Method for forming tooling and fabricating parts therefrom

A method of forming tooling for fabricating a part made from a metal powder is described herein. The method includes forming a first sheet and second sheet. The first sheet includes a first protrusion defining a first cavity and a first flange extending about the first protrusion. The second sheet includes a second flange. Additionally, the method includes arranging the first sheet and the second sheet to abut together the first flange of the first sheet and the second flange of the second sheet and to define an enclosure. The enclosure includes a void defined between the first cavity of the first sheet and the second sheet. The void has a shape of the part. The method further includes welding together the first flange of the first sheet and the second flange of the second sheet along a portion of the first flange spaced away from the first protrusion.

FIELD

This disclosure relates generally to the fabrication of parts into desired shapes, and more particularly to forming tooling and fabricating parts made from metal powder into desired shapes using such tooling.

BACKGROUND

The fabrication of parts using powder metallurgy offers advantages over traditional metallurgy. For example, parts made from powder metallurgy often are fabricated at lower costs, closer to net shape, and with improved metal alloys compared to traditional metallurgy.

Conventional powder metallurgy techniques include encapsulating and consolidating metal powders within an enclosure. The enclosure is formed by welding together two or more metal sheets. Conventional techniques for welding sheets together to form an enclosure include placing welds in the portion of the sheets defining the space used to shape the part. Such welds tend to impart residual stress on the sheets, which can cause the sheets to twist and deform during fabrication of the part.

Further, according to traditional techniques, the enclosures are limited to forming parts with only rudimentary or simple shapes. To fabricate parts into final shapes that are more complex, a significant amount of material must be machined away from the parts, which increases the time and complexity associated with fabrication of the parts. Traditionally, a ratio of a total volume of the rudimentary shape to a total volume of the final machined shape is at least between about 30 and about 60. Because metal powders are relatively expensive, the loss of material associated with machining parts with rudimentary shapes into more complex shapes results in added manufacturing costs.

SUMMARY

The subject matter of the present application provides embodiments of methods for forming tooling, and associated methods and apparatuses for fabricating a part made from metal powder, that overcome the above-discussed shortcomings of prior art techniques. In other words, the subject matter of the present application has been developed in response to the present state of the art, and in particular, in response to shortcomings of conventional methods and apparatuses for forming tooling used to fabricate parts made from metal powder.

According to one embodiment, a first method of forming tooling for fabricating a part made from a metal powder includes forming a first sheet. The first sheet includes a first protrusion that defines a first cavity and a first flange that extends about an entire periphery of the first protrusion. The first method also includes forming a second sheet that includes a second flange. Additionally, the first method includes arranging the first sheet and the second sheet adjacently to each other to abut together the first flange of the first sheet and the second flange of the second sheet and to define an enclosure. The enclosure includes a void defined between the first cavity of the first sheet and the second sheet. The void has a shape of the part. The first method further includes welding together the first flange of the first sheet and the second flange of the second sheet along a portion of the first flange spaced away from the first protrusion.

In some implementations of the first method, the second sheet includes a second protrusion that defines a second cavity. The second flange extends about an entire periphery of the second protrusion. The void is defined between the first cavity of the first sheet and the second cavity of the second sheet. Welding together the first flange of the first sheet and the second flange of the second sheet includes welding along a portion of the second flange spaced away from the second protrusion.

According to certain implementations of the first method, welding together the first flange of the first sheet and the second flange of the second sheet includes forming a continuous weld about the entire peripheries of the first protrusion of the first sheet and the second protrusion of the second sheet. The continuous weld can be spaced the same distance away from the first protrusion of the first sheet and the second protrusion of the second sheet about the entire peripheries of the first protrusion and the second protrusion. The continuous weld can be spaced a distance away from the first protrusion and the second protrusion. The distance is at least 0.125 inches in some implementations.

In certain implementations of the first method, the first cavity has a first three-dimensional shape and the second cavity has a second three-dimensional shape. The first three-dimensional shape of the first cavity can be the same as the second three-dimensional shape of the second cavity. A shape of the first protrusion may complement the first three-dimensional shape of the first cavity, and a shape of the second protrusion may complement the second three-dimensional shape of the second cavity. At least one of the first three-dimensional shape of the first cavity and the second three-dimensional shape of the second cavity can have a complex geometry.

According to some implementations of the first method, a periphery of the first protrusion is the same shape and size as a periphery of the second protrusion. Arranging the first sheet and the second sheet adjacently to each other includes aligning the peripheries of the first protrusion and the second protrusion.

In one implementation of the first method, the first flange and the second flange are planar.

According to certain implementations, the first method further includes forming a through-channel in at least one of the first flange and the second flange. The through-channel is open to the void at a first end of the through-channel and open to an exterior of the enclosure at a second end of the through-channel opposite the first end of the through-channel.

In certain implementations of the first method, the first flange of the first sheet and the second flange of the second sheet are welded together via friction stir welding. In further implementations of the first method, at least one of the first sheet and the second sheet are formed via incremental sheet forming.

According to one embodiment, a second method of fabricating a part made from a metal powder includes forming a first sheet. The first sheet includes a first protrusion that defines a first cavity and a first flange that extends about an entire periphery of the first protrusion. The second method also includes forming a second sheet. The second sheet includes a second protrusion that defines a second cavity and a second flange that extends about an entire periphery of the second protrusion. The second method further includes arranging the first sheet and the second sheet adjacently to each other to abut together the first flange of the first sheet and the second flange of the second sheet and to define an enclosure. The enclosure includes a void defined between the first cavity of the first sheet and the second cavity of the second sheet. The void has a shape of the part. Additionally, the second method includes welding together the first flange of the first sheet and the second flange of the second sheet along a portion of the first flange spaced away from the first protrusion and a portion of the second flange spaced away from the second protrusion. The second method also includes filling the void of the enclosure with metal powder. Further, the second method includes heating the enclosure and metal powder in the void of the enclosure to a threshold temperature and pressurizing the enclosure and metal powder in the void of the enclosure to a threshold pressure to form a part in the void of the enclosure. The second method also includes removing the part from the enclosure.

In some implementations of the second method, the part in the void of the enclosure has an intermediate shape. The second method can further include shaping the part from the intermediate shape to a final shape. A ratio of a total volume of the intermediate shape and a total volume of the final shape can be less than about 6. The final shape of the part is a complex three-dimensional shape in certain implementations.

According to some implementations of the second method, the first cavity has a first three-dimensional shape and the second cavity has a second three-dimensional shape. The void can have a third-three-dimensional shape that includes a combination of the first three-dimensional shape and the second three-dimensional shape. The part in the void of the enclosure has the third three-dimensional shape.

In certain implementations, the second method also includes forming a through-channel in at least one of the first flange and the second flange. The through-channel is open to the void at a first end of the through-channel and open to an exterior of the enclosure at a second end of the through-channel opposite the first end of the through-channel. The second method further includes passing the metal powder through the through-channel to fill the void of the enclosure.

According to yet another embodiment, an apparatus for fabricating a part made from a metal powder includes a first sheet with a first protrusion that defines a first cavity and a first flange that extends about an entire periphery of the first protrusion. The apparatus also includes a second sheet with a second protrusion that defines a second cavity and a second flange that extends about an entire periphery of the second protrusion. The second flange of the second sheet abuts the first flange of the first sheet to define a void between the first cavity of the first sheet and the second cavity of the second sheet. The void has a shape of the part. The apparatus also includes a continuous weld formed in the first flange and the second flange. The continuous weld is spaced apart from the first protrusion of the first sheet and the second protrusion of the second sheet.

DETAILED DESCRIPTION

Referring toFIGS. 1-9, and according to one embodiment, an enclosure100for fabricating a part190made from metal powder180or powdered metal is shown. The enclosure100includes a first sheet110and a second sheet112. The first sheet110is coupled to the second sheet112to form the enclosure100. Moreover, the first sheet110includes a first protrusion114and the second sheet112includes a second protrusion116. Extending about a periphery125of the first protrusion114is a first flange118. Similarly, extending about a periphery127of the second protrusion116is a second flange120. In the illustrated embodiment, the first flange118extends about the entire periphery125of the first protrusion114, and the second flange120extends about the entire periphery127of the second protrusion116. In this manner, on a given plane or curved surface, the first and second flanges118,120effectively surround the first and second protrusions114,116. The first protrusion114includes one or more sidewalls122and a fillet124, and the second protrusion116includes one or more sidewalls126and a fillet128. The fillets124,128provide a radiused transition region between the sidewalls122,126, and the first and second flanges118,120, respectively. Although the first and second protrusions114,116include fillets124,128between the sidewalls122,126and the first and second flanges118,120, in some implementations, the first and second protrusions114,116do not include fillets such that the sidewalls transition directly into the first and second flanges without a radiused or otherwise gradual transition region.

As shown inFIG. 5, the first and second protrusions114,116define first and second cavities150,152, respectively. More specifically, an interior surface164of the first protrusion114defines the first cavity150, and an interior surface166of the second protrusion116defines the second cavity152. Therefore, the shape and size of the interior surfaces164,166of the first and second protrusions114,116define the shape and size of the first and second cavities150,152, respectively. The interior surfaces164,166can have any of various shapes and sizes to define first and second cavities150,152with any of various complementary shapes and sizes. In the illustrated embodiment, the interior surfaces164,166are shaped to define first and second cavities150,152with three-dimensional shapes. As defined herein, a three-dimensional shape is a shape with complex geometries or a shape with at least one portion extending at an angle relative to another portion such that an interior angle is defined between the portions. The three-dimensional shapes of the first and second cavities150,152in the illustrated embodiment are just one example of any of an infinite number of possible three-dimensional shapes that could be defined by the interior surfaces164,166of the first and second protrusions114,116, respectively. In other words, the first and second protrusions114,116can be configured differently than those shown to have interior surfaces164,166that define three-dimensional shapes different than those shown without departing from the essence of the present disclosure. For example, the three-dimensional shapes of the first and second cavities150,152can be more or less complex than the three-dimensional shapes shown in the illustrated embodiments.

The size and shape of the first and second cavities150,152can be the same or different depending on a desired shape of the part being fabricated. In the illustrated embodiment, the size and shape of the first and second cavities150,152are the same such that the shape of the part190is symmetrical across its midline. Alternatively, the size and shape of the first and second cavities150,152can be differently sized, differently shaped, or both differently sized and shaped to produce a part that is asymmetrical.

The first and second protrusions114,116extend perpendicularly or obliquely away from the first and second flanges118,120, respectively. Referring toFIGS. 5 and 6, the first flange118includes an outer surface170and an opposing interface surface174, and the second flange120includes an outer surface172and an opposing interface surface176. The interface surfaces174,176of the first and second flanges118,120, respectively, are shaped to complement and sit flush against each other. In this manner, a weld130can be properly formed in the first and second flanges118,120across the interface surfaces174,176to couple together the flanges, and thus coupled together the first and second sheets110,112. Additionally, in this manner, the weld130effectively seals the void154of the enclosure100.

Although both the first and second protrusions114,116are shown to define first and second cavities150,152both with three-dimensional shapes, in some embodiments, one of the first and second cavities150,152may have a three-dimensional shape, while the other of the first and second cavities does not. For example, in one embodiment, the first sheet110has a protrusion that defines a three-dimensional cavity, and the second sheet112does not have a protrusion. Although the second sheet112may be a flat sheet, because the cavity of the protrusion of the first sheet110is three-dimensional, the resulting part also will be three-dimensional.

In some embodiments, such as in the illustrated embodiment, the first and second flanges118,120are planar. In other words, the interface surfaces174,176of the first and second flanges118,120are planar (e.g., flat). For example, as in the illustrated embodiment, the interface surface174of the first flange118can be co-planar about the entire periphery125of the first protrusion114, and the interface surface176of the second flange120can be co-planar about the entire periphery127of the second protrusion116, such that when coupled together the entirety of the first and second flanges are parallel to each other. However, in other embodiments, although planar, some portions of the first flange118are not co-planar with other portions of the first flange, and some portions of the second flange120are not co-planar with other portions of the second flange. For example, one side of the interface surfaces174,176of the first and second flanges118,120may be angled in a first direction and another side of the first and second flanges may be non-angled or angled in a different direction.

According to other embodiments, the first and second flanges118,120are non-planar. In other words, the interface surfaces174,176of the first and second flanges118,120can be sharply or gradually contoured. For example, in certain implementations, the interface surfaces174,176may be rounded, pointed, or the like. In some implementations, one of the interfaces surfaces174,176is concave and the other of the interface surfaces is convex, such that the convex surface is nestably engaged with the concave surface.

Referring toFIG. 3, the first and second flanges118,120each have an outer periphery119. The outer periphery119of each of the first and second flanges118,120can be any of various shapes and sizes. Moreover, the size and shape of the outer peripheries119of the first and second flanges118,120can be the same or different. As shown, in some implementations, the outer peripheries119of the first and second flanges118,120have the same shape and size for facilitating ease in forming and handling the enclosure100. The shape of the outer peripheries119in the illustrated implementation is substantially square or rectangular. However, in other implementations, the shape of the outer peripheries119can be non-square or non-rectangular, such as, for example, circular, ovular, triangular, and the like. Alternatively, the shape of the outer peripheries119of the first and second flanges118,120can be the same as the shape of the corresponding outer peripheries25,27of the first and second protrusions114,116.

The first protrusion114and the first flange118of the first sheet110form a one-piece monolithic construction, and the second protrusion116and the second flange120of the second sheet112form a one-piece monolithic construction, in some embodiments. In the illustrated embodiment, each of the first and second sheets110,112has a constant thickness across at least one of the respective protrusions and flanges of the first and second sheets. For example, in one implementation, the first protrusion114of the first sheet110has a constant thickness, and the second protrusion116of the second sheet112has a constant thickness. In such an implementation, an exterior surface160of the first protrusion114complements (e.g., has the same shape and size as) the interior surface164of the first protrusion. Likewise, in such an implementation, an exterior surface162of the second protrusion116complements the interior surface166of the second protrusion. In the same or an alternative example, the flange118of the first sheet110has a constant thickness and the flange120of the second sheet112has a constant thickness. In yet some embodiments, the thickness across at least one of the respective protrusions and flanges of the first and second sheets110,112may vary. Whether constant or varying, the thickness of the first and second sheets110,112(e.g., distance between interior and exterior surfaces) is much smaller than the width and length of the sheets such that the first and second sheets have a generally sheet-like configuration.

Referring toFIG. 10, a method200of forming tooling for fabricating a part made from a metal powder includes forming a first sheet, such as the first sheet110, that has a protrusion and a flange extending about a periphery of the protrusion at210. Similarly, the method200includes forming a second sheet, such as the second sheet112, that has a protrusion and a flange extending about a periphery of the protrusion at220. The first and second sheets110,112can be made from any of various materials and formed using any of various manufacturing techniques. According to one embodiment, the first and second sheets110,112are made from a material such as, for example, metal, ceramic, polymer, fiber-reinforced composite, and combinations thereof. In some implementations, the first and second sheets110,112are made from a metal or metal alloy, such as aluminum, steel, and the like. According to one embodiment, the first and second sheets110,112are formed using a manufacturing technique such as, for example, casting, molding, machining, stamping, forging, bending, peening, and the like. In some implementations, the first and second sheets110,112are made using an incremental sheet forming (ISF) technique. ISF techniques are useful for forming complex three-dimensional shapes, such as the shapes of the first and second protrusions114,116. Generally, ISF techniques include repeatedly imparting small incremental and localized deformations to a material using an impact tool until a desired shape of the material is achieved. Often, the impact tool is precisely controlled by a computerized numerically-controlled (CNC) machine to produce desired shapes with tight tolerances.

After the first and second sheets are formed at210,220, respectively, the method200includes abutting together the flanges of the first and second sheets to define a void between cavities defined by the protrusions of the first and second sheets at230. In other words, the method200includes arranging the first and second sheets adjacently to each other such that the flanges of the sheets abut each other. More specifically, in the illustrated embodiment as shown inFIG. 5, the interface surfaces174,176of the first and second flanges118,120, respectively, abut each other. As described above, the interface surfaces174,176can be configured to sit flush against each other about substantially the entire peripheries125,127of the respective protrusions114,116. The peripheries125,127of the first and second protrusions114,116can have the same shape and size. Moreover, abutting the first and second flanges118,120at230can include arranging the first and second sheets110,112adjacently to each other such that the peripheries125,127of the first and second protrusions114,116are aligned. Alignment of the peripheries125,127can be defined as being aligned in a direction perpendicular to an interface plane or midplane between the first and second protrusions114,116. From the perspective shown inFIG. 5, the peripheries125,127can be aligned in a direction extending from top-to-bottom of the page or a vertical direction. Alignment of the peripheries125,127of the first and second protrusions114,116may also include alignment of the peripheries of the first and second cavities150,152defined by the first and second protrusions.

After the first and second sheets are arranged adjacently to each other and the first and second flanges abut each other, the method200includes welding together the first and second flanges at240to fixedly couple together the first and second sheets to form an enclosure. The weld or weldment formed in the first and second flanges at240of the method200is spaced away from the first and second protrusions of the first and second sheets, respectively. In certain implementations, the weld is spaced away from the first and second protrusions by being non-adjoining or non-coincident with the protrusions. In other words, some portion of the flange is positioned between the weld and the protrusions. Spacing the weld away from the protrusions prevents residual stresses from being formed in and deformation of the protrusions by the weld.

Referring toFIGS. 5 and 6, in the illustrated embodiment, the weld130is formed in the first and second flanges118,120and spaced a predetermined distance D away from the peripheries125,127of the first and second protrusions114,116. In some implementations, the predetermined distance D is the same about the entire peripheries125,127of the first and second protrusions114,116. The distance D is defined between the outermost extents of the first and second peripheries125,127and an innermost extent of the inner periphery132of the weld130. The inner periphery132of the weld130opposes an outer periphery134of the weld. The inner and outer peripheries132,134of the weld130are defined as the respective peripheries of the portions of the first and second flanges118,120that are thermomechanically affected by the welding process. Accordingly, the inner and outer peripheries132,134of the weld130can be defined as the interface or transition between the region of the first and second flanges118,120thermomechanically affected by the welding process and the region of the flanges thermomechanically unaffected by the welding process. The distance D is greater than zero. In some implementations, the distance D is at least 0.125 inches. In yet certain implementations, the distance D is between 0.05 inches and about 0.5 inches. According to some implementations, the distance D calculated based on a diameter of the pin and shoulder portions of a wear-resistant rotating tool for friction stir welding (FSW) processes, an estimated width of the heat affected zone of the weld130, and a preferred dimension for clearance between the tool and a tangency point of radii of fillets124,128, respectively.

The weld130can be formed using any of various fusion welding techniques configured to thermomechanically alter the materials of adjoining sheets to permanently mix together the materials and join together the sheets. For example, the weld130can be formed using friction stir welding (FSW), laser welding, arc welding, and the like. FSW techniques include the use of a wear-resistant rotating tool to join adjoining sheets together. The rotating tool includes a shoulder from which extends a profiled pin. In the illustrated embodiment, the shoulder frictionally engages or presses against the outer surface170,172of one of the flanges118,120of the first and second sheets110,112. With the shoulder against the outer surface of a flange, the profiled pin penetrates at least partially through both the first and second flanges118,120. Friction due to rotation of the tool generates heat in the material of the first and second flanges118,120. The heat generated by the rotating tool is sufficient to soften the material and thermomechanically alter the material without melting the material. The softened material of the first and second flanges118,120is stirred together and allowed to cool (e.g., harden) to permanently join together the material and thus the first and second flanges.

A continuous weld, as opposed to a spot weld, is formed in a desired pattern using FSW techniques by translationally moving the rotating tool, while engaging and thermomechanically altering the flanges, along the outer surface of one of the flanges in the desired pattern. As mentioned above, the desired pattern complements the shape of the outer peripheries125,127of the first and second protrusions114,116. Generally, the diametric extent or periphery of the shoulder of the tool defines the inner and outer peripheries132,134of the weld130. In other words, thermomechanical alternation of the material of the first and second flanges118,120is contained within the footprint of the shoulder of the rotating tool. In this manner, controlling the position of the shoulder of the rotating tool relative to the outer peripheries125,127of the first and second protrusions114,116also controls the location of the weld130relative to the outer peripheries of the first and second protrusions. Therefore, the rotating tool is positioned such that the shoulder of the rotating tool is the predetermined distance D away from the outer peripheries125,127of the protrusions, which results in the weld130being the desired distance D away from the outer peripheries.

After the flanges of the first and second sheets are welded together at240to form an enclosure defining a void, the method200includes filling the void with metal powder at250. In the illustrated embodiment, the void154of the enclosure100is filled with metal powder180by passing the metal powder through a through-channel140formed in the enclosure100. Accordingly, filling the void with metal powder at250may include forming a through-channel in at least one of the flanges of the first and second sheets of the enclosure. The through-channel140can be formed in at least one of the first and second flanges118,120of the first and second sheets110,112, respectively. As shown, the through-channel140is defined by two opposing sub-channels140A,140B formed in the interface surfaces174,176of the first and second flanges118,120, respectively. In other words, half of the through-channel140is formed in the first flange118and the other half of the through-channel is formed in the second flange. In alternative embodiments, the entirety of the through-channel140can be formed in one or the other of the first and second flanges118,120. Notwithstanding how the through-channel140is formed, the through-channel is configured to be open to the void on one end and open to an exterior of the enclosure100on another other end. Accordingly, the through-channel140extends through the flanges118,120and into the void154In this manner, after the enclosure100is formed, access to the void154, such as for passing metal powder180into the void, is available from outside the enclosure.

The metal powder180can be any of various metal powders known in the art. For example, in some implementations, the metal powder is one or more of an aluminum powder, an iron powder, and the like. The metal powder180may include additives, such as lubricant wax, carbon, copper, and nickel, that help to bind the metal powder together during a part forming process. Although a metal powder is the focus of the present disclosure, non-metal powders may be used.

After the void of the enclosure is filled with metal powder at250, the method200may include evacuating air from the void in preparation for a part forming process. The air may be removed using a vacuum pump or other similar device. In one implementation, a vacuum pump evacuates air from within the void using the same through-channel used to supply metal powder into the void. However, according to other implementations, a secondary through-channel is used to evacuate air from the void.

When the enclosure is filled with metal powder and air is evacuated from the void, the through-channel(s) are sealed. The through-channel(s) can be sealed using any of various methods, such as welding shut the through-channel(s), collapsing the through-channel(s), and the like. In the illustrated implementation, the through-channel140is welded shut using the same welding technique used to join together the first and second flanges118,120. In other implementations, the through-channel can be welded shut using a different welding technique. Because in some implementations the through-channel140may not be welded shut using the same continuous weld130formed around the peripheries125,127of the protrusions114,116, or may be collapsed shut, as defined herein a weld is a continuous weld in the flanges about an entire periphery of the protrusions if the weld in the flanges extends about the entire periphery of the protrusions but for the portion of the flanges occupied by the through-channel.

After the void of the enclosure is filled with metal powder, air is evacuated from the void, and the through-channel(s), or other means used to fill the void and evacuate the air, is sealed, the method200includes heating and pressurizing the metal powder to form a part at260. Referring toFIG. 8, pressure186and heat188applied to the enclosure100also pressurizes (e.g., compacts) and heats the metal powder180. The pressure186and heat188are interdependently selected to achieve a desired density or compactness of the part, such as the part190. In some implementations, the pressure186can be between about 2,000 psi and about 40,000 psi. The heat188can include temperatures between about 900° F. and about 2,250° F. In some implementations, the enclosure100and the metal powder180is pressurized and heated in a hot isostatic pressure (HIP) chamber as is commonly known in the art.

After the metal powder is heated and pressurized such that the formed part is compacted to a desired density, the method200includes removing the part from the void of the enclosure at270. In some implementations, the part can be removed from the void of the enclosure by cutting through the enclosure. For example, a cutting tool may be employed to cut through one or both of the first and second sheets110,112to form an opening through which the part190can be removed. Removing the part190can also include bending or peeling back the cut sheets to access the part190.

The shape of the part in the enclosure, and the shape of the part upon being removed from the enclosure, can be considered to have an intermediate three-dimensional shape. In certain embodiments, the part is further shaped from the intermediate three-dimensional shape into a final three-dimensional shape. Further shaping of the part from the three-dimensional shape to the final three-dimensional shape can include removing material from the part. The final three-dimensional shape of the part can be defined as the shape of the part during use for its intended purpose. Because the enclosure100and method200of forming tooling and fabricating a part using the tooling facilitate the formation of complex three-dimensional parts, only a minimal amount of material is removed from the part with the intermediate three-dimensional shape to achieve the final three-dimensional shape. In some implementations, a ratio of a total volume of the intermediate shape to a total volume of the final shape is less than or equal to between about 3.0 and about 6.0.