Embodiments of the present disclosure generally relate to additive manufacturing of three-dimensional objects.
Additive manufacturing refers to any process for manufacturing a three- dimensional object in which successive layers of base material are deposited under computerized control. For example, the size and shape of the object may be based on a three-dimensional computer model or another electronic data source. Additive manufacturing can be used to fabricate objects that have complex structures and/or shapes. Additive manufacturing techniques for fabricating metal objects may be less labor intensive, may allow greater design freedom, and may yield more precise and repeatable finished products than conventional metal manufacturing techniques, such as die-casting, extruding, and the like.
At least one known additive manufacturing technique, which is referred to herein as selective laser melting (or sintering), builds a metal object within a powder bed including metal powder. For example, the object sits on a platform and is fully encased within the powder bed such that the top of the object is covered by a thin layer of metal powder. An energy source above the top of the object heats a selected portion of the thin layer of the metal powder to fuse the portion onto the top of the object, forming a new top layer of the object.
However, the metal object may experience substantial residual stresses and/or deformation during the manufacturing process due at least in part to large thermal gradients between different sections of the metal object. For example, the temperature at the top of the metal object where the new top layer is formed may be significantly greater than a section of the metal object closer to the bottom of the metal object, and the resulting residual stress can cause deformation and even crack formation in the metal object. Heating the lower section of the metal object that is within the powder bed to reduce the temperature gradient (and therefore reduce the residual stress) is impractical because the heat may cause the metal powder in the bed to fuse together and coalesce. The fused powder in the bed may have to be discarded instead of being reusable. For these reasons, attempting to heat the metal object in the powder bed greatly increases the amount of powder used (and wasted) during the additive manufacturing process relative to not heating the metal object in the bed.
The additive manufacturing techniques that build metal objects in powder beds have several other disadvantages in addition to the risk of deformation and/or cracking due to residual stress. For example, the size of the fabricated object is limited to the size of the tank that confines the powder and the amount of powder available. The production of relative large metal objects may require several tons of metal powder within the powder bed, which may be costly to obtain and maintain. Furthermore, because the temperature of the powder bed may be relatively cool (e.g., at or close to ambient temperature), the build speed may be limited because more time is necessary for the energy source to heat up and melt the metal powder onto the top layer of the metal object than if the metal object and/or the metal powder were maintained at a greater temperature. Varying the composition of the metal object that is being fabricated by changing the type of metal powder that is deposited in between successive layers is also difficult and potentially wasteful because intermixing of multiple different types of powders within the powder bed may contaminate the powders and require the entire powder bed to be discarded.
Certain embodiments of the present disclosure provide an additive manufacturing system that includes a plate, a build support device, at least one electromagnetic energy source, and one or more processors. The plate is at least semitransparent. The build support device is configured to couple to an object. The build support device is movable relative to the plate to move the object into and out of contact with a stratum of a powder distributed on a first side of the plate. The powder includes metal particles. The one or more processors are operably connected to the at least one electromagnetic energy source and configured to control the at least one electromagnetic energy source to emit one or more energy beams that penetrate through the plate and impinge upon a selected portion of the powder in the stratum upon exiting the plate to form a layer of the object.
Certain embodiments of the present disclosure provide a method for additive manufacturing that includes distributing a first stratum of a powder on a first side of a plate. The powder includes metal particles and the plate is at least semitransparent. The method includes moving an object towards the first side of the plate into contact with the first stratum of the powder. The method also includes directing one or more energy beams from at least one electromagnetic energy source to penetrate through the plate and impinge upon a first selected portion of the powder in the first stratum upon exiting the plate to form a first layer of the object.
Certain embodiments of the present disclosure provide an additive manufacturing system that includes a plate, a powder, a spreader, and at least one electromagnetic energy source. The plate is at least semitransparent. The powder includes metal particles, and is deposited on a top side of the plate. The spreader is mounted above the top side of the plate and is movable across the plate to disperse the powder into a stratum having a designated thickness. The at least one electromagnetic energy source is disposed below a bottom side of the plate that is opposite the top side. The at least one electromagnetic energy source is configured to emit one or more energy beams towards the plate such that the one or more energy beams penetrate through the plate and impinge upon a selected portion of the powder in the stratum upon exiting the plate to melt the selected portion of the powder and form a layer on an object that is held in contact with the stratum.
These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like numerals represent like parts throughout the drawings, wherein:
The foregoing summary, as well as the following detailed description of certain embodiments will be better understood when read in conjunction with the appended drawings. As used herein, an element or step recited in the singular and preceded by the word “a” or “an” should be understood as not necessarily excluding the plural of the elements or steps. Further, references to “one embodiment” are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising” or “having” an element or a plurality of elements having a particular property may include additional elements not having that property.
Embodiments of the present disclosure provide systems and a method for fabricating three-dimensional objects (e.g., work pieces, parts, products, etc.) via additive manufacturing. In one or more of the embodiments, the objects are metallic and are fabricated from a powder including metal particles. For example, the powder is heated or otherwise energized by one or more electromagnetic energy sources, which melts and/or fuses the energized powder onto a surface of the object. The energized powder that adheres to the object solidifies upon cooling to form a new layer of the object, and the process repeats layer by layer in series until the object is completed. The additive manufacturing systems described herein may be fully automated, such that the systems do not require operator intervention once a build operation is commenced. As described herein in more detail, the additive manufacturing systems of the present disclosure may be able to produce metal objects of various shapes and sizes with a reduced risk of distortion and/or cracks in the objects, reduced powder waste, reduced amount of powder required, and/or a faster build speed than known additive manufacturing systems designed to fabricate metal objects. The additive manufacturing systems may also have additional benefits over known additive manufacturing systems, as described herein.
The object 118 may be generated layer-by-layer in a successive sequence by the one or more electromagnetic energy sources 106 emitting electromagnetic energy beams that impinge upon a layer or stratum of the powder 116, causing a selected portion of the stratum to adhere to the object 118 and form a new layer of the object 118. The emission and direction of the electromagnetic energy beams are controlled by the control unit 108, which is operably connected to the one or more electromagnetic energy sources 106 via a wired or wireless communication pathway. The AM system 100 has one electromagnetic energy source 106 in the illustrated embodiment, but the AM system 100 may include multiple electromagnetic energy sources 106 arranged in an array or a line in another embodiment.
In one example, the powder 116 may be homogenous, including a single type of metal or metal alloy material without additional non-metallic filler particles (e.g., non-metallic filler materials). The metal or metal alloy material of the powder 116 may include various metal types, such as aluminum, stainless steel, copper, nickel, cobalt, titanium, or the like, and alloys of the various metal types. In another example, the powder 116 includes multiple different types of metals and/or metal alloys, with or without non-metallic filler materials. Possible non-metallic filler materials within the powder 116 may include ceramics, polymers, silica, or the like. The powder reservoir 114 that contains the powder 116 is able to selectively release specific quantities of the powder 116 onto the plate 102. The powder reservoir 114 includes a valve 120 along a spout 122 of the powder reservoir 114. The valve 120 is able to open and close to control the deposition of powder 116 from the powder reservoir 114. The valve 120 may be operable connected to the control unit 108, such that the control unit 108 may be selectively opened and closed in response to control signals received from the control unit 108. In
The plate 102 is disposed between the electromagnetic energy source 106 and the object 118 that is being fabricated. The plate 102 has the first side 126 and a second side 128 opposite the first side 126. In the illustrated embodiment, the build support device 104, the heating appliance 112, the object 118, the spreader 110, and the powder reservoir 114 are located along the first side 126 of the plate 102 such that the first side 126 faces towards these components with or without the components mechanically contacting or engaging the first side 126. The electromagnetic energy source 106 is located along the opposite, second side 128 of the plate 102.
The AM system 100 is oriented with respect to a lateral axis 191, a height axis 192, and a longitudinal axis 193. The axes 191-193 are mutually perpendicular. The longitudinal axis 193 extends into and out of the page in the illustrated orientation. The axes 191-193 are not required to have any particular orientation with respect to gravity. In at least one embodiment, the height axis 192 extends in a vertical direction generally parallel to the force of gravity. For example, the first side 126 of the plate 102 in
The plate 102 is at least semitransparent, and may be fully transparent. The electromagnetic energy beams emitted from the electromagnetic energy source 106 penetrate through a thickness of the plate 102 before impinging upon a stratum of the powder 116 to fuse a selected portion of the powder 116 onto the object 118. The plate 102 is rigid. The first and second sides 126, 128 may be planar and parallel to one another. The plate 102 may be or include glass, alumina, polycarbonate, or the like. In a non-limiting example, the plate 102 is composed of single crystal sapphire (e.g., alumina) material.
The heating appliance 112 includes an enclosure 130 that at least partially surrounds the object 118 during the build process. The heating appliance 112 also includes a heating element 132 that generates thermal energy (i.e., heat) within the enclosure 130. The heating appliance 112 regulates the temperature of the object 118. For example, the heating appliance 112 may heat the object 118 during the build process such that an internal temperature of the object 118 is greater than an ambient, room temperature outside of the enclosure 130. The raised temperature of the object 118 may allow the powder 116 to more readily adhere to the object 118 than if the object 118 is not heated. For example, the portion of the powder 116 upon which the electromagnetic energy beams impinge may adhere to the heated object 118 more quickly and/or with less beam energy required than if the object 118 was not heated, which may enable faster and/or more efficient fabrication of the object 118.
The enclosure 130 may fully or only partially surround the object 118. The enclosure 130 in
The heating element 132 may include electrically resistive elements that convert electrical energy (i.e., current) into thermal energy that is supplied into the enclosure 130. For example, heating element 132 may be conductively connected to a power source, such as a wall outlet via an electrical cable, to receive current for generating heat. The heating element 132 may include control circuitry and/or devices (e.g., switches, relays, etc.) that regulates the heat generated and supplied into the enclosure to control the temperature within the enclosure 130. The control unit 108 may be operably connected to the heating element 132 via a wired or wireless connection. The control unit 108 may communicate electrical signals to the heating element 132 to control the heating element 132 in order to maintain the temperature within the enclosure 130 and/or the internal temperature of the object 118 at a designated temperature or within a designated temperature range. For example, the designated temperature of the object 118 during the build process may be greater than 100° F. (56° C.), such as, but not limited to, 200° F. (111° C.), 300° F. (167° C.), or 500° F. (278° C.). The designated temperature may be selected to be below, but relatively close to, a melting temperature of the powder 116, such as within a designated range (e.g., within 100° F. or within 200° F.) of the melting temperature.
The build support device 104 is coupled to the object 118 and is movable relative to the plate 102 to reciprocally move the object 118 between a contact position and a separated position. In the separated position, the build support device 104 holds the object 118 spaced apart from the first side 126 of the plate 102. The object 118 is in the separated position in
The build support device 104 may include a platform 140 that couples to the object 118 and a linear drive mechanism 142 that moves the platform 140 relative to the plate 102. The platform 140 removably couples to the object 118 via one or more of adhesive, fasteners (e.g., nuts and bolts, etc.) clips, latches, bands, hooks, or the like. The platform 140 is coupled to a proximal end 150 of the object 118 in the illustrated embodiment. The proximal end 150 of the object 118 is opposite to a distal end 152 of the object 118. The distal end 152 of the object 118 engages the first side 126 of the plate 102, or at least a stratum of powder 116 on the first side 126, when the object 118 is moved to the contact position. After the proximal end 150 of the object 118 is formed, the proximal end 150 does not engage the plate 102 or the powder 116 during the remainder of the build process. The location of the platform 140 at the separated position may be based on a threshold lower limit distance or spacing between the distal end 152 of the object 118 and the first side 126 of the plate 102. For example, the threshold lower limit distance may be at least slightly greater than a distance from the first side 126 to a top of the spreader 110, which ensures that the spreader 110 can pass between the object 118 and the plate 102 while the object 118 is in the separated position.
The linear drive mechanism 142 may include any suitable electro-mechanical motorized actuator and associated mechanical linkage. The linear drive mechanism 142 in the illustrated embodiment is coupled to the ceiling 136 of the enclosure 130. For example, the linear drive mechanism 142 extends from the ceiling 136 to the platform 140, and the build support device 104 is disposed within the enclosure 130 of the heating appliance 112. Alternatively, the linear drive mechanism 142 may be mounted to the side walls 134 of the enclosure 130 or may be unconnected to the enclosure 130. In an example alternative embodiment, the linear drive mechanism 142 may be connected directly to the plate 102 or may be mounted on a support structure (other than the enclosure 130).
The linear drive mechanism 142 of the build support device 104 is operably connected to the control unit 108 via a wired or wireless communication pathway. The control unit 108 communicates electrical signals to the linear drive mechanism 142 to control the positioning of the object 118 relative to the plate 102 during the build process. It is understood that the location of the platform 140 relative to the plate 102 and the heating appliance 112 when the object 118 is in the contact position may vary during the build process as the object 118 increases in size. For example, the platform 140 is closer to the plate 102 to achieve the contact position early in the build process when the object 118 is relatively small than later in the build process when the object 118 is larger. Similarly, the location of the platform 140 relative to the plate 102 and the heating appliance 112 when in the separated position may also vary during the build process as the object 118 enlarges.
The energy beams output from the electromagnetic energy source 106 have a sufficient amount of energy to promote melting and/or fusing of the powder 116 onto the distal end 152 of the object 118. The electromagnetic energy source 106 may be or include a laser beam generator, an electron beam generator, or the like. For example, in an embodiment in which the electromagnetic energy source 106 is a laser beam generator, the electromagnetic energy source 106 generates and emits laser beams that represent the energy beams. The laser beam generator may be a fiber laser in a non-limiting example. In an embodiment in which the electromagnetic energy source 106 is an electron beam generator, the electromagnetic energy source 106 generates and emits electron beams that represent the energy beams. The electron beam generator optionally may be a single crystalline cathode, multi-beam device. The electromagnetic energy source 106 optionally may also include one or more lenses, collimators, mirrors, and/or the like for directing the energy beams towards different selected areas of the plate 102. The electromagnetic energy source 106 is operably connected to the control unit 108 via a wired or wireless communication pathway. The control unit 108 communicates electrical signals to the electromagnetic energy source 106 to control the timing and intensity of energy beams that are generated and emitted during the build process, as well as to guide and direct the locations at which the energy beams impinge upon the powder 116 that is dispersed on the plate 102.
The control unit 108 includes one or more processors 154 that are configured to operate based on programmed instructions. The control unit 108 may include additional features or components, such as a data storage device (e.g., memory), an input/output (I/O) device, and/or a wireless communication device. The memory may store programmed instructions (i.e., software) that is dictates the functioning of the one or more processors 154. For example, the memory may store a data file, such as a CAD file, associated with the object 118 that is being fabricated. The control unit (e.g., the one or more processors 154 thereof) may control the operations of the electromagnetic energy source 106 based on the instructions in the data file to produce the object 118 as a replica of a digital object in the data file. The control unit 108 may also control one or more of the build support device 104, the heating appliance 112, spreader 110, and/or the valve 120 on the powder reservoir 114 during the build process. In
Optionally, all or at least a subset of the components of the AM system 100 shown in
In the illustrated embodiment, the spreader 110 is elongated along the longitudinal axis 193. The spreader 110 may be a cylindrical roller, a blade (e.g., a recoater blade), or the like. The spreader 110 moves relative to the plate 102 parallel to the lateral axis 191 to disperse and distribute the powder 116 into the stratum 202. Optionally, the spreader 110 is coupled to rails 204 that provide a track for the spreader 110 to move parallel to the lateral axis 191. The rails 204 are fixed in place relative to the plate 102, and optionally may engage the plate 102. For example, the rails 204 may be mounted to the second side 128 of the plate 102. The spreader 110 is coupled to the rails 204 via mounting arms 206. The mounting arms 206 and/or the rails 204 may include a motorized actuator that controls movement of the spreader 110 and the mounting arms 206 relative to the rails 204 and the plate 102.
The illustration shown in
In the illustrated orientation, the build support device 104 lifts the object 118 above the plate 102, and the spreader 110 moves underneath the object 118 to disperse the powder 116 into the stratum 202 under the object 118. The stratum 202 is retained on the first (or top) side 126 of the plate 102 via gravitational force. The electromagnetic energy source 106 is disposed below the second (or bottom) side 128 of the plate 102. The plate 102 is disposed between the stratum 202 and the electromagnetic energy source 106, and the stratum 202 is disposed between the object 118 and the plate 102.
The one or more processors 154 of the control unit 108 (shown in
In one or more embodiments of the present disclosure, the object 118 is disposed within the enclosure 130 of the heating appliance 112 (shown in
Because the entire (or at least most of the) mass of the object 118 is heated to the designated temperature, the object 118 does not experience significant thermal gradients between different parts of the object 118. For example, all parts of the object 118 may be within a small temperature range, such as within 2° F., 5° F., 10° F., or the like, of each other during the manufacturing process. Because the temperature at the distal end 152 of the object 118 that is fused to the selected portion 310 of the stratum 202 is similar to (e.g., within the small temperature range of) the temperature at the proximal end 150 of the object 118, the object 118 does not experience internal residual stress and/or deformation during the manufacturing process attributable to thermal gradients. Due to methodology of the manufacturing process described herein and the relatively uniform heating of the object 118, the AM system 100 described herein is able to accurately and consistently produce metal-containing parts with reduced risk of cracks, deformations, and the like relative to known additive manufacturing systems.
After moving the object 118 away from the plate 102, the remaining portion 314 of the powder 116 in the stratum 202 optionally may be cleared from the plate 102. For example, the powder 116 may be swept, blown, sucked, or otherwise moved into a collection reservoir (not shown) for reuse or disposal of the powder 116. After removing the remaining portion 314 of the stratum 202, another stratum of powder can be deposited and distributed onto the first side 126 of the plate 102 to prepare for application of a successive layer of the object 118. Alternatively, the remaining portion 314 of the preceding stratum 202 may not be removed from the first side 126 of the plate 102 before depositing additional powder to form the subsequent stratum. For example, the new powder may mix with the remaining portion 314 to define the subsequent stratum.
At 504, an object 118 is heated within an enclosure 130 of a heating appliance 112. The heating appliance 112 may be an oven or a furnace. The object 118 within the enclosure 130 is an incomplete manufactured part or work piece that being formed via additive manufacturing. The object 118 is heated to raise the temperature of the object 118 above a temperature of the ambient surrounding environment. The object 118 within the enclosure 130 may be coupled to a build support device 104 that holds the object 118 between the build support device 104 and the plate 102.
At 506, the object 118 is moved towards the first side 126 of the plate 102 such that the object 118 makes contact with the stratum 202 of powder 116. For example, the object 118 may be moved by the build support device 104, which includes a linear drive mechanism 142. The object 118 optionally may remain within the enclosure 130 during the movement towards the plate 102 and while the object 118 engages the stratum 202.
At 508, one or more energy beams 304 are directed from one or more electromagnetic energy sources 106 towards the plate 102 and the stratum 202 of powder 116 thereon. The one or more electromagnetic energy sources 106 are disposed along an opposite side of the plate 102 from the stratum 202. The one or more energy beams 304 penetrate through the plate 102 and impinge upon the powder 116 in a selected portion 310 of the stratum 202 upon exiting the plate 102. The energy beams 304 melt and/or fuse the powder 116 in the selected portion 310, causing the melted powder 116 to adhere to a distal end 152 of the object 118 which forms a (new) layer 312 of the object 118. The melted powder 116 may adhere to the object 118 via surface tension (e.g., capillarity) and/or chemical bonding. The selected portion 310 may be based on a computer design model, and the energy beams 304 are directed to the selected portion 310 by controlling adjustable optics associated with the electromagnetic energy sources 106, such as lenses, mirrors, and the like.
In at least one embodiment, the AM system 100 is oriented such that the first side 126 of the plate 102 generally faces vertically upward, and the stratum 202 of powder 116 is retained on the first side 126 via gravitational force. The one or more electromagnetic energy sources 106 are disposed below a second or bottom side 128 of the plate 102, such that the plate is between the electromagnetic energy sources 106 and the powder 116.
At 510, the object 118 is moved away from the first side 126 of the plate 102, such that the object 118 is spaced apart from the powder 116 that remains in the stratum 202. The object 118 may be moved by controlling the build support device 104 to lift the object 118 off of (e.g., above) the remaining powder 116 in the stratum 202. The portion of the melted powder 116 that adhered to the object 118 to form the layer 312 remains on the object 118 and is separated from the stratum 202 when the object 118 is moved away from the plate 102. At 512, the remaining portion 314 of the powder 116 in the stratum 202 optionally may be removed from the plate 102 after the object 118 is moved away from the plate 102. For example, the removed powder may be discarded or collected for reuse. The removal of the remaining portion 314 is optional because an additional quantity of powder 116 may be added to the remaining portion 314 on the plate 102 to form a subsequent, second stratum 402 that is used to apply a subsequent layer onto the object 118.
At 514, a determination is made whether or not the object 118 that is being manufactured is complete. The determination may be resolved with reference to programmed instructions, such as a computer design model, associated with the object 118. If the object 118 is not complete after the addition of the layer 312, then flow of the method 500 returns to 502 to apply a subsequent layer onto the layer 312 of the object 118. For example, upon returning to 502, an additional quantity of powder 116 is distributed onto the first side 126 of the plate 102 to form a second stratum 402. The powder 116 in a second stratum 402 may be the same type of powder or a different type of powder than the powder 116 in the first stratum 202. If, on the other hand, it is determined that the object 118 is complete and requires no additional layers, then the method 500 may end. Optionally, the method 500 may start again to produce another object that is the same as or different than the preceding object 118.
While various spatial and directional terms, such as top, bottom, lower, mid, lateral, horizontal, vertical, front and the like may be used to describe embodiments of the present disclosure, it is understood that such terms are merely used with respect to the orientations shown in the drawings. The orientations may be inverted, rotated, or otherwise changed, such that an upper portion is a lower portion, and vice versa, horizontal becomes vertical, and the like.
The diagrams of embodiments herein may illustrate one or more control or processing units, such as the control unit 108 shown in
As used herein, the term “control unit,” or the like may include any processor- based or microprocessor-based system including systems using microcontrollers, reduced instruction set computers (RISC), application specific integrated circuits (ASICs), logic circuits, and any other circuit or processor including hardware, software, or a combination thereof capable of executing the functions described herein. Such are exemplary only, and are thus not intended to limit in any way the definition and/or meaning of such terms. The control unit 108 shown in
As used herein, a structure, limitation, or element that is “configured to” perform a task or operation is particularly structurally formed, constructed, or adapted in a manner corresponding to the task or operation. For purposes of clarity and the avoidance of doubt, an object that is merely capable of being modified to perform the task or operation is not “configured to” perform the task or operation as used herein.
It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the various embodiments of the disclosure without departing from their scope. While the dimensions and types of materials described herein are intended to define the parameters of the various embodiments of the disclosure, the embodiments are by no means limiting and are example embodiments. Many other embodiments will be apparent to those of ordinary skill in the art upon reviewing the above description. The scope of the various embodiments of the disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112(f), unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.
This written description uses examples to disclose the various embodiments of the disclosure, including the best mode, and also to enable any person skilled in the art to practice the various embodiments of the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the various embodiments of the disclosure is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if the examples have structural elements that do not differ from the literal language of the claims, or if the examples include equivalent structural elements with insubstantial differences from the literal language of the claims.