WO2017095404A1

WO2017095404A1 - Build layer sensing

Info

Publication number: WO2017095404A1
Application number: PCT/US2015/063436
Authority: WO
Inventors: Alejandro Manuel De Pena; Miguel Angel LOPEZ; Sebastia CORTES I HERMS
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2015-12-02
Filing date: 2015-12-02
Publication date: 2017-06-08

Abstract

Examples include an apparatus comprising a build material support, a scanning carriage, and a build layer sensing system. The scanning carriage is to move along a scanning axis over the build material support. The build layer sensing system is to emit light over the build material support and along a sensing axis, and the build layer sensing system is further to detect light emitted over the build material support. Light emitted by the build layer sensing system is to move along the scanning axis with movement of the scanning carriage. A controller may determine build layer characteristics for a layer of build material in the build area based at least in part on detected light.

Description

BUILD LAYER SENSING

BACKGROUND

[0001] Additive manufacturing systems that generate three-dimensional objects on a layer-by-layer basis are convenient way for producing three- dimensional objects. Examples of additive manufacturing systems include three-dimensional printing systems. The quality of objects produced by additive manufacturing systems may vary widely based on the type of additive manufacturing technology used.

DRAWINGS

[0002] FIG. 1 provides a block diagram of some components of an example apparatus for generating three-dimensional objects.

[0003] FIGS 2A-D provide block diagrams of some components of an example apparatus for generating three-dimensional objects.

[0004] FIG. 3 provides a block diagram of some components of an example apparatus for generating three-dimensional objects.

[0005] FIG. 4 provides a block diagram of some components of an example apparatus for generating three-dimensional objects.

[0006] FIG. 5 provides a block diagram of some components of the example apparatus of FIG. 4.

[0007] FIG. 6 provides a flowchart that illustrates a sequence of operations that may be performed by an example apparatus.

[0008] FIG. 7 provides a flowchart that illustrates a sequence of operations that may be performed by an example apparatus.

[0009] FIG. 8 provides a flowchart that illustrates a sequence of operations that may be performed by an example apparatus. [0010] FIG. 9 provides a flowchart that illustrates a sequence of operations that may be performed by an example apparatus.

[0011] FIG. 10 provides a flowchart that illustrates a sequence of operations that may be performed by an example apparatus.

[0012] FIG. 11 provides a flowchart that illustrates a sequence of operations that may be performed by an example apparatus.

[0013] FIG. 12 provides a flowchart that illustrates a sequence of operations that may be performed by an example apparatus.

[0014] FIGS. 13A-B provide example charts associated with example apparatuses.

[0015] Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements. The figures ate 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.

DESCRIPTION

[0016] Examples provided herein include apparatuses and processes for generating three-dimensional objects. Apparatuses for generating three- dimensional objects may be referred to as additive manufacturing apparatuses and additive manufacturing processes. As will be appreciated, example apparatuses described herein may correspond to three-dimensional printing systems, which may also be referred to as three-dimensional printers. In an example additive manufacturing process, a layer of build material may be distributed in a build area of a build material support, an agent may be selectively distributed on the layer of build material, and energy may be temporarily applied to the layer of build material.

[0017] The application of energy may cause portions of the layer of build material to which agent has been applied to begin to coalesce. The coalescing of build material may be referred to as fusing, and the temperature at which portions of the layer of build material may begin to coalesce may be referred to as a fusing temperature. Upon cooling, portions of the build material layer that have coalesced become solid and form part of a three-dimensional object being generated.

[0018] Additional layers may be distributed and the operations described above may be performed for each layer to thereby generate a three-dimensional object. As will be appreciated, each layer may correspond to a cross-section of a three-dimensional object to be formed. Sequentially layering and fusing layers of build material on top of previous layers may facilitate generation of the three-dimensional object. The layer-by-layer formation of a three-dimensional object may be referred to as a layer-wise additive manufacturing process. In some examples, a height of a build layer (which may also be referred to as thickness) may be in the micron scale. For example, some example build layer heights may be in the range of approximately 90 to 110 microns. Furthermore, an overall build height of the cumulative layers of build material may be in the centimeter or meter scale depending on the apparatus and process

implemented.

[0019] in examples described herein, a build material may include a powder-based build material, where powder-based build material may comprise wet and/or dry powder-based materials, particulate materials, and/or granular materials, in some examples, the build material may be a weak light absorbing polymer. In some examples, the build material may be a thermoplastic.

Furthermore, as described herein, agent may comprise fluids that may facilitate fusing of build material when energy is applied. In some examples, agent may be referred to as coalescing agent. In some examples, agent may be a light absorbing fluid, such as a pigment colorant

[0020] Generally, build material distributed in a layer on the build area may have a corresponding build layer height at various locations in the print area. As will be appreciated, a quality associated with a three-dimensional object formed in an additive manufacturing process may be at least partially based on uniformity of build layer height over the build area. Particularly, deviations in build layer height of build material over the build area may lead to defects in the formed three-dimensional object. Accordingly, monitoring of build layer height for each distributed build layer during an additive manufacturing process may facilitate improved quality in three-dimensional objects generated by such processes. In addition, in some additive manufacturing processes and apparatuses that perform such processes, a build layer height that exceeds a particular maximum threshold may cause errors in the process or damage to the apparatus.

[0021] Example apparatuses comprise a build layer sensing system with which to emit light along a sensing axis and across a build area of the apparatus. In some examples, light emitted by the build layer sensing system may move along a scanning axis over the build area, where the scanning axis is orthogonal to the sensing axis. The light emitted along the sensing axis may be detected by the build layer sensing system. By moving light emitted by the build layer sensing system over the scanning axis and detecting such emitted light during the movement thereof, examples may thereby scan build material distributed as a build layer in the build area. In some examples, detected light may be analyzed to thereby analyze a build layer of build material distributed in the build area. For example, a build layer height may be determined at locations along the scanning axis (and therefore locations of the build are) based at least in part on light detected by the build layer sensing system.

[0022] Example build layer sensing systems may comprise emitters to emit light and receivers to detect such emitted light, in some examples, the build layer sensing systems may comprise laser emitters and laser receivers. In some examples, build layer sensing systems may comprise ultraviolet emitters and ultraviolet receivers. While reference may be made to light emitters and sensors, some examples may implement various other types of electromagnetic radiation emitters and receivers such as radio-based emission/detection systems, x-ray based emission/detection systems, infrared-based

emission/detection systems, etc.

[0023] Example apparatuses described herein comprise a build material support, where a surface of the build material support may correspond to a build area. Accordingly, a first layer of build material may be distributed on the surface of the build material support in the build area. Subsequent layers of build may be distributed in the build area on previously distributed and fused layers. Furthermore, apparatuses may comprise one or more energy sources with which to temporarily apply energy to build material layers to heat the build material layers. For example, an apparatus may comprise at least one energy source that may heat a build material layer such that portions of the build material layer where agent has been distributed may fuse. In some examples, apparatuses may further comprise additional energy sources with which to preheat build material layers.

[0024] Example apparatuses may comprise at least one scanning carriage, where the at least one scanning carriage may be moveable along a scanning axis over the build area and over build material distributed in the build area, in some examples, the build layer sensing system may emit light across the build area along a sensing axis, where the sensing axis may be

approximately orthogonal to the scanning axis along which the scanning carriage may move. In such examples, light emitted by the build layer sensing system may move along the scanning axis as a scanning carriage moves along the scanning axis.

[0025] Accordingly, the build layer sensing system may emit light across the build area and detect such emitted light while the scanning carriage moves along the scanning axis such that the build area is scanned based on light emitted and detected by the build layer sensing system as the scanning carriage moves along the first scanning axis. Example apparatuses may analyze light emitted by and detected with a build layer sensing system to determine characteristics of a build material layer scanned according to the processes and operations described herein. As will be appreciated, light may be emitted by such example apparatuses across the build area and over build material distributed therein, where such light may approximately skim a top surface of build material distributed therein. Therefore, even relatively small scale (e.g., micron scale, millimeter scale, etc.) differences in height of build material of a layer may cause changes in light detected after passing across the build area.

[0026] In addition, example apparatus may comprise an agent distributor coupled to a scanning carriage. In some examples, an agent distributor may comprise a printhead or printheads (e.g., a thermal ejection based printhead, a piezoelectric ejection based printhead, etc.). In one example, printheads suitable for implementation in commercially available inkjet printing devices may be implemented as an agent distributor. In other examples, an agent distributor may comprise other types of fluid ejection devices that selectively eject small volumes of fluid.

[0027] In some examples, apparatuses may comprise a build material distributor to distribute build material in the build area. A build material distributor may comprise, for example, a wiper blade, a roller, and/or a spray mechanism. In some examples, a build material distributor may be coupled to a scanning carriage. In these examples, the build material distributor may distribute build material in the build area as the scanning carriage moves over the build area along the scanning axis to thereby distribute a layer of build material in the build area.

[0028] Turning now to the figures, and particularly to FIG. 1, this figure provides a block diagram of some components of an example apparatus 10 for generating a three-dimensional object. In this example, the apparatus may comprise a build material support 12 having a surface mat corresponds to a build area 14. As will be appreciated, build material may be distributed in the build area 14 on the surface of the build material support 12. Furthermore, in this example, the apparatus 10 comprises a scanning carriage 16 that may move bi-directionally along a scanning axis 18 over the build area 14. The apparatus 10 further comprises a build layer sensing system 20. As shown for illustrative purposes, the build layer sensing system 20 may emit light 22 along a sensing axis, where the sensing axis may be approximately orthogonal to the scanning axis 18.

[0029] As shown in this example, a plane of the surface of the build material support 14 corresponding to the build area 14 of the apparatus 10 may be approximately parallel to the scanning axis 18 and the sensing axis of light 22 emitted by the build layer sensing system 20. To emit light, the build layer sensing system 20 may comprise an emitter 24, and, to detect emitted light, the build layer sensing system 20 may comprise a receiver 26. in mis example, the emitter 24 is positioned on a first side of the build area 14 and the receiver 26 is positioned on a second side of the bui!d area 14 that is opposite the first side. As will be appreciated, as the scanning carriage 16 moves along the scanning axis 18 over the build area 14, the build layer sensing system 20 may emit light 22 across the build area 14 along the first sensing axis. In examples similar to the example of FIG. 1 , light detected by the build layer sensing system as the scanning carriage moves along the first scanning axis 18 may be analyzed to thereby analyze a layer of build material distributed in the build area 14. In this example, the emitter 24 and receiver 26 are coupled to the scanning carriage 16. Hence, in this example, as the scanning carriage 16 moves along the scanning axis 18, the emitter 24 and the receiver 26 move along the scanning axis 18 such that emitted light 22 of the build layer sensing system 20 moves along the scanning axis 18 to thereby scan build material distributed in a layer in the build area 14.

[0030] Furthermore, as will be appreciated, a first layer of build material may be distributed on the surface of the build material support 12 in the corresponding build area 14. and agent may be selectively distributed on the first layer of build material. The first layer of build material may be fused by controlled application of energy to the build layer. After fusing the first layer of build material, additional layers of build material may be sequentially distributed and fused on top of each previous layer in the build area 14. For each sequential layer, the example may analyze each layer of build material in the build area 14 by analyzing light emitted by Hie build layer sensing system 20 after distribution of the layer of build material. Therefore, the build area 14 refers to the area corresponding to the surface of the build material support 12 in which layers of build material may be distributed and fused in a layer-wise additive manufacturing process.

[0031 ] As shown, the example apparatus 10 further comprises a controller 28 that may be connected to die build layer sensing system 20 and the scanning carriage 16. In examples similar to the example of FIG. 1, the controller 28 may analyze light detected by the receiver 26 to thereby determine build layer characteristics of a build layer distributed in the build area 14. Examples of build layer characteristics that may be determined by analysis of the detected light may comprise a build layer height at locations along the scanning axis, a build layer uniformity, agent distribution in the build area 14, and/or other similar characteristics. Furthermore, in some examples, the controller 28 may control movement of the scanning carriage 16 along the scanning axis 18. In addition, in some examples, the controller may control emission of light by the emitter 24 during movement of the scanning carriage 16 such that the controller may control scanning of a layer of build material in the build area 14 by the build layer sensing system 20.

[0032] FIGS. 2A-D provide block diagrams that illustrate some components of an example apparatus 50. In this example, the apparatus 50 comprises a build material support 52 having a surface that corresponds to a build area 54 in which layers of build material may be deposited and fused in a layer-wise additive manufacturing process to form a three-dimensional object, in this example, the apparatus 50 comprises a scanning carriage 56 that may move bi-directionally along a scanning axis 57. In this example, the apparatus 50 comprises a build layer sensing system 58 that includes an emitter 60, a receiver 62, a first deflector 64, and a second deflector 66. in this example, the emitter 60 and the receiver 62 may be stationary - i.e., not movable with the scanning carriage 56.

[0033] To illustrate by way of example, FIGS. 2A-D illustrate light 68 that may be emitted by the build layer sensing system 58 across the build area 54 along a sensing axis. As illustrated in FIGS. 2A-D, the emitter 60 may emit light approximately parallel to the scanning axis 57, and the first deflector 64 may deflect light emitted from the emitter 60 across the build area 54 along a sensing axis to the second deflector 66. As will be appreciated, in some examples, the sensing axis may be approximately orthogonal to the scanning axis 57. The second deflector 66 deflects light approximately parallel to the scanning axis 57 to the receiver 62. Therefore, in this example, light emitted by the build layer sensing system 58 and deflected by the first deflector 64 along the sensing axis may move along the scanning axis 57 as the scanning carriage 56 moves. [0034] in some examples, the apparatus 50 may further comprise additional components 70 coupled to the scanning carriage 56, where the additional components may be used to perform various operations as the scanning carriage 56 moves along the scanning axis 58 over the build area 54. For example, the additional components 70 may comprise an energy source (such as a lamp or radiation source) that may heat build material as the scanning carriage 56 moves over the build area 54. In some examples, the additional components 70 may comprise an agent distributor to distribute an agent on a layer of build material distributed in the build area 54 as the scanning carriage 56 moves along the scanning axis 58 over the build area 54. In some examples, the additional components 70 may comprise a build material distributor to distribute build material in the build area 54 as the scanning carriage moves along the scanning axis 58 over the build area 54. As will be appreciated, some examples may concurrently scan a layer of build material with the build layer sensing system while performing additional operations associated with the additional components 70 as the scanning carriage 56 moves along the scanning axis 58 over the build area 54.

[0035] FIGS. 2A-D illustrate the scanning carriage 56 at different locations along the scanning axis 58 as the scanning carriage moves along the scanning axis 58. Particularly, FIG. 2A illustrates the scanning carriage 56 at a first location along the scanning axis 58. In the example of FIG. 2A the scanning carriage 58 may move in a first direction (indicated by directional arrow 72) along the scanning axis 58. In FIG. 2B, the scanning carriage 56 has moved along the scanning axis 58 in the first direction 72, such that the scanning carriage 56 is positioned in the build area 54. As will be appreciated, light deflected by the first deflector 64 across the build area 54 along the sensing axis to the second deflector 66 may pass over the build area 54 at a distance from build material in the build area 54 such that light detected by the build layer sensing system 58 may be analyzed to determine characteristics of a build layer associated with the location at which the scanning carriage 56 is positioned on the scanning axis 57. In FIG. 2C, the scanning carriage 56 has moved over the build area 54 along the scanning axis 57. In FIG. 2D, the scanning carriage 56 has moved along the scanning axis 58 in a second direction 76.

[0036] FIG. 3 provides a block diagram of some components of an example apparatus 100. In this example, die apparatus 100 may comprise a build material support 102. As will be appreciated, in some examples, the build material support 102 may not be included in the apparatus 100; hence, the build material support 102 is illustrated in dashed line. As discussed previously, the build material support 102 may have a build surface that corresponds to a build area 104 in which layers of build material may be sequentially distributed and fused. The example apparatus 100 comprises a first scanning carriage 106 and a second scanning carriage 108. In addition, the apparatus 100 includes a first build layer sensing system 110 and a second build layer sensing system 112. in this example, the first scanning carriage 106 may move over the build area 104 along a first scanning axis 114, and the second scanning carriage 108 may move over the build area 104 along a second scanning axis 116. As will be appreciated, the first scanning axis 114 is approximately orthogonal to the second scanning axis 116. Furthermore, the first scanning axis 114 and the second scanning axis 116 are approximately parallel to a plane of the surface of the build material support 102.

[0037] The first build layer sensing system 110 is to emit light 118 across the build area 104 along a first sensing axis, and the second build layer sensing system 112 is to emit light 120 across the build area 104 along a second sensing axis. For illustration purposes, FIG. 3 provides example illustrations of emitted light 118, 120. As shown, the first build layer sensing system 110 comprises a first emitter 122, a first receiver 124, a first deflector 126, and a second deflector 128. In this example, light deflected from the first deflector 126 to the second deflector 128 is along the first sensing axis, where the first sensing axis is approximately orthogonal to the first scanning axis 114. The first deflector 126 and the second deflector 128 may be coupled to the first scanning carriage 106 such that light 118 emitted by the first build layer sensing system 110 and deflected by the first deflector 126 to the second deflector 128 may move along the first scanning axis 114 over the build area 104 as the first scanning carriage 106 moves along the first scanning axis 114. As wilt be appreciated, the first receiver 124 may detect light emitted by the first emitter 122 that has been deflected by the first deflector 126 along the first sensing axis across the build area 104 and deflected by the second deflector 128 to the first receiver 124.

[0038] The second build layer sensing system 112 comprises a second emitter 130, a second receiver 132, a third deflector 134, and a fourth deflector 136. in this example, light deflected from the third deflector 134 to the fourth deflector 136 is along the second sensing axis, where the second sensing axis is approximately orthogonal to the second scanning axis 116. The third deflector 134 and the fourth deflector 136 may be coupled to the second scanning carriage 108 such that light 120 emitted by the second build layer sensing system 112 and deflected by the third deflector 134 to the fourth deflector 136 may move along the second scanning axis 116 over the build area 104 as the second scanning carriage 108 moves along the second scanning axis 116. As will be appreciated, the second receiver 132 may detect light emitted by the second emitter 130 that has been deflected by the third deflector 134 along the second sensing axis across the build area 104 and deflected by the fourth deflector 136 to the second receiver 132.

[0039] As discussed in previous examples, the scanning carriages 106, 106 may comprise additional components 140. in some examples, the additional components 140 coupled to the first scanning carriage 106 and/or second scanning carriage 108 may comprise, for example, energy sources, agent distributors, and/or build material distributors.

[0040] In addition, in the example shown in FIG. 3, the apparatus 100 includes a data processing subsystem 158 that comprises a processing resource 160 and a machine-readable medium 162. In examples described herein, a processing resource 160 may include at least one hardware based processor. As will be appreciated, a processing resource 160 may comprise one or more general purpose data processors and/or one or more specialized data processors. For example, the processing resource 160 may comprise a central processing unit (CPU), a graphics processing unit (GPU), an application- specific integrated circuit (ASIC), a controller, and/or other such configurations of logical components tor data processing,

[0041] Furthermore, in the examples, the machine-readable medium 162 may comprise a machine-readable storage medium, which may be referred to as a memory and/or a memory resource. The machine-readable memory may represent random access memory (RAM) devices as well as other types of memory (e.g. cache memories, non-volatile memory devices, read-only memories, mass-storage resources, etc.). Computer readable and/or machine- readable storage medium may Include RAM, ROM, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory, flash memory or other solid state memory technology, portable compact disc memory, or other optical storage, or any other medium that may be used to store executable instructions and information. Furthermore, the machine-readable storage medium 162 may be non-transitory.

[0042] As shown, the machine-readable memory 162 includes instructions 144 that may be executable by the processing resource 160, where execution of the instructions may cause the processing resource 160 and/or apparatus 100 to perform the functionalities, processes, and/or sequences of operations described herein. For example, execution of the instructions 164 by the processing resource 160 may control movement of the scanning carriages 106, 108. As another example, execution of the instructions 164 may cause the build layer sensing systems 110, 112 to scan a layer of build material distributed on the build material support 102 in the build area 104. In some examples, execution of the instructions 164 may control operation of the additional components 140. Furthermore, in some examples, execution of the instructions 164 may cause the apparatus 100 to analyze light detected by the build layer sensing systems 110, 112 to thereby analyze a layer of build material.

[0043] Turning now to FIG. 4, this figure provides a perspective view of some components of an example apparatus 200. In this example, the apparatus 200 may comprise a build material support 202 having a build surface 204 upon which layers of build material may be distributed in a layer- wise additive manufacturing process. The build surface 204 corresponds to a build area in which build material and agent may be distributed for processing as described herein. Furthermore, in this example, file apparatus 200 comprises a build material container 206 that may store build material to be distributed during operation of the apparatus 200. For illustrative purposes, FIG. 4 includes reference axes 212, 214, 216 - including an X axis 212, a Ύ' axis 214, and a 'Ζ' axis 216. In this example, the X axis 212, Y axis 214, and Z axis 216 are approximately orthogonal to each other. As will be appreciated, the reference axes 212-216 are provided to facilitate describing the relative orientations of various components of the apparatus 200. In an example layer- wise additive manufacturing process, the layer-by-layer processing may occur along the Z axis 216 - i.e., each sequential layer may be deposited on the build material support 202 such that a height of the object to be formed increases along the Z axis 216 as the process is performed. Therefore, as will be appreciated, the relative positioning of the scanning carriages 208, 210 to a top layer of build material in the build area may be approximately maintained by adjustment of the scanning carriages 208, 210 and/or the build material support 202 along the Z axis 216.

[0044] The first scanning carriage 208 of the apparatus 200 is to move along a first scanning axis mat is generally parallel to the X axis 212, and the second scanning carriage 210 is to move along a second scanning axis that is generally parallel to the Y axis 214. Furthermore, the apparatus 200 includes a first build layer sensing system 218 that comprises a first emitter 220 to emit light, a first receiver 222 to detect emitted light 222, a first deflector 224, and a second deflector 226. The first deflector 224 is to deflect light emitted by the first emitter 220 across the build area and along a first sensing axis to the second deflector 226, and the second deflector 226 is to deflect light to the first receiver 222.

[0045] FIG. 4 includes an example illustration of light emitted and detected by the first build layer sensing system 218 for illustrative purposes. As shown, light may be emitted from the first emitter 220 to the first deflector 224 along an axis mat is approximately parallel to the X axis 212. The first deflector 224 deflects light emitted by the first emitter 220 along a first sensing axis that is approximately orthogonal to the X axis 212 and approximately parallel to the Y axis 214. As shown the light deflected by the first deflector 224 spans a width of the build surface 204 along die first sensing axis - i.e., the light is deflected over the build surface 204 (and across the corresponding build area). Accordingly, as the first scanning carriage 208 moves along the first scanning axis, light deflected by the first deflector 224 may be projected across the build area (along the first sensing axis). The second deflector 226 deflects light to the first receiver 222 along an axis approximately parallel to tine first scanning axis and approximately orthogonal to the first sensing axis.

[0046] As will be appreciated, as the first scanning carriage moves along the first scanning axis over the build area of the build material support 202, build material distributed in the build area may change an intensity of light received at the first receiver 222. Some examples may therefore determine characteristics of build material of a build layer in the build area at a particular location on the first scanning axis based at least in part on an intensity of light detected by the first build layer sensing system 218 when positioned at the particular location.

[0047] In addition, the apparatus 200 comprises a second build layer sensing system 230. The second build layer sensing system 230 may comprise a second emitter 232, a second detector 234, a third deflector 236, and a fourth deflector 238. In this example, the third deflector 236 and fourth deflector 238 are coupled to the second scanning carriage 210 such mat the third deflector 236 and fourth deflector 238 may move along the second scanning axis as the second scanning carriage 210 moves along the second scanning axis. FIG.4 includes example illustrations of light that may be emitted and detected by the second build layer sensing system 230. As shown, light may be emitted by the second emitter 232 along an axis that is approximately parallel to the Y axis 214 (and the second scanning axis) to the third deflector 236. The third deflector 236 is to deflect light along a second sensing axis to the fourth deflector 238, where the second sensing axis is approximately parallel to the X axis 212 and approximately orthogonal to the second scanning axis. As shown, the light deflected by the third deflector 236 spans a width of the build surface 204 along the second sensing axis - i.e., the light is deflected over the build surface 204 (and across the corresponding build area). Accordingly, as the second scanning carriage 208 moves along the second scanning axis, light deflected by the third deflector 236 may be projected across the build area along the second sensing axis. Hie fourth deflector is to deflect light to the second receiver 234 along an axis approximately parallel to the second scanning axis and

approximately orthogonal to the second sensing axis.

[0048] in addition, the example apparatus 200 comprises a data processing subsystem 250 that includes a controller 252. In some examples, an included controller, such as the controller 252 of FIG. 4, as described herein may be any combination of hardware and programming to implement the functionalities described with respect to the controller 252. In some examples described herein, the combinations of hardware and programming may be implemented in a number of different ways. For example, the programming for the controller may be processor executable instructions stored on a non- transitory machine-readable storage medium and the hardware for the controller may include a processing resource to execute those instructions, in these examples, an apparatus implementing such controller may include the machine- readable storage medium storing the instructions and the processing resource to execute file instructions, or the machine-readable storage medium may be separately stored and accessible by the apparatus and the controller. In some examples, a controller may be implemented in circuitry.

[0049] The controller 252 of the example apparatus 200 may control movement of the scanning carriages 208, 210. In addition, the controller 252 may control emission of light by the build layer sensing systems 218, 230. In addition, the controller 252 may analyze light detected by the receivers 222, 234 to thereby determine build layer characteristics (e.g., build layer height at locations along the first scanning axis and the second scanning axis) for a layer of build material in the build area. Furthermore, in some examples, the controller 252 may control additional components of example apparatuses, such as agent distributors, build material distributors, energy sources, etc. As will be appreciated, the controller 252 may control movement of the scanning carriages 208, 210 and scanning of a layer of build material with the build layer sensing systems 218, 230. Furthermore, the controller 252 may analyze light detected by the build layer sensing systems 218, 230 to analyze a build layer

deposited/distributed on the build material support. In some examples, the controller 252 may analyze an intensity of detected light at a particular location along a scanning axis to determine a build height of build material at the particular location. Furthermore, as the build area is scanned with a build layer sensing system, the controller 252 may analyze an intensity of light

corresponding to particular locations along the scanning axis to thereby determine a build height of build material at the particular locations as well as a build layer uniformity. As will be appreciated, an intensity of detected light may correspond to a sensor response of a receiver of a build layer sensing system.

[0050] Turning now to FIG. 5, this figure provides a front view along a view plane parallel to a plane formed by the X axis 212 and the Z axis 216 of FIG. 4 that illustrates some components of the example apparatus 200 of FIG. 4. In FIG. 5, an example layer of build material 260 is on the build surface 204 of the build material support 202. Furthermore, in this example, an example representation of light 262 deflected by the third deflector 236 to the fourth deflector 238 is provided for illustrative purposes. As shown, the fight 262 is projected over the build surface 204 and across the build area. Based on characteristics of the light 262, examples may determine characteristics of the layer of build material 260. For example, a build height at locations along the second scanning axis may be determined based on an intensity of light detected when the scanning carriage (and thereby the light) are positioned at the locations. Based on the determined heights at various locations, some examples may determine a uniformity associated with a topmost build layer.

[0051 ] FIGS. 6-12 provide flowcharts that provide example sequences of operations that may be performed by an example apparatus to perform example processes and methods as described herein. In some examples, some operations included in the flowcharts may be embodied in a memory (such as the machine-readable memory 162 of FIG. 3) in the form of instructions that may be executable by a processing resource to cause an apparatus to perform the operations corresponding to the instructions. Additionally, the examples provided in FIGS. 6-12 may be embodied in computing devices, machine- readable storage mediums, processes, and/or methods. In some examples, the example processes and/or methods disclosed in the flowcharts of FIGS. 6-12 may be performed by a controller implemented in an apparatus such as the example controllers of FIG. 1 and 4.

[0052] FIG. 6 is a flowchart 300 that illustrates an example sequence of operations that may be performed by an example apparatus. In this example, a scanning carriage may be moved over a build area corresponding to a build material support along a scanning axis (block 302). As the scanning carriage moves along the scanning axis, the apparatus scans the build area along the scanning axis with a build layer sensing system (block 304). Based on scanning of a layer of build material in the build area, build layer characteristics may be determined (block 306). FIG. 7 provides a flowchart 350 that illustrates an example sequence of operations that may be performed by an example apparatus to scan a build area. In this example, a scanning carriage is moved along a scanning axis over the build area (block 352). During movement of the scanning carriage, the apparatus emits light from an emitter of a build layer sensing system along a sensing axis, where the sensing axis moves along the scanning axis with the movement of the scanning carriage over the build area (block 354). The apparatus detects emitted light during movement of the scanning carriage over the build area and over the build material support (block 356).

[0053] Turning now to FIG. 8, this figure provides a flowchart 400 that illustrates an example sequence of operations that may be performed by an example apparatus to analyze a layer of build material distributed in a build area for an additive manufacturing process. In this example, the apparatus may scan the layer of build material with a build layer sensing system along a scanning axis during movement of a scanning carriage (block 402). The apparatus analyzes light detected by the build layer sensing system to thereby analyze the layer of build material (block 406), and the apparatus may determine a build layer height at locations along the scanning axis (block 408). In some examples, analyzing detected light may comprise determining a sensor response of a receiver of the build layer sensing system for light detected when a scanning carriage and a corresponding sensing axis are at various locations along the scanning axis. In some examples, a build layer uniformity of a layer of build material in the build area may be determined (block 410). where a build layer uniformity may be based at least in part on a build layer height at locations along a scanning axis in the build area.

[0054] FIG. 9 provides a flowchart 450 mat illustrates an example sequence of operations that may be performed by an example apparatus to analyze a layer of build material distributed in a build area for an additive manufacturing process. The apparatus scans the layer of build material with a build layer sensing system as a scanning carriage moves along a scanning axis over the build area (block 452). The apparatus determines an intensity of detected light and/or a sensor response to detected light when the sensing axis is positioned at locations along the scanning axis (block 454). Based on the intensity of the detected light and/or the sensor response corresponding to locations along the scanning axis, the apparatus may determine a build layer height at locations of the scanning axis (block 456). As will be appreciated, the locations of the scanning axis correspond to locations of the build area.

[0055] Turning now to FIG. 10, this figure provides a flowchart 500 that illustrates an example sequence of operations that may be performed by an apparatus. Based on light detected during scanning of a build area by a build layer sensing system, the apparatus may determine a build layer height for locations of the build area (block 502). The apparatus analyzes the build layer height do determine whether the build layer height at any location is greater than a maximum threshold (block 504). in some examples, a maximum build layer height threshold may be defined for an apparatus. For example, for a particular apparatus, a maximum build layer height threshold may be based at least in part upon a distance needed between a scanning carriage (or a component coupled to the scanning carriage) and a layer of build material for proper operation. In response to determining that the build layer height is greater man a maximum threshold at a location of the build area/scanning axis (Ύ" branch of block 504), the apparatus may stop operation (block 506). As will be appreciated, in some examples, if build material height exceeds a maximum threshold for an apparatus, operation of the apparatus may result in damage to components of die apparatus. Accordingly, some examples may stop operation.

[0056] In response to determining that the build layer height is not greater than a maximum threshold at any location ("N" branch of block 504), the apparatus may determine whether the build layer height at any location is less than a minimum threshold (block 508). As will be appreciated, in some examples, a build layer height less than a minimum threshold at a particular location may cause a manufacturing defect in the three-dimensional object being formed in the layer-wise additive manufacturing process. Accordingly, in response to determining that a build layer height at any location is less than a minimum threshold (Ύ" branch of block 508), the example apparatus may distribute build material (block 510). Therefore, in this example, the apparatus may distribute additional build material over a first layer of build material responsive to determining that a build layer height at a location in the build area for the first build layer is below a minimum threshold. In response to

determining that the build layer height is not less than the minimum threshold ("N" branch of block 508), the apparatus may distribute agent (block 512).

Hence, if the build layer height is less than the maximum threshold and greater than the minimum threshold, this example continues with the layer-wise additive manufacturing process by distributing agent on the build layer.

[0057] FIG. 11 provides a flowchart 550 that illustrates an example sequence of operations that may be performed by an example apparatus. In this example, the apparatus may move a first scanning carriage along a first scanning axis (block 552), and, as the first scanning carriage moves along the first scanning axis, the apparatus may scan a build layer distributed in a build area with a first build layer sensing system (block 554). The example apparatus may move a second scanning carriage along a second scanning axis (block 556), and, as the second scanning carriage moves along the second scanning axis, the apparatus may scan the build layer with a second build layer sensing system (block 558). As will be appreciated, in this example, the apparatus may therefore scan the build layer along the first scanning axis and the second scanning axis.

[0058] FIG. 12 provides a flowchart 600 that illustrates an example sequence of operations that may be performed by an example apparatus. In this example, the apparatus may control movement of a first scanning carriage over a build area (block 602). in some examples, the apparatus may comprise a print engine that may control movement of the first scanning carriage.

Furthermore, the apparatus controls emission and detection of light by a first build layer sensing system (block 604). in some examples, the apparatus may comprise a print engine mat may control emission and detection of light with the first build layer sensing system. The apparatus may control movement of a second scanning carriage over the build area (block 606). In addition, the apparatus may control emission and detection of light by a second build layer sensing system (block 608). In some examples, the apparatus may comprise a print engine that may control emission and detection of light by the second build layer sensing system.

[0059] in addition, in some examples, the apparatus may perform other operations concurrent with movement of the first scanning carriage and/or second scanning carriage. For example, the apparatus may distribute agent concurrent with movement of a scanning carriage. Therefore, in such examples, the apparatus and/or a processing resource/engine thereof may control an agent distributor concurrent with controlling movement of the scanning carriage. As another example, the apparatus may distribute build material concurrent with movement of a scanning carriage. In these examples, the apparatus and/or a processing resource/engine thereof may control a build material distributor concurrent with controlling movement of the scanning carriage.

[0060] FIG. 13A provides an example chart 650 that illustrates an example relationship between a build layer height 652 and a sensor response 654. Accordingly, in some examples, a response of a receiver of a build layer sensing system may be analyzed to determine a build layer height. As will be appreciated, the sensor response may correspond to an intensity of light detected by the receiver. FIG. 13B provides an example chart 670 that illustrates example locations 672 and an example measured sensor response 674 at the example locations 672. As will be appreciated, the example locations may correspond to a location of a build area. For example, the example locations may correspond to distances from a set point (e.g., inches from an edge of the build area along a scanning axis). In this particular example, the example chart 670 illustrates that a lower build material height may be present at the 2.5 location in the build area.

[0061] Therefore, example apparatuses and processes described herein facilitate analysis of build material in a build area with at least one build layer sensing system. In some examples, the build layer sensing system emits light that may be projected across the build area along a sensing axis. To scan the build area, examples may cause the projected light to move along a scanning axis that is approximately orthogonal to the sensing axis. Examples described herein may analyze light detected by the build layer sensing system (after such light is projected across the build area along the sensing axis) to thereby determine characteristics of build material deposited in the build area. In some examples, a build height of a layer of build material may be determined at locations of the build area, in some examples, a uniformity of build height may be determined for a layer of build material in the build area. As described herein, some examples may perform various operations based at least in part on a determined build height and/or determined uniformity.

[0062] The preceding description has been presented to illustrate and describe examples of the principles described. This description is not intended to be exhaustive or to limit these principles to any precise form disclosed. Many modifications and variations are possible in light of the above disclosure.

Claims

CLAIMS: 1. An apparatus for generating a three-dimensional object:

a first scanning carriage to move along a first scanning axis over a build area;

a first build layer sensing system comprising:

a first emitter to emit light over the build area along a first sensing axis that is orthogonal to the first scanning axis, wherein light emitted by the first emitter is to move with movement of the first scanning carriage along the first scanning axis;

a first receiver to detect light emitted by the first emitter over the build area; and

a controller to analyze light detected by the first receiver to thereby determine build layer characteristics of a build layer distributed in the build area.

2. The apparatus of claim 1 , wherein the controller is further to control movement of the first scanning carriage along the first scanning axis.

3. The apparatus of claim 2, wherein the controller is to determine a build layer height at locations along the first scanning axis.

4. The apparatus of claim 1 , wherein the first build layer sensing system further comprises;

a first light deflector coupled to the first scanning carriage;

a second light deflector coupled to the first scanning carriage,

wherein the first emitter is to emit light parallel to the first scanning axis to the first light deflector, the first light deflector is to deflect emitted light along the first sensing axis to the second light deflector, and the second light deflector is to deflect emitted light parallel to the first scanning axis to the first receiver

5. The apparatus of claim 1, further comprising:

a second scanning carriage to move along a second scanning axis that is orthogonal to the first scanning axis;

a second build layer sensing system comprising:

a second emitter to emit light over the build material support along a second sensing axis that is orthogonal to the second scanning axis, wherein light emitted by the second emitter is to move with movement of the second scanning carriage along the second scanning axis; and

a second receiver to detect light emitted by the second emitter over the build material support.

6. The apparatus of claim 5,

wherein the first build layer sensing system further comprises:

a first light deflector coupled to the first scanning carriage;

a second light deflector coupled to the first scanning carriage, wherein the first emitter is to emit light parallel to the first scanning axis to the first light deflector, the first light deflector is to deflect emitted light along the first sensing axis to the second light deflector, and the second light deflector is to deflect emitted light parallel to the first scanning axis to the first receiver; and wherein the second build layer sensing system further comprises:

a third light deflector coupled to the second scanning carriage; a fourth light deflector coupled to the second scanning carriage, wherein the second emitter is to emit light parallel to the second scanning axis to the third light deflector, the third light deflector is to deflect emitted light along the second sensing axis to the fourth light deflector, and the fourth light deflector is to deflect emitted light parallel to the second scanning axis to the second receiver.

7. The apparatus of claim 5, wherein the controller is further to:

control movement of the first scanning carnage along the first scanning axis;

control movement of the second scanning carriage along the second scanning axis; and

analyze light detected by the second receiver to thereby determine build layer characteristics of the build layer distributed in the build area.

8. The apparatus of claim 5,

wherein the first scanning carriage comprises an agent distributor to distribute an agent in a build area of the build material support, and the second scanning carriage comprises a build material distributor to distribute a build material in the build area of the build material support as the second scanning carriage moves over the build material support.

9. A method for an apparatus for generating a three-dimensional object comprising:

moving a first scanning carriage through a build area of a build material support of file apparatus along a first scanning axis; and

scanning the build area of the build material support with a first build layer sensing system as the first scanning carriage moves through the build area; and

determining build layer characteristics of a build layer distributed in the build area based at least in part on the scanning of the build area with the first build layer sensing system,

10. The method of claim 10, wherein scanning the build area of the build material support with the first build layer sensing system comprises:

detecting, with a first receiver, light emitted along a first sensing axis from a first emitter, wherein the light emitted from the first emitter moves along the first scanning axis with the movement of the first scanning carriage, and the first sensing axis is orthogonal to the first scanning axis.

11. The method of claim 9, wherein determining build layer characteristics of the build layer comprises determining a build layer height for the build layer, and the method further comprises:

responsive to the build layer height being greater than a maximum threshold, stopping operation of the apparatus;

responsive to the build layer height being less than a minimum threshold, distributing build material prior to distributing agent.

12. The method of claim 9, further comprising:

moving a second scanning carriage over the build area of the build material support along a second scanning axis; and

scanning the build area of the build material support with a second build layer sensing system as the second scanning carriage moves over the build area,

wherein determining the build layer characteristics is based at least in part on te scanning of the build area with the second build layer sensing system.

13. An apparatus tor generating a three-dimensional object comprising: a first scanning carriage to move over a build area of the build material support along a first scanning axis;

a second scanning carriage to move over the build area of the build material support along a second scanning axis that is orthogonal to the first scanning axis;

a first build layer sensing system to emit light across the build area and along a first sensing axis that is orthogonal to the first scanning axis, and the first build layer sensing system to detect light emitted along the first sensing axis, wherein light emitted by the first build layer sensing system is to move along the first scanning axis as the first scanning carriage moves along the first scanning axis; and

a second build layer sensing system to emit light across the build area and along a second sensing axis that is orthogonal to the second scanning axis, and the second build layer sensing system is to detect light emitted along the second sensing axis, wherein light emitted by the first build layer sensing system is to move along the second scanning axis as the second scanning carriage moves along the second scanning axis.

14. The apparatus of claim 13, further comprising:

a controller to:

control movement of the first scanning carriage over the build area;

control emission of light of emitted light by the first build layer sensing system;

control movement of the second scanning carriage over the build area;

control emission of light of emitted light by the second build layer sensing system.

15. The apparatus of claim 13, wherein the first build layer sensing system comprises a first light deflector coupled to the first scanning carriage to deflect fight emitted by the first build layer sensing system, and the second build layer sensing system comprises a second light deflector coupled to the second scanning carriage to deflect light emitted by the second build layer sensing system.