Plasma Arc Welding Torches and Cutting Systems

Abstract

A plasma arc torch includes a nozzle body, a nozzle extending from the nozzle body, and a shield. An outer retaining hood is attached to the plasma arc torch and secures the shield to the plasma arc torch. A sleeve is located radially outward of the outer retaining hood and is configured to receive a pressurized gas flow. An insulator is located between the outer retaining hood and the sleeve. At least one of the sleeve and the insulator forms a gas flow channel, which is configured to guide a gas flow from the sleeve to a distal portion of the outer retaining hood.

Description

Background of the Invention Field of the Invention

[0002] The present invention relates to a plasma arc torch for cutting a workpiece using a plasma arc, and a system and method for minimizing a molten pool and top spatter generated when piercing a workpiece, which helps to cut a high-quality small-diameter hole.

[0003] Description of related technologies

[0004] Initially, using a plasma arc torch to pierce a workpiece may produce top spatter (also known as slag). As the workpiece is perforated, the molten material is displaced from the perforation and may accumulate as a molten pool around the perforation. The molten material solidifies as top spatter and adheres to the upper surface of the workpiece around the perforation. When perforating thick workpieces (such as 0.25 inches thick or thicker workpieces), top spatter is usually a problem, and perforating such thick workpieces may cause excessive top spatter. Top spatter makes it difficult to cut small holes of acceptable quality in thick workpieces. The diameter of the top spatter is larger than the diameter of the perforation, and the welding torch must cut around the top spatter to obtain a cut hole of acceptable quality. For example, perforating a 1-inch thick workpiece may produce top spatter with a width or diameter exceeding 2 inches. In this case, it is impossible to cut a hole of acceptable quality with a diameter of 2 inches or less. Due to the width of the top spatter generated during perforation, the ratio of hole diameter to material thickness acceptable to conventional plasma cutting systems is typically greater than 2:1. It is desirable to minimize the size of the molten pool produced during piercing, as well as the resulting top spatter, which will allow a smaller hole of acceptable quality to be cut from the workpiece. Summary of the invention

[0005] The following summary of the invention presents a simplified overview to provide a basic understanding of some aspects of the devices, systems and / or methods discussed herein. The present summary is not an extensive review of the devices, systems and / or methods discussed herein. It is not intended to point out key elements or to delimit the scope of such devices, systems and / or methods. The only purpose is to present some concepts in a simplified form as a preface to a more detailed description presented later.

[0006] According to one aspect of the present invention, a plasma arc torch is provided, the plasma arc torch having a nozzle body, a nozzle extending distally from the nozzle body, and a shield. An external retaining hood is attached to the plasma arc torch and fixes the shield to the plasma arc torch. A sleeve is located radially outside the external retaining hood and is configured to receive a pressurized gas flow. An insulator is located between the external retaining hood and the sleeve. At least one of the sleeve and the insulator forms a gas flow channel, which is configured to guide the gas flow from the sleeve to the distal portion of the external retaining hood.

[0007] According to another aspect of the present invention, a plasma cutting system is provided. The plasma cutting system includes a plasma arc torch and a plasma cutting power supply that provides a plasma cutting current to the plasma arc torch. A torch actuator moves the plasma arc torch during a cutting operation. A motion controller is operatively connected to the torch actuator to control the movement of the plasma arc torch during a cutting operation. A gas controller is configured to control the flow of plasma gas and molten metal scavenging gas to the plasma arc torch. The molten metal scavenging gas flow is activated during a piercing operation of the plasma arc torch, and the gas controller is configured to automatically determine the completion of the piercing operation and stop the molten metal scavenging gas flow after determining that the piercing operation is completed.

[0008] According to another aspect of the present invention, an attachment for a plasma arc torch is provided. The attachment includes an outer retaining hood that is attachable to the plasma arc torch and is configured to secure a shield to the plasma arc torch. A sleeve is located radially outward of the outer retaining hood and is configured to receive a pressurized gas flow. An insulator is located between the outer retaining hood and the sleeve. The attachment includes a gas flow channel that is configured to direct a gas flow from the sleeve to a distal portion of the outer retaining hood. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above and other aspects of the present invention will become apparent to those skilled in the art to which the present invention relates after reading the following description with reference to the accompanying drawings, in which:

[0010] Figure 1 A plasma arc welding torch is shown;

[0011] Figure 2 is an exploded view showing components of a plasma arc torch;

[0012] Figure 3 is an exploded view showing components of an attachment for a plasma arc torch;

[0013] Figure 4 is a cross-sectional view of an attachment for a plasma arc welding torch;

[0014] Figure 5 is a cross-sectional view of a portion of a plasma arc welding torch;

[0015] Figure 6 is a cross-sectional view of a second embodiment of an attachment for a plasma arc torch;

[0016] Figure 7 An insulator of a second embodiment of an attachment for a plasma arc torch is shown;

[0017] Figure 8 An insulator of a second embodiment of an attachment for a plasma arc torch is shown;

[0018] Fig. 9 is a schematic diagram of a plasma cutting system;

[0019] Fig.10 shows the result of a plasma arc torch perforating a workpiece; and

[0020] Fig.11 Another result of a plasma arc torch penetrating a workpiece is shown. DETAILED DESCRIPTION

[0021] The present invention relates to a plasma arc torch for cutting a workpiece using a plasma arc, and a system and method for minimizing a plasma molten pool generated when a workpiece is perforated. The present invention will now be described with reference to the accompanying drawings, wherein the same reference numerals are used throughout to refer to the same elements. It will be understood that these different drawings do not have to be drawn in a proportional manner to each other, and the same is true within a given drawing, and in particular, the sizes of the components are drawn arbitrarily to facilitate the understanding of the drawings. In the following description, for the purpose of explanation, a number of specific details are set forth in order to provide a comprehensive understanding of the present invention. However, it may be apparent that the present invention can be practiced without these specific details. In addition, other embodiments of the present invention are possible and can be practiced and implemented in a manner other than as described. The terms and phrases used in describing the present invention are adopted for the purpose of promoting understanding of the present invention and should not be considered restrictive.

[0022] As used herein, "at least one," "one or more," and "and / or" are open expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions "at least one of A, B, and C," "at least one of A, B, or C," "one or more of A, B, and C," "one or more of A, B, or C," and "A, B, and / or C" refers to A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, and C together. Any disjunctive words and / or phrases that give two or more alternative terms, whether in the description of the embodiments, claims, or drawings, should be understood to cover the following possibilities: including one of these terms, any of these terms, or all of the terms. For example, the phrase "A or B" should be understood to include the following possibilities: "A," or "B," or "A and B."

[0023] Discussed herein is a plasma arc torch that may have, among other things, fluid and electrical connections and a handle portion at the upstream end of the torch and a nozzle, a shield, and an external retaining hood at the downstream or cutting end of the torch. The term "proximal end" as used herein refers to the upstream direction of the torch, toward the end of the torch having the handle portion and any fluid and electrical connections. The term "distal end" as used herein refers to the downstream direction of the torch, toward the cutting end of the torch.

[0024] The present invention minimizes the molten pool and the top spatter or top slag generated during piercing by creating a gas flow of molten metal scavenging gas outside the plasma gas flow and the shielding gas flow, and also reduces the piercing time. For example, the molten metal scavenging gas can flow through the outer distal portion of the outer retaining cover of the welding torch and flow around the shield of the welding torch to blow the molten material generated during piercing through the piercing. The molten metal scavenging gas flow is activated only during the piercing operation and automatically stops after the piercing operation is completed. In some embodiments, an additive (such as an anti-splash liquid) is injected into the molten metal scavenging gas flow to help prevent the molten material generated during piercing from sticking to the workpiece and allowing the molten material to flow through the piercing. For thick workpieces (e.g., about 0.25 inches thick or thicker), the present invention can pierce the workpiece faster than conventional plasma arc systems (e.g., the piercing time is reduced by approximately 30%), and the size of the top spatter can be reduced from more than 2x (200%) of the material thickness to less than 1x (100%) of the material thickness. Due to the small width of the top spatter generated during piercing, the present invention allows 1:1 holes (hole diameter to material thickness ratio) and even smaller holes to be cut from a workpiece with acceptable cut quality.

[0025] Figure 1 An example plasma arc or plasma cutting torch 100 is shown. The plasma arc torch 100 can be a liquid-cooled torch or an air-cooled torch. The torch has a handle portion 102 that can be clamped into an automated cutting device, such as a computer numerical control (CNC) plasma cutting table or a robotic arm. Distal to the handle portion 102 is a torch body 104 that can be made of a metallic material. An external retaining hood is attached to the torch body 104 that secures the shield to the torch. The external retaining hood is part of an attachment 106 for the torch 100. The attachment 106 provides a molten metal scavenging gas flow during the piercing operation and discharges an additive (e.g., an anti-spatter liquid) to the workpiece to minimize the size of the molten pool and any top spatter produced during the piercing operation.

[0026] Providing molten metal purge gases and additives (e.g., anti-spatter liquid) will be discussed in the context of an attachment 106 for a plasma arc torch 100. However, it should be appreciated that the ability to provide molten metal purge gases and additives can be native to the torch 100 itself, rather than provided as an attachment. For example, flow passages for molten metal purge gases and additives can be native to the torch 100. The molten metal purge gases and additives can flow through conduits in the torch body 104 to the distal end of the torch 100 for exhaust into the shielding gas environment. The attachment 106 embodiment shown in the accompanying drawings does provide the advantage of being removable from the torch 100 when not needed (such as when cutting relatively thin workpieces where top spatter is not an issue).

[0027] Figure 2 is an exploded view of a welding torch showing various components and consumables of the welding torch presented along an axis 109 of the welding torch. Figure 2 1 shows a torch body 104, an attachment 106, and a shield 108. The shield 108 is secured to the torch by an external retaining cover within the attachment 106, which is threadedly connected to the torch body 104. When the attachment 106 is not in use, a conventional external retaining cover replaces the attachment on the torch. When the attachment 106 is needed, the conventional external retaining cover is unscrewed from the torch body 104 and replaced with the attachment.

[0028] A nozzle body 110 or anode, and a cooling tube 112 extend from the torch body 104. The cooling tube 112 is attached to a cathode within the torch, as is the electrode 114. The torch further includes a swirl ring 116 and a nozzle 118. When mounted on the torch, the nozzle 118 extends distally from the nozzle body 110. The swirl ring 116 and nozzle 118 are held in place by an inner retaining shroud 120, which is threaded onto the nozzle body 110. A shield 108 covers the distal ends of the nozzle 118 and the inner retaining shroud 120. The electrode 114, swirl ring 116, nozzle 118, inner retaining shroud 120, shield 108, and outer retaining shroud can all be considered consumables of a plasma arc torch.

[0029] Figure 3 is an exploded view of the attachment 106, and Figure 41 is a cross-sectional view of an attachment. The attachment includes an outer retaining cover 122 that fixes a shield (not shown) to the welding torch. The outer retaining cover 122 can be made of a metal material, such as brass and other suitable metals or alloys. A sleeve 124 is located radially outside the outer retaining cover 122. The sleeve 124 can also be made of a metal material, such as aluminum, stainless steel or other suitable metals or alloys. An insulator 126 is located between the outer retaining cover 122 and the sleeve 124. The insulator 126 can be made of a plastic material, such as glass-reinforced PEEK (polyetheretherketone), polyetherimide, etc. The insulator 126 can electrically insulate the sleeve 124 from the outer retaining cover 122. The insulator 126 is attached to the outer retaining cover 122, such as via a press fit or an adhesive. The attachment 106 further includes a shield 128 that extends axially from the sleeve 124 beyond the distal end of the outer retaining cover 122. In the illustrated embodiment, the sleeve 124 has male threads and the guard 128 has female threads to facilitate attachment of the guard to the sleeve; however, other attachment mechanisms are possible. The guard 128 is removable from the sleeve 124 to facilitate assembly of the attachment 106 (e.g., to allow the assembly of the outer retaining cover 122 and the insulator 126 to be inserted into the sleeve); however, in some embodiments, the sleeve and the guard may be integrally formed. Figure 5 As best seen in FIG. 1 , the shield 128 is radially offset from the outer retaining shroud 122 and the shield 108 to form an air gap between the shield and both the outer retaining shroud and the shield. During the piercing operation, the air gap directs the flow of molten metal scavenging gas through the outer retaining shroud 122 and the shield 108 to the distal terminal end of the plasma arc torch and around the plasma arc. The distal portion of the shield 128 has a generally conical shape, while the proximal portion of the shield is generally cylindrical. The shield 128 can be made of a metallic material, such as copper or a copper alloy, or other suitable metals or alloys.

[0030] exist Figure 3 and Figure 4In the illustrated embodiment, the sleeve 124 is attached to the assembly of the outer retaining cover 122 and the insulator 126 by a plurality of fasteners 130 spaced apart around the circumference of the sleeve. For example, the sleeve 124 may be attached via three equally spaced screws, thumb screws, etc., but any suitable number of fasteners may be used. The fasteners 130 permit the sleeve 124 to rotate relative to the torch and the outer retaining cover 122 so that a gas fitting 132 extending from the sleeve 124 may be positioned in a convenient location. The gas fitting 132 may be a quick disconnect type fitting for attaching a gas hose to the sleeve 124. Once the sleeve 124 is mounted to the assembly of the outer retaining cover 122 and the insulator 126, with the gas fitting 132 placed in a convenient location relative to the torch, the sleeve and the shield 128 will rarely need to be removed from the outer retaining cover / insulator assembly. When it is necessary to replace the welding torch consumables, the hose can be disconnected from the gas fitting 132 and the outer retaining cover 122 can be unscrewed from the welding torch while the sleeve 124 and the guard 128 are still attached. Removing the attachment 106 will release the guard 108 ( Figure 5 ) and allows the inner retaining cover 120 to be removed from the welding torch.

[0031] During the perforating operation, the sleeve 124 receives a pressurized molten metal purging gas flow from a gas source via the gas fitting 132, and optionally an additive (e.g., an anti-spatter liquid) entrained in the molten metal purging gas flow. The molten metal purging gas can be air or other gases (e.g., nitrogen, argon, etc.). The inner surface of the sleeve 124 includes a counterbore or channel that creates an annular plenum 134 for the molten metal purging gas. The annular plenum 134 is in fluid communication with the gas fitting 132. A plurality of axially extending gas flow channels direct the molten metal purging gas flow from the sleeve 124 to the distal portion of the outer retaining shroud 122. The shield 128 further directs the molten metal purging gas flow around the distal terminal end of the outer retaining shroud 122 and around the shield 108 ( Figure 5 ). An axially extending gas flow passage may be positioned in the sleeve 124 and / or the insulator 126 and may extend from the annular plenum 134 to a distal end of the sleeve and / or the insulator. Figure 3 and Figure 4 In the illustrated embodiment, the gas flow passages are formed as a plurality of grooves 136 or milled slots annularly arranged around the outer surface of the insulator 126. The grooves 136 extend axially in the proximal direction to the annular plenum 134 and in the distal direction to the terminal ends of the sleeve 124 and the insulator 126. The grooves 136 serve as passages for the molten metal scavenging gas while providing a flow restriction that helps to evenly distribute the gas. In alternative embodiments, in addition to being formed as surface grooves or slots, the gas flow passages can also be located within the walls of the sleeve 124 and / or the insulator 126.

[0032] The proximal end of the sleeve 124 forms an inwardly projecting annular shoulder 138. The annular shoulder provides a stop surface for the assembly of the outer retaining shield 122 and the insulator 126. With the shield 128 removed, the assembly of the outer retaining shield 122 and the insulator 126 can be slid into the sleeve 124 until the insulator contacts the annular shoulder 138. The fastener 130 can be tightened to attach the sleeve 124 to the assembly of the outer retaining shield 122 and the insulator 126. The shield 128 can then be placed over the distal terminal end of the outer retaining shield 122 and threaded onto the sleeve 124 to complete the assembly of the attachment 106 for a plasma arc torch.

[0033] Figure 5 is a cross-sectional view of the distal end of a plasma arc torch having an attachment 106 for cleaning melt from the torch. Figure 5 The various components discussed above are shown. Figure 5 106 and the outer retaining shroud 122 and shield 108 for conveying the molten metal scavenging gas flow 137 and anti-spatter liquid. During the piercing operation, the molten metal scavenging gas flow 137 and any entrained anti-spatter liquid surround the plasma gas flow and shield gas flow 139. The distal terminal end or tip of the shield 108 can be extended axially beyond the terminal end of the shield 128 on the attachment 106 and extend from the shield 128, as shown. Extending the shield 108 from the shield 128 on the attachment 106 allows the welding torch and plasma cutting power source with its own plate sensing capability to operate properly. The plate sensing capability provides contact sensing between the welding torch and the workpiece.

[0034] Figure 6 An additional embodiment of the attachment 106 is shown without the fasteners discussed above for attaching the sleeve 124 to the assembly of the outer retaining cover 122 and the insulators 140A, 140B. Figure 7 and Figure 8 Two different embodiments of insulators 140A, 140B are shown. Insulators 140A, 140B have flanges 142 at their distal terminal ends. When guard 128 is threaded onto sleeve 124, an inwardly projecting annular shoulder 144 on the guard contacts flange 142 on insulators 140A, 140B. Annular shoulder 144 on guard 128 and annular shoulder 138 on sleeve 124 clamp onto insulators 140A, 140B to hold the sleeve in place on outer retaining cover 122. Flange 142 on insulator may include grooves or slots through which molten metal scavenging gas may flow. The slots may be as shown in FIG. Figure 7 The slots may extend generally radially as shown to provide non-swirl gas flow, or they may extend generally radially as shown to provide non-swirl gas flow. Figure 8The radial angle shown is to cause the molten metal purge gas to swirl. The shield 128 may include an annular groove or undercut to accommodate the flange 142 and provide a plenum for the molten metal purge gas.

[0035] Fig. 9 Components of an example plasma cutting system 200 are schematically shown. The system 200 includes an open-air plasma cutting table 202 that cuts a workpiece W in an open-air (non-underwater) environment. The plasma cutting table 202 includes a torch actuator, such as a gantry 204 and a torch carriage 206, that moves the torch during the cutting operation. The gantry 204 can move back and forth in a first direction (e.g., along the Y direction) along the length of the body of the cutting table. The gantry 204 can move on a track or rail extending along the side of the table 202. The plasma arc torch 100 is attached to the torch carriage 206, which is mounted on the gantry 204. The torch carriage 206 can move back and forth along the gantry 204 in a second direction perpendicular to the first direction (e.g., in the X direction). The plasma cutting table 202 can be programmed to make precise cuts in the workpiece W by controlling the movement of the torch carriage 206 and the gantry 204 in the X and Y directions, respectively. In some embodiments, the torch carriage 206 can move the plasma arc torch 100 vertically toward and away from the workpiece W (e.g., in the Z direction), so that the torch can move in three perpendicular directions. In some embodiments, the torch carriage 206 can also rotate or tilt the torch 100 in a plane perpendicular to the plane of the table (e.g., in the XZ plane) to make bevel cuts.

[0036] The plasma cutting system 200 may include a torque height controller 208, which may be mounted to the gantry 204. The system 200 may also include a drive system 210 for providing movement of the welding torch 100 relative to a workpiece W positioned on the table 202. A plasma cutting power supply 212 is coupled to the welding torch 100 to provide a desired plasma cutting current for creating a plasma arc.

[0037] The system 100 may further include a gas console or gas controller 214 configured to adjust the gas flow and pressure of the plasma gas and the shielding gas during the cutting operation, and also control the flow / pressure of the molten metal scavenging gas provided to the welding torch 100 and the injection of any additives (such as anti-spatter liquid). Various gases can be used as plasma gas, shielding gas and molten metal scavenging gas, such as air, nitrogen, oxygen, etc. The plasma gas, shielding gas and molten metal scavenging gas can be the same gas or different gases. The gas console 214 can include proportional valves, etc., for controlling the pressure and / or flow of the plasma gas, shielding gas and molten metal scavenging gas.

[0038] The gas controller 214 provides molten metal purging gas to the welding torch 100 only during the piercing operation (e.g., when the piercing operation is about to begin or begins and until the piercing operation is completed or has just completed). The gas controller 214 communicates with the plasma cutting power supply 212 to determine when the piercing operation begins and is completed. The plasma cutting power supply 212 can notify the gas controller 214 about the start and completion of the piercing operation, or the gas controller can determine these states on its own (e.g., based on plasma voltage / current information received from the cutting power supply). For example, the plasma cutting power supply 212 can send a plasma voltage signal to the gas controller 214 during the piercing operation, and the gas controller can automatically determine when the piercing operation is completed based on the increase in plasma voltage. When the gas controller 214 determines that the workpiece W has been pierced, the gas controller stops the flow of molten metal purging gas.

[0039] The molten metal purge gas pushes the molten material produced during perforation through the perforations. An exemplary pressure range for the molten metal purge gas is 5-70 psi, but other pressures may be used. An exemplary flow range for the molten metal purge gas is 500 to 1200 scfh, but other flow rates may be used.

[0040] An additive, such as an anti-spatter liquid, can be added to the molten metal scavenging gas flow. The additive is sprayed onto the surface of the workpiece W at each perforation site to reduce the ability of the top spatter to stick to the workpiece and / or reduce the surface tension of the molten pool. The anti-spatter liquid typically contains silicone or similar ingredients, which are usually petroleum-based or water-based solvents to prevent spatter from sticking to the workpiece. The anti-spatter liquid also reduces the surface tension of the molten pool and promotes the movement of the molten pool by the molten metal scavenging gas. The anti-spatter liquid is known and its composition does not need to be discussed in detail. In some embodiments, the additive can be a powder entrained in the molten metal scavenging gas and blown onto the workpiece at the perforation site, rather than an aerosol liquid. The additive provided by the molten metal scavenging gas can be any substance that reduces the ability of the top spatter to stick to the workpiece and / or reduces the surface tension of the molten pool. In some embodiments, the additive can be sprayed onto the workpiece separately from the molten metal scavenging gas. In such an embodiment, the attachment or welding torch can include a dedicated port and conduit for the additive.

[0041] The plasma cutting system 200 may include a reservoir for the additive. The reservoir may be located, for example, in the plasma cutting power supply 212 or in the gas controller 214. The gas controller 214 may include an injector, such as an anti-splatter liquid injector 216, which injects the additive into the molten metal scavenging gas flow. The injector 216 may include a pump and an electronic injector, or a mechanical device, such as a venturi injector. The gas controller 214 is operatively connected to the anti-splatter liquid injector 216 to control its operation. During the perforating operation, the gas controller 214 may enable the anti-splatter liquid injector 216 to spray the anti-splatter liquid into the molten metal scavenging gas flow and onto the workpiece W. The anti-splatter liquid helps the molten metal generated during the perforation flow through the perforation because the molten metal is pushed by the scavenging gas flow.

[0042] An operator of the plasma cutting system 200 may enable / deactivate the molten metal purge gas and / or additive via the user interfaces 220, 222. The torch attachment may remain mounted on the torch when the molten metal purge gas or additive is deactivated.

[0043] The plasma cutting system 200 may include a CNC motion controller 218. The controller 218 is operatively connected to the gantry 204, the torch carriage 206, the torch height controller 208, etc. to control the movement of the welding torch 100 during the cutting operation. The controller 218 may include a user input / display screen or user interface 220. The user uses the user interface 220 and the controller 218 to input and read cutting operation parameters and data and allow the system 200 to operate as an automated programmable cutting system. The user can input various input parameters into the controller 218 via the user interface 220 (or other devices), including: torch current, material type, material thickness, cutting speed, torch height, plasma gas composition and shielding gas composition, whether molten metal removal is performed during perforation, etc. The workbench 202 may also include a user interface 222, which is operatively connected to the CNC and / or the plasma cutting power supply 212. In embodiments where a robotic arm (such as a torch actuator) is used instead of a gantry and a torch carriage, the CNC may be a robotic controller that controls the movement of the robotic arm. The plasma cutting system 200 can have many different configurations, and the embodiments are not limited to Fig. 9 As shown in , this figure is intended to be exemplary only.

[0044] The motion controller 218, gas controller 214, or plasma cutting power supply 212 may include an electronic controller and may include one or more processors. For example, the controller may include one or more of a microprocessor, a microcontroller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a discrete logic circuit, etc. The controller may further include a memory and may store program instructions that cause the controller to provide the functions assigned to it herein. The memory may include one or more volatile, non-volatile, magnetic, optical, or electrical media, such as a read-only memory (ROM), a random access memory (RAM), an electrically erasable programmable ROM (EEPROM), flash memory, etc. The controller may further include one or more analog-to-digital (A / D) converters for processing a plurality of different analog inputs to the controller. The program instructions for the motion controller 218 may include a cutting diagram or nesting software. Such instructions typically include cutting information, which includes instructions for the system 200 when cutting various holes or contours, taking into account the size and shape of the hole / contour and the material being cut. It is generally understood that the controller can allow the user to cut a plurality of sequential holes, contours, or a combination of holes and contours in a workpiece without stopping between cuts. For example, the operator can select a cutting program that includes both hole and contour cutting instructions, and the motion controller 218 will determine the order and positioning of the cuts, as well as the various parameters of the cuts based on the user input information.

[0045] The controller can operate in a network environment using a logical and / or physical connection to one or more remote computers. Examples of remote computers include workstations, server computers, routers, personal computers, etc. The network environment may include a local area network (LAN) and / or a wide area network (WAN). Such a networked environment is commonplace in offices, enterprise-wide computer networks, intranets, and the Internet. When used in a LAN networked environment, the controller is connected to a local network via a network interface or adapter. When used in a WAN networked environment, the controller typically includes a modem or a network interface, or is connected to a communication server on a LAN, or has other devices for establishing communication on a WAN (e.g., the Internet). In a networked environment, a program module implemented by a controller or a portion thereof may be stored in a remote memory storage device. It should be understood that the network connection described herein is exemplary, and other means for establishing a communication link between devices may be used.

[0046] Fig.10 The results of a conventional piercing operation on a thick workpiece (e.g., about 0.25 inches thick or thicker) and cutting a substantially 1:1 hole through the workpiece are shown. Fig.11A piercing operation is shown, as well as the results of cutting a substantially 1:1 hole in a thick workpiece using the torch attachment discussed above. Fig.10 and Fig.11 The left image of shows the initial perforation surrounded by spatter 224, 226, while the right image shows a substantially 1:1 hole 228, 230 cut out around the perforation. Fig.10 The width of the top splash 224 is more than twice the thickness of the workpiece. Fig.10 To cut a hole in a workpiece in the piercing process, the diameter of the workpiece must be larger than the width of the top spatter to ensure a good cut. This produces a hole diameter to material thickness ratio greater than 2:1. It can be seen that the approximately 1:1 hole 228 is surrounded by spatter 224 generated during the piercing operation. Due to the molten metal scavenging gas flow and the small amount of anti-splash liquid injected during the piercing operation, Fig.11 The width of the top splash 226 is greater than Fig.10 The width of the top splash 226 can be less than the material thickness (e.g., between 40% and 95% of the material thickness), which allows a 1:1 or smaller hole to be cut from the workpiece. Fig.11 There is no spatter around the approximately 1:1 hole 230 in the embodiment.

[0047] In certain embodiments, an anti-spatter liquid may be sprayed during a cutting operation, after perforation, as the torch moves about the workpiece. In such an embodiment, the gas controller continues to provide a flow of molten metal scavenging gas after the perforation operation is completed. Instead of providing a flow of molten metal scavenging gas toward the workpiece, the torch attachment may be configured to provide a vacuum to suck the molten metal away from the workpiece during perforation, rather than pushing it through the perforation. The vacuum attachment may be moved axially along the torch from a retracted position when not in use to an extended position adjacent to or in contact with the workpiece. When the workpiece is perforated, the vacuum may be turned off and the attachment may be retracted from the workpiece. An anti-spatter liquid may be sprayed from the vacuum attachment onto the workpiece to help prevent molten metal generated during perforation from sticking to the workpiece.

[0048] It should be clear that the present disclosure is by way of example, and that various changes may be made by adding, changing or removing details without departing from the reasonable scope of the teachings contained in the present disclosure. Therefore, the present invention is not limited to the specific details of the present disclosure, unless the appended claims are necessarily so limited.

Claims

1. A plasma arc welding torch comprising: Nozzle body; a nozzle extending from the nozzle body; Protective cover; an outer retaining shroud attached to the plasma arc torch, the outer retaining shroud securing the protective shroud to the plasma arc torch; a sleeve located radially outward of the outer retaining shroud and configured to receive a flow of pressurized gas; as well as an insulator located between the outer retaining cover and the sleeve, wherein at least one of the sleeve and the insulator forms a gas flow passage configured to direct a gas flow from the sleeve to a distal portion of the outer retaining shield; Wherein, the gas flow channel includes a plurality of grooves arranged in an annular shape around the outer surface of the insulator; and wherein, the sleeve includes an annular plenum chamber, and the plurality of grooves extend axially from the annular plenum chamber to the distal terminal end of the insulator.

2. The plasma arc torch according to claim 1, wherein: The gas flow passage extends from the annular plenum to a distal end of the sleeve.

3. The plasma arc torch of claim 2, further comprising a gas fitting mounted to the sleeve and in fluid communication with the annular plenum.

4. The plasma arc torch of claim 1 further comprising a shield extending axially from the sleeve beyond the distal terminal end of the outer retaining shroud, wherein The shield is radially offset from the outer retaining shroud and the shield to form an air gap therebetween for directing the gas flow to a distal terminal end of the plasma arc torch.

5. A plasma cutting system comprising: The plasma arc welding torch as claimed in claim 1; A plasma cutting power supply, the plasma cutting power supply providing a plasma cutting current to the plasma arc welding torch; a torch actuator that moves the plasma arc torch during a cutting operation; a motion controller operatively connected to the torch actuator to control movement of the plasma arc torch during the cutting operation; as well as a gas controller configured to control the flow of plasma gas and molten metal purge gas to the plasma arc torch, wherein the molten metal purging gas flow is activated during a piercing operation of the plasma arc torch, and the gas controller is configured to automatically determine completion of the piercing operation and to stop the molten metal purging gas flow upon determining completion of the piercing operation.

6. The plasma cutting system of claim 5, further comprising an injector that injects an additive into the molten metal scavenging gas flow, wherein: The additive is configured to reduce the surface tension of a molten pool produced during the piercing operation.

7. The plasma cutting system of claim 6, wherein: The additive is an anti-splash liquid, and wherein the gas controller is operatively connected to the injector to control operation of the injector.

8. The plasma cutting system of claim 5, wherein: The gas controller is further configured to control the discharge of anti-splash liquid to the plasma arc torch.

9. The plasma cutting system of claim 5, wherein: The gas controller is further configured to control the discharge of an additive to the plasma arc torch, wherein the additive is configured to reduce the surface tension of a molten pool generated during the piercing operation.

10. The plasma cutting system of claim 5, wherein: The plasma cutting power supply provides a plasma voltage signal to the gas controller, and the gas controller determines completion of the perforating operation based on changes in the plasma voltage signal.

11. The plasma cutting system of claim 5, wherein: The gas flow passage extends from the annular plenum to a distal end of the sleeve.

12. The plasma cutting system of claim 11, further comprising a gas fitting mounted to the sleeve and in fluid communication with the annular plenum.

13. The plasma cutting system of claim 5, further comprising a shield extending axially from the sleeve beyond the distal terminal end of the outer retaining shroud, wherein The shield is radially offset from the outer retaining shroud and the shield to form an air gap therebetween for directing the molten metal scavenging gas flow to a distal terminating end of the plasma arc torch.

14. An attachment for a plasma arc torch, comprising: an outer retaining shroud attachable to the plasma arc torch and configured to secure a protective shield to the plasma arc torch; a sleeve located radially outward of the outer retaining shroud and configured to receive a flow of pressurized gas; an insulator positioned between the outer retaining shield and the sleeve; and a gas flow passage configured to direct a flow of gas from the sleeve to a distal portion of the outer retaining shield; Wherein, the gas flow channel includes a plurality of grooves arranged in an annular shape around the outer surface of the insulator; and wherein, the sleeve includes an annular plenum chamber, and the plurality of grooves extend axially from the annular plenum chamber to the distal terminal end of the insulator.

15. The attachment of claim 14, wherein: The gas flow passage extends from the annular plenum to a distal end of the sleeve.

16. The attachment of claim 15, further comprising a gas fitting mounted to the sleeve and in fluid communication with the annular plenum.

17. The attachment of claim 14, further comprising a guard extending axially from the sleeve beyond the distal terminal end of the outer retaining shield.

18. The attachment of claim 17, wherein: The shield is radially offset from the outer retaining shroud to form an air gap between the shield and the outer retaining shroud for directing the gas flow to a distal terminal end of the plasma arc torch.

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