Metal deposition system

Abstract

Systems and methods for creating molten metal droplets are disclosed. The systems may be used for 3D printing. The system relies on a change in momentum of the droplet relative to the tip of the metal microwire to cause the droplet to separate from the tip of the metal microwire. The change in momentum can be created using a force generator. In some embodiments, the system can adjust electrical parameters to form metal droplets with desired parameters.

Description

[0001] METAL DEPOSITION SYSTEM

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application is a continuation-in-part of U.S. Pat. Appl . No. 19 / 011,465, filed on January 6, 2025, which is a continuation- in-part of U.S. Pat. Appl. No. 17 / 462,780, filed on August 31, 2021, since issued as U.S. Pat. No. 12,186, 600 on January 7, 2025, which claims priority to U.S. Prov. Pat. Appl. No. 63 / 074,261, filed on September 3, 2020. This application is also a continuation-in-part of U.S. Pat. Appl. No. 18 / 725, 638, filed on June 28, 2024, which is the national phase entry of PCT Appl. No. PCT / US2022 / 050699, filed on November 22, 2022, which claims priority to U.S. Prov. Pat. Appl. No. 63 / 281,919, filed on November 22, 2021, and U.S. Prov. Pat. Appl. No. 63 / 288,897, filed on December 13, 2021. This application also claims priority to each of U.S. Prov. Pat. Appl. No. 63 / 668,194, filed on July 6, 2024, U.S. Prov. Pat. Appl. No. 63 / 668,189, filed on July 6, 2024, U.S. Prov. Pat. Appl. No. 63 / 668,181, filed on July 6, 2024. The entire disclosure of each of these cases is incorporated herein by reference in its entirety.

[0004] FIELD

[0005] Embodiments of the present disclosure relate to devices, systems, methods and processes for generating or creating molten metal droplets on demand for additive manufacturing, layered creation of objects and parts, 3D printing or liquid metal printing . BACKGROUND

[0006] In liquid metal printing, molten metal droplets are used to build up 3 dimensional ( 3D) parts and obj ects by depositing droplets onto a build platform in layers . For example , feedstock material ( e . g . , metal wires ) may be heated to form metal droplets , which are then separated and deposited onto the build platform . Other examples of liquid metal printing processes use reservoirs , crucibles , pools , and / or other containments of molten metal from which droplets are generated using a single noz zle or, in some instances , multiple noz zles .

[0007] Liquid metal printing offers several advantages over traditional manufacturing techniques such as machining, casting, and powder-based additive manufacturing . For example , forming metal droplets enables highly efficient material usage with minimal waste , as feedstock can be directly converted into part material without the formation of scrap . Additionally, the architecture of the manufacturing system can be simpler and more compact than traditional systems such as laser or electron beam machines , leading to lower equipment costs and energy consumption .

[0008] Accordingly, a need exists for improved methods and systems for building 3D parts using molten metal droplets .

[0009] SUMMARY

[0010] This summary is provided to introduce a selection of concepts in a simpli fied form that are further described below in the Detailed Description section . This summary is not intended to identi fy or exclude key features or es sential features of the claimed subj ect matter, nor is it intended to be used as an aid in determining the scope of the claimed subj ect matter .

[0011] According to one aspect , the techniques described herein relate to a system for forming molten metal droplets on demand, the system including : a plurality of printheads arranged in a parallel fashion; and at least one wire feeder configured to control the delivery of a plurality of feedstock wires along a feed path, wherein each printhead is configured to heat the tips of at least one feedstock wire past its melting points such that metal droplets are formed .

[0012] In some embodiments , at least two of the printheads are at least one of electrically independent or mechanically independent .

[0013] In some embodiments , at least two of the printheads share a single wire feeder .

[0014] In some embodiments , at least two of the printheads are configured to form metal droplets from di f ferent feedstock wires .

[0015] In some embodiments , the tip of at least one feedstock wire is heated using an electric arc .

[0016] In some embodiments , the tip of at least one feedstock wire is heated using an adj acent feedstock wire as an electrode .

[0017] In some embodiments , the printheads are arranged as a plurality of parallel arrays .

[0018] In some embodiments , at least one array is configured to form metal droplets while at least one additional array is retracting . In some embodiments, the resolution of the printheads corresponds to the resolution of a build platform for receiving the metal droplets.

[0019] In some embodiments, the printheads are configured to construct a three-dimensional part using a print sequence based on the spatial arrangement of the printheads.

[0020] In some embodiments, the print sequence includes parallel scanning paths and a timed sequence for the printheads based on the spatial arrangement including an array.

[0021] In some embodiments, the print sequence is encoded in a G- code and M-code file.

[0022] According to another aspect, the techniques described herein relate to a method for forming molten metal droplets on demand, the method including: obtaining a plurality of feedstock wires at a plurality of printheads arranged in a parallel fashion; delivering, using at least one wire feeder, at least one feedstock wire along a feed path; and heating the tip of the at least one feedstock wire past its melting point such that a metal droplet is formed .

[0023] In some embodiments, at least two of the printheads are at least one of electrically independent or mechanically independent.

[0024] In some embodiments, the tip of at least one feedstock wire is heated using an electric arc. In some embodiments , the printheads are arranged as a plurality of parallel arrays .

[0025] In some embodiments , at least one array is configured to form metal droplets while at least one additional array is retracting .

[0026] In some embodiments , the resolution of the printheads corresponds to the resolution of a build platform for receiving the metal droplets .

[0027] In some embodiments , the method further includes generating a print sequence based on the spatial arrangement of the printheads ; and constructing a three-dimensional part using the formed metal droplets based on the print sequence .

[0028] In some embodiments , the print sequence is encoded in a G- code and M-code file .

[0029] According to one aspect , the techniques described herein relate to a system for forming metal droplets from a feedstock wire, the system including : a wire feeder configured to deliver a feedstock wire along a feed path; a heat source configured to heat the tip of the feedstock wire past its melting point such that a metal droplet is formed; and a movable carriage mechanically coupled to a force generator .

[0030] In some embodiments , the force generator includes a linear actuator that is configured to accelerate the movable carriage to ej ect the metal droplet from the feedstock wire .

[0031] In some embodiments , the heat source includes an electrode mechanically coupled to the movable carriage . In some embodiments, the linear actuator is configured to detach from the movable carriage after the metal droplet is formed.

[0032] In some embodiments, the force generator includes a piezoelectric actuator.

[0033] In some embodiments, the linear actuator is configured to: advance the movable carriage towards a build platform while being coupled with the movable carriage; change direction while being detached from the movable carriage; and recouple with the movable carriage to eject the droplet from the feedstock wire.

[0034] In some embodiments, the wire feeder is configured to accelerate the feedstock wire while the movable carriage is stationary.

[0035] In some embodiments, the wire feeder is configured to change direction to eject the metal droplet from the feedstock wire.

[0036] In some embodiments, the wire feeder includes a roller-based feeder .

[0037] In some embodiments, the wire feeder includes a first gripper, a second gripper, and a second linear actuator.

[0038] In some embodiments, the second linear actuator is configured to: deliver the feedstock wire towards a build platform while the first gripper grips the feedstock wire; and deliver the feedstock wire away from the build platform while the second gripper grips the feedstock wire. In some embodiments , the heat source includes a build platfor .

[0039] In some embodiments , the heat source includes an electrode wire mechanically coupled to the wire feeder .

[0040] In some embodiments , the feed path includes a bend .

[0041] In some embodiments , the system further includes a gripper configured to control the position of the feedstock wire after the metal droplet is formed .

[0042] According to another aspect, the techniques described herein relate to a system for forming metal droplets from a feedstock wire, the system including : a wire feeder configured to deliver a feedstock wire along a feed path; and an electrode configured to heat the tip of the feedstock wire past its melting point such that a metal droplet is formed .

[0043] In some embodiments , the system further includes a gripper to grip the feedstock wire after the feedstock wire is accelerated to ej ect the metal droplet from the feedstock wire .

[0044] In some embodiments , the wire feeder is configured to : accelerate the feedstock wire ; and change direction to ej ect the metal droplet from the feedstock wire .

[0045] In some embodiments , the wire feeder includes a roller-based feeder .

[0046] In some embodiments , the wire feeder includes a first gripper, a second gripper, and a linear actuator . According to one aspect , the techniques described herein relate to a method for forming metal droplets from a feedstock wire, the method including : setting at least one electrical parameter for an electrode ; and heating, using the electrode , the tip of the feedstock wire to form a metal droplet ; and ej ecting the metal droplet from the feedstock wire towards a build platform, the ej ected metal droplet having at least one desired property based on the electrical parameter .

[0047] In some embodiments , the electrical parameter includes at least one of a polarity, an arc time, a voltage level , a current level , or a number of arcs .

[0048] In some embodiments , the method further includes setting at least one physical configuration parameter for the feedstock wire , wherein the desired property is further based on the physical configuration parameter .

[0049] In some embodiments , the physical configuration parameter includes at least one of a position of the feedstock wire relative to the electrode or motion of the feedstock wire relative to the electrode during the formation of the metal droplet .

[0050] In some embodiments , the desired property includes at least one of a desired temperature , a desired velocity, or a desired si ze .

[0051] In some embodiments , the electrode includes the build platform . In some embodiments , the method further includes heating the ej ected metal droplet using a secondary heat source .

[0052] In some embodiments , the heating of the ej ected metal droplet includes generating a plasma arc in a drop path of the metal droplet using the secondary heat source .

[0053] In some embodiments , the method further includes heating a landing spot at a substrate at the time of impact using the secondary heat source .

[0054] In some embodiments , the method further includes forming a weakly bonded interface layer for a support structure using the ej ected metal droplet .

[0055] According to one aspect , the techniques described herein relate to a system for forming metal droplets from a feedstock wire, the system including : an electrode configured to heat the tip of the feedstock wire past its melting point such that a metal droplet is formed and ej ected from the feedstock wire towards a build platform; and a controller configured to set at least one electrical parameter for the electrode, the ej ected metal droplet having a desired property based on the electrical parameter .

[0056] In some embodiments , the electrical parameter includes at least one of a polarity, an arc time, a voltage level , a current level , or a number of arcs .

[0057] In some embodiments , the controller is configured to set at least one physical configuration parameter for the feedstock wire . In some embodiments , the physical configuration parameter includes at least one of a position of the tip of the feedstock wire relative to the electrode or motion of the feedstock wire relative to the electrode during the formation of the metal droplet .

[0058] In some embodiments , the desired property includes at least one of a desired temperature , a desired velocity, or a desired si ze .

[0059] In some embodiments , the electrode includes the build platform .

[0060] In some embodiments , the systems further includes a secondary heat source configured to heat the ej ected metal droplet .

[0061] In some embodiments , the heating of the ej ected metal droplet includes generating a plasma arc in a drop path of the metal droplet using the secondary heat source .

[0062] In some embodiments , the secondary heat source is further configured to heat a landing spot at a substrate at the time of impact .

[0063] In some embodiments , the ej ected metal droplet is used to form a weakly bonded interface layer for a support structure .

[0064] BRIEF DESCRIPTION OF THE FIGURES For a better understanding of the present disclosure, reference is made to the accompanying drawings, which are incorporated herein by reference and in which:

[0065] FIG. 1 shows an apparatus for the deposition of molten metal according to one embodiment; and

[0066] FIG. 2 shows a printhead according to one embodiment;

[0067] FIG. 3 shows a printhead according to a second embodiment;

[0068] FIGs. 4A-4D show one mechanism to separate the droplet from the metal microwire;

[0069] FIGs. 5A-5D show a second mechanism to separate the droplet from the metal microwire;

[0070] FIGs. 6A-6D show a third mechanism to separate the droplet from the metal microwire;

[0071] FIGs. 7A-7B show the printhead according to another embodiment ;

[0072] FIG. 8 shows a printhead with a stationary heat source; and

[0073] FIGs. 9A-9D show one mechanism to heat and separate the droplet from the metal microwire using a stationary heat source.

[0074] FIG. 10 shows a system with a printhead in accordance with an embodiment .

[0075] FIG. 11 shows a system with multiple printheads in accordance with an embodiment.

[0076] FIG. 12 shows a system with a printhead array in accordance with an embodiment.

[0077] FIG. 13 shows a system with a two-dimensional printhead array in accordance with an embodiment.

[0078] FIGs. 14A-14B show embodiments of another system with a printhead .

[0079] FIG. 15 shows a flowchart of a method for forming metal droplets in accordance with an embodiment.

[0080] FIG. 16 shows a flowchart of a method for generating a print sequence in accordance with an embodiment. FIG. 17 shows a system for forming metal droplets using a catch window in accordance with an embodiment.

[0081] FIG. 18 shows another system for forming metal droplets in accordance with an embodiment.

[0082] FIG. 19 shows yet another system for forming metal droplets in accordance with an embodiment.

[0083] FIG. 20 shows a flowchart of another method for forming metal droplets in accordance with one embodiment.

[0084] DETAILED DESCRIPTION

[0085] FIG. 1 shows an apparatus creating molten metal droplets. These molten metal droplets are used to build up 3 dimensional (3D) parts and objects by dispensing droplets onto a build-platform in layers .

[0086] The apparatus comprises one or more metal wire sources 1. These metal wire sources 1 may be metal microwire cartridges, spools or supplies. In the embodiment where more than one metal wire source 1 is employed, these metal wire sources 1 may contain the same or different types of metal microwire. A printhead 2 is in communication with the metal wire sources 1. The printhead 2 generates molten metal droplets 3 that are ejected towards a build platform 4 on which metal parts are created from layers.

[0087] A controller 5, such as a computer, server, dedicated microcontroller or other suitable processing unit, supplies instructions to the apparatus. The controller 5 may be directly attached to the apparatus or may communicate through a network or the internet. The instructions from the controller to the apparatus are derived from the desired part to be created . The desired part is sliced into a plurality of cross-sectional areas , each corresponding to a respective one of the layers by which the apparatus will build up the part .

[0088] The metal microwire 7 may be in the range of 50 to 3000 micrometers in diameter . The advancement of the metal microwire 7 from the metal wire source 1 to the printhead 2 may be achieved through the use of a piezo actuator, a stepper motor or a voicecoil . In certain embodiments , there is a single actuator to advance the metal microwire . In other embodiments , multiple actuators working together may be used .

[0089] The printhead 2 may contain a single molten metal droplet generator or an array of molten metal droplet generators , each being supplied with the same type of metal microwire or di f ferent types of metal microwire . The printhead 2 ej ects molten metal droplets 3 towards a build platform 4 through use of the molten metal droplet generators . The printhead 2 is capable of ej ecting droplets at a maximum frequency . The minimum time between droplets may be referred to as a droplet generation cycle . Additionally, the printhead 2 is capable of skipping one or multiple droplets , also referred to as drop on demand . In the XY plane , the printhead 2 and build platform 4 move relative to each other either in a vector, tool-path kind of traj ectory or in a rastering scanning type of motion . The ej ected molten metal droplets 3 are laid down in a layer according to the instruction sent by the controller 5 . As noted above , the 3-dimensional part or obj ect is built up from multiple layers . The printhead 2 and the build platform 4 may also more relative to each other in the Z direction . FIG . 2 shows an expanded view of the printhead 2 . The printhead 2 includes a carriage 6 , which holds the metal microwire 7 . The carriage 6 is held by linear guides 11 , disposed on opposite sides of the carriage 6. The carriage 6 may be able to move relative to the linear guides 11 , such as in an up and down direction . In certain embodiments , the linear guides 11 limit the movement of the carriage to only one direction, such as up and down, left and right, or forward and backward . For example , a rod

[0090] 15 or other rigid member may be used to connect the carriage 6 to a rotating component 16 , such as a cylinder . The rotating component 16 may be driven by a motor at a fixed or variable RPM . The rod 15 is coupled to the rotating component 16 at a location that is not the axis of rotation . The center of the rotating component 16 is fixed, such that rotation of the rotating component

[0091] 16 causes the rod 15 to move in a reciprocating fashion, causing the carriage 6 to move relative to the linear guides 11 . The rotating component 16 may rotate at the maximum frequency of the printhead, such that the carriage 6 moves up and down for the generation of each droplet . In certain embodiments , the carriage 6 may move in the X or Y directions relative to the linear guides 11 .

[0092] Within the carriage 6 may be one or more actuators 8 to advance the metal microwire 7 through the carriage 6 . In some embodiments , the actuators 8 may be located on the carriage 6 . In other embodiments , the actuators 8 may be locator of f the carriage 6, in which case a flexible drive shaft may connect the carriage 6 to the actuators 8 . The actuators 8 may be piezo electric devices or motors . The metal microwire 7 is advanced in a way such that the distance advanced can be controlled . A variety of di f ferent heat sources may be used to heat the tip of the metal microwire 7 to form the metal droplet 13 .

[0093] In one embodiment , light conduit 9, such as a fiber optic cable, may be disposed proximate the carriage 6 . Light , in the form of a laser beam, may be transmitted through the light conduit 9 . The light conduit 9 may have a curved portion such that the laser beam is focused at the end of the metal microwire 7 . The fiber optic cable may include a lens 10 to focus the emergent beam at the tip of the metal microwire 7 . The energy from the laser beam may cause the tip of the metal microwire 7 to transition from a solid to a liquid, so as to form a droplet .

[0094] In another embodiment , a laser may not be used . Rather, a di f ferent heat source , such as an induction coil , may be used to heat the tip of the metal microwire 7 to create a liquid . This embodiment is shown in FIG . 3 . Similar components have been given identical reference designators . In this embodiment, the laser is replaced with an induction coil 14 , which may encircle the tip of the metal microwire 7 . When a quantity of power is applied to the induction coil 14 , as determined according to the properties of the induction coil 14 and the material , diameter and length of the metal microwire within it, the tip of the metal microwire 7 is heated and transitions to the liquid state .

[0095] In another embodiment , the heat source used to melt the tip of the metal microwire 7 might not be a laser or induction coil but a plasma arc . Embodiments that utili ze a plasma arc 19 are shown in FIGs . 7A-7B . Similar components have been given identical reference designators . In the embodiment shown in FIG . 7A, a plasma arc 19 is created between two electrodes 18 by applying an electric potential across the gap of the electrodes 18 which may or may not be filled with gas other than air, such as shield gas . The voltage applied to the electrodes 18 may be an AC or DC voltage . The magnitude of the voltage may be determined based on the distance between the electrode 18 , the thickness of the metal microwire 7 and the type of metal used . The voltage may be applied to one electrode or both electrodes . Those skilled in the art may readily determine the appropriate magnitude of the voltage based on these parameters . The plasma arc 19 is hot enough to melt the metal microwire 7 from solid to liquid . The tip of the metal microwire 7 is advanced into the plasma arc 19 , which will heat and transition the metal microwire 7 to liquid state .

[0096] In the embodiment shown in FIG . 7B, the tip of the metal microwire 7 serves as one of the two electrodes 18 creating the plasma arc 19 which will also heat and transition the metal microwire 7 to liquid state . In certain embodiments , the metal microwire 7 is grounded and the electrode 18 is supplied with a voltage , which may be AC or DC voltage . Further, the voltage applied to the electrode 18 may be positive or negative . In other embodiments , this voltage may be applied to the metal microwire 7 . In yet other embodiments , voltages are applied to both the metal microwire 7 and the electrode 18 . These voltages may be AC or DC, positive or negative and may vary in magnitude .

[0097] In some embodiments , the heat source is designed such that the quantity and rate of heat energy applied to the tip of the metal microwire 7 is such that the metal microwire 7 above the tip remains a solid . In other embodiments , the metal microwire above the tip remains a solid due to active temperature management of the metal microwire 7 , such as via conduction or convection . In all embodiments , the droplet si ze is controlled by the distance the metal microwire 7 is advanced by the actuator 8 . In some embodiments , the metal droplets 13 may have a diameter in the range of 150 to 3000 micrometers . Additionally, one or more droplets may be skipped by not advancing the metal microwire 7 .

[0098] In certain embodiments , a hard stop 12 may be provided on the linear guide 11 .

[0099] The metal droplet 13 may be separated from the tip of the metal microwire 7 through a change in momentum . Three di f ferent embodiments are described, each capable of creating changes in momentum, which impart a force to the metal droplet 13 that may be in excess of 10G . In certain embodiments , the force is in excess of 100G . In some embodiments , the force applied to the metal droplet 13 may be on the order of 1000G or more , thus reducing the influence of gravity on the orientation of the droplet separation and subsequent traj ectory to a minimum .

[0100] In the first embodiment, shown in FIGs . 4A-4D, the metal droplet 13 is released using oscillation . First , as shown in FIG . 4A, the carriage 6 starts to move in a first oscillating direction due to the rotation of rotating component 16 . This may be the downward direction . As shown in FIG . 4B, while the carriage 6 is moving in the first oscillating direction, the metal microwire 7 is advanced by the actuator 8 and the wire tip is melted from solid to liquid phase . The amount of metal that forms the droplet is determined by the speed of the actuator 8 , the speed of the carriage 6, and the diameter of the microwire . The molten metal droplet receives the direction of the movement . At the end of the oscillation movement, shown in FIG . 4C, the carriage 6 decelerates , changes direction and accelerates again in the opposite second direction . The rate of deceleration, the rate of acceleration, the velocity and the distance traveled for the oscillation movement are chosen according to microwire diameter, droplet diameter and droplet mass in order to force a separation of the metal droplet 13 from the metal microwire 7 and guarantee that the metal droplet 13 continues its movement in the direction received during the original first direction of the oscillation movement ( see FIG . 4B ) . As shown in FIG . 4D, the carriage 6 travels in the second, opposite , direction until it reaches its original position where it decelerates , changes direction and accelerates again to start the next period cycle . Note that whi le FIGs . 4A-4D show the oscillation occurring in the Z direction, the carriage 6 and linear guides 11 may be configured so that the oscillation occurs in the X or Y direction . While FIGs . 4A-4D show a printhead with a laser, it is understood that the same sequence applied to a printhead with another heat source, such as an induction coil or a plasma arc .

[0101] In the second embodiment , shown in FIGs . 5A-5D, the metal droplet 13 is released using oscillation with a hard stop . This embodiment is similar to the previous embodiment . First , as shown in FIG . 5A, the carriage 6 moves in a first oscillating direction due to the rotation of rotating component 16 . This may be the downward direction . As shown in FIG . 5B, while the carriage 6 is moving in the first oscillating direction, the metal microwire 7 is advanced by the actuator 8 and the wire tip is melted from solid to liquid phase . The amount of metal that forms the droplet is determined by the speed of the actuator 8 , the speed of the carriage 6, and the diameter of the microwire . The molten metal droplet receives the direction of the movement . At the end of the oscillation movement, shown in FIG . 5C, the carriage 6 decelerates , strikes the hard stop 12 , changes direction and accelerates again in the opposite direction . The rate of deceleration, the rate of acceleration, the velocity and the distance traveled for the oscillation movement are chosen according to microwire diameter, droplet diameter and droplet mass in order to force a separation of the metal droplet 13 from the metal microwire 7 and guarantee that the metal droplet 13 continues its movement in the direction received during the original first direction of the oscillation movement ( see FIG . 5B ) . In certain embodiments , the carriage 6 may not decelerate before striking the hard stop 12 . As shown in FIG . 5D, the carriage 6 travels in the second, opposite , direction until it reaches its original position where it decelerates , changes direction and accelerates again to start the next period cycle . Note that while FIGs . 5A-5D show the oscillation occurring in the Z direction, the carriage 6 and linear guides 11 may be configured so that the oscillation occurs in the X or Y direction . Additionally, while FIGs . 5A-5D show a printhead with a laser, it is understood that the same sequence applied to a printhead with another heat source , such as an induction coil or a plasma arc .

[0102] In the third embodiment, shown in FIGs . 6A- 6D, the metal droplet 13 is released using momentum transfer . In this embodiment, the carriage is exposed to periodic momentum transfers . First, as shown in FIG . 6B, while the carriage 6 is moving in the first oscillating direction, the metal microwire 7 is advanced and the wire tip is melted from solid to liquid phase . The amount of metal that forms the droplet is determined by the speed of the actuator 8 , the speed of the carriage 6 , and the diameter of the microwire . Upon formation of the desired droplet , the carriage 6 receives a momentum in the desired direction of droplet movement and trans fers that momentum to the molten metal droplet , as shown in FIG . 6C . For example , in one embodiment , the carriage 6 is stationary . The rod 15 is in communication with a mass 17 . As the rotating component 16 rotates , the mass 17 moves up and down . The rod 15 and the mass 17 are dimensioned such that the mass 17 impacts the carriage 6 at the bottom of its stroke . Upon receiving the momentum, the metal droplet 13 separates from the metal microwire 7 and moves in the direction of the momentum, as shown in FIG . 6D . The next period cycle starts . Additionally, while FIGs . 6A- 6D show a printhead with a laser, it is understood that the same sequence applied to a printhead with another heat source , such as an induction coil or a plasma arc .

[0103] In still another embodiment , the carriage 6 is accelerated to at least a desired drop speed and has a high-speed retracting mechanism such as a piezoelectric actuator on board that retracts the metal microwire 7 after a drop has been formed to separate the drop from the wire 7 . Then the carriage 6 is decelerated and reverses direction to return to the top of its stroke to repeat the process again while the separated drop moves in the direction of its momentum to the build bed for deposition . This separation approach of fers tunable timing of acceleration and drop separation and an impact free momentum change for drop separation that reduces vibration and hardware wear .

[0104] While each of the previous figures shows the heat source as being mounted or coupled to the carriage , other embodiments are also possible . For example , as shown in FIG . 8 , the heat source 20 , which may be a laser beam, induction coil or plasma arc is not fixed to the carriage 6 but remains stationary in relation to the linear guides 11 . Other aspects of this embodiment are similar to those described above and similar components have been given identical reference designators . In this embodiment , the heat source 20 is located at the point where the oscillation reverses direction and the metal droplet 13 separates from the tip of the metal microwire 7 .

[0105] FIGs . 9A- 9D show the operation of the printhead of FIG . 8 . As shown in FIG . 9A, the sequence of events starts with the metal microwire 7 in the full advanced position while the carriage 6 starts to move in the first direction . This may be the downward direction . The motion of the carriage 6 will cause the metal microwire 7 to be inserted into the heat source 20 which will melt the metal microwire 7 from solid to liquid form . During the movement in the first direction, metal microwire 7 is continuously advanced into the heat source by the actuator 8 , increasing the amount of metal used to form the droplet . At the end of the oscillation movement, shown in FIG . 9C, the carriage 6 decelerates , changes direction and accelerates again in the opposite second direction . The rate of deceleration, the rate of acceleration, the velocity and the distance traveled for the oscillation movement are chosen according to microwire diameter, droplet diameter and droplet mass in order to force a separation of the metal droplet 13 from the metal microwire 7 and guarantee that the metal droplet 13 continues its movement in the direction received during the original first direction of the oscillation movement , as shown in FIG . 9C . As shown in FIG . 9D, the carriage 6 travels in the second, opposite , direction until it reaches its original position where it decelerates . During the motion in second direction, the metal microwire 7 is advanced to start the next period cycle . This embodiment of the mechanism has advantages in regards to timing of events and might be used to achieve certain frequencies of droplet generation . Although not shown, the embodiments of FIGs . 5A-5D and 6A- 6D may also be implemented using a heat source that remains stationary with respect to the linear guides 11 .

[0106] In each of these embodiments , the controller 5 may be in communication with the actuator 8 , the motor that controls the rotating component 16, and the heat source to perform the actions described herein .

[0107] All embodiments described herein can be used in various , nonvertical orientations . As described above , the force that is exerted upon the metal droplet 13 and causes the metal droplet 13 to separate from the metal microwire 7 may be much greater than the force of gravity . The momentum' s direction, which is also the direction of the printhead' s oscillation, will be maintained by the metal droplet 13 and determines its traj ectory . In a nonvertical orientation, gravity will have a small influence on the droplet ' s traj ectory, possibly causing the otherwise straight traj ectory to be slightly curved . Compared to the force of molten metal surface tension, gravity also has a small influence of sub millimeter scale molten metal droplets , thus enabling layer by layer fabrication of molten metal droplet structures on a vertical platform .

[0108] The embodiments described in this disclosure may have many advantages . The separation of the droplet may be more predictable and the timing of this separation may also be more predictable . Additionally, the present system has the capability for creating droplets of a higher temperature and from di f ferent types of metal . This system also allows a higher frequency with which droplets can be separated . The system can also be parallelized into an array of droplet generators , resulting in higher throughput and lower unit cost .

[0109] Parall el Printhead Arrays

[0110] As described above , liquid metal printing involves using molten metal droplets to print 3D parts . Conventional liquid metal printing techniques often rely on crucibles , reservoirs , and / or pools of molten metal to store the material used for forming the droplets . Typically, such systems employ noz zles to ej ect the droplets onto the desired locations . These systems , however, present various challenges such as consistency and repeatability of the molten metal droplet traj ectory, drop on demand in multinoz zle scenarios , scalability of metal throughput, high temperature materials , complexity of control systems , maintenance scope and intervals , and time between failures .

[0111] Conventional printheads for generating metal droplets are also limited in their capacity for parallelization . For example , their cost, complexity, and physical si ze make it impractical to deploy them in large numbers . Crucible-based printheads with molten reservoirs are particularly di f ficult to pack closely together because each crucible requires dedicated space for heating and insulation and because fitting multiple noz zles into a shared reservoir introduces interference among j etting forces . These constraints hinder ef forts to increase throughput by arraying multiple printheads .

[0112] Accordingly, embodiments described herein include systems and methods for forming molten metal droplets using paralleli zed printheads . An exemplary system may include a plurality of printheads arranged in a parallel fashion, and at least one wire feeder configured to control the delivery of a plurality of feedstock wires along a feed path . Each printhead may be configured to heat the tips of at least one feedstock wire past its melting points such that metal droplets are formed .

[0113] The embodiments described herein may provide several advantages over traditional methods . For example , the described embodiments may eliminate the need for a reservoir or crucible of molten metal . Instead, metal droplets may be formed directly from solid feedstock wire by locali zed heating and then deposited on demand .

[0114] The described embodiments may enable a highly modular and scalable droplet deposition system . For example , in some embodiments , multiple wire-based printheads may be arranged in a parallel array, thereby facilitating high-throughput operation suitable for large- format or rapid production applications . By using discrete wire inputs rather than a shared molten pool , each printhead may operate independently, allowing for selective activation and feedstock variation across the array .

[0115] The described embodiments may allow for a minimal footprint and compact form factor . In some embodiments , the droplet formation may be confined to the wire tip, and the footprint of the wire tip may be defined by the arcing distance and the mechanisms of the force generator . These limitations may be further reduced by using a wire feeder located of f to the side . In such configurations , the footprint of a printhead may be reduced to the diameter of the wire feeding tube and the required arcing standof f between adj acent wires . This compact arrangement enables high-density packing of printheads within an array, signi ficantly improving system throughput without sacri ficing precision or controllability .

[0116] FIG . 10 shows a system with a single printhead 1000 in accordance with an embodiment . The system may be configured to create metal droplets for printing various 3D parts .

[0117] The system may include the printhead 1000 , a wire feeder 1002 , and a feedstock wire 1004 . The feedstock wire 1004 may be any suitable metal wire . As shown, the feedstock wire 1004 may be sourced from a spool , although the feedstock wire 1004 may be sourced from any suitable wire source . The feedstock wire 1004 may be contained within a feeding tube .

[0118] The wire feeder 1002 may be configured to feed the feedstock wire 1004 to the printhead 1000 . The printhead 1000 may be configured to melt the tip of the feedstock wire 1004 to form molten metal droplets . The printhead 1000 may ej ect the metal droplets towards a build platform to form a part . The printhead 1000 may form the droplets without requiring a reservoir or crucible .

[0119] In some embodiments , the system may be paralleli zed by arranging multiple printheads in close proximity to each other . By eliminating the need for large crucibles and reservoirs , the spatial footprint of each printhead may be minimized .

[0120] FIG . 11 shows a system with multiple printheads 1100 in accordance with an embodiment . As shown, the printheads 1100 may be placed adj acent to each other in a parallel fashion . As shown, the printheads 1100 may use separate feedstock wires 1102 to form metal droplets . In some embodiments , the feedstock wires 1102 may include the same feedstock material for high- throughput deposition of a single material . In some embodiments , the feedstock wires 1102 may include dif ferent feedstock material for performing multi-material printing . The materials may have di f ferent properties such as ductility, conductivity, and / or hardness . For example , the system may use both conductive and structural feedstocks for integrating electronic components directly into the part .

[0121] In many traditional printing systems , the printheads use dedicated electrodes for melting the feedstock wires . Bringing printheads into close proximity with each other, however, may allow a wire to serve as an electrode for an adj acent wire serving as the feedstock . The role that each wire serves may be controlled by the applied polarity . By selectively controlling the polarity, the roles of electrode and feedstock may be dynamically alternated between neighboring wires . Using wires as electrodes may allow electrode performance to remain consistent throughout the printing process by eliminating the degradation typically associated with fixed electrodes . This may be particularly beneficial in high- throughput systems where di f ferent printheads may be subj ect to varying drop loads . The configuration also removes the need for separate electrode components , thereby simplifying the system architecture and improving operational reliability .

[0122] FIG . 12 shows a system with a printhead array 1200 in accordance with an embodiment . The printhead array 1200 may include multiple printheads arranged in a parallel fashion . The printheads may use separate feedstocks and / or share feedstocks with other printheads . In some embodiments, the printhead array 1200 may be configured to deposit metal droplets on the build platform by scanning the build platform from side to side, rather than through sequential point-by-point placement by a single printhead. In this configuration, the printhead array 1200 may traverse the build platform in at least one linear pass, with multiple printheads simultaneously generating and depositing droplets in accordance with the desired part geometry. This may enable faster build rates, reduced mechanical complexity, and / or greater spatial uniformity in droplet distribution, thereby enhancing the scalability and efficiency of the manufacturing process.

[0123] FIG. 13 shows a system with a two-dimensional (2D) printhead array 1300 in accordance with an embodiment. The printhead array 1300 may include multiple rows of printheads (e.g. , multiple instances of the printhead array 1200) . By using a 2D array, the system may enable increased throughput for droplet formation. Each row may be configured to support wire electrode pairings. In this arrangement, adjacent wires within a single row and / or between neighboring rows may be paired for arcing and droplet generation.

[0124] In some embodiments, each row of the printhead array 1300 may be slightly offset from adjacent rows (e.g. , in the X-direction) to fill gaps left by the adjacent rows, thereby increasing the effective resolution across the build platform.

[0125] The system may activate and / or retract the rows of the printhead array 1300 in any suitable sequence. In some examples, the system may activate a portion of the rows at a time. For example, one row may actively generate droplets while another row (e.g., an adjacent row) is retracting or preparing for further deposition . This may allow for continuous or near-continuous deposition, ef fectively increasing the droplet generation frequency across the printhead array 1300 . In some examples , the system may activate and / or retract all the rows simultaneously . In some examples , the system may activate the rows in a cascading pattern . The rows may be activated in sequence so that each row is activated following the activation of an adj acent row .

[0126] In some embodiments , the system may include at least one high- precision wire feeder configured to advance and retract feedstock wires at print frequencies . The wire feeder may operate without performance degradation over time and accommodate a wide range of wire materials and properties .

[0127] In some embodiments , the resolution of the printhead array 1300 may be configured to match or approximately match the print resolution of the build platform . In this configuration, the system may print the part with minimal printhead motion . As a result , the need for a printhead motion system may be eliminated entirely, thereby simpli fying the system architecture .

[0128] In some embodiments , the system may control the printhead array 1300 using a printhead addressing scheme to selectively activate , retract , and / or disable speci fic printheads . The addressing may be achieved using multiplexed electrical buses , where a shared control signal line is combined with digital selection logic to address each printhead individually or in selected groups . For example , the printhead array 1300 may be divided into independent zones , with each zone operating independently from other zones . Such multiplexing may allow for a signi ficant reduction in wiring complexity and controller overhead, particularly in arrays containing dozens or hundreds of printheads .

[0129] While FIGs . 11-13 show printheads arranged as parallel arrays , it is to be appreciated that the printheads may be arranged in any suitable manner . For example , the printheads may be arranged in a hexagonal pattern, a radial pattern, and / or a helical pattern .

[0130] In some embodiments , a set of printheads may be configured so that each printhead operates independently with its own dedicated force generator, feedstock wire, and / or electrical system. The printheads may be electrically independent and / or mechanically independent . The set of printheads may approximate the size of the build platform itsel f . In this configuration, each printhead is responsible for a specific region of the part .

[0131] FIG . 14A shows a system with a printhead in accordance with an embodiment . The printhead 1400 may be an independent printhead that forms droplets from a single feedstock wire 1402 that is fed by a dedicated wire feeder 1404 .

[0132] This configuration may enable spatial division of the build volume , where each printhead is responsible for a specific sector of the part , thereby enhancing overall throughput and enabling fault isolation between printheads .

[0133] In some embodiments , the set of printheads may be configured so that multiple printheads share the same force generator and / or electrical system . The shared wires may include the same feedstock material or di f ferent feedstock material . Each printhead may be independently addressable (e.g., using software) so that specific printheads can be controlled electronically.

[0134] FIG. 14B shows an alternate embodiment of the system shown in FIG. 14A. As shown, two feedstock wires 1402 may share the wire feeder 1404 to form the two dependent printheads 1400.

[0135] FIG. 15 shows a flowchart of a method for forming metal droplets in accordance with an embodiment. While FIG. 15 shows illustrative operations according to one embodiment, other embodiments may omit, add to, reorder, and / or modify any of the operations shown in FIG. 15. Moreover, each of the operations depicted in FIG. 15 may be performed in any of the ways described herein. The operations shown in FIG. 15 may be performed by any of the illustrative systems described herein.

[0136] Operation 1500 may include obtaining a plurality of feedstock wires at a plurality of printheads arranged in a parallel fashion.

[0137] Operation 1502 may include delivering, using at least one wire feeder, at least one feedstock wire along a feed path.

[0138] Operation 1504 may include heating the tip of the feedstock wire past its melting point such that a metal droplet is formed.

[0139] In some embodiments, printing a part using metal droplets may be based on a generated print sequence. The print sequence may indicate information needed for printing the desired part, such as which droplets to place, the order of the droplet placements, the timing of the droplet placements, and the specific printheads used to form the droplets. FIG. 16 shows a flowchart of a method for generating a print sequence in accordance with an embodiment. While FIG. 16 shows illustrative operations according to one embodiment, other embodiments may omit, add to, reorder, and / or modify any of the operations shown in FIG. 16. Moreover, each of the operations depicted in FIG. 16 may be performed in any of the ways described herein. The operations shown in FIG. 16 may be performed by any of the illustrative systems described herein, such as the controller 5 shown in FIG. 1 and / or any other suitable controller.

[0140] Operation 1600 may include receiving a 3D part geometry for a desired part. The part geometry may be a representation that defines the geometry, dimensions, and / or features of the desired part. The part geometry may be encoded as a digital model. For example, the digital model may be a CAD model in any suitable format, such as STL, STEP, OBJ, and / or AMF. In some embodiments, operation 1600 may include receiving metadata associated with the desired part, such as part identifiers, orientation preferences, material requirements, and / or surface finish preferences.

[0141] Operation 1602 may include generating z-layer outlines of the part geometry. The outlines may represent 2D cross-sectional layers of the part geometry. The part geometry may be sliced into discrete layers along the z-axis to product the z-layer outlines of the part.

[0142] In some embodiments, an x-y offset may be applied before generating the z-layer outlines. The x-y offset may adjust the x- y dimensions of the part geometry by expanding or contracting the outer perimeters. Applying the XY offset first may compensate for droplet spread, thermal expansion, and / or shrinkage. Operation 1604 may include generating drop center points for the print sequence . The drop center points may be spatial coordinates representing the locations where individual metal droplets are to be deposited during the printing of the part .

[0143] Various drop placement strategies may be used to generate the drop center points . In some embodiments , the strategies may be determined based on a corresponding region of the part . For example , drops may be evenly spaced along the perimeter outline of each z-layer . This may include tracing the contour of the layer and placing center points at regular intervals based on a selected droplet diameter or spacing criterion .

[0144] For internal regions , the system may employ a grid-based packing strategy, such as by intersecting a hexagonal grid or circling packing pattern with the inner perimeter of a layer . Alternatively or additionally, the total surface area and / or cross-sectional area of a z-layer may be calculated and divided by the ef fective coverage area of a single droplet . The drop center points may be distributed using packing patterns ( e . g . , circle packing) to evenly fill the available space while avoiding overlaps or voids .

[0145] Operation 1606 may include generating a print sequence . The print sequence may include any of the information generated at operations 1600-1604 , such as the drop center points .

[0146] In some embodiments , the print sequence may include scanning paths for the printheads . The scanning paths may be determined based on the spatial arrangement of the printheads . For example , i f the printheads are arranged in a 2D grid array pattern ( e . g . , as shown in FIG . 13 ) , the part may be divided into grid sectors , with each sector assigned to a particular printhead. The scanning paths may be generated across the part as parallel lines. A drop release timing sequence may be generated to be synchronized with the motion of each printhead.

[0147] If the printheads are arranged as a linear array (e.g. , as shown in FIG. 12) , the drop center points may be rasterized with array positions. Parallel line scanning paths and a drop release timing sequence may be generated (e.g. , as described with the 2D grid array case) .

[0148] If the printheads are arranged as dual printheads, the part geometry may be split into grid sectors, with each grid sector assigned to a dual printhead. The drop center points may be paired according to printhead spacing. Scanning paths may then be determined for the drop center points, such as by generating a shortest path through the drop center points. Generating the shortest path may be modeled as a traveling salesperson problem. Any appropriate algorithm may be used to solve the traveling salesperson problem, such as brute force algorithms, dynamic programming algorithms, and / or linear programming algorithms.

[0149] If the printheads are arranged as single printheads, scanning paths may be determined by generating a shortest path (e.g. , as described with the dual printhead case) .

[0150] In some embodiments, the scanning paths may be determined using other criteria, such as maximizing motion efficiency, minimizing backtracking, and / or minimizing thermal gradients. In some examples, the scanning paths may be based on a motion smoothing technique. The motion smoothing technique may be any technique that reduces sudden momentum changes for the printhead. For example , the speed of the printhead may be reduced when navigating sharp turns or angular changes in the print seguence . In some examples , the sharp turns and / or angular changes may be removed ( e . g . , by using curved paths ) .

[0151] Operation 1608 may include generating a file based on the print sequence . The file may be formatted as a G- and M-code file , although it is to be appreciated that the file may be written in any suitable language , such as Python, MATLAB, and / or Lua . The file may contain computer instructions to be used by a suitable system ( e . g . , the system shown in FIG . 1 ) for printing the desired part .

[0152] Printhead Moti on Control

[0153] Many traditional liquid metal printing techniques use crucibles to store molten metal for forming metal droplets . The crucibles maintain the metal in a liquid state suitable for droplet formation . However, crucibles inherently possess a high thermal mass . As a result, crucible-based techniques are unable to quickly change drop temperature between drops to modulate the temperature of individual droplets in real time .

[0154] Additionally, crucible-based techniques often employ a range of liquid j etting methods to ej ect droplets from the crucible , such as magnetohydrodynamic (MHD) propulsion, inductive pulse heating, and mechanical actuation using plungers or pistons . These techniques are often complex and require signi ficant infrastructure to implement . For example, MHD and inductive systems require precise electromagnetic field control and high- frequency power delivery systems , while mechanical plunger systems require finely tuned actuators with coordinated timing mechanisms . Such complexity contributes to increased costs , reduced reliability, and larger physical footprints . Crucible noz zles are also subj ect to high thermal loads and repeated cycling, which can lead to noz zle degradation . Over time, such degradation may affect the shape and consistency of ej ected droplets , resulting in inconsistent droplet properties .

[0155] Accordingly, embodiments described herein include systems and methods for forming metal droplets from feedstock wires . An exemplary system may include a wire feeder configured to deliver a feedstock wire along a feed path, a heat source configured to heat the tip of the feedstock wire past its melting point such that a metal droplet is formed, and a movable carriage mechanically coupled to a force generator . The described embodiments may form and ej ect the metal droplets in multiple steps , such as wire feeding, melting, droplet formation, and controlled separation of the droplet towards the build platform .

[0156] In some embodiments , a printing system may include a printhead that is fed feedstock wire . The printhead may be accelerated using a force generator, such as a linear actuator . During this acceleration, the printhead may melt the tip of the wire ( e . g . , via an electrode using electrical arcing, resistive heating, etc . ) to form a molten droplet . Controlling the motion profile of the printhead may cause separation of the droplet from the wire in a desired manner . In some embodiments , the electrode used to melt the wire may be mechanically coupled to the printhead and may travel with the printhead, thus maintaining a fixed spatial relationship between the wire and the electrode .

[0157] In some embodiments , the printhead may remain stationary while the wire itsel f is accelerated using an appropriate force generator ( e . g . , a wire feeder ) and melted . The molten droplet may be formed at the tip of the wire . The droplet may be detached by imparting a rapid momentum change to the wire . The momentum change may be accomplished through an abrupt halt using a wire gripper or by reversing the wire feeder . Accelerating the wire may allow for precise control of droplet release while minimizing mechanical complexity in the printhead .

[0158] In some embodiments , the electrode may remain stationary, with only the wire undergoing motion . This may minimi ze the mass being accelerated and thus improve dynamic responsiveness . The wire may move toward the melt zone at a velocity that exceeds the upward climb of the droplet along the wire .

[0159] Various types of wire feeders may be used to accelerate the wire . In some examples , a roller-based feeder may be used . The roller-based feeder may impart motion to the wire using rollers arranged to grip the wire between them . In some examples , a two- gripper system may be used in combination with a linear actuator . A top gripper may secure the wire while the lower gripper remains open, allowing the actuator to accelerate the wire downward . Once the desired displacement is achieved, the lower gripper may engage the wire and the top gripper may release it . The actuator may then retract in preparation for the next cycle . This configuration may be used with a stationary electrode , which can be configured to move in parallel with the wire .

[0160] In some embodiments , software may be used to control the drop formation and separation process by controlling the motion profile of the force generator . The software ( e . g . , using a G- and M- code file ) may precisely configure the energy, timing, and / or velocity imparted by the force generator to achieve consistent and repeatable drop separation events . The software may coordinate with various hardware components to achieve precise drop separation events .

[0161] In some embodiments , the system can introduce a coasting or braking phase during melting by physically decoupl ing the printhead from the force generator . This may allow the molten droplet to stabilize and center at the wire tip prior to separation, resulting in a more predictable and accurate droplet traj ectory .

[0162] FIG . 17 shows a system for forming metal droplets using a catch window in accordance with an embodiment . The system may include a spool 1700 , a wire feeder 1702 , a feedtube 1704 , a force generator 1706 , a catch window 1708 , an electrode 1710 , a linear bearing 1712 , and a build platform 1714 . The spool 1700 may supply feedstock wire that is fed by the wire feeder 1702 through the feedtube 1704 . The electrode 1710 may act as a heat source to melt the tip of the feedstock wire and generate metal droplets . The force generator 1706 may move the linear bearing 1712 ( and therefore the tip of the wire ) towards and / or away from the build platform 1714 . As shown, the force generator 1706 may be implemented as a voice coil . However, the force generator 1706 may include any suitable force generating component , such as a piezo actuator, a linear actuator, a magnetostrictive actuator, a hydraulic actuator, and / or a stepper motor .

[0163] The system may use the catch window 1708 to separate metal droplets from the feedstock wire . The force generator 1706 may reverse direction from a downstroke to an upstroke while temporarily disengaged from the linear bearing 1712 . The force generator 1706 may then re-engage with the upper portion of the catch window 1708 to create a tension-based separation event . This may avoid the use of a rigid hard stop, thereby reducing structural bending and mechanical shock during droplet separation .

[0164] The catch window 1708 may be implemented in a suitable manner . For example , the linear bearing 1712 may include at least one notch, ledge , and / or opening that physically engages with the force generator 1706 at a defined point . The catch window 1708 may be configured with compliant or damped interfaces , such as elastomeric pads or flexure hinges , to reduce shock and suppress vibration during engagement . In some examples , non-contact mechanisms may be used . For example, magnetic coupling can hold the force generator 1706 and linear bearing 1712 together and allow for passive separation under certain force or displacement thresholds . In some examples , the catch window 1708 may be configured with multiple catch points , allowing for variableposition engagement .

[0165] In some embodiments , the build platform may serve as the electrode . The build platform may arc with the wire after the wire is brought into close proximity to the build platform, generating a molten droplet . The droplet may separate through retraction of the wire , relying on surface tension rather than momentum change for droplet placement .

[0166] In some embodiments , the same wire feeder may be used for both the feedstock wire and the corresponding electrode wire . The wire feeder may retract the electrode wire at any suitable time after arcing ( e . g . , during or after droplet generation) . This may allow the system to adj ust the motion profile of the droplet to minimi ze drop traj ectory distance , minimi ze time of flight, and enable the precise placing of the droplets onto the build platform . FIG . 18 shows another system for forming metal droplets in accordance with an embodiment . As shown, the system may include a wire gripper 1800 positioned near the tip of the feedstock wire . The wire gripper 1800 may be used to control the position of the wire tip during droplet formation and separation . The wire gripper 1800 may mitigate the trans fer of mechanical vibrations through the wire , which could otherwise disturb the molten droplet and adversely af fect its traj ectory . The wire gripper 1800 may use any suitable actuation mechanism, such as passive spring clamping, piezoelectric clamping, electromagnetic clamping, and / or thermally actuated micro-clamping .

[0167] FIG . 19 shows another system for forming metal droplets in accordance with an embodiment . The system may include at least one bend in the feedtube 1704 . As shown, for example , the bend may include a circular loop . The bend may introduce friction between the wire and the feedtube 1704 , thereby stabili zing the position of the wire during drop separation . In some embodiments , the bend may be at a removable portion of the feedtube 1704 , allowing for reconfiguration of the feedtube 1704 .

[0168] In some embodiments , other methods for stabili zing the wire may be used . For example , the wire may be kept under constant or controlled tension using a spring-loaded spool , a weighted pulley, and / or a motori zed feedback loop . The tensioning system may be dynamically adj usted based on wire length, feed rate , and / or feedback from vibration sensors . In some examples , the wire may pass through a damped guide channel or low- friction sleeve . The interior surface of the guide or sleeve may be lined with viscoelastic materials , vibration-damping polymers , and / or microstructured surfaces designed to absorb lateral motion . Controlling Metal Droplet Properties

[0169] As described above, molten metal droplets may be formed to print a metal part. The properties of each individual droplet, such as temperature, size and velocity, can significantly impact the properties of the formed part. As such, precise control over droplet formation and deposition may be beneficial for ensuring consistent and high-quality manufacturing processes.

[0170] Accordingly, embodiments describe herein include systems and methods for controlling properties of metal droplets. A method may include setting at least one electrical parameter for an electrode, heating, using the electrode, the tip of the feedstock wire to form a metal droplet, and ejecting the metal droplet from the feedstock wire towards a build platform, the ejected metal droplet having at least one desired property based on the electrical parameter. In some embodiments, the electrical parameter may be set by a controller.

[0171] Droplet properties may depend on various factors related to the formation and separation of the droplets. For example, as described above, the feedstock may be melted through electrical arcing. The characteristics of the arc (e.g., intensity, duration, shape, etc.) may be controlled by adjusting electrical parameters such as current, number of arcs, pulse shape, inter-pulse delay, pulse frequency, voltage when the arc is first established, arcing time, and / or polarity. Such parameters may affect the energy imparted to the wire during electrical arcing.

[0172] Other factors affecting droplet properties may include the spatial configuration of the printhead, the feed rate of the feedstock, the position (e.g., orientation, proximity) of the feedstock tip relative to the electrode, and / or motion of the feedstock relative to the electrode during the formation of the metal droplet. In some embodiments, additional subsystems or actuators may further affect droplet properties, such as mechanical vibration mechanisms or flow shaping devices.

[0173] Accordingly, a printing system may be configured to adjust various parameters (e.g., on a per-droplet basis) to control droplet properties. The system may comprise and / or be otherwise coupled to a controller (and / or any other suitable component) configured to adjust the parameters. For example, the controller 5 shown in FIG. 1 may be configured to adjust parameters for the apparatus shown in FIG. 1. The controller may adjust electrical parameters for an electrode configured to melt feedstock to form metal droplets.

[0174] Adjusting the parameters may allow for real-time control of droplet properties such as size, temperature, velocity, drop path, and / or kinetic energy. Droplet properties may be selected based on the corresponding region in the printed part. For instance, outer perimeter regions of the part may be formed from smaller or cooler droplets to improve surface finish. Interior regions may be formed from hotter, larger droplets to promote bonding strength and reduce porosity. In some embodiments, droplets may be cooled intentionally to create weaker metallurgical bonds, such as in support structures intended for easy removal. For example, weakly bonded interface layers for support structures may be formed using cooler metal droplets. Control over droplet properties may also be used to print complex geometries, such as overhangs or thin features, by adjusting adhesion and wetting behaviors at the impact site . In some embodiments , multi-stage arcing sequences may be used for dif ferent phases of droplet formation and separation . For example , a first arc pulse may preheat the wire and partially melt the tip, and a second pulse with higher energy may finali ze melting and promote separation . In some examples , an additional pulse may be used to adj ust the drop path .

[0175] In some embodiments , superheated droplets may be formed, where the droplets are heated above their melting point but remain below the boiling point . Such droplets may carry excess thermal energy that can be transferred to the substrate during deposition . This may promote local melting or sintering at the interface and thus improve bonding between the droplet and the substrate . The degree of superheating may also be varied based on the temperature of the substrate .

[0176] In some embodiments , additional thermal energy may be imparted to the droplet using secondary heating mechanisms after the droplet has separated from the feedstock . For example , a plasma arc or heating field may be positioned in the drop path of the droplet, such that the droplet traverses the arc and absorbs further thermal energy prior to impact . In some examples , a droplet may pass between a pair of electrodes that establish an arc across the drop path, allowing the droplet to bridge the arc and acquire additional energy . In some examples , focused radiation sources such as lasers or high-intensity lamps may be used to provide additional energy to droplets . The energy trans fer may be controlled by adj usting electrical parameters . The energy transfer may allow the droplet to maintain and / or raise its temperature while in-flight . In some embodiments , the landing spot at the substrate may undergo locali zed heating, such as by using lasers , resistive heating elements , arc discharges , and / or other heat sources . This may promote metallurgical bonding, particularly when the substrate temperature would otherwise be insuf ficient to promote fusion .

[0177] In some embodiments , the arc polarity may be adj usted to control the shape and stability of the plasma arc . This may influence the melting of the feedstock and optionally clean the feedstock surface of oxides and / or contaminants before droplet formation begins .

[0178] In some embodiments , the arc parameters and timing may be adj usted to form self-separating droplets . The droplet may be formed and detached through controlled surface tension . By tuning the arc parameters and timing, the droplet may be induced to detach from the feedstock without requiring high momentum change . Thi s may reduce stress on the printhead and improve droplet traj ectory . In some embodiments , the sel f-separation may be controlled by adj usting mechanical parameters , such as the orientation of the printhead an / or feedstock, feedstock tension, and / or damping control .

[0179] In some embodiments , the incidence angle between the ej ected droplet and the build platform may be adj usted to af fect droplet properties . For example , the printhead and / or build platform may be mounted on a multi-axis motion system that enables dynamic adj ustment of angular orientation during printing . Controlling the incidence angle may encourage directional flow of the molten material across the substrate surface . In some embodiments , the incidence angle may be selected to smooth out ridges or eliminate surface discontinuities by directing molten flow into nearby valleys or crevasses.

[0180] In some embodiments, a controlled force (e.g., an oscillation or tilt) may be applied to the printhead during droplet formation and / or separation. The force may affect the drop path, such as by influencing the angle at which the droplet separates from the wire. The controlled force may be applied for printing onto angled surfaces or overhang regions.

[0181] In some embodiments, electromagnetic or electrostatic fields may be used to control the drop path while the droplet is inflight. For example, charged electrodes or magnetic coils may be placed near the drop path to deflect or stabilize the metal droplet. The polarity and strength of the applied field may be adjusted based on droplet mass, weight, velocity, and / or shape.

[0182] In some embodiments, gas jets or pulsed airflows may be used to control the drop path while the droplet is in-flight. For example, controlled bursts of air or inert gas may alter the drop path and / or apply braking force to adjust the velocity of the metal droplet .

[0183] In some embodiments, at least one parameter may be dynamically adjusted based on feedback received during droplet formation and / or separation. For example, a sensor may determine at least one droplet property of a separate droplet. If the property is outside an acceptable range, at least one parameter may be adjusted, such as the arc duration or the current. Sensors such as high-speed cameras, thermal sensors, and / or photodiodes may be used to monitor droplets and determine droplet properties in real time . In some embodiments , a machine learning model may be configured to predict droplet properties based on input parameters . For example , the model may predict the traj ectory of a droplet based on selected parameters . In some embodiments , the model may be configured to output a set of recommended parameters based on a given feedstock material and / or desired droplet properties . The model may be trained on historical print data .

[0184] FIG . 20 shows a flowchart of a method for forming metal droplets in accordance with one embodiment . While FIG . 20 shows illustrative operations according to one embodiment , other embodiments may omit , add to , reorder, and / or modify any of the operations shown in FIG . 20 . Moreover, each of the operations depicted in FIG . 20 may be performed in any of the ways described herein . The operations shown in FIG . 20 may be performed by any of the illustrative systems described herein, such as the apparatus shown in FIG . 1 .

[0185] Operation 2000 may include setting at least one electrical parameter for an electrode . The electrical parameter may be set by a controller, such as the controller 5 shown in FIG . 1 .

[0186] Operation 2002 may include heating, using the electrode , the tip of the feedstock wire to form a metal droplet .

[0187] Operation 2004 may include ej ecting the metal droplet from the feedstock wire towards a build platform . The ej ected metal droplet may have at least one desired property based on the electrical parameter, such as any of the properties described herein . The present disclosure is not to be limited in scope by the specific embodiments described herein . Indeed, other various embodiments of and modi fications to the present disclosure , in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings . Thus , such other embodiments and modifications are intended to fall within the scope of the present disclosure . Furthermore , although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose , those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes . Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein .

Claims

What is claimed is :1 . A system for forming molten metal droplets on demand, the system comprising : a plurality of printheads arranged in a parallel fashion; and at least one wire feeder configured to control the delivery of a plurality of feedstock wires along a feed path, wherein each printhead is configured to heat the tips of at least one feedstock wire past its melting points such that metal droplets are formed .2 . The system of claim 1 wherein at least two of the printheads are at least one of electrically independent or mechanically independent .3 . The system of claim 1 wherein at least two of the printheads share a single wire feeder .4 . The system of claim 1 wherein at least two of the printheads are configured to form metal droplets from dif ferent feedstock wires .5 . The system of claim 1 wherein the tip of at least one feedstock wire is heated using an electric arc .6 . The system of claim 1 wherein the tip of at least one feedstock wire is heated using an adj acent feedstock wire as an electrode .7 . The system of claim 1 wherein the printheads are arranged as a plurality of parallel arrays .

8. The system of claim 7 wherein at least one array is configured to form metal droplets while at least one additional array is retracting .

9. The system of claim 1 wherein the resolution of the printheads corresponds to the resolution of a build platform for receiving the metal droplets.

10. The system of claim 1 wherein the printheads are configured to construct a three-dimensional part using a print seguence based on the spatial arrangement of the printheads.

11. The system of claim 10 wherein the print seguence includes parallel scanning paths and a timed sequence for the printheads based on the spatial arrangement including an array.

12. The system of claim 10 wherein the print sequence is encoded in a G-code and M-code file.

13. A method for forming molten metal droplets on demand, the method comprising: obtaining a plurality of feedstock wires at a plurality of printheads arranged in a parallel fashion; delivering, using at least one wire feeder, at least one feedstock wire along a feed path; and heating the tip of the at least one feedstock wire past its melting point such that a metal droplet is formed.

14. The method of claim 13 wherein at least two of the printheads are at least one of electrically independent or mechanically independent .15 . The method of claim 13 wherein the tip of at least one feedstock wire is heated using an electric arc .16 . The method of claim 13 wherein the printheads are arranged as a plurality of parallel arrays .17 . The method of claim 16 wherein at least one array is configured to form metal droplets while at least one additional array is retracting .18 . The method of claim 13 wherein the resolution of the printheads corresponds to the resolution of a build platform for receiving the metal droplets .19 . The method of claim 13 further comprising : generating a print sequence based on the spatial arrangement of the printheads ; and constructing a three-dimensional part using the formed metal droplets based on the print sequence .20 . The method of claim 19 wherein the print sequence is encoded in a G-code and M-code file .21 . A system for forming metal droplets from a feedstock wire , the system comprising : a wire feeder configured to deliver a feedstock wire along a feed path; a heat source configured to heat the tip of the feedstock wire past its melting point such that a metal droplet is formed; and a movable carriage mechanically coupled to a force generator .22 . The system of claim 21 wherein the force generator comprises a linear actuator that is configured to accelerate the movable carriage to ej ect the metal droplet from the feedstock wire .23 . The system of claim 21 wherein the heat source comprises an electrode mechanically coupled to the movable carriage .24 . The system of claim 22 wherein the linear actuator is configured to detach from the movable carriage after the metal droplet is formed .25 . The system of claim 21 wherein the force generator comprises a piezoelectric actuator .26 . The system of claim 22 wherein the linear actuator is configured to : advance the movable carriage towards a build platform while being coupled with the movable carriage; change direction while being detached from the movable carriage ; and recouple with the movable carriage to ej ect the droplet from the feedstock wire .27 . The system of claim 21 wherein the wire feeder is configured to accelerate the feedstock wire while the movable carriage is stationary .28 . The system of claim 21 wherein the wire feeder is configured to change direction to ej ect the metal droplet from the feedstock wire .29 . The system of claim 21 wherein the wire feeder comprises a roller-based feeder .30 . The system of claim 21 wherein the wire feeder comprises a first gripper, a second gripper, and a second linear actuator .31 . The system of claim 30 wherein the second linear actuator is configured to : deliver the feedstock wire towards a build platform while the first gripper grips the feedstock wire ; and deliver the feedstock wire away from the build platform while the second gripper grips the feedstock wire .32 . The system of claim 21 wherein the heat source comprises a build platform .33 . The system of claim 21 wherein the heat source comprises an electrode wire mechanically coupled to the wire feeder .34 . The system of claim 21 wherein the feed path comprises a bend .35 . The system of claim 21 further comprising a gripper configured to control the position of the feedstock wire after the metal droplet is formed .36 . A system for forming metal droplets from a feedstock wire , the system comprising : a wire feeder configured to deliver a feedstock wire along a feed path; and an electrode configured to heat the tip of the feedstock wire past its melting point such that a metal droplet is formed .

37. The system of claim 36 further comprising a gripper to grip the feedstock wire after the feedstock wire is accelerated to eject the metal droplet from the feedstock wire.

38. The system of claim 36 wherein the wire feeder is configured to : accelerate the feedstock wire; and change direction to eject the metal droplet from the feedstock wire .

39. The system of claim 36 wherein the wire feeder comprises a roller-based feeder.

40. The system of claim 36 wherein the wire feeder comprises a first gripper, a second gripper, and a linear actuator.

41. A method for forming metal droplets from a feedstock wire, the method comprising: setting at least one electrical parameter for an electrode; and heating, using the electrode, the tip of the feedstock wire to form a metal droplet; and ejecting the metal droplet from the feedstock wire towards a build platform, the ejected metal droplet having at least one desired property based on the electrical parameter.

42. The method of claim 41 wherein the electrical parameter comprises at least one of a polarity, an arc time, a voltage level, a current level, or a number of arcs.

43. The method of claim 41 further comprising setting at least one physical configuration parameter for the feedstock wire,wherein the desired property is further based on the physical configuration parameter .44 . The method of claim 43 wherein the physical configuration parameter comprises at least one of a position of the feedstock wire relative to the electrode or motion of the feedstock wire relative to the electrode during the formation of the metal droplet .45 . The method of claim 41 wherein the desired property comprises at least one of a desired temperature, a desired velocity, or a desired size .46 . The method of claim 41 wherein the electrode comprises the build platform .47 . The method of claim 41 further comprising heating the ej ected metal droplet using a secondary heat source .48 . The method of claim 47 wherein the heating of the ej ected metal droplet comprises generating a plasma arc in a drop path of the metal droplet using the secondary heat source .49 . The method of claim 47 further comprising heating a landing spot at a substrate at the time of impact using the secondary heat source .50 . The method of claim 41 further comprising forming a weakly bonded interface layer for a support structure using the ej ected metal droplet .51 . A system for forming metal droplets from a feedstock wire , the system comprising : an electrode configured to heat the tip of the feedstock wire past its melting point such that a metal droplet is formed and ej ected from the feedstock wire towards a build platform; and a controller configured to set at least one electrical parameter for the electrode , the ej ected metal droplet having a desired property based on the electrical parameter .52 . The system of claim 51 wherein the electrical parameter comprises at least one of a polarity, an arc time, a voltage level , a current level , or a number of arcs .53 . The system of claim 51 wherein the controller is configured to set at least one physical configuration parameter for the feedstock wire .54 . The system of claim 53 wherein the physical configuration parameter comprises at least one of a position of the tip of the feedstock wire relative to the electrode or motion of the feedstock wire relative to the electrode during the formation of the metal droplet .55 . The system of claim 51 wherein the desired property comprises at least one of a desired temperature, a desired velocity, or a desired size .56 . The system of claim 51 wherein the electrode comprises the build platform .57 . The system of claim 51 further comprising a secondary heat source configured to heat the ej ected metal droplet .58 . The system of claim 57 wherein the heating of the ej ected metal droplet comprises generating a plasma arc in a drop path of the metal droplet using the secondary heat source .59 . The system of claim 57 wherein the secondary heat source is further configured to heat a landing spot at a substrate at the time of impact . 60 . The system of claim 51 wherein the ej ected metal droplet is used to form a weakly bonded interface layer for a support structure .

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