Arc erosion resistant nozzle for plasma arc material processing system

Abstract

A nozzle for an air-cooled plasma arc torch is provided. The nozzle includes a nozzle body formed of a first metal. The nozzle body includes a proximal portion and a distal portion extending along a longitudinal axis. The distal portion of the nozzle body includes a first orifice. The nozzle also includes an arc transition member formed of a second metal. The arc transition member is coupled to the distal portion of the nozzle body and includes a second orifice configured to substantially align with the first orifice when the arc transition member is coupled to the nozzle body. The second metal of the arc transition component includes a noble metal, and the second metal is different from the first metal.

Description

Technical Field

[0001] The present invention relates generally to a nozzle for an air-cooled plasma arc treatment system, wherein the nozzle is configured to resist arc erosion. Background Technology

[0002] Material handling equipment such as plasma arc welding torches and lasers are widely used for heating, cutting, planing, and marking metallic materials known as workpieces. For example, a plasma arc welding torch typically includes a torch body, consumables (such as welding electrodes and nozzles with a central outlet orifice mounted within the torch body), electrical connections, and channels for cooling and arc control fluids (e.g., plasma gas). Optionally, vortex rings are used to control the fluid flow pattern within the plasma chamber formed between the welding electrode and the nozzle. In some plasma arc welding torches, retaining caps may be used to hold the nozzle and / or vortex rings within the torch body. The gas used in the torch can be non-oxidizing (e.g., argon or nitrogen) or oxidizing (e.g., oxygen or air). The plasma arc welding torch is configured to generate a plasma arc, which is a compressed ionized jet of plasma gas with high temperature and high momentum.

[0003] One method for generating a plasma arc in a plasma arc welding torch is the contact initiation method. The contact initiation method involves establishing physical contact and electrical connection between the welding electrode and the nozzle to form a current path between them. The welding electrode, eddy current ring, and nozzle can be coupled to form a plasma chamber within the torch body. Current is supplied to the welding electrode and the nozzle, and a process gas is introduced into the plasma chamber. The pressure of the process gas accumulates until it is sufficient to separate the welding electrode and the nozzle. This separation results in the formation of an arc between the welding electrode and the nozzle within the plasma chamber. Hereinafter, this plasma arc is referred to as a pilot arc, and the torch operation in which the arc is attached to the nozzle is referred to as the pilot arc mode. The pilot arc ionizes the introduced process gas to generate a plasma jet, which can be transferred to the workpiece for material handling. Hereinafter, this plasma arc is referred to as a transfer arc, and the torch operation in which the plasma arc is transferred is referred to as the transfer arc mode. In some applications, the power supply connected to the plasma arc welding torch is adapted to provide a first current, known as the pilot current, during the generation of the arc in pilot arc mode, and a second current, known as the transfer arc current, after the plasma jet has been transferred to the workpiece in transfer arc mode.

[0004] If a conventional plasma arc welding torch is used for an extended period in guided arc mode (e.g., where the guided arc extends from the electrode to the nozzle rather than to the workpiece), the torch may degrade rapidly. Guided arc mode is used in a variety of situations, including the start-up phase of a plasma treatment operation, providing light in a dark space, intermittent cutting operations, cutting uneven surfaces, etc. Guided arc discharge can significantly reduce the lifespan of the nozzle in a plasma arc welding torch. More specifically, during the guided arc mode used to operate a plasma arc welding torch (e.g., each time the torch is started), a guided arc is formed between the electrode and the inner surface of the nozzle surrounding the nozzle exit orifice. The guided arc then rapidly passes through the nozzle exit orifice and remains attached to the outer surface of the nozzle surrounding the nozzle exit orifice. During this period and before the arc is transferred to the workpiece, the guided arc current and oxygen in the treatment gas cause rapid wear on the nozzle around the exit of the nozzle exit orifice. This nozzle wear reduces the cutting capability of the torch and severely limits consumable life.

[0005] In some cases, the nozzle is encapsulated with one or more other welding torch consumable components (including welding electrodes, eddy current rings, and / or shields) to form a cylinder. The assembly of consumable components within the cylinder may not be usable or servicable individually. While the introduction and adoption of cylinders in plasma arc welding torches has driven a wave of innovation in the plasma arc cutting field and created more robust solutions and products for end users, a drawback is that using cylinders combined with standard nozzles (e.g., all-copper nozzles) in high-guided arc applications can lead to high consumable costs because operators cannot selectively replace only parts nearing the end of their lifespan / that have failed; instead, the entire cylinder must be replaced. That is, a failure in one component of the cylinder (such as the nozzle) means the entire cylinder becomes unusable. Therefore, in practice, for applications with long guided arc times, it is necessary to replace the nozzle and / or the entire consumable cylinder well before other consumables (e.g., welding electrodes) have reached the end of their lifespan.

[0006] Recently, plasma arc treatment systems have been integrated into robotic manufacturing cells to perform various operations, such as deburring aluminum castings. The variability and continuity of burr location require the plasma arc torch in robotic manufacturing systems to maintain a continuous guiding arc over the workpiece contour where burrs may occur, regardless of their presence. As the torch passes near the burr, the plasma arc is adapted to transfer to the workpiece to begin cutting and removing the burr from the casting. This operation is effective for deburring, but results in significant guiding arc (i.e., non-transfer arc) operation time for the plasma consumable, which significantly shortens consumable life because the arc terminal (anode) continuously transitions between the nozzle (in guiding arc mode) when burrs are absent and the workpiece (transfer arc) when burrs are present. Furthermore, due to limitations in part variation and robot motion control, these applications benefit from increased torch spacing (i.e., increased torch-to-workpiece distance) to avoid torch collisions. However, this preference exacerbates nozzle wear and further reduces the lifespan of nozzles, other welding torch consumables, and / or barrels. Furthermore, consumables used in robotic manufacturing applications (e.g., nozzles) are particularly sensitive to cutting life, as replacing old consumables with new ones requires shutting down one or more robot units, resulting in production losses.

[0007] Generally, long lead-out arc times can lead to premature nozzle wear and a lower overall consumable cartridge life, thus increasing consumable costs. Examples of applications requiring significant lead-out arc times, as described above, include, but are not limited to, robotic applications where operators use a welding torch as a light source, where workpiece edge positioning is inaccurate and / or unpredictable, grate cutting, robotic aluminum casting cutting, and trimming operations, where the average lead-out arc time per start-up can be 5 to 10 times that of conventional cutting table applications. For example, in robotic applications where cartridges are mounted inside a plasma arc welding torch, less than 1% of cartridges are used up due to electrode blowout. Conversely, in many cases, the vast majority of cartridges are replaced due to premature nozzle wear. This need for premature cartridge replacement limits the advantages of cartridge use. In applications where consumables are replaceable individually (i.e., not part of the cartridge), customers can use up to two nozzles per electrode.

[0008] Therefore, systems and methods are needed to reduce nozzle wear caused by guided arc discharge in plasma arc treatment systems without compromising treatment performance. Summary of the Invention

[0009] The invention features a multi-material composite nozzle configured to reduce guided arc erosion. In one aspect, a nozzle for an air-cooled plasma arc welding torch is provided. The nozzle includes a nozzle body formed of a first metal. The nozzle body includes a proximal portion and a distal portion extending along a longitudinal axis. The distal portion of the nozzle body includes a first orifice. The nozzle also includes an arc transition member formed of a second metal. The arc transition member is coupled to the distal portion of the nozzle body and includes a second orifice configured to substantially align with the first orifice when the arc transition member is coupled to the nozzle body. The second metal of the arc transition member comprises a noble metal and is different from the first metal.

[0010] On the other hand, a consumable cartridge for an air-cooled plasma arc welding torch is provided. The consumable cartridge includes a composite nozzle comprising a nozzle body formed of a first metal and an arc transition member formed of a second metal different from the first metal. The arc transition member is coupled to a distal end of the nozzle body along the longitudinal axis of the nozzle. The consumable cartridge also includes a welding electrode disposed within a portion of the nozzle, a vortex ring disposed around the welding electrode and fixedly connected to the nozzle, and a data storage device disposed within the consumable cartridge. The data storage device includes instructions for adjusting one or more operating parameters of the plasma arc welding torch based on the thickness of the arc transition member along the longitudinal axis.

[0011] In another aspect, a computer-implemented method for automatically operating an air-cooled plasma arc welding torch is provided. The method includes: causing the plasma arc welding torch to generate a first pilot arc by a computing device; moving the plasma arc welding torch to a position close to a workpiece by the computing device, such that the first pilot arc is transferred to the workpiece to form a transfer arc; and causing the plasma arc welding torch to process the workpiece using the transfer arc by the computing device. The method further includes moving the plasma arc welding torch to a second position away from the workpiece by the computing device, such that the transfer arc transitions from the workpiece back to the plasma arc welding torch to form a second pilot arc. The second pilot arc is adapted to be attached to an arc transition member disposed at the distal end of the nozzle of the plasma arc welding torch, the arc transition member comprising a precious metal. The method further includes maintaining the second pilot arc of the plasma arc welding torch by the computing device for at least about 3 seconds. In some embodiments, the second pilot arc of the plasma arc welding torch is maintained for about 5 seconds, and may be maintained for up to about 20 seconds.

[0012] In some embodiments, the method further includes receiving data from a computing device for controlling the plasma arc welding torch and data for parts to be processed by the plasma arc welding torch from the workpiece. In some embodiments, the method further includes having the computing device cause the plasma arc welding torch to repeatedly generate a sequence of a first pilot arc, a transfer arc, and a second pilot arc at multiple locations on the workpiece without the plasma arc being extinguished.

[0013] In another aspect, a computer-implemented method is provided for operating a plasma arc welding torch on a dressing robot in a plasma arc processing system. The method includes receiving data from a computing device for a desired part to be processed from a workpiece and data for the plasma arc welding torch. The plasma arc welding torch includes a composite nozzle comprising a nozzle body coupled to an arc transition member made of a material including precious metals. The arc transition member is disposed at a distal end of the nozzle body. The method further includes: the computing device causing the plasma arc welding torch to generate a guiding arc; and the computing device actuating the plasma arc welding torch via the dressing robot to track a path relative to the workpiece based on workpiece data without piercing the workpiece, while the plasma arc welding torch maintains the guiding arc. The method further includes: the computing device moving the plasma arc welding torch close to the workpiece, such that the guiding arc is transferred to the workpiece to form a transfer arc for processing the workpiece; and the computing device reattaching the transfer arc to the plasma arc welding torch at the arc transition member of the plasma arc welding torch to reform the guiding arc.

[0014] In some embodiments, reattaching the transfer arc to the plasma arc welding torch includes moving the plasma arc welding torch away from the workpiece to eliminate proximity to the workpiece. In some embodiments, the method further includes automatically sensing proximity between the plasma arc welding torch and the workpiece, such that once proximity is achieved, a transfer arc is automatically established between the plasma arc welding torch and the workpiece. In some embodiments, the method further includes maintaining a pilot arc by the plasma arc welding torch for at least about 5 seconds while the plasma arc welding torch tracks a path relative to the workpiece without piercing it. In some embodiments, the method further includes repeatedly switching between generating a pilot arc and a transfer arc by the plasma arc welding torch for at least 90 seconds without the plasma arc extinguishing. In some embodiments, the transfer arc treats the workpiece by piercing it to trim casting burrs from the workpiece.

[0015] In another aspect, a method for manufacturing a nozzle for an air-cooled plasma arc welding torch is provided. The method includes forming a nozzle body from a first metal. The nozzle body includes a proximal portion and a distal portion extending along a longitudinal axis. The distal portion of the nozzle body includes a first orifice. The method also includes forming an arc transition member from a second metal. The arc transition member includes a second orifice. The second metal of the arc transition member includes a noble metal, and the second metal is different from the first metal. The method further includes coupling the arc transition member to the distal portion of the nozzle body such that the second orifice is substantially aligned with the first orifice.

[0016] Any of the foregoing aspects may include one or more of the following features. In some embodiments, the arc transition component is disposed on the nozzle body of the nozzle, and the arc transition component and the nozzle body are formed of different materials. In some embodiments, the second metal of the arc transition component comprises a noble metal. In some embodiments, the noble metal of the arc transition component is silver. In some embodiments, the noble metal of the arc transition component is gold. In some embodiments, the second metal of the arc transition component comprises at least about 45% silver. For example, the second metal of the arc transition component comprises at least about 85% silver. In some embodiments, the second metal of the arc transition component is a silver alloy. In some embodiments, the silver alloy is silver-nickel. In some embodiments, the silver alloy is silver-tin oxide. In some embodiments, the silver alloy is silver-tungsten oxide. In some embodiments, the material of the nozzle body is copper.

[0017] In some embodiments, the arc transition component reduces oxidation of the nozzle caused by plasma arc attachment, thereby extending the duration of one or more pilot arc operations of the plasma arc welding torch. In some embodiments, the arc transition component includes an outer surface comprising a location where plasma arc attachment occurs to transition between the transfer plasma arc and the pilot arc. In some embodiments, the arc transition component is coupled to an end face of a distal portion of the nozzle body. The arc transition component may extend from the end face within the distal portion of the nozzle body.

[0018] In some embodiments, the arc transition component is mounted to the distal portion of the nozzle body by at least one of the following methods: brazing, metallurgical bonding, stamping, friction welding, forging, ultrasonic welding, or pressure fitting. In some embodiments, the arc transition component has a washer-like shape. In some embodiments, the arc transition component includes a coating on at least one of the end face of the distal portion of the nozzle body, the inner surface of the first orifice, or the inner surface of the second orifice.

[0019] In some embodiments, the thickness of the arc transition component along the longitudinal axis of the nozzle is between about 0.005 inches and about 0.15 inches. For example, the thickness is about 0.06 inches. In some embodiments, the diameter of the end face of the arc transition component is approximately equal to or smaller than the diameter of the end face of the distal portion of the nozzle body.

[0020] In some embodiments, the nozzle is configured as part of a consumable cartridge mounted within a plasma arc welding torch. In some embodiments, the consumable cartridge includes a data storage device configured to store instructions for adjusting one or more operating parameters of the plasma arc welding torch based on the thickness of the arc transition component. In some embodiments, the one or more operating parameters include a guide curve. In some embodiments, the one or more operating parameters include at least one of the following: gas pressure, gas selection, process identification, cutting speed, ampere number, guide curve, ramp curve, or system compensation taking into account usage conditions. In some embodiments, the data storage device is an RFID tag or a security chip.

[0021] In some embodiments, the nozzle is configured to operate at a current level below about 140 amperes. In some embodiments, the nozzle includes a contact actuation surface disposed on an inner surface of a proximal portion of the nozzle body. The contact actuation surface is configured to contact a welding electrode during arc generation. In some embodiments, the welding electrode is a contact-activated welding electrode configured to contact the nozzle during the initiation of the guiding arc. In some embodiments, the welding electrode is disposed within the nozzle body.

[0022] In some implementations, the plasma arc welding torch is mounted on a robotic arm controlled by a computing device.

[0023] It should also be understood that various aspects and embodiments of the present invention can be combined in various ways. Based on the teachings of this specification, those skilled in the art can readily determine how to combine these different embodiments. For example, in some embodiments, any aspect of the above may include one or more of the features described above. One embodiment of the present invention may provide all of the above features and advantages. Attached Figure Description

[0024] The advantages of the invention described above, and further advantages thereof, can be better understood by referring to the following description taken in conjunction with the accompanying drawings. The drawings are not necessarily drawn to scale, but generally focus on illustrating the principles of the invention.

[0025] Figure 1 An exemplary nozzle configured for installation in a plasma arc welding torch is shown according to some embodiments of the present invention.

[0026] Figure 2 Some embodiments of the present invention are shown. Figure 1 An exemplary exploded view of the nozzle.

[0027] Figure 3 Some embodiments of the present invention are shown. Figure 1 and Figure 2 A perspective view of the assembled nozzle.

[0028] Figure 4 A cross-sectional view is shown of another exemplary nozzle configured for installation in a plasma arc welding torch according to some embodiments of the present invention.

[0029] Figure 5 Some embodiments of the present invention are shown. Figure 4 A perspective view of the nozzle.

[0030] Figure 6 Combinations according to some embodiments of the present invention are shown. Figure 4 and Figure 5 An exemplary consumable cartridge for a nozzle.

[0031] Figure 7 An exemplary plasma arc treatment system with a plasma arc welding torch according to some embodiments of the present invention is shown, the plasma arc welding torch being combined with... Figures 1 to 3 nozzle or Figure 4 and Figure 5 The nozzle.

[0032] Figures 8a to 8d Conventional nozzles and embodiments according to the present invention are shown. Figures 1 to 3 A comparison of the performance of nozzles after different periods of use.

[0033] Figure 9 The invention illustrates some embodiments thereof. Figure 7 An exemplary computer-implemented process for automating the operation of a plasma arc welding torch in a plasma arc treatment system. Detailed Implementation

[0034] Figure 1An exemplary nozzle 100 configured for mounting in a plasma arc welding torch according to some embodiments of the invention is shown. The plasma arc welding torch may be an air-cooled contact-start plasma arc welding torch. Alternatively, the plasma arc welding torch may be cooled by one or more of air or a liquid coolant (e.g., water) and may optionally have a high-frequency starting mechanism. As shown, the nozzle 100 includes a nozzle body 102 having a proximal portion 104 and a distal portion 106 extending along a longitudinal axis A. The distal portion 106 is generally defined as the section of the nozzle body 102 closest to the workpiece during torch operation, and the proximal portion 104 is positioned relative to the distal portion 106 along the longitudinal axis A. The distal portion 106 includes an orifice 108. A contact-start surface 109 is disposed on the inner surface of the nozzle body 102 near the distal portion 106, wherein the contact-start surface 109 is configured to physically contact a welding electrode (not shown) during plasma arc generation. The nozzle 100 also includes an arc transition member 110 configured to be coupled to a distal portion 106 of the nozzle body 102. For example, the arc transition member 110 may be coupled to an end face 116 of the distal portion 106 of the nozzle body 102. The arc transition member 110 also includes an orifice 112 configured to be substantially aligned with an orifice 108 of the nozzle body 102 when the arc transition member 110 is coupled to the nozzle body 102.

[0035] In some embodiments, the material of the arc transition component 110 is selected to minimize arc erosion. This material is conductive, does not form easily flaking oxides, facilitates rapid arc movement to dissipate heat, and minimizes arc erosion. In some embodiments, both the nozzle body 102 and the arc transition component 110 are made of metal (i.e., conductive material), but the metal of the nozzle body 102 is different from the metal of the arc transition component 110. In some embodiments, the metal of the arc transition component 110 includes precious metals such as silver or gold. In some embodiments, the metal of the arc transition component 110 is an arc-resistant alloy or composite material, such as a precious metal-based alloy or composite material. For example, the arc transition component 110 may be a silver alloy / composite material, such as silver-nickel (Ag / Ni) (e.g., about 90% silver and about 10% nickel, or about 85% silver and about 15% nickel), silver-cadmium oxide (Ag / CdO), silver-tin oxide (Ag / SnO2) (e.g., about 88% silver and about 12% tin oxide, or about 86% silver and about 14% tin oxide), silver-molybdenum (Ag / Mo), silver-tungsten (Ag / W), silver-tungsten oxide, silver-graphite (Ag / C), powder metallurgy silver-tin oxide doped with tungsten oxide (Ag / SnO2 / SPW4), silver-tungsten graphite (Ag / W / C), or silver-tungsten graphite with tungsten oxide (Ag / W / C / SPW4). In some embodiments, the arc transition component 110 comprises at least about 45% precious metals, such as at least about 45% silver, about 80% silver, or about 85% silver. In some embodiments, the metal of the arc transition component 110 is a pure precious metal. Including a precious metal material near (e.g., on) the end of the nozzle 100 is suitable for increasing the operational life of the nozzle 100, as well as increasing the long-term cutting accuracy and precision of the welding torch consumables. In some embodiments, the metal of the arc transition component 110 is titanium or includes titanium. In some embodiments, the metal of the nozzle body 102 is copper or a copper alloy. In some embodiments, the nozzle body 102 and the arc transition component 110 are made of the same metal, such as a metal including precious metals (e.g., silver, gold, or silver-nickel). In some embodiments, the nozzle 100 is a single / integral component made of a single material including precious metals (e.g., silver alloy / composite material).

[0036] In some embodiments, different materials are selected for the arc transition component 110 to combat the wear of different plasma arc welding torches and / or operations, as they may degrade the nozzle in different ways. For example, a plasma arc welding torch with high gas flow rate and high pilot current may benefit from an arc transition component 110 made of a low-arc erosion material (e.g., pure silver or a silver-cadmium alloy) compared to a plasma arc welding torch with low gas flow rate and low pilot current that may benefit from an arc transition component 110 made of a material with low arc erosion (e.g., pure silver or a silver-cadmium alloy). High arc flow rate is desirable because it allows the plasma arc to attach at different locations around the nozzle orifice to distribute the heat load. Thus, these multiple attachment points prevent the plasma arc from eroding a particular nozzle location. In some embodiments, the nozzle 100 is configured to operate at a current level below about 140 amperes.

[0037] In addition to the material composition, the position of the arc transition component 110 within the nozzle 100 can be selected to reduce oxidation of the nozzle 100 caused by plasma arc attachment, thereby extending the duration of one or more guide arc operations of the plasma arc welding torch and extending the nozzle's lifespan. More specifically, such as Figure 1 As shown, an arc transition member 110, comprising an arc erosion resistant material (e.g., a noble metal-based alloy), is positioned near the distal portion 106 of the nozzle body 102 (e.g., a portion defining the distal end of the nozzle 100) at a location where the arc may terminate during the pilot arc mode and cause erosion of the nozzle. Specifically, the arc transition member 110 may include an outer surface 114 that forms a location (i.e., the anode) where plasma arc attachment occurs to transition between the transfer plasma arc and the pilot arc during torch operation. This arc attachment can cause the outer surface 114 to heat to temperatures exceeding approximately 550 degrees Celsius. Therefore, selecting a suitable material to form the arc transition member 110 can provide arc erosion / wear resistance at this location during torch operation. Furthermore, the arc erosion / wear resistant material of the arc transition member 110 is adapted to line a portion of the orifice of the nozzle 100, which further improves arc durability. In general, the arc transition component 110 disposed in and / or around the orifice 108 of the nozzle body 102 is adapted to improve heat conduction from the orifice 108 and / or reduce oxidation of the nozzle 100 caused by arc attachment, especially during guided arc operation.

[0038] As described above, Figure 1The multi-material nozzle 100 is a composite material of a nozzle body 102 and an arc transition component 110, wherein two or more different metals (e.g., a copper and silver alloy) are joined together. In some embodiments, the arc transition component 110 is mounted to the distal portion 106 of the nozzle body 102 by at least one of the following methods: brazing, metallurgical bonding, stamping, forging, friction welding, induction welding, ultrasonic welding, or pressure fitting, press fitting, or pressing and diffusion. In some embodiments, the arc transition component 110 has a washer-like shape, wherein an orifice 112 extends through the center of the washer, such as... Figure 1 As shown. In some embodiments, the arc transition member 110 is applied as a coating to at least one of the end face 116 of the distal portion 106 of the nozzle body 102 or the inner surface of the orifice 108 of the nozzle body 102. In some embodiments, the thickness 118 of the arc transition member 110 along the longitudinal axis A of the nozzle 100 is between about 0.005 inches and about 0.15 inches. For example, the thickness 118 may be about 0.06 inches. In some embodiments, the diameter of the outer surface 114 of the arc transition member 110 is approximately equal to or smaller than the diameter of the end face 116 of the distal portion 106 of the nozzle body 102.

[0039] Figure 2 Some embodiments of the present invention are shown. Figure 1 An exemplary exploded view of nozzle 100. Nozzle body 102 may be machined from a metal (such as copper), through which a central orifice 108 extends. Arc transition member 110 may be formed in the shape of a washer, through which a central orifice 112 extends. Arc transition member 110 may be manufactured by stamping / machining from any of the aforementioned materials (e.g., silver-based materials / alloys) different from the material of nozzle body 102 (e.g., copper). Arc transition member 110 is then coupled to the end face 116 of the distal portion 106 of nozzle body 102, which is typically attached with a guiding arc, while the two orifices 108, 112 are substantially aligned. Arc transition member 110 may be brazed to nozzle body 102 for a fixed attachment. In some embodiments, arc transition member 110 includes built-in brazing material. In some embodiments, brazing is performed in an argon atmosphere at approximately 75% power for approximately 25 seconds. In some implementations, brazing is performed in air or in an inert or hydrogen atmosphere at a temperature between about 651 degrees Celsius and about 895 degrees Celsius.

[0040] Figure 3 Some embodiments of the present invention are shown. Figure 1 and Figure 2A perspective view of the assembled nozzle 100. As shown, an arc transition component 110 is disposed at the end face 116 of the distal portion 106 of the nozzle body 102, and its profile is complementary to the shape of the distal portion 106. The composite material of the arc transition component 110 and the nozzle body 102 is suitable for forming the nozzle 100 of an air-cooled plasma arc welding torch.

[0041] Figure 4 and Figure 5 Cross-sectional and perspective views of another exemplary nozzle 300 configured for installation in a plasma arc welding torch, according to some embodiments of the present invention, are shown respectively. Figure 4 and Figure 5 The nozzle 300 is structurally and compositionally similar to... Figures 1 to 3 This is similar to the multi-material composite nozzle 100. As shown, nozzle 300 includes a nozzle body 302, which includes a proximal portion 304 and a distal portion 306 extending along a longitudinal axis A. The distal portion 306 of nozzle body 302 includes an orifice 308. A contact actuation surface 309 is disposed on the inner surface of nozzle body 302 near the distal portion 306. Nozzle body 302 may have the same material composition as nozzle body 102 of nozzle 100, such as copper or a copper alloy. Nozzle 300 also includes an arc transition member 310, which is configured to be coupled to the distal portion 306 of nozzle body 302. As shown, arc transition member 310 may be disposed within a cavity 320 machined from the end face 316 of distal portion 306 of nozzle body 302 into nozzle body 302. The arc transition component 310 also includes an orifice 312 configured to substantially align with the orifice 308 of the nozzle body 302 when the arc transition component 310 is coupled to the nozzle body 302.

[0042] In some embodiments, the arc transition member 310 is coupled to the nozzle body 302 by pressing and / or crimping into the cavity 320. In some embodiments, the arc transition member 310 has the same material composition as the arc transition member 110 of the nozzle 100 described above, such as a material including precious metals (e.g., silver or a silver alloy). In some embodiments, the thickness 318 of the arc transition member 310 along its longitudinal axis is substantially the same as the thickness 118 of the arc transition member 110 of the nozzle 100 (e.g., between about 0.005 inches and about 0.15 inches). Figure 4 and Figure 5 In the nozzle configuration, the outer surface 314 of the arc transition member 310 is substantially aligned / flush with the end face 316 of the nozzle body 302. The diameter of the outer surface 314 of the arc transition member 310 may be smaller than the diameter of the end face 316 of the distal portion 306 of the nozzle body 302.

[0043] On the other hand, Figures 1 to 3 Nozzle 100 or Figure 4 and Figure 5 The nozzle 300 can form part of the consumable cartridge of a plasma arc welding torch, wherein the cartridge comprises two or more consumable components packaged as a single unit. The consumable cartridge is defined herein as a single-piece component, wherein the components of the cartridge are not individually repairable or usable. Therefore, if a component of the consumable cartridge needs to be replaced, the entire cartridge is replaced. In some embodiments, the consumable cartridge is a “single-use” cartridge, wherein the cartridge is replaced by the operator after any of its components has reached the end of its service life, rather than repairing and replacing individual components as in conventional welding torch designs. Since the use of multi-material composite nozzles 100 or 300 generally extends nozzle life compared to conventional nozzles, as stated above, incorporating such a nozzle design into the consumable cartridge is suitable for improving cartridge life and cut quality. Figure 6 Combinations according to some embodiments of the present invention are shown. Figure 4 and Figure 5 An exemplary consumable cartridge 200 for a multi-material composite nozzle 300. In an alternative embodiment, the cartridge 200 is readily configured to combine... Figures 1 to 3 The multi-material composite nozzle 100 is shown. The consumable cartridge 200 also includes a welding electrode 202 disposed within a portion of the internal region of the nozzle body 102 or 302 of the nozzle 300. Furthermore, the consumable cartridge 200 includes a vortex ring 204 disposed around the outer surface of the welding electrode 202 and fixedly connected to the nozzle 300. The welding electrode 202 may be a contact-activated welding electrode adapted to physically contact the internal contact-activated surface 309 of the nozzle body 302 during the initiation of the guiding arc.

[0044] Figure 7 An exemplary plasma arc processing system 500 with a plasma arc welding torch 502 according to some embodiments of the present invention is shown, the plasma arc welding torch being combined with 1 to Figure 3 Multi-material composite nozzle 100 or Figure 4 and Figure 5 A multi-material composite nozzle 300. The plasma arc welding torch 502 is an air-cooled contact-start plasma arc welding torch configured to operate in either a pilot arc mode (for initiating / igniting the plasma arc) or a transfer arc mode (for processing the workpiece by transferring the plasma arc to the workpiece). In some embodiments, the plasma arc welding torch 502 includes... Figure 6The consumable cartridge 200, in which nozzle 100 or 300 is part of cartridge 200 as described above. Alternatively, nozzle 100 or 300 may be mounted inside the welding torch 502 instead of being part of the consumable cartridge, in which case nozzle 100 or 300 is individually serviceable and replaceable. The plasma arc welding torch 502 may also include at least one data storage device 504 configured to store data (e.g., instructions) about nozzle 100 or 300, which can be used by the plasma arc welding torch system 500 to adjust one or more operating parameters of the plasma arc welding torch 502. Data storage device 504 may be a radio frequency identification (RFID) tag, a memory device, or a security chip (e.g., a printed circuit board embedded therein that processes data such as identification and operation data). Data storage device 504 may be disposed within or on the body of nozzle 100 or 300, or coupled to another consumable component inside the welding torch 502. If the cylinder 200 is installed inside the welding torch 502, the data storage device 504 can be incorporated into the cylinder 200 together with the nozzle 100 or 300.

[0045] In some embodiments, data storage device 504 is electrically connected to a computer digital controller (CNC) 506 of the plasma arc material handling system 500, wherein the CNC 506 is configured to automatically control the operation of the plasma arc welding torch 502. Data from data storage device 504 can be electrically transmitted to the CNC 506. For example, if data storage device 504 is an RFID tag, the plasma arc handling system 500 may include an RFID reader (not shown) configured to receive data in the form of a radio frequency signal from data storage device 504. Nozzle data stored in storage device 504 may include at least one of the following: for example, the thickness 118 or 318 of the arc transition portion 110 or 310 of nozzle 100 or 300, or the type / composition of nozzle 100 or 300. In some embodiments, if, for example, no data storage device is present in system 500, the CNC 506 may receive nozzle data via input from an operator. Based on nozzle data, the CNC 506 can send control commands to the power supply 508 of the plasma arc treatment system 500 to operate the plasma arc welding torch 502 under conditions specific to nozzle 100 or 300 and / or cylinder 200 (if the cylinder is installed inside the welding torch 502). These control commands may include settings for one or more operating parameters, including at least one of the following: gas pressure, gas selection, process identification, cutting speed, ampere, guide curve, ramp curve, spacing distance, or system compensation considering usage conditions. For example, the value of the "expected guide life" parameter (representing the guide curve) for the plasma arc welding torch 502 can be automatically set by the CNC 506 based on the type of nozzle incorporated in the cylinder. For a cylinder with a standard nozzle (e.g., made of a single metal), the expected guide life can be set to 5 minutes. In contrast, for a cylinder with a multi-material composite nozzle 100 or 300, the expected guide life is approximately 5 to 10 times that of a standard nozzle. During torch operation, if the duration of the guiding operation is significantly shorter than the expected guide life, this indicates to the operator that nozzle 100 or 300 (or cylinder 200 if it is installed inside torch 502) is operable. However, if the duration of the guiding operation is closer to or greater than the expected guide life, this indicates to the operator that nozzle 100 or 300 (or cylinder 200 if it is installed inside torch 502) needs to be replaced to obtain optimal cutting performance. In other exemplary configurations, the nozzle may have an alloy composition designed / selected for one or more of higher spacing, higher current and / or gas flow rates, or lower current and / or gas flow rates. The nozzle ID may also drive these selections. As another example, the CNC 506 may linearly increase the guide life with the thickness 118 or 318 of the arc transition component 110 or 310.For example, if the arc transition component 110 or 310 has a thickness of approximately 0.060 inches (118 or 318), this provides approximately 5 to 10 times the guide life of a conventional single-material nozzle. If the arc transition component 110 or 310 has a thickness of approximately 0.0120 inches (118 or 318), this would increase the guide life by another 3 to 5 times.

[0046] Will Figures 1 to 3 Multi-material composite nozzle 100 or Figure 4 and Figure 5 The multi-material composite nozzle 300 is incorporated into the plasma arc welding torch (e.g., Figure 7 Inside the welding torch 502, as a consumable cartridge (e.g., Figure 6 As part of the consumable cartridge 200 or as a separate consumable, the nozzle 100 or 300 is suitable for increasing the cutting life of the welding torch due to its arc erosion resistance. This type of torch design is particularly valuable in robotic applications where the guiding arc is used as a sensor to detect and / or respond to the presence of material to cut and quickly transition to a transfer arc. This nozzle design can significantly improve productivity by reducing downtime for consumable replacement and minimizing poor cut quality. Figures 8a to 8d A conventional nozzle 600 according to some embodiments of the present invention is shown. Figure 1 A performance comparison of the multi-material composite nozzle 100 after different usage periods. Specifically, Figure 8a and Figure 8b The distal portions of a conventional nozzle 600 are shown after approximately 6 minutes and 12 minutes of operation in guided arc mode. The conventional nozzle 600 is constructed from a single copper material. The average depth of the pits formed on the conventional nozzle 600 after approximately 6 minutes of guided operation is shown (e.g., Figure 8a The indentation depth (as shown) is approximately 0.032 inches, and after approximately 12 minutes of guided operation, the average depth of the indentation in a conventional nozzle 600 (as shown) is... Figure 8b (As shown) is approximately 0.044 inches. In comparison, Figure 8c and Figure 8d The distal portions of the composite nozzle 100 are shown after approximately 30 minutes and 60 minutes of operation in guided arc mode, respectively, with average pit depths of approximately 0.019 inches and 0.030 inches, respectively. Therefore, the multi-material composite nozzle 100 reduces pitting and / or erosion on the arc-attached nozzle end face 114, thereby increasing nozzle life by 3, 4, or even 5 times compared to a standard all-copper nozzle 600. More specifically, the use of an arc transition element 110 in the nozzle 100 improves consumable life and cut quality. Furthermore, Figure 4 and Figure 5 The composite nozzle design 300 has superior performance compared to traditional nozzles, similar to the performance of nozzle 100.

[0047] Figure 9 The invention illustrates some embodiments thereof. Figure 5 An exemplary computer-implemented process 700 of the plasma arc treatment system 500 for automatically operating an air-cooled plasma arc welding torch 502 (e.g., in robot operation). Figures 1 to 3 Multi-material composite nozzle 100 or Figure 4 and Figure 5 The multi-material composite nozzle 300 can be installed inside the welding torch 502, for example, as a consumable cartridge (e.g., Figure 6 The plasma arc welding torch 502 is either part of the tube 200 or a separate component. In some embodiments, the plasma arc welding torch 502 is mounted on a robotic arm (not shown) of the plasma arc processing system 500, which is operated by a CNC 506. Figure 9 The process is controlled by 700.

[0048] As shown in the figure, at step 702 of process 700, the CNC 506 of the plasma arc treatment system 500 can actuate the welding torch 502 to generate a guiding arc in preparation for workpiece processing. At step 704, the CNC 506 can move the welding torch 502 to a position close to the workpiece, such that the guiding arc is adapted to transfer to the workpiece to form a transfer arc, which processes (e.g., cuts, chisels, or marks) the workpiece in step 706. In some embodiments, the transfer of the arc to the workpiece is automatic once the tip of the welding torch is sufficiently close (e.g., vertically or laterally) to the workpiece to establish a path of least resistance to the workpiece. After the desired processing is completed at this particular location, at step 708, the CNC 506 can move / translate the welding torch 502 to another position relative to the workpiece, where the welding torch 502 is away from the workpiece, such that the transfer arc transitions from the workpiece back to the plasma arc welding torch 502 to form another guiding arc. In some implementations, once the torch tip is sufficiently distanced from the workpiece such that the path of least resistance is the torch 502 itself, the transition of the arc back to the torch 502 is automatic. This distance can be achieved through at least one of the following operations: the CNC 506 lifts the torch 502 away from the workpiece; the CNC 506 moves the torch laterally along the workpiece so that the torch tip is away from the workpiece; and / or the torch 502 is positioned on the workpiece away from the torch (e.g., a hole or unevenness in the workpiece). As described above, this distance is suitable for attaching the guiding arc to the end face 114 or 314 of the arc transition component 110 or 310 of the nozzle 100 or 300. However, due to the material composition of the arc transition component 110 or 310 (e.g., containing precious metals such as silver), the nozzle 100 or 300 is less susceptible to arc abrasion / erosion compared to conventional nozzles. At step 710, CNC 506 is configured to maintain the pilot arc (from step 708) for a duration such as 3 seconds or longer (e.g., at least 5 seconds and / or up to about 20 seconds). In some embodiments, while maintaining the pilot arc, CNC 506 can repeat process 700 by moving the welding torch 502 to different locations on the workpiece and processing the workpiece at the new locations without extinguishing the plasma arc. Thus, the plasma arc welding torch 502 can be actuated to repeatedly generate a series of pilot and transfer arcs at multiple locations on the workpiece without extinguishing the plasma arc.

[0049] In some implementations, the CNC 506 uses at least one of the following data: data input by the operator or data received from a data storage device 504 disposed in the welding torch 502, as referenced above. Figure 7As described. The data may include data for the desired part to be processed from the workpiece, values ​​of various operating parameters for controlling the welding torch 502, and information that can be used by the CNC 506 to automatically adjust these operating parameters (e.g., the thickness of the arc transition part 110 or 310, the material composition of the nozzle 100 or 300, etc.).

[0050] In some implementation schemes, Figure 9Process 700 is tailored for casting trimming operations, in which case the robotic arm with the welding torch 502 mounted thereon can be a trimming robot. In an exemplary casting trimming operation, after an initial guiding arc is generated at step 702, the CNC 506 can actuate the welding torch 502 via the trimming robot to trace a desired path on the workpiece based on workpiece data. Tracing typically involves translating the welding torch 502 around the contour of the casting, outlining the desired shape that should be cast, during which the guiding arc generated by the welding torch is adapted to rapidly transfer to the workpiece as the guiding arc approaches, and to remove / trimme any unwanted burrs on the periphery of the desired part / casting via the transfer arc. The approach to the workpiece can be between about 0.05 inches and about 2.5 inches, such as between about 0.15 inches and about 1.5 inches, and more specifically, between about 0.4 inches and about 1.2 inches. In some embodiments, the approach distance for cutting operations is between about 0.01 inches and 2 inches. An exemplary height for cutting is approximately 0.06 inches to approximately 0.18 inches. An exemplary height for fine cutting is approximately 0.01 inches to approximately 0.06 inches. The approach distance for planing operations is between approximately 0.1 inches and approximately 4 inches. During tracking, the guiding arc can be maintained by the welding torch 502 for approximately 0 seconds to approximately 30 seconds (e.g., approximately 5 seconds) before extinguishing. In an exemplary operation, when the CNC 506 performs step 704 by moving the welding torch 502 to track the workpiece, the guiding arc is automatically transferred to the workpiece when the welding torch 502 approaches the workpiece (e.g., encountering an unwanted burr section) to form a transfer arc for processing the workpiece (step 706). More specifically, this processing, performed in the context of a trimming operation, involves the edge of the transfer arc beginning to trim casting burrs from the workpiece along the tracking path. The CNC 506 can sense the approach of the plasma arc welding torch 502 to the workpiece, such that once the approach is achieved, a transfer arc is automatically established between the plasma arc welding torch 502 and the workpiece. This can be achieved when the welding torch 502 is close enough to the workpiece that the arc automatically jumps to the workpiece to adjust its resistance path, in which case the guiding arc transitions into a transfer arc. As the CNC 506 continues to actuate the welding torch 502 to move / translate it over the workpiece along the tracking path, when the welding torch 502 encounters a section away from the workpiece (e.g., where there are no undesirable burrs below the workpiece), the proximity to the workpiece is eliminated, and the transfer arc is reattached to the plasma arc welding torch at the arc transition part 110 or 310 of the plasma arc welding torch 100 or 300, thereby reforming the guiding arc (step 708).In some embodiments, when the welding torch 502 is moved along a trajectory / path along the intended edge of the casting / desired part and there are no burrs, a move-away is achieved, in which case the arc becomes too far to reach the workpiece, causing the arc to retreat back to the nozzle, and the welding torch 502 automatically enters a guiding mode until the burrs are close enough for the arc to jump back to the workpiece. In some embodiments, the welding torch 502 repeatedly switches between generating a guiding arc and transferring an arc along the tracking path for at least 90 seconds without the plasma arc extinguishing, for casting finishing purposes (step 710). In some embodiments, the CNC 506 / power supply 508 automatically detects whether the welding torch is operating in transferring arc mode or guiding arc mode and can adjust the current and gas supplied to the welding torch 502 accordingly. In some embodiments, the system performs this mode detection based on the amount of current passing through the workpiece. For example, if the system senses that the current through the workpiece is approximately zero, it indicates that the welding torch 502 is in guiding arc mode. Conversely, if the system senses a current through the workpiece exceeding approximately 0.4 amperes, it indicates that the welding torch 502 is in arc transfer mode. If a guided arc mode is detected, the CNC 506 / power supply 508 can automatically reduce the gas and current supplied to the welding torch 502. Conversely, if an arc transfer mode is detected, the CNC 506 / power supply 508 can automatically increase the gas and current supplied to the welding torch 502.

[0051] It should be understood that various aspects and embodiments of the present invention can be combined in various ways. Based on the teachings of this specification, those skilled in the art can readily determine how to combine these different embodiments. Modifications may also arise in the minds of those skilled in the art after reading this specification.

Claims

1. A nozzle for an air-cooled plasma arc welding torch, the nozzle comprising: A nozzle body formed of a first metal, the nozzle body including a proximal portion and a distal portion extending along a longitudinal axis, wherein the distal portion of the nozzle body includes a first orifice; and An arc transition component, formed of a second metal, is coupled to the distal portion of the nozzle body and includes a second orifice configured to substantially align with a first orifice when the arc transition component is coupled to the nozzle body. The second metal of the arc transition component comprises a noble metal, and the second metal is different from the first metal.

2. The nozzle according to claim 1, wherein the precious metal of the arc transition component is silver.

3. The nozzle according to claim 1, wherein the precious metal of the arc transition component is gold.

4. The nozzle according to claim 2, wherein the second metal of the arc transition component is a silver alloy.

5. The nozzle of claim 1, wherein the second metal of the arc transition component comprises at least about 45% silver.

6. The nozzle of claim 5, wherein the second metal of the arc transition component comprises at least about 85% silver.

7. The nozzle according to claim 4, wherein the silver alloy is silver-nickel.

8. The nozzle according to claim 4, wherein the silver alloy is silver-tin oxide.

9. The nozzle according to claim 4, wherein the silver alloy is silver tungsten oxide.

10. The nozzle of claim 1, wherein the arc transition component reduces oxidation of the nozzle caused by plasma arc attachment, thereby extending the duration of one or more guide arc operations of the plasma arc welding torch.

11. The nozzle of claim 10, wherein the arc transition component includes an outer surface, the outer surface including a location where the plasma arc attaches to transition between a transfer plasma arc and a guiding arc.

12. The nozzle of claim 1, wherein the arc transition member is coupled to the end face of the distal portion of the nozzle body.

13. The nozzle of claim 12, wherein the arc transition member extends from the end face within the distal portion of the nozzle body.

14. The nozzle of claim 1, wherein the arc transition component is mounted to the distal portion of the nozzle body by at least one of the following methods: brazing, metallurgical bonding, stamping, friction welding, forging, ultrasonic welding, diffusion bonding, or pressure fitting.

15. The nozzle of claim 1, wherein the arc transition component has a washer-like shape.

16. The nozzle of claim 1, wherein the arc transition component comprises a coating on at least one of the end face of the distal portion of the nozzle body, the inner surface of the first orifice, or the inner surface of the second orifice.

17. The nozzle of claim 1, wherein the thickness of the arc transition component along the longitudinal axis of the nozzle is between about 0.005 inches and about 0.15 inches.

18. The nozzle of claim 17, wherein the thickness is about 0.06 inches.

19. The nozzle of claim 1, wherein the diameter of the end face of the arc transition member is approximately equal to or smaller than the diameter of the end face of the distal portion of the nozzle body.

20. The nozzle of claim 1, wherein the nozzle is configured as part of a consumable cartridge mounted in the plasma arc welding torch.

21. The nozzle of claim 20, wherein the consumable cartridge includes a data storage device configured to store instructions for adjusting one or more operating parameters of the plasma arc welding torch based on the thickness of the arc transition component.

22. The nozzle of claim 21, wherein the one or more operating parameters include a guide curve.

23. The nozzle of claim 1, wherein the nozzle is configured to operate at a current level below about 140 amperes.

24. The nozzle of claim 1, further comprising a contact actuation surface disposed on an inner surface of the nozzle body near the distal portion, the contact actuation surface being configured to contact the welding electrode during arc generation.

25. A consumable cartridge for an air-cooled plasma arc welding torch, the consumable cartridge comprising: A composite nozzle comprising a nozzle body formed of a first metal and an arc transition component formed of a second metal different from the first metal, the arc transition component being coupled to a distal end of the nozzle body along the longitudinal axis of the nozzle; A welding electrode, wherein the welding electrode is disposed within a portion of the nozzle; A vortex ring, which is disposed around the welding electrode and fixedly connected to the nozzle; and A data storage device disposed in the consumable cylinder, the data storage device including instructions for adjusting one or more operating parameters of the plasma arc welding torch based on the thickness of the arc transition component along the longitudinal axis.

26. The consumable cartridge of claim 25, wherein the one or more operating parameters include at least one of the following: gas pressure, gas selection, process identification, cutting speed, ampere, guide curve, ramp curve, or system compensation taking into account usage conditions.

27. The consumable cartridge of claim 25, wherein the welding electrode is a contact-activated welding electrode configured to contact the nozzle during the initiation of the guiding arc.

28. The consumable cartridge of claim 25, wherein the second metal of the arc transition component comprises a precious metal.

29. The consumable cartridge of claim 28, wherein the second metal of the arc transition component comprises at least about 45% silver.

30. The consumable cartridge of claim 25, wherein the data storage device is a radio frequency identification tag or a security chip.

31. The consumable cartridge of claim 25, wherein the thickness of the arc transition member along the longitudinal axis of the nozzle is between about 0.005 inches and about 0.15 inches.

32. The consumable cartridge according to claim 25, wherein the welding electrode is disposed within the nozzle body of the nozzle.

33. The consumable cartridge of claim 25, wherein the arc transition component includes a position where a plasma arc is attached to switch between a transfer plasma arc and a guiding arc.

34. A computer-implemented method for automatically operating a gas-cooled plasma arc welding torch, the method comprising: The computing device causes the plasma arc welding torch to generate a first guiding arc; The computing device moves the plasma arc welding torch to a position close to the workpiece, so that the first guiding arc is transferred to the workpiece to form a transfer arc; The computing device enables the plasma arc welding torch to process the workpiece using the transferred arc; The computing device moves the plasma arc welding torch to a second position away from the workpiece, such that the transfer arc transitions from the workpiece back to the plasma arc welding torch to form a second guiding arc, wherein the second guiding arc is adapted to attach to an arc transition component disposed on the distal end of the nozzle of the plasma arc welding torch, the arc transition component comprising a noble metal; and The computing device maintains the second guiding arc of the plasma arc welding torch for at least about 3 seconds.

35. The computer-implemented method of claim 34, further comprising receiving data from the computing device for controlling the plasma arc welding torch and data for parts to be processed from the workpiece by the plasma arc welding torch.

36. The computer-implemented method according to claim 34, further comprising the computing device causing the plasma arc welding torch to repeatedly generate a sequence of the first guiding arc, the transfer arc, and the second guiding arc at multiple locations on the workpiece without the plasma arc being extinguished.

37. The computer-implemented method of claim 34, wherein the arc transition component is disposed on the nozzle body of the nozzle, and the arc transition component and the nozzle body are formed of different materials.

38. The computer-implemented method of claim 37, wherein the noble metal of the arc transition component is silver.

39. The computer-implemented method according to claim 37, wherein the material of the arc transition component is a silver alloy.

40. The computer-implemented method of claim 37, wherein the material of the nozzle body is copper.

41. The computer-implemented method of claim 34, wherein the plasma arc welding torch is mounted on a robotic arm controlled by the computing device.

42. The computer-implemented method of claim 34, wherein the second guiding arc of the plasma arc welding torch is maintained for approximately 5 seconds.

43. A computer-implemented method for operating a plasma arc welding torch on a dressing robot in a plasma arc treatment system, the method comprising: The computing device receives data for the desired part to be processed from the workpiece and data for the plasma arc welding torch, wherein the plasma arc welding torch includes a composite nozzle, the composite nozzle including a nozzle body coupled to an arc transition component made of a material including precious metals, the arc transition component being disposed on a distal end of the nozzle body; The computing device causes the plasma arc welding torch to generate a guiding arc; The computing device actuates the plasma arc welding torch via the dressing robot to track the path relative to the workpiece based on workpiece data without piercing the workpiece, while the plasma arc welding torch maintains the guiding arc. The computing device moves the plasma arc welding torch close to the workpiece, so that the guiding arc is transferred to the workpiece to form a transfer arc for processing the workpiece; as well as The computing device causes the transfer arc to reattach to the plasma arc welding torch at the arc transition component of the plasma arc welding torch, so as to reform the guiding arc.

44. The computer-implemented method of claim 43, wherein reattaching the transfer arc to the plasma arc welding torch comprises moving the plasma arc welding torch away from the workpiece to eliminate proximity to the workpiece.

45. The computer-implemented method according to claim 43, further comprising automatically sensing the proximity of the plasma arc welding torch to the workpiece, such that once proximity is achieved, the transfer arc between the plasma arc welding torch and the workpiece is automatically established.

46. ​​The computer-implemented method of claim 43, wherein the transferred arc processes the workpiece by piercing it to trim casting burrs from the workpiece.

47. The computer-implemented method of claim 43, further comprising maintaining the guiding arc by the plasma arc welding torch for at least about 5 seconds while the plasma arc welding torch traces the path relative to the workpiece without piercing the workpiece.

48. The computer-implemented method of claim 43, wherein the arc transition component and the nozzle body are formed of different materials.

49. The computer-implemented method of claim 43, wherein the noble metal of the arc transition component is silver.

50. The computer-implemented method of claim 49, wherein the material of the arc transition component is a silver alloy.

51. The computer-implemented method according to claim 43, further comprising the plasma arc welding torch repeatedly switching between generating the guiding arc and the transferring arc for at least 90 seconds without the plasma arc being extinguished.

52. A method for manufacturing a nozzle for an air-cooled plasma arc welding torch, the method comprising: A nozzle body is formed of a first metal, the nozzle body including a proximal portion and a distal portion extending along a longitudinal axis, wherein the distal portion of the nozzle body includes a first orifice; An arc transition component is formed of a second metal, the arc transition component including a second orifice, wherein the second metal of the arc transition component includes a noble metal, and the second metal is different from the first metal; as well as The arc transition component is coupled to the distal portion of the nozzle body such that the second orifice is substantially aligned with the first orifice.

53. The method of claim 52, wherein the noble metal of the arc transition component is silver.

54. The method of claim 53, wherein the second metal of the arc transition component is a silver alloy.

55. The method of claim 53, wherein the second metal of the arc transition component comprises at least about 45% silver.

56. The method of claim 52, wherein the first metal is copper.

57. The method of claim 52, wherein the arc transition component is mounted to the distal portion of the nozzle body by at least one of the following methods: brazing, metallurgical bonding, stamping, friction welding, forging, ultrasonic welding, or pressure fitting.

58. The method of claim 52, wherein the arc transition component has a washer-like shape.

59. The method of claim 52, wherein the arc transition component comprises a coating on at least one of the end face of the distal portion of the nozzle body, the inner surface of the first orifice, or the inner surface of the second orifice.

60. The method of claim 52, wherein the thickness of the arc transition component along the longitudinal axis of the nozzle is between about 0.005 inches and about 0.15 inches.

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