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Title:
FUSING APPARATUS FOR A THREE-DIMENSIONAL PRINTER
Document Type and Number:
WIPO Patent Application WO/2019/135738
Kind Code:
A1
Abstract:
Systems and methods for using microwave energy to form objects in a three- dimensional (3D) printer are provided. An example of a fusing apparatus includes a print head configured to apply a liquid susceptor agent (LSA) to a bed of build material. A microwave head that includes a number of microwave tips is configured to apply microwave energy to the bed of build material. A controller is configured to apply LSA from the print head in a pattern over the bed of build material, and apply microwave energy from a microwave tip of the plurality of microwave tips of the microwave head when the microwave tip is proximate to the LSA on the bed of build material.

Inventors:
CHAMPION, David, A. (1070 NE Circle Blvd, Corvallis, OR, 97330-4239, US)
PEDERSON, Douglas (1070 NE Circle Blvd, Corvallis, OR, 97330-4239, US)
KASPERCHIK, Vladek, P. (1070 NE Circle Blvd, Corvallis, OR, 97330-4239, US)
Application Number:
US2018/012156
Publication Date:
July 11, 2019
Filing Date:
January 03, 2018
Export Citation:
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Assignee:
HEWLETT-PACKARD DEVELOPMENT COMPANY, L.P. (10300 Energy Drive, Spring, Texas, 77389, US)
International Classes:
B29C64/165; B29C64/295; B29C64/393; B33Y10/00; B33Y30/00; B33Y50/02
Attorney, Agent or Firm:
LEMMON, Marcus, B. et al. (HP Inc, 3390 East Harmony RoadMail Stop 3, Fort Collins CO, 80528, US)
Download PDF:
Claims:
CLAIMS

What is claimed is:

1. A fusing apparatus for a three-dimensional (3D) printer, comprising: a print head configured to apply a liquid susceptor agent (LSA) to a bed of build material;

a microwave head comprising a plurality of microwave tips configured to apply microwave energy to the bed of build material; and

a controller configured to:

apply LSA from the print head in a pattern over the bed of build

material; and

apply microwave energy from a microwave tip of the plurality of

microwave tips of the microwave head when the microwave tip is proximate to the LSA on the bed of build material.

2. The fusing apparatus of claim 1 , the controller to use a build map to determine when the microwave tip is proximate to the LSA.

3. The fusing apparatus of claim 1 , the controller to detect the LSA and activate the microwave tip.

4. The fusing apparatus of claim 1 , comprising a power circuit coupled to each one of the plurality of microwave tips.

5. The fusing apparatus of claim 4, wherein the power circuit comprises a feedback detector to control the microwave energy applied to the microwave tip.

6. The fusing apparatus of claim 4, wherein the power circuit comprises a phase locked loop to control the microwave energy applied to the microwave tip.

7. The fusing apparatus of claim 1 , the microwave head comprising a plurality of arrays of microwave tips, wherein each of the arrays are offset from an adjoining array.

8. A method for fusing a build material using a microwave tip, comprising: forming a layer of build material over a build platform;

applying a liquid susceptor agent in a pattern over the layer of build material; activating a microwave tip proximate to a target zone; and

adjusting energy applied to the microwave tip.

9. The method of claim 8, comprising moving a powder handling over the build platform to deposit the build material in the layer of build material.

10. The method of claim 8, comprising moving a microwave head over the layer of build material, wherein the microwave head comprises the microwave tip.

1 1 . The method of claim 8, comprising:

measuring the energy reflected from the layer of build material; and adjusting the energy based, at least in part, on the energy reflected from the layer of build material.

12. The method of claim 8, comprising:

measuring a phase of the energy reflected from the layer of build material; and

adjusting the energy based, at least in part, on the phase.

13. A non-transitory, machine readable medium comprising code to direct a processor to:

apply microwave energy to a surface through a microwave tip;

detect microwave energy reflected from the surface; and

adjust the microwave energy applied to the microwave tip in response to the microwave energy detected.

14. The non-transitory, machine readable medium of claim 13, comprising code to direct the processor to:

dispense a build material to form the surface; and

apply a liquid susceptor agent to the surface in a pattern.

15. The non-transitory, machine readable medium of claim 13, comprising code to direct the processor to:

read a build file to determine a location of a liquid susceptor agent on the surface; and

apply microwave energy proximate to the liquid susceptor agent.

Description:
FUSING APPARATUS FOR A THREE-DIMENSIONAL PRINTER

BACKGROUND

[0001] Three-dimensional (3D) printing may produce a 3D object by adding successive layers of build material, such as powder, to a build platform, then selectively solidifying portions of each layer under computer control to produce the 3D object. The build material may be powder, or powder-like material, including metal, plastic, ceramic, composite material, and other powders. In some examples, the powder may be formed from, or may include, short fibers that may have been cut into short lengths from long strands or threads of material.

[0002] The objects formed can be various shapes and geometries, and may be produced using a model, such as a 3D model or other electronic data source. The fabrication may involve laser melting, laser sintering, heat sintering, electron beam melting, thermal fusion, and so on. The model and automated control may facilitate the layered manufacturing and additive fabrication. The 3D printed objects may be prototypes, intermediate parts and assemblies, as well as end-use products. Product applications may include aerospace parts, machine parts, medical devices, automobile parts, fashion products, and other applications.

DESCRIPTION OF THE DRAWINGS

[0003] Certain examples are described in the following detailed description and in reference to the drawings.

[0004] Fig. 1 is a schematic diagram of a selective solidification process using a print head to apply a liquid susceptor agent (LSA) to a bed of build material and a microwave head to apply energy proximate to the LSA, in accordance with examples.

[0005] Fig. 2 is a cross-sectional view of a microwave tip illustrating the field of microwave energy emanating from the microwave tip, in accordance with examples.

[0006] Fig. 3 is a cross-sectional view of an array of microwave tips in a line on a microwave head proximate to a bed of build material, in accordance with examples. [0007] Fig. 4 is a plot of an open load intensity of microwave energy versus frequency that may be used for a solidification process, in accordance with examples.

[0008] Fig. 5 is a cross-sectional view of a coupon of solidified build material that has been further fused by the application of microwave energy from a microwave tip, in accordance with examples.

[0009] Fig. 6 is a schematic diagram of a power circuit for applying microwave energy through a microwave tip while measuring a phase of energy reflected from a surface to the microwave tip, in accordance with examples.

[0010] Fig. 7 is a plot of a series of runs illustrating the repeatability of the selective solidification of a bed of build material, in accordance with examples.

[0011] Fig. 8 is a plot of a series of runs illustrating the dependence of the phase on tip height during the selective solidification of a bed of build material, in accordance with examples.

[0012] Fig. 9 is a plot of heating profiles at a fixed tip height of 1 mm based on the application of different energies to the bed of build material, in accordance with examples.

[0013] Fig. 10 is a plot of reflected power and plastic temperature rise at a fixed power and tip height, in accordance with examples.

[0014] Fig. 1 1 is a drawing of a three-dimensional (3D) printer, in accordance with examples.

[0015] Fig. 12 is a schematic diagram of a 3D printer having an internal new material vessel that discharges new build material through a new feeder into a conveying system, in accordance with examples.

[0016] Fig. 13 is a process flow diagram of a method for selectively solidifying a bed of build material using microwave energy, in accordance with examples.

[0017] Fig. 14 is a block diagram of a system for using microwave energy to selectively solidify build material in a bed, in accordance with examples.

[0018] Fig. 15 is a block diagram of a non-transitory, machine readable medium comprising code to direct a processor to control the application of energy to selectively solidify build material in a bed, in accordance with examples. DETAILED DESCRIPTION

[0019] In examples described herein, controlled and focused application of microwave energy, which is selectively coupling to a liquid susceptor agent (LSA), provides selectivity of solidification (fusing) and overall energy efficiency. The LSA may be jetted over a bed of build material from a print head, in a pattern that forms a layer of a three-dimensional (3D) object. In some examples, the LSA may be deposited over the bed using a single nozzle to draw a pattern.

[0020] The microwave techniques may broaden the options for materials used in some 3D printing processes. The application of the microwave energy application may be limited to areas of a bed of build material where heating to fusing

temperatures may be desirable, rather than heating all of a surface of build material. This may provide an energy efficiency gain, and may also lead to less of the build material having a history of exposure to energy.

[0021] Currently, some 3D printing techniques may use a liquid fusing agent (LFA) for defining patterns on a bed of build material. Optical radiation energy may then be applied to the treated surface. The LFA patterned surface absorbs a larger amount of radiation than non-patterned powder areas, creating a process temperature window. The process temperature window is the temperature difference between the patterned and non-patterned surface. A polymer powder that may undergo a sharp phase transition to turn into a molten state is typically used. These materials may have a viscosity that is not usually higher than about 1000

pascals/sec (Pa/s) in the molten state. The polymers that may be used may include highly crystalline polymers, such as polyamides, which are considered good materials for such 3D printing processes because of their sharp melting transition which allows processing within relatively narrow process window. Low crystallinity and amorphous polymers that do not have sharp melting transition at their processing temperature may use very wide process temperature window, which may be difficult to achieve with some 3D printing processes.

[0022] Directional or local application of microwave energy may provide accelerated heating to an area of a build material that has been treated with a susceptor agent. This may expand the temperature processing window for the build materials, allowing a wider variety of materials to be used. For example, non-polar polymers that are not treated by susceptor agents may be heated to a much lower temperature when exposed to microwave radiation. The wide process temperature window may enable the use of build material such as plastic powders that do not have sharp phase transitions upon heating (crystalline polymers) to be used in some 3D printing processes. These materials may include low crystallinity and amorphous polymer powders, as well as other plastics which tend to be substantially transparent to microwave energy at about 2.4 GHz, for example, increasing in temperature less than about 5 °C, or about 1 °C, or less upon exposure to the microwave radiation in the absence of a susceptor agent. For example, polymers that may be used as build materials include lower crystallinity and branched polyethylenes and polypropylenes, polystyrene, styrene-butadiene co-polymer, ABS, nylon, Teflon, polyvinyl chloride (PVC), thermoplastic urethane’s (TPU) and the like.

[0023] The susceptor agents that may be used in the LSA include any number of materials having polar molecules that couple with microwave energy, for example, at about 2.4 GHz. These materials may include an MJF carbon black or fusing agent, water, organic solvent with dipol molecules, and metal nanoparticles, such as nickel, copper, silver, iron, and the like as well as nano-particles of many transition metal oxides, such as Fe 3 0 4 , CuO, Co 3 0 4 , MnO, and the like. The LSA may be an aqueous suspension of the susceptor agents, for example, using a surfactant to stabilize the suspension. The surfactants may be cationic, anionic, or non-ionic. Further, the surfactants may be polar molecules that may absorb microwave energy as well. Surfactants that may be used include, for example, polyethylene oxide (PEO), sodium laurel sulfate, sodium stearate, or other materials, such as longchain fatty acids, triglycerides, and the like.

[0024] Liquid susceptor agents (LSA) suitable for patterning of non-polar polymer powder surface may be selected or designed for application using an inkjet print head. Examples of types of such materials which are suitable for inkjet application include dispersions of electrically conductive carbon particles, such as carbon black, graphite, fullerenes, carbon nanotubes, graphene, and the like. Other suitable materials may include dispersions of metal nano-particles, such as nanoparticles of silver, gold, or copper, among others. The LSA may include dispersions of inorganic conductive and semi-conductive carbides, such as SiC, TiC, or WC, and the like. Further materials that may be used in the dispersions include conductive and semi-conductive metal oxides and nitrides, such as indium tin oxide (ITO), TiN, CuO, Cu 2 0, reduced non-stoichiometric metal oxides, and the like.

Ferromagnetic oxides, such as Fe 3 0 4 , Fe 2 0 3 , Co 3 0 4 , complex ferrites, and the like, may also be used.

[0025] The absorption of microwave energy by a bulk amount of a build material may be non-linear, making the use of microwave energy for a bulk energy source problematic. The use of microwave energy in bulk heating systems may be difficult to control, which may lead to runaway reactions that fuse portions of the build material bed outside of the areas treated with the LSA. In examples described herein, a microwave tip emitter may be energized in the region of an LSA to control the applied energy. Further, the energy applied at a microwave tip may be monitored and controlled using a feedback loop to detect energy reflected from the surface.

The process may be accelerated by the use of a microwave head that includes a number of microwave tips, each with its own power supply and feedback loop.

[0026] Fig. 1 is a schematic diagram of a selective solidification process 100 using a print head 102 to apply a liquid susceptor agent (LSA) 104 to a bed 106 of build material and a microwave head 108 to apply energy proximate to the LSA 104, in accordance with examples. As used herein, proximate indicates that a microwave tip of the microwave head 108 is sufficiently close to an area of LSA 104 so as to cause a temperature increase of the LSA 104 from the microwave energy that fuses the build material. In some examples, the microwave tip may be proximate to the LSA 104 when the distance from the microwave tip to the LSA 104 is less than about 0.5 mm, less than about 1 mm, less than about 1 .5 mm, or greater, depending on the energy applied to the microwave tip.

[0027] The print head 102 may use inkjet printing technology to apply the LSA 104. In some examples, the print head 102 may be part of an assembly used to form a layer of build material over the bed 106. In these examples, the print head 102, may be moved 1 10 across the bed 106 once or multiple times to apply the layer of build material, and print the pattern of the LSA 104 over the build material. In some examples, a separate unit, termed a recoater or wiper mechanism 1 12, may be used to level the bed 106. In some examples, the print head 102 and the microwave head 108 may be combined into a single head.

[0028] After the application of the LSA 104 in a pattern over the bed 106, the microwave head 108 may be moved 1 14 across the bed 106. Microwave energy may be applied to the bed 106 proximate to the LSA 104, for example, from an array of microwave tips mounted along the microwave head, as described with respect to Fig. 3. The determination of which tips to activate may be based on a build map of the LSA 104 location, as described herein. The application of the microwave energy may be controlled by measuring reflected energy from the build material proximate to the LSA 104, as the build material fuses. The determination of the location of the LSA 104 for application of the microwave energy on the bed 106 may be made by reading a build file that includes a build map of the locations for each layer. In other examples, the LSA 104 may be detected by a sensor, such as an optical sensor that detects the LSA 104 based on color or other optical properties.

[0029] The bed 106 may be supported by a build platform 1 14. After the fusing of the build material in the bed 106 proximate to the LSA 104, the build platform 1 16 may be lowered 1 18 to allow the application of a new layer of build material to the bed 106.

[0030] Fig. 2 is a cross-sectional view 200 of a microwave tip 202 illustrating the field 204 of microwave energy emanating from the microwave tip 202, in accordance with examples. As described with respect to Fig. 3, an array of microwave tips may be mounted along a microwave head. In this example, a waveguide 206 is used to convey microwave energy 208 from a source to a coaxial cable 210. The coaxial cable 210 conveys the microwave energy 208 to the microwave tip 202. The microwave energy emanates from the microwave tip 202 creating the field 204. Accordingly, the distance of the microwave tip 202 to a surface below the microwave tip 202 affects the amount of microwave energy that may be conveyed to the surface.

[0031] Fig. 3 is a cross-sectional view 300 of an array of microwave tips 302 in a line on a microwave head 304 proximate to a bed 306 of build material, in accordance with examples. Insulation, such as insulating sheaths 308, may isolate the microwave tips 302 from each other, allowing a focused application of microwave energy on to the surface 310.

[0032] The microwave tips 302 serve a similar purpose as a heating or fusing lamp in a 3D printing type process, but with greater selectivity. The use of individual power supplies for each of the microwave tips 302 may allow the application of fields 312 of microwave energy to be applied to the surface 310 of the bed 306 of build material proximate to LSA 314 that has been applied to the bed 306, for example, by a print head. The energy density of the fields 312 near the tips may differ by about 3 orders of magnitude over a distance from a microwave tip 302 from 1 millimeter (mm) to 7 mm. The build material used to form the bed may be a fine powder, for example, about 50 micrometers, about 100 micrometers, about 200 micrometers, or about 500 micrometers in a largest dimension. This may help the energy from the microwave field to fuse the build material, as the fields 312 may completely encompass build material particles that are in contact with the LSA. Further, varying the height of the microwave tips 302 above the surface 310 of the bed of build material may be used to adjust the delivery of energy to the LSA 314 on the surface. Further, the energy coupling at an individual tip 316 may be monitored and controlled in real time, for example, using a phase detection apparatus as described herein.

[0033] The microwave head 304 is not limited to a single array of microwave tips 302. In examples, multiple arrays of microwave tips 302 may be present, wherein each array of microwave tips 302 is offset from other arrays of microwave tips 302, decreasing the space between microwave tips 302 and the LSA 314 on the surface 310 of the bed 306 of build material. A microwave head 304 may include two arrays, three arrays, four arrays, or more arrays of microwave tips 302, depending, for example, on the desired resolution of the application of microwave energy. This may allow the application of microwaves to LSA 314 that land between microwave tips 302 in the first array, such as the intermediate line of LSA 318.

[0034] Fig. 4 is a plot 400 of an open load intensity 402 of microwave energy versus frequency that may be used for a solidification process, in accordance with examples. In the plot 400, the x-axis 406 represents the frequency of the microwave energy in gigahertz, while the y-axis 404 represents the intensity of the reflected microwave energy that is applied in decibels (dB). In this example, the peak 408 of the open load intensity 402 of the microwave energy is at about 2.41 GHz. A very narrow band for the microwave energy may allow the microwave energy to be tuned to a strong absorption frequency for the susceptor used, while lowering the total amount of microwave energy absorbed by other materials in the bed.

[0035] Fig. 5 is a cross-sectional view 500 of a coupon 502 of solidified build material that has been further fused by the application of microwave energy from a microwave tip 504, in accordance with examples. The coupon 502 was prepared using a 3D printing process, and then treated using a microwave process at room temperature. The portion 506 of the coupon 502 that was solidified using the MJF process has a more granular appearance than the portion 508 of the coupon 502 that has been further fused using the microwave energy. The cross-sectional view 500 illustrates that the fusion using microwave energy follows a well behaved thermal process. At 100 watts (W), the portion 508 of the coupon 502 fused by the microwave energy showed substantial melting within 100 milliseconds (ms).

[0036] Fig. 6 is a schematic diagram of a power circuit 600 for applying microwave energy through a microwave tip while measuring a phase of energy reflected from a surface to the microwave tip, in accordance with examples. The power circuit 600 uses a heterodyne detection scheme to monitor reflected power by determining the phase of the reflected power. Accordingly, the power circuit 600 includes a feedback detector that may be used to control the energy used in a fusing operation.

[0037] The power circuit 600 includes two oscillators 602 and 604. The first oscillator 602 provides a microwave signal at a first frequency to a power divider 606. The power divider 606 divides the microwave signal into two components. The first component, carried by line 608, is provided to a circulator 610. The circulator 610 is a passive, nonreciprocal three port device in which a microwave signal entering any port is transmitted to the next port in the rotation. In this example, the first component, carried by line 608, enters the circulator 610 through port 1 and is transmitted out of the circulator 610 through port 2. Accordingly, the first component is transmitted to a microwave tip 612 to be imposed on the sample. The second component from the power divider 606, carried by line 614, is transmitted to a frequency mixer 616. [0038] The second oscillator 604 provides a microwave signal at a second frequency to a power divider 618. In the power divider 618, the microwave signal at the second frequency is divided into two components. A first component is carried by line 620 to the frequency mixer 616. In the frequency mixer 616, the signal at the first frequency, carried by line 614, and the signal at the second frequency, carried by line 620, are combined to create a new signal that is the first frequency minus the second frequency. The new signal, carried by line 622, is provided to a lock-in amplifier 624 as a reference signal. The second component at the second frequency is carried from the power divider 618 by line 626 to frequency mixer 628.

[0039] Reflected energy from the sample is received by the microwave tip 612, and enters the circulator 610 through port 2. This energy is transmitted from the circulator 610 out port 3, and is carried by line 630 to frequency mixer 628. In frequency mixer 628, the signal at the second frequency and the reflected energy from the sample are combined to create another new signal that is the first frequency minus the second frequency plus a phase shifted component from the reflected energy. This is provided by line 632 to the lock-in amplifier 624 as a sample signal.

[0040] In the lock-in amplifier 624, the sample signal and the reference signal are multiplied and integrated, attenuating the first and second frequencies, and noise components, allowing the detection of the phase shifted frequency. The remaining direct-current signal may be used to determine the amount of reflected energy. This may be used in a control scheme to adjust the amount of power applied to the sample, for example, reducing the power as more energy is reflected to lower the probability of a run-away reaction.

[0041] Fig. 7 is a plot 700 of a series of runs 702 illustrating the repeatability of the selective solidification of a bed of build material, in accordance with examples. In the plot 700, the phase response is charted along the y-axis 704, while the height of the tip above the surface is charted along the x-axis 706. This plot 700 illustrates the repeatability of the phase measurement, indicating the usefulness of the phase measurement for control of the application of microwave energy.

[0042] Fig. 8 is a plot 800 of a series of runs 802 illustrating the dependence of the phase on tip height during the selective solidification of a bed of build material, in accordance with examples. In the plot 800, the phase response is charted along the y-axis 804, while the tip height is charted along the x-axis 806.

[0043] Fig. 9 is a plot 900 of heating profiles at a fixed tip height of 1 mm based on the application of different energies to the bed of build material, in accordance with examples. In the plot 900, the temperature of the sample, measured at the spot of maximum energy exposure, is charted along the y-axis 902. The time is charted along the x-axis 904. As the power applied to microwave tip is increased, the heating profile is also increased. In the plot, this is shown by comparing a heating profile 906, run at 10 W, to a heating profile 908, run at 25 W. Other heating profiles shown include a heating profile 910, run at 12.5 W, a heating profile 912, run at 15 W, and a heating profile 914 run at 20 W.

[0044] Fig. 10 is a plot 1000 of reflected power and plastic temperature rise at a fixed power and tip height, in accordance with examples. In the plot 1000, the X axis 1002 represents the time. The temperature 1004 of the sample at the spot of maximum heating is charted along the left y-axis 1006. The reflected amplitude 1008 is charted along the right y-axis 1010. As can be seen in this plot 1000, as the temperature of the sample increases the amount of energy reflected by the sample also increases.

[0045] This may be used to control the energy applied to the sample, for example, shifting a microwave head to a new region when the reflected energy reaches a selected level or reducing power to particular microwave tips as the reflected energy from those microwave tips reaches a selected level.

[0046] As described, the techniques herein may be used in a 3D printer to form 3D objects. Any number of printer configurations may use microwave energy for solidification. In one example, the 3D printer described with respect to Figs. 1 1 and 12 may use the microwave fusing technique. However, the techniques are not limited to this configuration.

[0047] Fig. 1 1 is a drawing of a 3D printer 1 100, in accordance with examples. The 3D printer 1 100 may be used to generate a 3D object from a build material, for example, on a build platform. The build material may be a powder, and may include a plastic, a metal, a glass, or a coated material, such as a plastic-coated glass powder, among others. The build material may absorb very little microwave energy when no SLA is applied thereto, to allow the use of an LSA to fuse parts, as described herein.

[0048] The printer 1 100 may have covers or panels over compartments 1 102 for internal material vessels that hold build material. The material vessels may discharge build material through feeders into an internal conveying system for the 3D printing. The printer 1 100 may have a controller to adjust operation of the feeders to maintain a desired composition of build material including a specified ratio of materials in the build material. The internal material vessels may be removable via user-access to the compartments 1 102. The printer 1 100 may have a housing and components internal to the housing for handling of build material. The printer 1 100 has a top surface 1 104, a lid 1 106, and doors or access panels 1 108. The access panels 1 108 may be locked during operation of the 3D printer 1 100. The printer 1 100 may include a compartment 1 1 10 for an additional internal material vessel such as a recovered material vessel that recovers unfused or excess build material from a build enclosure of the printer 1 100.

[0049] As described in detail herein, build material may be added or removed from the 3D printer through build material containers that are horizontally inserted into supply stations. The supply stations may include a new supply station 1 1 12 for the addition of new build material, and a recycle supply station 1 1 14 for the addition of recycled build material. As described in examples, the recycle supply station 1 1 14 may also be used to offload recovered build material, for example, from the recovered material vessel. In one example, a single supply station may be provided which may be used for both adding new build material and for removing recycled build material from the printer.

[0050] In some examples, the 3D printer 1 100 may use a print liquid, such as a liquid susceptor agent (LSA), for a selective fusing process. Other liquids may be used for other purposes, such as decoration, or other fusing techniques. For examples of a 3D printer 1 100 that employ a print liquid, a print-liquid system 1 1 16 may be included to receive and supply print liquid for the 3D printing. The print-liquid system 1 1 16 includes a cartridge receiver assembly 1 1 18 to receive and secure removable print-liquid cartridges 1 120. The print-liquid system 1 1 16 may include a reservoir assembly 1 122 having multiple vessels or reservoirs for holding print liquid collected from the print-liquid cartridges 1 120 inserted into the cartridge receiver assembly 1 1 18. The print liquid may be provided from the vessels or reservoirs to the 3D printing process, for example, to a print assembly or print head above a build enclosure and build platform.

[0051] The 3D printer 1 100 may also include a user control panel or interface 1 124 associated with a computing system or controller of the printer 1 100. The control interface 1 124 and computing system or controller may provide for control functions of the printer 1 100. The fabrication of the 3D object in the 3D printer 1 100 may be under computer control. A data model of the object to be fabricated and automated control may direct the layered manufacturing and additive fabrication, including the locations of the LSA for targeted application of microwave energy. The data model may be, for example, a computer aided design (CAD) model, a similar model, or other electronic source. As described with respect to Fig. 14, the computer system, or controller, may have a hardware processor and memory. The hardware processor may be a microprocessor, CPU, ASIC, printer control card, or other circuitry. The memory may include volatile memory and non-volatile memory. The computer system or controller may include firmware or code, e.g., instructions, logic, etc., stored in the memory and executed by the processor to direct operation of the printer 1 100 and to facilitate various techniques discussed herein.

[0052] Fig. 12 is a schematic diagram of a 3D printer 1200 having an internal new material vessel 1202 that discharges new build material through a new feeder 1204 into a conveying system 1206, in accordance with examples. Like numbered items are as described with respect to Fig. 1 1 . The printer 1200 may include a recycle material vessel 1208 to discharge recycle build material through a recycle feeder 1210 to the conveying system 1206. The printer 1200 may have a controller to adjust operation of the feeders 1204 and 1210 to maintain a composition and discharge rate of the build material for the 3D printing. Further, the printer 1200 may include a recovered material vessel 1212 to discharge recovered material 1216 through a recovery feeder 1214 into the conveying system 1206. The conveying system 1206 may transport the build material to a dispense vessel 1218 which may supply build material for 3D printing, for example, to a dispensing bar or

multifunctional print head. In the illustrated example, the dispense vessel 1218 is disposed in an upper portion of the 3D printer 1200. Moreover, although the conveying system 1206 for the build material is depicted outside of the 3D printer 1200 for clarity in this schematic view, the conveying system 1206 is internal to the housing of the printer 1200.

[0053] The 3D printer 1200 may form a 3D object from the build material on a build platform 1220 associated with a build enclosure 1222. The 3D printing may include selective layer sintering (SLS), selective heat sintering (SHS), electron beam melting (EBM), thermal fusion, and fusing agent, or other 3D printing and additive manufacturing (AM) technologies to generate the 3D object from the build material.

In examples described herein, the sintering or fusing process is based on the application of microwave energy proximate to a liquid susceptor agent applied in a pattern over the build material.

[0054] Recovered build material 1224, for example, non-solidified or excess build material, may be recovered from the build enclosure 1222. The recovered build material 1224 may be treated and returned to the recovered material vessel 1212. The use of an LSA with the targeted application of microwave energy may decrease the total heat exposure of the material, which may allow more recycled material to be used in blends with new material in the build process. Further, the printer 1200 may include a new supply station 1 1 12 and a recycle supply station 1 1 14 to hold build material containers inserted by a user along a horizontal, or generally horizontal, axis.

[0055] Lastly, as noted, the build material including the first material and the second material may be powder. A powder may be a granular material with a narrow size distribution, such as beads, or other shapes of small solids that may flow and be conveyed in an air stream. The granular material may be about 50 micrometers in diameter to about 500 micrometers in diameter, as described herein. In some example, larger materials, for example, having diameters of about 1 millimeter or greater, may be used. As used herein, the term“powder” as build material can, for example, refer to a powdered, or powder-like, material which may be layered and sintered via an energy source or fused via a fusing agent, or a fusing agent and energy source in a 3D printing job. In some examples, the build material may be formed into a shape using a chemical binder, such as a solvent binder or a reaction promoter. The build material can be, for example, a semi-crystalline thermoplastic material, a metal material, a plastic material, a composite material, a ceramic material, a glass material, a resin material, or a polymer material, among other types of build material, including added fibers. In examples described herein, the build material does not absorb microwave radiation, for example, at about 2.4 GHz.

[0056] Fig. 13 is a process flow diagram of a method 1300 for selectively solidifying a bed of build material using microwave energy, in accordance with examples. The method 1300 begins at block 1302, when powder is layered over a build platform, for example, using the apparatus described with respect to Fig. 1 . At block 1304, a liquid susceptor agent (LSA) is applied over the layer of powder on the build platform in a pattern of an object being printed. This may be performed by the print head described with respect to Fig. 1 . In some examples, a single nozzle may be used to apply the LSA, for example, drawing the pattern on the bed.

[0057] At block 1306, the microwave head is moved across the platform. At block 1308, microwave tips over target zones, for example, proximate to the applied LSA are activated, for example, as described with respect to Fig. 3. At block 1310, the energy applied through the microwave tips is adjusted based on the feedback received from the detection of reflected energy, for example, as described with respect to Fig. 6.

[0058] Fig. 14 is a block diagram of a system 1400 for using microwave energy to selectively solidify build material in a bed, in accordance with examples. The controller 1400 may be part of the main controller for the 3D printer, or a separate controller associated with the supply stations.

[0059] The controller 1400 may include a processor 1402, which may be a microprocessor, a multi-core processor, a multithreaded processor, an ultra-low voltage processor, an embedded processor, or other type of processor. The processor 1402 may be an integrated microcontroller in which the processor 1402 and other components are formed on a single integrated circuit board, or a single integrated circuit, such a system on a chip (SoC). As an example, the processor 1402 may include a processor from the Intel® Corporation of Santa Clara, CA, such as a Quark™, an Atom™, an i3, an i5, an i7, or an MCU-class processor. Other processors that may be used may be obtained from Advanced Micro Devices, Inc. (AMD) of Sunnyvale, CA, a MIPS-based design from MIPS Technologies, Inc. of Sunnyvale, CA, an ARM-based design licensed from ARM Holdings, Ltd. or customer thereof, or their licensees or adopters. The processors may include units such as an A5-A10 processor from Apple® Inc., a Snapdragon™ processor from Qualcomm® Technologies, Inc., or an OMAP™ processor from Texas Instruments, Inc.

[0060] The processor 1402 may communicate with a system memory 1404 over a bus 1406. Any number of memory devices may be used to provide for a given amount of system memory. The memory may be sized between about 2 GB and about 64 GB, or greater. The system memory 1404 may be implemented using non volatile memory devices to protect from power loss, such as static RAM (SRAM), or memory modules having backup power, for example, from batteries, super capacitors, or hybrid systems. The system memory 1404 stores operating programs, results, and the like, for example, including a build map of LSA locations for targeting the application of microwave energy.

[0061] Persistent storage of information such as data, applications, operating systems, and so forth, may be performed by a mass storage 1408 coupled to the processor 1402 by the bus 1406. The mass storage 1408 may be implemented using a solid-state drive (SSD). Other devices that may be used for the mass storage 1408 include flash memory cards, such as SD cards, microSD cards, xD picture cards, and the like, and USB flash drives. In some examples, the controller 1400 may have an accessible interface, such as a USB connection, an SD card socket, or a micro SD socket to all the insertion of memory devices with build plans, instructions, and the like.

[0062] In some examples, the mass storage 1408 may be implemented using a hard disk drive (HDD) or micro HDD. Any number of other technologies may be used in examples for the mass storage 1408, such resistance change memories, phase change memories, holographic memories, or chemical memories, among others.

[0063] The components may communicate over the bus 1406. The bus 1406 may include any number of technologies, such as industry standard architecture (ISA), extended ISA (EISA), peripheral component interconnect (PCI), peripheral component interconnect extended (PCIx), PCI express (PCIe), or any number of other technologies. The bus 1408 may include proprietary bus technologies, for example, used in a SoC based system. Other bus systems may be included, such as an I2C interface, an SPI interface, point to point interfaces, and a power bus, among others. A network interface controller (NIC) 1410 may be included to provide communications with a cloud 1412 or network, such as a local area network (LAN), a wide area network (WAN), or the Internet. The NIC 1410 may be used to download build plans from devices in the cloud, allow control of operations from devices in the cloud, and the like.

[0064] The bus 1406 may couple the processor 1402 to interfaces 1414 and 1416 that are used to connect to other devices in the 3D printer. For example, a sensor interface 1414 may be used to couple to level sensors 1416 to detect if a container holding a liquid susceptor agent has sufficient liquid for a build. Weight sensors 1418 may be used to determine the weights of various containers or vessels, such as the supply stations, the new material vessel, the recycle material vessel, or the recovered material vessel, among others. Energy sensors 1420, such as the lock-in amplifier 624 described with respect to Fig. 6, may be used to detect reflected energy from a sample surface for control of applied energy.

[0065] An actuator interface 1416 may be included to control various actuators in the 3D printer. The actuators may include feeders 1422 to meter the amount of build material released from storage vessels. The feeders 1422 may use stepper motors, server motors, or other kinds of motors that have rotation controlled by the supplied power signal, allowing the number of revolutions per minute in total revolutions to be controlled by the actuation. In some examples, a sensor may be used to determine the number of revolutions, for example, position sensors may be used to count the number of revolutions of the feeders 1422. Blowers 1424 may be used to convey material through the printer to a build platform, as described with respect to Figs. 1 1 and 12. A print head 1426, such as an inkjet print head, may be used to apply an LSA over a layer of build material, as described with respect to Fig. 1 . The print head 1426 may also include, or be part of, an apparatus to apply and smooth a layer of build material over a build platform. A microwave head 1428 may be moved over the bed of build material to place microwave tips on the microwave head proximate to LSA applied over the build material. A microwave energy driver 1430 may be used to apply microwave energy to microwave tips proximate to LSA applied over the bed.

[0066] While not shown, various other input/output (I/O) devices may be present within, or connected to, the controller 1400. For example, a display panel may be included to show information, such as build information, action prompts, warnings of incorrect material, or messages concerning status of doors, build material containers, and the like. Audible alarms may be included to alert a user of a condition. An input device, such as a touch screen or keypad may be included to accept input, such as instructions on new builds, and the like. Other sensors and actuators that may be used in the 3D printer include door locks, build material container sensors, and the like.

[0067] The mass storage 1408 may include modules to control the

solidification of the build material through the application of microwave energy.

Although shown as code blocks in the mass storage 1408, it may be understood that any of the modules may be fully or partially implemented in hardwired circuits, for example, built into an application specific integrated circuit (ASIC). The modules may generally be used to implement the functions described with respect to Fig. 13.

[0068] A director module 1432 may implement the general functions for setting up the printer and build procedures. These may include the general operations not included in one of the more specific procedures, such as getting job instructions for applying the LSA pattern, estimating revolutions used to dispense or add build material, and moving recovered build material into a recycle material vessel past the recycle supply station.

[0069] A dispense module 1434 may implement the actions used to dispense build material from a build material container, such as monitoring the number of revolutions of the build material container during the dispense procedure and the level of the vessel accepting the build material, among others.

[0070] A print module 1436 may implement the printing procedure described with respect to Fig. 13. This may include the actions used to add a layer of powder to the bed of build material, and the printing of the LSA over the print bed in a pattern. [0071] A microwave energy control module 1438 may control the application of microwave energy to the bed of build material proximate to the LSA patterns. The microwave energy control module 1438 may include an apply microwave energy module 1440 to activate the microwave energy driver 1430 to apply microwave energy to microwave tips, when the microwave tips are proximate to the LSA. A detect energy module 1 142 may detect the energy feedback from the bed as the build material fuses. This may use the techniques described with respect to Fig. 6 to monitor the phases of the reflected energy. An adjust energy output module 1444 may use the detected energy to adjust the applied microwave energy, as described herein.

[0072] Fig. 15 is a block diagram of a non-transitory, machine readable medium 1500 comprising code to direct a processor 1502 to control the application of energy to selectively solidify build material in a bed, in accordance with examples. The processor 1502 may access the non-transitory, machine readable medium 1500 over a bus 1504. The processor 1502 and bus 1504 may be as described with respect to the processor 1402 and bus 1406 of Fig. 14. The non-transitory, machine readable medium 1500 may include devices described for the mass storage 1408 of Fig. 14 or may include optical disks, thumb drives, or any number of other hardware devices.

[0073] The non-transitory, machine readable medium 1500 may include code 1506 to direct the processor 1502 to apply microwave energy to microwave tips that in the vicinity of LSA patterns, for example, as determined from a build map of the LSA patterns, or by detecting the LSA on the surface of the build material. Code 1508 may be included to direct the processor 1502 to detect microwave energy reflected from a surface, for example, by monitoring a DC signal from a lock-in amplifier that is detecting the phase of the reflected energy, as described with respect to Fig. 6. The non-transitory, machine readable medium 1500 may also include code 1510 to direct the processor 1502 to adjust the microwave power applied to a microwave tip, or the location of the microwave tip based, at least in part, on the reflected energy.

[0074] While the present techniques may be susceptible to various

modifications and alternative forms, the examples discussed above have been shown only by way of example. It is to be understood that the technique is not intended to be limited to the particular examples disclosed herein. Indeed, the present techniques include all alternatives, modifications, and equivalents falling within the scope of the present techniques.