具体实施方式：
[0070]A description of example embodiments follows.
[0071]In a binder jetting process, a thin layer of powder (e.g., 50 μm) is spread onto a powder bed, followed by deposition of a liquid binder in a two-dimensional (2D) pattern or image that represents a single “slice” of a three-dimensional (3D) shape. After deposition of the liquid binder, another layer of powder is spread, and the process is repeated to form the 3D shape of bound powder material inside the powder bed. Powder spreading may be accomplished by means of a dispensing apparatus that deposits a pile of powder onto the powder bed. The pile of powder may then be spread, rolled, smoothed, or compacted by means of a spreading mechanism, such as a counter-rotating roller, doctor blade, or other means for spreading. After printing, the bound part is removed from the excess unbound powder, and sintered at high temperature to bind the particles together. Sintering may be performed to densify the part to full density (i.e., removal of all void space) or may be performed to bond the particles only lightly without substantial removal of void space.
[0072]During the process of spreading a new layer of powder onto the powder bed, the spreading mechanism can apply a shear force, also referred to interchangeably herein as a shearing force, that can cause defects in one or more previously printed layers. These defects can include: “shifting” (i.e., translation of layers in the powder bed); and “cracking” (i.e., breakup of the layers). Such defects may be referred to collectively herein as “smearing,”“shifting,” or “cracking,” but all generally refer to the “smeared” or “shifted” layers of a printed part. An example embodiment disclosed herein prevents such layer “shifting,”“smearing,” and “cracking” of layers of printed parts by means of immobilizing the layers during printing by printing a sacrificial component, also referred to interchangeably herein as a “raft,” under one or more portions of the part being printed. As such, a method may reduce layer shifting and smearing during 3D printing by means of sacrificial printed raft(s).
[0073]FIG. 1A is a block diagram of an example embodiment of a sacrificial component 24 and a part 10 within a powder bed 20. The sacrificial component 24 is printed using a three-dimensional (3D) printing system (not shown), such as the 3D printing system 250 of FIG. 2A, disclosed further below, or any other suitable 3D printing system that includes (i) a spreading mechanism 15 for spreading unbound powder 4 to form layers of a powder bed 20, such as the layer 35 of the powder bed 20, and (ii) a printing mechanism 19 for jetting binder fluid 22 into the unbound powder 4 to form the sacrificial component 24. Jetting the binder fluid 22 into the unbound powder 4 produces the bound powder 33. Regions of the bound powder 33 may be referred to as “printed” regions. The sacrificial component 24 is formed with a feature (not shown) that provides a resistive force (not shown) to a shear force 12 imposed by the spreading mechanism 15 during the spreading. The resistive force may be represented as one or more vector arrows (not shown) that are equal and opposite to vector arrows of the shear force 12. The part 10 is printed with the 3D printing system in a coupled arrangement 26 with the sacrificial component 24. The coupled arrangement 26 in combination with the resistive force is sufficient to immobilize each printed layer of the part 10 in the powder bed 20 to resist the shear force 12 imposed by the spreading mechanism 15 during spreading of the unbound powder 4 above each printed layer of the part 10.
[0074]According to an example embodiment, at least a portion of the unbound powder 4 provides the resistive force. The part 10 and the sacrificial component 24 may be coupled in the coupled arrangement 26 via a mechanical coupling 5. The mechanical coupling 5 may be a direct or indirect mechanical coupling. For example, the mechanical coupling 5 may be a direct mechanical coupling formed by at least a portion of the part 10 being bound directly to the sacrificial component 24 or by at least of portion of the part 10 and the sacrificial component 24 each being bound to a printed structure interposed therebetween, such as the lattice structure 1121 of FIG. 11A, disclosed below, or any other suitable printed structure. The part 10 and the sacrificial component may be printed as a single printed part in the coupled arrangement 26. According to an example embodiment, the part 10 and the sacrificial component 24 may be printed in a coupled arrangement 26 with a mechanical coupling 5 that is an indirect mechanical coupling, for example, the indirect mechanical coupling may be formed of unbound powder 4.
[0075]The feature of the sacrificial component 24 may be a given number of printed layers, an inverse geometric feature that complements a geometric feature of the part, or a combination thereof. Example embodiments of the feature are disclosed, further below.
[0076]FIG. 1B is a block diagram of another example embodiment of a sacrificial component 124 and a part 110 within a powder bed 120. The sacrificial component 124 and the part 110 may be printed by a 3D printing system (not shown) in a coupled arrangement, as disclosed above. In the example embodiment of FIG. 1B, at least a portion of the part 110 is printed above the sacrificial component 124 and is coupled to the sacrificial component 124 via a direct mechanical coupling 105 as the printed layer 108a of the part is bound to at least a portion of the printed layer 102e of the sacrificial component 124. In the example embodiment of FIG. 1B, the sacrificial component 124 is formed with a feature that provides a resistive force (not shown) to a shear force 112 imposed by spreading of the unbound powder 104 by the spreading mechanism 115. In the example embodiment, the feature of the sacrificial component 124 includes a given number of printed layers, that is, five, in the example embodiment, namely, the printed layers 102a-e that are located below the mechanical coupling 105.
[0077]The sacrificial component 124 and the part 110 reside within a powder bed 120. Printing of the sacrificial component 124 and the part 110 includes jetting binder fluid (not shown) into layers of the unbound powder 104 of the powder bed 120 spread by the spreading mechanism 115 on a layer-by-layer basis, such as disclosed below with reference to FIG. 2A.
[0078]In the example embodiment of FIG. 1B, printing of the sacrificial component 124 includes jetting binder fluid into the powder layers 106b, 106c, 106d, 106e, and 106f, while printing of the part 110 includes jetting binder fluid into the powder layers 106g, 106h, and 106i, of the plurality of powder layers 106a-j that are spread by the spreading mechanism 115, yielding the printed layers 102a-e of the sacrificial component and the printed layers 108a-c of the part 110.
[0079]According to the example embodiment, the coupled arrangement of the part 110 and the sacrificial component 124 in combination with the resistive force of the feature, that is, the given number of layers of the sacrificial component 124, is sufficient to immobilize each printed layer of the part 110, that is, the printed layers 108a-c, to resist the shear force 112 imposed by the spreading mechanism 115 during spreading of the unbound powder 104 at powder layers 106h, 106i, and 106j, each above a printed layer of the part 110. It should be understood that the powder layers 106b-f include the printed layers 102a-e and that the printed layers 102a-e reflect portions of their respective powder layers 106b-f that have binder fluid applied thereto. Further, the powder layers 106g-i include the printed layers 108a-c and the printed layers 108a-c reflect portions of their respective powder layers 106g-i that have binder fluid applied thereto. The shear force 112 is imposed by physical interaction of the spreading mechanism 115 with the powder layers 106b-j. After printing, and before or after post-processing, the part 110 is separated from the sacrificial component 124. Following decoupling from the part 110, the sacrificial component 124 may be disposed of, having served to ensure quality of the part 110 (e.g., preventing smearing of the part 110) during the printing process.
[0080]As illustrated in FIG. 1B, the printed layers 102a-e of the sacrificial component 124 experience shifting, relative to a respective original printed location 107, due to the shear force 112. Because the sacrificial component 124 already absorbed effects of the shear force 112 and because the part 110 is printed in a coupled arrangement with the sacrificial component 124, the printed layers 108a-c of the part 110 resist the shear force 112 and, thus, do not experience shifting. In the example embodiment, the given number of layers of the sacrificial component 124 is five; however, the given number may be any suitable number that enables printed layer(s) of the part 110 to resist the shear force 112 caused by the spreading mechanism 115. Further, it should be understood that the part 110 may have any suitable shape or number of printed layers to form a target 3D part. In addition, while FIG. 1B discloses spreading of the powder layer 106j, it should be understood that such spreading is shown for illustrative purposes to show the shear force 112 and that a powder layer may not be spread over the part 110 following printing of the part 110.
[0081]FIG. 2A is a block diagram of an example embodiment of an additive manufacturing system 250. The additive manufacturing system 250 comprises a spreading mechanism 215, printing mechanism 219, and controller 230. The controller 230 is configured to (i) drive the spreading mechanism 215 to spread unbound powder 204 to form layers of a powder bed 220 and (ii) drive the printing mechanism 219 to jet binder fluid 222 into the unbound powder 204 to print a sacrificial component 224 and a part 210. The controller 230 is further configured to drive the printing mechanism 219 to form the sacrificial component 224 with a feature that provides a resistive force to a shear force 212 imposed by the spreading mechanism 215 during the spreading and print the part 210 in a coupled arrangement 226 with the sacrificial component 224. The coupled arrangement 226 in combination with the resistive force is sufficient to immobilize each printed layer of the part 210 in the powder bed 220 to resist the shear force 212 imposed by the spreading mechanism 215 during spreading of the unbound powder 204 above each printed layer of the part 210.
[0082]The feature of the sacrificial component 224 may be a given number of printed layers, an inverse geometric feature that complements a geometric feature of the part 210, or a combination thereof. It should be appreciated that any one or more methods described with respect to the formation of a given layer of the part 210 or sacrificial component 224 may be repeated as necessary to form a respective plurality of layers making up the part 210 or sacrificial component 224. The sacrificial component 224 and the part 210 are three-dimensional (3D) objects. The unbound powder 204 may include, without limitation, metallic particles, ceramic particles, polymeric particles, and combinations thereof. The additive manufacturing system may further comprise a sintering mechanism (not shown). The part 210, sacrificial component 224, or a combination thereof, may be subsequently processed (e.g., sintered) by the sintering mechanism (not shown) to form a finished part that is separate from the sacrificial component 224. In addition to sintering, other processing of the part 210 may be performed to form the finished part.
[0083]The additive manufacturing system 250 may further comprise a powder supply 217, print box 214, and nozzle 218. The print box 214 includes a build platform 213, such as a piston, that is moveable within the print box 214. The print box 214 may have any suitable shape and includes walls which, in combination with a top surface of the build platform 213, contains the powder bed 220 which is formed by spreading layers of the unbound powder 204 above the build platform 213. The powder supply 217 is a dispensing apparatus that deposits a pile of the unbound powder 204 onto the powder bed 220. According to the example embodiment, the dispensing apparatus is a hopper with an opening from which the unbound powder 204 flows to deposit the pile of unbound powder 204. The pile of unbound powder 204 may then be spread, rolled, smoothed, or compacted by means of the spreading mechanism 215, such as a counter-rotating roller, doctor blade, or other means for spreading.
[0084]The build platform 213 is configured to move downward within the print box 214 following spreading of a layer of the unbound powder 204 and, optionally, jetting the binder fluid 222 into same. The spreading mechanism 215 is moveable along the print box 214 to spread successive layers of the unbound powder 204 across the powder bed 220. The powder bed 220 may have a maximum number of layers defined by the print box 214.
[0085]The nozzle 218 and the printing mechanism 219 may be movable (e.g., in coordination with one another and, optionally, in coordination with movement of the spreading mechanism 215) across the powder bed 220 to form a plurality of layers and, ultimately, to form the sacrificial component 224 and the part 210. The spreading mechanism 215, nozzle 218, and printing mechanism 219 may be movable over the print box 214. It should be understood that any manner and form of relative movement of components of the additive manufacturing system 250 may be used to carry out any one or more of the binder jetting processes described herein. Thus, for example, the print box 214 may be, further or instead, movable with respect to one or more of the spreading mechanism 215, nozzle 218, and printing mechanism 219 to achieve relative movement of components, as necessary to carry out any one or more of the binder jetting processes described herein.
[0086]The spreading mechanism 215 may generally span at least one dimension of the powder bed 220 such that the spreading mechanism 215 may distribute a layer of the unbound powder 204 on top of the powder bed 220 in a single pass. As an example, the spreading mechanism 215 may include a roller rotatable about an axis perpendicular to an axis of movement of the spreading mechanism 215 across the print box 214.
[0087]The roller may be, for example, substantially cylindrical. In use, rotation of the roller about the axis perpendicular to the axis of movement of the spreading mechanism 215 may spread the unbound powder 204 that flows from the powder supply 217 to the print box 214 to form a layer of the unbound powder 204 of the powder bed 220. It should be appreciated, therefore, that the plurality of sequential layers of the unbound powder 204 of the powder bed 220 may be formed through repeated movement of the spreading mechanism 215 across the powder bed 220. The thickness of each layer of the unbound powder 204 may be substantially uniform and, in particular, may be about 50 microns. Other dimensions are additionally or alternatively possible.
[0088]The printing mechanism 219 may direct binder fluid into the powder bed 220 as the printing mechanism 219 moves across the powder bed 220. While the printing mechanism 219 may be illustrated as a single printhead, it should be appreciated that the printing mechanism 219 may, additionally or alternatively, include a plurality of printheads from which the binder fluid 222 may be jetted into the powder bed 220. Further, it should be understood that jetting of the binder fluid 222 into the unbound powder 204 of the powder bed may be jetted from any direction.
[0089]The controller 230 may be in electrical communication with the powder supply 217, build platform 213, print box 214, spreading mechanism 215, printing mechanism 219, and nozzle 218 to drive functionality of same. The controller 230 may include one or more processors 231 operable to control the powder supply 217, build platform 213, print box 214, spreading mechanism 215, printing mechanism 219, and nozzle 218, and combinations thereof.
[0090]The one or more processors 231 of the controller 230 may execute instructions to control movement of one or more of the powder supply 217, build platform 213, print box 214, spreading mechanism 215, printing mechanism 219, and nozzle 218 relative to one another as the sacrificial component 224 and the part 210 are being formed. For example, the one or more processors 231 of the controller 230 may execute instructions to move the powder supply 217 to direct the unbound powder 204 toward powder bed 220, move the spreading mechanism 215 to spread the unbound powder 204 across the powder bed, move the printing mechanism 219 to jet binder fluid into a layer of unbound powder of the powder bed, and to move the build platform 213 in a z-axis direction away from the spreading mechanism 215 to accept each new layer of the powder 204 along the top of the powder bed 220 as the spreading mechanism 215 moves across the powder bed 220. In general, the controlled movement of the build platform 213 is based on a thickness of a corresponding layer being formed in the powder bed 220.
[0091]Additionally, or alternatively, the one or more processors 231 of the controller 230 may execute instructions to control movement of the spreading mechanism 215 to spread successive layers of the unbound powder 204 across the powder bed 220. For example, the one or more processors 231 of the controller 230 may control speed of movement of the spreading mechanism 215 across the powder bed 220. As a further or alternative example, the controller 230 may control one or more features of the spreading mechanism 215 useful for packing the top layer of the powder bed 220 as the spreading mechanism 215 moves across the powder bed 220. Returning to the specific example of the spreading mechanism 215 being rotatable, the one or more processors 231 of the controller 230 may control rotation (e.g., speed, direction, or both) of the spreading mechanism 215.
[0092]The one or more processors 231 of the controller 230 may, further or instead, control the printing mechanism 219. For example, the one or more processors 231 of the controller 230 may control movement (e.g., speed, direction, timing, and combinations thereof) of the printing mechanism 219 across the powder bed 220 as well as jetting of the binder fluid 222 from the printing mechanism 219 into unbound powder of the powder bed 220. The one or more processors 231 may control the printing mechanism 219 to jet the binder fluid 222 into unbound powder of the powder bed 220 along a controlled two-dimensional pattern associated with a given layer. The controlled two-dimensional pattern may vary from layer-to-layer, as necessary, according to a component shape of sacrificial component 224 and a part shape of the part 210 being formed in the powder bed 220.
[0093]The additive manufacturing system 250 may further, or instead, include a non-transitory, computer readable storage medium 232 in communication with the controller 230 and having stored thereon a three-dimensional model(s) 234 and instructions for causing the one or more processors 231 to carry out any one or more of the methods described herein. In general, as a plurality of sequential layers of the powder unbound powder 204 are introduced to the powder bed 220, the sacrificial component 224 and the part 210 are formed according to the three-dimensional model(s) 234 stored in the non-transitory, computer readable storage medium 232. In certain implementations, the controller 230 may retrieve the three-dimensional model(s) 234 in response to user input, and generate machine-ready instructions for execution by the additive manufacturing system 250 to fabricate the sacrificial component 224 and the part 210.
[0094]In the example embodiment of FIG. 2A, at least a portion of the part 210 is printed above the sacrificial component 224 and is coupled to the sacrificial component 224 via a mechanical coupling 205 that may be an indirect or direct mechanical coupling, as disclosed herein. The controller 230 may be further configured to drive the printing mechanism 219 to print the at least a portion of the part above the sacrificial component 224.
[0095]According to an embodiment, the part 210 and the sacrificial component 224 may be coupled in the coupled arrangement 226 via an indirect mechanical coupling formed of the unbound powder 204. According to another embodiment, the part 210 and the sacrificial component 224 may be coupled in the coupled arrangement 226 via a direct mechanical coupling. For example, the controller 230 may be further configured to form the direct mechanical coupling by driving the spreading mechanism 215 to spread one or more layers of the unbound powder 204 and driving the printing mechanism 219 to jet the binder fluid 222 into same in a manner that creates a lattice connection, such as the lattice structure 1121 of FIG. 11A, disclosed further below, that may be created between the at least a portion of the part and the sacrificial component.
[0096]The controller 230 may be further configured to drive the printing mechanism 219 to print at least a portion of the part 210 above the sacrificial component. The part 210 and the sacrificial component 224 may be coupled in the coupled arrangement via a direct mechanical coupling formed of an anti-sintering agent (ASA), as disclosed further below with reference to FIG. 7B. The controller 230 may be further configured to drive the printing mechanism 219 to apply the ASA to a surface of the sacrificial component 224 to form a separation layer between the at least a portion of the part 210 and the sacrificial component 224 and drive the sintering mechanism (not shown) to sinter the coupled arrangement 226 to decouple the at least a portion of the part 210 from the sacrificial component 224.
[0097]According to an example embodiment, the controller 230 may be further configured to drive the printing mechanism 219 to print at least a portion of the part 210 above the sacrificial component 224 and the at least a portion of the part 210 may be the entire part.
[0098]According to an example embodiment, the controller 230 may be further configured to: drive the printing mechanism 219 to print the sacrificial component 224 with a component shape that extends laterally beyond a part shape of the part 210; print one or more layers of the sacrificial component 224 and the part 210 that extend the sacrificial component 224 and the part 210 vertically upward and alongside each other; or a combination thereof, such as disclosed below with reference to FIG. 8B and FIG. 8C.
[0099]According to an example embodiment, the controller 230 may be further configured to drive the printing mechanism 219 to create the sacrificial component 224 with one or more gaps of the unbound powder 204 to facilitate decoupling of the sacrificial component 224 from the part 210, such as disclosed further below with reference to FIG. 8D.
[0100]According to an example embodiment, the controller 230 may be further configured to drive the printing mechanism 219 to jet the binder fluid 222 into the unbound powder 204 in a manner that prints the sacrificial component 224 as a lattice structure, such as the lattice structure 224, disclosed further below with reference to FIG. 11A.
[0101]According to an example embodiment, the controller 230 may be further configured to drive the printing mechanism 219 to print the sacrificial component 224 as multiple sacrificial components each having a direct or indirect mechanical coupling with a respective sacrificial component-facing surface of the part, such as disclosed below with reference to FIG. 12.
[0102]According to an example embodiment, the part 210 may have a part shape and the controller 230 may be further configured to drive the printing mechanism 219 to print the sacrificial component 224 with a complementary shape relative to the part shape. The complementary shape may conform to a topography of the part shape at least sufficient enough to provide for the coupled arrangement.
[0103]According to an example embodiment, the controller 230 may be further configured execute instructions or interpret codes that were generated according to the 3D CAD model(s) 234 to drive the printing mechanism 219 to print the sacrificial component 224 and the part 210 in the coupled arrangement 226.
[0104]According to an example embodiment, the controller 230 may be further configured to drive the printing mechanism 219 to: print the sacrificial component 224 by jetting the binder fluid 222 at a first saturation level; and print the part 210 by jetting the binder fluid 222 at a second saturation level, wherein the first saturation level may be lower relative to the second saturation level, such as disclosed further below with reference to FIGS. 15A-D.
[0105]FIG. 2B is a block diagram of another example embodiment of an additive manufacturing system 2250. The example embodiment of the additive manufacturing system 2250 includes an alternative embodiment of the powder supply 217 relative to the example embodiment of the additive manufacturing system 250 of FIG. 2A, disclosed above.
[0106]According to the example embodiment, the print box 214 includes the powder supply 217 for depositing the pile of unbound powder 204. As in the example embodiment of FIG. 2A, disclosed above, the pile of unbound powder 204 may then be spread, rolled, smoothed, or compacted by means of the spreading mechanism 215, such as a counter-rotating roller, doctor blade, or other means for spreading.
[0107]According to the example embodiment of FIG. 2B, the spreading mechanism 215 may be movable from the powder supply 217 to the powder bed 220 and along the powder bed 220 to spread successive layers of the unbound powder 204 across the powder bed 220. As in the example embodiment of FIG. 2A, disclosed above, the nozzle 218 and the printing mechanism 219 may be movable (e.g., in coordination with one another and, optionally, in coordination with movement of the spreading mechanism 215) across the powder bed 220 to form a plurality of layers and, ultimately, to form the sacrificial component 224 and the part 210.
[0108]According to the example embodiment of FIG. 2B, the one or more processors 231 of the controller 230 may execute instructions to control z-axis movement of one or more of the powder supply 217 and the build platform 213 relative to one another as the sacrificial component 224 and the part 210 are being formed. For example, the one or more processors 231 of the controller 230 may execute instructions to move the powder supply 217 in a z-axis direction toward the spreading mechanism 215 to direct the unbound powder 204 toward the spreading mechanism 215 as each layer is formed and to move the build platform 213 in a z-axis direction away from the spreading mechanism 215 to accept each new layer of the unbound powder 204 along the top of the powder bed 220 as the spreading mechanism 215 moves across the powder bed 220. Movement of the powder supply 217 may be performed by driving movement of a powder supply platform 229. The powder supply platform may be any suitable moveable platform, such as a piston.
[0109]In general, the controlled movement of the build platform 213 relative to the powder supply 217 is based on a thickness of a corresponding layer being formed in the powder bed 220. Movement of the powder supply 217 may be upward via a powder supply platform Additionally, or alternatively, the one or more processors 231 of the controller 230 may execute instructions to control movement of the spreading mechanism 215 from the powder supply 217 to the powder bed 220 to spread successive layers of the unbound powder 204 across the powder bed 220.
[0110]FIG. 3 is a block diagram of an example embodiment of printing stages for printing a sacrificial component 324 and a part 310 in a coupled arrangement. In a first printing stage 321, a first printed layer 302a of the sacrificial component 324 is printed by jetting binder fluid into unbound powder of the powder bed layer 306b spread on top of the unbound powder of the powder bed layer 306a of a powder bed 320.
[0111]In a second printing stage 323, a next layer of unbound powder is spread across a current top surface of the powder bed 320, where the current top surface in the second printing stage 323 is the powder bed layer 306b that includes the printed layer 302a of the sacrificial component 324 and unbound powder. A spreading mechanism 315, such as a roller or any other suitable spreading mechanism, is used to spread the unbound powder of the powder bed layer 306c across the current top surface of the powder bed 320 and applies a shear force 312a during the spreading. In response to the shear force 312a, the printed layer 302a shifts 303 relative to its original printed location 307a. As such, the shear force 312a from the spreading mechanism 315 causes the previously printed layer, that is, the printed layer 302a of the sacrificial component 324, to shift relative to its original printed location 307a.
[0112]In a third printing stage 325, binder fluid is jetted into unbound powder of the powder bed layer 306c to form a next printed layer of the sacrificial component 324, that is, the printed layer 302b. The powder bed layer 306c includes the printed layer 302b of the sacrificial component 324 and unbound powder and becomes the current top surface layer of the powder bed 320.
[0113]In a fourth printing stage 327, additional layers of the sacrificial component 324 are printed, namely the printed layers 302c, 302d, and 302e, by spreading unbound powder to successively form the powder bed layers 306d, 306e, and 306f and jetting binder fluid into same. Following the printing of a given number of layers of the sacrificial component 324, that is, five in the example embodiment, a feature of the sacrificial component 324 is formed that provides a resistive force to the shear force imposed by the spreading mechanism 315 during spreading. Additional layers of unbound powder are spread to form additional powder bed layers of the powder bed 320, namely, the powder bed layers 306g, 306h, and 306i, and binder fluid is jetted into same to print the printed layers 308a, 308b, and 308c of the part 310.
[0114]As disclosed in FIG. 3, there is no shifting of the printed layers 308a, 308b, and 308c of the part 310, relative to an original printed location 307b, due to the shear force 312b imposed by the spreading mechanism 315 during spreading of unbound powder above such layers. Shifting due to the shear force 312b is limited to the five printed layers of the sacrificial component 324. The five printed layers of the sacrificial component 324 serve as an anchor for printed layers of the part 310 and form a feature of the sacrificial component 324 that provides a resistive force to the shear force imposed by the spreading mechanism during spreading of unbound powder. As disclosed in the example embodiment of FIG. 3, at least a portion of the part 310 is above the sacrificial component 324 in the coupled arrangement. In the example embodiment, the mechanical coupling 305 between the part 310 and the sacrificial component 324 is a direct mechanical coupling.
[0115]The five printed layers 306b-f of the sacrificial component 324 are lower in the powder bed relative to the printed layers 308a-c. The coupled arrangement of the part 310 and the sacrificial component 324 in combination with the resistive force provided by at least the given number of layers, that is, the five printed layers 306b-f of the sacrificial component 324, is sufficient to immobilize each printed layer of the part 310 in the powder bed 320, that is, the printed layers 308a-c, to resist the shear force 312b imposed by the spreading mechanism 315 during spreading of unbound powder above each printed layer of the part 310.
[0116]FIG. 4 is a flow diagram 401 of an example embodiment of an additive manufacturing method. The method begins (402) and prints a sacrificial component using a three-dimensional (3D) printing system including (i) a spreading mechanism for spreading unbound powder to form layers of a powder bed and (ii) a printing mechanism for jetting binder fluid into the unbound powder to form the sacrificial component with a feature that provides a resistive force to a shear f