Method of jetting print material and method of printing

Abstract

To provide a method of printing a three-dimensional object which improves the quality of three-dimensional objects made through three-dimensional printers.SOLUTION: The method comprises: supplying an electrically conductive print material 104 to a plurality of ejector conduits 106 arranged in an array, the ejector conduits comprising first ends 106A configured to accept the print material and second ends 106B comprising ejector nozzles 108; advancing the print material into one or more of the ejector conduits of the array until the print material is arranged in one or more of the ejector nozzles; flowing an electrical current through the print material positioned in the ejector nozzles, thereby heating and expanding the print material in the ejector nozzles so as to eject the print material from the ejector nozzles onto a print substrate; and repeating both the step of advancing and the step of flowing the electrical current through the print material to form a three-dimensional object on the print substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure is directed to methods of jetting printing material, including methods of 3D printing. [Background technology]

[0002] Melting of solid materials, including materials in the form of solid filaments, is commonly used in 3D printing technology. It is well understood that when a phase change or heating of the material occurs, the material generally expands and, in the case of a phase change from solid to liquid, becomes flowable. Printing materials are often melted to allow the material to flow and deposit on a substrate, from which a 3D object is formed. As a specific example, liquid three-dimensional printers for building 3D objects from molten aluminum are known in the art.

[0003] One such 3D printer is disclosed in U.S. Patent No. 9,616,494. The 3D printer functions by ejecting molten aluminum droplets in response to DC pulses applied by an electromagnetic coil. A platen, which targets the droplets, translates to allow the droplets to connect and accumulate, generating a three-dimensional object. However, the molten aluminum droplets ejected from this 3D printer have diameters of approximately 0.5 mm or larger. This allows for high-volume, high-throughput production of metal parts. However, relatively large droplet sizes can result in undesirable porosity in the printed 3D object, as well as uneven build surfaces, unwelded droplets, and shape variations during production. All of this can lead to poor physical properties, such as insufficient tensile strength, as well as poor cosmetic appearance in the final object and / or an inability to print objects with very fine detail.

[0004] Therefore, a method and system for improving the quality of three-dimensional objects produced from a three-dimensional printer, such as a liquid metal printer, would represent an advancement in the art. Summary of the Invention

[0005] One embodiment of the present disclosure is directed to a three-dimensional ("3D") printer. The 3D printer includes a plurality of ejector conduits arranged in an array, each of the ejector conduits having a first end positioned to receive printing material, a second end including an ejector nozzle, and a passage defined by an inner surface of the ejector conduit to allow printing material to pass through the ejector conduit from the first end to the second end, the ejector nozzle including a first electrode and a second electrode, at least one surface of the first electrode exposed within the passage and at least one surface of the second electrode exposed within the passage. a current pulse generating system in electrical contact with the ejector nozzle of each of the ejector conduits, the current pulse generating system configured to pass a current between the first electrode and the second electrode to provide sufficient thermal expansion to eject the conductive printing material when the conductive printing material is disposed within the ejector nozzle; and a positioning system for controlling the relative position of the array with respect to the printed circuit board during operation of the 3D printer in a manner that enables the printed circuit board to receive jettable printing material from the ejector nozzle of each of the plurality of ejector conduits.

[0006] The present disclosure is also directed to a printer ejection mechanism comprising: a plurality of ejector conduits arranged in an array, each ejector conduit having a first end positioned to receive printing material, a second end including an ejector nozzle, and a passage defined by an inner surface of the ejector conduit to allow the printing material to pass through the ejector conduit from the first end to the second end, the ejector nozzle including a first electrode and a second electrode, at least one surface of the first electrode exposed within the passage and at least one surface of the second electrode exposed within the passage; and a current pulse generation system in electrical contact with the ejector nozzle of each of the plurality of ejector conduits, the current pulse generation system configured to pass a current between the first electrode and the second electrode to provide sufficient thermal expansion to eject the conductive printing material when the conductive printing material is disposed within the ejector nozzle.

[0007] Another embodiment of the present disclosure is directed to a three-dimensional ("3D") printer ejection mechanism. The 3D printer ejection mechanism includes a plurality of ejector conduits arranged in an array, each of which has a first end configured to receive printing material, a second end including an ejector nozzle, and a passageway defined by an inner surface of the ejector conduit for allowing the printing material to pass through the ejector conduit from the first end to the second end. The ejector nozzle includes a first electrode, a second electrode, and an electrically insulating material disposed laterally between the first and second electrodes, wherein at least one surface of the first electrode is exposed within the passageway, and at least one surface of the second electrode is exposed within the passageway.

[0008] Another embodiment of the present disclosure is directed to a method for printing a three-dimensional object. The method includes supplying a conductive printing material to a plurality of ejector conduits arranged in an array, the ejector conduits comprising a first end configured to receive the printing material and a second end comprising an ejector nozzle, advancing the printing material into one or more of the ejector conduits of the array until the printing material is disposed within an ejector nozzle of the one or more ejector conduits, passing an electric current through the printing material disposed within at least one of the ejector nozzles to heat and expand the printing material in at least one of the ejector nozzles to eject at least a portion of the printing material from the at least one ejector nozzle onto the printed circuit board, and repeating both advancing the printing material and passing an electric current through the printing material to form the three-dimensional object on the printed circuit board.

[0009] Yet another embodiment of the present disclosure is directed to a method for ejecting printing material from a printer ejection mechanism, the method including: supplying electrically conductive printing material to a plurality of ejector conduits arranged in an array, the ejector conduits having a first end configured to receive the printing material and a second end having an ejector nozzle; advancing the printing material into one or more of the ejector conduits of the array until the printing material is disposed within an ejector nozzle of the one or more ejector conduits; and passing an electric current through the printing material disposed in at least one of the ejector nozzles to heat and expand the printing material in at least one of the ejector nozzles to eject at least a portion of the printing material from at least one of the ejector nozzles.

[0010] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present teachings, as claimed. [Brief explanation of the drawings]

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present teachings and, together with the description, serve to explain the principles of the present teachings. [Figure 1] 1 illustrates an example of a printer jetting mechanism, according to one embodiment of the present disclosure. [Figure 2] 1 illustrates a top view of a printer jetting mechanism, according to one embodiment of the present disclosure. [Figure 3] 1 illustrates a bottom view of an ejector nozzle with an electrode pair, according to one embodiment of the present disclosure, a current pulse generating system is illustrated in electrical contact with the electrode pair. [Figure 4] 1 illustrates an example of a schematic cross-sectional view of an ejector conduit, also illustrating a current pulse generation system that can be used to generate a current pulse across an electrode disposed within an ejector nozzle of the ejector conduit, according to an embodiment of the present disclosure. [Figure 5] 1 illustrates an example of a schematic cross-sectional view of an ejector conduit, also illustrating a current pulse generation system that can be used to generate a current pulse across an electrode disposed within an ejector nozzle of the ejector conduit, according to an embodiment of the present disclosure. [Figure 6] 1 illustrates a schematic bottom view of an ejector nozzle having a square cross-section flow passage, according to one embodiment of the present disclosure. [Figure 7] 1 illustrates a schematic bottom view of an ejector nozzle having a square cross-section flow passage, according to one embodiment of the present disclosure. [Figure 8] 1 illustrates a schematic cross-sectional view of an ejector nozzle having an inner diameter d i according to one embodiment of the present disclosure. [Figure 9] 1 illustrates a schematic top view of a printer ejection mechanism comprising rows of staggered ejector conduits, according to one embodiment of the present disclosure. [Figure 10] 1 illustrates a schematic cross-sectional side view of an ejector conduit according to one embodiment of the present disclosure. [Figure 11] 1 illustrates a schematic cross-sectional side view of an array of ejector conduits, according to one embodiment of the present disclosure. [Figure 12A] 1 illustrates a schematic cross-sectional side view of an ejector conduit having printing material therein that may be used in the printer jetting mechanisms described herein, according to one embodiment of the present disclosure. [Figure 12B] 12B illustrates a schematic cross-sectional side view of the ejector conduit of FIG. 12A after vaporization of a portion of the printing material and ejection of another portion of the printing material below the vaporized portion, according to one embodiment of the present disclosure. [Figure 13] 1 illustrates a schematic cross-sectional side view of an ejector conduit with a vent, according to one embodiment of the present disclosure. [Figure 14A] 1 illustrates a schematic bottom view of an ejector nozzle with multiple vents, according to one embodiment of the present disclosure. [Figure 14B] 14B illustrates a schematic cross-sectional view of a portion of the ejector conduit 106 along line AA including the ejector nozzle of FIG. 14A, according to one embodiment of the present disclosure. [Figure 15] FIG. 1 is a block diagram of a 3D printer according to one embodiment of the present disclosure. [Figure 16] FIG. 1 illustrates a schematic side view of a printer jetting mechanism with multiple ejector conduits that simultaneously eject droplets to print a 3D object on a printed circuit board, according to one embodiment of the present disclosure. [Figure 17] 1 is a flow diagram of a method for ejecting printing material from a printer ejection mechanism according to one embodiment of the present disclosure. [Figure 18] FIG. 1 is a schematic diagram of a 3D printer according to one embodiment of the present disclosure.

[0012] It should be noted that some details of these figures have been simplified and strict structural accuracy, detail, and scale are not maintained, but rather are drawn to facilitate understanding of the embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0013] Reference will now be made in detail to embodiments of the present teachings, examples of which are illustrated in the accompanying drawings, wherein like reference numerals are used to designate the same elements throughout. In the following description, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific exemplary embodiments in which the present teachings may be practiced. Accordingly, the following description is by way of example only.

[0014] The present disclosure is directed to a printer jetting mechanism comprising a plurality of ejector conduits arranged in a jet array and a 3D printer using the printer jetting mechanism. A method of using such a jetting mechanism to jet a printing material is also disclosed. The printer jetting mechanism is designed to use an electric current to induce thermal expansion of the printing material as a force for jetting, as described in more detail herein. The jetting mechanism and printing method disclosed herein can provide one or more of the following advantages: the ability to selectively jet a wide range of metals and other materials, the ability to jet selectable drop volumes, the ability to jet small drop sizes enabling printing of fine and / or selectable feature sizes, and the ability to print at a relatively high throughput.

[0015] Printer injection mechanism FIG. 1 illustrates an example of a printer jetting mechanism 100 according to one embodiment of the present disclosure. The printer jetting mechanism 100 optionally includes a feeder mechanism 102 for advancing a printing material 104 to be printed. An exemplary printing material 104 is a preformed wire of a selected alloy, or other materials as discussed in more detail below. A plurality of ejector conduits 106 are arranged in an array 107. Each ejector conduit 106 includes a first end 106A positioned to receive the printing material 104 from the feeder mechanism 102. The second end 106B includes an ejector nozzle 108. FIG. 2 illustrates a top view of the printer jetting mechanism 100. A passage 106C defined by the inner surface of each of the ejector conduits 106 allows the printing material 104 to pass through the ejector conduit 106 from the first end 106A to the second end 106B.

[0016] The ejector nozzle 108 includes at least one pair of electrodes, including a first electrode 110 and a second electrode 112, used to supply current to heat the printing material 104. At least one surface of the first electrode 110 is exposed within the passage 106C, and at least one surface of the second electrode 112 is exposed within the passage 106C. A current pulse generating system 114, shown in FIG. 3, is in electrical contact with at least one electrode pair of the ejector nozzle 108 of each of the multiple ejector conduits 106. The current pulse generating system 114 can pass a pulse of current primarily between the first electrode 110 and the second electrode 112 when the conductive printing material 104 is disposed within the ejector nozzle 108.

[0017] Sufficient power is provided to the electrodes 110, 112 to heat the printing material 104 within the ejector nozzle 108, causing the printing material 104 to expand rapidly enough to provide sufficient momentum to eject or jet at least a portion of the printing material from the ejector nozzle 108. The rapid expansion of the printing material that results in the desired ejection of the printing material, also referred to herein as jetting, may or may not include heating that causes a phase change in the printing material, as described in more detail below.

[0018] The electrodes 110 and 112 can be configured to provide electrical contact with the printing material 104. As an example, if the printing material is a solid filament, one or both of the electrodes 110, 112 can be lightly spring loaded using any desired spring mechanism 113 ( FIG. 7 ) or electrode design that positionally biases one or both of the electrodes in the direction of the longitudinal axis 1 of the passageway 106C. In this manner, the electrodes are pressed against the printing material 104 as the printing material 104 is fed into the nozzle 108 during operation of the ejector. Suitable spring mechanisms and / or electrode designs capable of providing such biasing contact force against the filament can be determined by those skilled in the art.

[0019] The electrodes 110, 112 can comprise any material suitable for providing electrical contact to the printing material 104 while withstanding ejector nozzle temperatures during printing. Examples of suitable materials include metals having a higher melting temperature than the printing material, including refractory metals as described herein, aluminum, aluminum alloys (e.g., 1000 series, 2000 series, 3000 series, 4000 series, 5000 series, 6000 series such as 6061 and 6063, and 7000 series aluminum alloys), magnesium, magnesium alloys, iron, iron alloys (e.g., steel), copper, copper alloys (e.g., zinc), nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Suitable alloys of the above metals can include any desired mixtures of metals, such as mixtures of any two or more of the above elemental metals with elemental refractory metals, such as mixtures of two or more of aluminum, magnesium, iron, copper, nickel, titanium, tungsten, or any of the other elemental refractory metals, palladium, silver, any of the other refractory metal alloys listed herein, etc. The electrodes 110 and 112 can be corrosion-resistant. For example, any of the electrodes 110 and 112 described herein are optionally coated with a passivation coating 144 (e.g., FIG. 7 ) including a noble metal, such as palladium, that resists corrosion by the molten printing material. In one example, any of the electrodes herein can include tungsten, another refractory metal, copper, or any of the other metals taught herein as suitable for electrodes, coated with a passivation layer including a noble metal, such as palladium. The use of noble metals as corrosion-resistant coatings on electrodes is generally known.

[0020] The current pulse generating system 114, also referred to herein as a current pulse generating circuit, is capable of generating pulses of current having sufficient amplitude to heat and expand the printing material 104 in a relatively short period of time (e.g., a single current pulse). The short, high current pulse generates sufficient momentum in the heated printing material resulting from thermally driven expansion, causing, for example, detachment and ejection of the printing material 104 from the ejector nozzle 108 during operation of the 3D printer. This can be done without using a magnetic field source, such as an electromagnetic coil or other type of magnet, in conjunction with the current pulse to generate the ejection force. Thus, in this application, it is the expansion of the printing material that primarily drives the ejection, rather than electromagnetic forces.

[0021] Any type of current pulse generating circuit capable of providing pulses of sufficient amperage to achieve the desired heating rate for thermal expansion and ejection of the printing material can be used. Suitable current pulse generating circuits are well known in the art, and any desired current pulse generating system can be used. The current pulse generating system is electrically connected to any one or more of the electrode pairs (e.g., all electrode pairs) in the ejector device described herein, such as the first electrode 110 and second electrode 112 of the ejector nozzle as shown in FIGS. 3, 4, and 5. In one embodiment, the current pulse generating system 114 includes a current source electrically connected to the ejector nozzle 108 (e.g., a current source connected to the first electrode 110 and a current sink electrically connected to the second electrode 112 of the ejector nozzle). In another embodiment, the current pulse generating system 114 includes a voltage source electrically connected to the ejector nozzle 108 (e.g., to apply a desired voltage between the first electrode 110 and the second electrode 112 of the nozzle). Examples of suitable current and voltage sources are well known in the art.

[0022] Referring to FIG. 3 , the circuitry of the current pulse generating system 114 can include a power supply 114a and a switch 114b operated by a pulse control device 114c, such as a pulse generator, waveform generator, or other device capable of generating the desired current pulses. While shown separately in FIG. 3 , the switch 114b can optionally be part of the pulse control device 114c. The pulse control device 114c can be programmable to provide computer control of the current pulse generating system. The power supply 114a can be any power supply, such as a DC power supply or a switching power supply, capable of providing the desired current. The switch 114b can be any switch capable of providing the desired current pulses in combination with the pulse control device 114c. Examples include high-current capable switches, including FET or MEMS switches. As will be understood by those skilled in the art, other circuit components can be optionally included as part of the current pulse generating system 114, such as, for example, amplifiers, resistors, etc. As described herein, the current pulse generating system 114 can be electrically connected to the printing material in the ejector nozzle 108 using electrodes 110 and 112.

[0023] FIG. 4 illustrates an example of a current pulse generating circuit that may be used to provide relatively high current pulses for a small amount of time at a low duty cycle. The current pulse generating system 114 of FIG. 4 charges one or more capacitors using a power supply 114a, which is a DC power supply such as a switching power supply, and multiple FETs (e.g., GaAs FETs or other FETs) that function as switches 114b. The current pulse generating system 114 of FIG. 4 is electrically connected to the printing material in the ejector nozzle 108 using electrodes 110 and 112, as described herein. The charged capacitors can be discharged to provide the desired current pulses 118 across the printing material. A typical circuit design can use a DC voltage source, a high-power operational amplifier with a current feedback resistor, and / or a high-speed, low-series impedance switch such as a GaAs nMOS transistor. Such circuits are generally well known. Rapid bipolar switching can be similarly applied using, for example, a high-current H-bridge. Any other suitable current pulse generating circuit capable of providing suitable current pulses can be used.

[0024] The resistivity of the printing material changes when it is heated and / or undergoes a phase change, which can be taken into account when determining the desired amplitude and / or duration of the current pulse. If desired, the amount of current supplied by the current pulse generating system 114 can be purposefully varied over the duration of the current pulse 118 to provide the desired thermal energy to the printing material despite changes in resistivity that may occur due to heating and / or phase change of the printing material 104.

[0025] In one embodiment, current pulse generating system 114 includes a programmable pulse control device. Pulse control system 160 ( FIG. 4 ) is an example of a programmable pulse control device that includes a pulse controller 162 and a computing system 164. Pulse controller 162 may be, for example, a microcontroller including a CPU 170 and memory 172 that interfaces with the circuit components (e.g., current switches, power supplies, and / or other components) of current pulse generating system 114 to generate current pulses having desired pulse characteristics for heating the printing material when the current pulses pass between first electrode 110 and second electrode 112. Pulse controller 162 may be driven by computing system 164, which may be capable of executing computer-executable instructions embodied in a non-transitory computer-readable medium (e.g., memory 166 of computing system 164). Computing system 164 may be integrated as part of pulse controller 162 itself (e.g., a CPU and memory integrated into pulse controller 162, such as CPU 170 and memory 172, may be used), or may be a separate computer system (as shown in FIG. 4 ), including, for example, memory 166 and CPU 168 interfacing with pulse controller 162. Computer-executable instructions embodied in the non-transitory computer-readable medium of computing system 164 may, among other things, instruct CPU 168 of computing system 164 to determine at least one desired pulse characteristic, such as a pulse length, amplitude, and / or pulse shape, for heating the printing material to cause thermal expansion and ejection of printing material 104 as described herein. Computing system 164 may determine the at least one desired pulse characteristic in any suitable manner, such as by using a mathematical algorithm to calculate pulse characteristics that provide the desired ejection characteristics of printing material 104, and may take into account, for example, the type of printing material, the pulse history of the ejector, and / or feedback from the printer jetting mechanism. Such feedback may include, for example, real-time nozzle temperature, print material temperature, and / or other data.Additional computer-executable instructions embodied in a non-transitory computer-readable medium (e.g., memory 166 or 172) of one or both of computer system 164 and pulse controller 162 are executed by a CPU (e.g., CPU 168 and / or CPU 170) of pulse control system 160 to send commands or electrical signals to a voltage source or current source of the current pulse generating system to cause a current to flow between first electrode 110 and second electrode 112. The resulting current comprises current pulses 118 having at least one pulse characteristic. By controlling the current pulses across first electrode 110 and second electrode 112, the ejection of printing material 104 can be controlled, including drop volume, velocity of the ejected printing material, and ejection rate (e.g., number of ejections per second), etc.

[0026] As described above, when determining the desired pulse characteristics, the computing system 164 can optionally compensate for factors such as the effects of electrical conductivity, thermal expansion, or other temperature-dependent properties of the printing material 104 due to, for example, temperature changes at the nozzle 108 caused by changes in duty cycle. For example, in some cases, the duty cycle may be high, with one pulse quickly following another. This can cause localized increases in temperature in the ejector nozzle 108, ejector conduit 106, and / or adjacent to the ejector nozzle and / or the printing material 104 contained therein compared to lower duty cycle situations. Such temperature changes can affect the expansion and ejection of the printing material. By considering these effects when determining the pulse characteristics, the computing system 164 of the current pulse generation system can control and / or improve the jetting characteristics of the printer jetting mechanism 100.

[0027] FIG. 5 illustrates a current pulse generating circuit similar to that of FIG. 4, except that the current pulse generating circuit of FIG. 5 can be used with an ejector nozzle 108 having two or more pairs of electrodes 110a, 112a, 110b, 112b, and 110c, 112c. While three pairs of electrodes are shown, any number of electrode pairs can be used, such as one to ten electrode pairs, or two to five electrode pairs. Such a design may allow for improved control and / or higher current density through the printed material compared to the single electrode pair design of FIG. 4. For example, multiple electrodes per nozzle may enable variable volume droplet ejection, where the droplet volume of each ejection can be varied by sending current pulses to a desired number of electrode pairs. Thus, smaller droplets can be ejected by pulsing current through a single electrode pair 110 a, 112 a, while larger droplets can be ejected by pulsing current through two electrode pairs 110 a, 112 a and 110 b, 112 b, or three or more electrode pairs. A pulse control system 160, such as that illustrated in Figure 4, can also be used to control the current pulse generating circuit of Figure 5. Any of the devices of the present disclosure can use multiple electrode pairs in the ejector nozzle 108, as described herein.

[0028] The ejector nozzle 108 is an end portion of the ejector conduit 106 and is positioned to eject printing material during operation of the printer ejection mechanism 100. The passage 106C of the ejector nozzle 108 can have the same or a different shape as the passage 106C of the ejector conduit 106. FIG. 3 shows an ejector nozzle 108 having a passage 106C with a circular cross-section bounded by an electrode 110, an electrode 112, and an electrical insulator portion 111 disposed laterally between the electrodes 110 and 112. The electrical insulator comprises an insulating material such as silica or any of the other insulating materials described herein as suitable for the ejector conduit 106. An example of an ejector nozzle 108 with a square cross-section is shown in FIGS. 6 and 7. A square cross-section may potentially provide a more uniformly distributed current flow through the printing material 104 than the circular cross-section of FIG. 3. Any other desired cross-sectional shape, such as other polygonal or elliptical shapes, may be used for the passage 106C.

[0029] Referring to FIG. 8, the ejector nozzle 108 has an inner width d i If the cross section of the passage 106C is not circular, then d i is the length of the shortest straight line between opposing insulator portions 111, where the line passes through the longitudinal axis "l" shown in Figures 1, 6, and 7 of the passage 106C (where the longitudinal axis points into the page in Figures 6 and 7). i The cross section of the ejector nozzle 108 used to determine d lies in a plane that is perpendicular to all directions relative to the longitudinal axis "l" at the point where the cross section intersects the passage 106C. (e.g., d i )d, such as when the value of i If there is more than one possible value for d i is the possible d for the ejector nozzle 108 i The minimum value of d iExemplary values ​​for d include, for example, about 10 micrometers to about 1000 micrometers, about 20 micrometers to about 500 micrometers, about 50 micrometers to about 200 micrometers, or about 100 micrometers. i The length L of the first electrode 110 and the second electrode 112 ranges in size from about 10 micrometers to about 100 micrometers, such as from about 10 micrometers to about 50 micrometers, or from about 10 micrometers to about 25 micrometers. w (FIG. 3) (or the combined length of the multiple electrode pairs when multiple electrode pairs are used, such as in FIG. 5) is, for example, the inner width d i The ejector nozzle 108 may have the same or different design and materials as the rest of the ejector conduit 106. The total length of the ejector conduit 106, including the length of the nozzle, may be, for example, the length L of the electrodes 110 and 112. w The length may be any suitable length, such as a length that is about 2 to about 100 times, or about 4 to 20 times the length of the nucleic acid.

[0030] In one embodiment, as illustrated in FIGS. 1 and 2, the passageway 106C of the ejector conduit 106 has a first width at the first end 106A, the first width being smaller than the inner width d of the ejector nozzle 108 to allow the passageway 106C to fit closely around the printing material within the ejector nozzle 108 while allowing the printing material to be easily threaded into the first end 106A. i In one embodiment, the passageway 106C gradually tapers from the first width to the inner width to prevent printing material 104 in the form of a solid filament from getting caught in and / or undesirably blocking the passageway 106C.

[0031] The feeder mechanism 102 can be any suitable mechanical, pressure-driven, or other system capable of delivering the printing material 104 to the ejector conduit 106. The feeder mechanism can include one or more pumps, actuators, or combinations thereof, which can function as a mover 102a (FIG. 18) to move the printing material 104. Examples of suitable actuators include electric motors, piezoelectric motors, inchworm actuators, hydraulic actuators, and pneumatic actuators. The type of feeder mechanism 102 used will depend on the type of printing material 104 used. In one embodiment, the printing material 104 includes multiple filaments, and the feeder mechanism 102 is a mechanism for advancing the multiple filaments. For purposes of this disclosure, the term “filament” is defined to include both solid, wire-like filaments or liquid filaments, such as liquid-filled capillaries or other liquid-filled conduits. Examples of feeder mechanisms for solid filaments include spool feeders and inchworm actuators, which are well known in the art. As will be appreciated by those skilled in the art, other feeder devices for ratcheting or otherwise advancing solid printing material 104 into ejector conduit 106 in the form of a solid filament, dry powder, or other solid form may also be used as feeder mechanism 102.

[0032] In embodiments, the feeder mechanism 102 may be any suitable mechanism for supplying liquid printing material, such as a liquid filament, into the ejector conduit 106 and advancing the liquid printing material to the ejector nozzle 108. Examples of suitable feeder mechanisms for liquid printing material include mechanisms that advance liquid from a reservoir or other source of printing material (e.g., molten metal), thereby using capillary force and / or overpressure sufficient to steadily refill the ejector nozzle 108 after ejection (e.g., the feeder mechanism may be designed to automatically refill the ejector nozzle after ejection). The feeder mechanism 102 may include, for example, a pump, a feeder conduit, and / or a printing material reservoir configuration that can be filled with printing material to provide a hydrostatic head (e.g., by maintaining a certain fill level of printing material in the reservoir), or any other device for applying pressure. Such feeder mechanisms are well known in the art. Those skilled in the art will be able to readily determine an appropriate feeder mechanism.

[0033] In one embodiment, the feeder mechanism 102 can supply printing material to each ejector conduit 106 at a different feed rate. As an example, a feeder mechanism 102 for advancing multiple filaments includes separate mechanisms for incrementally advancing each of the multiple filaments at separately controllable feed rates. Thus, in one embodiment, as the ejection rate at each ejector increases or decreases as desired for printing, the feed rate can accommodate a replenishment of printing material 104 to the ejector nozzle before the next ejection.

[0034] At least a portion of each of the multiple ejector conduits 106 includes an electrically insulating material that provides suitable electrical insulation to avoid electrical shorting of the electrodes 110, 112 during operation. The electrically insulating material may be selected to withstand process temperatures while maintaining desired structural integrity. In one embodiment, the entire ejector conduit 106, except for the electrodes 110 and 112, may be an electrically insulating material, for example, as shown in FIG. 1 . In one embodiment, the conduit 106 may include a conductive material covered with an insulating material. The electrically insulating material used in the conduit 106 may be a refractory material, such as a refractory material selected from metal oxides (e.g., glasses such as doped or undoped silica), ceramics, and combinations thereof. For purposes of this disclosure, the term "refractory material" is broadly defined as any material that has a melting point of 1000° C. or greater at 1 atmosphere. For example, the refractory material can have a melting point in the range of 1000°C to about 4000°C, such as about 1200°C to about 4000°C, or about 1400°C to about 3500°C, or about 1700°C to about 3500°C, or about 2000°C to about 3500°C. The ejector conduit material can have a melting point outside these ranges. For example, if the printing material 104 is a polymer, the ejector conduit could be made of a material with a melting point below 1000°C, such as 800°C, 700°C, 500°C, or lower.

[0035] In one embodiment, the ejector conduits 106 include a combination of electrically insulating and other materials, such as when at least a portion of each of the multiple ejector conduits 106 includes a thermally conductive material such as a metal. The thermally conductive material can be used to transfer thermal energy from a heating mechanism 126 ( FIGS. 2 and 9 ) to the printing material 104 to raise and maintain the temperature of the printing material 104 as needed. The heating mechanism 126 is described in more detail below. FIG. 10 illustrates an example of one such embodiment in which the ejector conduits 106 include an electrically insulated inner conduit portion 115 and an outer conduit portion 116 including a thermally conductive material different from the electrically insulating material of the inner conduit portion. FIG. 11 includes yet another exemplary configuration in which the ejector conduits 106 arranged in an array each include an electrically insulated inner conduit portion 115. A first outer conduit portion 116 is positioned to surround an upper region of the inner conduit portion 115. The first outer conduit portion 116 comprises a thermally conductive material. The second outer conduit portion 117 is disposed to surround a lower region of the inner conduit portion 115. The second outer conduit portion 117 comprises a second electrically insulating material, which may be the same as or different from the electrically insulating material of the inner conduit portion 115. Although the second outer conduit portion 117 appears to be approximately the same thickness as the first outer conduit portion 116 in FIG. 11 , the second outer conduit portion 117 can be thinner than the first outer conduit portion 116, as long as sufficient electrical insulation is provided between the electrodes 110 and 112 and any electrically conductive material used in the conduit 106, such as when the first outer conduit portion 116 is electrically conductive. In yet another embodiment, the inner conduit portion 115 is thick enough to provide electrical insulation for the electrodes 110 and 112 (e.g., the inner conduit portion 115 is thicker than the width of the electrodes 110 and 112), in which case the first outer conduit portion 116 can extend the entire length of the ejector conduit 106. Various other designs for the ejector conduit 106 can be implemented. The electrically insulating material of the inner conduit portion 115 ( FIGS. 10 and 11 ) and the second outer conduit portion 117 can include, for example, any of the electrically insulating materials described herein for use as the ejector conduit 106.The outer conduit portion 116 of Figures 10 and 11 can comprise any thermally conductive material that provides effective thermal conductivity for transferring heat to the printing material 104 and can withstand process temperatures while maintaining structural integrity. Examples of thermally conductive materials include graphite, refractory metals, or other metals with suitable high thermal conductance and melting points for printing applications, such as copper, copper alloys, platinum, and platinum alloys, as well as combinations thereof. As used herein, the term "refractory metal" is defined to include elemental refractory metals and their alloys, including, for example, niobium, molybdenum, tantalum, tungsten, rhenium, titanium, vanadium, chromium, zirconium, hafnium, ruthenium, rhodium, osmium, iridium, and alloys of any of these metals, such as alloys of two or more of any of the refractory metals listed herein, or alloys of one or more of the refractory metals with other metals, such as iron, nickel, copper, silver, etc. Suitable refractory metal alloys are known in the art.

[0036] 12A illustrates a configuration of an ejector conduit 106 that may be used in any of the printer ejection mechanisms 100 described herein, according to one embodiment of the present disclosure. The ejector conduit 106 of FIG. 12A includes a first electrode 110 and a second electrode 112 disposed proximate to the top of an ejector nozzle 108. A current pulse generating system can pass pulses of current primarily between the first electrode 110 and the second electrode 112 when the printing material 104 is disposed within the ejector nozzle, thereby ohmically heating and expanding the printing material 104a between the first electrode 110 and the second electrode 112. This provides the desired expansion and ejection of the printing material 104 from the ejector nozzle 108. In one example, the printing material 104a between the electrodes 110 and 112 vaporizes to provide the desired expansion, thereby driving the ejection of the printing material 104b, which remains in liquid form below the electrodes 110, 112, from the ejector nozzle 108, as illustrated in FIG. w L can be any desired length that allows for sufficient ohmic heating for ejection or printing material 104.w Examples of suitable values ​​of are about 5 micrometers to about 1000 micrometers, such as about 5 micrometers to about 500 micrometers, such as about 10 micrometers to about 100 micrometers, or about 15 micrometers to about 50 micrometers.

[0037] In the embodiments described herein, the electrodes 110, 112 may be disposed entirely within the ejector nozzle 108 (e.g., FIG. 12A) and / or may be disposed at the tip (e.g., end-most position) of the ejector nozzle 108 (e.g., FIG. 1). The ejector nozzle 108 is the end-most portion of the ejector conduit 106 and may have an inner width d of the ejector nozzle 108 as described herein, for example. i (e.g., diameter) in the range of about 1 to about 10 times n (FIG. 12A). In another embodiment, the ejector nozzle 108 has a length L n For example, d i Approximately 1 to 5 times, d i Approximately 1 to 3 times, d i Approximately 1 to 2 times or d i In one embodiment, the electrode length L w is the length of the ejector nozzle L n is equal to.

[0038] Referring to FIG. 2 , multiple ejector conduits 106 are supported within an ejector housing 120. The ejector conduits 106 may be separate structures from the housing material and may be attached to the ejector housing 120 in any suitable manner. In alternative embodiments, the multiple ejector conduits may be integral with the ejector housing 120. For example, the conduits may be formed as capillary tubes or larger conduits that are drilled or otherwise formed directly in the housing material. The conduits may optionally be coated to provide an inner surface of the ejector conduits 106 comprising a material that is different from, but integral with, the ejector housing 120. Techniques for forming such conduits directly in the housing material, as well as techniques for coating the conduits, are generally known. In embodiments, the ejector conduits 106 may comprise a different material than, or the same material as, the ejector housing 120.

[0039] The ejector housing 120 comprises any suitable material capable of withstanding the ejection process temperatures and providing the desired support for the ejector conduit 106. Examples of suitable housing materials include metals such as aluminum, copper, brass, and steel, refractory metals, ceramics, other refractory materials, polymers capable of withstanding the process temperatures (e.g., polymers having melting points of 150°C to 650°C or higher, such as 200°C to 300°C), and combinations thereof, such as metal-coated ceramics and ceramic-coated metals. An example of a composite housing material is copper clad with a ceramic, such as mullite, where the copper and mullite have similar thermal expansion coefficients. The specific material used will depend on the printing material being ejected.

[0040] In one embodiment, the ejector housing 120 includes a heating mechanism 126 for heating at least a portion of the ejector housing 120 surrounding the ejector conduit 106 during operation of the three-dimensional printer. The heating mechanism 126 can provide sufficient thermal energy to bring the printing material 104 to or just below a desired temperature for expansion and ejection of the printing material. For example, if the expansion to provide the ejection momentum of the printing material does not involve a phase change, the heating mechanism 126 can provide sufficient thermal energy to bring the printing material 104 to a melting temperature or just above the melting temperature. Alternatively, in the case of a phase-change expansion, to provide the printing material momentum for ejection, the heating mechanism 126 can provide sufficient thermal energy to bring the printing material 104 to a temperature just below the melting temperature or vaporization temperature of the printing material 104, as desired. In embodiments in which a phase change of the printing material occurs, by controlling the printing material temperature near the ejection site (e.g., the melting zone or vaporization zone), heat loss away from the ejector nozzle 108 can be reduced because the phase change is an isothermal process. In embodiments where the printing material 104 is solid before the phase change, a temperature below the melting temperature may be desirable to ensure re-solidification of un-jetted material before the next jetting event.

[0041] The heating mechanism 126 may include, for example, any suitable type of resistive heater, inductive heater, radiative heater, or any combination thereof. For example, the heating mechanism 126 may comprise a heating element embedded in or disposed proximate to the conduit 106 and / or the ejector housing 120, as illustrated in FIGS. 1 and 9 . The heating element may be in the form of, for example, a resistive heating coil or an inductive coil. As an example, a suitable resistive heating mechanism comprises an ohmic serpentine trace embedded in the ejector housing 120 or the ejector conduit 106 surrounding the passage 106C. As used herein, the term “ohmic serpentine trace” refers to a conductive heating element having a nonlinear path along its longitudinal axis (e.g., a wire suitable for resistive heating having a zigzag, wound, or otherwise curved path). The heating mechanism 126 is separate from the current pulse generation system 114 and / or the electrodes 110, 112.

[0042] In one embodiment, the array of ejector conduits 106 includes M columns of ejector conduits arranged on the X-axis and N rows of ejector conduits arranged on the Y-axis, where M is an integer ranging from 2 to 1000 and N is an integer ranging from 1 to 2. For example, for the array of Figure 2, M is 3 and N is 1, while for the array of Figure 9, M is 3 and N is 2. In other examples, M is an integer ranging from 5 to about 1000, from about 50 to about 1000, from about 100 to about 500, or from about 500 to about 1000.

[0043] In one embodiment, the rows of the ejector conduits 106 are arranged linearly, with the ejector conduits 106 in each row staggered relative to the ejector conduits in adjacent rows to facilitate close packing, as shown, for example, in Figure 9. In an alternative embodiment (not shown), the columns of the ejector conduits 106 are arranged linearly, with the ejector conduits 106 in each column staggered relative to the ejector conduits in adjacent columns. Multiple arrays can be stacked to expand the number of rows or columns in a system, as needed.

[0044] Droplet formation during ejection of printing material can occur by any suitable mechanism within or external to the ejector nozzle 108. In one embodiment, detachment of printing material to form droplets can occur by necking-off of the printing material inside the ejector conduit 106, such as within the nozzle 108. In such an embodiment, the ejector conduit 106 can optionally include one or more vents 130, as illustrated in FIG. 13 . The vents 130 can be located within or immediately above the ejector nozzle 108, such as at or near a position within the ejector nozzle 108, where necking-off of the ejected printing material 104 from the remaining printing material 104 in the ejector conduit 106 occurs during droplet formation. The vents 130 allow air or other ambient gases (as illustrated by arrows 132) to flow into the ejector conduit 106 and / or into the ejector nozzle 108 as the printing material 104 is ejected. This may allow the printing material 104 to be ejected and more easily separated from the remaining printing material 104 in the ejector conduit 106 and / or more easily ejected from the ejector nozzle 108. The one or more vents 130 may be configured in any manner that allows ambient gas to flow into the ejector nozzle as the printing material 104 is ejected. FIGS. 14A and 14B illustrate another example in which the vent 130 takes the form of a groove on the inner surface of the ejector nozzle 108. Any other suitable vent configuration may be used. In one embodiment, the vent 130, such as that in FIGS. 13, 14A, and 14B, has dimensions that are small enough so that the surface tension of the liquid printing material 104 does not allow a large amount of printing material to flow out of the ejector conduit into the vent 130, but large enough to allow ambient gas to flow through the groove and into the ejector nozzle 108. For example, the width and / or length of vent 130 in Figure 13, or the diameter in the case of a circular vent (not shown), or the groove width in Figure 14, can be 10 times or more smaller than the inner diameter of the ejector nozzle so that penetration of the liquid printing material is reduced or eliminated. The vents can be formed by any suitable means, such as by etching techniques or laser ablation, as are well known in the art.

[0045] This disclosure is not intended to be limited to any particular droplet formation and / or detachment mode. For example, droplets can neck off and detach in a detachment zone inside the ejector conduit 106, but it is also possible for droplets to neck off and detach outside the ejector conduit 106, with the undetached printing material 104 then retreating back into the ejector conduit 106. Thus, modes of droplet ejection can include expansion "extrusion" of the molten printing material 104 from the ejector nozzle 108 into free space, followed by deceleration / retreat of the extruded printing material 104 as the heating pulse ends and the printing material 104 cools / contracts. Other modes of droplet ejection and / or detachment can also be implemented.

[0046] In one embodiment, ejecting the printing material includes flowing a sheath gas proximate the ejector nozzle, where the sheath gas includes one or both of an inert gas and a reducing gas. An example using a sheath gas is illustrated by arrow 210 in FIG. 16 . The sheath gas flow can be achieved in any suitable manner, such as by flowing the sheath gas through a sheath gas vent 212 located in or near the printer ejection mechanism 100, such as in the array 107 and / or ejector housing 120 of any of the printer ejection mechanisms described herein. In one embodiment, the sheath gas is maintained at a desired temperature to avoid cooling the printing material before deposition. For example, the sheath gas temperature can be at or above the melting point of the printing material. In this way, the printing material can be maintained in a molten state, if desired, until deposition onto the substrate occurs. In one embodiment, the sheath gas can move at approximately the same speed and in approximately the same direction as the droplets as they are ejected.

[0047] The printer-jetting mechanism 100 described herein can be used in any type of printer suitable for jetting printing material. In one embodiment, the printer is a three-dimensional (“3D”) printer usable for printing 3D objects. A block diagram of an exemplary 3D printer 150 is shown in FIG. 15 . The 3D printer 150 can include any of the printer-jetting mechanisms 100 described herein, including an array 107 of ejector conduits 106. Additionally, the 3D printer can include a positioning system 152 for controlling the relative position of the array 107 with respect to a printed circuit board 154. The phrase “controlling the relative position of the array 107 with respect to the printed circuit board 154” means that one or both of the array 107 and the printed circuit board 154 can move to change the relative positions of the array and the printed circuit board. The relative position of the printed circuit board 154 and the array 107 is modified during printing such that the printed circuit board 154 is positioned to receive jettable printing material 104 from the multiple ejector conduits, thereby forming the 3D object. The positioning system 152 can include one or both of a printed circuit board handling mechanism 156 for positioning the printed circuit board 154 and an array positioning mechanism 158 for positioning other parts of the printer jetting mechanism 100, such as the array 107 and, optionally, a portion of the current pulse generating system 114, or the electrical connections thereto. The printed circuit board 154 can include any substrate on which it is desired to print a three-dimensional object. An example of a printed circuit board 154 is a build plate that is part of the 3D printer 150, or other temporary substrate from which the 3D object can be detached after printing. In another example, the printed circuit board 154 can be intended to be permanently attached to the three-dimensional object after printing, such as when the printed circuit board 154 is a printed circuit board on which a portion of a circuit has been printed.

[0048] The printed circuit board handling mechanism 156 may be any mechanism suitable for positioning the printed circuit board 154 to receive jettable printing material from multiple ejector conduits disposed within the array 107 during operation of the 3D printer 150. In one embodiment, the printed circuit board handling mechanism 156 is capable of positioning the printed circuit board 154, such as a mechanism plate or other substrate, by moving the printed circuit board 154 along the x-axis, y-axis, and / or z-axis to a desired location targeted by the jetted printing material. The array positioning mechanism 158 may be any mechanism suitable for moving the array 107 along one or more of the x-axis, y-axis, and / or z-axis to a desired location targeted by the jetted printing material 104. The positioning system 152, including either or both the printed circuit board handling mechanism 156 and the array positioning mechanism 158, may include one or more actuators 180 ( FIG. 18 ), which may function as movers for positioning the printed circuit board 154 and the array 107 relative to one another, for example, using a system including tracks 182. Examples of suitable actuators include electric motors, piezoelectric motors, hydraulic actuators, and pneumatic actuators. FIG. 18 illustrates an example of such a positioning system 152 comprising an actuated (e.g., motorized) XY stage 184 for supporting a printed circuit board 154 and a vertical track system 186 along which all or a portion 100 a of the printer ejection mechanism 100 can be moved using one or more actuators 180 to enable vertical positioning. The portion 100 a of the printer ejection mechanism 100 can comprise any of the components of the printer ejection mechanism 100 described herein mounted on the vertical track system 186 for vertical positioning, including multiple ejector conduits disposed within an array and all or a portion of the current pulse generation system. The feeder mechanism 102 can be positioned so that it is not directly mounted to the vertical track system 186 (as illustrated in FIG. 18 ), or in other embodiments, it can be directly mounted to the vertical track system 186.

[0049] As mentioned, the positioning system 152 can include one or both of a printed circuit board handling mechanism 156 and an array positioning mechanism 158. By way of example, the printed circuit board handling mechanism 156 can be used to move the printed circuit board 154 along both the x-axis and the y-axis, and the array positioning mechanism 158 can be used to move the array 107, and optionally the entire printer jetting mechanism 100, or any portion thereof, along the z-axis, thereby allowing the printed circuit board 154 and the array 107 to be positioned relative to one another in three dimensions during operation of the 3D printer. By way of example, for purposes of this discussion, the x-axis and z-axis are as illustrated for the printing operation in FIG. 16 , the y-axis (not shown) is in the direction into the paper, the x-axis and y-axis are parallel to the top surface of the printed circuit board 154, and the z-axis is perpendicular to the top surface of the printed circuit board 154. In one embodiment, the printed circuit board 154 is a build plate, optionally using a heating mechanism 155 that can heat the build plate to a desired deposition temperature. Suitable build plates, including build plates with heating mechanisms, are well known in the art.

[0050] Method for jetting printing material An embodiment of the present disclosure is directed to a method for ejecting printing material from a printer ejection mechanism. As illustrated in FIG. 17 at 200, the method includes supplying a printing material 104 that is electrically conductive to a plurality of ejector conduits 106 (FIGS. 1 and 2) arranged in an array. The ejector conduits 106 have a first end 106A configured to receive the printing material and a second end 106B that includes an ejector nozzle 108. The ejector nozzle 108 can have an internal width (e.g., diameter) ranging from about 10 micrometers to about 1000 micrometers, for example, or any of the widths of other ejector nozzles disclosed herein. In the method described herein, the ejector nozzle 108 includes electrodes 110, 112 for supplying an electric current to induce thermal expansion and ejection of the printing material, as discussed in more detail below.

[0051] As shown at 202 in FIG. 17 , the printing material 104 is advanced into one or more of the ejector conduits 106 of the array until the printing material 104 is disposed within the ejector nozzles 108 of the one or more ejector conduits 106. As an example, the printing material 104 can be advanced to substantially or completely fill the ejector nozzles 108. In one embodiment, the printing material 104 includes multiple filaments. Individual filaments of the multiple filaments can be advanced into each of the one or more ejector conduits 106 to supply the printing material at a desired feed rate. The desired feed rate can be different for each filament depending on the rate at which the printing material is being ejected from the associated ejector nozzle 108, which in turn depends on the number of jets per unit time from each nozzle and the droplet size per jet.

[0052] 17 , the printing material 104 disposed in at least one of the ejector nozzles 108 is heated by passing an electric current through the conductive printing material 104 disposed in at least one of the ejector nozzles 108, thereby heating and expanding the printing material for a selected time period to provide sufficient momentum to eject at least a portion of the printing material from at least one of the ejector nozzles 108, for example, onto a printed circuit board. Passing an electric current may include, for example, sending a current pulse between the first electrode 110 and the second electrode 112 using a current pulse generating system 114, such as any of the current pulse generating systems described herein.

[0053] In one embodiment, the current pulse causes the printing material 104 to undergo a phase transition from a first phase to a second phase to achieve the desired expansion. In one example of phase-change expansion, a filament in a solid phase is supplied to the ejector nozzle 108 as the printing material 104. Heating the printing material 104 disposed within the ejector nozzle 108 uses a single current pulse to melt individual filaments to provide the desired momentum of the printing material for ejection. In an embodiment in which the printing material 104 is solid and then changes phase to a liquid, controlling the temperature of the printing material remaining in the ejector conduit 106 to be directly below the melting temperature after each ejection may be desirable to ensure re-solidification of any un-ejected liquid material before the next ejection event.

[0054] In another example of phase change expansion, the printing material 104 is supplied to the ejector nozzle 108 as a liquid phase. Heating the printing material 104 disposed within the ejector nozzle 108 vaporizes at least a portion of the liquid printing material 104 using a single current pulse to provide the desired momentum of the printing material for ejection.

[0055] Even without undergoing a phase change, some printing materials can expand sufficiently in the liquid phase as their temperature increases to drive ejection. In one embodiment, the printing material 104 is supplied to the ejector nozzle as a liquid and thermally expanded while remaining in liquid form throughout the entire heating period to eject the liquid from the ejector nozzle 108. In one embodiment, the liquid printing material 104 is expanded sufficiently rapidly using a single current pulse to provide the desired momentum of the printing material for ejection without undergoing a phase change.

[0056] The ejection force, or momentum, of the printing material ejected from the ejector nozzle 108 depends on both the amount of thermal expansion and the rate of expansion of the printing material, which in turn depends on both the amount of thermal energy applied to the printing material and the time it takes to apply the thermal energy to the printing material. Therefore, to impart a desired momentum to the printing material, droplets of the printing material can be ejected from the ejector conduit 106 and deposited on a substrate using relatively short pulses of sufficiently high current to achieve the desired amount of expansion. The pulse length of the current can be any duration that provides the desired expansion rate and ejects the printing material 104. Examples of suitable pulse lengths range from about 0.1 microseconds to about 100 milliseconds, from about 1 microsecond to about 1000 microseconds, or from about 2 microseconds to about 100 microseconds. This rapid heating causes the printing material to expand axially within the ejector nozzle 108, thereby providing sufficient momentum to the printing material 104 to eject at least a portion of it from the ejector nozzle 108. The amount of current and length of the current pulse to achieve a desired momentum of the ejected printing material depends on the type of printing material, the amount of printing material to be ejected, etc., and can be easily determined by one skilled in the art. In addition to providing momentum for the ejection, a shorter current pulse length can also potentially enable a faster ejection rate (e.g., more ejections of printing material per second from the same ejector nozzle).

[0057] While the above teaches using a single current pulse to achieve expansion of the printing material 104, it may also be useful to use two or more current pulses to achieve expansion, either from the same or multiple pairs of electrodes. For example, two, three, or more rapid pulses may be used to achieve the desired expansion of the printing material, as opposed to a single, longer pulse. In general, any desired pulse waveform capable of providing the desired ejection of the printing material may optionally be selected.

[0058] Droplet sizes can be individually selected on demand. In one embodiment, droplet size can be varied by varying the current pulse energy of each pulse (e.g., varying the pulse length and / or amplitude of the current pulse). In another embodiment, multiple addressable electrodes (similar to those shown in FIG. 5 , but with each electrode independently driven) can be used to vary droplet volume. Thus, during operation, a current generating system can be used to send electrical pulses between a first number of electrode pairs (e.g., one or more of electrode pairs 110a, 112a, 110b, 112b, and 110c, 112c in FIG. 5 ) to achieve a first jet, followed by sending electrical pulses between a second number of electrode pairs to achieve a second jet, where the first number of electrode pairs is different from the second number of electrode pairs. In this process, the droplet size of the printing material ejected during the first jet is different from the droplet size of the printing material ejected during the second jet.

[0059] The droplet size per jet may be selected based on a variety of factors, including the desired size of the printed object detail, the specific properties of the printing material (e.g., heat transfer and expansion properties), the characteristics of the current pulse provided to the printing material, the nozzle size, etc. The droplets may generally have a diameter size as small as the inner diameter of the jetting nozzle 108, but may have significantly larger diameters if a longer length of filament is heated during a single jet. A trade-off between power and droplet size may be considered when determining the amount of printing material heated for each jet. In particular, a longer length of filament can be heated with proportionally higher power, allowing for a longer length of printing material to be jetted. In one embodiment, the length of heated printing material per pulse is about 1 to about 10 times the inner width (e.g., diameter) of the printing nozzle 108 each time the printing material is jetted (this inner width may be approximately the same as the filament width, dp, if a solid filament is fed directly into the printing nozzle). Thus, as an example, the filament can be advanced from a length of about one diameter of the printing nozzle per pulse of current to a length of about 10 diameters per pulse, the pulse of current causing ohmic heating and expansion of each length of the filament as it advances.

[0060] After ejection of the printing material 104, the heating and associated expansion of the printing material can be repeated to advance additional printing material 104 into the ejector nozzle or nozzles 108 and then eject additional printing material. This process of advancing and heating the printing material can be repeated any number of times desired for each of the ejector nozzles 108 in the array until printing is completed, thereby forming the 3D object. During printing, the heating and ejection of the printing material 104 can occur from a single ejector nozzle 108 in the array, simultaneously from two or more ejector nozzles 108, and / or simultaneously from all of the ejector nozzles 108 in the array, as desired to accomplish the particular printing process being performed.

[0061] Any conductive printing material that expands sufficiently during a phase change and / or during heating in a single phase (e.g., without a phase change) to generate sufficient momentum for ejection can be used. In one example, the printing material includes at least one metal. The at least one metal can be selected from, for example, tin, tin alloys, lead, lead alloys (e.g., solders containing one or both of tin and lead), aluminum, aluminum alloys (e.g., 1000 series, 2000 series, 3000 series, 4000 series, 5000 series, 6000 series such as 6061 and 6063, and 7000 series aluminum alloys), magnesium, magnesium alloys, iron, iron alloys (e.g., steel), copper, copper alloys (e.g., zinc), nickel, nickel alloys, titanium, titanium alloys, tungsten, tungsten alloys, silver, and silver alloys. Suitable alloys of the above metals can include any desired mixture of metals, such as a mixture of two or more of any of the above elemental metal printing materials (e.g., a mixture of two or more of aluminum, magnesium, iron, copper, nickel, titanium, tungsten, silver, etc.). In one embodiment, the printing material 104 has a metal content of greater than 90% by weight, such as between about 95% and 100% by weight, or between 98% and 100% by weight, or between 99% and 100% by weight, or between 99.5% and 100% by weight, or between 9.8% and 100% by weight, or between 99.9% and 100% by weight.

[0062] In one embodiment, the printing material 104 has a conductivity of about 1×10 at 20° C. (e.g., is conductive at room temperature (20° C.)). -6 Ohms * m or approx. x 1x10 -7 Ohms * m ~ approx. x 1x10 -8 Ohms * m, etc., 1x10 at 20°C -5 Ohms * In one embodiment, the printing material 104 has a resistivity of less than about 1×10 -6 Ohms * m ~ approx. 1x10 -8 Ohms * 1x10 such as m -5 Ohms *m, while in solid, liquid, or both solid and liquid form, while at a temperature within 300° C. of the melting temperature.

[0063] Any of the printing materials described herein can be in the form of multiple solid or liquid filaments. The solid filaments can have any desired cross-sectional shape, such as circular, elliptical, rectangular, or other polygonal. The cross-sectional shape of the solid filaments can be the same as that of the ejector nozzle 108 (e.g., small in size to allow feeding of the filament through the nozzle). For solid filaments having a circular cross-section, such as shown for printing material 104 in FIG. 8, the filaments have a width d, which is the diameter of the circular cross-section. p For solid filaments that do not have a circular cross section, the width d p is a dimension corresponding to (e.g., collinear with) the inner width di of the ejector nozzle 108 when a solid filament is delivered to the ejector nozzle 108. p If there are more than two possible values ​​for d, then p is possible d p It is the maximum value.

[0064] For solid filaments, the width of an individual filament, d p is the inner width of the ejector nozzle 108, d i The solid filament width, d, may optionally be selected to be slightly smaller than or substantially the same as the solid filament width, d, and the filament is positioned to provide a close fit around the solid filament, thereby allowing the filament to still be positioned within the ejector nozzle 108. The fit is close enough so that when the portion of the filament within the ejector nozzle expands, the printed material expands axially at a sufficient velocity to eject at least a portion of the filament material from the ejector nozzle 108. As an example, the solid filament width, d p is about 0.1% to about 1% smaller, or about 0.5% smaller, etc., the ejector nozzle inner width, d i 0 to about 2% smaller than d p and di The relative sizes of the filament widths can depend on various factors, such as the expansion characteristics of the printing material during phase change, the desired momentum of the printing material when ejected, the heating rate of the printing material within the ejector nozzle, and others. As an additional example, the filament width (e.g., diameter) can be about 0.01 micrometers to 20 micrometers smaller than the nozzle inner width (e.g., diameter), such as about 0.1 micrometers to about 10 micrometers, or about 1 micrometer to about 5 micrometers, or about 0.1 micrometers to about 2 micrometers, or about 0.1 micrometers to about 1 micrometer smaller than the nozzle inner width (e.g., diameter).

[0065] The printing material can have any suitable width, such as a width (e.g., diameter) ranging from about 1 micrometer to about 1000 micrometers, about 10 micrometers to about 500 micrometers, about 50 micrometers to about 200 micrometers, or about 100 micrometers. The advantage of ohmic heating is that heat is generated throughout the entire portion of the filament through which current flows, so the propagation time of thermal energy from the periphery to the center of the filament is not a factor. The ability to heat and expand the entire thickness of the filament in short bursts, regardless of filament thickness, can enable, among other things, increased control over jet momentum and / or jet volume (e.g., droplet size). That is, a filament with a relatively small width (e.g., diameter) may be able to individually jet a smaller amount of printing material (e.g., smaller droplet sizes jetted from the jet nozzle 108) compared to a filament with a larger width. Therefore, for these reasons, filaments with relatively small widths may be preferred. The desired small filament width size will depend on the thermal diffusivity characteristics of the printing material, as well as other factors. By way of example, the width (e.g., diameter) of the printed material for solid or liquid filaments ranges from about 1 micrometer to about 100 micrometers, such as from about 10 micrometers to about 50 micrometers, or from about 10 micrometers to about 25 micrometers. The inner width of the ejector nozzle can be sized as described above to provide a close fit around an individual filament while still allowing the filament to be positioned within the ejector nozzle.

[0066] In embodiments, printing material 104 is supplied to the ejector conduit as either a liquid or a solid and ejected from the ejector nozzle 108 as a liquid in the form of droplets. The droplets may optionally have a relatively small droplet size, which may enable printing of fine detail. By way of example, droplet diameters may range from about 0.001 mm to about 0.2 mm, from about 0.005 mm to about 0.1 mm, or from about 0.01 mm to about 0.05 mm. Droplets of larger diameters may also be formed if desired.

[0067] In one embodiment, the printing material 104 is supplied to the ejector nozzle 108 as a liquid first phase, and then a portion of the printing material is heated to a vapor second phase. Referring to FIGS. 12A and 12B , in such a process, at least a portion of the passage 106C in front of the ejector nozzle 108 is filled with molten printing material (e.g., any of the printing materials described herein). As described herein, all or a portion of the passage 106C can optionally be tapered. Using a current pulse transmitted between the electrodes 110 and 112, a first portion 104a of the molten printing material 104 between the electrodes 110 and 112 is vaporized by rapid heating within the ejector nozzle 108, while a second portion 104b between the first portion 104a and the tip of the ejector nozzle 108 remains liquid. The vaporized portion 104a of the printing material 104 expands axially to provide sufficient motive force to eject a liquid second portion 104b of the printing material from the ejector nozzle 108. In one embodiment, the printing material 104 may be initially fed as a solid to the first end 106A of the ejector conduit 106 using the feeder mechanism 102, melted before being introduced to the ejector nozzle 108, such as by using heat from the heating mechanism 126, and then vaporized by rapid heating within the ejector nozzle 108 to provide the desired motive force for jetting. Alternatively, the printing material 104 may be fed as a liquid to the first end 106A of the ejector conduit 106 using the feeder mechanism 102, maintained as a liquid using heat from the heating mechanism 126, and then vaporized by rapid heating caused by a current pulse between the electrodes 110, 112 to provide the desired motive force for jetting.

[0068] The methods of the present disclosure can be used to deposit printing material 104 simultaneously or separately from any number of ejector conduits 106, as desired, and can allow for the deposition of small amounts of material from any one ejector nozzle 108 while still providing a relatively high overall deposition rate, due to the potentially large number of ejector conduits 106 in the array and the potentially high ejection velocity from each ejector conduit 106.

[0069] The printer jetting mechanisms for jet-printed materials described herein can be used in various printing methods. For example, any of the printer jetting mechanisms described herein can be used in a method of three-dimensional printing in which printing material 104 ( FIG. 1 ) is ejected from ejector nozzles 108 and deposited onto a printed circuit board 154 ( FIGS. 15 and 16 ), such as a build plate. One or both of the printed circuit board 154 and the array 107 of ejector nozzles 108 can move relative to one another in three dimensions (e.g., along the x-, y-, and z-axes) during printing in any manner as described herein, thereby forming a 3D object. As is well known in the art, 3D printing involves printing multiple droplets or layers of material, each of which can be stacked on top of each other until a desired thickness of the 3D object is achieved. FIG. 16 illustrates an example of a printer jetting mechanism 100 including multiple ejector conduits 106 that simultaneously eject droplets 200 to print a 3D object 202 on the printed circuit board 154. Many layers 204 of droplets 200 can be deposited, one layer or droplet after the other, until the 3D object 202 is complete. As will be readily understood by one skilled in the art, the droplets and / or layers can be stacked in any desired order, for example, a first sub-layer 204 may or may not be completed before beginning a subsequent layer, and there may or may not be a discernible layer pattern relative to the order of material deposition. Rather, the droplets, layers, and / or portions of layers can be stacked in any desired order to complete the 3D object.

[0070] The following examples are illustrative only and are not intended to limit or otherwise affect the scope of the invention as set forth in the claims.

[0071] Theoretical Example Example 1: Solid-to-Liquid Phase Change Expansion: Aluminum, copper, and iron wires each having a diameter of 0.0001 meters are held just below their melting temperature and each is fed into a separate refractory tube (e.g., a fused silica tube) with an inner diameter larger than the outer diameter of the wire. A current pulse flows through the 0.0001 meter end portion of each wire, melting the wire portion in microseconds. During melting, expansion of the molten wire material occurs primarily along the longitudinal axis of the silica tube. The free meniscus of the molten material accelerates axially within the tube, with the molten region accelerating at approximately half the speed of the meniscus. As shown in Table 1 below, the acceleration of the molten material within the tube corresponds to an energy sufficiently greater than the energy required to detach a droplet of molten material from the wire and eject it from the tube, thus ejecting the droplet from the tube. The energy used to melt a sufficient portion of the wire for ejection is provided by a current pulse generating system, such as any of the current pulse generating systems described herein, that can be pulsed at the desired pulse power.

[0072] The calculations in Table 1 below assume there is no volume between the wire and the tube. Calculated motive force = average acceleration of the melt multiplied by the mass of the melt. "Pulse energy" in the table refers to the energy to melt the length of wire that can potentially be delivered by a single current pulse.

[0073] [Table 1]

[0074] Example 2: Liquid-to-Liquid Expansion: Each of aluminum, copper, iron, and indium wires, each with a diameter of 0.0001 meters, is fed into a separate refractory tube (e.g., fused silica) with an inner diameter larger than the outer diameter of the wire. The refractory tube includes two electrodes disposed at its ends. The electrodes are connected to a current pulse generating system and positioned within the tube so that a current flows through the wire material adjacent the end of the tube. A liquid metal, such as molten aluminum, mercury (Hg), gallium-indium, or a gallium-indium-tin eutectic mixture, is fed into a similar silica tube equipped with electrodes. In the case of wire materials, a meniscus of the liquid is positioned at the end of the graphite tube to melt at least a portion of each wire and maintain it as a liquid adjacent the end of the silica tube. Using the current pulse generating system, a single current pulse flows through the 0.0001 meter end portion of each silica tube, heating the liquid material therein to a temperature increase of approximately 300 Kelvin in approximately 5 microseconds. During heating, the expansion of the liquid material occurs primarily along the longitudinal axis of the silica tube. The free meniscus of the molten material accelerates axially within the tube, and the molten region accelerates at approximately half the speed of the meniscus. As shown in Table 2 below, the acceleration of the molten material within the tube corresponds to an energy that exceeds the energy required to detach a droplet of molten material from the liquid and eject it from the tube, thus ejecting the droplet from the tube.

[0075] For the calculations in Table 2 below, Motive Force = Average Acceleration of the Liquid Multiplied by the Mass of the Liquid. "Pulse Energy" in Table 2 refers to the energy required to raise the temperature of the liquid by 300 Kelvin and could potentially be supplied by a single current pulse.

[0076] [Table 2]

[0077] Example 3: Liquid-to-Vapor Phase Change Expansion: Aluminum, copper, and iron wires each having a diameter of 0.0001 meters are fed into separate refractory tubes (e.g., silica tubes) having an inner diameter larger than the outer diameter of the wire. At least a portion of each wire is melted and maintained as a liquid proximate the end of the silica tube, with a meniscus of liquid positioned at the end of the silica tube. The silica tube includes an electrode positioned just above the 100 micrometer silica end portion of the tube. The electrode is attached to a current pulse generating system, such as any of the current pulse generating systems described herein. The electrode has a dimension of approximately 25 micrometers along the length of the tube. A current pulse is transmitted through the liquid material between the electrodes in the silica tube, vaporizing the liquid in approximately 5 microseconds. The end portion of the molten material between the electrode and the silica tip remains liquid. During heating, the expansion of the vaporized material occurs primarily along the longitudinal axis of the silica tube, pushing against the end portions of the liquid or molten material, accelerating them axially so that they are ejected from the tube, resulting in droplets of molten material being ejected from the tube.

[0078] For Table 3 below, "Pulse Energy" refers to the energy used to vaporize a portion of the liquid as described above, and could potentially be supplied by a single current pulse.

[0079] [Table 3]

[0080] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the present disclosure are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Furthermore, all ranges disclosed herein should be understood to encompass any and all subranges subsumed therein.

[0081] While the present teachings have been illustrated with respect to one or more implementations, changes and / or modifications can be made to the illustrated embodiments without departing from the spirit and scope of the appended claims. Additionally, while particular features of the present teachings may be disclosed with respect to only one of several implementations, such features may be combined with one or more other features of other implementations as may be desirable and advantageous for any given function or functions. Furthermore, to the extent that the terms "including," "includes," "having," "has," "with," or variations thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprising." Furthermore, the term "about" in the discussion and claims herein indicates that the recited values ​​may be varied somewhat unless such variations result in incompatibility of the process or structure to the illustrated implementation. Finally, the term "exemplary" indicates that the description is used as an example, rather than as an ideal.

[0082] It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unprecedented alternatives, modifications, variations, or improvements may subsequently occur to those skilled in the art, which are intended to be encompassed by the following claims.

Claims

1. 1. A method of printing a three-dimensional object, comprising: supplying a conductive filament printing material to a plurality of ejector conduits arranged in an array, the ejector conduits comprising a first end configured to receive the printing material and a second end comprising an ejector nozzle; advancing the printing material into one or more of the ejector conduits of the array until the printing material is disposed within the ejector nozzle of one or more of the ejector conduits; passing an electric current through the filament printing material disposed in at least one of the ejector nozzles, thereby heating and expanding the filament printing material in the at least one of the ejector nozzles so as to eject at least a portion of the filament printing material from the at least one of the ejector nozzles onto a printed circuit board; repeating both the advancing and the passing of the current through the filament printing material to form a three-dimensional object on the printed circuit board; and Including, the filament printing material has a width that is about 0 to about 2% less than the inner width of the ejector nozzle in which the filament printing material is disposed; method.

2. 2. The method of claim 1, wherein the ejector nozzle comprises a first electrode and a second electrode forming an electrode pair, and further wherein the passing of the current comprises sending an electrical pulse between the first electrode and the second electrode using a current pulse generating system.

3. 2. The method of claim 1, wherein the ejector nozzle comprises a plurality of electrode pairs, and further wherein the passing of the current comprises sending electrical pulses between a first number of electrode pairs to achieve a first ejection and sending electrical pulses between a second number of electrode pairs to achieve a second ejection, the first number of electrode pairs being different from the second number of electrode pairs.

4. 2. The method of claim 1, wherein the filament printing material comprises a plurality of filaments, and further wherein the advancing the filaments comprises advancing individual filaments of the plurality of filaments into each of the one or more ejector conduits.

5. The method of claim 4 , wherein the plurality of filaments comprises a metal.

6. 10. The method of claim 1, wherein during the heating of the filament printing material disposed within at least one of the ejector nozzles, at least a portion of the filament printing material undergoes a phase transition from a first phase to a second phase.

7. 7. The method of claim 6, wherein the first phase is a solid and the second phase is a liquid.

8. 8. The method of claim 7, wherein the liquid is ejected from the ejector nozzles of the one or more ejector conduits as droplets having a droplet diameter in the range of about 0.001 mm to about 0.2 mm.

9. 7. The method of claim 6, wherein the first phase is a liquid and the second phase is a vapor, and further wherein a first portion of the filament printing material disposed within the at least one of the ejector nozzles undergoes the phase transition while a second portion of the filament printing material between the first portion and a tip of the ejector nozzle remains liquid, the second portion being the portion of the filament printing material ejected from the at least one of the ejector nozzles.

10. 10. The method of claim 1, wherein the filament printing material disposed within at least one of the ejector nozzles is maintained in a single phase during the heating.

11. 10. The method of claim 1, wherein the heating comprises simultaneously heating the filament printing material disposed within the ejector nozzles of two or more ejector conduits.

12. 10. The method of claim 1 , wherein the three-dimensional object comprises a plurality of stacked layers of filament printing material.

13. 1. A method for ejecting printing material from a printer ejection mechanism, comprising: supplying a conductive printing material to a plurality of ejector conduits arranged in an array, the ejector conduits comprising a first end configured to receive the printing material and a second end comprising an ejector nozzle; advancing the printing material into one or more of the ejector conduits of the array until the printing material is disposed within the ejector nozzle of one or more of the ejector conduits; passing an electric current through the printing material disposed in at least one of the ejector nozzles, thereby heating and expanding the printing material in the at least one of the ejector nozzles to eject at least a portion of the printing material from the at least one of the ejector nozzles; Including, the filament printing material has a width that is about 0 to about 2% less than the inner width of the ejector nozzle in which the filament printing material is disposed; method.

14. 14. The method of claim 13, wherein the ejector nozzle comprises a first electrode and a second electrode forming an electrode pair, and further wherein the passing of the current comprises sending an electrical pulse between the first electrode and the second electrode using a current pulse generating system.

15. 14. The method of claim 13, wherein the ejector nozzle comprises a plurality of electrode pairs, and further wherein the passing of the current comprises sending electrical pulses between a first number of electrode pairs to effect a first ejection and sending electrical pulses between a second number of electrode pairs to effect a second ejection, the first number of electrode pairs being different from the second number of electrode pairs.

16. 14. The method of claim 13, wherein the filament printing material comprises a plurality of filaments, and further wherein the advancing the filaments comprises advancing individual filaments of the plurality of filaments into each of the one or more ejector conduits.

17. The method of claim 13 , wherein the filament printing material comprises a metal.

18. 14. The method of claim 13, wherein during the heating of the filament printing material disposed within at least one of the ejector nozzles, at least a portion of the filament printing material undergoes a phase transition from a first phase to a second phase.

19. 14. The method of claim 13, wherein the printing material is maintained in a single phase during the heating of the filament printing material disposed within at least one of the ejector nozzles.

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