sizes and/or shapes may be used. In general, the deflecting element will have at least one surface angled such that it can deflect a spherical working body traveling along the linear direction of reciprocating motion by at least 30 degrees. Another exemplary embodiment is shown in FIGS. 3 A and 3B, below.

Referring now to FIGS. 3A and 3B, insert 365 deflecting elements 320 are disposed adjacent to the bottom surface 350 of processing chamber 310 to finishing vessel 300. Insert 368 is essentially the same as insert 265 (see FIG. 2A) except that it further comprises a pyramidal base 367 deflecting element disposed on the bottom surface of the processing chamber in use. The finishing vessel is agitated in a linearly reciprocating manner (i.e., back and forth) using a linear motion. This may be typically provided by an actuator for linearly displacing the finishing vessel in a linearly reciprocating manner. Any device capable of accomplishing this may be used including e.g., a motor-driven piston or rotating cam.

Commercially available mixing devices capable of accomplishing the above are marketed by Resodyn Acoustic Mixers, Butte, Montana. Laboratory-scale devices include LabRAM I and LabRAM II controlled batch mixers. Large scale devices are marketed under the trade designations OmniRAM,

RAM5, and RAM 55. These devices typically operate at resonant vibrational frequencies of from 20 to up to < 1 kHz, preferably 40 to 100 hertz, more preferably 40 to 80 hertz, and more preferably 55-65 hertz, although this is not a requirement. The vibrating mixers are also characterized by actuator displacements that are on the order of 0.5 inch (1.3 cm), that may be accompanied by an acceleration g-force, wherein g =

9.8 m/s , of at least 20-g, 30-g, 40-g, 50-g, or even at least 60-g, although this is not a requirement. Further details concerning suitable resonant acoustic mixers can be found, for example, in U.S. Pat. Nos. 7,188,993 (Howe et al.) and 9,808,778 (Farrar et al.). Preferably, a control module controls the actuator such that the sealed mixing vessel vibrates under resonant or near-resonant conditions (e.g., resonant acoustic conditions) throughout the surface modification process. Use of vibrationally resonant conditions ensures high efficiency use of the supplied energy.

In practice, the working bodies and the workpiece(s) are disposed within the interior chamber. The workpiece may be loose within the interior chamber or fixed in a given position relative to the sealed mixing vessel (e.g., mounted to a wall or cover of the sealed mixing vessel. The latter configuration may be desirable if the workpiece has a large mass and/or is delicate, so that collisions between the workpiece and the vessel walls are prevented.

On a volume basis, the working bodies may collectively constitute up to 20, 30, 40, 50, 60, 70, or 80 percent of the volume of the interior chamber, for example. However, in typical use the working bodies may collectively constitute from 5 to 35 percent of the volume of the interior chamber, although lesser and greater amounts may also be used.

Useful working bodies may include abrasive bodies and peening bodies. In some embodiments, at least some of the working bodies comprise spheroidal and/or spherical working bodies.

The abrasive bodies are typically irregular so that sharp-edged working bodies can cut away brittle surface deposits; however, this is not a requirement. Abrasive bodies useful for the methods of the present disclosure may include any abrasive bodies that are useful for abrasive blasting (commonly termed "sandblasting") or vibratory tumbling. There are several variants of the process, using various media; some are highly abrasive, whereas others are milder. Exemplary materials for the abrasive bodies may include sand, copper slag, nickel slag, coal slag, glass beads, plastic abrasive, cmshed glass, silica, steel spheres, steel grit, stainless steel spheres, cut steel wire, ground-up plastic stock, walnut shells, corncobs, aluminum oxide (which includes brown aluminum oxide, heat treated aluminum oxide, and white aluminum oxide), co-fused alumina-zirconia, ceramic aluminum oxide, green silicon carbide, black silicon carbide, chromia, zirconia, flint, cubic boron nitride, boron carbide, diamond, garnet, sintered alpha-alumina-based ceramic as described, for example, by U.S. Pat. No. 4,314,827 (Leitheiser et al.) and in U.S. Pat. Nos. 4,770,671 and 4,881,951 (both to Monroe et al.). Preferentially, the abrasive bodies are aggregates of the aforementioned abrasive particles, bound by polymers, ceramics or metals, for example. Usually, the abrasive bodies range in diameter from 0.01 millimeter (mm) to as large as 5 mm, preferably from 0.1 mm to 5 mm; however, this is not a requirement. In some embodiments, the abrasive bodies may be sized according to an abrasives industry specified nominal grade.

Abrasive bodies (i.e., abrasive particles) graded according to abrasive industry accepted grading standards specify the particle size distribution for each nominal grade within numerical limits. Such industry accepted grading standards (i.e., abrasives industry specified nominal grade) include those known as the American National Standards Institute, Inc. (ANSI) standards, Federation of European Producers of Abrasive Products (FEPA) standards, and Japanese Industrial Standard (JIS) standards.

ANSI grade designations (i.e., specified nominal grades) may include, for example: ANSI 4, ANSI 6, ANSI 8, ANSI 16, ANSI 24, ANSI 36, ANSI 40, ANSI 50, ANSI 60, ANSI 80, ANSI 100, ANSI 120, ANSI 150, ANSI 180, ANSI 220, ANSI 240, ANSI 280, ANSI 320, ANSI 360, ANSI 400, and ANSI 600. FEPA grade designations include P8, P12, P16, P24, P36, P40, P50, P60, P80, P100, P120, P150, P180, P220, P320, P400, P500, P600, P800, P1000, and P1200. JIS grade designations include JIS8, JIS12,

JIS 16, JIS24, JIS36, JIS 46, JIS 54, JIS 60, JIS 80, JIS 100, JIS 150, JIS 180, JIS 220, JIS 240, JIS 280, JIS 320, JIS 360, JIS 400, JIS 600, JIS 800, JIS 1000, JIS 1500, JIS 2500, JIS 4000, JIS 6000, JIS8000, JIS 10000, JIS 20000, and JIS 30000.

Alternatively, abrasive bodies (abrasive particles) can be graded to a nominal screened grade using U.S.A. Standard Test Sieves conforming to ASTM E-ll "Standard Specification for Wire Cloth and Sieves for Testing Purposes." ASTM E-ll proscribes the requirements for the design and construction of testing sieves using a medium of woven wire cloth mounted in a frame for the classification of materials according to a designated particle size. A typical designation may be represented as -18+20 meaning that the abrasive particles through a test sieve meeting ASTM E-l l specifications for the number 18 sieve and are retained on a test sieve meeting ASTM E-ll specifications for the number 20 sieve. In one embodiment, the abrasive bodies have a particle size such that most of the particles pass through an 18 mesh test sieve and can be retained on a 20, 25, 30, 35, 40, 45, or 50 mesh test sieve. In various embodiments of the disclosure, the abrasive bodies can have a nominal screened grade comprising: -18+20, -20+25, -25+30, -30+35, -35+40, -40+45, -45+50, -50+60, -60+70, -70+80,

-80+100, -100+120, -120+140, -140+170, -170+200, -200+230, -230+270, -270+325, -325+400,

-400+450, -450+500, or -500+635.

Optionally the sealed mixing vessel may contain a fluid such as, for example, water. The fluid may contain optional additives such as, for example, surfactant, defoamer, or in the case of abrasive bodies an etchant (e.g., an alkali metal hydroxide).

Useliil peening bodies may include any bodies known for use in shot peening. Examples include: spherical metal shot (e.g., cast steel, iron steel, stainless steel, tungsten, molybdenum, titanium, tantalum, cobalt-chrome, or cobalt), spherical ceramic/cermet beads (e.g., zirconia, alumina, silicon carbide, or tungsten carbide/cobalt), spherical glass beads, and conditioned (rounded) cut wire (e.g., conditioned cut steel wire). Conditioned cut wire shot may be preferred in some applications, because maintains its roundness as it is degraded, unlike cast shot which tends to break up into sharp pieces that can damage the workpiece. Conditioned cut wire shot can last five times longer than cast shot. Mixtures of two or more working body compositions, shapes, and/or sizes may be used. Usually, the peening bodies range in diameter from 0.1 millimeter (mm) to as large as 3.2 mm, preferably from 0.7 to 1.2 mm; however, this is not a requirement.

Peening may be beneficially practiced on metallic (e.g., including aluminum, steel, steel forgings and machine parts) workpieces. The effect of peening is a surface phenomenon that typically does not exceed several hundred microns in depth, so it is typically only necessary that the surface of the workpiece be metallic in order to achieve a benefit. However, in many instances the entire workpiece may be metallic.

Workpieces may include any article having a solid outer surface. Examples include manufactured parts comprising metal, ceramic, plastic, glass, composite, and combinations thereof. Exemplary workpieces include crank shafts, connecting rods, turbine blades, and cast or 3D-printed parts (e.g., engine components).

In practice of methods according to the present disclosure, the workpiece(s) may be placed in the finishing vessel as loose (i.e., unrestrained) items or they may be securely and reversibly mounted to the inner surface of finishing vessel, which is preferred in some embodiments.

Methods according to the present disclosure may be especially beneficial for workpieces, fabricated by powder jet or laser sintering additive manufacturing (3D printing) methods, since the working bodies and the workpiece may be free to move within the sealed chamber, the working bodies (if sufficiently small) can penetrate into interior passages that are accessible from the surface of the workpiece, and which may not be easily accessible using other methods.

SELECT EMBODIMENTS OF THE PRESENT DISCLOSURE In one embodiment, the present disclosure provides a method of finishing a surface of a workpiece, the method comprising: providing the workpiece disposed in a processing chamber of a vibratory finishing system comprising: a finishing vessel comprising the processing chamber bounded by a bottom surface, at least one sidewall surface, and atop surface, wherein the finishing vessel has at least one deflecting element disposed within the processing chamber, and wherein the at least one deflecting element is capable of deflecting a working body moving in a first linear direction, in a single collision, to a second direction that is oriented at least 30 degrees different than the first linear direction; and an actuator for linearly displacing the finishing vessel in a linearly reciprocating manner; disposing a plurality of the working bodies into the finishing vessel; and displacing the finishing vessel in the linearly reciprocating manner along the first linear direction such that the working bodies repeatedly contact the surface of the workpiece. In a second embodiment, the present disclosure provides a method according to the first embodiment, wherein the finishing vessel further comprises a mounting member for securely and reversibly fixturing a workpiece within the processing chamber, and wherein the workpiece is reversibly fixtured to the mounting member.

In a third embodiment, the present disclosure provides a method according to the first or second embodiment, wherein the finishing vessel is resonant-acoustically coupled to the actuator.

In a fourth embodiment, the present disclosure provides a method according to any of the first to third embodiments, wherein the working bodies comprise abrasive particles.

In a fifth embodiment, the present disclosure provides a method according to any of the first to fourth embodiments, wherein at least some of the working bodies are spheroidal or spherical.

In a sixth embodiment, the present disclosure provides a method according to any of the first to fifth embodiments, wherein the working bodies comprise shot particles.

In a seventh embodiment, the present disclosure provides a method according to any of the first to sixth embodiments, wherein the finishing vessel further comprises an upper portion and a lower portion that are adapted to releasably engage one another to define the processing chamber.

In an eighth embodiment, the present disclosure provides a method according to the seventh embodiment, wherein the finishing vessel further comprises a sleeve adapted to conformably engage at least one of the lower portion or the upper portion, and wherein the sleeve compnses at least one of the at least one deflecting element.

In a ninth embodiment, the present disclosure provides a finishing vessel comprising: a processing chamber bounded by a bottom surface, at least one sidewall surface, and a top surface, wherein the finishing vessel has at least one deflecting element disposed within the processing chamber, wherein the at least one deflecting element is capable of deflecting a spherical working body moving in a first linear direction, in a single collision, to a second direction that is oriented at least 30 degrees different than the first linear direction, and wherein the finishing vessel further comprises a mounting member for securely and reversibly fixturing a workpiece within the processing chamber.

In a tenth embodiment, the present disclosure provides a method according to the ninth embodiment, wherein the mounting member is securely fastened to the top surface.

In an eleventh embodiment, the present disclosure provides a method according to the ninth or tenth embodiment, wherein the at least one deflecting element comprises an insert adapted to fit within the processing chamber.

In a twelfth embodiment, the present disclosure provides a method according to any of the ninth to eleventh embodiments, wherein the finishing vessel is substantially cylindrical.

In a thirteenth embodiment, the present disclosure provides a method according to any of the ninth to twelfth embodiments, wherein at least one of said at least one deflecting element is adjacent to the bottom surface. In a fourteenth embodiment, the present disclosure provides a method according to any of the ninth to thirteenth embodiments, wherein at least one of said at least one deflecting element is adjacent to the at least one sidewall surface.

In a fifteenth embodiment, the present disclosure provides a method according to any of the ninth to fourteenth embodiments, wherein at least one of said at least one deflecting element is adjacent to the top surface.

In a sixteenth embodiment, the present disclosure provides a method according to any of the ninth to fifteenth embodiments, wherein the finishing vessel further comprises an upper portion and a lower portion that are adapted to engage one another to define the processing chamber.

In a seventeenth embodiment, the present disclosure provides a method according to the ninth to sixteenth embodiment, wherein the finishing vessel further comprises a sleeve adapted to conformably engage at least one of the lower portion or the upper portion, and wherein the sleeve comprises at least one of the at least one deflecting element.

Objects and advantages of this disclosure are further illustrated by the following non-limiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure.

EXAMPLES

Unless otherwise noted, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight.

The mixing/agitating system used for all examples described below was a LabRAM Resonant Acoustic mixer from Resodyn Corporation, Butte, Montana. The system, which was equipped with a sealed mixing vessel, was ran at 100% intensity in the auto frequency mode.

EXAMPLE 1

This example demonstrates a greater surface finish improvement on the vertical faces of a mounted workpiece in a finishing vessel containing deflecting elements, as compared to a vessel containing no such elements, during a peening process. Roughness measurements: R _a , were made using a MarSurf PS 10 stylus profilometer, Mahr, Gottingen, Germany.

The workpiece was a machined aluminium alloy (Grade BS EN 755 6082-T6) 16 mm X 3 mm x 50 mm cuboid with a surface roughness R _a of 4.5 microns. The vessel used was polypropylene of 50 mm diameter and 100 mm height. Glass spheres (100 g, 2 mm diameter) were placed in the finishing vessel, with and without deflecting elements. The finishing vessel (as shown in FIGS. 2A-2D, except that no insert 265 was present) had a cover/lid with a mounting member, straight vertical walls, and a flat horizontal base, without deflecting elements, and was obtained from VWR International, Radnor, Pennsylvania. The workpiece was attached by screws to the mounting member so that the main faces (16 mm x 50 mm) were vertical facing the walls. The LabRAM system was run for 15 mins, after which an 8 percent reduction in R _a was measured on the main faces of the cuboid (R _a was reduced to 4.1 microns).

The reduction in roughness was due to peening from the spheres on the surface, compressing the peaks in the roughness profile. The above procedure was repeated, except that the insert 265 shown in FIGS. 2A-2D was placed in the vessel. The deflecting elements had a 6 mm height, a slope of 45 degrees from the sidewall to their tip, and a deflecting element spacing of 20 mm. A 45 percent reduction in R _a was measured on the main faces of the cuboid (R _a was reduced to 2.5 microns). All cited references, patents, and patent applications in this application are incorporated by reference in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in this application shall control. The preceding description, given in order to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.