Dual Wire Welding or Additive Manufacturing Systems

Abstract

To provide a device, system and method about material deposition with a dual wire configuration.SOLUTION: A welding or additive manufacturing wire drive system includes a first drive roll and a second drive roll. One or both of the drive rolls has a circumferential groove for simultaneously driving both of a first wire electrode and a second wire electrode located between the drive rolls in the circumferential groove. A sensor device generates a signal or data corresponding to a consumed or remaining amount of one or both of the wire electrodes. The first wire electrode contacts the second wire electrode within the circumferential groove. The first wire electrode further contacts a first sidewall portion of the circumferential groove. The second wire electrode further contacts a second sidewall portion of the circumferential groove. Both of the wire electrodes are offset from a base portion of the circumferential groove, said base portion extending between the first sidewall portion and the second sidewall portion of the circumferential groove.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

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

[0002] During welding, it is often desirable to increase the width of the weld bead or the length of the weld puddle during welding. There are a variety of reasons why this may be desirable, all of which are well known in the welding industry. For example, it may be desirable to increase the weld puddle width to keep the weld and filler metal molten for a longer period of time to reduce porosity. That is, the longer the weld puddle remains molten, the longer toxic gases have to escape from the weld bead before it solidifies. Additionally, it may be desirable to increase the width of the weld bead to cover a wider weld gap or to increase the wire deposition rate. In both cases, this typically involves increasing the diameter of the electrode. Increasing the diameter may require either increasing the width or length of the weld puddle, but not both. Increasing the diameter, however, increases the length and width of the weld puddle. However, this is not without its drawbacks. Specifically, because a larger electrode is used, more energy is required in the welding arc to drive a proper weld. This increased energy results in a higher heat input for the weld, resulting in more energy being used in the welding operation. This is due to the larger diameter electrodes used. Furthermore, the resulting weld bead shape or cross section may not be ideal for some mechanical applications. Instead of increasing the diameter of the electrode, it may be desirable to use two smaller electrodes simultaneously. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 5,816,466 [Patent Document 2] U.S. Patent No. 8,569,653 [Patent Document 3] US Patent Application Publication No. 2013 / 0264323 Summary of the Invention [Means for solving the problem]

[0004] The following summary presents a simplified summary to provide a basic understanding of some aspects of the devices, systems, and / or methods described herein. This summary is not an exhaustive overview of the devices, systems, and / or methods described herein. It is not intended to identify critical elements or delineate the scope of such devices, systems, and / or methods. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

[0005] According to one aspect of the present invention, a welding or additive manufacturing wire drive system is provided. The system includes a first drive roll and a second drive roll. One or both of the first drive roll and the second drive roll have a circumferential groove for simultaneously driving both a first wire electrode and a second wire electrode disposed within the circumferential groove between the first drive roll and the second drive roll. A sensor device generates a signal or data corresponding to the consumed or remaining amount of one or both of the first wire electrode and the second wire electrode. The first wire electrode contacts the second wire electrode within the circumferential groove. The first wire electrode further contacts a first sidewall portion of the circumferential groove. The second wire electrode further contacts a second sidewall portion of the circumferential groove. Both the first wire electrode and the second wire electrode are offset from a bottom portion of the circumferential groove, the bottom portion extending between the first sidewall portion and the second sidewall portion of the circumferential groove.

[0006] According to another aspect of the present invention, a welding or additive manufacturing system is provided. The system includes a first wire electrode source storing a first wire electrode and a second wire electrode source storing a second wire electrode. A welding torch includes a contact tip assembly having a first exit orifice for the first wire electrode and a second exit orifice for the second wire electrode. The system includes at least one power supply and a controller for controlling operation of the power supply. The power supply provides a current waveform to the contact tip assembly. A sensor device generates a signal or data corresponding to a consumed or remaining amount of one or both of the first and second wire electrodes. The first and second exit orifices of the contact tip assembly are spaced apart from each other such that a distance S is provided between the first and second wire electrodes. The contact tip assembly is configured to deliver the current waveform to both the first and second wire electrodes. The distance S is configured to encourage the current waveform to form a bridge droplet between the first and second wire electrodes, the bridge droplet connecting the first and second wire electrodes before contacting the molten puddle during the deposition operation.

[0007] According to another aspect of the present invention, a welding or additive manufacturing system is provided. The system includes a wire feeder including a first drive roll, a second drive roll, and a biasing member that biases the first drive roll toward the second drive roll. One or both of the first drive roll and the second drive roll have a circumferential groove for simultaneously driving both a first wire electrode and a second wire electrode disposed within the circumferential groove between the first drive roll and the second drive roll. A welding torch includes a contact tip having a first exit orifice for the first wire electrode and a second exit orifice for the second wire electrode. The first and second outlet orifices are spaced apart from one another to provide a distance S between the first and second wire electrodes, the distance S being configured to promote the formation of a bridge droplet between the first and second wire electrodes during the deposition operation, the bridge droplet connecting the first and second wire electrodes before contacting a molten puddle during the deposition operation.

[0008] These and other aspects of the present invention will become apparent to those skilled in the art to which the present invention pertains from a reading of the following description taken in conjunction with the accompanying drawings in which: [Brief explanation of the drawings]

[0009] [Figure 1A] 1 shows a schematic diagram of an example welding system. [Figure 1B] 1 shows a schematic diagram of an example welding system. [Figure 2] 1 illustrates a perspective view of an example welding system. [Figure 3] FIG. 1 shows a side view of an example of a wire feeder. [Figure 4] An example of a driving roll is shown. [Figure 5] 1 shows a perspective view of the drive roll of this example. [Figure 6] 1 shows a cross section of a drive roll feeding dual wires. [Figure 7] 1 shows a cross-sectional view of a drive roll feeding dual wires. [Figure 8] 1 shows a cross-sectional view of a drive roll feeding dual wires. [Figure 9] 1 shows a cross-sectional view of a drive roll feeding dual wires. [Figure 10] 1 shows a cross-sectional view of a drive roll feeding dual wires. [Figure 11] 1 shows a cross-sectional view of a drive roll feeding dual wires. [Figure 12] 1 shows a cross-sectional view of a drive roll feeding dual wires. [Figure 13] 1 shows an example of a contact tip assembly. [Figure 14A] 1 shows a portion of an example of a deposition operation. [Figure 14B] 1 shows a portion of an example of a deposition operation. [Figure 14C] 1 shows a portion of an example of a deposition operation. [Figure 15A] An example of the interaction between electric current and magnetic field is shown below. [Figure 15B] An example of the interaction between electric current and magnetic field is shown below. [Figure 16A] Weld beads are shown. [Figure 16B] Weld beads are shown. [Figure 17] A flow diagram is shown. [Figure 18] 1 shows an example of a welding current waveform. [Figure 19] 1 shows an example of a welding current waveform. [Figure 20] 1 shows an example of a welding current waveform. DETAILED DESCRIPTION OF THE INVENTION

[0010]

[0023] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. The exemplary embodiments described are intended to aid in understanding 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.

[0011] As used herein, "at least one," "one or more," and "and / or" are open-ended expressions that operate both conjunctively and disjunctively. For example, "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, A and C, B and C, or A, B, and C. Whether in the description of embodiments, claims, or drawings, disjunctive phrases presenting two or more alternative terms should be understood to contemplate the possibility of including one of those terms, either of those terms, or both of those terms. For example, the phrase "A or B" should be understood to encompass the possibilities of "A" or "B" or "A and B."

[0012] Embodiments of the present invention are described herein in the context of welding systems. Examples of welding systems include gas metal arc welding (GMAW) systems, submerged arc welding (SAW) systems, flux-cored arc welding (FCAW) systems, and metal-cored arc welding (MCAW) systems. Furthermore, while the electrodes described herein may be solid electrodes, embodiments of the present invention are not limited to the use of solid electrodes. For example, flux-cored electrodes and metal-cored electrodes may be used without departing from the spirit or scope of the present invention. Furthermore, embodiments of the present invention may be used in manual, semi-automated, and robotic welding operations. Because such systems are well known, they will not be described in detail herein. In addition to welding operations, embodiments of the present invention may be used in additive manufacturing processes and other welding-type processes involving a driven wire electrode (e.g., build-up welding).

[0013] Referring now to the drawings, FIG. 1A illustrates an exemplary embodiment 100 of a welding system. The welding system 100 includes a power supply 109 coupled to both a welding torch 111 and a wire feeder 105. The power supply 109 may be any known type of welding power supply capable of delivering a welding current and welding waveform (e.g., pulsed spray, STT, and / or short arc type welding waveforms). The structure, design, and operation of such power supplies are well known and need not be described in detail herein. Additionally, welding power may be supplied simultaneously from two or more power supplies, and the operation of such systems is also known. The power supply 109 may further include a controller 120 coupled to a user interface 122 through which a user can input control parameters and welding parameters for the welding operation. The controller 120 may include a processor, a CPU, a memory, etc., used to control the operation of the welding process and the generation of the welding waveform. Torch 111 may be configured similarly to known manual, semi-automatic, or robotic welding torches and may be linear or gooseneck. Wire feeder 105 withdraws wire electrodes E1 and E2 from electrode sources 101 and 103, respectively, which may be of any known type, such as reels, spools, containers, etc. Wire feeder 105 withdraws electrodes or welding wire E1 and E2 using drive roll 107 to push and pull the electrodes relative to torch 111. Details of drive roll 107 are described further below. Drive roll 107 and wire feeder 105 are configured for a dual-electrode welding operation; that is, they simultaneously supply both electrodes E1 and E2 to torch 111 for generating an arc and welding workpiece W. As shown, wire feeder 105 is operatively connected to a power source 109 consistent with known configurations of welding operations. Like the power supply 109, the wire feeder 105 may also include a controller to perform the various operations ascribed to the wire feeder.

[0014] As electrodes E1 and E2 are driven by drive roll 107, they can pass through liner 113 and be delivered to torch 111. Liner 113 is sized appropriately to allow electrodes E1 and E2 to pass through to torch 111. For example, for two 0.030 inch diameter electrodes, a standard 0.0625 inch diameter liner 113 (which is typically used for a single 0.0625 inch diameter electrode) can be used without modification.

[0015] In some embodiments, the wire electrodes E1 and E2 may have different diameters. That is, embodiments of the present invention may use an electrode with a first diameter (larger diameter) and an electrode with a second diameter (smaller diameter). Such embodiments may more conveniently weld two workpieces with different thicknesses. For example, the larger electrode may be directed toward the larger workpiece, and the smaller electrode may be directed toward the smaller workpiece. Furthermore, embodiments of the present invention may be used in various types of welding operations, such as, but not limited to, GMAW, SAW, FCAW, and MCAW. Furthermore, embodiments of the present invention may be used with various types of electrodes. For example, it is contemplated that a cored electrode (e.g., a flux-cored electrode or a metal-cored electrode) may be combined with a non-cored or solid electrode. Furthermore, multiple electrodes with different compositions may be used to achieve desired weld characteristics and weld composition in the final weld bead. Two different (but compatible) consumable materials may be combined to form a desired weld joint. For example, compatible consumables, such as build-up wire, stainless steel wire, nickel alloy, and steel wire, with different compositions, may be combined. As a specific example, mild steel wire and overalloyed wire can be combined to form a 309 stainless steel composition. This can be advantageous when the welding characteristics of a single consumable of a desired type are not desirable. For example, some consumables for specialty welding provide the desired welding chemistry but are very difficult to use and produce satisfactory welds. In contrast, embodiments of the present invention allow the combination of two easy-to-weld consumables to form the desired welding chemistry. Using embodiments of the present invention, it is possible to form alloy / deposition chemistries that would otherwise be commercially unavailable or prohibitively expensive to manufacture. In this way, using two different consumables can eliminate the need for expensive or unavailable consumables. Furthermore, embodiments can be used to form dilution alloys. For example, a first welding wire can be a common, inexpensive alloy, and a second welding wire can be a specialty wire.The resulting deposit is an average of the two wires, thoroughly intermixed in the formation of the molten droplet, and the average cost of the two wires is lower than the cost of expensive specialty wires. Furthermore, in some applications, the desired deposit may be achieved by mixing two standard alloy wires, where the appropriate consumable chemicals may be unavailable due to a shortage, and the deposits can be mixed in the molten droplet and deposited as a single droplet. Furthermore, in some applications, such as wear-resistant metal applications, the desired deposit may be a combination of tungsten carbide particles from one wire and chromium carbide particles from another wire. In yet other applications, a mixture of the two wires is deposited by mixing a larger wire containing larger particles with a smaller wire containing fewer or smaller particles, where the expected contribution of each wire is proportional to the size of the wire. Furthermore, while the exemplary embodiments described herein utilize two wire electrodes simultaneously, other embodiments of the present invention may utilize three or more electrodes. For example, it is contemplated that configurations of three or more electrodes may be utilized consistent with the descriptions and discussions provided herein.

[0016] Figure 1B is similar to Figure 1A, except that in Figure 1B, the electrode sources 102, 104 are contained in drums rather than spools. The wire electrodes E1, E2 may be supplied from any conventional packaging system, such as spools, drums, boxes, reels, etc.

[0017] As shown in FIGS. 1A and 1B, system 100 may include sensor elements or sensors used to track the amount of wire electrodes E1, E2 remaining in their respective packages, the amount of each wire electrode consumed from the package, and / or identify when either electrode is about to be consumed (e.g., indicating an impending wire depletion condition). It is undesirable for either electrode E1, E2 to be consumed (e.g., the packaging system runs out of wire) during the deposition process. This could result in a portion of the deposition being performed using only one wire, potentially causing wire feed issues (e.g., "bird nesting"). By tracking the amount of wire consumed or remaining in the source, or otherwise signaling when an electrode is about to be consumed, an operator can be notified that one or both of the wire electrode sources need to be replaced before they are depleted.

[0018] The sensors monitor or measure characteristics of the wire electrodes, such as their current weight, height within the container, position or location, wire feed rate, etc. From one or more monitored characteristics of the wire, a consumed or remaining amount of wire may be determined. In some embodiments, the monitored characteristics may be received by the wire feeder 105 and / or power source 109 and processed to calculate the consumed or remaining amount of wire. The output from the sensors, either alone or in combination with post-processing by the wire feeder 105 and / or power source 109, may cause the generation of a signal or data corresponding to the consumed or remaining amount of one or both of the wire electrodes E1, E2.

[0019] An example of a sensor is a weight sensor 106 or a scale, which outputs the weight of the electrode source. From the weight, the wire feeder 105 or the power source 109 can determine the consumed or remaining amount of electrodes in the corresponding source. When the consumed or remaining amount of wire electrodes reaches a threshold, the wire feeder 105 and / or the power source 109 may generate an alarm instructing an operator to replace the electrode before it is consumed. This alarm may be displayed on a user interface on the wire feeder 105 or the power source 109 or may be transmitted to a remote device. A signal or data corresponding to the consumed or remaining amount of electrodes E1, E2 may be transmitted between the wire feeder 105 and the power source 109 via a power cable or a separate communication link 108.

[0020] Another example of a sensor is an ultrasonic height sensor 110 that measures the height or distance of a coil of welding electrode. The ultrasonic height sensor 110 is an example of a non-contact sensor. Various types of non-contact sensors may be used to measure how much electrode has been consumed or remains at the source, such as magnetic or inductive sensors 112, 114, and 116. The magnetic or inductive sensor can output a signal when the stored wire reaches a characteristic height. For example, when the coil of wire falls below the sensor height, the sensor can be triggered and output a corresponding signal.

[0021] The amount of wire consumed can be tracked from the wire feed speed of the wire feeder 105. The wire feed speed, or the linear amount of wire fed, can be measured by the linear wire feed sensor 118. The wire feed speed may be determined by the wire feed speed setting used by the wire feeder. The amount of wire fed can be calculated from the wire feed speed and the feed time. In some embodiments, the wire electrodes E1 and E2 may be encoded with information read by the wire feeder 105 or by a separate reading device in communication with the wire feeder and / or power supply 109. The wire feeder 105 or reading device can determine the amount of wire consumed or remaining from the encoded information. For example, the last 20-100 feet of wire may contain encoded information used to determine whether the wire is about to run out. Examples of encoding techniques include magnetically encoding information along the wire or marking the wire with a code (e.g., with a laser).

[0022] 2 shows a perspective view of welding system 100. Wire feeder 105 includes drive rolls that transport wire electrodes E1, E2 from electrode sources 101, 103 for use in a particular application. Wire electrodes E1, E2 may be continuously unwound from a reel, spool, or container (e.g., a box or drum) and delivered to workpiece W (the weldment in this embodiment). Wire feeder 105 may include a drive assembly that utilizes power from one or more prime movers (e.g., electric motors) to drive wire electrodes E1, E2 to the application's work site or workpiece W.

[0023] The welding power supply 109 may receive input power from an external power source (e.g., commercial power), which is routed to an on-board transformer and processor-controlled inverter or chopper circuit (not shown). Output from the power supply 109 may be provided from the welding power output terminals 121 or studs of the welding power supply. The welding gun or welding torch 111 and wire conduit may be electrically connected to the welding power supply 109 through a welding wire feeder 105, which delivers welding current to the workpiece W in a manner known in the art. Thus, welding wires E1, E2 are fed and metered (i.e., dispensed) through the torch 111 in any manner suitable for carrying out the welding process, depending on the application and / or end user requirements. Note that electrodes E1, E2 conduct electricity to establish a welding arc, and are delivered to the workpiece W at a voltage potential equal to or approximately equal to the output voltage of the welding power supply 109, which may be significantly higher than ground.

[0024] Various methods for transporting the wire electrodes E1, E2 are known in the art, including, for example, using power or torque from a prime mover to push the electrodes into the torch 111. Another electrode transport method is a push / pull method that utilizes multiple prime movers. The electrodes E1, E2 are delivered to the torch 111, which may have an activation mechanism, such as a trigger, to dispense the electrodes at the user's discretion. It may sometimes be necessary to deliver the electrodes E1, E2 at various feed rates. Therefore, the output of the prime movers can be adjusted to accommodate the varying wire feed speed (WFS) of the electrodes E1, E2. Specifically, the drive motor of the wire feeder 105 may be a variable speed motor to adjust the WFS.

[0025] Drive motor 123 is shown in Figure 3. Wire feeder 105 and / or drive motor 123 may draw operating power from welding power source 109 or from an entirely separate power source. Nevertheless, any manner of providing power to operate welding wire feeder 105 and / or drive motor 123 may be selected with acoustic engineering judgment suitable for use with embodiments of the present invention.

[0026] 2 and 3, welding wire feeder 105 may include a drive assembly, or drive roll assembly. As mentioned above, drive motor 123, also referred to as a wire feeder motor, provides the power, i.e., torque, to transport first and second welding wires E1, E2 from the wire feeder to torch 111 and then to workpiece W. Drive rolls 107 are included, which grip welding wires E1, E2 to push or pull them in the appropriate direction (i.e., toward workpiece W). A series of vertically aligned drive rolls 107 have corresponding, aligned annular or circumferential grooves through which welding wires E1, E2 pass simultaneously. As can be seen, the series of vertically aligned drive rolls 107 rotate in opposite directions to drive welding wires E1, E2 through wire feeder 105. For example, in FIG. 3 , the upper drive roll 107 rotates clockwise, and the lower drive roll rotates counterclockwise. The drive roll 107 may be cylindrical, or more specifically, disk-shaped, although this particular shape should not be construed as limiting. The surface, i.e., the outer periphery, of the drive roll 107 may be constructed of a material (such as steel) of sufficient hardness that is durable and suitable for firmly gripping the welding wires E1 and E2. As shown, the drive rolls 107 may be arranged in pairs along the wire trajectory, with each drive roll of the pair supported on opposite sides of the welding wires E1 and E2, such that the outer periphery of each drive roll engages with the opposite sides of the wire (e.g., from above and below). Note that the central axes of the drive rolls 107 extend substantially parallel to each other and substantially transverse to the trajectories of the welding wires E1 and E2.

[0027] The wire feeder 105 may include a biasing member that biases the series of vertically aligned drive rolls 107 toward each other. The biasing member sets the clamping force or pressure that the drive rolls 107 apply to the welding wires E1, E2. For example, the wire feeder 105 may include a biasing spring 125 that applies a biasing force to one or more of the drive rolls 107, thereby setting the compression that the drive rolls apply to the welding wires E1, E2. In the exemplary embodiment of FIG. 3 , the biasing spring 125 is attached to an adjustment rod 127 that can be moved inward and outward to adjust the pressure of the biasing spring 125. The force of the biasing spring 125 is transmitted to the upper drive roll 107 via a pivot lever 129. As described above, the series of vertically aligned drive rolls 107 have corresponding, aligned annular or circumferential grooves through which the welding wires E1, E2 pass simultaneously. That is, welding wires E1, E2 are positioned together in grooves in the upper and lower drive rolls. Welding wires E1, E2 are packed or forced into the grooves by a biasing force applied to drive roll 107 by biasing spring 125. As will be explained further below, welding wires E1, E2 come into contact with each other within the grooves as they are packed into the grooves by drive roll 107. In addition to the pressure exerted on welding wires E1, E2 from above / below, pressure is also exerted on welding wires E1, E2 from the side to force welding wires E1, E2 together within the grooves. The pressure from the side is provided by the shape of the side walls of the groove.

[0028] Details of the construction of welding wire feeders are described in U.S. Pat. No. 6,619,898 (Patent Document 1) and U.S. Pat. No. 6,619,898 (Patent Document 2) issued on U.S. Pat. No. 6,619,893 ...3), both of which are incorporated herein by reference.

[0029] 4 and 5 show an example of a drive roll 107. The drive roll has a central bore. The inner surface of the bore may include a contoured recess 131 that receives a protrusion of a drive mechanism (e.g., a drive gear), thereby transmitting drive torque to the drive roll 107. The drive roll 107 includes one or more annular or circumferential wire-receiving grooves 133, 135. The wire-receiving grooves 133, 135 are axially spaced about the circumference of the drive roll 107. The wire-receiving grooves 133, 135 are designed to receive two welding wires. Typical diameters of welding wires used with the drive roll 107 include, for example, 0.030 inches, 0.035 inches, 0.040 inches, 0.045 inches, etc. The wire-receiving grooves 133, 135 may be the same width and depth as one another, or may have different widths and depths to accommodate different sizes or combinations of dual welding wires. If the wire-receiving grooves 133, 135 each have the same width and depth, the drive roll 107 can be reused if one groove wears by simply flipping the drive roll over and reinstalling it on the wire feeder. The wire-receiving grooves 133, 135 may be configured to simultaneously drive two wires of the same diameter or two wires of different diameters. In FIG. 4 , the wire-receiving grooves 133, 135 are trapezoidal in shape, with straight, angled, or inwardly tapered sidewalls and a flat bottom extending between the sidewalls. However, the wire-receiving grooves 133, 135 may have shapes other than trapezoidal, such as a curved, concave groove bottom. In some embodiments, the grooves 133, 135 may include a frictional surface treatment, such as knurling, to provide a firm grip on the welding wire.

[0030] 6-12 show partial cross-sectional views of various drive rolls 107 as they are mounted on a wire feeder supplying a dual-wire electrode. The drive rolls 107 are biased together to apply a clamping force to the first and second welding wires E1 and E2. Both welding wires E1 and E2 are disposed within annular grooves in the upper and lower drive rolls 107. The annular grooves are aligned with one another and may be trapezoidal in shape. In FIG. 6, the trapezoidal shape is an isosceles trapezoid formed by an inner sidewall 137, an outer sidewall 139, and a groove bottom 141 extending between the sidewalls. This isosceles trapezoid is inverted relative to the outer circumferential surface of the drive roll 107 as a concave cross-section.

[0031] The biasing force applied by the drive roll 107 clamps the welding wires E1, E2 within the annular groove between the upper and lower sidewalls 137, 139 that define the groove and the adjacent welding wire. The welding wires E1, E2 are held stable by three-point contact within the annular groove. This clamping system may allow both wires to feed from the wire feeder in a consistent manner. The two welding wires E1, E2 support each other during feeding and pull each other longitudinally through friction. The inner and outer sidewalls 137, 139 of the annular groove are angled, applying both vertical and horizontal clamping forces to the welding wires E1, E2. The horizontal clamping force pushes the welding wires E1, E2 together, causing them to contact each other. In some embodiments, the welding wires E1, E2 are clamped within the annular groove so that they are radially offset from both groove bottoms 141. That is, the welding wires E1, E2 are pinned relative to each other and between the angled side walls 137, 139 of the groove so that there is a gap between the welding wires and the groove bottom surface 141. This is best seen in FIG.

[0032] The clamping system described above allows for some variation in the diameter of the welding wires E1 and E2 (e.g., due to manufacturing tolerances). If each welding wire E1 and E2 has its own dedicated annular groove in the drive roll 107 and one welding wire is slightly larger than the other, the smaller welding wire may not be adequately clamped between the drive rolls. In such a situation, the larger welding wire restricts the radial displacement of the drive rolls 107 toward each other, thereby preventing proper clamping of the smaller wire. This can lead to feeding problems and possible bird nesting of the smaller welding wire during feeding. The clamping system described above is self-adjusting and can accommodate wires of different sizes. As shown in FIG. 7, if one welding wire E1 is thicker than the other welding wire E2, the contact point between the two wires will be axially displaced from its center position within the annular groove toward the smaller wire. Three-point contact with each welding wire E1 and E2 is maintained by the groove sidewalls 137 and 139 and the adjacent welding wire.

[0033] The cross-sectional shape of the annular groove 143 of the drive roll 107 shown in FIG. 8 is an acute trapezoid rather than an isosceles trapezoid. The groove's inner and outer sidewalls 145, 147 have varying lengths and form different angles relative to the outer circumferential surface of the drive roll. In FIG. 9, the annular groove 149 of the drive roll 107 is a right-angle trapezoid. Acute and right-angle trapezoid grooves can accommodate larger differences in welding wire diameters than isosceles trapezoid grooves. Thus, acute and right-angle trapezoid grooves may be used when the groove is intended to drive welding wires of different diameters, e.g., 0.040 inch and 0.045 inch. In some embodiments, the sidewalls and / or bottom surface of the groove may be curved (e.g., concave or convex). Additionally, the inner corner transitions between the sidewalls and bottom surface of the trapezoidal groove may be curved or rounded. 10 has straight, angled sidewalls 150 joined to a concavely curved or radiused groove bottom 152. In one exemplary embodiment, the angle between the sidewalls 150 and the outer periphery of the drive roll 107 is approximately 150°, although other angles are possible and may be determined by acoustic engineering judgment.

[0034] In one exemplary embodiment shown in FIG. 11 , the grooves of one drive roll 107 are trapezoidal and the grooves of the other drive roll 107a are non-trapezoidal for welding wires E1 and E2. While the non-trapezoidal grooves are rectangular in shape in FIG. 11 , other shapes are possible. For example, the non-trapezoidal grooves may be curved, e.g., oval or rounded. Furthermore, trapezoidal grooves are shown on the lower drive roll 107. However, trapezoidal grooves may be on the upper drive roll 107a and non-trapezoidal grooves on the lower drive roll. Welding wires E1 and E2 are clamped between the side walls 137 and 139 of the trapezoidal grooves and the bottom surface 153 of the non-trapezoidal groove 151, respectively, so that the welding wires contact each other as described above. Thus, welding wires E1 and E2 are stably held within the annular grooves 107 and 107a by three-point contact.

[0035] In one exemplary embodiment shown in FIG. 12 , the grooves of one drive roll 107 are trapezoidal for welding wires E1 and E2, while the other drive roll 107b has no grooves and instead directly contacts the welding wires at its outer circumferential surface 155. The trapezoidal grooves are shown on the lower drive roll 107; however, trapezoidal grooves may also be on the upper drive roll. Welding wires E1 and E2 are clamped between the side walls 137 and 139 of the trapezoidal grooves, respectively, and the outer circumferential surface 155 of the upper drive roll 107b, so that the welding wires contact each other as described above. Thus, welding wires E1 and E2 are stably held by three-point contact.

[0036] FIG. 13 illustrates an exemplary contact tip assembly 200 of the present invention. The contact tip assembly 200 may be made of known contact tip materials and may 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, a first electrode E1 is threaded through the first channel 201, and a second electrode E2 is threaded through the second channel 203. As noted above, while the exemplary embodiments described herein utilize two wire electrodes simultaneously, other embodiments of the present invention may utilize three or more electrodes. For example, it is contemplated that configurations of three or more electrodes may be utilized consistent with the description and discussion herein. Thus, the contact tip assembly 200 may include three or more channels for simultaneously delivering current to three or more electrodes. The size of the channels 201 / 203 is typically determined appropriately to accommodate the diameter of the wires threaded through those channels. For example, if each electrode has the same diameter, each channel will have the same diameter. On the other hand, if different diameters are used, each channel must be sized appropriately to properly route current to each electrode. Furthermore, in the illustrated embodiment, channels 201 / 203 are configured so that electrodes E1 / E2 exit the distal end face of contact tip 200 parallel to one another. In contrast, in other exemplary embodiments, each channel may be configured so that electrodes E1 / E2 exit the distal end face of the contact tip at an angle between their respective centerlines in the range of ±15°. This angulation may be determined based on the desired performance characteristics of the welding, additive manufacturing, or other deposition operation being performed. Furthermore, in some exemplary embodiments, the contact tip assembly may be a single, integrated contact tip with channels, as shown, while in other embodiments, the contact tip assembly may be comprised of two contact tip subassemblies positioned adjacent to one another, with current routed to each of these contact tip subassemblies.

[0037] As shown in FIG. 13 , each electrode E1 / E2 is spaced apart by a distance S, where the distance S is the distance between the closest edges of each electrode. In an exemplary embodiment of the invention, this distance is in the range of 0.025 to 4 times the diameter of the larger of the two electrodes E1 / E2, while in another exemplary embodiment, the distance S is in the range of 2 to 3 times the largest diameter. For example, if the diameter of each electrode is 1 mm, the distance S may be in the range of 2 to 3 mm. In another exemplary embodiment, the distance S is in the range of 0.25 to 2.25 times the diameter of one of the wires (e.g., the larger of the two electrodes). In a manual or semi-automatic welding operation, the distance S may be in the range of 0.25 to 2.25 times the largest electrode diameter, while in a robotic welding operation, the distance S may be in the same range or a different range (e.g., 2.5 to 3.5 times the largest electrode diameter). In an exemplary embodiment, the distance S is in the range of 1.5 to 3.5 mm.

[0038] As will be further explained below, the distance S must be selected so that a single bridge droplet forms between the electrodes before droplet transfer, while preventing the electrodes from contacting each other except through the bridge droplet.

[0039] 14A illustrates one exemplary embodiment of the present invention, showing the interaction of the magnetic forces from each electrode E1 and E2. As shown, the flow of current generates a magnetic field around the electrodes, which tends to create a pinch force that pulls the wires together. This magnetic force tends to form a droplet bridge between the two electrodes, as will be described in more detail below.

[0040] FIG. 14B shows a droplet bridge formed between two electrodes. That is, as current through each electrode melts the ends of the electrodes, magnetic forces tend to attract the molten droplets toward each other and eventually connect them. The distance S is far enough that the solid portions of the electrodes are not attracted to each other and touch, but close enough that the droplet bridge forms before the molten droplets are transferred to the weld puddle formed by the welding arc. The droplets are shown in FIG. 14C, where the droplet bridge forms a single large droplet that is transferred to the puddle during welding. As shown, the magnetic pinching force acting on the droplet bridge acts to pinch off the droplet, similar to the pinching force used in a single-electrode welding operation.

[0041] FIG. 15A further illustrates an exemplary representation of current flow in one embodiment of the present invention. As illustrated, the welding current is divided to flow through each electrode, and once the bridge droplet is formed, it flows toward and through the bridge droplet. The current then passes from the bridge droplet to the puddle and workpiece. In an exemplary embodiment in which the electrodes are the same diameter and type, the current is essentially divided equally through each electrode. In an embodiment in which the electrodes have different resistances, for example, due to different diameters and / or compositions / structures, the current is distributed according to the relationship V = I × R. This is because the welding current is applied to the contact tip, as in known methodologies, and the contact tip supplies the welding current to each electrode through contact between the electrode and the channel wall of the contact tip. FIG. 15B illustrates magnetic forces within the bridge puddle, which assist in the formation of the bridge droplet. As illustrated, these magnetic forces tend to attract the respective molten portions of each electrode toward each other, eventually bringing them into contact with each other.

[0042] FIG. 16A shows an exemplary cross-section of a weld created in a single-electrode welding operation. As shown, the weld bead WB has the proper width, but the fingers F of the weld bead WB penetrate into the workpiece W as shown and are relatively narrow. This can occur when high deposition rates are used in single-wire welding operations. That is, in such welding operations, the fingers F can be so narrow that it is not possible to reliably assume that the fingers have penetrated in the desired direction, and therefore the fingers F are not a reliable indicator of proper weld penetration. Furthermore, the deeper the narrow fingers penetrate, the more likely they are to lead to defects such as pitting near the fingers. Furthermore, in such welding operations, the useful side of the weld bead does not penetrate as deeply as desired. Therefore, in some applications, the mechanical bond is not as strong as desired. Furthermore, in some welding applications, such as when performing horizontal fillet welds, using a single electrode makes it difficult to achieve equal-sized weld legs at high deposition rates without adding excessive heat to the welding operation. These problems are alleviated by embodiments of the present invention. That is, embodiments of the present invention can reduce finger penetration and widen the fingers, increasing the width of the lateral penetration of the weld. An example of this is shown in FIG. 16B, which shows a weld bead of one embodiment of the present invention. As shown, this embodiment can achieve similar or improved weld bead leg symmetry and / or length while also achieving a wider weld bead at a greater depth within the weld joint. This improved weld bead shape is achieved while reducing the total heat input to the weld. Thus, embodiments of the present invention can improve mechanical welding performance while reducing heat input and increasing deposition rates. The use of two or more electrodes during the deposition operation can also improve arc characteristics.

[0043] FIG. 17 shows 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 / power is applied by the welding power supply (610) to induce current in the contact tip and electrode consistent with known system architectures. Exemplary waveforms are described in detail below. During welding, a bridge droplet is allowed to form between the electrodes (620), and the droplets from each electrode contact each other to form a bridge droplet. The bridge droplet forms before contacting the weld puddle. Upon bridge droplet formation, at least one of the duration and droplet size is detected until the droplet reaches a target size for transition, after which the droplet is transferred to the molten puddle (640). This process is repeated throughout the welding operation. To control the welding process, a power supply controller / control system can use either the bridge droplet current duration and / or the bridge droplet size detection results to determine whether the bridge droplet is a target size for transition. For example, in one embodiment, a predetermined bridge current duration is used for a given welding operation, and the bridge current is maintained for that duration before droplet transfer is initiated. In another exemplary embodiment, a controller of the power supply 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 the detected arc voltage (detected by an arc voltage detection circuit of known type) reaches a bridge droplet threshold level, the power supply initiates the droplet separation portion of the welding waveform. This is described in more detail below with respect to exemplary embodiments of welding waveforms usable with embodiments of the present invention.

[0044] 18-20, various exemplary waveforms usable with exemplary embodiments of the present invention are shown. Generally, in exemplary embodiments of the present invention, a bridge droplet is formed and grown toward transfer by increasing the current. In exemplary embodiments, the average diameter of the bridge droplet at transfer is equal to the distance S between the electrodes, which may be greater than the diameter of either electrode. Once formed, the droplet is transferred by a high peak current, after which the current is reduced to a lower level (e.g., background level) to remove the arc pressure acting on the wire. A bridging current then grows the bridge droplet. The pinch force is not so high that it cannot pinch off the growing droplet. In exemplary embodiments, this bridging current is at a level in the range of 30-70% between the background current and the peak current. In another exemplary embodiment, the bridging current is at a level in the range of 40-60% between the background current and the peak current. For example, if the background current is 100 amps and the peak current is 400 amps, the bridging current will be in the range of 220-280 amps (i.e., 40-60% of the 300 amp difference). In some embodiments, the bridging current may be held for a duration in the range of 1.5-8 milliseconds, and in another exemplary embodiment, the bridging current may be held for a duration in the range of 2-6 milliseconds. In an exemplary embodiment, the bridging current duration includes a period during which the bridging current ramps up starting from the end of the background current state, and this ramp time may range from 0.33-0.67 milliseconds, depending on the bridging current level and ramp rate. In an exemplary embodiment of the invention, the waveform pulse frequency may be slowed compared to a single-wire process to account for droplet growth, which may improve control, and to allow for higher deposition rates compared to single-wire operation.

[0045] FIG. 18 shows an exemplary current waveform 800 for pulsed spray welding-type operations. As shown, the waveform 800 has a background current level 810 that transitions to a bridge current level 820, during which the bridge droplet grows to a target size for transfer. The bridge current level is lower than the spray transition current level 840, at which the droplet begins to transfer to the puddle. At the end of the bridge current 820, the current is increased above the spray transition current level 840 to a peak current level 830. The peak current level is then held for the peak duration, allowing the droplet transfer to be completed. After the transition, the current is again reduced to the background level, and the process repeats. Thus, in these embodiments, no single droplet transfer occurs during the bridge current portion of the waveform. In such exemplary embodiments, the lower bridge current level 820 allows droplet formation without excessive pinch force to induce the droplet into the puddle. By using a bridge droplet, welding operations can be achieved in which the peak current 830 can be maintained at a higher level and for a longer duration than when using a single wire. For example, some embodiments can maintain peak current durations of at least 4 milliseconds, and for periods ranging from 4 to 7 milliseconds, when the peak current level is 550 to 700 amperes and the background current is in the range of 150 to 400 amperes. Such embodiments can significantly improve deposition rates. For example, some embodiments achieve deposition rates in the range of 19 to 26 pounds per hour, compared to deposition rates in the range of only 10 to 16 pounds per hour for similar single-wire processes. For example, in one non-limiting embodiment, a pair of twin wires with a diameter of 0.040 inches can be deposited at a rate of 19 pounds per hour at a frequency of 120 Hz with a peak current of 700 amperes, a background current of 180 amperes, and a droplet bridge current of 340 amperes. Such deposition occurs at a much lower frequency and, therefore, more stable than conventional welding processes.

[0046] FIG. 19 shows another exemplary waveform 900 that can be used in a short-arc welding operation. Again, the waveform 900 has a background portion 910 followed by a short-circuit response portion 920 structured to clear a short circuit between the droplet and the puddle. During the short-circuit response 920, the current is increased to clear the short circuit, and once the short circuit is cleared, the current is reduced to a bridge current level 930, during which a bridge droplet forms. Again, the bridge current level 930 is lower than the peak current level of the short-circuit response 920. The bridge current level 930 is maintained for a bridge current duration that allows a bridge droplet to form and be guided to the puddle. Then, during droplet transfer, the current is reduced to a background level, allowing the droplet to advance until a short circuit occurs. Once a short circuit occurs, the short-circuit response / bridge current waveform is repeated. Note that in embodiments of the present invention, it is the presence of a bridge droplet that makes the welding process more stable. This is because bridge droplets are not present in conventional welding processes using multiple wires. In such a process, if one wire shorts or makes contact with the puddle, the arc voltage drops and the arc to the other electrode is extinguished or killed. This does not occur in embodiments of the present invention, and the bridging droplet is common to each wire.

[0047] FIG. 20 shows another exemplary waveform 1000, which is an STT (surface tension transfer) type waveform. Such waveforms are known and will not be described in detail here. For a detailed description of STT type waveforms, their structure, use, and implementation, U.S. Patent Application Publication No. 2012 / 0124994, filed April 5, 2012, is incorporated herein in its entirety. Again, this waveform has a background level 1010, a first peak level 1015, and a second peak level 1020, the second peak level being reached after a short circuit between the droplet and the puddle is cleared. After the second peak current level 1020, the current is reduced to a bridge current level 1030, where a bridge droplet forms, and then the current is reduced to the background level 1010, allowing the droplet to propel toward the puddle until it contacts the puddle. In another embodiment, an AC waveform may be used, such as an AC STT waveform, a pulsed waveform, or the like.

[0048] Use of the embodiments described herein can result in significant improvements in stability, weld structure, and performance over known welding operations. However, embodiments may be used in additive manufacturing operations beyond welding operations. Indeed, the system 100 described above can be used in additive manufacturing operations as well as welding operations. In exemplary embodiments, increased deposition rates can be achieved in additive manufacturing operations. For example, when using an STT-type waveform in a single-wire additive manufacturing process, a deposition rate of approximately 5 pounds per hour is possible using a 0.045-inch wire before it becomes unstable. In contrast, using embodiments of the present invention and two 0.040-inch wires, a deposition rate of 7 pounds per hour is achievable at a stable transition. Because additive manufacturing processes and systems are known, a detailed description of the details of such processes and systems is not necessary herein. In such processes, a bridging current, such as the bridging current described above, may be used in the additive manufacturing current waveform.

[0049] It should be noted that exemplary embodiments are not limited to the use of the waveforms described above and herein, and other welding-type waveforms may be used with embodiments of the present invention. For example, alternative embodiments may use pulsed spray welding waveforms of various polarities, AC waveforms, etc., without departing from the spirit and scope of the present invention. For example, in alternative polarity embodiments, the bridge portion of the welding waveform may be completed with negative polarity so that a bridge droplet is formed while reducing the total heat input to the weld puddle. For example, when an AC-type waveform is used, the waveform may have an alternating positive and negative pulse frequency of 60 to 200 Hz, which can melt two wires and form a bridge droplet between them. In alternative embodiments, the frequency may be in the range of 80 to 120 Hz.

[0050] As described, embodiments of the present invention can be used with various types and combinations of consumables, including flux-cored consumables. Indeed, embodiments of the present invention may achieve a more stable welding operation when using flux-cored electrodes. Specifically, the use of bridging droplets can help stabilize flux-cored droplets, which tend to be unstable in single-wire welding operations. Furthermore, embodiments of the present invention enable increased weld 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 a streaming spray to a rotating spray, which significantly reduces the stability of the welding operation. In contrast, with exemplary embodiments of the present invention, bridging droplets stabilize the droplets, thereby significantly improving arc and weld stability at high deposition rates (e.g., above 20 pounds per hour).

[0051] It will be understood that the present disclosure is illustrative and that various modifications may be made by adding, modifying, or deleting details without departing from the fair scope of the teachings contained herein. Accordingly, the present invention is not limited to the specific details of this disclosure except to the extent that the following claims are necessarily so limited. [Explanation of symbols]

[0052] 100 Welding System 105 Wire Feeder 106 Weight Sensor 107 Drive Roll 107a Driving Roll 107b Driving Roll 108 Communication Links 109 Power supply 110 Ultrasonic height sensor 111 Welding Torch 113 Liner 118 Straight Wire Feed Sensor 120 Controller 121 Welding output terminal 122 User Interface 123 Drive motor 125 bias spring 127 Adjustment Rod 131 Molded recess 133, 135 Wire receiving groove 137 Inner sidewall 139 Outer side wall 141 Groove bottom surface 143 Annular groove 145 Inner sidewall 147 Outer side wall 149 Circular Groove 150 side wall 151 Non-trapezoidal groove 152 Groove bottom surface 153 bottom 155 Outer surface 200 Contact Tip Assembly Channels 201 and 203

Claims

1. a first wire electrode source storing a first wire electrode; a second wire electrode source storing a second wire electrode; a circumferential groove for simultaneously driving both the first wire electrode and the second wire electrode; a welding torch including a contact tip assembly having a first exit orifice for the first wire electrode and a second exit orifice for the second wire electrode; at least one power supply and a controller for controlling operation of the power supply, the power supply providing a current waveform to the contact tip assembly; a sensor device that generates a signal or data corresponding to a consumed amount or remaining amount of one or both of the first wire electrode and the second wire electrode; Including, the first and second exit orifices of the contact tip assembly are spaced apart from one another such that a distance S is provided between the first wire electrode and the second wire electrode; the contact tip assembly is configured to deliver the current waveform to both the first wire electrode and the second wire electrode; both the first wire electrode and the second wire electrode are offset from a concave bottom portion of the circumferential groove, the concave bottom portion extending between sidewall portions of the circumferential groove; the distance S is configured to promote the current waveform to form a bridge droplet between the first wire electrode and the second wire electrode, the bridge droplet connecting the first wire electrode and the second wire electrode before contacting a molten puddle during a deposition operation; Welding or additive manufacturing systems.

2. The welding or additive manufacturing system of claim 1 , wherein the sensor device measures the consumed or remaining weight of the one or both of the first wire electrode and the second wire electrode.

3. 2. The welding or additive manufacturing system of claim 1, wherein the sensor device measures the consumed or remaining length of the one or both of the first wire electrode and the second wire electrode and / or the sensor device measures the consumed or remaining height of the one or both of the first wire electrode and the second wire electrode.

4. The welding or additive manufacturing system of claim 1, further comprising a wire feeder including a first drive roll, a second drive roll, and a biasing member biasing the first drive roll toward the second drive roll, wherein one or both of the first drive roll and the second drive roll have the circumferential groove.

5. 2. The welding or additive manufacturing system of claim 1, wherein the distance S is measured as the separation between the nearest edges of the first wire electrode and the second wire electrode and is in the range of 1.5 to 3.5 mm.

6. 2. The welding or additive manufacturing system of claim 1, wherein the distance S is measured as the spacing between the nearest edges of the first wire electrode and the second wire electrode and is in the range of 2 to 3 mm.

7. 2. The welding or additive manufacturing system of claim 1, wherein the distance S is measured as the separation between the nearest edges of the first wire electrode and the second wire electrode and is in the range of 0.25 to 2.25 times the largest diameter of either the first wire electrode or the second wire electrode.

8. 2. The welding or additive manufacturing system of claim 1, wherein the distance S is measured as the separation between the nearest edges of the first wire electrode and the second wire electrode and is in the range of 2.5 to 3.5 times the largest diameter of either the first wire electrode or the second wire electrode.

9. The welding or additive manufacturing system of claim 1 , wherein the signal or data indicates an impending wire starvation condition.

10. a wire feeder including a first drive roll, a second drive roll, and a biasing member that biases the first drive roll toward the second drive roll, wherein one or both of the first drive roll and the second drive roll have a circumferential groove for simultaneously driving both a first wire electrode and a second wire electrode disposed in the circumferential groove between the first drive roll and the second drive roll, and both the first wire electrode and the second wire electrode are offset from a concave bottom portion of the circumferential groove, and the concave bottom portion extends between sidewall portions of the circumferential groove; a welding torch including a contact tip having a first exit orifice for the first wire electrode and a second exit orifice for the second wire electrode, the first and second exit orifices being spaced apart such that a distance S is provided between the first and second wire electrodes, the distance S being configured to promote formation of a bridge droplet between the first and second wire electrodes during a deposition operation, the bridge droplet connecting the first and second wire electrodes before contacting a molten puddle during the deposition operation; 1. A welding or additive manufacturing system comprising:

11. 11. The welding or additive manufacturing system of claim 10, wherein both the first wire electrode and the second wire electrode are offset from a bottom portion of the circumferential groove, the bottom portion extending between sidewall portions of the circumferential groove, and the bottom portion and sidewall portions are trapezoidal in shape.

12. 11. The welding or additive manufacturing system of claim 10, wherein the distance S is measured as the separation between the nearest edges of the first and second wire electrodes and is in the range of 1.5 to 3.5 mm.

13. 11. The welding or additive manufacturing system of claim 10, wherein the distance S is measured as the separation between the nearest edges of the first and second wire electrodes and is in the range of 2 to 3 mm.

14. 11. The welding or additive manufacturing system of claim 10, wherein the distance S is measured as the separation between the nearest edges of the first wire electrode and the second wire electrode and is in the range of 0.25 to 2.25 times the largest diameter of either the first wire electrode or the second wire electrode.

15. 11. The welding or additive manufacturing system of claim 10, wherein the distance S is measured as the separation between the nearest edges of the first wire electrode and the second wire electrode and is in the range of 2.5 to 3.5 times the largest diameter of either the first wire electrode or the second wire electrode.

16. 11. The welding or additive manufacturing system of claim 10, further comprising a sensor device that generates a signal or data corresponding to a consumed or remaining amount of one or both of the first wire electrode and the second wire electrode.

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