WO2022093190A1

WO2022093190A1 - 3d printing with build material layer contone maps

Info

Publication number: WO2022093190A1
Application number: PCT/US2020/057525
Authority: WO
Inventors: Krzysztof Nauka
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2020-10-27
Filing date: 2020-10-27
Publication date: 2022-05-05

Abstract

A machine-readable medium storing instructions executable by a processor is disclosed herein. The medium comprises instructions to receive object data representative of a 3D object to be generated, instructions to determine a first area of a build material layer corresponding to the 3D object and a second area of the build material layer corresponding to an area surrounding a part of the first area, and instructions to assign an energy-absorbent fusing agent to the first area and the second area of the build material layer.

Description

3D PRINTING WITH BUILD MATERIAL LAYER CONTONE MAPS

BACKGROUND

[0001] Some additive manufacturing or three-dimensional printing systems generate 3D objects by selectively solidifying portions of successively formed layers of build material on a layer-by- layer basis. The build material which has not been solidified is separated from the 3D objects to continue with the additive manufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] The present application may be more fully appreciated in connection with the following detailed description of non-limiting examples taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout and in which:

[0003] Figure 1A is a schematic diagram showing an example of a 3D printer comprising an energy source;

[0004] Figure IB is a schematic diagram showing an example of another 3D printer comprising a plurality of energy sources;

[0005] Figure 2 is a graph diagram showing an example of wavelength absorption values of a build material and fusing agent and wavelength emission values of a light source;

[0006] Figure 3 is a flowchart of an example method of controlling the agent distributor of a 3D printer based on a contone map;

[0007] Figure 4 is a schematic diagram showing an example of a contone map; and

[0008] Figure 5 is a block diagram showing a processor-based system example to generate a contone map. DETAILED DESCRIPTION

[0009] The following description is directed to various examples of additive manufacturing, or three-dimensional printing, apparatus and processes involved in the generation of 3D objects. Throughout the present disclosure, the terms "a" and "an" are intended to denote at least one of a particular element. In addition, as used herein, the term "includes" means includes but not limited to, the term "including" means including but not limited to. The term "based on" means based at least in part on.

[0010] As used herein, the terms "about" and "substantially" are used to provide flexibility to a range endpoint by providing that a given value may be, for example, an additional 15% more or an additional 15% less than the endpoints of the range. In another example, the range endpoint may be an additional 30% more or an additional 30% less than the endpoints of the range. The degree of flexibility of this term can be dictated by the particular variable and would be within the knowledge of those skilled in the art to determine based on experience and the associated description herein.

[0011] For simplicity, it is to be understood that in the present disclosure, elements with the same reference numerals in different figures may be structurally the same and may perform the same functionality.

[0012] Additive manufacturing devices, generally known as 3D printers, generate 3D objects based on object data in a 3D virtual model of an object or objects to be generated. 3D printers may generate 3D objects by selectively processing layers of build material. For example, a 3D printer may selectively treat portions of a layer of build material, e.g. a powder, corresponding to a layer of a 3D object to be generated, thereby leaving the portions of the layer un-treated in the areas where no 3D object is to be generated. The combination of the generated 3D objects and the un-treated build material may also be referred to as a build cake. The volume in which the build cake is generated may be referred to as a build chamber.

[0013] Suitable powder-based build materials for use in additive manufacturing include polymer powder, metal powder or ceramic powder. In some examples, non-powdered build materials may be used such as gels, pastes, and slurries. [0014] 3D printers may selectively treat portions of a layer of build material by, for example, ejecting a print agent in a pattern corresponding to the 3D object. Examples of print agents may include fusing agents, detailing agents, curable binder agents or any printing liquid suitable for the generation of a 3D object. Additionally, the chemical composition of some printing liquids may include, for example, a liquid vehicle and/or solvent to be at least partially evaporated once the printing liquid have been applied to the build material layer.

[0015] Some three-dimensional printing systems use fusing agents to treat the portions of the layer of build material. The portions in which the fusing agent is applied are further heated so that the fusing agent absorbs such energy to heat up and melt, coalesce and solidify upon cooling the portions of build material on which the fusing agent was ejected thereto. The three- dimensional printing system may heat the build material by applying energy from an energy source to each layer of build material.

[0016] In some 3D printers, the portions of the build material which are not to be solidified are heated up along with the to be solidified build material portions such that the thermal gradient between both portions is minimized. These thermal gradients, resulting in different expansion of differently heated materials (e.g., thermal stress), tend to generate warps and buckles to the 3D objects once generated. As such, it is wanted to apply energy to both portions as long as the build material corresponding to the portions which do not form part of the 3D object remain unsolidified.

[0017] Furthermore, in some 3D printers, the build material corresponding to the portions of the build material which are not solidified may be used in subsequent print jobs. However, the energy absorbed by the un-solidified polymeric build material particles in order to reduce the thermal stress effect causes degradation of the said polymeric build material due to thermal decomposition of some of its components. If this material is used in subsequent 3D printing the mechanical properties of the printed objects may be adversely impacted. Damage to the build material may grow exponentially with its temperature. As such, there is a compromise between heating build material particles to reduce the thermal stress of the 3D objects generated; and recycling the build material particles. [0018] Referring now to the drawings, Figure 1A is a schematic diagram showing an example of a 3D printer 100A.

[0019] The 3D printer 100A comprises a platform 110 on which build material layers are generated. The platform 110 may comprise a substantially horizontal top surface. In some examples, the platform 110 is a moveable build platform that is, for example, moveable vertically within a build chamber of the 3D printer 100A.

[0020] The 3D printer 100A further comprises a build material distributor 120 moveable along a horizontal axis 170 substantially parallel to the platform 110 to generate a build material layer 130 on the platform 110 or over an already generated build material layer. The build material distributor 120 may be implemented as a spreading device that spreads an amount of build material 135 across the platform 110 or across a previously generated build material layer, to generate a newly formed build material layer 130. In some examples, the build material distributor 120 may be a recoating roller or a doctor blade. In other examples, however, the build material distributor may be an overhead hopper that selectively dispenses build material while moving along the axis 170 to thereby generate the build material layer 130.

[0021] The 3D printer 100A comprises an agent distributor 140 moveable over and across the platform 110, for example along arrow 147. In some examples, the agent distributor 140 scans bidirectionally along the axis 170. In some examples, the agent distributor 140 may be housed in a carriage. In further examples, the 3D printer 100A comprises a plurality of agent distributors 140 independently controllable to move one after the other over the platform 110, for example synchronously or asynchronously with respect to each other. Each of the plurality of agent distributors 140 may eject the same agents or different agents.

[0022] The agent distributor 140 is controllable to selectively eject an energy-absorbent print agent 145 to portions of the build material layer 130 to generate 3D printed objects as described herein. In an example, the agent distributor 140 comprises thermal inkjet printheads or piezoelectric printheads. However, other examples may include any other agent distributor 140 suitable for selectively eject an amount of the energy-absorbent print agent 145. [0023] In the examples herein, the print agent 145 may include, fusing agent and may be ejected along with other agents such as detailing agent, colored agents or a combination thereof. The print agent 145 may include any other suitable print agent to be ejected during the processing of a print job by the 3D printer 100A to generate a 3D object.

[0024] In some examples, the agent distributor 140 ejects a white or transparent (e.g., colorless) fusing agent to absorb energy from an energy source. In some examples, the fusing agent is to absorb energy at the wavelengths corresponding to the peak of emission of the emitted energy. Some examples of white or transparent fusing agents may include UV absorbers. Some colorless UV absorbers comprise pigments or dies comprising, for example one of TiO2, ZnO, CeO2, ITO, SnO, Acid Yellow 19 and 23, "gray" inks, Cyanocobalamin, Folic acid, Riboflavin, Pyridoxal Phosphate, Pyridoxal HCI, Pyridoxine HCI, Phylloquinone (vitamin KI), Epolin 29, Other benzotriazoles, benzophenones, oxanilides, hydroxyphenyl triazines (Tinuvin P, Hostavin 3315, Hoechst 33258), pyranine, 2,2'-dihydroxy-4-methoxybenzophenone, 8-Anilino-l- napththalenesulfonic acid, Quinine sulfate or 3-hydroxyacetophene, l,4-Bis(5-phenyl-2- oxazolyl)benzene.

[0025] In other examples, the agent distributor 140 ejects a black or colored fusing agent to absorb energy from an energy source. In some examples, the fusing agent is to absorb energy at the wavelengths corresponding to the peak of emission of the emitted energy. Some examples of black or colored fusing agents may include carbon black or colored UV absorbers. Some colored UV absorbers comprise pigments or dies comprising, for example some of Acid Yellow 19 and 23, "gray" inks, Cyanocobalamin, Folic acid, Riboflavin, Pyridoxal Phosphate, Pyridoxal HCI, Pyridoxine HCI, pyranine, 2,2'-dihydroxy-4-methoxybenzophenone, 8-Anilino-l- napththalenesulfonic acid, Quinine sulfate, 3-hydroxyacetophene, l,4-Bis(5-phenyl-2- oxazolyl)benzene, curcumin, coffee or Ag in form of plasmonic nanoparticles.

[0026] In some examples, the 3D printer 100A may further comprise a set of print agent reservoirs (not shown) to supply the corresponding print agent 145 to the agent distributor 140. In other examples, however, the 3D printer 100A may comprise a print agent reservoir enclosure within which a print agent reservoir is to be inserted to, thereby, supply the print agent 145 to the agent distributor 140. In yet further examples, the agent distributor 140 is fluidically connected to an external source of the print agent 145.

[0027] The 3D printer 100A further comprises an energy source 150. In an example, the energy source 150 may be housed in a carriage 110 that is to scan bidirectionally along the horizontal axis 170 and over the platform. In another example, the energy source 150 may be an overhead energy source to irradiate substantially the entire printing surface over the platform 110. The energy source 150 is controllable to emit energy 155 to the build material layer 130. The energy source 150 is to emit energy 155 at single wavelength or a narrow band of wavelengths. The energy source 150 is selected such that the wavelength or narrow band of wavelengths is substantially reflected by the raw build material and substantially absorbed by the print agent. Some examples of specific wavelengths are disclosed herein with reference to Figure 2.

[0028] In the examples herein, a narrow band of wavelengths may be interpreted as a band of wavelengths whose width ranges from about 1 nm to about 50 nm. In other examples, a narrow band of wavelengths width ranges from about 1 nm to 30 nm. In yet other examples, a narrow band of wavelengths width ranges from about 1 nm to lOnm.

[0029] The energy source 150 may comprise an array of solid-state emitters. In an example, the array of solid-state emitters is an array of Light-Emitting Diodes (LED), an array of Laser Diodes (LD) such as Edge Laser Diodes (ELD), or an array of Vertical-Cavity Surface-Emitting Lasers (VCSEL). In yet another example, the array of solid-state emitters may be a combination of at least two of LEDs, LDs and VCSELS.

[0030] LEDs, LDs and VCSELs are formed by semiconductor diodes. The choice of the semiconductor material determines the wavelength of the emitted light beam, which may range from the infra-red to the UV spectrum. In the examples herein, the type of solid-state emitters of the solid-state emitters array is selected to emit energy 155 in a narrow band of wavelengths to be absorbed by the print agent 145.

[0031] The 3D printer 100A further comprises a controller 160. The controller comprises a processor 165 and a memory 167 with specific control instructions stored therein to be executed by the processor 165. The controller 160 may be coupled, either directly or indirectly, to the build material distributor 120, the agent distributor 140 and the energy source 150. Additionally, the controller 160 may also be coupled to the platform 110. The controller 160 may control at least some of the operations of the elements that it is coupled therewith. The functionality of the controller 160 is described further below with reference to Figure 3.

[0032] In the examples herein, the controller 150 may be any combination of hardware and programming that may be implemented in a number of different ways. For example, the programming of modules may be processor-executable instructions stored in at least one non- transitory machine-readable storage medium and the hardware for modules may include at least one processor to execute those instructions. In some examples described herein, multiple modules may be collectively implemented by a combination of hardware and programming. In other examples, the functionalities of the controller may be, at least partially, implemented in the form of an electronic circuitry. The controller may be a distributed controller, a plurality of controllers, and the like.

[0033] Figure IB is a schematic diagram showing an example of a 3D printer lOOB. The 3D printer 100B comprises the previously disclosed elements from the 3D printer 100A of Figure 1A referred to with the same reference numerals. The 3D printer 100B comprises the platform 110, the build material distributor 120, the agent distributor 140, the energy source 150 and the controller 160.

[0034] In addition to the elements of the 3D printer 100A from Figure 1A, the 3D printer 100B further comprises an additional energy source 180 to emit energy 185 to the build material layer 130 at a broad band of wavelengths to be absorbed by the build material. The broad band of wavelengths may comprise wavelengths from the UV spectrum to the IR spectrum. White build material particles absorb energy from the UV and the IR spectra. In some examples, the additional energy source may be a Halogen lamp, a Tungsten lamp, a Quartz Tungsten Halogen lamp or any other lamp suitable to emit energy to the build material layer 130 at the broad band of wavelengths.

[0035] In the examples herein, a broad band of wavelengths may be interpreted as a band of wavelengths whose width ranges from about 500 nm to about 4000 nm. In other examples, a broad band of wavelengths width ranges from about 500 nm to 2000 nm. In yet other examples, a broad band of wavelengths width ranges from about 1 nm to 500nm.

[0036] The additional energy source 180 is to heat substantially the entire build material layer 130 to reduce the thermal stress between the portions of the build material layer 130 to be solidified and the other portions of the build material layer 130. As it is appreciated from the examples below, the build material layer 130 may be heated with a little amount of energy to reduce the thermal stress phenomenon, and thereby reduce the powder degradation effect and increase the recyclability of said powdered build material.

[0037] The energy source 150 and the additional energy source 180 may be implemented in a number of different ways. In an example, the energy source 150 is housed in a carriage to scan bidirectionally along the horizontal axis 170 and the additional energy source 180 is an overhead energy source. The carriage may be moveable along with the agent distributor 140, for example in the same or in an independent carriage. In another example, both the energy source 150 and the additional energy source 180 are housed in a carriage to scan bidirectionally along the horizontal axis 170. In yet another example, both the energy source 150 and the additional energy source 180 are overhead energy sources in which at least the energy source 150 is capable to selectively emit the energy 155 to specific portions of the build material layer 130.

[0038] Figure 2 is a graph diagram 200 showing an example of the absorption values of a build material and fusing agent and emission values of a light source in a band of wavelengths from about 200 nm to 500 nm.

[0039] The first series 220 of the graph diagram 200 is indicative of the energy absorption rate of a polyamide 12 which is a white powdered build material. Other types of build material, such as polypropylenes, polyurethanes (e.g., thermoplastic polyurethane), and other polyamides (e.g., polyamide 11) may absorb energy in a similar way. As shown, the build material has its first peak of absorption (i.e., about 90% energy absorbed, about 10% of energy reflected) at about 200nm. The energy absorption diminishes at higher wavelengths, for example from 400nm to about 1350 nm (not shown), where the build material has an energy absorption rate below 10% thereby reflecting substantially 90% of the emitted energy. At even higher wavelengths, the build material absorbs a higher amount of energy. For example, at about 3000 nm (not shown) the build material absorbs substantially the entire emitted energy. As such, in an example, the energy source 150 is to emit energy 155 at a narrow band of wavelengths from the range of about 350 nm to about 700 nm such that the build material reflects substantially the entire energy emitted. In another example, the energy source 150 is to emit energy 155 at a narrow band of wavelengths from the range of about 350 nm to about 400 nm.

[0040] The second series 240 of the graph diagram 200 is indicative of the energy absorption rate of a UV fusing agent which is an example of the energy-absorbent print agent 145 to be ejected by the agent distributor 140 from Figure 1A. The UV fusing agent has its peak of absorption at about 340 to about 350 nm (i.e., about 90%-100% of the energy is absorbed). The UV fusing agent absorbs over 40% of an emitted energy at wavelengths ranging from about 300 to about 370nm. Other types of similar fusing agents that are compliant with examples herein may be used without departing from the scope of the present disclosure.

[0041] As such, by using the build material from the first series 220 and the UV fusing agent of the second series 240, it is noted that energy emitted at a narrow band of wavelengths from about 330 nm to about 370 nm is substantially reflected by the build material (i.e., 80-90% reflected) and substantially absorbed by the UV fusing agent (i.e., 90-40% absorbed, including the peak of absorption at about 340-350nm). As such, emitting energy at a wavelength or narrow band of wavelengths from the range of about 330 nm to about 370 nm enables a selective absorption of energy in areas where the UV fusing agent is ejected and substantially no build material degradation in the other areas.

[0042] The third series 260 of the graph diagram 200 is indicative of the energy emission rate of a UV LED (365nm) which is an example of a narrow-band energy source 150 from the 3D printer 100A of Figure 1A. The UV LED (365nm) emits energy at above 30% emission rate at wavelengths from about 356 nm to about 370 nm, having its peak of emission at about 365nm (i.e. 100%). Accordingly, the UV LED (365nm) of the third series 260 emits energy at a range of wavelengths from 350nm to 380nm and is thereby suitable to achieve a selective energy absorption at areas where the UV fusing agent of the second series 240 is ejected while maintaining a no build material degradation (build material of the first series 220) in the other areas.

[0043] The above examples with reference to Figure 2 are examples and other combinations of build materials, fusing agents and narrow-band energy sources suitable for the teaching herein may be used without departing from the scope of the present disclosure.

[0044] Figure 3 is a flowchart of an example method 300 of controlling the agent distributor 140 of a 3D printer based on a contone map. The method 300 involves previously disclosed elements from Figures 1A and IB referred to with the same reference numerals. In some examples, parts of method 300 may be executed by the controller 160 of the 3D printer (100A, 100B).

[0045] At block 320, the controller 160 controls the build material distributor 120 to generate a build material layer 170 on the platform 110 or on a previously generated build material layer. In an example, the controller 160 may spread an amount 135 of build material across the printable area of the platform 110. In other examples, the build material distributor 120 dispenses build material from above the platform 110 to generate the build material layer 130.

[0046] At block 340, the controller 160 accesses a contone map. In some examples, the contone map is computed by the 3D printer controller 160. In another example, the contone map is computed by an external computing device and then sent to the controller 160. In an example, the external computing device is the processor-based system of Figure 5.

[0047] Figure 4 is a schematic diagram showing an example of a contone map 400. The contone map 400 comprises a first area 490 and a second area 495. The first area 490 of the build material layer 130 corresponds to a 3D object or plurality of 3D objects to be generated (e.g., an illustrated circular-shaped 3D object). The second area 495 of the build material layer 130 corresponds to an area surrounding the first area 490. In some examples, the second area 495 surrounds a part of the first area 490. In other examples the second area 495 completely surrounds the first area 490.

[0048] The second area 495 separates the first area 490 indicative of the build material layer 130 portions to be solidified, from the other portions of the build material layer 130 that are not to be solidified. The separation between the first area 490 and the other portions of the build material layer 130 that are not to be solidified corresponds to the width of the second area 495 (indicated by the reference 'L')- In some examples, the controller 160 or the external computing device is to define the width of the second area 495 based on the geometry of the of the 3D object to be generated. In other examples, the controller 160 or the external computing device is to define the width of the second area 495 based on a distribution profile of the gradient concentration of the print agent in the second area 495 (see, block 360 from Figure 3). In yet further examples, the controller 160 or the external computing device are encoded with a predetermined width of the second area 495 of the range of about 0.5mm to about 1cm.

[0049] Turning back to Figure 3, at block 360 the controller 160 is to control the agent distributor 140 to selectively eject the print agent 145 at least to the first area and the second area of the build material layer 130. In some examples, the concentration of print agent 145 ejected per surface unit of first area 490 is a different concentration than the concentration of print agent 145 ejected per surface unit of the second area 490. In other examples, the print agent 145 ejected to the first area 490 is a print agent that absorbs a higher quantity of energy 155 per surface unit than a different print agent to be ejected to the second area 490.

[0050] In the examples herein, the energy 155 emitted by the selected energy source 150 is to be substantially entirely reflected by the build material and substantially entirely absorbed by the energy-absorbent print agent 145 (see, Figure 2). As such, the recycled build material is to maintain its original mechanical properties as the build material particles have not been excessively heated during the previous printing stage. However, the build material layer 130 portions corresponding to the first area 490 have been ejected with energy-absorbent print agent 145. Upon application of energy 155, the print agent 145 is to absorb, at least partially, the energy and heat up, melt, coalesce and solidify upon cooling the build material particles corresponding to the first area 490. The build material layer 130 portions corresponding to the second area 495 have also been ejected with energy-absorbent print agent 145 to absorb enough energy to heat up, but not enough energy to melt and coalesce the corresponding build material particles. As such, the build material particles corresponding to the second area 495 are heated up to reduce the thermal gradient at the edges of the first area 490 and thereby avoid warpage and buckles of the generated 3D object. Furthermore, in the examples herein, most part of the build material that is not to be solidified (i.e., build material layer 130 portions which do not correspond to the first and second areas 490-495) remain unheated to be fully recycled.

[0051] In an example, the controller 160 is to control the agent distributor 140 to eject a white or transparent fusing agent to the first and second areas 490-495. In another example, the controller 160 is to control the agent distributor to eject a white or transparent fusing agent to the second area 495 and another different fusing agent to the first area 490, for example a carbon-black based fusing agent. Ejecting a white or transparent fusing agent to the build material corresponding to the second area 495 enables said build material to remain unblemished and being suitable to be further recycled.

[0052] In some examples, the controller 160 is to control the agent distributor 140 to eject the print agent 145 to the second area 495 in a gradient concentration basis. In these examples, the print agent 145 is to be ejected at a higher concentration per surface unit at the surface units which are closer to the first area 490; and at lower concentration per surface unit at the surface units which are closer to the portions of the build material layer 130 other than the first and second areas 490-495. In an example, the gradient concentration basis follows a linear pattern. In another example, the gradient concentration basis follows a parabolic pattern. In yet further examples, other incremental patterns may be used. The pattern to be used may be pre-calculated based on a thermal analysis of the energy source 150, the geometry of the first area 490 and the width of the second area 495. In these examples, the thermal exposure of the build material corresponding to the parts of the second area 495 which are farther from the first area 490 is reduced, thereby reducing the mechanical property loss of the corresponding build material particles and increase its recyclability while enabling the thermal stress effect reduction at the first area 490.

[0053] At block 380, the controller 160 is to control the energy source 150 to emit energy 155 at the first and second areas 490-495 at the wavelength or narrow band of wavelengths. In some examples, the energy source 150 is further to emit energy to the remaining portions of the build material layer 130. The energy 155 is to be substantially reflected by the build material and absorbed by the print agent 145 such that the build material corresponding to the first area 490 is to heat up, melt, coalesce and solidify upon cooling, and the build material corresponding to the second area 490 is to heat up below its melting point.

[0054] Figure 5 is a block diagram showing a processor-based system 500 example to generate a contone map (e.g., contone map 400 from Figure 4). In the examples herein, the instructions of system 500 may involve previously disclosed elements from Figures 1A-1B, 2-4 referred to with the same reference numerals.

[0055] In some implementations, the system 500 may be or may form part of an external computing unit from a 3D printing system. In other examples, however, the system 500 may be part of a 3D printing system. In some implementations, the system 500 is a processor-based system and may include a processor 510 coupled to a machine-readable medium 520. The processor 510 may include a single-core processor, a multi-core processor, an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), and/or any other hardware device suitable for retrieval and/or execution of instructions from the machine-readable medium 520 (e.g., instructions 522-526) to perform functions related to various examples. Additionally, or alternatively, the processor 510 may include electronic circuitry for performing the functionality described herein, including the functionality of instructions 522-526. With respect of the executable instructions represented as boxes in Figure 5, it should be understood that part or all of the executable instructions and/or electronic circuits included within one box may, in alternative implementations, be included in a different box shown in the figures or in a different box not shown.

[0056] The machine-readable medium 520 may be any medium suitable for storing executable instructions, such as a random-access memory (RAM), electrically erasable programmable readonly memory (EEPROM), flash memory, hard disk drives, optical disks, and the like. In some example implementations, the machine-readable medium 520 may be a tangible, non-transitory medium, where the term "non-transitory" does not encompass transitory propagating signals. The machine-readable medium 520 may be disposed within the processor-based system 500, as shown in Figure 5, in which case the executable instructions may be deemed "installed" on the system 500. Alternatively, the machine-readable medium 520 may be a portable (e.g., external) storage medium, for example, that allows system 500 to remotely execute the instructions or download the instructions from the storage medium. In this case, the executable instructions may be part of an "installation package". As described further herein below, the machine- readable medium may be encoded with a set of executable instructions 521-526.

[0057] Instructions 522, when executed by the processor 510, may cause the processor 510 to receive object data that represents at least a part of a 3D object which is to be manufactured by a 3D printer. In some examples, the format of the data may include a Computer Aided Product (CAD) file.

[0058] Instructions 524, when executed by the processor 510, may cause the processor 510 to determine a first area 490 of a build material layer 130 corresponding to the 3D object and a second area 495 of the build material layer corresponding to an area surrounding a part of the first area 490.

[0059] Instructions 526, when executed by the processor 510, may cause the processor 510 to assign an energy-absorbent white or transparent fusing agent to the first area 490 and the second area 495 of the build material layer 130.

[0060] The above examples may be implemented by hardware, or software in combination with hardware. For example, the various methods, processes and functional modules described herein may be implemented by a physical processor (the term processor is to be implemented broadly to include CPU, SoC, processing module, ASIC, logic module, or programmable gate array, etc.). The processes, methods and functional modules may all be performed by a single processor or split between several processors; reference in this disclosure or the claims to a "processor" should thus be interpreted to mean "at least one processor". The processes, method and functional modules are implemented as machine-readable instructions executable by at least one processor, hardware logic circuitry of the at least one processor, or a combination thereof.

[0061] The drawings in the examples of the present disclosure are some examples. It should be noted that some units and functions of the procedure may be combined into one unit or further divided into multiple sub-units. What has been described and illustrated herein is an example of the disclosure along with some of its variations. The terms, descriptions and figures used herein are set forth by way of illustration. Many variations are possible within the scope of the disclosure, which is intended to be defined by the following claims and their equivalents.

[0062] There have been described example implementations with the following sets of features:

[0063] Feature set 1: A 3D printer comprising: a build material distributor to generate a build material layer on a platform; an agent distributor to selectively eject an energy-absorbent print agent to the build material layer; an energy source to emit energy to the build material layer at a wavelength or a narrow band of wavelengths to be absorbed by the print agent; and a controller to: control the build material distributor to generate a build material layer; access a contone map comprising a first area of the build material layer corresponding to a 3D object to be generated and a second area of the build material layer corresponding to an area surrounding a part of the first area; control the agent distributor to selectively eject the print agent to the first area and the second area of the build material layer; and control the energy source to emit energy at the first and second areas at the wavelength or narrow band of wavelengths.

[0064] Feature set 2: A 3D printer with feature set 1, wherein the print agent is a white or transparent fusing agent.

[0065] Feature set 3: A 3D printer with any preceding feature set 1 to 2, wherein the agent distributor is to selectively eject a first energy-absorbent print agent and a second different white or transparent energy-absorbent print agent, and the controller is to control the agent distributor to selectively eject the first print agent to the first area and the second print agent to the second area. [0066] Feature set 4: A 3D printer with any preceding feature set 1 to 3, wherein the first print agent is a carbon-black based fusing agent.

[0067] Feature set 5: A 3D printer with any preceding feature set 1 to 4, wherein the controller is to control the agent distributor to eject the print agent to the second area in a gradient concentration basis.

[0068] Feature set 6: A 3D printer with any preceding feature set 1 to 5, The 3D printer of claim 5, wherein the gradient concentration follows one of a linear or parabolic pattern.

[0069] Feature set 7: A 3D printer with any preceding feature set 1 to 6, wherein the controller is to define the width of the second area based on the geometry of the 3D object to be generated.

[0070] Feature set 8: A 3D printer with any preceding feature set 1 to 7, wherein the controller is encoded with a predetermined width of the second area of the range of about 0.5mm to about lcm.

[0071] Feature set 9: A 3D printer with any preceding feature set 1 to 8, wherein the energy source is to emit energy at a narrow band of wavelengths from the range of about 350nm to about 700nm.

[0072] Feature set 10: A 3D printer with any preceding feature set 1 to 9, wherein the energy source is an array of UV LEDs

[0073] Feature set 11: A 3D printer with any preceding feature set 1 to 10, further comprising an additional energy source to emit energy to the build material layer at a broad band of wavelengths to be absorbed by the build material.

[0074] Feature set 12: A 3D printer with any preceding feature set 1 to 11, wherein the energy source is moveable along the agent distributor over the platform and the additional energy source is an overhead energy source over the platform.

[0075] Feature set 13: A method comprising: generating a build material layer with a build material distributor; determining a first area of the build material layer corresponding to a 3D object to be generated and a second area of the build material layer corresponding to an area surrounding a part of the first area; selectively ejecting, by an agent distributor, an energy-absorbent print agent to the first area and the second area of the build material layer, wherein the print agent is ejected to the second area in a gradient concentration basis; and emitting energy, by an energy source, at the first and second areas at a wavelength or a narrow band of wavelengths to be absorbed by the print agent

[0076] Feature set 14: A method with feature set 13, wherein the print agent is a white or transparent fusing agent.

[0077] Feature set 15: A non-transitory machine-readable medium storing instructions executable by a processor, the non-transitory machine-readable medium comprising: instructions to receive object data representative of a 3D object to be generated; instructions to determine a first area of a build material layer corresponding to the 3D object and a second area of the build material layer corresponding to an area surrounding a part of the first area; and instructions to assign an energy-absorbent white or transparent fusing agent to the first area and the second area of the build material layer

Claims

CLAIMS WHAT IT IS CLAIMED IS:

1. A 3D printer comprising: a build material distributor to generate a build material layer on a platform; an agent distributor to selectively eject an energy-absorbent print agent to the build material layer; an energy source to emit energy to the build material layer at a wavelength or a narrow band of wavelengths to be absorbed by the print agent; and a controller to: control the build material distributor to generate a build material layer; access a contone map comprising a first area of the build material layer corresponding to a 3D object to be generated and a second area of the build material layer corresponding to an area surrounding a part of the first area; control the agent distributor to selectively eject the print agent to the first area and the second area of the build material layer; and control the energy source to emit energy at the first and second areas at the wavelength or narrow band of wavelengths.

2. The 3D printer of claim 1, wherein the print agent is a white or transparent fusing agent.

3. The 3D printer of claim 1, wherein the agent distributor is to selectively eject a first energy-absorbent print agent and a second different white or transparent energy-absorbent print agent, and the controller is to control the agent distributor to selectively eject the first print agent to the first area and the second print agent to the second area.

4. The 3D printer of claim 3, wherein the first print agent is a carbon-black based fusing agent.

5. The 3D printer of claim 1, wherein the controller is to control the agent distributor to eject the print agent to the second area in a gradient concentration basis.

6. The 3D printer of claim 5, wherein the gradient concentration follows one of a linear or parabolic pattern.

7. The 3D printer of claim 1, wherein the controller is to define the width of the second area based on the geometry of the 3D object to be generated.

8. The 3D printer of claim 1, wherein the controller is encoded with a predetermined width of the second area of the range of about 0.5mm to about 1cm.

9. The 3D printer of claim 1, wherein the energy source is to emit energy at a narrow band of wavelengths from the range of about 350nm to about 700nm.

10. The 3D printer of claim 1, wherein the energy source is an array of UV LEDs.

11. The 3D printer of claim 1, further comprising an additional energy source to emit energy to the build material layer at a broad band of wavelengths to be absorbed by the build material.

12. The 3D printer of claim 11, wherein the energy source is moveable along the agent distributor over the platform and the additional energy source is an overhead energy source over the platform.

13. A method comprising: generating a build material layer with a build material distributor; determining a first area of the build material layer corresponding to a 3D object to be generated and a second area of the build material layer corresponding to an area surrounding a part of the first area; selectively ejecting, by an agent distributor, an energy-absorbent print agent to the first area and the second area of the build material layer, wherein the print agent is ejected to the second area in a gradient concentration basis; and emitting energy, by an energy source, at the first and second areas at a wavelength or a narrow band of wavelengths to be absorbed by the print agent.

14. The method of claim 13, wherein the print agent is a white or transparent fusing agent.

15. A non-transitory machine-readable medium storing instructions executable by a processor, the non-transitory machine-readable medium comprising: instructions to receive object data representative of a 3D object to be generated; instructions to determine a first area of a build material layer corresponding to the 3D object and a second area of the build material layer corresponding to an area surrounding a part of the first area; and instructions to assign an energy-absorbent white or transparent fusing agent to the first area and the second area of the build material layer.