Double-wire welding or additive manufacturing contact tip and diffuser

Abstract

To provide dual wire welding or an additive manufacturing contact tip and a diffuser.SOLUTION: A welding or additive manufacturing contact tip includes an electrically-conductive body extending from a proximal end of the body to a distal end of the body. The body forms a first bore terminating at a first exit orifice at a distal end face of the body, and a second bore terminating at a second exit orifice at the distal end face of the body. The first and second exit orifices are separated from each other by a distance configured to facilitate formation of a bridge droplet between a first wire electrode delivered through the first bore and a second wire electrode delivered through the second bore during a deposition operation.SELECTED DRAWING: None

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims priority to (a) U.S. Patent Application No. 16 / 295,571, filed Mar. 7, 2019, which is incorporated herein by reference in its entirety as if fully reproduced herein; (b) U.S. Patent Application No. 16 / 267,476, filed Feb. 5, 2019, which is incorporated herein by reference in its entirety as if fully reproduced herein; (c) U.S. Provisional Patent Application No. 62 / 750,893, filed Oct. 26, 2018, which is incorporated herein by reference in its entirety as if fully reproduced herein.

[0002] The devices, systems, and methods according to the present invention relate to material deposition using a dual - wire configuration.

Background Art

[0003] When welding, it is often desirable to increase the width of the weld bead or the length of the weld paddle during welding. There can be many different reasons for this, and these are well known in the welding industry. For example, to reduce porosity, it may be desirable to lengthen the weld paddle to keep the weld metal and filler metal molten for a longer period of time. That is, if the weld paddle is molten for a longer period of time, there is more time for harmful gases to escape from the weld bead before the bead solidifies. Furthermore, it may be desirable to increase the width of the weld bead to cover a wider weld gap or to increase the weld deposition rate. In both cases, it is common to use an electrode with an increased diameter. Increasing the diameter increases both the length and width of the weld paddle, even though it is desirable to increase only the width or only the length, rather than both. However, this comes with disadvantages. In particular, the larger the electrode used, the greater the energy required in the welding arc to promote proper welding. This increase in energy increases the heat input to the weld, and because the diameter of the electrode used is larger, more energy is used in the welding operation. Furthermore, this may result in a weld bead shape or cross-section that is not ideal for certain mechanical applications. It may be preferable to use at least two smaller electrodes simultaneously rather than increasing the electrode diameter. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] U.S. Patent Application Publication No. 2013 / 0264323 [Overview of the Initiative] [Means for solving the problem]

[0005] Summary of the Invention The following summary provides a simplified overview to offer a basic understanding of some aspects of the devices, systems, and / or methods discussed herein. This summary is not a comprehensive overview of the devices, systems, and / or methods discussed herein. It is not intended to identify key elements of such devices, systems, and / or methods or to define the scope of such devices, systems, and / or methods. The sole purpose of the following summary is to present some concepts in a simplified form as an introduction to the more detailed descriptions that will be presented later.

[0006] According to one aspect of the present invention, a welded or additively manufactured contact tip is provided. The contact tip includes a conductive body extending from a base end to a tip end of the body. The body has a first hole terminating at a first exit orifice on the tip face of the body and a second hole terminating at a second exit orifice on the tip face of the body. The first and second exit orifices are separated from each other by a distance configured to facilitate the formation of bridge droplets between a first wire electrode fed through the first hole and a second wire electrode fed through the second hole during the deposition operation.

[0007] According to another aspect of the present invention, a welded or additively manufactured contact tip is provided. The contact tip includes a conductive body extending from a base end to a tip end of the body. The body forms a first hole through the body, extending from a first inlet orifice at the base end of the body to a first outlet orifice at the tip end of the body, and a second hole through the body, extending from a second inlet orifice at the base end of the body to a second outlet orifice at the tip end of the body. The first and second outlet orifices are separated from each other by a distance configured to facilitate the formation of a bridge droplet between a first wire electrode fed through the first hole and a second wire electrode fed through the second hole during the deposition operation. The bridge droplet couples the first wire electrode to the second wire electrode before contacting the molten paddle created by the deposition operation.

[0008] According to another aspect of the present invention, a welded or additively manufactured contact tip is provided. The contact tip includes a conductive body extending from a base end to a tip end. The body forms a first channel terminating at the tip end of the body and a second channel terminating at the tip end of the body. At the tip end of the body, the first channel and the second channel are separated from each other by a distance configured to facilitate the formation of a bridge droplet between a first wire electrode fed through the first channel and a second wire electrode fed through the second channel during the deposition operation. The bridge droplet couples the first wire electrode to the second wire electrode before contacting the molten paddle created by the deposition operation.

[0009] The above and / or other aspects of the present invention will become more apparent by describing in detail exemplary embodiments of the invention with reference to the accompanying drawings. [Brief explanation of the drawing]

[0010] [Figure 1] This diagram illustrates an exemplary embodiment of the welding system of the present invention. [Figure 2] This shows a graphical representation of an exemplary contact chip assembly in one embodiment of the present invention. [Figure 3A-3C] This diagram illustrates the welding operation in an exemplary embodiment of the present invention. [Figure 4A-4B] This diagram illustrates the interaction between electric current and magnetic field in an exemplary embodiment of the present invention. [Figure 5A-5B] Figure 5A shows a graphical representation of an exemplary weld bead using a single wire, and Figure 5B shows a graphical representation of an exemplary weld bead using one embodiment of the present invention. [Figure 6] An illustrative flowchart of an exemplary welding process in one embodiment of the present invention is shown. [Figure 7] This diagram illustrates an alternative embodiment of the contact tip assembly used in conjunction with the embodiments of the present invention. [Figure 8] This diagram illustrates an exemplary welding current waveform in an embodiment of the present invention. [Figure 9]Shows a graphical representation of a further exemplary welding current waveform in an embodiment of the present invention. [Figure 10] Shows a graphical representation of an additional exemplary welding current waveform in an embodiment of the present invention. [Figure 11] Shows a part of the welding torch. [Figure 12] Is a perspective view of the contact tip and the diffuser. [Figure 13] Is a perspective view of the contact tip. [Figure 14] Is a perspective view of the contact tip. [Figure 15] Is a perspective view of the diffuser. [Figure 16] Is a perspective view of the diffuser. [Figure 17] Is a perspective view of the contact tip and the bias spring. [Figure 18] Shows a perspective view of the contact tip, the bias spring, and the diffuser. [Figure 19] Shows a part of the welding torch. [Figure 20] Is a perspective view of the contact tip and the diffuser. [Figure 21] Is a perspective view of the contact tip. [Figure 22] Is a perspective view of the contact tip and the diffuser. [Figure 23] Is a perspective view of the contact tip and the diffuser. [Figure 24] Is a perspective view of the diffuser.

Mode for Carrying Out the Invention

[0011] Exemplary embodiments of the present invention will be described hereinafter with reference to the accompanying drawings. The exemplary embodiments described are intended to assist in understanding the present invention and are not intended to limit the scope of the present invention. Like reference numerals refer to like elements throughout.

[0012] As used herein, “at least one,” “one or more,” and “and / or” are open-ended expressions that function as both conjunctions and disjunctions. For example, 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,” “one or more of A, B, or C,” and “A, B, and / or C” mean A only, B only, C only, A and B together, A and C together, B and C together, or A, B, and C together, respectively. Any disjunction or disjunction phrase that presents two or more alternative terms should be understood as intended to include the possibility of including one of the terms, either one of the terms, or both of the terms, whether in the description of an embodiment, in the claims, or in the drawings. For example, the phrase “A or B” should be understood as encompassing the possibilities of “A,” “B,” or “A and B.”

[0013] The embodiments of the present invention discussed herein are considered in the context of GMAW welding, but other embodiments of the present invention are not limited thereto. For example, the embodiments can be used in SAW and FCAW welding operations and other similar types of welding operations. Furthermore, although the electrodes described herein are solid electrodes, the embodiments of the present invention are not limited to the use of solid electrodes, and cored arc welding electrodes (either flux-cored or metal-cored) can also be used without departing from the spirit or scope of the invention. Moreover, embodiments of the present invention can also be used in manual, semi-automatic, and robotic welding operations. Such systems are well known and will not be described in detail herein.

[0014] Referring to the figures below, Figure 1 shows an exemplary embodiment of a welding system 100 according to an exemplary embodiment of the present invention. The welding system 100 includes a welding power supply 109 coupled to both a welding torch 111 (having a contact tip assembly - not shown) and a wire feeder 105. The power supply 109 can be any known type of welding power supply capable of supplying current and welding waveforms described herein, e.g., pulse spray, STT, and / or short-arc welding waveforms. The configuration, design, and operation of such power supplies are well known and therefore do not need to be detailed herein. It should also be noted that welding power can be supplied simultaneously by two or more power supplies - again, the operation of such systems is well known. The power supply 109 may also include a controller 120, which is coupled to a user interface to allow a user to input control parameters or welding parameters for the welding operation. The controller 120 may have a processor, CPU, memory, etc., used to control the operation of the welding process described herein. The torch 111 can be configured similarly to known manual, semi-automatic, or robotic welding torches and can be coupled to any known or used welding gun, and can be linear or gooseneck type as described above. The wire feeder 105 draws electrodes E1 and E2, respectively, from electrode sources 101 and 103, which can be any known type such as reels, spools, or containers. The wire feeder 105 is of a known configuration and utilizes the feed roller 107 to draw electrodes E1 and E2 and push the electrodes toward the torch 111. In exemplary embodiments of the present invention, the feed roller 107 and wire feeder 105 are configured for single-electrode operation. Embodiments of the present invention using a dual-wire configuration can be used in conjunction with the wire feeder 105 and roller 107 designed only for single-wire feeding operation. For example, the roller 107 can be configured for a single 0.045-inch diameter electrode but is suitable for driving two 0.030-inch diameter electrodes without modifying the wire feeder 105 or roller 107.Alternatively, the wire feeder 105 may be designed to provide a separate set of rollers that feed electrodes E1 / E2 respectively, or to have rollers configured to feed two or more electrodes simultaneously (for example, via trapezoidal wire receiving grooves around the rollers that can accommodate two electrodes). In other embodiments, two separate wire feeders may also be used. As shown, the wire feeder 105 communicates with the power supply 109 by welding operations of a known configuration.

[0015] When driven by the roller 107, electrodes E1 and E2 are passed through the liner 113 and fed to the torch 111. The liner 113 is appropriately sized to allow electrodes E1 and E2 to pass to the torch 111. For example, for two 0.030-inch diameter electrodes, a standard 0.0625-inch diameter liner 113 (typically used for a single 0.0625-inch diameter electrode) can be used without modification.

[0016] While the above-referenced example considers the use of two electrodes having the same diameter, the present invention is not limited thereto, and electrodes of a box-like diameter can also be used in embodiments. That is, embodiments of the present invention can use a first larger diameter electrode and a second smaller diameter electrode. In such embodiments, it is possible to more conveniently weld two workpieces of different thicknesses. For example, the larger electrode can be directed towards a larger workpiece, while the smaller electrode can be directed towards a smaller workpiece. Furthermore, embodiments of the present invention are not limited and can be used in many different types of welding operations, including MIG (metal-inert gas), submerged arc, and flux core welding. Furthermore, embodiments of the present invention can be used in automatic, robotic, and semi-automatic welding operations. Furthermore, embodiments of the present invention can be used in combination with different electrode types. For example, it is intended that a core electrode can be combined with an uncore electrode. Furthermore, electrodes of different compositions can be used to achieve desired welding attributes and the composition of the final weld bead. Thus, embodiments of the present invention can be used in a wide range of welding operations.

[0017] Figure 2 shows an exemplary contact tip assembly 200 of the present invention. The contact tip assembly 200 can be made from known contact tip materials and can be used with any known type of welding gun. As shown in this exemplary embodiment, the contact tip assembly has two separate channels 201 and 203 extending along the length of the contact tip assembly 200. During welding, the first electrode E1 is passed through the first channel 201 and the second electrode E2 is passed through the second channel 203. Channels 201 / 203 are typically sized appropriately for the diameter of the wire passed through them. For example, if the electrodes have the same diameter, the channels will have the same diameter. However, if different diameters are to be used, the channels should be sized appropriately to allow the current to flow through the electrodes as appropriate. Furthermore, in the embodiment shown, channels 201 / 203 are configured so that the electrodes E1 / E2 exit the tip face of the contact tip 200 in a parallel relationship. However, in other exemplary embodiments, the channel may be configured such that electrodes E1 / E2 emerge from the tip surface of the contact tip such that an angle of + / -15° exists between the centerlines of each electrode. The angle may be determined based on desired performance characteristics of the welding operation. It should be further noted that in some exemplary embodiments, the contact tip assembly may be a single contact tip integrated with the channel as shown, while in other embodiments, the contact tip assembly may consist of two contact tip subassemblies positioned close to each other, with current directed to each contact tip subassembly.

[0018] As shown in Figure 2, each electrode E1 / E2 is spaced apart by a distance S, which is the distance between the nearest edges of the electrodes. In 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 can be in the range of 2 mm 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 can be in the range of 0.25 to 2.25 times the maximum electrode diameter, while in robotic welding operations, the distance S can be in the same range 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 mm to 3.5 mm.

[0019] The wire electrodes E1 / E2 protrude from the exit orifice at 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 wire, the diameter of the exit orifice can be 0.043 inches; for a 0.040-inch wire, the diameter of the exit orifice can be 0.046 inches; and for a 0.045-inch wire, the diameter of the exit orifice can be 0.052 inches. The channels 201, 203, and the exit orifice are appropriately spaced apart during the welding operation to facilitate the formation of a single bridge droplet between the wire electrodes E1 / E2. For exit orifices sized for electrodes with a diameter of 0.045 inches or less, the distance between the exit orifices (internal circumference distance as well as distance S) can be less than 3 mm to facilitate the formation of a bridge droplet. However, depending on the wire size, magnetic force, orientation (e.g., angle) of channels 201 and 203, a spacing of 3 mm or more between exit orifices may be possible. In certain embodiments, the distance between exit orifices is in the range of 20% to 200% of the diameter of one or both exit orifices, which can also correspond to a distance S between wire electrodes in the range of 0.25 to 2.25 times the diameter of the electrodes.

[0020] Furthermore, as will be discussed later, the distance S should be chosen to ensure that one bridge droplet is formed between the electrodes while ensuring that the electrodes do not come into contact with each other except through the bridge droplet before the droplet is transferred.

[0021] Figure 3A shows an exemplary embodiment of the present invention, illustrating the interaction of magnetic forces from electrodes E1 and E2. As shown, due to the flow of current, a magnetic field is generated around the electrodes, and this magnetic field tends to produce a pinch force that attracts the wires toward each other. This magnetic force tends to create a droplet bridge between the two electrodes, which will be described in more detail later.

[0022] Figure 3B shows a droplet bridge created between two electrodes. That is, as the current through each electrode melts the ends of the electrodes, the magnetic force tends to pull the molten droplets toward each other until they merge. The distance S is far enough so that the solid portions of the electrodes are not attracted to each other into contact, but close enough so that a droplet bridge is created before the molten droplets move to the welding paddle created by the molten arc. The droplets are shown in Figure 3C, where the droplet bridge produces one large droplet that moves to the paddle during welding. As shown, the pinch magnetic force acting on the droplet bridge acts to pinch off the droplets, similar to the use of a pinch force in single-electrode welding operations.

[0023] Furthermore, Figure 4A shows an exemplary representation of the current flow in one embodiment of the present invention. As shown, the welding current is divided to pass through each electrode and, as bridge droplets are formed, is passed through the bridge droplets. The current then flows from the bridge droplets to the paddle and then to the workpiece. In exemplary embodiments where the electrodes are of the same diameter and type, the current is essentially divided equally among the electrodes. For example, in embodiments where the electrodes have different resistance values ​​due to different diameters and / or compositions / configurations, the welding current is applied to the contact tip, as in known methods, and the contact tip provides the welding current to each electrode through the contact between the electrode and the channel of the contact tip, so that each current is related to V=I * The separation is caused by R. Figure 4B shows the magnetic force in a bridge paddle intended for the creation of bridge droplets. As shown, the magnetic force tends to pull each molten portion of the droplet toward each other until each molten portion of the droplet comes into contact with the others.

[0024] Figure 5A shows an exemplary cross-section of a weld made using a single-electrode welding operation. As shown, while the weld bead WB is of appropriate width, the fingers F of the weld bead WB that penetrate into the workpiece W shown have a relatively narrow width. This can occur in single-wire welding operations when higher deposition rates are used. That is, in such welding operations, the fingers F may become too narrow to be reliable in assuming that the fingers have penetrated in the desired direction, and therefore cannot be a reliable indicator of proper penetration. Furthermore, as these narrow fingers deepen, defects such as porosity may be incorporated near the fingers. Moreover, in such welding operations, the useful surface of the weld bead does not penetrate as deeply as desired. Therefore, in certain applications, this mechanical bond is not as strong as desired. Furthermore, in some welding applications, such as when welding horizontal fillet welds, the use of a single electrode makes it difficult to achieve weld legs of equal size at high deposition rates without adding too much heat to the welding operation. These problems are mitigated by using embodiments of the present invention, which can reduce finger penetration and diffuse the fingers to broaden the lateral penetration of the weld. An example of this is shown in Figure 5B, which shows a weld bead of one embodiment of the present invention. As shown in this embodiment, it is possible to achieve similar, i.e., improved weld bead leg symmetry and / or length, as well as a wider weld bead in the weld depth within the weld joint. This improved weld bead geometry is achieved while using a generally lower heat input to the weld. Thus, embodiments of the present invention can provide improved mechanical welding performance with lower heat input and improved deposition rates.

[0025] Figure 6 shows a flowchart 600 of an exemplary welding operation of the present invention. This flowchart is illustrative and not limiting. As shown, a welding current / output is provided by the welding power supply so that the current is directed to the contact tip and electrodes in a known system configuration (610). Exemplary waveforms will be described further below. During welding, a bridge droplet can form 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 until the droplet reaches a size to be transferred, and when it reaches a size to be transferred, the droplet is transferred to the paddle (640). The process is repeated throughout the welding operation. To control the welding process, a power supply controller / control system may use either the 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 is used for a given welding operation so that the bridge current is maintained for that duration, and after the duration, droplet transfer is initiated. In a further exemplary embodiment, a power / 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, if the detected arc voltage (detected via a known type of arc voltage detection circuit) indicates that the arc voltage has reached a bridge droplet threshold level, the power supply initiates the droplet separation portion of the welding waveform. This is further discussed below in some exemplary embodiments of welding waveforms that can be used in conjunction with embodiments of the present invention.

[0026] Figure 7 shows an alternative exemplary embodiment of the contact tip 700 that can be used in conjunction with embodiments of the present invention. As described above, in some embodiments, the electrodes can be directed to the torch via a single wire guide / liner. Naturally, in other embodiments, separate wire guides / liners can be used. However, in embodiments in which a single wire guide / liner is used, the contact tip can 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 one inlet channel 710 with one 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 isolation portion 720 of the contact tip, which directs one electrode to a first outlet channel 711 and the second electrode to a second outlet channel 712, thereby directing the electrodes to separate outlet orifices 701 and 702, respectively. Naturally, channels 710, 711, and 712 should be appropriately sized for the size of the electrodes used, and the separation portion 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 inclined toward each other, but as shown in Figure 2, these channels can also be oriented parallel to each other.

[0027] Referring now to Figures 8 to 10, various exemplary waveforms that can be used in conjunction with exemplary embodiments of the present invention are shown. Generally, in exemplary embodiments of the present invention, the current is increased to create a bridged droplet and build the bridged droplet toward migration. In exemplary embodiments, during migration, the bridged droplet has an average diameter similar to the distance S between the electrodes and can be larger than the diameter of either electrode. Once the droplet is formed, it is migrated via a high peak current, and then the current is reduced to a lower level (e.g., background) to remove the arc pressure acting on the wire. The bridged current then builds the bridged droplet without exerting a pinch force large enough to pinch off the droplet during formation. In exemplary embodiments, this bridged current is in the range of 30% to 70% between the background current and the peak current. In other exemplary embodiments, the bridged current is in the range of 40% to 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 to 280 amperes (i.e., 40% to 60% of the 300 ampere difference). In some embodiments, the bridge current can be maintained for a duration ranging from 1.5 ms to 8 ms, while in other exemplary embodiments, the bridge current is maintained for a duration ranging from 2 ms to 6 ms. In exemplary embodiments, the bridge current duration begins at the end of the background current state and includes a bridge power rise, where the rise can be in the range of 0.33 ms to 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 can be slowed compared to a single-wire process, thereby enabling droplet growth that can be controlled more effectively and allows for higher deposition rates compared to single-wire operation.

[0028] Figure 8 shows an exemplary current waveform 800 for pulsed spray welding operation. As shown, the waveform 800 has a background current level 810, then transitions to a bridge current level 820, during which the bridge droplet grows to a size for migration. The bridge current level is below the spray migration current level 840, at which point the droplet begins to migrate to the paddle. At the end of the bridge current 820, the current rises above the spray migration current level 840 to a peak current level 830. The peak current level is then maintained for a peak duration to complete the droplet migration. After migration, the current is reduced again to the background level, and the process is repeated. Thus, in these embodiments, single droplet migration does not occur during the bridge current portion of the waveform. In such exemplary embodiments, the lower current level of the bridge current 820 allows droplet formation without excessive pinching force to direct the droplet towards the paddle. The use of bridge droplets makes it possible to achieve welding operations in which the peak current 830 can be maintained at a higher level for a longer duration than when using a single wire. For example, in some embodiments, the peak duration can be maintained for 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, for a range of 4 ms to 7 ms. In such embodiments, a significantly improved deposition rate can be achieved. For example, some embodiments achieve deposition rates in the range of 19 lb / hr to 26 lb / hr, while a similar single-wire process can only achieve deposition rates in the range of 10 lb / hr to 16 lb / hr. For example, in a non-limiting embodiment, a pair of two wires having a diameter of 0.040 inches and using a peak current of 700 amps, a background current of 180 amps, and a droplet bridge current of 340 amps can deposit at a rate of 19 lb / hr at a frequency of 120 Hz. Such deposition is at a much lower frequency than conventional welding processes and is therefore more stable.

[0029] Figure 9 shows another exemplary waveform 900 that can be used in short-arc type operation. Here again, the waveform 900 has a background portion 910 before a short-response portion 920 that is structured to clear a short between the droplet and the paddle. During the short-response 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. Here again, the bridge current level 930 is less than the peak current level of the short-response 920. The bridge current level 930 is maintained for a bridge current duration that causes the bridge droplet to form and move toward the paddle. During droplet migration, the droplet current is reduced to a background level, thereby allowing the droplet to advance until a short occurs. Once a short occurs, the short-response / bridge current waveform is repeated. Note that in embodiments of the present invention, it is the presence of bridge droplets that makes the welding process more stable. That is, in conventional welding processes using multiple wires, there are no bridge droplets. In those processes, if one wire shorts or comes into contact with the paddle, the arc voltage drops and the arcs on the other electrodes are extinguished. This does not occur in embodiments of the present invention where the bridge droplet is common to each wire.

[0030] Figure 10 shows a further exemplary waveform 1000, which is an STT (Surface Tension Transfer) type waveform. Since such waveforms are known, they will not be described in detail herein. For further explanation of the STT type waveform, its structure, use, and implementation, Patent Document 1, filed April 5, 2012, is incorporated herein by reference in whole. Here again, this waveform has a background level 1010 and a first peak level 1015 and a second peak level 1020, the second peak level being reached after the short between the droplet and the paddle is cleared. After the second peak current level 1020, the current is reduced to a bridge current level 1030 to form a bridged droplet, 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 can be used, for example, AC STT waveforms, pulsed waveforms, etc.

[0031] As described above, wire electrodes used in multi-wire deposition operations (e.g., welding, additive manufacturing, hard build-up, etc.) can be spaced apart by a distance S that promotes the formation of bridge droplets between wire electrodes. The size of the bridge droplet is determined by the spacing between wire electrodes and the spacing between exit orifices in the contact tip. The size of the bridge droplet determines the width of the electric arc present during deposition, and reducing the distance between exit orifices and wire electrodes narrows the arc width. Larger welds may prefer larger bridge droplets, and smaller welds may prefer smaller bridge droplets. The deposition rate is affected by the arc width, and the deposition rate of small gauge wires can be increased by reducing the distance between exit orifices and wire electrodes (e.g., from about 2 mm to 1 mm).

[0032] The maximum spacing of the exit orifice and the maximum spacing of the wire electrodes are reached when the magnetic force created by the current waveform (e.g., at the peak current level) still allows for the formation of bridged droplets, and exceeded when bridging is no longer possible. The minimum spacing is the spacing that keeps the wires separated at the time of bridge formation. The magnetic force tends to pull the wire electrodes together, and the wires have some flexibility. Therefore, the minimum spacing of the exit orifice and the minimum spacing of the wire electrodes depend on the stiffness of the electrodes, which is influenced by parameters such as wire diameter and construction material.

[0033] Figure 11 shows 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 are not described herein. As shown, the torch comprises several components and is used to deliver at least two wire electrodes and shielding gas to a workpiece in a welding or additive manufacturing operation. The torch includes a diffuser 205 which assists in appropriately directing and distributing the shielding gas in the welding operation. Coupled to the downstream end of the diffuser 205 is a contact tip 200, which is used to deliver the welding current to at least two wire electrodes, which pass through the contact tip simultaneously during welding. The contact tip 200 is configured to facilitate the formation of bridge droplets between the wire electrodes as they are delivered through holes or channels within the contact tip. The bridge droplets couple the first wire electrode to the second wire electrode before coming into contact with the molten paddle created by the deposition operation, as described above.

[0034] An insulator 206 is screwed to the outside of the diffuser 205. The insulator 206 electrically insulates the nozzle 204 from the energized components inside the torch. During welding, the nozzle 204 directs the shielding gas from the diffuser 205 to the tip of the torch and then to the workpiece.

[0035] Conventional contact tips have a thread at the upstream or base 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 fixing system works well for welding with a single wire. The welding wire can pass through the contact tip, and the contact tip can screw into the diffuser by rotating around the wire multiple times. However, when welding with multiple welding wires passing through the contact tip simultaneously, such a fixing system causes undesirable twisting of the welding wires. For example, if two welding wires pass through the contact tip, and then the contact tip is screwed into the diffuser by multiple rotations requiring more than 360°, the welding wires will twist and will no longer be able to pass through the contact tip.

[0036] The contact tip 200 in Figure 11 is attached to the diffuser 205 by rotating the contact tip less than 360°, such as 270° (3 / 4 turn), 180° (1 / 2 turn), 90° (1 / 4 turn), or less than 90°. The rotation of the contact tip 200 required to attach the contact tip to the diffuser 205 can be any angle, preferably less than 360°, as desired, to prevent the multiple wire electrodes passing through the contact tip from twisting excessively during installation. If the welding wire twists excessively during installation of the contact tip, a wire supply problem may occur, potentially leading to "entanglement" of the welding wire.

[0037] Referring to Figures 11 to 16, the contact tip 200 is attached to the diffuser 205 by a quarter-clockwise turn of the contact tip within the diffuser. The contact tip 200 has a tapered shape and a forward or downstream tip that includes a flat portion 215 for gripping with a tool such as pliers. The contact tip 200 is generally cylindrical but has a rear or upstream base portion 208 that includes a radially projecting tab 210 that engages with a slot 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 within the diffuser 205 when the contact tip is installed in the diffuser and functions 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 that of the adjacent downstream portion, causing the shoulder portion 211 to project in a corrugated direction from the cylindrical rear portion 208 of the contact tip. The shoulder portion 211 rests against the end surface of the diffuser 205 when the contact tip 200 is placed in the diffuser.

[0038] The contact tip 200 can be made from known contact tip materials and can be used with any known type of welding gun. The contact tip may comprise a conductive body, such as copper, extending from the rear base end to the front tip. As shown in this exemplary embodiment, the contact tip 200 has two separate wire channels or holes 214 and 216 extending along the length of the contact tip. The channels 214 / 216 may extend between a wire inlet orifice at the base end face of the mounting shank 208 and a wire outlet orifice at the front tip face of the contact tip. During welding, the first wire electrode is fed through the first channel 214 and the second wire electrode is fed through the second channel 216. The channels 214 / 216 are typically sized appropriately for the diameter of the wire being fed through them. For example, if the electrodes have the same diameter, the channels will have the same diameter. However, if different wire sizes are used together, the channels should be sized appropriately to allow current to flow appropriately through electrodes of different sizes. Furthermore, in the embodiments shown, channels 214 / 216 are configured so that the electrodes exit the tip surface of the contact tip 200 in a parallel relationship. However, in other exemplary embodiments, the channels may be configured so that the electrodes exit the tip surface of the contact tip such that an angle of + / -15° exists between the centerlines of each electrode. The angle can be determined based on desired performance characteristics of the welding operation. The contact tip examples considered herein are shown having two electrode holes. However, it should be understood that the contact tip may have two or more electrode holes, such as three or more holes.

[0039] The slot 212 in the inner wall of the diffuser 205 includes a shaft portion 218 and a helical portion 220. The shaft portion 218 of the slot 212 extends to the downstream end face of the diffuser 205, where the shoulder portion 211 of the contact tip 200 seats. After the welding electrode is supplied through the contact tip 200, the radially projecting tab 210 on the mounting shank 208 is inserted into the shaft portion 218 of the slot 212, and the contact tip is pushed into the diffuser 205. When the tab 210 reaches the helical portion 220 of the slot, the contact tip 200 rotates, moving the tab to the end of the helical portion. The helical portion 220 has a slight upstream pitch that pulls the contact tip 200 inward as the contact tip rotates, thereby causing the shoulder portion 211 of the contact tip to seat against the downstream end face of the diffuser 205. The tab 210 of the mounting shank 208 may have a tapered edge 217 that matches the pitch of the slots 212 of the diffuser 205, thereby helping to ensure a close connection between the two components. In the example embodiment shown, the helical portion 220 of the slot 212 allows the contact tip 200 to be secured to the diffuser 205 by a quarter turn of the contact tip 200. However, it should be understood that other angles of rotation are also possible (e.g., a quarter turn, greater than or less than 90°). For example, the helical portion 220 of the slot may extend less than 360° around the inner circumference of the internal chamber of the diffuser 205.

[0040] Figures 17 and 18 show an example of one embodiment of a contact tip 200 that includes a bias mechanism providing an axial force between the contact tip and the diffuser 205. The bias mechanism shown is a bias spring 222, such as a corrugated washer. When the contact tip 200 is mounted to the diffuser 205, the bias spring 222 compresses to maintain an axial force between the contact tip and the diffuser. The axial force helps the radially projecting tab 210 on the mounting shank 208 to seat in the slot 212 of the diffuser 205. In particular, the axial force can press the tapered surface of the tab 210 against the sidewall of the slot in the diffuser 205, thereby helping to fix the contact tip in place and prevent loosening (e.g., due to thermal circulation, mechanical shock, etc.). The mounting shank 208 extends from the shoulder 211 of the contact tip 200, and the bias spring 222 can be arranged annularly around the mounting shank between the radially projecting tab and the shoulder. The bias spring 222 can be captured by the mounting shank 208 so that it cannot be removed without damaging the bias spring or the contact tip. Various types of bias mechanisms, such as retaining washers or coil springs, can be used to maintain axial force between the contact tip 200 and the diffuser 205.

[0041] Figures 19 to 24 show a further embodiment of the contact tip 302 and diffuser 300 in multi-wire welding or additive manufacturing. The contact tip 302 does not require rotation when installed in the diffuser 300, as will be described later. The nozzle 204 and the insulating portion 206 of the welding torch are substantially the same as in the embodiment of Figure 7. The contact tip 302 also includes wire channels 214 / 216 and shoulder portion 211, as described above.

[0042] The contact tip 302 and diffuser 300 are aligned such that there is only one possible mounting orientation between the contact tip and the diffuser. The inner surface 304 of the diffuser and the rear portion 306 of the contact tip or the mounting shank are shown to have corresponding flat portions for aligning the diffuser and the contact tip. However, other adjustment mechanisms, such as slot and protrusion adjustment mechanisms, may also be used.

[0043] After the welding electrode passes through the contact tip 302, the contact tip is inserted axially into the diffuser 300 without twisting or rotating it. The diffuser 300 is collet-type and tightly grips the rear portion 306 of the contact tip, holding it in place by friction. The diffuser 300 may include several slots 308, 310, 312 that allow the downstream end of the diffuser to expand slightly as the contact tip 302 is inserted into the diffuser. The expansion of the downstream end of the diffuser 300 applies a radial gripping force to the rear portion 306 of the contact tip. If desired, additional gripping mechanisms can be used to further secure the contact tip 302 within the diffuser 300. For example, a set screw can secure the contact tip to the diffuser, or a clamp can further compress the downstream end of the diffuser around the rear portion of the contact tip. Such a clamp can be screwed onto the diffuser such that, when the clamp is screwed onto the diffuser, the gripping force applied to the downstream end of the diffuser is provided by the axial movement of the clamp.

[0044] The use of the embodiments described herein can provide significant improvements in stability, weld structure, and performance from known welding operations. However, in addition to welding operations, the embodiments can be used in additive manufacturing operations. In fact, the system 100 described above can be used in additive manufacturing operations as well as 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 manufacturing process, the use of a 0.045-inch wire can provide a deposition rate of about 5 lb / hr before instability occurs. However, with embodiments of the present invention and when using two 0.040-inch wires, a deposition rate of 7 lb / hr can be achieved with stable transfers. Since additive manufacturing processes and systems are known, it is not necessary to describe their details herein. In such processes, bridge currents such as those described above can be used in additive manufacturing current waveforms.

[0045] It should be noted that the exemplary embodiments are not limited to the use of waveforms described above and herein, and other welding type waveforms can be used in combination with embodiments of the present 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 present invention. For example, in the variable polarity embodiment, the bridge portion of the welding waveform can be negatively polarized so as to create bridge droplets while reducing the overall heat input to the welding paddle. For example, when using an AC type waveform, the waveform may have a frequency of 60 Hz to 200 Hz with alternating negative and positive pulses, thereby melting two wires and forming bridge droplets between the two wires. In further embodiments, the frequency may be in the range of 80 Hz to 120 Hz.

[0046] As previously described, embodiments of the present invention can be used in combination with different types of consumables and combinations of consumables, including flux-cored consumables. In fact, embodiments of the present invention can provide more stable welding operation when using flux-cored electrodes. In particular, the use of bridged droplets can help stabilize flux-cored droplets, which may tend to be unstable in single-wire welding operations. Furthermore, embodiments of the present invention can increase 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 be changed from streaming spray to rotary spray, which significantly reduces the stability of the welding operation. However, when using exemplary embodiments of the present invention, bridged droplets stabilize the droplets and greatly improve arc and welding stability at high deposition rates, such as over 20 lb / hr.

[0047] Furthermore, as previously shown, consumables can be of different types and / or combinations, and a given welding operation can be optimized. That is, the use of two different but compatible consumables can be combined to produce a desired welded joint. For example, compatible consumables include hard-fill wire, stainless steel wire, nickel alloy and steel wire of different compositions. As a specific example, mild iron wire can be combined with over-alloyed wire to create a 309 stainless steel composition. This can be advantageous when one of the desired types of consumables does not have the desired welding properties. For example, some consumables for special welding provide desirable weld chemistry properties, but are extremely difficult to use and have problems providing satisfactory welds. However, in embodiments of the present invention, it is possible to use two consumables that are easier to weld and combine to produce the desired weld chemistry properties. Using embodiments of the present invention, alloy / deposition chemistry properties that are not commercially available in other cases or are otherwise very expensive to manufacture can be produced. Thus, the use of two different consumables can reduce the need for expensive or unavailable consumables. Furthermore, dilute alloys can be created using embodiments. For example, the first welding wire can be a common and inexpensive alloy, and the second welding wire can be a special wire. The desired deposition is the average of two well-mixed wires in the formation of bridge droplets at a lower average cost than that of expensive special wires. Furthermore, in some applications, the desired deposition may not be obtainable due to the lack of suitable consumable chemistry properties, but can be achieved by mixing two standard alloy wires that are mixed in bridge droplets and deposited as single droplets. Furthermore, in some applications, such as wear-resistant metal applications, the desired deposition may be a combination of tungsten carbide particles from one wire and chromium carbide particles from the other wire. In yet another application, a mixture of two wires is deposited by mixing a larger wire containing larger particles with a smaller wire containing fewer or smaller particles. Here, the expected contribution from each wire is proportional to the size of the wire, given that the wire feeding rates are the same.In yet another example, the wire feeding rate of the wire can be varied to change the resulting alloy based on the desired deposition, but the mixing of the wire is still produced by bridging droplets formed between the wires.

[0048] Although the present invention has been described in detail with reference to exemplary embodiments, the present invention is not limited to these embodiments. The present invention is defined by the following claims. Those skilled in the art will understand that various changes can be made to the form and details without deviating from the purpose and scope. [Explanation of Symbols]

[0049] 100 welding systems 101, 103 Electrode source 105 Wire Feeder 107 Supply Roller 109 Welding Power Supply 111 Welding Torch 113 Liner 120 controllers 200, 302 Contact Tips Channels 201, 203, 214, and 216 204 nozzles 205, 300 diffusers 206 Insulator 208 Mount Shank 210 Radial projection tab 211 Shoulder 212, 308, 310, 312 slots 215 Flat area 218 Shaft section 220 Spiral part 222 Bias spring 306 Rear part 600 flowcharts 700 Contact Tips 701, 702 Exit Orifice 710 Inlet Channel 711 First Exit Channel 712 Second Exit Channel 720 Separation part 800 waveforms 810 Background current level 820 Bridge Current Level 830 Peak current level 840 Spray transition current level 900 waveforms 910 Background part 920 Short response section 930, 1030 Bridge current levels 1000 Exemplary waveforms 1010 Background Level 1015 First peak level 1020 Second peak level E1, E2 electrode F finger W Workpiece WB welding bead

Claims

1. Welded or additively manufactured contact tip, Conductive body extending from the base end to the tip of the main body The main body is equipped with, A first hole terminating at a first exit orifice on the tip surface of the main body, A second hole terminating at a second exit orifice on the tip surface of the main body, Forming, The main body includes a mounting shank, the mounting shank extends from the shoulder of the contact tip, A welded or additive manufacturing contact tip, wherein the first and second outlet orifices are separated from each other by a distance configured to facilitate the formation of bridge droplets between the first wire electrode and the second wire electrode during a deposition operation in which a welding current flows simultaneously through the contact tip to both the first and second wire electrodes, while preventing the solid portion of the first wire electrode fed through the first hole from coming into contact with the solid portion of the second wire electrode fed through the second hole, and the contact tip is inserted into a diffuser configured to direct and distribute gas during a welding operation, such that the contact tip rotates less than 360° during mounting to the diffuser, in accordance with the passage of the first or second wire electrode or the contact tip.

2. The welded or additive manufactured contact tip according to claim 1, wherein the first exit orifice has a diameter and the distance is in the range of 20% to 200% of the diameter.

3. The welding or additive manufacturing contact tip according to claim 1, wherein the distance is measured between the closest edges of the first wire electrode and the second wire electrode, and provides a spacing S between the first wire electrode and the second wire electrode that is within the range of 0.25 to 2.25 times the diameter of the first wire electrode and the second wire electrode.

4. The welded or additively manufactured contact tip according to claim 1, wherein the aforementioned distance is less than 3 mm.

5. A welded or additively manufactured contact tip according to claim 1, wherein one or more inlet orifices are disposed on the mounting shank, and the mounting shank includes a radially projecting tab.

6. The welded or additively manufactured contact tip according to claim 5, further comprising a bias spring disposed between the radially protruding tab and the tip surface of the main body.

7. The welded or additively manufactured contact tip according to claim 6, wherein the bias spring is arranged annularly around the mounting shank between the shoulder portion and the radially protruding tab.

8. The welded or additively manufactured contact tip according to claim 7, wherein the radially protruding tab has a tapered edge and the bias spring is a corrugated washer.

9. Welded or additively manufactured contact tip, Conductive body extending from the base end to the tip of the main body The main body is equipped with, A first hole passing through the main body extends from a first inlet orifice at the base end of the main body to a first outlet orifice at the tip of the main body, A second hole passing through the main body extends from a second inlet orifice at the base end of the main body to a second outlet orifice at the tip of the main body, Forming, The main body includes a mounting shank, the mounting shank extends from the shoulder of the contact tip, A welded or additive manufacturing contact tip, wherein the first and second outlet orifices are separated from each other by a distance configured to facilitate the formation of a bridge droplet between a first wire electrode fed through the first hole and a second wire electrode fed through the second hole during a deposition operation, the bridge droplets coupling the first wire electrode to the second wire electrode before the welding current flows through the contact tip to both the first and second wire electrodes simultaneously, while preventing the solid portion of the first wire electrode fed through the first hole from contacting the solid portion of the second wire electrode fed through the second hole; and the contact tip is inserted into a diffuser configured to direct and distribute gas during a welding operation, such that the contact tip rotates less than 360° during mounting to the diffuser, as the first or second wire electrode passes through the contact tip.

10. The welded or additive manufactured contact tip according to claim 9, wherein the first exit orifice has a diameter and the distance is in the range of 20% to 200% of the diameter.

11. The welding or additive manufacturing contact tip according to claim 9, wherein the distance is measured between the nearest edges of the first wire electrode and the second wire electrode, and provides a spacing S between the first wire electrode and the second wire electrode that is within the range of 0.25 to 2.25 times the diameter of the first wire electrode and the second wire electrode.

12. The welding or additive manufacturing contact tip according to claim 9, wherein the aforementioned distance is less than 3 mm.

13. The welding or additive manufacturing contact tip according to claim 9, wherein the angle between the center line of the first wire electrode and the center line of the second wire electrode is within the range of +15 degrees to -15 degrees when the first wire electrode exits the first exit orifice and the second wire electrode exits the second exit orifice.

14. The welded or additive manufactured contact tip according to claim 9, wherein the first inlet orifice and the second inlet orifice are located on the mounting shank, and the mounting shank includes a radially projecting tab.

15. The welded or additively manufactured contact tip according to claim 14, further comprising a bias spring disposed between the radially protruding tab and the tip portion of the main body.

16. The welded or additively manufactured contact tip according to claim 15, wherein the bias spring is arranged annularly around the mounting shank between the shoulder portion and the radially protruding tab.

17. The welded or additively manufactured contact tip according to claim 16, wherein the radially protruding tab has a tapered edge and the bias spring is a corrugated washer.

18. Welded or additively manufactured contact tip, Conductive body extending from the base end to the tip of the main body The main body is equipped with, A first channel terminating at the tip surface of the main body, A second channel terminating at the front end surface of the main body, Forming, The main body includes a mounting shank, the mounting shank extends from the shoulder of the contact tip, A welded or additive manufacturing contact tip, wherein, at the tip surface of the main body, the first channel and the second channel are separated from each other by a distance configured to facilitate the formation of a bridge droplet between a first wire electrode fed through the first channel and a second wire electrode fed through the second channel during the deposition operation, the bridge droplets coupling the first wire electrode to the second wire electrode before contact with a molten paddle created by the deposition operation in which a welding current is simultaneously flowed through the contact tip to both the first and second wire electrodes, while preventing the solid portion of the first wire electrode fed through the first channel from contacting the solid portion of the second wire electrode fed through the second channel, and the contact tip is inserted into a diffuser configured to direct and distribute gas during the welding operation, such that the contact tip rotates less than 360° during mounting to the diffuser, as the first or second wire electrode passes through the contact tip.

19. The welded or additively manufactured contact tip according to claim 18, wherein the first channel has a diameter at the tip surface of the body, and the distance is in the range of 20% to 200% of the diameter.

20. The welding or additive manufacturing contact tip according to claim 18, wherein the distance is measured between the closest edges of the first wire electrode and the second wire electrode, and provides a spacing S between the first wire electrode and the second wire electrode that is within the range of 0.25 to 2.25 times the diameter of the first wire electrode and the second wire electrode.

21. The welding or additive manufacturing contact tip according to claim 18, wherein the aforementioned distance is less than 3 mm.

22. A welded or additively manufactured contact tip according to claim 18, wherein one or more inlet orifices are located on the mounting shank, and the mounting shank includes a radially projecting tab.

23. The welded or additively manufactured contact tip according to claim 22, further comprising a bias spring disposed between the radially protruding tab and the tip surface of the main body.

24. The welded or additively manufactured contact tip according to claim 23, wherein the bias spring is arranged annularly around the mounting shank between the shoulder portion and the radially protruding tab.

25. The welded or additively manufactured contact tip according to claim 24, wherein the radially protruding tab has a tapered edge and the bias spring is a corrugated washer.

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