WO2020072070A1

WO2020072070A1 - Edge adjustments for layers of build material

Info

Publication number: WO2020072070A1
Application number: PCT/US2018/054536
Authority: WO
Inventors: Andy Van Brocklin; Frank D. Derryberry
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2018-10-05
Filing date: 2018-10-05
Publication date: 2020-04-09

Abstract

In some examples, a system determines, based on a representation of an object to be formed by an additive manufacturing machine, locations in a layer of build material where a liquid agent is to be applied. As part of an edge adjustment at a greater control than a control provided by a dispensing assembly for the liquid agent, the system controls a location of an edge of the layer of build material relative to a location of the edge of the layer of build material specified by the representation of the object, the controlling of the location of the edge comprising adding a pattern of dry voxels in digital data representing locations of the layer of build material where the liquid agent is to be applied.

Description

EDGE ADJUSTMENTS FOR LAYERS OF BUILD MATERIAL

Background

[0001 ] Additive manufacturing machines produce three-dimensional (3D) objects by building up layers of material. A type of an additive manufacturing machine is referred to as a 3D printing system. Additive manufacturing machines are able to receive as input a computer aided design (CAD) model or other digital representation of a physical 3D object to be formed, and build, based on the CAD model, the physical 3D object. The model may be processed into layers by the additive manufacturing machine, and each layer defines a corresponding part (or parts) of the 3D object.

Brief Description of the Drawings

[0002] Some implementations of the present disclosure are described with respect to the following figures.

[0003] Fig. 1 is a block diagram of an additive manufacturing machine, according to some examples.

[0004] Fig. 2 is a top view of a layer of build material with dry voxel regions added according to some examples.

[0005] Fig. 3 is an expanded view of an area of the layer of build material of Fig. 2, to show dry voxel regions according to some examples.

[0006] Fig. 3A is an expanded view of the area of the layer of build material of Fig. 3, with the dry voxel regions filled in by a liquid agent that has flowed from the surrounding areas.

[0007] Fig. 4 is a top view of a layer of build material with dry voxel regions added according to alternative examples. [0008] Fig. 5 is an expanded view of an area of the layer of build material of Fig. 4.

[0009] Fig. 6 is a block diagram of a storage medium storing machine-readable instructions according to some examples.

[0010] Fig. 7 is a block diagram of an additive manufacturing machine according to further examples.

[0011 ] Fig. 8 is a flow diagram of a process according to some examples.

[0012] Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements. The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings provide examples and/or implementations consistent with the description; however, the description is not limited to the examples and/or implementations provided in the drawings.

Detailed Description

[0013] In the present disclosure, use of the term“a,”“an”, or“the” is intended to include the plural forms as well, unless the context clearly indicates otherwise. Also, the term“includes,”“including,”“comprises,”“comprising,”“have,” or“having” when used in this disclosure specifies the presence of the stated elements, but do not preclude the presence or addition of other elements.

[0014] An additive manufacturing machine such as a three-dimensional (3D) printing system can build 3D objects by forming successive layers of build material and processing each layer of build material on a build platform. In some examples, a build material can include a powdered build material that is composed of particles in the form of fine powder or granules. The powdered build material can include metal particles, plastic particles, polymer particles, ceramic particles, or particles of other powder-like materials. In some examples, a build material powder may be formed from, or may include, short fibers that may, for example, have been cut into short lengths from long strands or threads of material. [0015] In some examples, as part of the processing of each layer of build material, liquid agents can be dispensed (such as through a printhead or other agent dispensing assembly) to the layer of build material. Examples of agents include a fusing agent (which is a form of an energy absorbing agent) that absorbs the heat energy emitted from an energy source used in the additive manufacturing process. For example, after a layer of build material is deposited onto a build platform (or onto a previously formed layer of build material) in the additive manufacturing machine, a fusing agent with a target pattern can be deposited on the layer of build material.

The target pattern can be based on an object model (or more generally, a digital representation) of the physical 3D object that is to be built by the additive

manufacturing machine.

[0016] According to an example, a fusing agent may be an ink-type formulation including carbon black, such as, for example, the fusing agent formulation

commercially referred to as the V1 Q60A“HP fusing agent” available from HP Inc. In an example, a fusing agent may additionally include an infrared light absorber, a near infrared light absorber, a visible light absorber, or an ultraviolet (UV) light absorber. Fusing agents can also refer to a chemical binding agent, such as used in a 3D printing system that forms objects using a metal or other type of build material. In further examples, other types of additive manufacturing agents can be added to a layer of build material.

[0017] Following the application of the fusing or binding agent, an energy source (e.g., including a heating lamp or multiple heating lamps that emit(s) energy) is activated to sinter, melt, fuse, bind, or otherwise coalesce the powder of the layer of build material underneath the fusing or binding agent. The patterned build material layer (i.e. , portions of the layer on which the fusing or binding agent was deposited) can solidify, for example after cooling, and form a part, or a cross-section, of the physical 3D object.

[0018] Next, a new layer of powder is deposited on top of the previously formed layer, and the process is re-iterated in the next additive manufacturing cycle to form 3D parts in the successive layers of build material. The 3D parts collectively form a 3D object (or multiple 3D objects) that is the target of the build operation.

[0019] In other examples, an additive manufacturing machine can be used as part of a sintering process. In the sintering process, as each layer of build material is deposited, a binder (which is another type of liquid agent) is applied by a printhead or other agent dispensing assembly to the layer of build material. Portions of the build material where the binder is applied are bound together by the binder. The binder can include an ultraviolet-curable binder, heat-curable binder, and so forth. After the layers of build material have been deposited and the binder applied to locations of each layer of build material, curing of the binder produces a so-called “green part.” The green part is de-powdered to remove any unbound build material powder. Afterwards, the green part can be transferred to an oven, where the bound build material powder (e.g., metal particles, etc.) are sintered together to form a highly dense 3D object.

[0020] An agent dispensing assembly includes nozzles to dispense a liquid agent to a layer of build material. The spacing between the nozzles contributes to a resolution of the agent dispensing assembly (e.g., 1200 dots per inch or DPI, 2400 DPI, etc.). Resolution refers to the fineness of steps of the positions at which liquid agent deposition can occur. The resolution of the agent dispensing assembly can further be based on other factors, such as aerodynamic characteristics associated with the travel of liquid agent drops from the agent dispensing assembly to a layer of build material, the positioning of liquid agent drops that can vary due to misdirected nozzles or nozzles that eject liquid agent drops at less than a target force, and so forth.

[0021 ] The resolution of the agent dispensing assembly may not be sufficient to achieve a target edge profile. For example, an edge of a layer of build material formed by an additive manufacturing machine may not be straight or may not have some other target profile. However, it may not be possible with the resolution of the agent dispensing assembly to address the lower than desired spatial resolution and/or accuracy in the formation of the edge of the layer of build material. [0022] Additionally or alternatively, the agent dispensing assembly may not exhibit a target accuracy or precision in setting a location of the edge of the layer of build material. Accuracy refers to how closely the actual position of liquid agent deposition achieved relates to a target position of liquid agent deposition. Precision refers to a degree to which repeated depositions of the liquid agent will occur at the same locations under unchanged conditions of the additive manufacturing machine.

[0023] In accordance with some implementations of the present disclosure, an edge adjustment of an edge of a build material layer is performed based on a control of the location of the edge that is at a greater resolution, accuracy, and/or precision than edge location control achievable based on deposition of the liquid agent by an agent dispensing assembly.

[0024] As part of the edge adjustment with greater control than control

achievable with an agent dispensing assembly for the liquid agent, a location of an edge of the layer of build material is adjusted relative to a location of the edge of the layer of build material specified by a representation of an object to be formed by an additive manufacturing machine is performed. As used here,“control” of an edge adjustment can refer to control according to any or some combination of a resolution, an accuracy, or precision achievable by an additive manufacturing machine in setting the location of the edge.

[0025] The adjusting of the location of the edge includes adding a pattern of dry voxels in digital data (which can be referred to as“raster data,”“digital slice data,” “bitmap data,” etc.) representing locations of an individual layer of build material where the liquid agent is to be applied. Each dry voxel of the pattern of dry voxels defines a respective dry voxel region in the layer of build material that is without the liquid agent. The dry voxel region is able to receive a flow of a portion of the liquid agent applied to other locations of the layer of build material. A dry voxel region in the build material layer is distinguished from a wet voxel region in the build material layer, where the wet voxel region includes a region where the liquid agent is applied by the agent dispensing assembly 114. A wet voxel region is represented by a wet voxel in the digital data used to process a build material layer. [0026] As used here, an“edge” of a layer of build material can refer to either the outermost edge of the layer of build material, or to any boundary of any area (such as an inner area) within the layer of build material. The area of the layer of build material can be part of a portion that is less than the entirety of the layer of build material.

[0027] The formation of dry voxel regions based on an added pattern of dry voxels to digital slice data for an individual layer of build material allows for liquid flow modulation of the edge profile of the layer of build material (or more specifically, of a part of the layer of build material corresponding to the 3D part to be formed in the layer of build material). The liquid flow modulation using the dry voxel regions enables the location of the edge of the layer of build material to be adjusted with a greater control than possible using the nozzles of the agent dispensing assembly. The presence of the dry voxel regions is to reduce movement of the liquid agent to the edge of the build material layer.

[0028] It is noted that edge adjustment of a layer of build material can be performed in any or some combination of multiple dimensions (e.g., X, Y, and Z dimensions). The X and Y dimensions are the dimensions of a horizontal plane that is parallel to the layer of build material. The Z dimension defines a vertical axis that is perpendicular to the X and Y dimensions.

[0029] Fig. 1 shows an example arrangement of an additive manufacturing machine 100, which in some examples can include a 3D printer. The additive manufacturing machine 100 includes a spreader 102 that is used to spread a build material 104 (in powder form) onto a build bed 106. The build bed 106 can either be a base plate (if a first layer of build material is being dispensed) or a previously formed 3D part (formed using a layer build material or multiple layers of build material). The spreader 102 can be in the form of a blade, a roller, and so forth.

[0030] The spreader 102 is moved along a spreading direction 105 (or multiple spreading locations), starting at a supply station 108 that supplies the build material 104. A dispensing surface 110 of the powder supply station 108 has a supply of build material 104 that is spread by the spreader 102 across the upper surface of the build bed 106 as the spreader 102 is moved in the spreading direction 105 across the build bed 106. A layer of build material 112 (hereinafter referred to as a“build material layer”) is formed on the build bed 106.

[0031 ] Once the build material layer 112 is formed on the build bed 106, an agent dispensing assembly 114, which can include a printhead, can be activated to dispense a liquid agent 116 onto a surface of the build material layer 112. The agent dispensing assembly 114 can include an array of nozzles 115 that include respective orifices through which drops of the liquid agent can be dispensed towards the build material layer 112. In some examples, the agent dispensing assembly 114 (or multiple agent dispensing assemblies) can dispense different types of liquid agents onto the build material layer 112.

[0032] The operation of the agent dispensing assembly 114 can be controlled by a controller 118 of the additive manufacturing machine 100. As used here, a “controller” can refer to a hardware processing circuit, which can include any or some combination of a microprocessor, a core of a multi-core microprocessor, a microcontroller, a programmable integrated circuit, a programmable gate array, or another hardware processing circuit. Alternatively, a“controller” can refer to a combination of a hardware processing circuit and machine-readable instructions (software and/or firmware) executable on the hardware processing circuit.

[0033] In some examples, the controller 118 receives a representation 120 of a physical 3D object that is to be built by the additive manufacturing machine 100. The representation 120 of the 3D objection can be in the form of a CAD model or any other digital representation of the 3D object.

[0034] The controller 118 includes slicing logic 122 that generates digital data slices 124 based on the representation 120 of the 3D object. As used here, a“logic” that is included in the controller 118 can refer to a portion of the hardware processing circuit of the controller 118, or machine-readable instructions executable by the controller 118. [0035] Each digital data slice 124 contains information corresponding to an individual build material layer. The digital data slice 124 can include information pertaining to locations where a liquid agent to be applied to the individual build material layer. In further examples, a digital data slice 124 can include information pertaining to locations where multiple liquid agents are to be applied to an individual build material layer. In other examples, multiple digital data slices 124 can include information pertaining to locations where multiple liquid agents are to be applied to an individual build material layer.

[0036] Information in the digital data slice(s) 124 pertaining to locations where the liquid agent(s) is (are) to be applied to an individual build material layer can control which selected nozzles of the agent dispensing assembly 114 to activate to dispense the liquid agent(s) at the locations.

[0037] The controller 118 further includes a dry voxel pattern generation logic 126 that receives the digital data slices 124. The dry voxel pattern generation logic 126 is able to add a pattern of dry voxels (or multiple patterns of dry voxels) to a digital data slice (or multiple digital data slices) 124 corresponding to parts of the build material layer where edge adjustment is to be performed at a greater control than possible with the nozzles 115 of the agent dispensing assembly 114.

[0038] “Adding” a pattern of dry voxels to a digital data slice 124 can refer to either (1 ) modifying the digital data slice 124 as received from the slicing logic 122 to add information representing the pattern of dry voxels (where the modifying can include replacing a wet voxel in the digital data slice 124 with a dry voxel in the digital data slice 124), or (2) generating a new digital data slice that includes the pattern of dry voxels as well as certain information of the digital data slice 124 as received from the slicing logic 122.

[0039] In other examples, the slicing logic 122 and the dry voxel pattern generation logic 126 can be executed in a controller that is separate from the additive manufacturing machine 100. [0040] In examples where different types of liquid agents (e.g., a fusing agent and a detailing agent) are to be applied, the dry voxel pattern generation logic 126 can add a pattern of dry voxels for the fusing agent and a pattern of dry voxels for the detailing agent. The pattern of dry voxels for the detailing agent may be based on the pattern of dry voxels for the fusing agent.

[0041 ] Fig. 2 is a top view of a build material layer 202. The build material layer 202 includes a first build material portion 202-1 in which a 3D part is not to be formed, and a second build material portion 202-2 in which a 3D part is to be formed In the first build material portion 202-1 where a 3D part is not to be formed, no liquid agent is applied. Flowever, in the second build material portion 202-2 in which a 3D part is to be formed, a liquid agent is applied at specified locations. Note that there may be some locations within the second build material portion 202-2 in which a liquid agent is not applied. The respective digital data slice 124 (Fig. 1 ) can specify that the liquid agent is to be dispensed at certain locations of the second build material portion 202-2, but not at other locations of the second build material portion 202-2.

[0042] Fig. 3 is an expanded view that shows an area 204 identified in Fig. 2. As shown in Fig. 3, a pattern of dry voxel regions 302 can be formed in the second build material portion 202-2. Each dry voxel region 302 includes a region of the build material portion 202-2 where a liquid agent is not applied. The pattern of dry voxel regions 302 can be formed based on a pattern of dry voxels added to the

corresponding digital data slice 124. A dry voxel region 302 of the pattern can replace a wet voxel region that would have been formed based on the representation of the 3D object 120.

[0043] The liquid agent applied at various locations of the build material portion 202-2 (surrounding the dry voxel regions 302) can flow into the dry voxel regions 302. The effect of allowing liquid agent flow into the dry voxel regions 302 is that an edge 304 of the build material layer 202 (more specifically, the boundary of the build material portion 202-2) is moved inwardly in the direction indicated by the arrow 306. [0044] To perform an adjustment of the location of the edge 304, the pattern of dry voxel regions 302 is added to an edge segment 310 of the build material portion 202-2. An“edge segment” refers to a segment of the build material portion 202-2 that is in proximity to, or even at, the edge 304, such that liquid agent flow into the dry voxel regions 302 can modulate the location of the edge 304.

[0045] An edge segment is distinguished from an interior segment, such as interior segment 312 in Fig. 3. The interior segment 312 farther away from the edge 304 of the layer of build material than the edge segment 310.

[0046] Although Fig. 3 shows the pattern of dry voxel regions 302 formed in a particular edge segment of the build material portion 202-2, it is noted that patterns of dry voxel regions can be formed in other edge segments of the build material portion 202-2, such as edge segments proximate other edges of the build material portion 202-2.

[0047] Fig. 3 shows a pattern of dry voxel regions 302 that are discretely formed— in other words, no two dry voxel regions 302 are adjacent or continuous with one another. In other examples, there can be a number (e.g., 2 to 8 or some other range) of continuous dry voxel regions 302 in the pattern.

[0048] In the example of Fig. 3, the introduction of the dry voxel regions 302 is to adjust a location of the edge 304 of the build material portion 202-2 in the X-Y plane (horizontal plane). It is noted that in further examples, a pattern of dry voxel agents can be introduced to move an edge in the Z axis (vertical plane) that is perpendicular to the X and Y axes.

[0049] Fig. 3A shows an example of how liquid agent flow into the dry voxel regions 302 of Fig. 3 has effectively moved the location of the edge 304 (in dashed profile in Fig. 3A) inwardly in the X direction to edge location 304A in Fig. 3A.

[0050] In the example of Figs. 2, 3, and 3A, the 3D part to be formed (as represented by the build material portion 202-2) is generally rectangular in shape. In other examples, the 3D part to be formed can have a cylindrical shape, such as shown in Figs. 4 and 5. Fig. 4 is a top view of a build material layer 402 that includes a first build material portion 402-1 in which the 3D part is not to be formed, and a second build material portion 402-2 in which the 3D part is to be formed.

[0051 ] Fig. 5 is an expanded view of an area 404 of the build material layer 402. As shown in Fig. 5, a pattern of dry voxel regions 502 can be formed in the second build material portion 402-2. Each dry voxel region 502 includes a region of the build material portion 402-2 where a liquid agent is not applied. The pattern of dry voxel regions 502 is formed in an edge segment of the build material portion 402-2 to adjust a location of an edge 504 of the build material portion 402-2. Liquid agent flow into the dry voxel regions 502 would cause the edge 504 to move inwardly similar to that depicted in Fig. 3A.

[0052] Although example patterns of dry voxel regions are shown in Figs. 3 and 5, it is noted that other patterns of dry voxel regions can be used in other examples. Either a regular pattern or irregular pattern of dry voxel regions can be used.

Empirical data of edge locations of build material layers that can be provided by an additive manufacturing machine can be collected. Further, empirical data of edge locations of build material layers when different patterns of dry voxel regions are used can be collected. Then using the empirical data, a user or a program can decide which pattern of dry voxel regions to use to achieve a target edge profile (such as specified in a request to build a 3D object) of a build material layer. A rule or algorithm can be developed to select a pattern of dry voxel regions (from among multiple possible patterns of dry voxel regions) for achieving a target edge profile of a build material layer.

[0053] The depth of the pattern of dry voxel regions from the edge of the build material layer can also be selected. The dry voxel regions can be formed all the way up to the edge of the build material layer. Alternatively, the dry voxel regions can be formed some distance away from the edge of the build material layer. The adjustment of the edge of the build material layer can vary based on how far from the edge of the build material layer the dry voxel regions. The depth of the pattern of dry voxel regions can thus be selected, such as based on empirical data of how different depths affect edge adjustments.

[0054] Fig. 6 is a block diagram of a non-transitory machine-readable or computer-readable storage medium 600 comprising machine-readable instructions that upon execution cause a system (e.g., an additive manufacturing machine, a computer that provides data to an additive manufacturing machine to build physical 3D objects, etc.) to perform respective tasks.

[0055] The machine-readable instructions include liquid agent location

determination instructions 602 to determine, based on a representation of an object (e.g., representation 120 of Fig. 1 ) to be formed by an additive manufacturing machine, locations in a layer of build material where a liquid agent is to be applied.

[0056] The machine-readable instructions further include edge adjustment instructions 604 to perform an edge adjustment of an edge of the layer of build material with greater control of placement of a location of the edge of the layer of build material than achievable by a dispensing assembly (e.g., 114 in Fig. 1 ) for the liquid agent. The edge adjustment performed by the edge adjustment instructions 604 adjusts a location of the edge of the layer of build material relative to a location of the edge of the layer of build material specified by the representation of the object, the controlling of the location of the edge comprising adding a pattern of dry voxels in digital data (e.g., digital data slice 124 in Fig. 1 ) representing locations of the layer of build material where the liquid agent is to be applied.

[0057] The machine-readable instructions can also include instructions to identify an edge segment of a layer of build material that is proximate the edge of the layer of build material that is to be adjusted. The adding of the pattern of the dry voxels can occur in a portion of the digital data representing the edge segment of the layer of build material.

[0058] In some implementations, dry voxels for providing a dimensional control increase (increase in any one or some combination of resolution, accuracy, or precision) are not added to a portion of the digital data representing an interior segment (e.g., 312 in Fig. 3) of the layer of build material, where the interior segment is farther away from the edge of the layer of build material than the edge segment (e.g., 310 in Fig. 3).

[0059] The machine-readable instructions can also include instructions to identify a further edge segment of the layer of build material that is proximate a further edge of the layer of build material, where the adding of the pattern of the dry voxels occurs in a further portion of the digital data representing the further edge segment of the layer of build material. In some examples, dry voxels are not added to a portion of the digital data representing an interior segment of the layer of build material, the interior segment being between the edge segments of the layer of build material.

[0060] Fig. 7 is a block diagram of an additive manufacturing machine 700 according to further examples. The additive manufacturing machine 700 includes an agent dispensing assembly 702 to dispense a liquid agent onto a layer of build material. The additive manufacturing machine 700 further includes a controller 704 to perform various tasks. The tasks performed by the controller 704 can include a liquid agent locations determination task 706 to determine, based on a

representation of an object to be formed by the additive manufacturing machine, locations in a layer of build material where a liquid agent is to be applied.

[0061 ] The tasks performed by the controller 704 can further include an edge segment identification task 708 to identify an edge segment of the layer of build material, the edge segment proximate an edge of the layer of build material. The tasks further include an edge adjustment task 710 to, as part of an edge adjustment to control a location of the edge of the layer of build material relative to a location of the edge of the layer of build material specified by the representation of the object, add a pattern of dry voxels in an edge portion of digital data corresponding to the edge segment, the digital data representing locations of the layer of build material where the liquid agent is to be applied. [0062] Fig. 8 is a flow diagram of an additive manufacturing process that includes applying (at 802), using an agent dispensing assembly, a liquid agent to a layer of build material based on digital data comprising a pattern of dry voxels added to adjust a location of an edge of the layer of build material with greater control than achievable by the agent dispensing assembly, the adjusting of the location of the edge of the layer of build material changing a location of the edge relative to a location of the edge of the layer of build material specified by a representation of an object to be built by the additive manufacturing machine.

[0063] The storage medium 600 of Fig. 6 can include any or some combination of the following: a semiconductor memory device such as a dynamic or static random access memory (a DRAM or SRAM), an erasable and programmable read- only memory (EPROM), an electrically erasable and programmable read-only memory (EEPROM) and flash memory; a magnetic disk such as a fixed, floppy and removable disk; another magnetic medium including tape; an optical medium such as a compact disk (CD) or a digital video disk (DVD); or another type of storage device. Note that the instructions discussed above can be provided on one computer-readable or machine-readable storage medium, or alternatively, can be provided on multiple computer-readable or machine-readable storage media distributed in a large system having possibly plural nodes. Such computer-readable or machine-readable storage medium or media is (are) considered to be part of an article (or article of manufacture). An article or article of manufacture can refer to any manufactured single component or multiple components. The storage medium or media can be located either in the machine running the machine-readable instructions, or located at a remote site from which machine-readable instructions can be downloaded over a network for execution.

[0064] In the foregoing description, numerous details are set forth to provide an understanding of the subject disclosed herein. Flowever, implementations may be practiced without some of these details. Other implementations may include modifications and variations from the details discussed above. It is intended that the appended claims cover such modifications and variations.

Claims

What is claimed is:

1. A non-transitory machine-readable storage medium comprising instructions that upon execution cause a system to:

determine, based on a representation of an object to be formed by an additive manufacturing machine, locations in a layer of build material where a liquid agent is to be applied; and

perform an edge adjustment of an edge of the layer of build material with greater control of placement of a location of the edge of the layer of build material than achievable by a dispensing assembly for the liquid agent, the edge adjustment comprising adjusting the location of the edge of the layer of build material relative to a location of the edge of the layer of build material specified by the representation of the object, the adjusting of the location of the edge comprising adding a pattern of dry voxels in digital data representing locations of the layer of build material where the liquid agent is to be applied, each dry voxel of the pattern of dry voxels defining a respective dry voxel region in the layer of build material that is without the liquid agent and that is to receive a flow of a portion of the liquid agent applied to the layer of build material.

2. The non-transitory machine-readable storage medium of claim 1 , wherein the liquid agent comprises a fusing agent or a detailing agent.

3. The non-transitory machine-readable storage medium of claim 1 , wherein the liquid agent comprises a binder.

4. The non-transitory machine-readable storage medium of claim 1 , wherein the instructions upon execution cause the system to:

identify an edge segment of the layer of build material that is proximate the edge of the layer of build material,

wherein the adding of the pattern of the dry voxels occurs in a portion of the digital data representing the edge segment of the layer of build material.

5. The non-transitory machine-readable storage medium of claim 4, wherein dry voxels for providing a dimensional control increase are not added to a portion of the digital data representing an interior segment of the layer of build material, the interior segment farther away from the edge of the layer of build material than the edge segment.

6. The non-transitory machine-readable storage medium of claim 4, wherein the instructions upon execution cause the system to:

identify a further edge segment of the layer of build material that is proximate a further edge of the layer of build material,

wherein the adding of the pattern of the dry voxels occurs in a further portion of the digital data representing the further edge segment of the layer of build material.

7. The non-transitory machine-readable storage medium of claim 6, wherein dry voxels for providing a dimensional control increase are not added to a portion of the digital data representing an interior segment of the layer of build material, the interior segment being between the edge segment and the further edge segment.

8. The non-transitory machine-readable storage medium of claim 1 , wherein the dry voxel regions are to reduce movement of the liquid agent to the edge of the layer of build material.

9. The non-transitory machine-readable storage medium of claim 1 , wherein the edge of the layer of build material is an edge in a horizontal plane of the layer of build material.

10. The non-transitory machine-readable storage medium of claim 1 , wherein the edge of the layer of build material is an edge in a vertical plane of the layer of build material.

11. An additive manufacturing machine comprising:

an agent dispensing assembly to dispense a liquid agent onto a layer of build material; and

a controller to:

determine, based on a representation of an object to be formed by the additive manufacturing machine, locations in a layer of build material where a liquid agent is to be applied;

identify an edge segment of the layer of build material, the edge segment proximate an edge of the layer of build material; and

as part of an edge adjustment to control a location of the edge of the layer of build material relative to a location of the edge of the layer of build material specified by the representation of the object, add a pattern of dry voxels in an edge portion of digital data corresponding to the edge segment, the digital data

representing locations of the layer of build material where the liquid agent is to be applied, each dry voxel of the pattern of dry voxels defining a respective dry voxel region in the layer of build material that is without the liquid agent and that is to receive a flow of a portion of the liquid agent applied to the layer of build material.

12. The additive manufacturing machine of claim 11 , wherein the edge

adjustment using the pattern of dry voxels achieves the edge adjustment at a greater control than a control provided by the agent dispensing assembly.

13. The additive manufacturing machine of claim 11 , wherein the controller is to: not add dry voxels for providing a dimensional control increase to a portion of the digital data representing an interior segment of the layer of build material, the interior segment farther away from the edge of the layer of build material than the edge segment.

14. A method of an additive manufacturing machine, comprising:

applying, using an agent dispensing assembly, a liquid agent to a layer of build material based on digital data comprising a pattern of dry voxels added to adjust a location of an edge of the layer of build material with greater control than achievable by the agent dispensing assembly, the adjusting of the location of the edge of the layer of build material changing a location of the edge relative to a location of the edge of the layer of build material specified by a representation of an object to be built by the additive manufacturing machine,

wherein each dry voxel of the pattern of dry voxels defines a respective dry voxel region in the layer of build material that is without the liquid agent and that is to receive a flow of a portion of the liquid agent applied to the layer of build material.

15. The method of claim 14, further comprising:

generating, by a controller that is part of the additive manufacturing machine or that is external of the additive manufacturing machine, the digital data with the dry voxels added.