Apparatus and method for managing temperature and stress in parts during additive manufacturing

Abstract

To provide a method of additively manufacturing a workpiece, which reduces cracking of the three-dimensional object due to internal residual stresses and distortions that occur during heating and cooling cycles involved in the additive manufacturing process.SOLUTION: A method of additively manufacturing a workpiece includes: depositing and melting a material on a build plate by translating a deposition head of an additive manufacturing apparatus over the build plate to form a layer of deposited material; and heating the deposited material with an oven after the layer is deposited on the build plate, wherein the oven comprises a furnace body and an oven lid movable with the deposition head and disposable on the furnace body to enclose a heated build chamber of the oven.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This specification relates generally to additive manufacturing, and more particularly to managing temperature and stress in additively manufactured objects during the building process. [Background technology]

[0002] Additive manufacturing is a set of emerging technologies that produce three-dimensional objects directly from digital models through additive processes, typically by depositing material layer by layer and bonding successive layers in place. In some additive manufacturing techniques, a heat source is typically applied to layers of build material to selectively melt the layers of build material so that the build material ultimately solidifies in a desired configuration as a layer of the three-dimensional object.

[0003] The embodiments set forth in the drawings are illustrative and exemplary in nature and are not intended to limit the subject matter defined by the claims. The following detailed description of exemplary embodiments can be understood when read in conjunction with the following drawings, in which like structure is indicated with like reference numerals and in which: [Brief explanation of the drawings]

[0004] [Figure 1] FIG. 1 is a schematic diagram of an additive manufacturing apparatus according to one or more embodiments described herein. [Figure 2] 2 is a schematic diagram of the additive manufacturing apparatus shown in FIG. 1 with the deposition head and oven lid of the additive manufacturing apparatus in different positions, according to one or more embodiments described herein. [Figure 3] FIG. 3 is a flowchart diagram illustrating a method for additively manufacturing a workpiece while managing residual stresses in the workpiece according to one or more embodiments described herein. [Figure 4] FIG. 4 is a schematic diagram of an additive manufacturing apparatus incorporating an autoclave, according to one or more embodiments described herein. [Figure 5]FIG. 5 is a schematic diagram of an additive manufacturing apparatus incorporating multiple autoclaves, according to one or more embodiments described herein. [Figure 6] FIG. 6 is a schematic diagram illustrating a top view of another additive manufacturing apparatus having an array of autoclaves, according to one or more embodiments described herein. DETAILED DESCRIPTION OF THE INVENTION

[0005] During the heating and cooling cycles involved in additive manufacturing processes, stresses can accumulate in the three-dimensional object being built. For example, if the build material is a metal, the build material may shrink as it melts and then solidifies. This shrinkage can generate internal residual stresses and strains. Such internal residual stresses and strains can induce cracks in the three-dimensional object. This is particularly likely when the three-dimensional object being built is relatively large or is built from a material with low ductility (e.g., an alloy). Therefore, there is a need for a method to manage such internal residual stresses and strains during additive manufacturing processes.

[0006]

[0010] An embodiment of a method for heating a workpiece formed by an additive manufacturing apparatus during the process of building the workpiece will now be described in detail. In the embodiment, the additive manufacturing apparatus includes a build plate on which the workpiece is built and a deposition head translatable relative to the build plate. In the embodiment, the deposition head is configured to direct both an energy beam from an energy beam source and deposition material to a common location, whereby the energy beam from the energy beam source melts and fuses the deposition material as the deposition head translates over the build plate to deposit layers of the deposition material on the build plate to form a portion of the workpiece. The additive manufacturing apparatus includes an oven including an oven lid and a furnace body. The furnace body defines a heated build chamber in which the build plate is disposed, and the oven lid moves in conjunction with the deposition head as the deposition head translates relative to the build plate and the furnace body. The oven lid also includes an opening through which the deposition material and the energy beam are provided from the deposition head to the heated build chamber. The oven lid is in physical contact with (e.g., slidably connected to) or positioned proximate to the furnace body such that the heated build chamber is substantially sealed regardless of the position of the deposition head. Such an oven configuration facilitates heat treating the workpiece at any point during the build process, thereby enabling the removal of residual stresses in the workpiece and therefore enabling the production of larger workpieces or workpieces comprised of less ductile materials than would be possible using conventional additive manufacturing equipment. In an embodiment, the furnace body is configured as an autoclave, and the cavity is pressurized when the autoclave lid is placed on the furnace body and seals the cavity therein.

[0007] As used herein, the term "about" means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and / or larger or smaller, as appropriate, to reflect tolerances, conversion rates, rounding, measurement error, and the like, as well as other factors known to those of ordinary skill in the art. When the term "about" is used to describe a numerical value or an endpoint of a range, the specific value or endpoint referenced is included. Regardless of whether a numerical value or range endpoint herein is described as "about," two embodiments are described: one embodiment modified by "about" and one embodiment not modified by "about." Furthermore, it will be understood that each endpoint of a range is significant both in relation to the other endpoint and independently of the other endpoint.

[0008] Directional terms used herein (e.g., up, down, right, left, front, back, top, bottom) are used solely with reference to the depicted figures and are not intended to imply absolute directions.

[0009] Unless expressly stated otherwise, no method described herein is intended to be construed in any way as requiring that its steps be performed in a particular order, nor is any method intended to require a particular orientation of any apparatus. Thus, where a method claim does not actually recite the order in which its steps are to be followed, or any apparatus claim does not actually recite an order or orientation for individual components, or where the claim or specification does not specifically state that the steps are to be limited to a particular order, or where no particular order or orientation for the apparatus components is recited, no order or orientation is intended to be inferred in any way. This also applies to any implicit matters that may be the basis of interpretation, including logical matters regarding the arrangement of steps, operational flow, component order, or component orientation, the plain meaning derived from grammatical construction or punctuation, or the number or type of embodiments described herein.

[0010] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a component preceded by "a" includes aspects having two or more of such components unless the context clearly dictates otherwise.

[0011] As used herein, the term "additive manufacturing (AM)" encompasses a variety of manufacturing and prototyping technologies known by various names, including freeform manufacturing, 3D printing, rapid prototyping / tooling, etc. AM technologies can produce complex parts from a variety of materials. Generally, freestanding objects can be produced from computer-aided design (CAD) models. Certain embodiments described in this disclosure may relate to directed energy deposition AM technologies, such as Laser Freeform Manufacturing Technology (LFMT), Selective Laser Melting (SLM), Powder-Bed Electron Beam Melting (EBM), Electron Beam Free Form Fabrication (EBF3), and Laser Engineered Net Shape (LENS). While certain implementations of the present disclosure are described with reference to particular AM technologies, such examples should not be considered limiting.

[0012] The term "substantially" may be utilized herein to describe the inherent degree of uncertainty that may result from any quantitative comparison, value, measurement, or other representation. This term is also used herein to describe the degree to which a quantitative representation may vary from the stated standard without resulting in a change in the basic functionality of the subject matter at issue.

[0013] 1 and 2, an additive manufacturing apparatus 100 is shown schematically. The additive manufacturing apparatus 100 is configured to build a workpiece 102 on a build plate 104. A deposition head 112 is attached to support structures, shown as support arms 108 and 110. The deposition head 112 and the build plate 104 are generally movable relative to one another. For example, the support arm 110 may include a movable structure (e.g., a translation stage) and a motor or other actuation device (not shown) coupled to the deposition head 112 such that the deposition head 112 is movable in a plane parallel to the build plate 104 (e.g., the x-y plane). The deposition head 112 may have a first range of motion 152 in the x-direction and a second range of motion (not shown) in the y-direction (e.g., the center of the deposition head 112 may be movable between opposite ends of the first range of motion 152). In an embodiment, the build plate 104 is rotatable about an axis extending in the z-direction. For example, the build plate 104 may be mounted on a base plate 105 and rotate relative to the base plate 105. For example, the base plate 105 may include a motor to rotate the build plate 104, or the build plate 104 may include a motor to rotate the build plate 104 on the base plate 105, or rotating the base plate 105 may rotate the build plate 104 mounted thereon. Alternatively or additionally, embodiments may include an actuator 163 to translate the build plate 104 vertically in the z-direction and / or to rotate the build plate 104. If utilized, the actuator 163 may also rotate the base plate 105 and the build plate 104 thereon. However, the base plate 105 and / or the actuator 163 are optional.

[0014] The deposition head 112 includes an energy beam source 120 configured to emit an energy beam 122, and material sources 116 and 118. While the energy beam source 120 and the material sources 116 and 118 are shown as being disposed within the deposition head 112, it should be understood that all or a portion of the energy beam source 120 and the material sources 116 and 118 may be disposed external to the deposition head 112. For example, in an embodiment, the material sources 116 and 118 include a powder delivery system disposed external to the deposition head 112, which may include a pressurized gas source configured to convey powder (e.g., a metal powder or an alloy powder) to the deposition head 112. In such an implementation, the illustrated material sources 116 and 118 may include powder nozzles extending through material nozzles 114 attached to the deposition head 112. The material nozzles may be configured to provide material feeds 124 and 126 (e.g., in the form of powder jets) to the build plate 104. In other embodiments, the material sources 116 and 118 may include material spools and material feeders (not shown) configured to provide material feeds 124 and 126 (e.g., as metal wire) to the build plate 104 for incorporation into the workpiece 102. Such material spools and material feeders may be attached to the exterior surface 168 of the deposition head 112. While two material sources 116 and 118 are shown, it should be understood that any number of material sources may be included consistent with this disclosure. The material sources 116, 118 may include any number of materials or mixtures of materials, including, but not limited to, titanium alloys (e.g., Ti-6-4 or Ti-6-2-4-2), precipitation hardenable nickel superalloys (INCO-718 or RENE-41), precipitation hardenable steels (e.g., 17-4-PH or 15-5-PH), etc.

[0015] The energy beam source 120 can take a variety of forms depending on the implementation. For example, in embodiments, the energy beam source 120 may include a laser beam source and optics configured to direct a laser beam (i.e., the energy beam 122 is a laser beam) having a desired energy density (e.g., focus) toward the build surface on the build plate 104. The energy beam source 120 may be located external to the deposition head 112, or the illustrated energy beam source 120 located within the deposition head 112 may include a radiation direction device (e.g., a reflector). In embodiments, the energy beam source 120 can take a variety of other forms (e.g., an electric arc, a plasma source, and an electron beam source). For example, the energy beam source 120 may include an electron emitter connected to a power source and at least one focusing coil configured to direct an electron beam (i.e., the energy beam 122 is an electron beam) toward the build surface on the build plate 104. In embodiments in which an electron beam is used to fuse the deposition material, the build chamber 128 (eg, surrounding the deposition head 112 and build plate 104) may be in a vacuum or reduced oxygen environment.

[0016] Material feeds 124 and 126 are provided in the path of the energy beam 122, which heats the deposition material. A melt pool of deposition material may be formed on the build surface on the build plate 104. For example, the melt pool may be formed directly on the build plate 104 (e.g., when the layer of deposition material to be deposited is an initial layer of the workpiece 102) or may be formed on a layer of the workpiece 102 that was previously deposited on the workpiece 102 via the additive manufacturing apparatus 100. By controlled movement of the deposition head 112 relative to the build plate 104, the layer of deposition material may be deposited as a melt pool on the build plate 104.

[0017] It is contemplated that, depending on the size of the workpiece 102, the melt pool may cool after depositing a layer of deposition material before depositing another layer of deposition material. For example, this may be particularly true for large-format parts, although the disclosure is not so limited. As the melt pool cools, the deposited material may shrink, creating residual stresses in the workpiece 102. Such residual stresses may ultimately cause cracking or warping of the workpiece 102. Without a way to control such stresses caused by thermal fluctuations in the deposited material, the additive manufacturing apparatus 100 may be unable to build certain types of workpieces 102. If the material feeds 124 and 126 are less flexible materials, such as alloys, the additive manufacturing apparatus 100 may be unable to fabricate workpieces 102 of such materials, especially if such workpieces 102 have characteristics that promote stress accumulation. For example, alloys such as Ti-6-2-4-2 are difficult to handle. Due to the low ductility of these types of materials (compared to alloys such as cobalt-chromium), significant strain can accumulate as successive layers of them are built and then begin to cool, and because such materials have limited ductility, strain accumulates until the strength of the material is eventually exceeded and a portion is sheared free. Additionally, because thicker workpieces 102 typically include more layers of deposited material and therefore may contain more accumulated residual stresses, such residual stress buildup can also prevent the additive manufacturing apparatus 100 from manufacturing workpieces 102 having relatively large geometries.

[0018] With the above in mind, the additive manufacturing apparatus 100 includes an oven 130. The oven 130 includes a furnace body 132 that defines a cavity 134 in which the build plate 104 is disposed. The furnace body 132 includes sidewalls 138 and a floor 140 that define the cavity 134 with an open top. An oven lid 136 may be provided on the furnace body 132 to at least partially enclose the open top of the cavity 134, thereby further insulating the cavity 134. As described below, the furnace body 132 and oven lid 136 substantially enclose the cavity 134 such that the cavity 134 is a heated build chamber that encompasses the vicinity of the build plate 104 and the workpiece 102. In other words, the furnace body 132 and oven lid 136 define a subvolume within the additive manufacturing apparatus 100 that can be selectively heated to a temperature different from the temperature of the ambient environment of the additive manufacturing apparatus 100. As mentioned above, the oven lid 136 is large enough to cover the cavity 134 throughout its range of motion.

[0019] The furnace body 132 and the oven lid 136 can take a variety of different forms depending on the implementation. In embodiments, the furnace body 132 and the oven lid 136 can have corresponding geometric shapes. The example shown in FIG. 1 depicts a cavity 134 having a substantially square cross-section. In such embodiments, the furnace body 132 can be substantially box-shaped, while the cavity 134 can have a substantially flat sheet-like cross-section. Other implementations are contemplated in which the furnace body 132, the cavity 134, and the oven lid 136 have a variety of different shapes. For example, in embodiments, the furnace body 132 can be substantially round (e.g., thereby defining a cavity 134 having a substantially cylindrical shape), and the oven lid 136 can have a corresponding geometric shape. In the illustrated embodiment, the oven lid 136 is arranged parallel to the build plate 104, but in other embodiments, the oven lid 136 may not be parallel to the build plate 104 (e.g., the oven lid 136 may extend at an angle to the xy plane or may be curved).

[0020] The cavity 134 defined by the furnace body 132 and enclosed via the oven lid 136 may be of various sizes. For example, in embodiments, the furnace body 132 is designed such that the cavity 134 is large enough to fit the build plate 104 and deep enough (e.g., in the z direction of the illustrated coordinate system) to accommodate a workpiece 102 to be built via the additive manufacturing apparatus 100 having a desired thickness. Such an embodiment is beneficial in that the volume (e.g., volume of gas, vacuum, etc.) that needs to be heated via the oven 130 is minimized, such that heating times are reduced and higher heating efficiency is achieved. However, alternative embodiments are envisioned in which the furnace body 132 and / or cavity 134 are larger relative to the build plate 104 (e.g., including a larger gap between the build plate 104 and the sidewalls 138 and floor 140 of the furnace body 132). Such embodiments including cavities 134 with such large dimensions may be beneficial in that they are less susceptible to damage from waste material (e.g., powder from material feeds 124 and 126 that is not fused to workpiece 102).

[0021] In an embodiment, the furnace body 132 is stationary within the additive manufacturing apparatus 100. As shown, the furnace body 132 is attached to an oven support structure 142 that is disposed on the base 106 of the additive manufacturing apparatus 100. The oven support structure 142 may include an opening such that a cavity 144 is defined between the floor 140 of the furnace body 132 and the base 106. In an embodiment, the oven support structure 142 includes a movable platform such that the furnace body 132 is moveable within the additive manufacturing apparatus 100. In an embodiment, an alternative oven support may be attached to the support arm 110 (e.g., the furnace body 132 may be attached to a sidewall of the additive manufacturing apparatus 100) such that the furnace body 132 is held in spaced relation to the base 106. Such space between the base 106 and the floor 140 (e.g., in the form of a cavity 144) beneficially provides space for additional components (e.g., a build plate support 162 and an excess bin 166) beneath the furnace body 132. In an embodiment, the furnace body 132 is positioned directly on the base 106.

[0022] The oven 130 includes heating elements 146 that extend into the cavity 134 through openings 147 in the sidewalls 138 of the furnace body 132. Although the oven 130 is shown including only two of the heating elements 146 extending through the sidewalls 138 of the furnace body 132, the oven 130 may include any number of heating elements 146 positioned at various locations within the additive manufacturing apparatus 100. For example, certain embodiments may include a heating element 146 positioned within or extending through the oven lid 136. Alternatively or additionally, the heating element 146 may extend through the floor 140 of the furnace body 132. In embodiments, the heating element 146 may be embedded in the sidewalls 138 and / or the oven lid 136 and / or the floor 140. In some embodiments, the build plate 104 may include a build base (not shown) that is positioned within the cavity 134. Such an embodiment may include a heating element 146 extending through the build base to provide heating to the bottom surface of the workpiece 102, which may beneficially prevent a thermal gradient between the bottom surface of the workpiece 102 and an outer portion of the workpiece 102.

[0023] In an embodiment, the heating elements 146 are induction coils or electrical resistance heating elements, although other forms of heaters may be used. In such embodiments, each of the heating elements 146 may be connected to a power supply (not shown) controlled via a controller 148. As described below, the controller 148 may be responsive to various inputs (e.g., input from a user of the additive manufacturing apparatus 100, input from an ultrasonic stress sensor (not shown) configured to measure stress in the workpiece 102) to selectively control the power supplies to heat the workpiece 102 at various points during the process of building the workpiece 102 with the additive manufacturing apparatus 100. For example, the oven 130 may be controlled to heat the cavity 134 to elevated temperatures to heat-treat the workpiece 102 between different layers of deposition material deposited by the deposition head 112 onto the build plate 104, thereby removing residual stresses in the workpiece 102 as it is built.

[0024] The oven lid 136 is disposed between the deposition head 112 and the furnace body 132 and includes an upper surface 150 and a lower surface 151. The oven lid 136 includes an opening 154 to provide clearance for the energy beam 122 and material feeds 124 and 126 to reach the build plate 104. In the illustrated embodiment, the opening 154 is centrally located within the oven lid 136 and extends through the oven lid 136 from the upper surface 150 to the lower surface 151. The central location of the opening 154 within the oven lid 136 facilitates consistent overlap between the oven lid 136 and the cavity 134, regardless of the position of the oven lid 136. However, alternative embodiments are contemplated in which the opening 154 is not centrally located within the oven lid 136. In embodiments, the size of the opening 154 is based on the distance between the material nozzle 114 and the oven lid 136 because, for example, the material feeds 124 and 126 may extend at an angle between the material nozzle 114 and the build plate 104, and the opening 154 may be sized to provide clearance for the material feeds 124 and 126. The opening 154 can have any shape and depth profile, depending on the implementation. In embodiments, the opening 154 has the smallest allowable size while still allowing the material feed and directed energy to pass through the opening. In other embodiments, the oven lid 136 has a pair of openings, a first opening of the pair for passing the material feed and a second opening of the pair for passing the directed energy.

[0025] As described herein, the deposition head 112 may be translatable in the xy plane to deposit layers of deposition material onto the build surface on the build plate 104. Such movement of the deposition head 112 may cause misalignment between the opening 154 and the deposition head 112 such that the top surface 150 of the oven lid 136 blocks the energy beam 122 and the material feeds 124 and 126 from reaching the build plate 104. In embodiments, the oven lid 136 moves in conjunction with the deposition head 112 as the deposition head 112 translates to facilitate continuous access to the build plate 104 by the energy beam 122 and the material feeds 124 and 126. Stated another way, the oven lid 136 is movable with the deposition head 112, and the oven lid 136 and deposition head 112 are movable together. The mobility of the oven lid 136 facilitates minimizing the size of the opening 154 while still providing sufficient clearance for the energy beam 122 and the material feeds 124 and 126. Minimizing the opening 154 improves the performance of the oven 130, for example, by reducing the convection of heat supplied by the heating element 146 to the environment outside the oven 130.

[0026] Translation of the oven lid 136 and deposition head 112 can be achieved in a variety of ways. As illustrated in FIG. 1 , the oven lid 136 may be attached to an exterior surface 168 of the deposition head 112 via an oven mounting member 158 attached to a top surface 150 of the oven lid 136. In an embodiment, the oven lid 136 is suspended from the deposition head 112 via mechanical fasteners, such as screws. In an embodiment, the oven lid 136 is coupled to the deposition head 112 in a manner that allows relative vertical movement of the oven lid 136 with respect to the deposition head 112. For example, if the oven lid 136 is slidable on the furnace body 132, the deposition head 112 can include alignment features (such as vertically oriented pins) that engage with corresponding holes in the oven lid 136 (or vice versa), thereby allowing the oven lid 136 to move vertically relative to the deposition head 112 and obstruct the deposition head 112. The alignment feature can physically interconnect the deposition head 112 and the oven lid 136 while allowing limited relative vertical translation of the oven lid 136 relative to the deposition head 112, such that the deposition head 112 can translate vertically a sufficient amount before ultimately lifting the oven lid 136. For example, the alignment feature can have a flange portion attached to the deposition head 112 that interacts with and captures a ridge in a corresponding hole in the oven lid 136. In this manner, a single motor (e.g., coupled to either the oven lid 136 or the deposition head 112) can be utilized to translate the combination of the oven lid 136 and deposition head 112 relative to the build plate 104. However, alternative embodiments are also envisioned in which the oven lid 136 is not attached to the deposition head 112, and the additive manufacturing apparatus 100 includes a separate translation device configured to move the oven lid 136 (e.g., the controller 148 may provide separate control signals to provide translation of the oven lid 136 and the deposition head 112).

[0027] Although only a single oven mounting member 158 on one side of the deposition head 112 is shown, the oven lid 136 can be attached to the deposition head 112 using any number of mounting members in any configuration. For example, in one embodiment, the oven mounting member 158 has a shape that corresponds to the deposition head 112 (e.g., a substantially cylindrical shape) and can contact the entire circumference of the deposition head's outer surface 168. In other embodiments, the oven lid 136 can be attached directly to the deposition head 112. For example, the opening 154 can be attached directly to the outer surface 168 such that at least a portion of the deposition head 112 is disposed within the opening 154. In other examples, the oven lid 136 can be attached to the support arm 110 that supports the deposition head 112. In other examples, the deposition head 112 and the oven lid 136 are not attached to each other and, instead, can move together via independent movement systems. For example, the oven lid 136 may be movable via a motor configured to move the oven lid 136 based on the movement of the deposition head 112, such that the oven lid 136 follows the movement of the deposition head 112 while covering the cavity 134.

[0028] As described herein, in some embodiments, the furnace body 132 may be secured to the base 106 such that the furnace body 132 is stationary. Providing the furnace body 132 in a stationary state advantageously simplifies the configuration of the additive manufacturing apparatus by simplifying connections between components (e.g., the heating element 146 and a power source external to the oven 130). In these embodiments, the oven lid 136 is configured to be movable relative to the (stationary) furnace body 132 to facilitate movement of the oven lid 136 in conjunction with the deposition head 112. To facilitate movement of the oven lid 136, in some examples, the oven lid 136 need not be in physical contact with the furnace body 132. In such embodiments, the underside 151 of the oven lid 136 is spaced less than a predetermined distance from the edge of the sidewall 138 of the furnace body. In embodiments, the oven lid 136 can be spaced as short a distance as possible from the edge of the sidewall 138 without interference therebetween. In an embodiment, the oven lid 136 is spaced approximately 0.1 inches from the edge of the sidewall 138. As shown in FIGS. 1-2 , in other embodiments, the lower surface 151 is in physical contact with the upper edge of the sidewall 138, but the oven lid 136 is still movable relative to the furnace body 132 (e.g., the oven lid 136 is slidable relative to the furnace body 132). In an embodiment, the upper edge of the sidewall 138 (or the lower surface of the oven lid 136) may be provided with rollers or a low-friction material.

[0029] The deposition head 112 is positioned in FIG. 1 so that the oven lid 136 is centered relative to the furnace body 132 (e.g., at the center of the x-direction range of motion 152). In this configuration, the oven lid 136 includes an overhang 160 that extends beyond the sidewall 138 of the furnace body 132. The overhang 160 has a length (e.g., in both the x and y directions) that corresponds to the range of motion of the deposition head 112 (e.g., the x-direction range of motion 152 and the y-direction range of motion (not shown)). For example, in an embodiment, the overhang 160 has a length in both the x and y directions (e.g., on both sides of the oven 130) that corresponds to half of the range of motion. In this way, even when the deposition head 112 moves to the end of the range of motion 152, as shown in FIG. 2, the cavity 134 remains covered by the oven lid 136, maintaining efficient heating. The overhang 160 may be shorter or longer in other embodiments. Some embodiments may not include the overhang portion 160. As described above, the oven lid 136 is large enough to cover the cavity 134 throughout the entire range of motion 152. In this manner, the cavity 134 is surrounded by the furnace body 132 and the oven lid 136, except for the opening 154 that provides clearance for the energy beam 122 and the material feeds 124 and 126, and / or, as described above, except for areas where the underside 151 of the oven lid 136 may not contact the sidewalls 138 of the furnace body 132. Regardless of the presence of the opening 154 and whether the oven lid 136 contacts the sidewalls 138 of the furnace body 132, the furnace body 132 and the oven lid 136 are said to "substantially surround" or "enclose" the cavity 134.

[0030] In the illustrated example, the build plate 104 and base plate 105 are supported within the furnace body 132 by build plate supports 162 disposed on the base 106. The build plate supports 162 extend through the floor 140 of the furnace body 132. In some embodiments, the build plate supports 162 are adjustable relative to the furnace body 132, allowing the build plate 104 to move in the z-direction between layers of deposition material being deposited on the build plate 104. For example, the build plate supports 162 may be extendable in the z-direction (e.g., as an articulated arm or an extendable arm) and may include an actuator 163 communicatively coupled to the controller 148. Alternatively or additionally, the build plate supports 162 can also support the furnace body 132 and allow movement in the z-direction. In embodiments where the deposition head 112 is maintained in a (constant) vertical position and the build plate 104 is moved vertically relative to the deposition head 112, the build begins with the build plate support 162 positioning and holding the build plate 104 adjacent to the underside of the oven lid 136. As the build progresses and the workpiece 102 grows vertically, the build plate support 162 lowers the build plate 104 so that the top layer of the workpiece 102 is maintained a constant vertical distance from the deposition head 112.

[0031] After a layer of deposition material is deposited on the build plate 104 by translational movement of the deposition head 112, the controller 148 can command the actuator 163 to actuate the build plate support 162, thereby moving the build plate 104 a predetermined distance in the negative z-direction based on the desired thickness of the next layer of deposition material to be deposited. In an embodiment, a seal can be disposed between the build plate support 162 and the floor 140 of the furnace body 132 to promote heating efficiency.

[0032] A material conduit 164 is shown extending through the base plate 105, the build plate 104, and a portion of the floor 140 of the furnace body 132. The material conduit 164 may be located on an outer portion of the build plate 104 that does not overlap with the range of motion 152 of the deposition head 112. In other words, the material conduit 164 may be located in an area of the build plate 104 that does not support the workpiece 102. During the build process of the workpiece 102, excess material from the material feeds 124 and 126 may not be melted by the energy beam 122 and may accumulate on the build plate 104. The material conduit 164 provides a path for such excess material to be removed from the cavity 134 so that it is not inadvertently incorporated into the workpiece 102. The material conduit 164 supplies excess material to an excess container 166 located on the base 106. The excess container 166 can be emptied between or during builds, for example, to maintain a clean operating environment. While only one material conduit 164 is shown, it should be understood that any number of material conduits 164 may be incorporated into an additive manufacturing apparatus 100 consistent with the present disclosure. In an embodiment, a scraper may be connected within the cavity 134, for example, to the sidewall 138, and may be movable to position the scraper to scrape or brush excess material into the material conduit 164. In an embodiment, a portion of the build surface of the build plate 104 on which no workpiece 102 is disposed may have a funnel-shaped surface that funnels excess material (e.g., powder) into the material conduit 164. In other embodiments where the material conduit 164 does not extend into the build plate 104, a portion of the build plate 104 can be tilted away from the workpiece 102, thereby allowing excess material to spill from the build plate 104 onto the floor 140, which has a funnel shape that leads to the material conduit 164, thereby allowing the excess material to be removed.

[0033] Referring now to Figure 3, a method 300 for additively manufacturing a workpiece is shown in accordance with one or more embodiments described herein. Method 300 may be performed by the additive manufacturing apparatus 100 described with respect to Figures 1 and 2 herein. For example, controller 148 may control deposition head 112, oven 130, and build plate support 162 to perform method 300 and build workpiece 102. It should be understood that method 300 may also be performed by other additive manufacturing apparatuses.

[0034] In step 302, a layer of deposition material is deposited and melted onto the build plate 104 by translating the deposition head 112 of the additive manufacturing apparatus 100 over the build plate 104. For example, the controller 148 may receive a representation of the workpiece 102 and divide the workpiece 102 into multiple layers for deposition by the additive manufacturing apparatus 100. The controller 148 may control the movement of the deposition head 112 in the x and y directions to deposit the deposition material in a desired pattern corresponding to one of the multiple layers of the workpiece 102. As described herein, the deposition head 112 includes material sources 116 and 118 and an energy beam source 120. Material sources 116 and 118 provide material feeds 124 and 126 (e.g., as wires, powder jets, etc.) to build plate 104, which interact with energy beam 122 from energy beam source 120 such that the deposited material melts and forms a melt pool on build plate 104. The melt pool may be fused to build plate 104 upon cooling. As noted above, the deposited material may include a variety of different materials, but in an example where the deposited material is titanium 6-4 ("Ti 6-4"), the Ti 6-4 is deposited with oven 130 heated to approximately 500°C (500°C).

[0035] In step 304, it is determined that the residual stress in the workpiece 102 is greater than a predetermined threshold. Step 304 is optional. In embodiments, such a determination may be made by a user of the additive manufacturing system 100 (e.g., by observing the workpiece 102 during build). The determination may also be made via the controller 148. For example, in embodiments, the controller 148 may have multiple instruction sets (stored in the controller 148) that, for example, identify stress buildup based on the deposition material contained in the material feeds 124 and 126. Such instruction sets may include a determination based on a previous build that a threshold amount of residual stress is reached after a predetermined number of layers of deposition material have been deposited and melted on the build plate 104. In embodiments, the controller 148 automatically determines that the residual stress in the workpiece 102 is greater than a predetermined threshold. As such, step 302 may be repeated any number of times before step 304. In an embodiment, the additive manufacturing apparatus 100 includes at least one detector 149 communicatively coupled to the controller 148 and configured to inspect the workpiece 102 (e.g., disposed within the cavity 134 defined by the furnace body 132 and disposed on the build plate 104). The detector 149 may include, for example, a stress sensor (e.g., an ultrasonic transducer, a piezoelectric transducer, etc.) and / or a camera configured to generate a detection signal (e.g., an image, a stress measurement) that is analyzed by the controller 148 to determine whether the residual stress exceeds a predetermined threshold. The predetermined threshold may be calculated by empirical data of identical or similar workpieces or by prior analysis based on computer modeling.

[0036] If utilized, the detector 149 may be provided to enable measurements of the workpiece 102 to be taken from within the cavity 134. In the illustrated example, the detector 149 is shown extending through the sidewall 138, but the detector 149 may be provided in a different manner. For example, the detector 149 may be provided on the deposition head 112 and / or on the underside 151, or may otherwise be suspended within the cavity 134. In other embodiments, measuring the residual stresses in the workpiece 102 is achieved via a distortion prediction system that generates material property information for predicting distortion of the workpiece 102 during sintering. In such embodiments, the distortion prediction system may include a processor and a material characterization module 510 having a plurality of test workpiece models that may be input and stored (e.g., as part models) within the additive manufacturing system 100. The test workpiece models have known material properties (i.e., residual stresses) based on testing of coupons formed by the additive manufacturing system 100 that are intended to simulate the workpiece 102. In this manner, the material characterization module contains material property information for simulating distortion and residual stresses in workpieces 102 built using a number of different material configurations (e.g., granular materials, binder solutions, scan speeds, curing parameters, etc.) Thus, a determination of when sufficient stress has accumulated to perform a stress relief cycle may be made using detector 149 and / or via predictive stress analysis performed using a distortion prediction system.

[0037] In step 306, in response to the determination made in step 304, the workpiece 102 is heated by the oven 130 to a first elevated temperature above ambient temperature. As described herein, the oven 130 includes a furnace body 132 and an oven lid 136 that enclose a cavity 134 defined by a sidewall 138 and a floor 140 of the furnace body 132. The oven lid 136 moves in conjunction with the deposition head 112 as the deposition head 112 moves over the build plate 104 to deposit layers of deposition material. The oven lid 136 (e.g., via an opening 154) provides a path for the material feeds 124 and 126 and the energy beam 122 to reach the build plate 104 and moves parallel to the movement of the deposition head 112. In this manner, the cavity 134 defines a heated build chamber that is substantially smaller than the volume of the additive manufacturing apparatus 100 without interrupting the operation of the deposition head 112. Therefore, the workpiece 102 is heated more efficiently, reducing the heating time and energy consumption of the oven 130.

[0038] The oven 130 includes at least one heating element 146 configured to heat the workpiece 102 and / or the cavity 134. In an embodiment, the controller 148 provides a control signal to the heating element 146 (or a power source connected thereto) to increase the temperature within the cavity 134 to a first elevated temperature. In an embodiment, the additive manufacturing apparatus 100 includes a temperature sensor (not shown) configured to monitor the temperature within the cavity 134 and provides feedback control of the heating element 146 via the controller 148. For example, in an embodiment, power is supplied to the at least one heating element 146 to heat the cavity 134 at a first predetermined heating rate until the first elevated temperature is reached. Once the first elevated temperature is reached, the controller 148 can control the at least one heating element 146 to maintain the temperature within the cavity 134 at the first elevated temperature for a first predetermined period of time to remove residual stresses within the workpiece 102. In the above example using Ti6-4 as the deposition material, the oven 130 is further heated in step 306 to a first elevated temperature of about 700°C.

[0039] Step 308 is a decision block. If the layer deposited on the build plate 104 in step 304 is not the final layer of the workpiece 102, the method 300 may return to step 302 to deposit another layer of deposition material on the build plate 104. In embodiments, deposition of additional layers on the build plate 104 may occur while the cavity 134 is being heated via the at least one heating element 146 (e.g., while the cavity 134 is at a first elevated temperature). In embodiments, deposition of additional layers on the build plate 104 may occur after the temperature within the cavity 134 has cooled to an ambient temperature of the environment of the additive manufacturing apparatus 100. In embodiments, the at least one heating element 146 may heat the cavity 134 to any temperature (e.g., a temperature between the first elevated temperature and ambient temperature, the first elevated temperature, a temperature higher than the first elevated temperature, etc.) while depositing additional layers. In an embodiment, the additive manufacturing apparatus 100 includes a cooler (not shown) configured to cool the cavity 134. Deposition of layers onto the build plate 104 can occur at temperatures below ambient as well.

[0040] If the layer of deposition material deposited in step 302 is the final layer of the workpiece 102, the method 300 proceeds to step 310. In step 310, the workpiece 102 may be heated via the oven 130 to a second elevated temperature at a predetermined second heating rate (which may be greater than or equal to the first predetermined heating rate, or less than or equal to the first predetermined heating rate). The second elevated temperature may be greater than or equal to the first elevated temperature to which the workpiece 102 was heated during step 306. For example, in embodiments, the second elevated temperature is higher than the first elevated temperature. The controller 148 may control the at least one heating element 146 to maintain the temperature within the cavity 134 at the second elevated temperature for a second predetermined period of time to further relieve stresses accumulated at various locations within the workpiece 102. In embodiments, step 310 may also include any other heat treatments that may be desired to improve the strength of the workpiece 102 while in the oven 130, such as a precipitation hardening step and / or a final heat treatment. In the above example using Ti6-4 as the deposition material, the oven 130 is further heated during step 310 such that the workpiece 102 is heated to a second elevated temperature of about 900°C for about two hours. In embodiments, the workpiece 102 may also be subjected to hot isostatic pressing during step 310. For example, the workpiece 102 may be hot isostatically pressed to a second elevated temperature of about 900°C and a pressure of 100 MPa for about two hours.

[0041] In step 312, the temperature of the workpiece 102 is reduced at a predetermined cooling rate by controlling the at least one heating element 146. The temperature within the cavity 134 may be reduced at the predetermined cooling rate until the temperature within the cavity 134 reaches the ambient temperature of the environment of the additive manufacturing apparatus 100. In an embodiment, the predetermined cooling rate is based on the deposition material provided via the material feeds 124 and 126 (e.g., based on a thermal expansion coefficient curve). Such controlled cooling is advantageous for minimizing temperature gradients within the cavity 134 and preventing further buildup of residual stresses within the completed workpiece 102. The predetermined cooling rate may be achieved by selectively cycling or otherwise controlling the at least one heating element 146. In the above example using Ti6-4 as the deposition material, the workpiece 102 is removed from the cavity 134 after step 310, and the temperature of the workpiece 102 is reduced by exposing the workpiece 102 to air. In some embodiments, a fan may be utilized to increase the temperature reduction of the workpiece 102 .

[0042] In the above-described embodiment of the additive manufacturing apparatus 100, the build plate 104 is disposed within a cavity 134 of the oven 130 and is at least partially covered via an oven lid 136 so that the workpiece 102 may be selectively heated or cooled. However, in other embodiments, the additive manufacturing apparatus 100 may be configured to subject the workpiece 102 to a pressurized environment and / or cooling in addition to heating. Thus, for example, the additive manufacturing apparatus 100 may be configured to subject the workpiece 102 to a hot isostatic pressing (HIP) process, which may be advantageous for repairing internal blockages or defects within the workpiece 102. Typically, in conventional additive manufacturing systems, the workpiece 102 must be sent to a post-processing device where it can undergo the HIP process or other subsequent processing. However, by configuring the additive manufacturing apparatus 100 to perform the HIP process as described below, efficiency is improved because the workpiece 102 does not need to be sent to another device for the HIP process. As described below, in some embodiments, the oven 130 can be configured as an autoclave for pressurizing the workpiece 102 within the cavity 134 in addition to heating / cooling the workpiece 102 therein. As used herein, the term autoclave refers to a machine configured to perform industrial and scientific processes that require elevated temperatures and / or pressures relative to ambient temperature and / or pressure. For example, the oven lid 136 may be removed from the furnace body 132 and replaced with an autoclave lid that surrounds and seals the cavity 134 so that the cavity 134 can be pressurized. Thus, the cavity 134 can be heated when the oven lid 136 is placed thereon and then pressurized and / or cooled when the autoclave lid is moved onto the furnace body 132.

[0043] FIG. 4 illustrates an additive manufacturing apparatus 400 configured to build a workpiece 102′ and subject the workpiece 102′ to a HIP process, according to one or more embodiments. The additive manufacturing apparatus 400 is similar to the additive manufacturing apparatus 100 described above and includes a build plate 104′ on which the workpiece 102′ is built, a deposition head 112′ supporting a material nozzle 114′, and an oven lid 136′ that moves with the deposition head 112′. In the illustrated embodiment, the oven lid 136′ and the deposition head 112′ are connected to one another via an oven mounting member 158′, allowing them to move together. However, in other embodiments, the oven lid 136′ and the deposition head 112′ can move together via separate motion systems. One difference is that the additive manufacturing apparatus 400 of FIG. 4 incorporates an autoclave 402 in which the workpiece 102′ is built and in which the workpiece 102′ can be subjected to a HIP process, instead of the oven 130 of the additive manufacturing apparatus 100. Thus, autoclave 402 may include a pressure source 403, as described in more detail below, for increasing the pressure within autoclave 402. As used herein, the term autoclave refers to a machine configured to perform industrial and scientific processes that require elevated temperatures and / or pressures relative to ambient temperature and / or pressure, and autoclaves may also perform cooling cycles.

[0044] In the illustrated embodiment, deposition head 112' is supported on support arms 108' and 110', all of which are disposed within build chamber 128', which is defined within enclosure 401. In embodiments, enclosure 401 may be a housing or a room. In this manner, build chamber 128' may be sealed from an external ambient environment 405 outside of build chamber 128'. Enclosure 401 also has an opening 407, and, as described below, an autoclave 402 is disposed in opening 407 to maintain build chamber 128' in a sealed state and inhibit ingress between external ambient environment 405 and build chamber 128', which may include an inert gas atmosphere or a vacuum atmosphere.

[0045] In the illustrated embodiment, the autoclave 402 includes an autoclave body 404 having an upper autoclave lid 408, a sidewall 410, and a lower autoclave lid 412, which together define a cavity 406. As described herein, the build plate 104′ is movable in the z-direction and can thus be positioned within the cavity 406. The sidewall 410 defines an upper autoclave opening 409 that can be covered and sealed by the upper autoclave lid 408 and a lower autoclave opening 411 that can be covered and sealed by the lower autoclave lid 412. As shown, the lower autoclave opening 411 is disposed in and communicates with the opening 407 such that the opening 407 is closed and sealed when the lower autoclave lid 412 is placed on the sidewall 410. Here, sidewall 410 is supported by the inner surface of housing 401 within build chamber 128′ and extends from the inner surface of housing 401 away from opening 407 such that upper autoclave opening 409 is positioned further from opening 407 within build chamber 128′ than lower autoclave opening 411. In other embodiments, sidewall 410 is positioned within opening 407, and a seal is provided between opening 407 and the outer surface of sidewall 410 such that upper autoclave opening 409 and lower autoclave opening 411 of sidewall 410 are positioned on opposite sides of opening 407.

[0046] The upper autoclave lid 408 is removable from the autoclave body 404 so that the support arms 110′ can position the deposition head 112′ over the build plate 104′, thereby fabricating the workpiece 102′ within the autoclave body 404. In the illustrated example, the upper autoclave lid 408 is suspended from an upper support structure 414 and cables 416, which can extend and retract the cables 416 to raise and lower the upper autoclave lid 408 relative to the sidewalls 410 of the autoclave body 404. In the illustrated embodiment, the upper support structure 414 is mounted within the housing 401, e.g., to the ceiling of the build chamber 128′. However, the upper support structure 414 may be provided external to the build chamber 128′, with the cables extending through the housing 401. In other embodiments, the upper autoclave lid 408 may be attached to the autoclave body 404 via a hinge, so that the upper autoclave lid 408 can be rotated away from the top of the autoclave body 404 sufficiently to position the deposition head 112' and oven lid 136' over the cavity 406, as described below.

[0047] Similarly, the lower autoclave lid 412 is removable from the sidewall 410 of the autoclave body 404 to expose the lower autoclave opening 411, thereby allowing the build plate 104' with the workpiece 102' (when completed) to be removed from the build chamber 128' while the remainder of the autoclave 402 remains within the build chamber 128', sealing the opening 407 in the housing 401. When the upper and lower autoclave lids 408, 412 are both sealingly provided over the upper and lower autoclave openings 409, 411 in the sidewall 410, the cavity 406 is sealed from both the build chamber 128' and the external ambient environment 405, thereby allowing the cavity 406 to be independently controlled (e.g., pressurized, heated, cooled, etc.). However, when the lower autoclave lid 412 is sealed over the lower autoclave opening 411 in the sidewall 410, but the upper autoclave lid 408 is removed from the sidewall 410 to expose the upper autoclave opening 409 to the build chamber 128′, the cavity 406 and the build chamber 128′ communicate with each other while being sealed from the external ambient environment 405. On the other hand, when the upper autoclave lid 408 is sealed over the upper autoclave opening 409 in the sidewall 410, but the lower autoclave lid 412 is removed to expose the lower autoclave opening 411 to the external ambient environment 405, the cavity 406 communicates with the external ambient environment 405, and the build chamber 128′ is sealed from the external ambient environment 405. This allows the workpiece 102′ to be removed without disturbing the build chamber 128′.

[0048] As described above, the oven lid 136' is movable relative to the deposition head 112 (e.g., via the oven mounting member 158') so that when the deposition head 112' is positioned as described above, the oven lid 136' is also positioned over the cavity 406. Thus, when the upper autoclave lid 408 is removed from the side wall 410, the oven lid 136' covers the upper autoclave opening 409 and can surround the cavity 406 so that the cavity 406 can be selectively heated or cooled during deposition, even when the upper autoclave lid 408 is removed. After the deposition head 112' deposits the deposition material, thereby forming the workpiece 102' (i.e., after deposition), the deposition head 112' and oven lid 136' may be moved away from the upper autoclave opening 409 and cavity 406, and then the upper autoclave lid 408 may be moved onto the sidewall 410 of the autoclave body 404 to surround and seal the cavity 406. For example, after deposition, the support arm 110' may rotate the deposition head 112' and oven lid 136' away from the autoclave 402 so that they are not positioned above the cavity 406, and then the upper autoclave lid 408 can be lowered onto the sidewall 410 to seal the upper autoclave opening 409 without being obstructed by the support arm 110', deposition head 112', and / or oven lid 136'. Then, with the upper autoclave lid 408 sealed onto the sidewall 410 and the lower autoclave lid 412 also sealed onto the sidewall 410, the temperature and pressure within the cavity 406 can be set via the heating element 146 and pressure source 403 as may be appropriate for processing the workpiece 102', for example, via HIP processing.

[0049] The build plate 104' may be part of a build plate assembly that also includes a movable base 420, a support shaft 422, and an actuator 424. In the illustrated embodiment, the build plate 104' is mounted on a movable base 420 that rotates the build plate 104' about an axis of rotation extending in the z-direction, as described above with reference to the base plate 105. In other embodiments, the movable base 420 is operable to axially translate the build plate 104' along the axis of rotation extending in the z-direction, thereby facilitating vertical positioning of the build plate 104' within the cavity 406. In other embodiments, the movable base 420 is operable to both rotate the build plate 104' about the axis of rotation and translate the build plate 104' along the axis of rotation.

[0050] The build plate 104′ and the movable base 420 are connected to a support shaft 422. The support shaft 422 extends through the lower autoclave lid 412 and may be operably connected to an actuator 424, which is operable to extend and retract the support shaft 422 (e.g., as an articulating or telescoping arm). Thus, in some embodiments, the support shaft 422 is movable relative to at least a portion of the autoclave body 404, allowing for movement of the build plate 104 in the z-direction between layers of deposition material being deposited on the build plate 104. In some embodiments, the actuator 424 may be communicatively coupled to the controller 148′. In embodiments, the actuator 424 and the support shaft 422 are operable to raise and lower the lower autoclave lid 412, allowing for removal of the lower autoclave lid 412, thereby facilitating removal or ejection of the workpiece 102′. In such embodiments, the lower autoclave lid 412 may be coupled to the support shaft 422 so that the lower autoclave lid 412 can be raised and lowered along with the build plate 104. For example, the support shaft 422 can lower the lower autoclave lid 412 as the build plate 104' is retracted from the cavity 406. In embodiments, the lower autoclave lid 412 can move relative to the support shaft 422. For example, the lower autoclave lid 412 can be removed to expose the lower autoclave opening 411 and the cavity 406, and then the support shaft 422 can be actuated to retract the build plate 104' from the cavity 406. These embodiments allow the HIPed workpiece 102' to be removed from the build plate 104' while maintaining a barrier between the build chamber 128' and the external ambient environment 405 when the lower autoclave lid 412 is sealed onto the sidewall 410. In other embodiments not shown, the support shaft 422 can also support and move the autoclave body 404 in the z-direction (with or without the upper autoclave lid 408 and / or lower autoclave lid 412 provided thereon).For example, in such an embodiment, actuator 424 may be utilized to raise and lower autoclave 402 into and out of build chamber 128' of housing 401.

[0051] In embodiments, additive manufacturing apparatus 400 may incorporate multiple autoclaves, as described below. Thus, for example, while workpiece 102' is being built in autoclave 402, other workpieces may be undergoing HIP processing in other autoclaves, other built and HIPed workpieces may be removed from their respective autoclaves, and yet other autoclaves may be prepared for new builds.

[0052] FIG. 5 illustrates an additive manufacturing apparatus 500 for building and HIPing multiple workpieces 502a-502c, according to one or more embodiments. Similar to the additive manufacturing apparatus 400 of FIG. 4, the additive manufacturing apparatus 500 includes a deposition head 112′ and an oven lid 136′ that is movable with the deposition head 112′; however, as described below, the additive manufacturing apparatus 500 is operable to build and process multiple workpieces 502a-502c. In the illustrated example, the oven lid 136′ is attached to the deposition head 112′; however, in other embodiments, they are not attached but move together as described above. In the illustrated embodiment, the additive manufacturing apparatus 500 includes a first autoclave 504a, a second autoclave 504b, and a third autoclave 504c, each configured as described above with reference to the autoclave 402 of FIG. 4. However, it should be understood that the additive manufacturing apparatus 500 may include more or less than three autoclaves 504a-504c without departing from this disclosure. In the illustrated embodiment, the housing 401 includes a first opening 507a associated with the first autoclave 504a, a second opening 507b associated with the second autoclave 504b, and a third opening 507c associated with the third autoclave 504c.

[0053] In the illustrated embodiment, each of the autoclaves 504a-504c includes an individual pressure source 503a-503c associated therewith. However, in other embodiments, a single power source may be provided to individually pressurize any one or more of the three autoclaves 504a-504c, independent of each other.

[0054] Here, the additive manufacturing apparatus 500 is building a first workpiece 502a in a first autoclave 504a, as described above with reference to Figure 4. While the first workpiece 502a is being built in the first autoclave 504a, a second autoclave 504b is HIPing a second workpiece 502b in its cavity 406. While the first workpiece 502a is being built in the first autoclave 504a and the second workpiece 502b is being HIPed in the second autoclave 504b, a third autoclave 504c is opened by removing the lower autoclave lid 412 and removing the build plate 104' from the cavity 406 of the third autoclave 504c through the lower autoclave opening 411 and a third opening 507c in the build chamber 128'. This allows the third workpiece 502c to be removed from the additive manufacturing apparatus 500 without interrupting the operation of the build chamber 128′ and the first and second autoclaves 504a, 504b. As described above, the sidewall 410 of the third autoclave 504c is sealed around the opening 507c in the build chamber 128′, and the upper autoclave lid 408 of the third autoclave 504c is sealed onto its sidewall 410. The sidewall 410 and the upper autoclave lid 408 of the third autoclave 504c thus form a physical barrier that isolates and seals the environment within the build chamber 128′ from the external ambient environment 405. Thus, the third workpiece 502c can be removed from the cavity 406 of the third autoclave 504c, which is shown as being exposed to the external ambient environment 405, without disturbing the build chamber 128', which may include an inert gas atmosphere or a vacuum atmosphere.

[0055] Each of the autoclaves 504a-504c can be operated in this manner, thereby allowing removal of any of the workpieces 502a-502c without disturbing the environment within the build chamber 128′ while continuously sealing the environment within the build chamber 128′ from the external ambient environment 405. By providing each of the autoclaves 504a-504c with an upper autoclave lid 408 and a lower autoclave lid 412 that are separately removable from the sidewalls 410 and sealing each of the sidewalls 410 within a particular one of the openings 507a-507c associated therewith, removal of one or more of the workpieces 502a-502c can be permitted while maintaining the environment within the build chamber 128′.

[0056] In embodiments, the support arm 110' can rotate about a vertical axis extending in the z-direction to move the deposition head 112' from the first autoclave 504a to either the second autoclave 504b or the third autoclave 504c. Here, the deposition head 112' can access the cavity 406 of either the second autoclave 504b or the third autoclave 504c when the associated upper autoclave lid 408, as illustrated with respect to the first autoclave 504a, is moved (or raised) out of the way of the support arm 110' and deposition head 112' to expose the upper autoclave opening 409. Also, in embodiments in which the oven lid 136' is integrally attached to the deposition head 112, such removal of the upper autoclave lid 408 allows the deposition head 112' to position the oven lid 136' over the cavity 406, thereby enabling heating during deposition. In such an embodiment, deposition material may be supplied to the deposition head 112' from the upper supply system 510a and / or the lower supply system 510b. In this manner, deposition material can be supplied to the deposition head 112' without impeding or blocking such supply as the support arm 110' moves and rotates between the autoclaves 504a-504c.

[0057] FIG. 6 illustrates an additive manufacturing apparatus 600 having autoclaves 604a-d arranged around support arms 108′, 110′, in accordance with one or more embodiments. In the illustrated example, support arm 110′ can rotate deposition head 112′ clockwise or counterclockwise, as indicated by arrow 606. However, it should be understood that autoclaves 604a-604d may be oriented differently relative to support arms 108′, 110′. In the illustrated example, a first workpiece (not shown) is being built in first autoclave 604a. Also in the illustrated example, each of the other autoclaves 604b-604d may HIP their respective workpieces. Furthermore, one or more of the other autoclaves 604b-604d may finish HIPing their workpieces and be lowered out of the build chamber to remove the workpiece. Additionally, any one or more of the other autoclaves 604b-604d may not have any workpieces therein and may be preparing for a new build. In this manner, additive manufacturing machine 600 efficiently builds and processes multiple workpieces without sending the workpieces to another machine / factory for subsequent processing.

[0058] In view of the above, it should be appreciated that providing a heated build chamber in close proximity to a workpiece being built by an additive manufacturing device provides efficiencies in heating the workpiece while also providing facilities for relieving stresses accumulated in the workpiece during the additive manufacturing process. The workpiece may be a large-format part that grows in the heated build chamber on a build plate that descends as the workpiece is built. Such a heated build chamber may be provided by an oven including a furnace body defining a cavity for the heated build chamber and an oven lid positioned between the build plate on which the workpiece is built and the furnace body. The oven lid includes an opening that allows an energy beam and / or material feed from a deposition head of the additive manufacturing device to reach the build plate, thereby providing a layer of deposition material on the build plate. The oven lid can move in conjunction with the deposition head during deposition of a layer of deposition material such that the heated build chamber is surrounded by the oven regardless of the position of the deposition head. In this way, the heating efficiency of the oven is fully utilized, reducing heating time and thus saving time required for stress relief. The oven can maintain the workpiece and build plate at a temperature suitable to prevent distortion or cracking as the workpiece grows, and in embodiments, during the build of the workpiece, material deposition can be paused and the oven temperature can be further increased to provide "in-process" stress relief. In embodiments, an autoclave can be utilized instead of an oven, with a heated build chamber provided within the autoclave. In addition to heating, the autoclave allows for pressurization of the build chamber, so that workpieces built in the autoclave can be subjected to pressure treatments such as hot isostatic press treatment, and the autoclave can also be utilized to allow an operator to cool the workpiece. If an autoclave is utilized, the autoclave can include a removable top lid and / or a removable bottom lid, which can be removed separately.The removable top lid allows the top lid, which moves in conjunction with the deposition head, to be moved over the heated build chamber during material deposition, and after the deposition head and oven lid have been moved, the removable top lid can be secured over the autoclave to pressure process the built workpiece. Then, after the workpiece is completed, the removable bottom lid can be removed to remove the completed workpiece from the build chamber of the autoclave. In embodiments, multiple autoclaves may be provided within the build chamber for producing multiple workpieces, each autoclave having a removable top lid and a removable bottom lid, such that a workpiece is built by the deposition head in a first autoclave covered by the oven lid, and another workpiece is pressure processed in a second autoclave, while a completed third workpiece can be retrieved from the third autoclave without disturbing the build chamber.

[0059] Additional aspects of the embodiments described herein are provided by the subject matter of the following appended claims.

[0060] (Appendix 1) A method for additively manufacturing a workpiece, comprising: translating a deposition head of an additive manufacturing apparatus over a build surface of a build plate to form a layer of material, the deposition head comprising a material nozzle through which the material is deposited as a deposition material, and an energy source configured to apply an energy beam to the deposition material to melt the deposition material at the build surface; and heating the deposition material using an oven after the layer has been deposited on the build surface, the oven comprising a furnace body defining a cavity in which the build plate is disposed, and an oven lid movable with the deposition head and positionable on the furnace body, wherein when the oven lid is positioned on the furnace body, the oven lid and the furnace body surround the cavity to provide a heated build chamber upon application of heat.

[0061] (Appendix 2) The method according to appendix 1, further comprising pressurizing the deposition material in the cavity after heating.

[0062] (Appendix 3) The method of appendix 1 or appendix 2, wherein pressurizing the deposition material in the cavity includes moving the deposition head away from the build plate to remove the oven lid from the furnace body, placing an autoclave lid on the furnace body to seal the cavity, and pressurizing the cavity.

[0063] (Appendix 4) The method of appendix 2, wherein the pressurizing is hot isostatic pressing of the deposition material in the cavity after heating, and the hot isostatic pressing of the deposition material in the cavity includes moving the deposition head away from the build plate to remove the oven lid from the furnace body, placing an autoclave lid on the furnace body to seal the cavity, heating the cavity, and pressurizing the cavity with an isotropic gas pressure.

[0064] (Appendix 5) The method of any of the preceding appendices, wherein the deposition head is movably mounted to a support structure such that the deposition head is movable in at least a first direction by an amount corresponding to a range of motion of the deposition head.

[0065] (Appendix 6) The method of any of the preceding appendices, wherein translating the deposition head on the build plate includes moving the deposition head a first distance in the first direction on the build plate relative to the support structure, the first distance being less than or equal to the range of motion.

[0066] (Appendix 7) A method according to any of the preceding appendices, wherein the furnace body has a sidewall with an upper end, and the underside of the oven lid physically contacts the upper end of the sidewall of the furnace body over at least a portion of the range of motion of the deposition head.

[0067] (Appendix 8) The method of any of the preceding appendices, wherein the underside of the oven lid physically contacts the upper end of the side wall of the furnace body throughout the entire range of motion of the deposition head.

[0068] (Appendix 9) The method of any of the preceding appendices, further comprising, after heating the deposition material, discharging excess portions of the deposition material from the heated shaping chamber through a material conduit extending through the furnace body, the material comprising a metal powder or an alloy powder.

[0069] (Appendix 10) A method according to any of the preceding appendices, wherein the material conduit extends through a portion of the shaping plate and through the floor of the furnace body.

[0070] (Appendix 11) A method according to any of the preceding appendices, wherein the furnace body has a sidewall, and the underside of the oven lid physically contacts the upper end of the sidewall of the furnace body over at least a portion of the range of motion of the deposition head.

[0071] (Appendix 12) The method of any preceding appendix, further comprising depositing and fusing a final layer of the workpiece, and further comprising using the oven to heat the workpiece to a second elevated temperature higher than the first elevated temperature, and maintaining the workpiece at the second elevated temperature for a predetermined period of time to further relieve stresses built up in the workpiece.

[0072] (Appendix 13) The method of any preceding appendix, further comprising, after the predetermined period of time, controlling at least one heating element of the oven to reduce the temperature of the workpiece to the ambient temperature at a predetermined cooling rate.

[0073] (Appendix 14) The method according to any of the preceding appendices, wherein the oven lid is attached to the deposition head.

[0074] (Appendix 15) A method according to any of the preceding appendices, wherein heating the deposition material includes moving the oven lid in conjunction with translational movement of the deposition head so that the heated shaping chamber is substantially enclosed by the oven lid and the furnace body regardless of the position of the deposition head.

[0075] (Appendix 16) The method of any preceding appendix, further comprising determining that residual stress in the workpiece is greater than a predetermined amount.

[0076] (Appendix 17) A method of additively manufacturing a workpiece, comprising: depositing material as a layer of material on a build surface of a build plate by translating a deposition head of an additive manufacturing apparatus over the build surface, the deposition head including a material nozzle through which the layer of material is deposited onto the build plate; depositing material; melting the layer of material using an energy source configured to apply an energy beam to the material at the build surface of the build plate to form a layer of the workpiece; determining that residual stress in the workpiece is greater than a predetermined amount; and melting the layer of material using an energy source configured to apply an energy beam to the material at the build surface of the build plate to form a layer of the workpiece. heating a layer of the workpiece using an oven in response to the determination that the residual stress in the workpiece is greater than the predetermined amount, the oven including: a furnace body defining a cavity in which the build plate is disposed; an oven lid movable with the deposition head and positionable on the furnace body, wherein when disposed on the furnace body, the oven lid and furnace body enclose the cavity, thereby providing a heated build chamber upon application of heat; and a heating element configured to heat the heated build chamber, the oven lid moving in conjunction with translational movement of the deposition head.

[0077] (Appendix 18) The method of appendix 17, wherein heating the layer using the oven includes maintaining the layer of material at a first elevated temperature higher than ambient temperature, the layer of material including a final layer of the workpiece, and further including: using the oven to heat the workpiece to a second elevated temperature higher than the first elevated temperature and maintaining the workpiece at the second elevated temperature for a predetermined period of time to further relieve stresses accumulated in the workpiece; and after the predetermined period of time, reducing the temperature of the workpiece to the ambient temperature at a predetermined cooling rate by controlling at least one heating element of the oven.

[0078] (Appendix 19) The method of appendix 17 or appendix 18, further comprising hot isostatically pressing the deposited material in the cavity after heating, wherein hot isostatically pressing the deposited material in the cavity comprises moving the deposition head away from the build plate to remove the oven lid from the furnace body, placing an autoclave lid on the furnace body to seal the cavity, heating the cavity, and pressurizing the cavity with an isotropic gas pressure.

[0079] (Supplementary Note 20) The method according to any one of Supplementary Notes 17 to 19, wherein the determining is performed automatically via a controller.

[0080] (Appendix 21) 1. An additive manufacturing apparatus comprising: a housing defining a build chamber and including an opening; an autoclave coupled to the opening of the housing, the autoclave comprising: a sidewall sealed around the opening of the housing and at least partially defining a build cavity, the sidewall having an upper autoclave opening communicating with the build cavity and a lower autoclave opening opposite the upper autoclave opening; an upper autoclave lid disposed on the sidewall and sealably covering the upper autoclave opening, the upper autoclave lid being removable from the sidewall to expose the upper autoclave opening and the build cavity; and a lower autoclave lid disposed on the sidewall and sealably covering the lower autoclave opening, the lower autoclave lid being removable from the sidewall to expose the lower autoclave opening and the build cavity. a build plate assembly coupled to the autoclave, the build plate assembly comprising: a build plate; and an actuator operably coupled to the build plate for axially translating the build plate relative to the build cavity of the autoclave, the actuator operable to move the build plate through the lower autoclave opening into or out of the build cavity when the lower autoclave lid is removed from the lower autoclave opening; a deposition assembly disposed in the build chamber, the deposition assembly comprising: a deposition head movable relative to the autoclave; a material nozzle connected to the deposition head and movable with the deposition head, the material nozzle operable to deposit material onto the build plate when positioned over the upper autoclave opening with the upper autoclave lid removed from the upper autoclave opening and when the build plate is positioned within the build cavity; an energy source connected to the deposition head and movable with the deposition head, the energy source operable to apply energy to the deposited material through the material nozzle to melt the deposited material to form the workpiece; and an oven lid movable with the deposition head and movable in conjunction with the deposition head to cover the upper autoclave opening of the autoclave as the deposition assembly deposits molten material, the oven lid being positionable over the upper autoclave opening of the autoclave when the upper autoclave lid is removed from the sidewall. An additive manufacturing device comprising:

[0081] (Appendix 22) An additive manufacturing apparatus as described in Appendix 21, wherein the build plate assembly further comprises a movable base on which the build plate is placed, the movable base being operable to rotate the build plate about an axis and / or to translate the build plate along the axis.

[0082] (Supplementary Note 23) When the lower autoclave lid is disposed on the side wall so as to sealably cover the lower autoclave opening, and when the upper autoclave lid is removed from the upper autoclave opening, the build cavity of the autoclave communicates with the build chamber of the housing but is sealed from the external ambient environment; When the upper autoclave lid is disposed on the side wall so as to sealably cover the upper autoclave opening, and when the lower autoclave lid is removed from the lower autoclave opening, the build cavity is in communication with the external ambient environment but is sealed from the build chamber of the housing; 23. The additive manufacturing apparatus of claim 21 or 22, wherein the autoclave heats and pressurizes the build cavity when the upper autoclave lid and the lower autoclave lid are both positioned on the side wall.

[0083] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the scope of the claimed subject matter. Thus, it is intended that the present specification cover modifications and variations of the various embodiments described herein, provided that such modifications and variations come within the scope of the appended claims and their equivalents.

Claims

1. A method (300) for additively manufacturing a workpiece (102), comprising: forming a layer of material by translating a deposition head (112) of an additive manufacturing device (100) over a build surface of a build plate (104), the deposition head (112) comprising a material nozzle (114) through which the material is deposited as a deposition material, and an energy source configured to apply an energy beam (122) to the deposition material to melt the deposition material at the build surface; heating the deposition material using an oven (130) after the layer has been deposited on the build surface, the oven (130) comprising a furnace body (132) defining a cavity (134) in which the build plate (104) is disposed, and an oven lid (136) movable with the deposition head (112) and positionable on the furnace body (132), the oven lid (136) and the furnace body (132) configured such that when the oven lid (136) is positioned on the furnace body (132), the oven lid (136) and the furnace body (132) surround the cavity (134) to provide a heated build chamber (128) upon application of heat; A method comprising:

2. The method (300) of claim 1, further comprising pressurizing the deposition material in the cavity (134) after heating.

3. Pressurizing the deposition material in the cavity (134) moving the deposition head (112) away from the build plate (104) and removing the oven lid (136) from the furnace body (132); placing an autoclave (402) lid on the furnace body (132) to seal the cavity (134); and pressurizing the cavity (134). The method (300) of claim 2.

4. the pressing is hot isostatic pressing of the deposited material in the cavity (134) after heating; The hot isostatic pressing of the deposited material in the cavity (134) comprises: moving the deposition head (112) away from the build plate (104) and removing the oven lid (136) from the furnace body (132); placing an autoclave (402) lid on the furnace body (132) to seal the cavity (134); heating the cavity (134) and pressurizing the cavity (134) with an isotropic gas pressure. The method (300) of claim 2.

5. 5. The method (300) of any one of claims 1 to 4, wherein the deposition head (112) is movably mounted to a support structure such that the deposition head (112) is movable in at least a first direction by an amount corresponding to a range of motion (152) of the deposition head (112).

6. Translating the deposition head (112) on the build plate (104) includes moving the deposition head (112) a first distance in the first direction on the build plate (104) relative to the support structure, the first distance being within the range of motion. The method (300) of claim 5, wherein the thickness is equal to or less than the circumference (152).

7. 7. The method of claim 6, wherein the furnace body includes a sidewall having an upper end, and wherein a lower surface of the oven lid physically contacts the upper end of the sidewall of the furnace body over at least a portion of the range of motion of the deposition head.

8. 8. The method (300) of claim 7, wherein the lower surface (151) of the oven lid (136) physically contacts the upper end of the sidewall (138) of the furnace body (132) throughout the range of motion (152) of the deposition head (112).

9. 5. The method (300) of claim 1, further comprising, after heating the deposition material, discharging excess portions of the deposition material from the heated shaping chamber (128) through a material conduit (164) extending through the furnace body (132), wherein the material comprises a metal powder or an alloy powder.

10. 10. The method (300) of claim 9, wherein the material conduit (164) extends through a portion of the shaped plate (104) and through a floor (140) of the furnace body (132).

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