WO2016209233A1

WO2016209233A1 - Reflecting radiation from three-dimensional object build material to sensors

Info

Publication number: WO2016209233A1
Application number: PCT/US2015/037606
Authority: WO
Inventors: Miguel Angel LOPEZ
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2015-06-25
Filing date: 2015-06-25
Publication date: 2016-12-29

Abstract

In some examples, a sensor may be to detect radiation. A reflector may be to reflect the radiation from build material to be on a support member to the sensor. The build material may be used to generate a three-dimensional object. A controller may be to receive data representing the radiation from the sensor.

Description

REFLECTING RADIATION F OM THREE-DIMENSIONAL OBJECT BUILD

MATERIAL TO SENSORS

BACKGROUND

[0001] Additive manufacturing systems that generate three-dimensional objects on a layer-by-layer basis have been proposed as a potentially convenient way to produce three-dimensional objects. The quality of objects produced by such systems may vary widely depending on the type of additive manufacturing technology used.

BRIEF DESCRIPTION

Some examples are described with respect to the following figures:

[0002] FIG. 1 illustrates an additive manufacturing system according to some examples;

[0003] FIG. 2 is a flow diagram illustrating a method according to some examples;

[0004] FIG. 3 is a block diagram illustrating a non-transitory computer readable storage medium according to some examples;

[0005] FIG. 4a is a simplified isometric illustration of an additive manufacturing system according to some examples;

[0006] FIG. 4b is a simplified schematic side view of an assembly including an agent distributor, sensor, and reflector according to some examples;

[0007] FIG. 5 is a simplified schematic side view of an assembly including an agent distributor, sensor, and reflector according to some examples;

[0008] FIG. 6 is a flow diagram illustrating a method of generating a three-dimensional object according to some examples; and

[0009] FIGS. 7a-d show a series of cross-sectional side views of layers of build material according to some examples.

[00010] The following terminology is understood to mean the following when recited by the specification or the claims. The singular forms "a," "an," and "the" mean "one or more." The terms "including" and "having" are intended to have the same inclusive meaning as the term "comprising."

[00011] Some additive manufacturing systems generate three-dimensional objects through the solidification of portions of successive layers of build material, such as a powdered, liquid, or fluidic build material. The properties of generated objects may be dependent on the type of build material and the type of solidification mechanism used. In some examples, solidification may be achieved by using an agent distributor to deliver a binder agent which binds and solidifies build material into a binder matrix, which is a mixture of generally separate particles or masses of build material that are adhesively bound together by a binder agent. In other examples, solidification may be achieved by temporary application of energy to the build material using an agent distributor. This may, for example, involve use of a coalescing agent, which is a material that, when a suitable amount of energy is applied to a combination of build material and coalescing agent, may cause the build material to coalesce and solidify. In some examples, a multiple agent additive manufacturing system may be used such as that described in PCT Application No. PCT/EP2014/050841 filed on January 16, 2014, entitled "GENERATING A THREE-DIMENSIONAL OBJECT", the entire contents of which are hereby incorporated herein by reference. For example, in addition to selectively delivering coalescing agent to layers build material, coalescence modifier agent may also be selectively delivered to layers of build material. A coalescence modifier agent may serve to modify the degree of coalescence of a portion of build material on which the coalescence modifier agent has been delivered or has penetrated, in yet other examples, other methods of solidification may be used, for example selective laser sintering (SLS), light polymerization, among others. The examples described herein may be used with any of the above additive manufacturing systems and suitable adaptations thereof.

[00012] However, aspects of the build process may not proceed as intended. An aspect of the additive manufacturing system such as an agent distributor may be misaligned, causing agents to be delivered in incorrect areas of build material on a support member, in some examples, temperature irregularities may appear throughout the build material while generating the three-dimensional object. Since accurate object generation may depend on maintaining build material temperatures within a narrow window, temperature irregularities may result in generated objects not being faithful reproductions of three-dimensional object models used to generate the objects.

[00013] Therefore, in some examples, a sensor may be used to provide feedback on temperatures of layers of build material during the build process. The feedback may then be used to modulate aspects of the build process so as to achieve desired object dimensions and properties, or cancel generation of the object before completing the object. However, due to high temperatures, for example about 180 degrees Celsius or more, achieved in additive manufacturing systems near the build material on the support member, the sensor may become damaged or malfunction if the sensor is placed near the build materia!.

[00014] Accordingly, the present disclosure provides a reflector that reflects radiation from the build material towards a sensor for detection. The detected radiation may be used to determine temperatures of the build material. In some examples, using the reflector may allow the sensor to be placed in a location shielded from the high temperatures near the build material. For example, the sensor may be placed on a top side of a carriage facing away from the build material, or may be placed in a location laterally distant from the build material. In some examples, these locations may experience lower temperatures, for examples 80 degrees Celsius, resulting in superior function of the sensor. Additionally, in some examples, the sensor can be made without using temperature resistant materials, thereby reducing cost.

[00015] FIG. 1 is a block diagram illustrating an additive manufacturing system 100 according to some examples. The additive manufacturing system 100 may include a sensor 102 to detect radiation. The additive manufacturing system 100 may include a reflector 104 to reflect the radiation from build material to be on a support member to the sensor. The build material may be used to generate a three-dimensional object. The additive manufacturing system 100 may include a controller 106 to receive data representing the radiation from the sensor.

[00016] FIG. 2 is a flow diagram illustrating a method 1 10 according to some examples. At 1 12, radiation from build material on a support member may be reflected by a mirror or a prism to a sensor while generating a three-dimensional object using the build material. At 1 14, the reflected radiation may be captured using the sensor. At 1 16, data representing the detected radiation may be provided to a controller. At 1 18, the generation of the three-dimensional object may be modified based on the data.

[00017] FIG. 3 is a block diagram illustrating an additive manufacturing system 120 according to some examples. The additive manufacturing system 120 may include a support member 122 to hold build material to be used in a build process to generate a three-dimensional object. The additive manufacturing system 120 may include a sensor 124 to capture radiation comprising infra-red radiation or visible light from the build material. The sensor 124 may be in a first region 126 of the additive manufacturing system 120. The additive manufacturing system 120 may include a mirror or a prism 128 to reflect the radiation from the build material to be held on a support member to the sensor. The mirror or the prism 128 may be in a second region 130 of the additive manufacturing system 120. The second region 130 may have a higher average temperature during the build process than the first region 126.

[00018] FIG. 4a is a simplified isometric illustration of an additive manufacturing system 200 according to some examples. FIG. 4b is a simplified schematic side view of an assembly 234 including an agent distributor 202, sensor 228, and reflector 220 according to some examples. The system 200 may be operated, as described further below with reference to the flo diagram of FIG. 6 to generate a three-dimensional object.

[00019] In some examples the build material may be a powder-based build material. As used herein the term powder-based materials is intended to encompass both dry and wet powder-based materials, particulate materials, granular, and fiuidic materials. In some examples, the build material may include a mixture of air and solid polymer particles, for example at a ratio of about 40% air and about 60% solid polymer particles. One suitable material may be Nylon 12, which is available, for example, from Sigma-A!drich Co. LLC. Another suitable Nylon 12 material may be PA 2200 which is available from Electro Optical Systems EOS GmbH. Other examples of suitable build materials may include, for example, powdered metal materials, powdered composite materials, powdered ceramic materials, powdered glass materials, powdered resin material, powdered polymer materials, and the like, and combinations thereof. It should be understood, however, that the examples described herein are not limited to powder-based materials or to any of the materials listed above. In other examples the build material may be in the form of a paste, liquid or a gel. According to one example a suitable build material may be a powdered semi-crystalline thermoplastic material.

[00020] The additive manufacturing system 20(3 may include a system controller 210. Any of the operations and methods disclosed herein (e.g. in FIG. 6) may be implemented and controlled in the additive manufacturing system 200 and/or controller 210. A controller, as understood herein, comprises (1 ) a non-transitory computer- readable storage medium comprising instructions to perform operations and methods disclosed herein, and a processor coupled to the non-transitory computer-readable storage medium to execute the instructions; or comprises (2) circuitry to perform the operations and methods disclosed herein.

[00021] The controller 210 may include a processor 212 for executing instructions that may implement the methods described herein. The processor 212 may, for example, be a microprocessor, a microcontroller, a programmable gate array, an application specific integrated circuit (ASIC), a computer processor, or the like. The processor 212 may, for example, include multiple cores on a chip, multiple cores across multiple chips, multiple cores across multiple devices, or combinations thereof. In some examples, the processor 212 may include at least one integrated circuit (IC), other control logic, other electronic circuits, or combinations thereof.

[00022] in some examples, the controller 210 may support direct user interaction. For example, the additive manufacturing system 200 may include user input devices coupled to the processor 212, such as a keyboard, touchpad, buttons, keypad, dials, mouse, track-bail, card reader, or other input devices. Additionally, the additive manufacturing system 200 may include output devices coupled to the processor 212, such as a liquid crystal display (LCD), video monitor, touch screen display, a light- emitting diode (LED), or other output devices. The output devices may be responsive to instructions to display textual information or graphical data.

[00023] The processor 212 may be in communication with a computer-readable storage medium 216 via a communication bus. The computer-readable storage medium 216 may include a single medium or multiple media. For example, the computer readable storage medium 216 may include one or both of a memory of the ASIC, and a separate memory in the controller 210. The computer readable storage medium 216 may be any electronic, magnetic, optical, or other physical storage device. For example, the computer-readable storage medium 216 may be, for example, random access memory (RAM), static memory, read only memory, an electrically erasable programmable read-only memory (EEPROM), a hard drive, an optical drive, a storage drive, a CD, a DVD, and the like. The computer-readable storage medium 216 may be non-transitory. The computer-readable storage medium 216 may store, encode, or carry computer executable instructions 218 that, when executed by the processor 212, may cause the processor 212 to perform any of the methods or operations disclosed herein according to various examples. [00024] in other examples, the controller 210 may not include a computer-readable storage medium 216, and the processor may comprise circuitry to perform any of the methods or operations disclosed herein without executing separate instructions in a computer-readable storage medium.

[00025] As shown in FIGS. 4a-b, the system 200 may include an agent distributor 202 to selectively deliver coalescing agent to successive layers of build material provided on a support member 204. According to one non-limiting example, a suitable coalescing agent may be an ink-type formulation comprising carbon black, such as, for example, the ink formulation commercially known as CM997A available from Hewlett-Packard Company. In one example such an ink may additionally comprise an infra-red light absorber. In one example such an ink may additionally comprise a near infra-red light absorber, in one example such an ink may additionally comprise a visible light absorber, in one example such an ink may additionally comprise a UV light absorber. Examples of inks comprising visible light enhancers are dye based colored ink and pigment based colored ink, such as inks commercially known as CM993A and CE042A available from Hewlett-Packard Company.

[00028] Although the description of agent distributor 202 is described herein as delivering coalescing agent, it is understood that in some examples, binder agent may be delivered by the agent distributor 202 rather than coalescing agent. Thus, the term "agent" is understood to encompass both coalescing agent and binder agent.

[00027] The controller 210 may control the selective delivery of coalescing agent to a layer of provided build material in accordance with the instructions 218.

[00028] The agent distributor 202 may be a printhead, such as a thermal Inkjet printhead or a piezo Inkjet printhead. The printhead may have arrays of nozzles, in one example, printheads such as those commonly used in commercially available Inkjet printers may be used. In other examples, the agents may be delivered through spray nozzles rather than through printheads. Other delivery mechanisms may be used as well. The agent distributor 202 may be used to selectively deliver, e.g. deposit, coalescing agent when in the form of suitable fluids such as a liquid.

[00029] The coalescing agent distributor 202 may include a supply of coalescing agent or may be connectabie to a separate supply of coalescing agent.

[00030] The agent distributor 202 may be used to selectively deliver, e.g. deposit, coalescing agent when in the form of a suitable fluid such as liquid, in some examples, the agent distributor 202 may have an array of nozzles through which the agent distributor 202 is able to selectively eject drops of fluid. In some examples, each drop may be in the order of about 10 pico liters (pi) per drop, although in other examples the agent distributor 202 is able to deliver a higher or lower drop size. In some examples the agent distributor 202 is able to deliver variable size drops.

[00031] In some examples the coalescing agent may comprise a liquid carrier, such as water or any other suitable solvent or dispersant, to enable it to be delivered via a printhead.

[00032] in some examples the printheads may be drop-on-demand printhead. in other examples the printhead may be continuous drop printhead.

[00033] In some examples, the agent distributor 202 may be an integral part of the system 200. In some examples, the agent distributor 202 may be user replaceable, in which case they may be removably insertable into a suitable agent distributor receiver or interface module of the system 200.

[00034] In the example illustrated in FIGS. 4a-b, the agent distributor 202 may have a length that enables it to span the whole width of the support member 204 in a so-called page-wide array configuration. In one example this may be achieved through a suitable arrangement of multiple printheads. in other examples a single printhead having an array of nozzles having a length to enable them to span the width of the support member 204 may be used, in other examples, the agent distributor 202 may have a shorter length that does not enable it to span the whole width of the support member 204.

[00035] The agent distributor 202 may be mounted on a moveable carriage 206 to enable it to move bi-directionally across the length of the support member 204 along the illustrated y-axis. Although FIG. 2 shows an end of the agent distributor 202, the agent distributor 202 may extend the same length across the x-axis as the carriage 206, such that the agent distributor 202 spans the width along the x-axis of the support member 208. This enables selective delivery of coalescing agent across the whole width and length of the support 204 in a single pass. In other examples the agent distributor 202 may be fixed, and the support member 204 may move relative to the agent distributor 202.

[00036] in other examples the agent distributors may be fixed, and the support member 204 may move relative to the agent distributors. [00037] It should be noted that the term 'width' used herein is used to generally denote the shortest dimension in the plane parallel to the x and y axes illustrated in FIG. 4a, whilst the term length' used herein is used to generally denote the longest dimension in this plane. However, it will be understood that in other examples the term 'width' may be interchangeable with the term length'. For example, in other examples the agent distributor 202 may have a length that enables them to span the whole length of the support member 204 whilst the moveable carriage 206 may move bi- directionally across the width of the support member 204.

[00038] in another example the agent distributor 202 does not have a length that enables it to span the whole width of the support member but are additionally movable bi-directionally across the width of the support member 204 in the illustrated x-axis. This configuration enables selective delivery of coalescing agent across the whole width and length of the support 204 using multiple passes. Other configurations, however, such as a page-wide array configuration, may enable three-dimensional objects to be created faster.

[00039] The system 200 may additionally include a sensor 228 for radiation. In some examples, the sensor 228 may be an imaging device to capture optical images of the build material. The images may, in some examples, be captured in the visible light range, however in some examples the radiation may be outside of the visible light range, in some examples, the sensor 228 may be a 2D camera, a scanning bar, a 1 D camera, or a line camera. The sensor 228 may output data representing the detected radiation (and therefore the image) to the controller 210.

[00040] in some examples, the sensor 228 may be to detect temperature in the system 200, such as a temperature of the build material. In some examples, the sensor 228 may be to capture radiation 238 from the build material, in some examples, the sensor 228 may be a thermographic camera. However, any other suitable sensors may be used to capture radiation 238 that may be used to infer temperature. In some examples, the sensor 228 may be to capture a wavelength distribution of radiation 238, for example in the IR range, emitted by each point of the build material across the area spanned by the build material on the support member 204. The sensor 228 may output data representing the wavelength distribution of radiation 238 to the controller 210, which may determine a temperature for each area across the build material based on known relationships, such as a black body distribution, between temperature and radiation intensity at different wavelengths of the distribution for the material used as the build material. For example, the distribution of radiation 238 may have its highest intensities at particular wavelength values in the infra-red (IR) range. Each temperature may correspond to a particular area of the build material, wherein each of the areas collectively define an entire area of the build material print bed. in some examples, a processor in the sensor 228 may be determine the temperatures rather than the controller 210.

[00041] in some examples, an array of sensors 228 may be used instead of a single sensor 228. For example, multiple sensors 228 (e.g. two, three, four, or more) may be lined up across the length of the carriage 206 along the x-axis. in some examples, radiation data from different sensors 228 may be collected from different regions of the build material, such that the radiation data from all of the sensors 228 may allow for determining temperature across the entire area of build material.

[00042] As shown in FIGS. 4a-b, the sensor 228 may be coupled (e.g. directly coupled and/or rigidly coupled) to the carriage 206, and may be oriented to face along the x- axis. The sensor 228 may thus be coupled to the agent distributor 202 indirectly through the carriage 206. The term "coupled" therefore is meant to encompass both direct and indirect coupling, in some examples, the sensor 228 may instead be directly coupled to the agent distributor 202.

[00043] in some examples, a protective cover 214 may be disposed over the sensor 228 to shield the sensor 228 from high temperatures in the system 200. The protective cover 228 may be coupled directly to the carriage 206 and indirectly to agent distributor 202 using the arm 236. In FIG. 4a, the cover 228 is shown as transparent with dashed lines to allow visualization of the sensor 228 which is underneath the cover 214.

[00044] A platform 222 may be coupled (e.g. directly coupled and/or rigidly coupled) to the carriage 206 and indirectly to the agent distributor 202 indirectly through the carriage 206. In some examples, the platform 222 may instead be directly coupled to the agent distributor 202. The platform may include an opening 208. The opening 208 may be a square shape, as shown, but in other examples the opening 208 may have other shapes.

[00045] A reflector 220 may be coupled (e.g. directly coupled and/or rigidly coupled) to the platform 222, and therefore indirectly coupled to the carriage 206 and agent distributor 202. As understood herein, a "reflector" may be any object, e.g. made of glass, metal, and/or other materials, that is used for reflecting radiation 238.

[00048] In some examples, the reflector 220 may be a lens, a mirror such as glass, silver, or gold mirror, or an aluminum mirror that e.g. lacks a protective glass cover, in some examples, the mirror may be a first surface mirror, in some examples, the reflector 220 may be a prism such as a glass, plastic, or fiuorite prism, or an Amici roof prism. In some examples, a prism may, for example, be to reflect radiation 238 as a perfect mirror using total internal reflection. In some examples, the reflector 220 may be a parabolic reflector. In other examples, other types of reflectors may be used, for example any type of reflector that is suitable for surviving high temperatures achieved in the system 200 near the build material, such as 180 degrees Celsius. In some examples, multiple reflectors 234 may be used, for example each reflector 220 may be attached to a different platform 222. in some examples, when multiple sensors 228 are used, each sensor 228 may be to receive reflected radiation 238 from a respective one of the reflectors 234.

[00047] in some examples, the sensor 228, platform 222, and reflector 220 may be oriented along a line across the y-axis as shown in FIG. 4a. In other examples, the sensor 228, platform 222, and reflector 220 may instead be oriented along a line across the x-axis on the carriage 206, rotated 90 degrees relative to the configuration of FIG. 4a.

[00048] in some examples, as shown in FIGS. 4a-b, the sensor 228 may be placed close to an edge on the carriage 208 in a position close to the reflector 220 along the y-axis to improve collection of radiation 238 from the reflector 220. Placing the sensor 228 in this position relative to, for example, on the center of the carriage 206, may allow the reflector 220 to be smaller but still reflect sufficient radiation 238 to the sensor 228.

[00049] The reflector 220 may be oriented at any suitable angle relative to the platform 222 and the y-axis, for example an acute angle such as about 45 degrees as shown in FIGS. 4a-b. In some examples, the reflector 220 may be an articulating object such that the reflector 220 is movable between different angles (e.g. different acute angles) relative to the platform 222, for example using a hinge or other coupling device that may couple the platform 222 to the reflector 220. [00050] in some examples, radiation 238 from build material formed on the support member 204 may be received by the reflector 220, which may reflect the radiation 238 toward to the sensor 228.

[00051] In some examples, the entire area of the build material may be scanned by the sensor 228 by articulating the reflector 220 between different angles while keeping the carriage 206 stationary. At each angle, radiation 238 from different areas of build material may be reflected from the build material to the sensor 228 until ail areas of the build material are scanned.

[00052] In some examples, the entire area of the build material may be scanned by the sensor 228 by moving the carriage 206 across the y-axis over the length of the support member, without articulating the reflector 220. As the carriage 206 may move, the reflector 220 may receive radiation 238 from different areas of the build material, until all areas of build material are covered once the carriage 206 completes its motion across the support member 204. In some examples, scanning by the sensor 228 may occur while the agent distributor 202 delivers agent as the carriage 206 moves across the support member 206.

[00053] In some examples, the entire area of the build material may be scanned by the sensor 228 using a combination of articulation of the reflector 220 and movement of the carriage 206.

[00054] FIG. 5 is a simplified schematic side view of an assembly 300 including an agent distributor 302, sensor 328, and reflector 320 according to some examples. In some examples, the assembly 300 may be used in the system 200 rather than the assembly 234 of FIG. 4b. In some examples, the carriage 306, agent distributor 302, reflector 320, and sensor 328 may be similar to the carriage 206, agent distributor 202, reflector 220, and sensor 228.

[00055] In some examples, the reflector 320 may be coupled (e.g. directly coupled and/or rigidly coupled) to the carriage 306, and therefore indirectly coupled to the agent distributor 302. in some examples, the reflector 320 may be directly coupled to the agent distributor 302.

[00056] The reflector 320 may be oriented at any suitable angle relative to the y-axis and the bottom surface of the agent distributor 302 and carriage 306, for example an acute angle such as about 45 degrees as shown in FIG. 5. In some examples, the reflector 320 may be an articulating object such that the reflector 320 is movable between different angles (e.g. different acute angles) relative to the y-axis, for example using a hinge or other coupling device that may couple the carriage 306 to the reflector 220.

[00057] In some examples, as shown in FIG. 5, the sensor 328 may be spaced away from the carriage 306 and the agent distributor 302 along the y-axis to protect the sensor 328 from high temperatures near the build material, support member 204, energy source 226, and heater 230. The sensor 328 may be coupled (e.g. directly coupled and/or rigidly coupled) to the carriage 306 via an arm 340, and therefore indirectly coupled to the agent distributor 302. In some examples, the sensor 328 may be directly coupled to the agent distributor 306. The arm 340 may be about 12 to 15 centimeters in length. The arm 340 may extend in the y-axis direction and in the z-axis direction as shown, such that the sensor 328 can receive radiation 238 reflected by the reflector 320. As shown in FIG. 5, the arm 340 may extend a greater distance in the y-axis direction than in the z-axis direction.

[00058] in some examples, the entire area of the build material may be scanned by the sensor 328 by articulating the reflector 320 between different angles while keeping the carriage 306 stationary. At each angle, radiation 238 from different areas of build material may be reflected from the build material to the sensor 328 until all areas of the build material are scanned.

[00059] in some examples, the entire area of the build material may be scanned by the sensor 328 by moving the carriage 306 across the y-axis over the length of the support member, without articulating the reflector 320. As the carriage 306 may move, the reflector 320 may receive radiation 238 from different areas of the build material, until all areas of build materia! are covered once the carriage 306 completes its motion across the support member 204. In some examples, scanning by the sensor 328 may occur while the agent distributor 302 delivers agent as the carriage 306 moves across the support member 306.

[00060] in some examples, the entire area of the build materia! may be scanned by the sensor 328 using a combination of articulation of the reflector 320 and movement of the carriage 306.

[00061] In some examples, for the assembly 234 of FIG. 4a-b or the assembly 300 of F!G. 5, the reflector 220 or 230 may be a first region of the additive manufacturing system 200 that experiences a first average temperature while generating the fhree- dimensional object, wherein the sensor 228 or 328 may be in a second region of the additive manufacturing system 200 that experiences a second average temperature while generating the three-dimensional object. The first average temperature may be greater than the second average temperature. An "average temperature" is an average of temperatures experienced during the interval between starting generation of the object and end generation of the object. Thus, due to the configurations of assembly 234 or 300, the sensor 228 or 328 may be subjected to lower temperatures than if it was placed in the first region having the reflector 220 or 320. This may, for example, enhance performance and lifetime of the sensor 228 and 328.

[00062] Turning back to FIG. 4a, the system 200 may further comprise a build material distributor 224 to form successive layers of build material on the support member 204. Suitable build material distributors 224 may include, for example, a wiper blade and a roller. Build material may be supplied to the build material distributor 224 from a hopper or build material store, in the example shown the build material distributor 224 moves across the width (x-axis) of the support member 204 to form a layer of build material. As previously described, a layer of build material may be formed on the support member 204, whereas subsequent layers of build material will be deposited on a previously deposited layer of build material. The build material distributor 224 may be a fixed part of the system 200, or may not be a fixed part of the system 200, instead being, for example, a part of a removable module, in some examples, the build material distributor 224 may be mounted on a carriage.

[00063] in some examples, the thickness of each layer may have a value selected from the range of between about 50 to about 3(30 microns, or about 9(3 to about 1 10 microns, or about 250 microns, although in other examples thinner or thicker layers of build material may be provided. The thickness may be controlled by the controller 210, for example based on the instructions 218.

[00064] in some examples, there may be any number of additional agent distributors and build material distributors, in some examples, the some distributors of system 200 may be located on the same carriage, either adjacent to each other or separated by a short distance. In other examples, two or more carriages each may contain a distributor. For example, each distributor may be located in its own separate carriage. Any additional distributors may have similar features as those discussed earlier with reference to the agent distributor 202. However, in some examples, different agent distributors may deliver different coalescing agents and/or coalescence modifier agents, for example.

[00065] In the example shown the support 204 is moveable in the z-axis such that as new layers of build materia! are deposited a predetermined gap is maintained between the surface of the most recently deposited layer of build material and lower surface of the agent distributor 202. In other examples, however, the support 204 may not be movable in the z-axis and the agent distributor 202 may be movable in the z-axis.

[00066] The system 200 may additionally include an energy source 226 to apply energy to build material to cause the solidification of portions of the build material according to where coalescing agent has been delivered or has penetrated. In some examples, the energy source 228 is an infra-red (IR) radiation source, near infra-red radiation source, halogen radiation source, or a light emitting diode. In some examples, the energy source 228 may be a single energy source that is able to uniformly apply energy to build material deposited on the support 204. In some examples, the energy source 226 may comprise an array of energy sources.

[00067] in other examples, the energy source 226 may be to apply energy in a substantially uniform manner to a portion of the whole surface of a layer of build material. For example, the energy source 226 may be to apply energy to a strip of the whole surface of a layer of build material. In these examples, as shown in FIG. 4a, the energy source may be moved or scanned across the layer of build material, e.g. along the x-axis, such that a substantially equal amount of energy is ultimately applied across the whole surface of a layer of build material.

[00068] in some examples, the energy source 226 may be to apply energy in a substantially uniform manner to the whole surface of a layer of build material. In these examples the energy source 226 may be said to be an unfocused energy source. In these examples, a whole layer may have energy applied thereto simultaneously, which may help increase the speed at which a three-dimensional object may be generated.

[00069] in some examples, the energy source 226 may be mounted on a moveable carriage, for example the same carriage on which the build material distributor 224 is mounted.

[00070] In other examples, the energy source 228 may apply a variable amount of energy as it is moved across the layer of build material, for example in accordance with instructions 218. For example, the controller 210 may control the energy source to apply energy to portions of build material on which coalescing agent has been applied but not to portions of build material on which coalescing agent has not been applied.

[00071] In further examples, the energy source 226 may be a focused energy source, such as a laser beam. In this example the laser beam may be controlled to scan across the whole or a portion of a layer of build material. In these examples the laser beam may be controlled to scan across a layer of build material in accordance with agent delivery control data. For example, the laser beam may be controlled to apply energy to those portions of a layer of on which coalescing agent is delivered.

[00072] The combination of the energy supplied, the build material, and the coalescing agent may be selected such that portions of the build material on which no coalescing agent have been delivered do not coalesce when energy is temporarily applied thereto, and portions of the build material on which coalescing agent has been delivered or has penetrated coalesce when energy is temporarily applied thereto do coalesce.

[00073] The system 200 may additionally include a heater 230 to emit heat to maintain build material deposited on the support 204 within a predetermined temperature range. The heater 230 may have any suitable configuration. The heater 230 may have an array of heating units 232, as shown in FIG. 4a. The heating units 232 may be each be any suitable heating unit, for example a heat lamp such as an infra-red lamp. The heating units 232 may have any suitable shapes or configurations such as rectangular, circular, rod shaped, or bulb shaped, for example. The configuration may be optimized to provide a homogeneous heat distribution toward the area spanned by the build material. Each heating unit 232, or groups of heating units 232, may have an adjustable current or voltage supply to variably control the local energy density applied to the build material surface.

[00074] Each heating unit 232 may correspond to its own respective area of the build material, such that each heating unit 232 may emit heat substantially toward its own area rather than areas covered by other heating units 232. For example, each of the sixteen heating units 232 may heat one of sixteen different areas of the build material, where the sixteen areas collectively cover the entire area of the build material. However, in some examples, each heating unit 232 may also emit, to a lesser extent, some heat which influences an adjacent area. [00075] in some examples, a heater separate from the heater 320 may be provided below the platen of the support member 204 to conductively heat the support member 204 and thereby the build material. The conductive heater may be to uniformly heat the build material across its area on the support member 204,

[00076] FIG. 6 Is a flow diagram illustrating a method 400 of generating a three- dimensional object according to some examples. In some examples, the orderings shown may be varied, some elements may occur simultaneously, some elements may be added, and some elements may be omitted. In describing FIG. 6, reference will be made to FIGS. 4a-b, 5 and 7a-d. FIGS. 7a-d show a series of cross-sectional side views of layers of build material according to some examples.

[00077] At 402, the controller 210 may obtain or generate agent delivery control data which may define for each slice of the three-dimensional object to be generated the portions or the locations on the build material, if any, at which agent is to be delivered. The agent delivery control data may be stored as part of the instructions 218.

[00078] In some examples, the agent delivery control data may be generated based on object design data representing a three-dimensional model of an object to be generated, and/or from object property data representing properties of the object. The model may define the solid portions of the object, and may be processed by the three- dimensional object processing system to generate slices of parallel planes of the model. Each slice may define a portion of a respective layer of build material that is to be solidified by the additive manufacturing system 200. The object property data may define properties of the object such as density, surface roughness, strength, and the like.

[00079] The object design data and object property data may be received, for example, as input from a user via an input device, from a software driver, from a software application such as a computer aided design (CAD) application, or may be obtained from a memory storing default or user-defined object design data and object property data.

[00080] The agent delivery control data may describe, for each layer of build material to be processed, locations or portions on the build material at which coalescing agent is to be delivered. In one example the locations or portions of the build materia! at which coalescing agent is to be delivered are defined by way of respective patterns. [00081] At 404, detection of radiation from the buiid material may begin. Radiation 238 may be received from the layer 402b of build material by the reflector 220 or 320, which may reflect the radiation 238 such that the reflected radiation 238 may be received and detected by the sensor 228 or 328, as discussed earlier. The controller 210 may receive data representing the radiation 238 from the sensor 228 or 328. in examples where the data is used to determine temperature, the controller 210 may determine respective temperatures for different areas of the build material based on the data representing the radiation 238, as discussed earlier. In examples where the data represents an image, the controller 210 may process the data into a suitable image format, but in other examples the sensor 228 may provide the data to the controller 210 in a suitable image format.

[00082] The detection by the sensor 228 or 328 may be continuous throughout the buiid process of method 40(3, and may end at 416, as will be discussed. In some examples, rather than continuous detection, detection may be performed periodically at predetermined times of the build process, for example, during and/or between 406, 408, 410, and/or 412.

[00083] In some examples, when detecting radiation 238 at 410 while delivering coalescing agent 504 using the agent distributor 202 or 302, radiation 238 may be detected throughout the build material by movement of the carriage 206 or 306, by articulation of the reflector 220 or 320, or a combination thereof, in some examples, when detecting radiation 238 at 406, 408, or 412, or between any of 406, 408, 410, and 412, radiation 238 may be detected throughout the build material by articulation of the reflector 220 or 320 so that the reflector receives radiation 238 from all areas of the build material.

[00084] As will be discussed, aspects of the buiid process may be modulated or modified based on the data received from the sensor 228 or 238 to optimize the build process to achieve accurate object dimensions and properties in accordance with the object design data and/or object property data. For example, the heating by the heater 230, the delivery of coalescing agent 404, and the application of energy by the energy source 226 may be modulated based on the data from the sensor 228 or 238.

[00085] At 406, a layer 502b of build material may be formed, as shown in FIG. 7a. For example, the controller 210 may control the buiid material distributor 224 to form the layer 502b on a previously completed layer 502a on the support member 204 by causing the build material distributor 224 to move along the x-axis as discussed earlier. The completed layer 502a may include a solidified portion 506. Although a completed layer 502a is shown in FIGS. 7a-d for illustrative purposes, it is understood that 406 to 414 may initially be applied to generate the first layer 502a.

[00086] At 408, in some examples, the layer 502b of build material may be heated by the heater 230 to heat and/or maintain the build material within a predetermined temperature range. The predetermined temperature range may, for example, be below the temperature at which the build material would experience bonding in the presence of coalescing agent 504. For example, the predetermined temperature range may be between about 155 and about 160 degrees Celsius, or the range may be centered at about 160 degrees Celsius. Pre-heating may help reduce the amount of energy that has to be applied by the energy source 226 to cause coalescence and subsequent solidification of build material on which coalescing agent has been delivered or has penetrated.

[00087] in some examples, the degree of heating on each area of the layer 502b may be modulated based on the most recent temperatures determined based on detection by the sensor 228 or 328. For example, if a particular area of the layer 502b is colder than expected then a greater degree of heat may be applied to cause the area to reach the predetermined temperature range, and if a particular area of the layer 502b is hotter than expected then a lesser degree of heat may be applied to cause the area to reach the predetermined temperature range.

[00088] At 410, as shown in FIG. 7b, coalescing agent 504 may be selectively delivered to the surface of portions of the layer 502b. As discussed earlier, the agent 404 may be delivered by agent distributor 202 or 302, for example in the form of fluids such as liquid droplets. In some examples, binder agent may be used rather than coalescing agent.

[00089] The selective delivery of the agent 504 may be performed in patterns on the portions of the layer 502b that the data representing the three-dimensional object may define to become solid to form part of the three-dimensional object being generated. "Selective delivery" means that agent may be delivered to selected portions of the surface layer of the build material in various patterns. [00090] in some examples, based on the data from the sensor 228 or 328, the amount of or pattern of agent, e.g. coalescing agent, may be modified so as to achieve coalescence and solidification as intended.

[00091] In some examples, if an area has a higher than expected temperature, then less coalescing agent may be needed compared to areas having lower temperatures.

[00092] in some examples, areas on which coalescing agent has been delivered and/or areas that have coalesced and solidified may be hotter and/or have a different color than areas on which coalescing agent has not been delivered or which have achieved coalescence and solidification. Therefore, the data may indicate if the wrong areas are being solidified, for example because of misalignment of the agent distributor 202 or 302 relative to the support member 204. in this example, the pattern of agent may be modified so as deliver the agent on the areas of the support member and build material as intended. In other examples, if the error cannot be sufficiently corrected or is outside tolerance thresholds, the build process and therefore the object may be cancelled.

[00093] FIG. 7c shows coalescing agent 504 having penetrated substantially completely into the portions of the layer 502b of build material, but in other examples, the degree of penetration may be less than 100%. The degree of penetration may depend, for example, on the quantity of agent delivered, on the nature of the build material, on the nature of the agent, etc.

[00094] At 412, a predetermined level of energy may be temporarily applied to the layer 502b of build material. In various examples, the energy applied may be infra-red or near infra-red energy, microwave energy, ultra-violet (UV) light, halogen light, ultrasonic energy, or the like. The temporary application of energy may cause the portions of the build material on which coalescing agent 504 was delivered to heat up above the melting point of the build material and to coalesce. In some examples, the energy source 226 may be focused. In some examples in which the energy source 226 is focused, the energy source 226 may cause coalescence of build material without use of coalescing agent 504, but in other examples coalescing agent 454 may be used. In other examples, the energy source 226 may be unfocused, and the temporary application of energy may cause the portions of the build material on which coalescing agent 504 has been delivered or has penetrated to heat up above the melting point of the build material and to coalesce. For example, the temperature of some or ail of the layer 502b may achieve about 220 degrees Celsius. Upon cooling, the portions having coalescing agent 404 may coalesce may become solid and form part of the three- dimensional object being generated, as shown in FiG. 7d.

[00095] In some examples, the amount of energy applied on each area of the layer 502b may be modulated based on the most recent temperatures determined based on detection by the sensor 228 or 328. For example, if a particular area of the layer 502b is colder than expected then a greater amount of energy may be applied, and if a particular area of the layer 502b is hotter than expected then a lesser amount of energy may be applied.

[00096] As discussed earlier, one such solidified portion 506 may have been generated in a previous iteration. The heat absorbed during the application of energy may propagate to the previously solidified portion 506 to cause part of portion 506 to heat up above its melting point. This effect helps creates a portion 508 that has strong interiayer bonding between adjacent layers of solidified build material, as shown in FiG. 7d.

[00097] In some examples, the energy may not be applied, for example if binder agent is used, or if the coalescing agent 504 is to cause coalescence and solidification of build material without use of the energy source 226.

[00098] After a layer of build material has been processed as described above in 304 to 318, new layers of build material may be provided on top of the previously processed layer of build material. In this way, the previously processed layer of build material acts as a support for a subsequent layer of build material. The process of 406 to 412 may then be repeated to generate a three-dimensional object layer by layer.

[00099] Thus, at 414, it may be determined, e.g. by the controller 210, whether an additional layer is to be processed to generate the three-dimensional object. If an additional layer is to be processed, the method 400 may proceed to 406, otherwise the method 400 may proceed to 416.

[000100] At 416, the detection of radiation may end. For example, the sensor 228 or 328 may stop detecting the radiation 238.

[000101 ] Ail of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the elements of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or elements are mutually exclusive. [000102] In the foregoing description, numerous details are set forth to provide an understanding of the subject disclosed herein. However, examples may be practiced without some or all of these details. Other examples may include modifications and variations from the details discussed above. It is intended that the appended claims cover such modifications and variations.

Claims

1 . An additive manufacturing system comprising:

a sensor to detect radiation;

a reflector to reflect the radiation from build material to be on a support member to the sensor, the build material to be used to generate a three-dimensional object; and

a controller to receive data representing the radiation from the sensor.

2. The additive manufacturing system of claim 1 wherein the reflector is:

a mirror comprising glass, silver, gold, or aluminum; or

a prism comprising glass, plastic, or fiuorite.

3. The additive manufacturing system of claim 1 wherein the reflector is oriented at an acute angle relative to an axis that is parallel to a surface of the support member that holds the build material.

4. The additive manufacturing system of claim 1 wherein the reflector is in a first region of the additive manufacturing system that experiences a first average temperature while generating the three-dimensional object, wherein the sensor is a second region of the additive manufacturing system that experiences a second average temperature while generating the three-dimensional object, wherein the first average temperature is greater than the second average temperature.

5. The additive manufacturing system of claim 1 wherein the radiation comprises infra-red radiation, wherein the controller is to determine a temperature of the build material based on the data.

6. The additive manufacturing system of claim 1 wherein the radiation comprises visible light, wherein the data represents an optical image of the build material.

7. The additive manufacturing system of claim 1 wherein the controller is to cause the generation of the three-dimensional object to be modulated based on the determined temperature, wherein the modulation comprises modifying an amount of heat applied by a heater to the build material, modifying an amount or pattern of agent to be selectively delivered to the build materia! using an agent distributor, modifying an amount of energy applied by an energy source to the build material, or canceling the generation of the three-dimensional object.

8. The additive manufacturing system of claim 1 further comprising:

a carriage; and

an agent distributor mounted on the carriage to selectively deliver agent to portions of layers of the build material in patterns derived from agent delivery control data representing slices of the three-dimensional such that the portions are to solidify to form the slices in accordance with the patterns,

wherein the sensor and the reflector are coupled to the agent distributor or the carriage.

9. The additive manufacturing system of claim 8 further comprising a cover coupled to the carriage or the agent distributor, wherein the sensor is directly coupled to the carriage or the agent distributor, wherein the cover is disposed over the sensor to shield the sensor from heat.

10. The additive manufacturing system of claim 8 wherein the sensor is coupled to the agent distributor or to the carriage through an arm, wherein the sensor is spaced away from the carriage and the agent distributor to shield the sensor from heat.

1 1 . The additive manufacturing system of claim 8 further comprising a platform that couples the reflector to the agent distributor or the carriage, wherein the platform comprises an opening to allow the radiation from the build material to be received and reflected by the reflector.

12. The additive manufacturing system of claim 1 wherein the reflector is to articulate to reflect the radiation from different areas of the build material.

13. The additive manufacturing system of claim 1 wherein the reflector is to reflect the radiation from different areas of the build material as the carriage and the agent distributor move across the build materia! to deliver the agent to the build material.

14. A method comprising:

reflecting, by a mirror or a prism, radiation from build material on a support member to a sensor while generating a three-dimensional object using the build material;

capturing, using the sensor, the reflected radiation;

providing data representing the detected radiation to a controller; and modifying the generation of the three-dimensional object based on the data.

15. An additive manufacturing system comprising:

a support member to hold build material to be used in a build process to generate a three-dimensional object;

a sensor to capture radiation comprising infra-red radiation or visible light from the build material, the sensor in a first region of the additive manufacturing system; a mirror or a prism to reflect the radiation from the build material to be held on a support member to the sensor, the mirror or the prism in a second region of the additive manufacturing system, wherein the second region has a higher average temperature during the build process than the first region.