Dual-wire welding or additive manufacturing systems and methods

Abstract

The present invention provides a dual-wire welding or additive manufacturing system and method. [Solution] The welding or additive manufacturing system includes a power supply having a controller that controls the operation of the power supply. The power supply provides a current waveform to a contact tip assembly having a first hole terminating at a first exit orifice and a second hole terminating at a second exit orifice. The first exit orifice is configured to deliver a first wire electrode, and the second exit orifice is configured to deliver a second wire electrode. The exit orifices are separated from each other by a distance configured to prevent the solid portion of the first wire electrode delivered through the first hole from coming into contact with the solid portion of the second wire electrode delivered through the second hole, while promoting the formation of bridge droplets between the wire electrodes during a deposition operation in which the current waveform is simultaneously guided through the contact tip assembly to both wire electrodes.

Description

Technical Field

[0001] Devices, systems, and methods consistent with the present invention relate to material deposition with a dual wire configuration.

Background Art

[0002] When welding, it is often desirable to increase the width of the weld bead or the length of the welding puddle. There can be many different reasons for this desire, which is well known in the welding industry. For example, it may be desirable to extend the welding puddle in order to keep the weld and filler metal in a molten state for a long time to reduce porosity. That is, if the welding puddle is in a molten state for a long time, there is more time for harmful gases to escape from the weld bead before the bead solidifies. Additionally, it may be desirable to increase the width of the weld bead to cover a wider welding gap or to increase the wire deposition rate. In either case, it is common to use an increased electrode diameter. The increased diameter will result in a long and expanded welding puddle, even if it may only be desirable to increase the width or length (but not both) of the welding puddle. However, this comes with drawbacks. Specifically, since a larger electrode is employed, more energy is required in the welding arc to facilitate proper welding. This increase in energy causes an increase in the heat input into the weld and results in more energy being used in the welding operation due to the larger diameter of the electrode being used. Further, it may produce a weld bead profile or cross-section that is not ideal for some mechanical applications. Instead of increasing the diameter of the electrode, it may be desirable to use at least two smaller electrodes simultaneously.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The following summary provides a simplified overview to give a basic understanding of some aspects of the apparatus, systems, and / or methods discussed herein. This summary is not a comprehensive overview of the apparatus, systems, and / or methods discussed herein. This summary is not intended to identify or describe the scope of the most important elements of such apparatus, systems, and / or methods. Its entire purpose is to present some concepts in a simplified form as a prelude to the more detailed explanations that will be presented later.

[0005] According to one aspect of the present invention, a welding or additive manufacturing system is provided. The system includes a power supply including a controller that controls the operation of the power supply. The power supply provides a current waveform to a contact tip assembly having a first hole terminating at a first exit orifice and a second hole terminating at a second exit orifice. The first exit orifice is configured to deliver a first wire electrode, and the second exit orifice is configured to deliver a second wire electrode. The first and second exit orifices are separated from each other by a distance configured to facilitate the formation of bridge droplets between the first wire electrode delivered at the first hole and the second wire electrode delivered at the second hole, while preventing the solid portion of the first wire electrode delivered at the first hole from coming into contact with the solid portion of the second wire electrode delivered at the second hole during a deposition operation in which the current waveform is simultaneously delivered at both the first and second wire electrodes through the contact tip assembly.

[0006] According to another aspect of the present invention, a welding or additive manufacturing system is provided. The system includes a power supply, which includes a controller for controlling the operation of the power supply. The power supply provides a current waveform to a contact tip assembly having a first hole terminating at a first exit orifice and a second hole terminating at a second exit orifice. A first wire feeder delivers a first wire electrode through the first exit orifice, and a second wire feeder delivers a second wire electrode through the second exit orifice. The first and second exit orifices are separated from each other by a distance configured to facilitate the formation of bridge droplets between the first wire electrode delivered through the first hole and the second wire electrode delivered through the second hole, while preventing the solid portion of the first wire electrode delivered through the first hole from coming into contact with the solid portion of the second wire electrode delivered through the second hole during a deposition operation in which the current waveform is simultaneously delivered to both the first and second wire electrodes through the contact tip assembly.

[0007] According to another aspect of the present invention, a welding or additive manufacturing system is provided. The system includes a power supply including a controller that controls the operation of the power supply. The power supply provides a current waveform to a contact tip assembly having a first hole terminating at a first exit orifice and a second hole terminating at a second exit orifice. The first exit orifice is configured to deliver a first wire electrode, and the second exit orifice is configured to deliver a second wire electrode. The system further includes at least one wire feeder, the at least one wire feeder driving a first wire electrode through a first hole and a second wire electrode through a second hole. The first and second outlet orifices are separated from each other by a distance configured to prevent the solid portion of the first wire electrode delivered through the first hole from coming into contact with the solid portion of the second wire electrode delivered through the second hole during a deposition operation in which the current waveform is simultaneously guided through the contact tip assembly to both the first and second wire electrodes, while facilitating the formation of bridge droplets between the first wire electrode delivered through the first hole and the second wire electrode delivered through the second hole.

[0008] The above and / or other aspects of the present invention will become apparent by describing in detail exemplary embodiments of the invention with reference to the accompanying drawings. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram shows an exemplary embodiment of the welding system of the present invention. [Figure 2] A diagrammatic representation of an exemplary contact tip assembly in one embodiment of the present invention is shown. [Figure 3A-3D] This diagram shows a welding operation in one exemplary embodiment of the present invention. [Figure 4A-4B] Diagrams illustrating current and magnetic field interactions in some exemplary embodiments of the present invention are shown. [Figure 5A] This diagram shows an exemplary weld bead made with a single wire according to one embodiment of the present invention. [Figure 5B] This shows a diagrammatic representation of an exemplary weld bead according to one embodiment of the present invention. [Figure 6] This diagram shows an illustrative welding process flowchart of one embodiment of the present invention. [Figure 7] A diagrammatic representation of an alternative embodiment of the contact tip assembly used in conjunction with some embodiments of the present invention is shown. [Figure 8] The diagrams shown illustrate the welding current waveforms of several embodiments of the present invention. [Figure 9] The diagrams shown here illustrate another exemplary welding current waveform in some embodiments of the present invention. [Figure 10] The diagrams below show additional exemplary welding current waveforms of several embodiments of the present invention. [Figure 11] A portion of a welding torch is shown. [Figure 12] This is a perspective view of the contact tip and diffuser. [Figure 13] This is a perspective view of a contact tip. [Figure 14] It is a perspective view of a contact chip. [Figure 15] It is a perspective view of a diffuser. [Figure 16] It is a perspective view of a diffuser. [Figure 17] It is a perspective view of another exemplary contact chip. [Figure 18] It is a perspective view of an exemplary drive roll. [Figure 19] It shows a cross-section of a drive roll for supplying dual wires. [Figure 20] It shows a diagrammatic representation of an exemplary embodiment of the welding system of the present invention. [Figure 21] It shows a diagrammatic representation of an exemplary embodiment of the welding system of the present invention. [Figure 22] It shows an additive manufacturing deposition operation. [Figure 23] It shows an additive manufacturing deposition operation. [Figure 24] It shows an additively manufactured part. [Figure 25] It shows an exemplary deposition operation.

MODE FOR CARRYING OUT THE INVENTION

[0010] Next, exemplary embodiments of the present invention will be described below by referring to the accompanying drawings. The described exemplary embodiments are intended to assist in the understanding of the present invention and are not intended to limit the scope of the present invention in any way. Like reference numerals refer to like elements throughout the specification.

[0011] As used herein, “at least one,” “one or more,” and “and / or” are open-ended expressions that are both conjunctions and disjunctions in action. For example, each of the expressions “at least one of A, B, and C,” “at least one of A, B, or C,” “one or more of A, B, and C,” and “A, B, and / or C” means A only, B only, C only, A and B together, A and C together, B and C together, or A, B, and C together. Any disjunction or disjunction that presents two or more alternative terms should be understood to take into account the possibility of including one of the terms, either of the terms, or both of the terms, whether in embodiments, claims, or accompanying drawings. For example, the phrase “A or B” should be understood to include the possibility of “A” or “B” or “A and B.”

[0012] While some embodiments of the present invention discussed herein are described in the context of GMAW type welding, other embodiments of the present invention are not limited thereto. For example, some embodiments may be used in SAW and FCAW type welding operations and other similar types of welding operations. Furthermore, while the electrodes described herein are solid electrodes, again, some embodiments of the present invention are not limited to the use of solid electrodes, as core electrodes (either flux cores or metal cores) may also be used without departing from the spirit or scope of the present invention. Moreover, some embodiments of the present invention may also be used in manual, semi-automatic, and robotic welding operations. Such systems are well known and will not be described in detail herein.

[0013] Now moving on to the attached drawings, Figure 1 depicts an exemplary embodiment of a welding system 100 according to one exemplary embodiment of the present invention. The welding system 100 includes an arc generating power source, such as a welding power source 109, which is coupled to a welding torch 111 (having a contact tip assembly (not shown)) via a wire feeder 105. The power source 109 may be a known type of welding power source capable of delivering current and welding waveforms, such as pulse spray, STT and / or short arc type welding waveforms, to the torch 111. The construction, design and operation of such a power source are well known and therefore do not need to be described in detail in the specification. The power source 109 outputs welding waveforms simultaneously to wire electrodes E1 and E2 during dual-wire welding operations via a contact tip assembly in the welding torch 111. The power source 109 may include a controller 120 coupled to a user interface to allow the user to control the welding operation or input welding parameters. The controller 120 may have a processor, CPU, memory, etc., used to control the operation of the welding process as described herein. The torch 111, which can be constructed similarly to known manual, semi-automatic, or robotic welding torches, can be coupled to any known or used welding gun and may be of a straight or gooseneck type. The wire feeder 105 draws electrodes E1 and E2, respectively, from electrode sources 101 and 103, which may be of any known type such as reels, spools, or containers. The wire feeder 105 is of a known construction and employs a drive roll 107 to draw electrodes E1 and E2 and push these electrodes to the torch 111. In one exemplary embodiment of the present invention, the drive roll 107 and wire feeder 105 are configured for single-electrode operation. Some embodiments of the present invention using a dual-wire configuration may be utilized with a wire feeder 105 and drive roll 107 designed solely for single-wire supply operation. For example, the drive roll 107 may be configured for a single 0.045-inch (1.14 mm) diameter electrode, and will suitably drive two 0.030-inch (0.76 mm) diameter electrodes without modification to the wire feeder 105 or the drive roll 107.Alternatively, the wire feeder 105 may be designed to provide a separate set of rollers for supplying electrodes E1 / E2 respectively, or it may have a drive roll specifically configured to supply two or more electrodes simultaneously (e.g., via a trapezoidal wire accommodating groove around a roller capable of accommodating two electrodes). In other embodiments, two separate wire feeders may also be used. As shown, the wire feeder 105 is in communication with a power supply 109 that conforms to a known configuration of a welding operation.

[0014] Driven by the drive roll 107, electrodes E1 and E2 are passed through the liner 113 to deliver them to the torch 111. The liner 113 is appropriately dimensioned to allow the electrodes E1 and E2 to pass to the torch 111. For example, for two 0.030-inch (0.76 mm) diameter electrodes, a standard 0.0625-inch (1.59 mm) diameter liner 113 (typically used for a single 0.0625-inch (1.59 mm) diameter electrode) can be used without modification.

[0015] While the example referenced above discusses the use of two electrodes of the same diameter, the present invention is not limited in this respect, as several embodiments may use electrodes of different diameters. That is, some embodiments of the present invention may use a first larger diameter electrode and a second smaller diameter electrode. Such embodiments allow for more convenient welding of two workpieces of different thicknesses. For example, the larger electrode may be directed towards a larger workpiece, while the smaller electrode may be directed towards a smaller workpiece. Furthermore, some embodiments of the present invention may be used in many different types of welding operations, including, but not limited to, metal-inert gas, submerged arc, and flux core welding. Additionally, some embodiments of the present invention may be used in automatic, robotic, and semi-automatic welding operations. Moreover, some embodiments of the present invention may be used with various electrode types. For example, a core electrode may be coupled with a non-core electrode. Furthermore, electrodes of various compositions may be used to achieve the desired welding characteristics and composition of the final weld bead. Thus, some embodiments of the present invention may be used in a wide range of welding operations.

[0016] Figure 2 illustrates an exemplary contact tip assembly 200 of the present invention. The contact tip assembly 200 may be fabricated from known contact tip materials and may be used in any known type of welding gun. As shown in this exemplary embodiment, the contact tip assembly has two separate channels 201, 203 running in the longitudinal direction of the contact tip assembly 200. During welding, the first electrode E1 passes through the first channel 201 and the second electrode E2 passes through the second channel 203. Channels 201 / 203 are typically appropriately sized for the diameter of the wire being passed through. For example, if the electrodes have the same diameter, the channels will have the same diameter. However, if different diameters are used, the channels should be appropriately sized to correctly transfer current to the electrodes. In addition, in the shown embodiment, channels 201 / 203 are configured so that electrodes E1 / E2 exit in parallel from the far end face of the contact tip 200. However, in other exemplary embodiments, the channel may be configured such that electrodes E1 / E2 exit the far end face of the contact tip such that an angle within the range of + / -15° exists between the centerlines of the respective electrodes. This angle may be determined based on the desired performance characteristics of the welding operation. In some exemplary embodiments, the contact tip assembly may be a single, integrated contact tip with the channel as shown, but in other embodiments, the contact tip assembly may consist of two contact tip subassemblies positioned close to each other, with the current directed towards each of the contact tip subassemblies.

[0017] As shown in Figure 2, each electrode E1 / E2 is spaced apart by a distance S, which is the distance between the nearest ends of the electrodes. In some exemplary embodiments of the present invention, this distance is in the range of 0.25 to 4 times the diameter of the larger of the two electrodes E1 / E2, while in other exemplary embodiments, the distance S is in the range of 2 to 3 times the maximum diameter. For example, if each electrode has a diameter of 1 mm, the distance S may be in the range of 2 to 3 mm. In other exemplary embodiments, the distance S is in the range of 0.25 to 2.25 times the diameter of one of the wire electrodes (such as the larger of the two electrodes). In manual or semi-automatic welding operations, the distance S is in the range of 0.25 to 2.25 times the maximum electrode diameter, while in robotic welding operations, the distance S is within the same or a different range (such as 2.5 to 3.5 times the maximum electrode diameter). In exemplary embodiments, the distance S is in the range of 0.2 to 3.5 mm.

[0018] The wire electrodes E1 / E2 protrude from the exit orifice on the end face of the contact tip 200. The diameter of the exit orifice is slightly larger than the diameter of the wire electrodes E1 / E2. For example, for a 0.035 inch (0.85 mm) wire, the diameter of the exit orifice may be 0.043 inches (1.09 mm); for a 0.040 inch (1.02 mm) wire, the diameter of the exit orifice may be 0.046 inches (1.17 mm); and for a 0.045 inch (1.14 mm) wire, the diameter of the exit orifice may be 0.052 inches (1.32 mm). Channels 201, 203 and the exit orifice are appropriately spaced apart to facilitate the formation of a single bridge droplet between the wire electrodes E1 / E2 during the deposition process. For exit orifices sized for electrodes with a diameter of 0.045 inches (1.14 mm) or less, the distance between exit orifices (from inner circumference to inner circumference, as well as distance S) may be less than 3 mm to facilitate the formation of bridge droplets. However, depending on the wire size, magnetic force, orientation of channels 201 and 203 (e.g., angle), a spacing of 3 mm or more between exit orifices may be possible. In some embodiments, the distance between exit orifices is in the range of 20% to 200% of the diameter of one or both exit orifices, which may also correspond to the distance S between wire electrodes being in the range of 0.25 to 2.25 times the electrode diameter.

[0019] As will be further explained below, the distance S should be selected to ensure that a single bridge droplet is formed between electrodes E1 / E2 before the droplets are transferred to the molten paddle during the deposition process, while preventing the solid portions of electrodes E1 / E2 delivered through the channel and exit orifice from coming into contact with each other except through bridge droplets.

[0020] Figure 3A illustrates an exemplary embodiment of the present invention while showing the magnetic force interaction from the respective electrodes E1 and E2. As shown, due to the flow of current, a magnetic field is generated around the electrodes that tends to produce a pinch force that pulls the wires in opposite directions. This magnetic force tends to create a droplet bridge between the two electrodes, which will be discussed in more detail below.

[0021] Figure 3B shows a droplet bridge formed between two electrodes E1 / E2. That is, as the current flowing through each electrode melts the ends of the electrodes, the magnetic force tends to pull the molten droplets toward each other until they connect. The distance S is far enough to prevent the solid parts of the electrodes from being pulled toward contact during the deposition process, but close enough for a droplet bridge to form before the molten droplets are transferred to the welding paddle generated by the welding arc. Figure 3B shows that a large bridge droplet can form between electrodes E1 / E2, but a relatively small cross-sectional area exists between the droplet and the electrode. That is, the electrode contacts the bridge droplet along its small cross-sectional area. The droplet is further depicted in Figure 3C, where the droplet bridge generates a single large droplet that is transferred to the paddle during welding. As shown, the magnetic pinch force acting on the droplet bridge acts to pinch off the droplet, similar to the use of pinch force in single-electrode welding operations.

[0022] In some embodiments, bridge droplets are transferred to the molten paddle during a short event between the molten paddle and the wire electrodes E1 / E2. This process is known as short arc welding. The short event is depicted in Figure 3D. Electrodes E1 / E2 are driven toward the workpiece W by a wire feeder at a wire feed rate (WFS) sufficient to ensure that the bridge droplet does not detach (e.g., not pinch off from the electrode) before the droplet and electrode short to the molten paddle on the workpiece W. The force supplying electrodes E1 / E2 overcomes the heating of the arc, and when the bridge droplet contacts the molten paddle as shown, the large bridge droplet is pulled into the molten pool, and surface tension, along with a pinch force, transfers the droplet from the electrode to the molten pool. The size of the bridge droplet is significantly larger than that of droplets formed in conventional single-electrode short arc welding. This results in a deposition rate per short arc cycle that exceeds that of conventional short arc welding, but the cross-sectional area between the electrode and the droplet is relatively small, requiring less pinch force to transfer the droplet. After the bridge droplet shorts into the molten paddle, electrodes E1 / E2 may continue to be driven into the molten paddle for a short time while being resistively heated by the welding current. Sufficient heat will be present in the molten paddle, combined with the resistance heating, to melt electrodes E1 / E2 and allow them to be consumed into the molten pool as additional filler metal.

[0023] Figure 4A depicts an exemplary representation of the current flow of the present invention in one embodiment. As shown, the welding current is divided to flow through each of the respective electrodes, passing through and through them as a bridge droplet is formed. The current then passes from the bridge droplet to the paddle and workpiece. In the exemplary embodiment where the electrodes are of the same diameter and type, the current will be divided uniformly through the electrodes. In some embodiments where the electrodes have different resistance values, for example, due to different diameters and / or compositions / structures, the current will be distributed according to the relationship V=I*R. Once the welding current is applied to the contact tip as in known methodologies, the contact tip supplies the welding current to each electrode through contact between the electrode and the channel in the contact tip. Figure 4B depicts the magnetic force that assists in the formation of the bridge droplet. As shown, the magnetic force tends to pull the respective molten portions of the electrodes toward each other until they come into contact with each other.

[0024] Figure 5A depicts an exemplary cross-section of a weld made by a single-electrode welding operation. As shown, the weld bead WB is of adequate width, but the fingers F of the weld bead WB (penetrating into the workpiece W as shown) are relatively narrow. This can occur in single-wire welding operations when higher deposition rates are used. That is, in such welding operations, the fingers F can be so narrow that it is unreliable to assume that the fingers will penetrate in the desired direction, and therefore cannot be a reliable indicator of adequate penetration. Furthermore, if these narrow fingers penetrate deeper, this can lead to defects such as pores trapped near the fingers. In addition, in such welding operations, the useful side of the weld bead does not penetrate as deeply as desired. Therefore, in some applications, this mechanical bond is not as strong as desired. Moreover, in some welding applications such as horizontal fillet welding, the use of a single electrode has made it difficult to achieve a weld leg of equal size at high deposition rates without adding too much heat to the welding operation. These challenges are mitigated by several embodiments of the present invention, which can reduce finger penetration and widen the fingers to broaden lateral penetration of the weld. An example of this is shown in Figure 5B, which shows a weld bead according to one embodiment of the present invention. As shown in this embodiment, similar or improved weld bead leg symmetry and / or length, as well as a wider weld bead in terms of weld depth within the weld joint, can be achieved. This improved weld bead geometry is achieved using less total heat input into the weld. Thus, several embodiments of the present invention can provide improved mechanical welding performance with less heat input and an improved deposition rate.

[0025] Figure 6 illustrates a flowchart 600 of an exemplary welding operation of the present invention. This flowchart is intended to be illustrative and not limiting. As shown, a welding current / output is provided by the welding power supply so that the current is directed to contact tips and electrodes that conform to a known system construction (610). Exemplary waveforms are discussed further below. During welding, a bridge droplet is formed between the electrodes (620), with each droplet from each electrode coming into contact with each other to form a bridge droplet. The bridge droplet is formed before contact with the welding paddle. During the formation of the bridge droplet, at least one of the duration or droplet size is detected by the time the droplet reaches a size to be transferred and is then transferred to the paddle (640) (630). This process is repeated throughout the welding operation. To control the welding process, a power supply controller / control system may use either bridge droplet current duration and / or bridge droplet size detection to determine whether the bridge droplet is of a size to be transferred. For example, in one embodiment, a predetermined bridge current duration for a given welding operation is used so that the bridge current is maintained for that duration and then droplet transfer begins. In another exemplary embodiment, a power supply controller may monitor the welding current and / or voltage and utilize a predetermined threshold (e.g., a voltage threshold) for a given welding operation. For example, in such an embodiment, when a detected arc voltage (detected via a known type of arc voltage detection circuit) detects that the arc voltage has reached a bridge droplet threshold level, the power supply initiates the droplet separation section of the welding waveform. This is further discussed below in some exemplary embodiments of welding waveforms that may be used with some embodiments of the present invention.

[0026] Figure 7 depicts an alternative exemplary embodiment of the contact tip 700 that may be used with some embodiments of the present invention. As previously described, in some embodiments, the electrodes may be directed to the torch via a single wire guide / liner. Naturally, in other embodiments, separate wire guides / liners may be used. However, in these embodiments in which a single wire guide / liner is used, the contact tip may be designed so that the electrodes are separated from each other within the contact tip. As shown in Figure 7, this exemplary contact tip 700 has a single inlet channel 710 with a single orifice at the upstream end of the contact tip 700. Each electrode enters the contact tip through this orifice and travels along the channel 710 until it reaches the separation section 720 of the contact tip. The separation section directs the first electrode into the first outlet channel 711 and the second electrode into the second outlet channel 712 so that the electrodes are directed to their respective outlet orifices 701, 702, respectively. Naturally, channels 710, 711, and 712 should be appropriately sized for the size of the electrodes used, and the separation section 720 should be shaped so as not to damage or scratch the electrodes. As shown in Figure 7, the exit channels 711 and 712 are angled relative to each other, but as shown in Figure 2, these channels can also be oriented in parallel with each other.

[0027] Next, moving to Figures 8 to 10, various exemplary waveforms that may be used with exemplary embodiments of the present invention are depicted. Generally, in some exemplary embodiments of the present invention, the current is increased to generate a bridge droplet and build it for transfer. In exemplary embodiments, during transfer, the bridge droplet has an average diameter (which may be larger than the diameter of either electrode) similar to the distance S between the electrodes. Once formed, the droplet is transferred through a high peak current, and then the current is reduced to a lower (e.g., background) level to remove the arc pressure acting on the wire. The bridge current then builds the bridge droplet without exercising too large a pinch force and pinching off the growing droplet. In exemplary embodiments, this bridge current is at a level in the range of 30-70% between the background current and the peak current. In other exemplary embodiments, the bridge current is in the range of 40-60% between the background current and the peak current. For example, if the background current is 100 amperes and the peak current is 400 amperes, the bridge current is in the range of 220–280 amperes (i.e., 40–60% of the 300 ampere difference). In some embodiments, the bridge current may be maintained for a duration in the range of 1.5–8 ms, while in other exemplary embodiments, the bridge current is maintained for a duration in the range of 2–6 ms. In exemplary embodiments of the present invention, the bridge current duration begins at the end of the background current state and includes a bridging current ramp-up, the ramp-up may be in the range of 0.33–0.67 ms depending on the bridge current level and ramp rate. In exemplary embodiments of the present invention, the pulse frequency of the waveform may be slowed compared to a single-wire process to enable droplet growth, improve control compared to single-wire operation, and enable higher deposition rates.

[0028] Figure 8 depicts an exemplary current waveform 800 for pulsed spray welding type operation. As shown, the waveform 800 has a background current level 810, which then transitions to a bridge current level 820, during which time the bridge droplet is allowed to grow to a size to be transferred. The bridge current level is below the spray transfer current level 840, at which point the droplet begins its transfer to the paddle. At the end of the bridge current 820, the current rises above the spray transfer current level 840 to a peak current level 830. The peak current level is then maintained for a peak duration to allow the transfer of the droplet to be completed. After the transfer, the current drops back down to the background level as the process is repeated. Thus, in these embodiments, the transfer of a single droplet does not occur during the bridge current portion of the waveform. In such exemplary embodiments, the lower current level 820 of the bridge current allows the droplet to form without excessive pinching force to direct it towards the paddle. Due to the use of bridged droplets, welding operations can be achieved in which a peak current of 830 amps can be maintained for longer durations at higher levels than when using a single wire. For example, some embodiments can maintain a peak duration in the range of 4 to 7 ms at least 4 ms, with a peak current level in the range of 550 to 700 amps and a background current in the range of 150 to 400 amps. In such embodiments, significantly improved deposition rates can be achieved. For example, some embodiments have achieved deposition rates in the range of 19 to 26 lbs (8.6 to 11.8 kg) / hour, while a similar single-wire process can only achieve deposition rates in the range of 10 to 16 lbs (4.5 to 7.3 kg) / hour. For example, in one non-limiting embodiment, a pair of twin wires with a diameter of 0.040'' (1.02 mm) using a peak current of 700 amps, a background current of 180 amps, and a droplet bridge current of 340 amps can be deposited at a rate of 19 lbs (8.6 kg) / hour at a frequency of 120 Hz. Such deposition occurs at a much lower frequency than in conventional welding processes, and is therefore more stable.

[0029] Figure 9 depicts another exemplary waveform 900 that may be used in short-arc type welding operations. Again, the waveform 900 has a background section 910 that precedes a short-response section 920 configured to clear the short between the droplet and the paddle. During the short-response section 920, the current is increased to clear the short, and once the short is cleared, the current is reduced to a bridge current level 930, during which a bridge droplet is formed. Again, the bridge current level 930 is less than the peak current level of the short-response section 920. The bridge current level 930 is maintained for a bridge current duration that allows the bridge droplet to form and be directed towards the paddle. During droplet transfer, the current is reduced to a background level, which allows the droplet to advance until a short occurs. Once a short occurs, the short-response / bridge current waveform is repeated. It should be noted that in some embodiments of the present invention, it is the presence of bridge droplets that makes the welding process more stable. That is, in traditional welding processes using multiple wires, bridge droplets do not exist. In these processes, if one wire shorts out or comes into contact with the paddle, the arc voltage of the other electrodes will decrease and the arc will be extinguished. This does not occur in some embodiments of the invention where the bridge droplet is common to each of the wires.

[0030] Figure 10 depicts another exemplary waveform 1000, which is an STT (surface tension transfer) type waveform. Such waveforms are known and will not be described in detail herein. For further description of STT type waveforms, their structure, use and embodiments, Patent Document 1, filed April 5, 2012, is incorporated herein by reference in whole. Again, this waveform has a background level 1010 and a first peak level 1015 and a second peak level 1020, where the second peak level is reached after the short circuit between the droplet and the paddle is released. After the second peak current level 1020, the current is reduced to a bridge current level 1030, where a bridged droplet is formed, and then the current is reduced to a background level 1010 to allow the droplet to advance to the paddle until it contacts the paddle. In other embodiments, AC waveforms may be used, e.g., AC STT waveforms, pulsed waveforms, etc.

[0031] The waveforms in Figures 9 and 10 are exemplary waveforms for short-circuit or short-arc welding using bridged droplets. During the arc portion of these deposition operations, the WFS of the welding electrode is positive and relatively high to push the bridged droplets into the molten paddle before they detach from the electrode. However, during a short event, the WFS may be reduced to allow the pinch force from the current flow to separate the electrode from the molten paddle and to rebuild the arc from the electrode. In some embodiments, wire feeding may be stopped during a short event so that the WFS reaches zero. The feeding direction of the wire feeder may also be reversed during a short event to pull the electrode away from the molten paddle. In this case, the wire feeder drives the electrode into the molten paddle initially during the short event to add additional filler metal to the paddle, and then pulls the electrode away from the molten paddle to help rebuild the arc. Timing for decelerating, stopping, and / or reversing the electrode may be based on the detection of the occurrence of a short event. For example, the power supply may monitor the welding voltage and control the wire feeder to decelerate / stop / reverse the electrode when the welding voltage drops to a short-circuit level, or to decelerate / stop / reverse the electrode for a predetermined period after a short circuit occurs. The welding arc between the electrode and the molten paddle may be re-established while the wire feed is decelerated or stopped or the feed direction is reversed (away from the molten paddle). The wire feeder may then resume delivering the electrode towards the molten paddle after the short circuit is cleared and the arc is re-established. Changes to the WFS and direction may be coordinated with changes to the current level and the arc portion of the deposition work during the short circuit.

[0032] As discussed above, wire electrodes used in multi-wire deposition operations (e.g., welding, filler fabrication, wear-resistant processing) may be spaced apart by a distance S that promotes the formation of bridge droplets between wire electrodes. The size of the bridge droplets is determined by the spacing between wire electrodes and the spacing between exit orifices within the contact tip. The size of the bridge droplets determines the width of the electric arc present during deposition, and reducing the spacing between the exit orifice and the wire electrode narrows the arc width. Larger bridge droplets may be preferable for larger welds, while smaller bridge droplets may be preferable for smaller welds. The deposition rate is affected by the arc width, and the deposition rate for small gauge wires can be increased by reducing the spacing between the exit orifice and the wire electrode (e.g., from approximately 2 mm to 1 mm).

[0033] The maximum distance between the exit orifices and wire electrodes is reached when the magnetic force grown by the current waveform (e.g., at peak current levels) still allows for the formation of bridge droplets, and is exceeded when bridging is no longer possible. The minimum distance is the distance that separates the solid parts of the wire at the point of bridging. The magnetic force tends to attract the wire electrodes, and the wire is somewhat flexible. Therefore, the minimum distance between the exit orifices and wire electrodes will depend on the stiffness of the electrodes, which is influenced by parameters such as wire diameter and construction material.

[0034] Figure 11 depicts the end of an exemplary welding torch according to the present invention. Since the structure and operation of welding torches are generally known, details of such structure and operation will not be discussed in detail herein. As shown, the torch comprises several components and is used to deliver at least two wire electrodes and one shielding gas to a workpiece for welding or additive manufacturing work. The torch includes a diffuser 205 that assists in the proper delivery and dispersion of the shielding gas for welding work. Coupled downstream of the diffuser 205 is a contact tip 200 used to deliver welding current into at least two wire electrodes that can be simultaneously penetrated by the contact tip during welding. The contact tip 200 is configured to facilitate the formation of bridge droplets between the wire electrodes delivered through holes or channels within the contact tip. The bridge droplets couple the first wire electrode to the second wire electrode before contact with the molten paddle generated by the deposition work, as discussed above.

[0035] An insulator 206 is screwed onto the outside of the diffuser 205. The insulator 206 electrically isolates the nozzle 204 from the electrically active components inside the torch. The nozzle 204 directs the shielding gas from the diffuser 205 to the far end of the torch and the workpiece during welding.

[0036] Conventional contact tips have threads on the upstream or near end of the contact tip that screws into the diffuser. The contact tip and diffuser are connected by screwing the contact tip into the diffuser. Such a clamping system works well for single-wire welding. The welding wire can be screwed through the contact tip, which can then be rotated multiple times around the wire and screwed into the diffuser. However, when welding with multiple welding wires that pass through the contact tip simultaneously, such a clamping system will result in undesirable twisting of the welding wires. For example, if two welding wires pass through the contact tip, then screwing the contact tip onto the diffuser by multiple rotations requiring more than 360° will twist the welding wires, preventing them from passing through the contact tip.

[0037] The contact tip 200 in Figure 11 is attached to the diffuser 205 by rotating the contact tip by less than 360° (e.g., 270° (3 / 4 turn), 180° (1 / 2 turn), 90° (1 / 4 turn), less than 90°). The rotation of the contact tip 200 required to attach the contact tip to the diffuser 205 can be any angle as desired, preferably less than 360°, and is an angle such that the multiple wire electrodes passing through the contact tip are not excessively twisted during the installation of the contact tip. If the welding wire is excessively twisted during the installation of the contact tip, a wire supply problem may occur, and a "bird nesting" condition of the welding wire may develop.

[0038] Referring to Figures 11-16, the contact tip 200 is attached to the diffuser 205 by a quarter turn (clockwise in the case of the contact tip inside the diffuser). The contact tip 200 has a tapered shape to accommodate gripping with tools such as pliers and has a forward, or downstream, tip that includes a flat 215. The contact tip 200 has a generally cylindrical rear, or upstream, base end 208, but includes radially projecting tabs 210 that engage with slots 212 in the inner wall of the diffuser 205 to securely connect the contact tip to the diffuser. The rear portion 208 of the contact tip 200 is located inside the diffuser 205 when the contact tip is installed on the diffuser and acts as the mounting shank for the contact tip. It can be seen that the diameter of the rear portion 208 of the contact tip is smaller than the adjacent downstream portion, resulting in shoulders 211 that project radially from the cylindrical rear portion 208 of the contact tip. The shoulder portion 211 sits in contact with the terminal surface of the diffuser 205 when the contact tip 200 is placed on the diffuser.

[0039] The contact tip 200 may be fabricated from known contact tip materials and may be used in any known type of welding gun. The contact tip may include a conductor (such as copper) extending from its rear near end to its front far end. As shown in this exemplary embodiment, the contact tip 200 has two separate wire channels or holes 214, 216 running in the longitudinal direction of the contact tip. The channels 214 / 216 may extend between a wire inlet orifice on the near end face of the mounting shank 208 and a wire outlet orifice on the far end face of the contact tip. During welding, the first wire electrode is delivered through the first channel 214 and the second wire electrode is delivered through the second channel 216. The channels 214 / 216 are typically appropriately sized with respect to the diameter of the wire passing through them. For example, if the electrodes have the same diameter, the channels will have the same diameter. However, if various wire sizes are used together, the channels should be appropriately sized to correctly transfer current to electrodes of various sizes. In addition, in the shown embodiment, channels 214 / 216 are configured such that electrodes exit in parallel from the far end face of the contact tip 200. However, in other exemplary embodiments, the channels may be configured such that electrodes exit the far end face of the contact tip such that an angle within the range of + / -15° exists between the centerlines of each electrode. This angle may be determined based on the desired performance characteristics of the welding operation. The exemplary contact tip discussed herein is shown having two electrode holes. However, it should be understood that the contact tip may have three or more electrode holes (e.g., three or more holes).

[0040] The slot 212 within the inner wall of the diffuser 205 includes an axial section 218 and a helical section 220. The axial section 218 of the slot 212 extends to the downstream end surface of the diffuser 205, where the shoulder 211 of the contact tip 200 abuts and seats. After the welding electrode passes through the contact tip 200, the radially projecting tab 210 on the mounting shank 208 is inserted into the axial section 218 of the slot 212, and the contact tip is pushed into the diffuser 205. When the tab 210 reaches the helical section 220 of the slot, the contact tip 200 is rotated to move the tab to the end of the helical section. The helical section 220 has a slightly upstream pitch that pulls the contact tip 200 inward as the contact tip rotates, so that the shoulder 211 of the contact tip abuts and seats on the downstream end surface of the diffuser 205. The tab 210 on the mounting shank 208 may have a tapered end 217 that matches the pitch of the slots 212 in the diffuser 205 to help ensure a tight connection between the two parts. In the exemplary embodiment shown, the helical portion 220 of the slot 212 allows a quarter turn of the contact tip 200 to secure the contact tip to the diffuser 205. However, it should be understood that other angles of rotation (e.g., a quarter turn, i.e., greater than or less than 90°) are possible. For example, the helical portion 220 of the slot may extend less than 360° around the inner circumference of the inner chamber of the diffuser 205.

[0041] Figure 17 shows another exemplary contact tip 230. The contact tip 230 is similar to the contact tip shown in Figure 13. However, the wire exit orifices 232, 234 are not symmetrically positioned on the far end face 236 of the contact tip 230. Exit orifice 232 is approximately centered along the far end face 236 of the contact tip 230. The second exit orifice 234 is separated from the first exit orifice 232 by a distance configured to facilitate the formation of bridge droplets between wire electrodes delivered through the contact tip 230 as discussed above. The wire electrode delivered through the first exit orifice 232 (centered along the torch axis) can be used for contact sensing of the weld path and for through-arc seam tracking (TAST). The wire electrode delivered through the first exit orifice 232 can also be the primary electrode used when the welding system is configured for both single-wire and dual-wire work. In single-wire welding, the wire feeder delivers the wire electrode only through the first outlet orifice 232 for use during welding, whereas in dual-wire welding, the same wire feeder or a second wire feeder delivers the wire electrode through both outlet orifices 232 and 234. In single-wire welding, if the primary wire electrode runs out, the secondary wire electrode delivered through the second outlet orifice 234 can be used as a backup until the primary wire electrode is replenished.

[0042] Figure 18 shows an exemplary drive roll 107 used in a wire feeder in a dual-wire welding system. The drive roll 107 has a central hole. The inner surface of the hole may include a hole-shaped recess 131 for accommodating a projection on the drive mechanism (such as a drive gear) to transfer drive torque to the drive roll 107. The drive roll 107 includes one or more annular wire accommodating grooves 133, 135. The wire accommodating grooves 133, 135 are spaced axially along the outer circumference of the drive roll 107. The wire accommodating grooves 133, 135 are designed to accommodate two welding wires. Exemplary standard welding wire diameters used with the drive roll 107 include 0.030 inches (0.76 mm), 0.035 inches (0.85 mm), 0.040 inches (1.02 mm), 0.045 inches (1.14 mm), etc. The wire dwelling grooves 133, 135 may have the same width and depth as each other, or they may have different widths and depths to accommodate different sizes or combinations thereof of dual welding wires. If the wire dwelling grooves 133, 135 each have the same width and depth, the drive roll 107 can be reused by simply flipping the drive roll over and reinstalling it on the wire feeder if one groove is worn out. The wire dwelling grooves 133, 135 may be configured to drive two wires of the same diameter or two wires of different diameters simultaneously. The wire dwelling grooves 133, 135 may have a substantially trapezoidal shape with straight sidewalls, angled sidewalls, or inwardly tapered sidewalls and a flat base extending between the sidewalls. However, the wire dwelling grooves 133, 135 may have other shapes besides the trapezoidal shape (e.g., having a curved groove base). In some embodiments, the grooves 133, 135 may include a serrated surface treatment or other friction surface treatment to help grip the welding wire.

[0043] Figure 19 shows a partial cross-sectional view of two drive rolls 107 that will be mounted on a wire feeder for supplying dual welding wires during loading operations. The drive rolls 107 are biased together to supply clamping forces onto the first welding wire E1 and the second welding wire E2. Both welding wires E1 and E2 are positioned within the annular grooves of the upper and lower drive rolls 107. The biasing force applied to the drive rolls 107 clamps the welding wires E1 and E2 within the annular groove between the upper and lower side walls 150 forming the groove and the adjacent welding wire. The welding wires E1 and E2 are held stably through three contact points within the annular groove. This clamping system allows both wires to be fed into the wire feeder in a consistent manner. The two welding wires E1 and E2 support each other and pull each other through friction during feeding. The side walls 150 of the annular groove are angled to apply both vertical and horizontal clamping forces on the welding wires E1 and E2. The horizontal clamping force pushes the welding wires E1 and E2 together, bringing them into contact with each other. The welding wires E1 and E2 are clamped in the annular groove so as to be axially offset from both groove bases 152. That is, the welding wires E1 and E2 are fixed between each other and the angled sidewalls 150 of the groove such that a gap exists between each welding wire and the groove base 152. In one exemplary embodiment, the angle between the sidewalls 150 and the outer circumference of the drive roll 107 is approximately 150°, but other angles are possible and can be determined by sound technical judgment.

[0044] The wire clamping provided by the drive rolls 107 allows for some variability in the diameters of the welding wires E1 and E2 (e.g., due to manufacturing tolerances). Each welding wire E1 and E2 has its own dedicated annular groove within the drive rolls 107, and if one welding wire is slightly larger than the other, the smaller welding wire may not be properly clamped between the drive rolls. In such a situation, the larger welding wire will limit the radial displacement of the drive rolls 107 relative to each other, thereby preventing proper clamping of the smaller wire. This can lead to feeding problems for the smaller welding wire during wire feeding and the so-called bird's nest condition. The clamping system discussed above can accommodate wires of various sizes because the clamping system is self-adjusting. If one welding wire E1 is larger than the other welding wire E2, the contact point between the wires is axially shifted from its central position within the annular groove toward the smaller wire. Three contact points are maintained on each welding wire E1 and E2 by the groove sidewalls 150 and the adjacent welding wires.

[0045] Figure 20 depicts another exemplary embodiment of the welding system 100. Here, the wire feeder 105 has separate sets of drive rolls 107a, 107b for supplying electrodes E1 and E2, respectively. The wire feeder 105 can selectively drive one or both of electrodes E1 and E2 via a common torch 111 and a contact tip (not shown). Thus, the welding system 100 can operate in either a single-wire mode, where only one of the electrodes is supplied during welding, or a dual-wire mode, where both electrodes are supplied during welding. The wire feeder 105 may include separate drive motors for a set of drive rolls 107a, 107b to control their operation, each drive motor being individually activated and deactivated and operating at various wire supply speeds. Alternatively, the drive rolls 107a, 107b may be powered by a common motor, and each set of drive rolls may be controlled by a clutch device to activate / deactivate their wire supply. The drive rolls 107a and 107b can be operated at various speeds as needed so that the wire feeding speeds of electrodes E1 and E2 differ from each other during the deposition operation, for example, to control the composition of the weld metal. Figure 21 shows yet another exemplary embodiment of the welding system 100 having two separate wire feeders 105a and 105b. The system in Figure 21 can operate similarly to the system in Figure 20 in that either wire electrode E1 or E2 can be fed only one at a time during a single-wire deposition operation, or wire electrodes E1 and E2 can be fed together during a dual-wire deposition operation. In Figure 21, the liner 114 has a common conduit trunk and separate branches 115 and 116 extending to each wire feeder 105a and 105b for carrying wire electrodes E1 and E2 to the torch 111. The liner 114 can be considered a Y-liner due to its overall Y shape.

[0046] Figures 22 and 23 illustrate an exemplary deposition process that utilizes both single-wire and dual-wire deposition processes together. The exemplary deposition process could be an additive manufacturing process such as 3D printing using single-wire and dual-wire welding techniques. Figure 24 shows an exemplary final part 300 built layer by layer using single and dual-wire additive manufacturing processes. The part 300 has internal voids 310 and therefore internal and external boundary lines 320. Figures 22 and 23 show partial layers of the formed final part 300. These layers are formed by building “walls” 330 along the boundary lines 320. The spaces between the walls are then filled with metal to complete the layers. It is desirable that the walls 330 be formed with high precision using a fine-resolution deposition process. The spaces between the walls can be filled using a lower-resolution and preferably higher-speed deposition process. Single-wire deposition generally offers higher resolution (e.g., more precise placement of metal) than dual-wire deposition. However, dual-wire deposition has a higher deposition rate and is therefore faster than single-wire deposition. In the exemplary additive manufacturing process, walls 330 are formed using a single-wire deposition operation. After walls 330 are formed, the spaces between walls are filled using a dual-wire deposition operation that utilizes bridge droplets formed between wires as discussed above 340. Single electrodes 350 and dual electrodes 360 are shown in Figures 22 and 23, respectively. Layers of the final part 300 may be formed using a single welding system (e.g., the welding system shown in Figures 20 and 21) that can selectively supply either one or two welding electrodes to the torch. The power supply may control the operation of the wire feeder to supply one or two welding electrodes to the torch depending on whether finer resolution deposition is required or whether a higher deposition rate is desirable. For example, the power supply may be configured to selectively operate a first wire feeder and a second wire feeder to perform both single-wire deposition and dual-wire deposition operations. The power supply may also control the welding waveform supplied to the torch depending on whether single or dual-wire operations are occurring.

[0047] Wall construction is one exemplary situation in which single-wire fine-resolution deposition may be used. Single-wire deposition may also be used at times when a lower deposition rate or finer resolution is desired, such as when forming overhangs of a part. As an alternative to single-wire deposition, dual-wire short-circuit or short-arc deposition may be used along the boundary 320 of a part to form a wall 330. Short deposition applies less heat to the molten paddle than pulsed spraying processes, which can help limit the molten flow during deposition and improve the resolution of the structure.

[0048] Figure 25 illustrates an exemplary dual-wire deposition operation. The welding torch contact tip 200 and dual-wire electrodes E1 and E2 are schematically shown in Figure 25. During welding, the torch moves along a groove 400 (direction Y) that forms a weld joint between two workpieces W1 and W2. The torch can also be advanced in a weaving motion (direction X) during welding. The exit orifices of electrodes E1 and E2 and the contact tip 200 are oriented along the groove approximately perpendicular to the torch's travel direction Y and approximately parallel to the weaving direction X. The orientation of electrodes E1 and E2 causes the arc cone to widen more in the X direction than in the Y direction. When electrodes E1 and E2 are advanced in a weaving motion in the X direction, the larger arc cone helps maintain a fluid state in the molten area, reducing the risk of poor fusion during welding. Naturally, electrodes E1, E2 and the contact tip exit orifice can be oriented at any desired angle with respect to the running and weaving directions (for example, parallel to the running direction Y) or at an angle of 45 degrees with respect to the weaving and running directions.

[0049] The use of the embodiments described herein may provide significant improvements in stability, weld structure, and performance beyond known welding operations. However, in addition to welding operations, some embodiments may be used in additive manufacturing operations. In fact, the system 100 described above may be used in additive manufacturing operations as well as in welding operations. In exemplary embodiments, improved deposition rates can be achieved in additive manufacturing operations. For example, when using an STT type waveform in a single-wire additive process, using a 0.045'' (1.14 mm) wire may provide a deposition rate of about 5 lbs (2.3 kg) / hour before becoming unstable. However, in some embodiments of the present invention and when using two 0.040'' (1.02 mm) wires, a deposition rate of 7 lbs (3.2 kg) / hour may be achieved with stable transfer. Since additive manufacturing processes and systems are known, details of such processes and systems do not need to be described herein. In such processes, bridge currents, such as those described above, may be used in the additive manufacturing current waveform.

[0050] It should be noted that the exemplary embodiments are not limited to the use of waveforms discussed above and described herein, as other welding type waveforms may be used with some embodiments of the invention. For example, other embodiments may use variable polarity pulsed spray welding waveforms, AC waveforms, etc., without departing from the spirit and scope of the invention. For example, in the variable polarity embodiment, the bridging portion of the welding waveform may be negative polarity so that bridging droplets are generated while reducing the total heat input into the welding paddle. For example, when using an AC type waveform, the waveform may have a frequency of 60 to 200 Hz, alternating between positive and negative pulses to melt two wires and form bridging droplets between them. In another embodiment, the frequency may be in the range of 80 to 120 Hz.

[0051] As previously described, some embodiments of the present invention can be used with various types of consumables and combinations thereof, including flux core consumables. In fact, some embodiments of the present invention can provide more stable welding operations when using flux core electrodes. Specifically, the use of bridged droplets can help stabilize flux core droplets, which can tend to be unstable in single-wire welding operations. Furthermore, some embodiments of the present invention enable increased welding and arc stability at higher deposition rates. For example, in single-wire welding operations, at high currents and high deposition rates, the droplet transfer type can change from streaming spray to rotational spray, noticeably reducing the stability of the welding operation. However, in some exemplary embodiments of the present invention, bridged droplets stabilize the droplets and significantly improve arc and welding stability at high deposition rates (e.g., stability above 20 lbs (9.1 kg) / hour).

[0052] In addition, as shown above, consumables can be of various types and / or compositions that can optimize a given welding operation. That is, the use of two different, compatible consumables can be combined to produce a desired welded joint. For example, compatible consumables including wear-resistant processed wire, stainless steel wire, nickel alloys and steel wires of various compositions can be combined. As one specific example, mild steel wire can be combined with excess alloy wire to make a 309 stainless steel composition. This can be advantageous when a single consumable of the desired type does not have the desired welding properties. For example, some consumables for special welding provide the desired welding chemistry but are extremely difficult to use and do not provide a satisfactory weld. However, some embodiments of the present invention can enable the use of two consumables that are easier to weld when combined to produce the desired welding chemistry. Some embodiments of the present invention can be used to produce alloys / deposition chemicals that are otherwise not commercially available or otherwise very expensive to manufacture. Thus, two different consumables can be used to eliminate the need for expensive or unavailable consumables. Furthermore, some embodiments can be used to produce dilute alloys. For example, the first welding wire could be a common, inexpensive alloy, and the second welding wire could be a specialty wire. The desired deposition would be an average of the two wires, exceeding the costly specialty wire, and would be well mixed during the formation of the bridge droplet at the low average cost of the two wires. Furthermore, in some applications, the desired deposition could be achieved by mixing two standard alloy wires, which may be unattainable due to the lack of suitable consumable chemicals, and which would be mixed within the bridge droplet and deposited as a single droplet. Furthermore, in some applications, such as wear-resistant metal applications, the desired deposition could be a combination of tungsten carbide particles from one wire and chromium carbide particles from another wire. In yet another application, to deposit a mixture of two wires, a larger wire containing larger particles is mixed with a smaller wire containing fewer or smaller particles.Here, the expected contribution from each wire is proportional to the size of the wire, assuming the wire feeding rate is the same. In yet another example, the wire feeding rate of the wires is different to allow the resulting alloy to be modified based on the desired deposition, but the mixture of wires is still generated by the bridging droplets that form between the wires.

[0053] Although the present invention has been particularly shown and described by reference to its exemplary embodiments, the present invention is not limited to these embodiments. It will be understood by those skilled in the art that various modifications of form and detail can be made without departing from the spirit and scope of the invention as defined by the following claims. [Explanation of Symbols]

[0054] 100 welding systems 101 Electrode source 103 Electrode source 105 Wire Feeder 105a Wire Feeder 105b Wire feeder 107 Drive Roll 107a Drive Roll 107b Drive Roll 109 Power supply 111 Torch 113 Raina 120 controllers 131 Hole-shaped recess 133 Annular wire housing groove 135 Annular wire housing groove 150 side wall 152 Groove base 200 contact tips 201 Channels 203 channels 204 nozzles 205 Diffuser 206 Insulator 208 Mounting shank 210 Radial protruding tabs 211 Shoulder 212 slots 214 First Channel 215 Flat 216 Second Channel 217 Tapered end 218 Axial section 220 Spiral part 230 Contact Tips 232 Exit Orifice 234 Exit Orifice 236 Far end face 300 Final Parts 310 Internal void 320 Boundary 330 Wall 350 Single Electrode 360 Dual Electrode 400 grooves 600 flowchart 700 Contact Tips 701 Individual Exit Orifice 702 Individual Exit Orifice 710 channels 711 First Exit Channel 712 Second Exit Channel 720 Separation section 800 current waveform 810 Background current level 820 Bridge Current Level 830 Peak current level 840 Spray transfer current level 900 waveforms 910 Background section 920 Short Response 930 Bridge current level 1000 waveforms 1010 Background level 1015 First peak level 1020 Second peak level 1030 Bridge current level E1 electrode E2 electrode F finger S distance X direction Y direction W Workpiece W1 Workpiece W2 Workpiece WB welding bead

Claims

1. A welding or additive manufacturing system, A power supply including a controller for controlling the operation of the power supply, the power supply provides a current waveform to a contact tip assembly having a first hole terminating at a first exit orifice and a second hole terminating at a second exit orifice, the first hole being parallel to the second hole, the first exit orifice being configured to deliver a first wire electrode, the second exit orifice being configured to deliver a second wire electrode, and the current waveform having a frequency and including a bridge current section and a further current section having a different current level than the bridge current section, The aforementioned bridge current section includes a current lamp, The further current section is a background current section, and the current level of the background current section is lower than the current level of the bridge current section, or the further current section is a peak current section, and the current level of the peak current section is higher than the current level of the bridge current section. The first and second outlet orifices are separated from each other by a distance configured to prevent the solid portion of the first wire electrode delivered through the first hole from coming into contact with the solid portion of the second wire electrode delivered through the second hole during a deposition operation in which the current waveform is simultaneously guided through the contact tip assembly to both the first and second wire electrodes, while promoting the formation of a bridge droplet between the first wire electrode delivered through the first hole and the second wire electrode delivered through the second hole, the current due to the current waveform flows from the contact tip assembly to the bridge droplet through both the first and second wire electrodes, the current is split between the first and second wire electrodes, and the current flows from the bridge droplet to the workpiece during the deposition operation, A welding or additive manufacturing system in which the bridge droplet between the first wire electrode and the second wire electrode is formed between the bridge current portion of the current waveform.

2. A welding or adding manufacturing system according to claim 1, further comprising at least one wire feeder, wherein the at least one wire feeder is configured to drive one or both of the first wire electrode and the second wire electrode via the contact tip assembly.

3. The welding or additive manufacturing system according to claim 1, wherein the wire supply speed of the first wire electrode is different from the wire supply speed of the second wire electrode during the deposition operation.

4. The welding or additive manufacturing system according to claim 1, wherein the orientation of the first outlet orifice and the second outlet orifice is substantially perpendicular to the direction of travel of the contact tip assembly during the deposition process.

5. The welding or processing manufacturing system according to claim 1, wherein the first outlet orifice has a diameter, and the distance is in the range of 20% to 200% of the diameter.

6. The welding or processing manufacturing system according to claim 1, wherein the distance is the distance between the first wire electrode and the second wire electrode, which is within the range of 0.25 to 2.25 times the diameter of the first and second wire electrodes, and is measured between the nearest ends of the first and second wire electrodes.

7. The welding or processing manufacturing system according to claim 1, wherein the aforementioned distance is less than 3 mm.

8. A welding or additive manufacturing system, A power supply including a controller for controlling the operation of the power supply, which provides a current waveform to a contact tip assembly having a first hole terminating at a first exit orifice and a second hole terminating at a second exit orifice, wherein the first hole is parallel to the second hole, and the current waveform has a frequency and includes a bridge current section and a further current section having a different current level than the bridge current section, the bridge current section includes a current ramp, the further current section is a background current section, the current level of the background current section is lower than the current level of the bridge current section or the peak current section of the further current section, the current level of the peak current section is greater than the current level of the bridge current section; A first wire feeder for delivering the first wire electrode through the first outlet orifice; and A second wire feeder that delivers the second wire electrode through the second outlet orifice; Includes, The first and second outlet orifices are separated from each other by a distance configured to prevent the solid portion of the first wire electrode delivered through the first hole from coming into contact with the solid portion of the second wire electrode delivered through the second hole during a deposition operation in which the current waveform is simultaneously guided through the contact tip assembly to both the first and second wire electrodes, while promoting the formation of a bridge droplet between the first wire electrode delivered through the first hole and the second wire electrode delivered through the second hole, the current due to the current waveform flows from the contact tip assembly to the bridge droplet through both the first and second wire electrodes, the current is split between the first and second wire electrodes, and the current flows from the bridge droplet to the workpiece during the deposition operation, A welding or additive manufacturing system in which the bridge droplet between the first wire electrode and the second wire electrode is formed between the bridge current portion of the current waveform.

9. The welding or processing manufacturing system according to claim 8, wherein the wire supply speed of the first wire electrode is different from the wire supply speed of the second wire electrode.

10. The welding or additive manufacturing system according to claim 8, wherein the power supply is configured to selectively operate the first wire feeder and the second wire feeder to perform both single-wire loading and dual-wire loading operations.

11. The welding or adding manufacturing system according to claim 8, wherein the contact tip assembly includes a far end face, and the first exit orifice is substantially centered along the far end face.

12. The welding or processing manufacturing system according to claim 8, wherein the first outlet orifice has a diameter, and the distance is in the range of 20% to 200% of the diameter.

13. The welding or processing manufacturing system according to claim 8, wherein the distance is the distance between the first wire electrode and the second wire electrode, which is within the range of 0.25 to 2.25 times the diameter of the first and second wire electrodes, and is measured between the nearest ends of the first and second wire electrodes.

14. The welding or processing manufacturing system according to claim 8, wherein the aforementioned distance is less than 3 mm.

15. A welding or additive manufacturing system, A power supply including a controller for controlling the operation of the power supply, wherein the power supply provides a current waveform to a contact tip assembly having a first hole terminating at a first exit orifice and a second hole terminating at a second exit orifice, the first hole being parallel to the second hole, the first exit orifice being configured to deliver a first wire electrode, the second exit orifice being configured to deliver a second wire electrode, the current waveform having a frequency and including a bridge current section and a further current section having a different current level than the bridge current section, the bridge current section including a current ramp, the further current section being a background current section, the current level of the background current section being lower than the current level of the bridge current section or the peak current section of the further current section, the current level of the peak current section being greater than the current level of the bridge current section; and At least one wire feeder that drives the first wire electrode through the first hole and the second wire electrode through the second hole; Includes, The first and second outlet orifices are separated from each other by a distance configured to prevent the solid portion of the first wire electrode delivered through the first hole from coming into contact with the solid portion of the second wire electrode delivered through the second hole during a deposition operation in which the current waveform is simultaneously guided through the contact tip assembly to both the first and second wire electrodes, while promoting the formation of a bridge droplet between the first wire electrode delivered through the first hole and the second wire electrode delivered through the second hole, the current due to the current waveform flows from the contact tip assembly to the bridge droplet through both the first and second wire electrodes, the current is split between the first and second wire electrodes, and the current flows from the bridge droplet to the workpiece during the deposition operation, A welding or additive manufacturing system in which the bridge droplet between the first wire electrode and the second wire electrode is formed between the bridge current portion of the current waveform.

16. The welding or processing manufacturing system according to claim 15, wherein the wire supply speed of the first wire electrode is different from the wire supply speed of the second wire electrode.

17. The welding or additive manufacturing system according to claim 15, wherein the power supply is configured to control the at least one wire feeder to perform both single-wire loading and dual-wire loading operations.

18. The welding or adding manufacturing system according to claim 15, wherein the contact tip assembly includes a far end face, and the first exit orifice is substantially centered along the far end face.

19. The welding or additive manufacturing system according to claim 15, wherein the orientation of the first outlet orifice and the second outlet orifice is substantially perpendicular to the direction of travel of the contact tip assembly during the deposition process.

20. The welding or processing manufacturing system according to claim 15, wherein the first outlet orifice has a diameter, and the distance is in the range of 20% to 200% of the diameter.

21. The welding or processing manufacturing system according to claim 15, wherein the distance is the distance between the first wire electrode and the second wire electrode, which is within the range of 0.25 to 2.25 times the diameter of the first and second wire electrodes, and is measured between the nearest ends of the first and second wire electrodes.

22. The welding or processing manufacturing system according to claim 15, wherein the aforementioned distance is less than 3 mm.

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