Patent ID: 12226824

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings is intended to provide a description of various exemplary embodiments of the concepts disclosed herein and is not intended to represent the only embodiments in which the disclosure may be practiced. The terms “exemplary” and “example” used in this disclosure mean “serving as an example, instance, or illustration,” and should not necessarily be construed as excluding other possible arrangements or as preferred or advantageous over other embodiments presented in this disclosure. The detailed description includes specific details for the purpose of providing a thorough and complete disclosure that fully conveys the scope of the concepts to those skilled in the art. However, the disclosure may be practiced without these specific details. In some instances, well-known structures and components may be shown in block diagram form, or omitted entirely, in order to avoid obscuring the various concepts presented throughout this disclosure. In many instances, diagrams are shown not to scale in order to highlight and clarify relevant portions of the disclosure.

This disclosure is directed generally to structures and techniques for the rapid removal of unfused powder that remains in the powder bed in a powder bed fusion (PBF) 3-D printer, for example, after rendering one or more build pieces. One of several key benefits of the rapid removal of unfused powder described herein is reduced post-processing times. This disclosure also presents techniques for exposing build piece(s) having powder beds that were recently vacated of unfused powder to a corresponding rapid flow of uniformly cooled (or heated) powder into the powder bed that surrounds the build pieces. The uniformly cooled (or heated) powder can mitigate the adverse effects on the build pieces of temperature fluctuations caused by the heat trapped in the lower powder layers during the fusion process in 3-D printing. The uniformly cooled (or heated) powder can promote a generally constant microstructure of the resulting build pieces. These uniform microstructures help generate printed parts achieve predictable thermal properties and other beneficial properties spanning the entire range of the part, and can help minimize the negative effects on the build pieces caused by temperature variations due to the trapped heat in the unfused powder.

PBF systems are 3-D printers that generally include a build plate on which a powder bed composed of multiple powder layers can be successively deposited. An energy beam source is positioned over the powder bed. The energy beam source may include, for example, a laser, an electron beam source, etc. The energy beam source relies on information compiled from a computer aided design (CAD) model to scan selected cross-sectional regions of successive layers of the powder during a print cycle and to thereby form a resulting structure representing the CAD model.

An entire PBF cycle for rendering a single layer may include a plurality of separate operations. These operations may include a material dispensing procedure, a re-coat cycle, and an exposure (print) cycle. In some configurations, certain of these cycles may overlap or be considered part of the same procedure. The dispensing procedure is a necessary step to feed material or powder to the 3D printer for forming layers. The dispensing procedure involves dispensing material to a container in the printer (e.g., a hopper) that can be used by the printer to form a layer. During the dispensing procedure, a depositor receives the stored powder from the hopper via a powder dispenser, and thereafter, the depositor dispenses the powder onto a build plate. It should be noted that the depositor in this example can itself act as a hopper, since one of its main tasks is to store the received power before dispensing it.

In an ensuing re-coat cycle, a re-coater spreads the powder evenly across a powder bed and/or build plate to form a layer. During the re-coat cycle, as the re-coater traverses the powder bed, a leveler, such as a specially shaped blade or roller, may be coupled to the re-coater. The leveler may be used to spread the deposited powder into a level, evenly-shaped layer across the powder bed.

After the powder layer is deposited, an exposure cycle may occur in which the energy beam, based on instructions from a print controller, selectively scans the powder bed to fuse portions of the deposited layer by forming a weld pool of melted powder in regions identified by the controller. The weld pool quickly solidifies into a portion of the intended cross-section of the build piece being printed. The various print operations (including the dispensing, re-coat and exposure cycles, for example) may continue in succession until the requisite number of layers are deposited and the build piece is complete. Thereafter, the un-fused, loose powder particles and the build piece can be removed from the PBF printer and the build plate can be prepared for another print run.

More than one build piece may be printed during one print job, depending on considerations like the relative sizes of the build pieces and the powder bed. These considerations are largely accounted for in an earlier computer aided design (CAD) process or simulation conducted prior to the print job, wherein a designer renders a three-dimensional computer model or representation of the build piece(s). The CAD designs may be compiled over the course of a few intermediate steps (e.g., support structures may be designed and generated where necessary to support overhanging portions of the build piece during printing, etc.). Ultimately the CAD designs are compiled into a design model with print instructions that are readable by the 3-D printer.

During a print operation, the 3-D printer uses a build plate to support the build piece and the unfused powder that accumulates as the layers are added during the re-coat cycle. A build plate is conventionally a singular, integrated platform (e.g., a flat, planar piece of material) that supports a powder bed receptacle, in conjunction with powder bed receptacle walls. That is, during each cycle, powder is dispensed on the build plate and spread over the build plate as a layer using a re-coater device (e.g., a leveler) to spread the powder. After the re-coat cycle, the print/exposure cycle relies on print instructions from the controller or other processor to manipulate an energy beam source (e.g., a laser, electron beam, etc.) to selectively fuse portions of the layer that correspond to a section of the build piece for that layer, as described above.

The controller can use a compiled design model of the build piece from the CAD operations, and/or other information pertaining to the generation of support structures that may be needed. While not part of the build piece itself, the support structures may be needed to attach from the build piece to portions of the build plate, e.g., in places where the angle formed by the build piece and the build plate exceed 45° (45 degrees).

As noted above, a current shortcoming of powder fed 3-D printers is that, as the controller begins to accumulate layers in the powder bed, the unfused powder tends to trap heat in the powder bed resulting from the fusion process. The effect of the heat is generally worse at regions closer to the build plate, since layers have been added that effectively trap the heat and the effect can be amplified as the layers go lower toward the build plate. The result can be a range of temperatures within the unfused powder that are concurrently affecting the microstructure that forms the build plate.

For example, at a microscopic level, the powder may be composed of a plurality of generally spherically-shaped pieces. Because an arrangement of generally spherical volumes only makes contact at certain small regions where the neighboring spheres are actually touching, the remaining regions not touching tend to trap the high temperatures, making the overall powder a poor conductor of heat. Even if the powder is assumed to be in shapes other than perfect spheres, typically the powder is not making continuous contact with other powder particles, and thus the powder remains a poor conductor. In effect, heat is trapped in the unfused powder and can have a deleterious effect on the build piece as layers are added.

Thus, at the conclusion of the print job, it is generally important to remove the powder as rapidly as possible to terminate these undesirable effects imposed by the trapped heat in the powder. Many conventional implementations separate the build pieces from the unfused powder at the conclusion of the print job by using a vacuum device that is directed at various portions of the build plate. This is a slow and time-consuming manual process, which becomes even slower (and progressively less effective) as the print jobs become more complex and/or use a higher density. Thus, conventionally after the print job, the unfused powder can undesirably linger about adjacent portions of the build piece(s) for an extended period of time before the powder can be removed. This extended time period means that the build piece(s) remain exposed to the undesirable temperature gradients caused by heat trapped in the powder. These temperature gradients can directly affect the microstructure of the build piece in different ways, depending on the temperature of the adjacent powder at a specifically defined region of the build piece. The build piece can, as a result, become structurally compromised by having uneven or poorly formed microstructures that can later loose strength or other properties, malfunction or eventually even break under stress.

In recognition of these problems with conventional powder removal, newer equipment has been marketed that can invert the entire build plate to dump the powder. In other attempted solutions, new equipment can use high velocity or high pressure air to remove the powder. In the former case of inversion of the build plate, one downside can be damage to the various seals between the build cylinder/plate and other associated mechanisms from such handling. The inversion can also adversely affect the build piece itself, as the forces of gravity and the torque caused by the rapid “flip” of the freshly-fused build piece can adversely affect the build piece during the inversion. Conversely, in the latter case of using high velocity or high pressure air, using this solution alone can be equally time-intensive, ineffective especially for more complex designs, and potentially damaging to the build piece being stricken with air at these high velocities or being subject to high pressures immediately after being printed.

Accordingly, in one aspect of the disclosure, the negative effects of the unfused powder are addressed in rapid fashion by the build piece itself. These techniques, described below, preserve the structural integrity of the build piece while rapidly removing the powder (and hence the potentially damaging temperature gradient) from the build chamber. In various embodiments, the build piece includes a first structure and a second structure (each of which may include a plurality of respective first or second structures, depending on the implementation) to enable rapid removal of unfused powder, e.g., after the build piece is printed. These first and second structures provide the build plate with features for allowing the removal of unfused powder from the build chamber by allowing it to drain through the build plate, including immediately on conclusion of the print. The build plate may include a second structure, such as a static grid, having configurable features (e.g., a plurality of first structures) that open and close channels for allowing rapid powder egress. Examples of these rapid powder removal techniques are provided below. Support structures in this case would need to tie only to the second structure—in this embodiment, the static portion of the build plate. During the period of powder removal in some embodiments, the build piece is fused to the second structure by virtue of the energy beam acting on the first few layers at the beginning of the print job. A majority of the cross-sectional area occupied by the build piece will likely contact, and therefore fuse to, the second structure(s). As the build piece is printed over a period of print cycles, the base of the build piece is consequently fused to the second structure(s). While the strength of this fusion may be deliberately marginal, with lower temperatures used and/or less area affected, for example, the fusion of the base of the build piece to the build plate can still be sufficiently strong to enable the second structure(s) to support the build piece during rapid powder removal, but not so strong as to require another process involving heat to separate the two after the print job. This means that during the rapid powder removal process, the second structure(s) can provide sufficient support for the build piece by stabilizing it. The second structure(s) also can support the build piece during the rapid powder egress regardless of whether the build piece is fused to the second structure(s) since the apertures in the second structure are ordinarily made too small for the build piece to pass through. In various embodiments discussed below (see, e.g.,FIG.4and accompanying text), the powder itself can be used as a means of support for the build piece. During subsequent powder removal, the second structure(s) prevent the build piece from falling through the build plate at least because the first structure(s) used to pass the powder through holes in the second structure(s) are generally too small for the build piece to impenetrate.

One of several benefits of this feature is an improvement in post-processing times for additively manufactured parts, which is generally beneficially to industries that rely on AM powder bed technologies. Improved post-processing rates can be very important where the materials used are sensitive to residual stress driven cracking such as, for example, laser-based powder bed fusion titanium allows.

A second benefit of the disclosed technology is the ability of a PBF system to exchange the unconsolidated powder volume surrounding the part. As noted, for certain materials this powder is highly insulating due to poor conduction between the individual powder particles. This in effect can result in temperature build-up within the build chamber over the print duration, which in turn can result in undesirable microstructure variation at the top of the build piece versus the bottom. Exchanging powder can mitigate this temperature variation. Therefore, in various embodiments, the powder is exchanged during, rather than only after, a print job. Older heated powder can be routed outside the build chamber and separated from the build chamber via an insulation layer. Meanwhile, new, cooled powder can be dispensed from a new hopper and provided to surround the build piece. The cooled powder can help the build piece maintain a substantially uniform microstructure. In various embodiments, a new batch of powder that is loaded into the build chamber for surrounding the build piece(s) can also be pre-cooled to a desired temperature such as by a cryogenic process. Combination of this process with ultrasonic vibrations (e.g., from one or more ultrasonic transducers arranged in the PBF system) can be used to cause movement of the new powder supply and encourage the new powder to settle in place quickly after the exchange. After cooling the build piece to a desired uniform microstructure temperature, the powder can be ejected and replaced, or further printing can occur and additional layers added onto the existing powder.

In addition, rapid powder removal/exchange according to the embodiments described herein can be used to expose the build piece(s) or some portion thereof to enable direct cooling such as by convection, which would otherwise be precluded by the surrounding powder. Rapid powder removal or exchange, whether during the print job or at the termination of the print job, can facilitate in situ heat treatment of build pieces as both heated or cooled gasses can theoretically be introduced into the build chamber depending on the types of materials used and the design objectives for the build piece.

In various embodiments, rapid powder removal can be done before the build is complete (e.g., in the middle of the build) if a defect is detected in the build piece. Removal of the powder may expose the defect so that it may be fixed, e.g., with a welding device that remelts the area of the defect. Once the defect is corrected, powder can be deposited back onto the build plate up to the correct level to resume printing.

FIG.1Ais a bottom view illustrating an exemplary build plate in accordance with an embodiment. The build plate can be used in connection with a 3-D printer, such as the PBF system100shown inFIG.1C. Referring toFIG.1A, the bottom view of the build plate is a view looking up from the floor at the underside of the build plate. The bottom view ofFIG.1Ashows a line AA, which is used in a subsequent illustration to provide a sectional view of the build plate. As shown, the bottom view of the build plate includes a first structure139and a second structure107. Frame160can be seen surrounding the build plate as part of the second structure107, but frame160need not be limited to the exterior portion of the build plate. Instead, frame160can be the portion of the build plate that holds the second structure107together as one piece. However, in the view ofFIG.1A, only limited portions of the second structure107are visible.

Shown further inFIG.1Ais a cross-sectional view of a piston170, which is attached in these embodiments to a first structure139of the build piece. Piston170, which is located in a cavity region beneath the build chamber, is attached to the first structure139. In various embodiments, a plurality of pistons or other connective devices may be separately connected to a respective plurality of first structures. In this embodiment, first structure139includes a single structure that can be manipulated by piston179as further shown below.

FIG.1Afurther shows a plurality of powder flow channels191, which can be used to effect rapid powder removal when the first and second structures are separated. In other embodiments (e.g.,FIG.5-6), a plurality of first structures may instead be fitted within respective apertures of a second structure to form a build plate. In some examples, the first structures are rotatably coupled to the second structure via edges of the apertures. Rapid powder flow in those embodiments can be achieved by removing (e.g., rotating and lowering) the first structures from the apertures of the second structure(s).

FIG.1Bis a top view illustrating the build plate ofFIG.1Ain accordance with an embodiment. The view inFIG.1Bis of the same collection of structures asFIG.1A, except thatFIG.1Bis viewed from directly above the build plate. As shown by the legend on the right, the build plate in this embodiment also uses first and second structures139and107. The second structure107, which is widely viewable in this figure, includes an array of apertures156. The edges158of apertures156are fitted with upward-protruding portions177of the first structures139to form a solid, flat build plate for supporting both the build plate and the unfused powder during printing. A cross-section of a build piece109is also shown resting on the build plate. Notably, build piece109is supported by the fixed regions of second structure107, such that when the upward protruding portions of the first structures139in apertures156are vacated using piston139(FIG.1A) and the apertures156effectively form powder holes for rapidly vacating powder, build piece remains firmly in place, supported by the fixed regions of second structure107beneath it.

WhileFIGS.1A and1Bshow a single first structure that is manufactured with upward protrusions that extend into the array of apertures156build into a single second structure107, in other embodiments the first structure and/or the second structure may be a plurality of separate structures. For example, in one embodiment, one first structure139may be associated with one aperture, such that each of the first structures139may be connected (e.g., by a common cross-bar array under the build plate) or alternatively, each of the first structures139may be structurally distinct, and individually controlled by a separate connector (see, e.g.,FIG.3). It will be appreciated, in short, that the rapid powder removal mechanism may be accomplished using a second structure (or plurality thereof) for supporting the build piece(s), and a first structure (or plurality thereof) for supporting the powder layers along with the second structure during printing, and then subsequently for exposing apertures out of which powder can flow. Stated differently, a number of different geometries of the first and second structures can be used to accomplish the rapid powder removal technique as described in this disclosure.

FIG.1Cis a front sectional view of a 3-D printer illustrating exemplary powder dispensing and re-coating procedures and illustrating the build plate taken along line AA ofFIGS.1A-Bin accordance with an embodiment. In particular, in the example ofFIG.1C, the 3-D printer is a PBF system and the build plate uses a first structure139and a second structure107as shown inFIGS.1A and1B.

In the embodiment shown, powder bed receptacle wall112is intended to encompass and provide sidewall support for the entire powder bed121. For simplicity, however, a front portion of powder bed receptacle wall112is omitted to display the powder bed121.FIG.1Cshows the dispensing and the re-coat cycle in one figure. Re-coater182is first shown at a time t=t0underneath powder dispenser133and above a left side of powder bed receptacle wall112. A hopper141provides powder117via the powder dispenser133to a depositor115. The depositor is arranged with re-coater182and moves along a surface of the powder bed during a subsequent re-coat cycle. During the dispensing cycle, depositor115is filled with at least enough powder117to provide one layer to the powder bed121, and typically includes a surplus to account for a layer that may require additional powder. Re-coater182further includes a leveler119, which may be a specially-shaped blade or roller for spreading the powder evenly during the re-coat cycle.

After the depositor115is filled with powder117during the dispensing procedure, the re-coater182including at least the depositor115and leveler119moves across the powder bed121in the direction of the “Arrow A”, and the re-coater182uses leveler119to spread a layer of powder. In this figure it is assumed that build piece109is being printed, and an additional powder layer125having a thickness123(scale exaggerated for clarity) is formed over the earlier-deposited layers.

The re-coater182is also shown at a subsequent time t1—namely, subsequent to the dispensing procedure. During time t1, the re-coater182may continue to use leveler119to evenly spread the powder layer until it reaches the right side of powder bed121, after which the re-coater182may return to the starting point under the powder dispenser133, or it may stay on the far right of the powder bed121. In either case, the powder bed is cleared for the subsequent print cycle (FIG.1D).

FIG.1Cfurther shows a second hopper142filled with powder and positioned adjacent first hopper141. The powder in second hopper142can be used in a powder swap, e.g., at a point where it is desired to replace the used powder117in powder bed121with fresh or new powder. In various embodiments, the second hopper142is insulated, or otherwise cooled or heated to a specified temperature for optimal use in the powder swap. The powder swap can be initiated and controlled manually, or automatedly via a command from controller181or an external device networked to the PBF device100. In various embodiments, controller181acts a print controller for providing instructions to the 3-D printer to fuse or print specific parts with designated geometries, and to govern the dispensing and re-coat cycles, etc. In some embodiments, controller181may include one or more CPUs, dedicated hardware such as digital signal processors (DSPs) or field programmable gate arrays (FPGAs), and other dedicated digital and analog circuits. Controller181may further include memory, which may be cache memory or other storage. The memory may be read only memory, random access memory (RAM), static or dynamic RAM, flash memory, or any other appropriate storage unit or device. In various embodiments, the functions of controller181may be provided by an external device networked or otherwise coupled to PBF system100. Controller181may be in a central location, or in some embodiment, controller181may be a distributed controller with different locations in PBF system100, e.g., where the locations are relevant to the functions being performed at that location. In various embodiments, additional or different controllers may be used. Controller181may be used to manipulate the first structure(s)139and second structure(s)107of the build plate. In other embodiments, a separate controller or an external device may control the build plate, whether in a powder swap during a 3-D print or in a rapid powder removal procedure following the print. In various embodiments, controller181may control the energy beam source103and deflector105during the print cycle (FIG.1D).

As shown inFIG.1C, the build plate includes a frame160which is ordinarily part of the second structure107and which in this embodiment connects the second structure107together. The structures having the repeating vertical line pattern represent portions of the frame160of the second structure. While the portions of the frame do not look integrated together inFIG.1C, it should be clarified that the view of the build plate is a cross section taken from line AA ofFIGS.1A and1B. Thus, the frame160is actually part of a single second structure107in this embodiment.

The lower portion of the build plate includes first structure139. First structure includes protrusions177that extend upward into the apertures156arranged in the second structure107of the build plate, as was shown inFIG.1B. In this configuration, the apertures156are closed in that they are filled by the protrusions177of the first structure, and the build plate is acting as a support plate for the powder bed121as per usual operation.FIG.1Calso shows the interface182of the powder at the bottom of the build plate where the powder meets one of the upper protrusions177.FIG.1Calso shows the interface183between the first and second structures. During the print cycle (FIG.1D), these interfaces remain snugly secure and the upper protrusions177keep the apertures156closed unless and until a powder swap command is issued by controller181or by another appropriate mechanism.

FIG.1Calso shows a cross-sectional representation of the powder flow channels191, which can also be seen inFIG.1A. InFIG.1C, the powder flow channels191are shown as closed because an upper end of the channels is blocked by second structure107. However, as described below (FIG.1D), the piston179can move the first structure downward (and in some embodiments, piston179can rotate) to open the powder flow channels and the apertures156such that powder can be rapidly removed into an excess powder flow chamber164, which may also be referred to as a receiving cavity190. The excess powder flow chamber164or receiving cavity190can store the dispensed powder171, for example. During a powder reswap, while receiving cavity190captures the falling powder, the second hopper142may be aligned to dispense uniformly cooled (or heated) new powder via the powder dispenser. In various embodiments, large amounts of powder can be ejected at once from the powder dispenser133and used to fill the powder bed121rapidly for providing new powder around a build piece without having to perform a separate re-coat for each layer.

At the end of a print job, it may be desirable to rapidly remove the powder in the powder bed, as described herein. Thus, while the piston179operates to move the second structure such that the powder can fall into the receiving cavity190, the second structure107can continue to support the build piece109to prevent the build piece from falling through the apertures156. The size of the build piece109should as a result be designed to be comparatively larger than the apertures156in the second structure139to ensure that the apertures are small enough to prevent the build piece(s) from moving during the powder removal.

FIG.1Dis a front sectional view of a 3-D printer selectively fusing a layer of a build piece in accordance with an embodiment. That is,FIG.1Dshows the print cycle that follows the powder dispensing and re-coat cycles shown inFIG.1C. Re-coater182and the depositor115are shown as re-positioned on the left side of the PBF system100to avoid interference with the print cycle. During the print cycle, the energy beam source103may receive instructions from controller181to selectively melt the powder in the top layer. The melted powder cools and solidifies. In the example shown, the energy beam source provides an energy beam127to a deflector105. Where the energy beam127is a laser, the deflector105may be used to direct the energy beam127onto a desired part of the powder bed to fuse the correct portions of the layer.

InFIG.1D, only the frame of build plate107is visible, since the build plate107is acting as one uniform support plate during the print cycle. In addition to the separation of the first and second structures during a rapid powder removal, build plate107can also be instructed to move down in an amount equal to a layer for each print cycle in order to keep the energy beam source103at a generally constant distance from the surface of the powder bed121.

After the fusing is complete, the energy beam source103may switch to an “off” or an “idle” position, and the depleted depositor115is then in a position to receive an additional dose of powder from hopper141in a next dispensing cycle and in preparation for a subsequent re-coat cycle.

FIG.1Eis a front sectional view of a 3-D printer including a build plate having a first structure that moves downward relative to a second structure for allowing the rapid removal of powder from the print chamber while the second structure maintains support for the build piece, in accordance with various embodiments. For example, in the embodiment shown inFIG.1E, the PBF system100may have completed the print job. In order to rapidly remove the powder from the powder bed121and avoid excessive exposure of the build piece to the undesirable thermal gradients produced by the powder's trapped heat, the piston179may quickly lower the first structure139, e.g., with the assistance of the vertical rollers161. The downward and circular arrows displayed adjacent piston179show that the piston179can flexibly move the first structure139both downward and in a rotating direction (if necessary) to facilitate the powder flow.FIG.1Eshows the rapid powder flow through apertures156of the second structure and through the powder flow channels191of the first structure (which are now open by virtue of the first and second structures separating) and ultimately into the excess powder flow chamber164. The dispensed powder171is shown as building up at the bottom of excess powder flow chamber164. In other embodiments, the falling powder is directly routed to another storage device that is removable from the PBF system100. During this time, build piece109remains stable on the second structure107.

After the chamber113is depleted of powder inFIG.1E, the build piece109can, after any unrelated post-processing steps, be expediently removed from the PBF system100. The first and second structures can thereafter recombine and close in preparation for a new print job. In some embodiments, one or more ultrasonic transducers can be used to further drive small powder particles off of ledges, etc. of one of the first or second structures to ensure that all power is removed from the build plate and that the build plates are clean and ready to recombine.

FIG.2is a perspective view of an exemplary build plate including a build piece supported on the build plate by support structures that extend from a frame of the build plate to the build piece, in accordance with various embodiments. In various embodiments, support structures may be needed to support excess angles that portions of the build piece209may make with the build plate (e.g., more than 45 degrees). Portions of build piece209are shown as transparent in the figure in order to allow a better view of the build plate. The support structures can be fabricated in a step prior to the actual print. In some embodiments, the support structures themselves may be 3-D printed; in other embodiments, the support structures may be manually made or machined, or provided as commercial off the shelf (COTS) parts that have been cut, bent or cured as appropriate, and manually or automatedly inserted into the powder bed, in some cases using adhesives.

FIG.2shows a build plate which also includes a second structure207. The second structure207is defined by a frame260that includes eight rectangular apertures271. The build plate further includes a plurality of first structures239that are designed to fit into respective apertures271and snugly support the combination of build piece, support structures, and loose powder during a print job. The build piece209in this embodiment includes four support structures256for supporting a middle portion of the build piece209, and four additional support structures258for supporting a posterior of the build piece209. In this embodiment, the second structure is configured to remain immobile relative to the build piece209. Accordingly, it is important in this embodiment that the support structures are connected to the second structure207, and not the first structures239, of the build plate. This is because, during rapid powder removal at the end of a print job or powder exchange, the second structures239are configured to lower (and in some embodiments, bend or rotate) to enable channels to provide essentially unimpeded powder flow out of the build chamber. After the rapid powder removal, technicians or automated constructors (e.g., robots) can simply remove the support structures256,258and the build piece209from the chamber for future use.

InFIG.2, it should be noted that first structures239may use distinct embodiments from those used inFIGS.1C and1D, for example. In various embodiments, each of the first structures239may each be separately connected to a member that is individually configured to move the single first structure239to which the member is connected, with other individual members being similarly configured to move the other individual first structures239independently from one another using distinct connections. In other embodiments, the first structures239may be coupled together, e.g., via an array of crossbars underneath the build plate, such that all the first structures can move in and out of the second structure207at one time as needed for rapid powder removal. In other configurations, the first structures may rely on gravity or may be suspended using special springs or other devices to facilitate their separation from the second structure207. In short, a number of different embodiments may be contemplated for segregating components of a 3-D printed build plate to effect the rapid powder removal and/or powder exchange described herein.

FIG.3is a front sectional view of portions of a 3-D printer including a build plate showing a first structure thereof in closed, partway open, and fully open configurations, and powder flowing into an insulated receiving cavity.FIG.3shows different configurations for convenience and simplicity. However, in various embodiments, all of the first structures may open and close at once in order to provide a uniform removal of powder.

FIG.3shows a PBF system100in accordance with another embodiment. PBF system100includes a chamber313defined by a build plate (the build plate having first structures365, including365(1),365(2) and365(3), and second structures370(1) and370), and powder bed receptacle walls112). For illustrative purposes, the 3-D printer is at the end of the print job and is undergoing powder removal. A powder bed originally filled with powder303is being drained through the build plate. The powder flow382continues into a separate receiving cavity390that is at least partly thermally insulated from the chamber313by insulator378. With the presence of insulator378, the deleterious effects of the heat trapped in the powder of the receiving cavity390and flowing into the chamber313are mitigated. In some embodiments wherein a powder exchange is occurring in the middle of a print job, the insulator can also keep new cool powder that enters the chamber313from powder dispenser326insulated from the warm powder329that has entered receiving cavity390.FIG.3also includes vertical rollers161that serve to facilitate lowering the build plate in a layer-by-layer fashion during print operation, and segregating the first and second structures from each other during a power removal operation.

FIG.3also shows a sectional view of another exemplary embodiment of the build plate. Referring to the left side of the build plate ofFIG.3, second structure370(1) is shown on the far left of the build plate. A number of identical second structures370are positioned to the right of second structure370(1). In some embodiments, second structure370(1) and the remaining second structures370are all part of the same structure (but they are connected out of the plane of the sectional view ofFIG.3). In other embodiments, the second structures are independently controlled.

Between each of these second structures370is an aperture, which may be either closed, partway open, or fully open. For example, immediately to the right of second structure370(1) is an aperture in which first structure365(1) is in a closed position. First structure365(1) includes a horizontal member and a vertical member. The horizontal member fills the aperture between second structure370(1) and the second structure370to the right of second structure370(1). The vertical member of first structure365(1) is adjacent a bi-directional arrow labelled “a”. The arrow “a” is intended to mean that the vertical segment of the first structure365can be moved downward to open the aperture between associated second structures370(1) and370, or alternatively, the vertical segment can be moved upward to close the aperture, as the aperture is currently shown.

FIG.3also shows another closed first structure365(1) that likewise has a horizontal member closing the aperture and a vertical member adjacent the bidirectional arrow “b”. The arrow “b” has the same meaning as “a”.

The next three first structures365(2), having respective vertical members defined by unidirectional arrows “c”, “d”, and “e”, are partway open. Each of arrows “c”, “d”, and “e” adjacent the first structures365(2) demonstrate that the first structures365(2) are all opening, and powder303is beginning to flow through the adjacent second structures, but that second structures365(2) are not fully opened.

The remaining two first structures365(3) are fully open. As shown by the two arrows, the first structures365(3) have been moved downward (as in the partway open first structures365(2), but in addition, the first structures have also been fully rotated to the right. As a consequence the first structures365(3) are fully open and powder303is flowing unhindered through those apertures into powder flow area381and then into receiving cavity via powder flow382.

The different modes of the build plate ofFIG.3(closed, partway open, and fully open) were shown primarily for illustrative purposes to demonstrate an example of how the control circuit362may open and close the various structures in preparation for powder removal or exchange. In some embodiments, however, it may be beneficial to open some while keeping others closed (e.g., to avoid an avalanche of powder from all dispersing at once, if necessary). However, aside from these types of examples, it should be noted that in various embodiments, first structures365(1), (2) and (3) can open and shut simultaneously, depending on whether a powder removal or exchange procedure is underway. If a regular print job is occurring, the first and second structures365,370all form a single integrated build plate. When a rapid powder removal occurs after a print job, build piece309remains supported and held in place by second structures370while all of the first structures can fully open, and the powder303can then pour through the newly vacated apertures at a maximum rate to accomplish powder removal as quickly as possible.

In some embodiments, a vacuum, or a negative pressure, pump388is provided for removing the warm powder from the receiving cavity390. This process can occur concurrently with the next print job, and therefore does not reduce post-processing times.

FIG.4is front sectional view of an exemplary 3-D printer in which the build piece is supported by the powder itself, in accordance with an embodiment. The PBF system100is shown without the energy source and various other components for simplicity. In the embodiment ofFIG.4, the build piece is constructed so as to enable the supporting material itself to stabilize it. Thus, for example, a powder-filled gap411may exist below the build piece109. The powder may be densely packed in anticipation of this scenario. In some embodiments, the viscosity or other parameters of the print material may be adjusted such that the build piece109can be adequately supported by the material. For example, if the powder is thick and heavy, it may provide a sufficient base for an energy source to fuse the powder into a structure (e.g., build piece109) that is over a gap411of the same supporting powder. The structure may then be built within the powder bed, using the powder as a support rather than the build plate per se. Various similar embodiments of this configuration may exist such as, for example, where a small portion of build piece109is in contact with the build plate109, the latter of which may otherwise be supported by the powder.

In the embodiment ofFIG.4, rapid powder removal would mean that the powder may flow through first structures (omitted for clarity) that were removed from apertures in the second structure(s) to enable rapid powder removal, as before. In these embodiments, however, the second structure(s) may also act as a safeguard for preventing build piece109from breaching the build plate, for the same or similar reasons as in earlier embodiments. For instance, the second structure(s) may be a primary structure that is substantially larger than the first structure(s). Thus, build piece109can be protected from falling with the rest of the powder. In other embodiments where a powder exchange takes place, a second phase may occur after the powder removal in which first structures are reconnected to the second structure and a hopper that is heated (or cooled, depending on the desired properties of the build piece109) may rapidly dispense powder directly into the powder bed in chamber113.

Rapid powder removal/exchange as described herein may be facilitated by different embodiments. For example, the first and second structures may have specific geometric features and other properties.FIG.5is a perspective view of exemplary first structures for use in a build plate, in accordance with various embodiments. First structures539aand539bare shown, although in a practical application, any number of combined first structures may be used, including entire array of first structures used to maximize the speed of powder removal. Each structure539a-bmay be elliptical or circular in shape, or may use another geometry. Each structure539a-bmay be coupled to two or more neighboring structures via an element such as a control bar541. In some embodiments, control bar541may be automatedly movable by a motor or other powered device to bring the first structures539into the various open, closed and intermediate modes as necessary (see, e.g.,FIG.3). Each structure539a-bmay include a post540that stems up from the control bar541. Like the control bar541, the post may in some embodiments have further degrees of freedom. For example, post540may be rotatable and/or movable in the vertical or horizontal directions to rotatably connect to an open aperture on a second structure (not shown) in one embodiment, and to rotatably move while concurrently moving downward in order to disengage the first structure539bfrom the second structure during a powder removal. In some embodiments, the control bar541need not be present, and each first structure539a-b, etc. may be associated with its own post540responsible for adjusting it in the various configurations. In some embodiments, post540may be arranged telescopically to extend and retract the first structure539bas needed. In other embodiments, post540may extend and retract from a base device in a cavity of the PBF system100located underneath the build plate. In various embodiments, the crossbar541may be connected in array style to a corresponding array of first structures in order to help ensure that the motion of the array of first structures in and out of the apertures in the second structure is coordinated and concurrent. In short, the first structures may be controlled using a number of embodiments. In various embodiments, third and fourth structures, etc. may be used as necessary, e.g., where a build plate having a geometric priority of motion is needed. In this latter set of embodiments, different structures may be engaged and disengaged from the second structure, causing powder removal to occur in greater quantities in certain locations and less so in other locations. This type of action may be militated by any number of design-specific objectives, such as the number of build pieces intended to be simultaneously rendered in one print job, the need for a specific structure to be removed of high temperature powder before lower priority structures, and the like.

In various embodiments, posts540and/or first structures539can be made of a shape memory alloy that can change shape based on temperature. For example, in some 3D printing processes, the build plate can be heated to and maintained at a temperature of 100-200 degrees C. during printing. Posts540and/or first structures539can be made of shape metal alloy that, at the heated temperature, takes a shape in which first structures539prevent powder from flowing through an aperture in the build plate. This can prevent powder removal during the printing, i.e., when the build plate is heated. The shape of posts540and/or first structures539can change when the build plate is cooled, e.g., after printing is completed, such that the powder is allowed to flow through the apertures. For example, the edges of first structures539may curl downwards at cooler temperatures and/or posts540may bend to create an opening between first structures539and the apertures. Cooling of the build plate may occur unaided after the printing, or cooling may be aided, for example, by a cooling circuit or device associated with the 3D printer. In various embodiments, the shape of the shape metal alloy in the heated state might not cause first structures to be perfectly flush with the tops of the apertures (i.e., the surface of the build plate). In this case, the dosing of powder for the first layer may be adjusted to account for the fact the first structures are not flush. For example, if the first structures are slightly below the tops of the apertures, the dosing can be increased to fill in the extra space.

FIG.6is a perspective view of a frame constituting a second structure in which the first structures ofFIG.5may be implemented for rapid powder removal.FIG.6is the type of frame that may be used, for example, in combination with an array or grid-like assembly of first structures. In some embodiments, the first structures may be rotatably connected with internal edges of the corresponding array of apertures656. The first structures ofFIG.6may in various embodiments be sealed with corresponding edges of the apertures656. In some cases a special rubber may be used to effect a temporary seal. In other embodiments, one of the apertures and the edges of the first structures may include ridges, and the other of the apertures and edges may include contoured shapes that fit into the respective ridges to form a seal, similar in some respects to how a cap fits on a bottle. The second structure607is part of a frame660that can provide support to a build piece for rapid powder removal. It is also noteworthy that the frame has enough area on it to enable a PBF system to fuse build pieces, at least in part, to its surface. Some build pieces may be big enough so as to actually obstruct the flow of powder during a powder removal. However, the larger array of first structures should have more than enough apertures that can accommodate the powder removal even if a few apertures are blocked by the sheer size of the build piece. This is one of several benefits of using a build piece with a plurality of first structures and/or second structures. In some embodiments, zones of powder removal may be established where a first powered apparatus is configured to open or separate first structures from second structures and enable a first powder flow across a first portion of a build plate, a second apparatus is configured to open third structures from fourth structures and enable a second powder flow across a second portion of the build plate, and so on. In many embodiments, however, it may be desirable to dump all powder at one time, in which case the build plate may be configured to open and separate all in one small span of time.

FIG.7is a block diagram of an illustration of elements for providing mechanical power to enable relative motion of structures in a build plate for effecting powder removal. Initially it should be noted that one or more CPUs722may be local to the areas adjacent the build plate. In some embodiments, each of the CPUs722may receive wiring from the controller181and may receive powder removal instructions, instructions to reconfigure the build plate, and the like. In some embodiments, CPUs722are not needed as controller181or other circuitry (such as a workstation networked to the PBF system) may provide instructions directly to the components that control the build plate. In other embodiments, the build plate region may house one central CPU722or controller for controlling the movement of the entire build plate and/or its constituent first and second structures during a powder removal or exchange. In any embodiment where CPUs722are present, the term “CPU” is intended to encompass any electronic circuit capable of issuing instructions to or otherwise controlling the actions of actuators, motors, shafts, and other devices for controlling mechanical motion. Thus, CPUs722may constitute a processor with a plurality of cores. CPUs722may include a controller or a dedicated logical circuit, for example which can be physically wired to the subsystems that it is intended to control. Where CPU/controller722is a processor, it may be a generic processor or a special purpose processor, running a general code set or a specialized set of instructions. Build preparation software or other code can be used in various implementations to account for the positioning of the build piece relative to the part apertures, channels, build plate edges, etc., to ensure that the positioning of the build piece or the support structures is secure, and does not interfere with the operation of the configurable build plate.

If needed, additional components, such as logic circuitry, capacitors, inductors, transistors, diodes, etc., may be included on a printed circuit board, with appropriate backup circuits and fuses to create redundancies and avoid acting as a bottleneck during the powder removal process. CPU722may be in some embodiments more akin to a hardware switch that provides one or a few different indications to its components to engage or to disengage, for example. In some embodiments, CPU722represents a processor or plurality thereof that are coupled to controller181as shown in order to work in concert with the rest of the PBF system as it moves through its various cycles of operation. A clock may be used to provide precise timing, such as with an on-board crystal oscillator. In some embodiments, CPU722may be acting through a network, in which case a network transceiver may also be present, as well as one or more antennae in the case of a wireless network.

A battery or power source718may be needed to provide power to the various circuits and/or to provide a sufficient source of mechanical power to the components that drive the build plate structures. In various embodiments, the source of energy is provided from a socket, and a proportion of that current flows to the other components inFIG.7. These components may be one or more actuators726, or components of a machine responsible for moving and controlling parts of a system, such as by moving the first structures downward and out of their connections. The actuators726can perform this task by receiving an appropriate authorization signal from CPU722and, using the energy supplied it via the power source718, can move or turn the structures in one or more directions. An array of actuators may be provided to accommodate movement in different directions. Similarly, one or more motors728may accomplish a similar task, by controlling certain structures of the build plate, and e.g., by locking the build plate in place after a powder removal has completed. In various embodiments, one or more shafts730may be used, for example, to provide torque. In a case where first structures are rotatably coupled to edges of apertures in the second structures, the shafts730may be used to twist a connector bar or set thereof coupled to the first structures and thereby open the first structures by rotatably releasing them. The structures may thereupon be moved downward by a motor728or other component.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these exemplary embodiments presented throughout this disclosure will be readily apparent to those skilled in the art. Thus, the claims are not intended to be limited to the exemplary embodiments presented throughout the disclosure, but are to be accorded the full scope consistent with the language claims. All structural and functional equivalents to the elements of the exemplary embodiments described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112(f), or analogous law in applicable jurisdictions, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”