Abstract:
Stickout of a welding electrode wire from a welding torch is determined during welding, and based upon a welding parameter, such as welding current. Different relationships are used for the determination depending upon whether the welding wire is in a short-circuit condition or an arc condition. The stickout may be converted to a standardized unit of measure to make it readily understandable to an operator. The stickout may be logged and associated with other parameters and information, such as workpiece, operator, welding system, date and time. The stickout may be used as the basis for an alarm or a disabling operation. Moreover, the stickout may be provided on a readout for the operator. It may also be used as a basis for controlling a wire feeding apparatus that retracts the welding wire to a desired stickout following a weld.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/468,826, entitled “Stickout Calculator”, filed on Mar. 29, 2011, and of U.S. Provisional Patent Application No. 61/557,808, entitled “Welding Electrode Stickout Monitoring and Control”, filed on Nov. 9, 2011, both of which are herein incorporated by reference in their entireties. 
     
    
     BACKGROUND 
       [0002]    The invention relates generally to welders, and more particularly to a welder configured to perform a welding operation in which a welding wire is advanced from a welding torch. 
         [0003]    A wide range of welding systems and welding control regimes have been implemented for various purposes. In continuous welding operations, metal inert gas (MIG) techniques allow for formation of a continuing weld bead by feeding welding wire shielded by inert gas from a welding torch. Electrical power is applied to the welding wire and a circuit is completed through the workpiece to sustain an arc that melts the wire and the workpiece to form the desired weld. Certain related processes do not use shielding gas, and may rely upon constituents in the welding wire for forming and protecting the progressing weld. 
         [0004]    In its various forms, MIG welding involves application of controlled voltages and currents to a welding wire that forms an electrode and is advanced towards a workpiece to create an arc between the electrode and the workpiece. The wire electrode is typically fed by a wire feeder coupled to a welding power supply, although in some systems, the wire feeder may be integrated into the power supply, or wire may be fed by a welding torch (e.g., “spoolgun”). In general, the welding torch may be held and controlled by a human operator, or may be part of an automated system, typically manipulated by a robotic device. Welding parameters may be set for all of these processes, including current and voltage levels, wire feed speeds, and so forth. For manual applications, travel speed (the rate of advancement of the torch to create the weld) is regulated by the operator, while in automated applications, this may be set in advance for particular welds and workpieces. 
         [0005]    A continuing issue in MIG and related welding processes is variability in the extension of the welding electrode from the structure supporting it in the welding torch. This length, sometimes referred to as “stickout” is necessary to allow the electrode to extend past the surrounding gas nozzle for welding, and to avoid excessive spatter and wear of the contact tip within the nozzle. At the same time, incorrect stickout can lead to degradation in welds, increased spatter, reduced contact tip life, and other unwanted effects. Moreover, variability in the stickout between welds can result in non-uniformity in part quality, particularly in automated applications. 
         [0006]    There is a need, therefore, for improved techniques for measuring or estimating stickout, and for using the measured or estimated stickout for monitoring and/or control of the welding wire or welding operation. 
       BRIEF DESCRIPTION 
       [0007]    The present invention provides welding systems designed to respond to such needs. In accordance with an exemplary implementation, a welding system comprises a sensor configured to sense a welding parameter, and processing circuitry configured to determine stickout of a welding electrode wire from a welding torch based upon the sensed welding parameter. The processing circuitry is configured to evaluate and store an evaluation of a performance of the welding system or a weld based on stickout. A component is configured to control an operation of the welding system based upon the determined stickout. 
         [0008]    The invention also provides a welding method that includes sensing welding current during welding, and determining, based upon the welding current, stickout of a welding electrode wire from a welding torch. The stickout may be logged during welding and/or used to control an operation of the welding system. The method also includes evaluating and storing an evaluation of a performance of the welding system or a weld based on stickout. 
         [0009]    In accordance with a particular aspect, the method comprises sensing welding current during welding, and determining, based upon the welding current, stickout of a welding electrode wire from a welding torch, wherein the stickout is determined by a first relationship if the welding electrode wire is in a short condition, and by a second relationship of the welding electrode wire is in an arc condition. A value of the stickout is then determined in a standardized unit of measure for logging and/or presentation to a welding operator. 
     
    
     
       DRAWINGS 
         [0010]      FIG. 1  is a diagrammatical representation of an exemplary MIG welding system illustrating a power supply coupled to a wire feeder for performing pulsed welding operations in accordance with aspects of the present techniques; 
           [0011]      FIG. 2  is a partially broken view of an exemplary welding torch with the wire electrode protruding from the torch while preforming a welding operation; 
           [0012]      FIG. 3  is a similar view of the welding torch with the wire retracted within the nozzle following the welding operation; 
           [0013]      FIG. 4  is a flow chart illustrating exemplary steps in the measurement or estimation of stickout based upon welding parameters; 
           [0014]      FIG. 5  is a flow chart illustrating exemplary monitoring and control options that may be implemented based upon stickout measurement or estimation; and 
           [0015]      FIG. 6  is a diagrammatical representation of certain of the functional components of a welding system that may be involved in implementing the monitoring and control options of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Turning now to the drawings, and referring first to  FIG. 1 , an exemplary welding system is illustrated as including a power supply  10  and a wire feeder  12  coupled to one another via conductors or conduits  14 . In the illustrated embodiment the power supply  10  is separate from the wire feeder  12 , such that the wire feeder may be positioned at some distance from the power supply near a welding location. However, it should be understood that the wire feeder, in some implementations, may be integral with the power supply. In such cases, the conduits  14  would be internal to the system. In embodiments in which the wire feeder is separate from the power supply, terminals are typically provided on the power supply and on the wire feeder to allow the conductors or conduits to be coupled to the systems so as to allow for power and gas to be provided to the wire feeder from the power supply, and to allow data to be exchanged between the two devices. 
         [0017]    The system is designed to provide wire, power and shielding gas to a welding torch  16 . As will be appreciated by those skilled in the art, the welding torch may be of many different types, and typically allows for the feed of a welding wire and gas to a location adjacent to a workpiece  18  where a weld is to be formed to join two or more pieces of metal. A second conductor is typically run to the welding workpiece so as to complete an electrical circuit between the power supply and the workpiece. 
         [0018]    The system is designed to allow for data settings to be selected by the operator, particularly via an operator interface  20  provided on the power supply. The operator interface will typically be incorporated into a front faceplate of the power supply, and may allow for selection of settings such as the weld process, the type of wire to be used, voltage and current settings, and so forth. In particular, the system is designed to allow for MIG welding with various steels, aluminums, or other welding wire that is channeled through the torch. These weld settings are communicated to control circuitry  22  within the power supply. 
         [0019]    The control circuitry, described in greater detail below, operates to control generation of welding power output that is applied to the welding wire for carrying out the desired welding operation. In certain presently contemplated embodiments, for example, the control circuitry may be adapted to regulate a suitable MIG welding regime. The control circuitry is thus coupled to power conversion circuitry  24 . This power conversion circuitry is adapted to create the output power, such as pulsed pulsed waveforms that will ultimately be applied to the welding wire at the torch. Various power conversion circuits may be employed, including choppers, boost circuitry, buck circuitry, inverters, converters, and so forth. The configuration of such circuitry may be of types generally known in the art in and of itself The power conversion circuitry  24  is coupled to a source of electrical power as indicated by arrow  26 . The power applied to the power conversion circuitry  24  may originate in the power grid, although other sources of power may also be used, such as power generated by an engine-driven generator, batteries, fuel cells or other alternative sources. Finally, the power supply illustrated in  FIG. 1  includes interface circuitry  28  designed to allow the control circuitry  22  to exchange signals with the wire feeder  12 . 
         [0020]    The wire feeder  12  includes complimentary interface circuitry  30  that is coupled to the interface circuitry  28 . In some embodiments, multi-pin interfaces may be provided on both components and a multi-conductor cable run between the interface circuitry to allow for such information as wire feed speeds, processes, selected currents, voltages or power levels, and so forth to be set on either the power supply  10 , the wire feeder  12 , or both. 
         [0021]    The wire feeder  12  also includes control circuitry  32  coupled to the interface circuitry  30 . As described more fully below, the control circuitry  32  allows for wire feed speeds to be controlled in accordance with operator selections, and permits these settings to be fed back to the power supply via the interface circuitry. The control circuitry  32  is coupled to an operator interface  34  on the wire feeder that allows selection of one or more welding parameters, particularly wire feed speed. The operator interface may also allow for selection of such weld parameters as the process, the type of wire utilized, current, voltage or power settings, and so forth. The control circuitry  32  is also coupled to gas control valving  36  which regulates the flow of shielding gas to the torch. In general, such gas is provided at the time of welding, and may be turned on immediately preceding the weld and for a short time following the weld. The gas applied to the gas control valving  36  is typically provided in the form of pressurized bottles, as represented by reference numeral  38 . 
         [0022]    The wire feeder  12  includes components for feeding wire to the welding torch and thereby to the welding application, under the control of control circuitry  36 . For example, one or more spools of welding wire  40  are housed in the wire feeder. Welding wire  42  is unspooled from the spools and is progressively fed to the torch. The spool may be associated with a clutch  44  that disengages the spool when wire is to be fed to the torch. The clutch may also be regulated to maintain a minimum friction level to avoid free spinning of the spool. A feed motor  46  is provided that engages with feed rollers  48  to push wire from the wire feeder towards the torch. In practice, one of the rollers  48  is mechanically coupled to the motor and is rotated by the motor to drive the wire from the wire feeder, while the mating roller is biased towards the wire to maintain good contact between the two rollers and the wire. Some systems may include multiple rollers of this type. Finally, a tachometer  50  may be provided for detecting the speed of the motor  46 , the rollers  48 , or any other associated component so as to provide an indication of the actual wire feed speed. Signals from the tachometer are fed back to the control circuitry  36 , such as for calibration as described below. 
         [0023]    It should be noted that other system arrangements and input schemes may also be implemented. For example, the welding wire may be fed from a bulk storage container (e.g., a drum) or from one or more spools outside of the wire feeder. Similarly, the wire may be fed from a “spool gun” in which the spool is mounted on or near the welding torch. As noted herein, the wire feed speed settings may be input via the operator input  34  on the wire feeder or on the operator interface  20  of the power supply, or both. In systems having wire feed speed adjustments on the welding torch, this may be the input used for the setting. 
         [0024]    Power from the power supply is applied to the wire, typically by means of a welding cable  52  in a conventional manner. Similarly, shielding gas is fed through the wire feeder and the welding cable  52 . During welding operations, the wire is advanced through the welding cable jacket towards the torch  16 . Within the torch, an additional pull motor  54  may be provided with an associated drive roller, particularly for aluminum alloy welding wires. The motor  54  is regulated to provide the desired wire feed speed as described more fully below. A trigger switch  56  on the torch provides a signal that is fed back to the wire feeder and therefrom back to the power supply to enable the welding process to be started and stopped by the operator. That is, upon depression of the trigger switch, gas flow is begun, wire is advanced, power is applied to the welding cable  52  and through the torch to the advancing welding wire. Finally, a workpiece cable and clamp  58  allow for closing an electrical circuit from the power supply through the welding torch, the electrode (wire), and the workpiece for maintaining the welding arc during operation. 
         [0025]    It should be noted throughout the present discussion that while the wire feed speed may be “set” by the operator, the actual speed commanded by the control circuitry will typically vary during welding for many reasons. For example, automated algorithms for “run in” (initial feed of wire for arc initiation) may use speeds derived from the set speed. Similarly, various ramped increases and decreases in wire feed speed may be commanded during welding. Other welding processes may call for “cratering” phases in which wire feed speed is altered to fill depressions following a weld. Still further, in pulsed welding regimes, the wire feed speed may be altered periodically or cyclically. 
         [0026]    It should also be noted, while the above discussion relates generally to manual welding processes, the system of  FIG. 1  may also be designed for automated processes. That is, the system components may be associated with various automated equipment for supporting and moving the welding torch, and for initiating, executing and terminating welds. In many applications this would be made by the intermediary of a robot that would be programmed to go to an initial location of a weld, perform the weld, and back away to a rest or home position, or move to the position of a subsequent weld. In both manual and automated welding, moreover, information may be available and collected on various workpieces, welds within any workpiece, and this information may be stored along with weld parameters, such as voltages, currents, wire feed speeds, and as described below, stickout of the electrode. 
         [0027]      FIG. 2  is a partially broken away view of a portion of a welding torch during a welding operation. The welding torch, indicated generally by reference numeral  60  will typically include a gas nozzle  62  through which shielding gas is channeled during welding. Within the nozzle a contact tip  64  supports the welding electrode or wire  66  and transmits electric current to the electrode for supporting the welding arc. During the welding operation, a welding arc is established between the workpiece  18  and the wire electrode  66 , and the wire electrode  66  is continuously advanced at a desired wire feed speed as indicated by arrow  68 . At the same time, as the weld advances, the torch (and/or workpiece) is displaced along the direction of the weld as indicated by arrow  70 . 
         [0028]    To permit distancing the nozzle and contact tip from the progressing weld, a stickout length  72  will typically be afforded, either by manual positioning of the torch (and/or workpiece) or by an automated setting of a robotic apparatus. In either case the torch may be positioned more or less close to the workpiece, such that the electrode stickout length  72  may change. In general, welders and welding engineers designing automated systems will prefer some optimal length of welding electrode to provide the desired penetration, arc heating, melting of the electrode, and so forth. The present techniques allow for determining the stickout length of the electrode, and at least one of monitoring the stickout or controlling system components based upon the stickout. 
         [0029]      FIG. 3  illustrates a similar torch with the wire electrode retracted. In certain embodiments of the present techniques, the stickout may be controlled to allow for determination of stickout following a welding operation, and retraction of the electrode following the welding operation as indicated by reference numeral  74 . In certain applications, the desired at-rest stickout  76  may be controlled by reference to the stickout following the welding operation. For example, in some implementations, the electrode may be retracted to approximately the level of the nozzle front extremity or slightly within the nozzle to reduce the potential for touching or otherwise contacting the electrode between welding operations. 
         [0030]      FIG. 4  illustrates exemplary steps in a process for determining the stickout length. The process indicated generally by reference numeral  78 , begins with measuring current, as indicated by reference numeral  80 . The current measured at step  80  will typically be the welding current, and will be measured by a current sensor associated with at least one of the welding torch, the wirefeeder, and the welding power supply. Such current measurements are commonly made for various monitoring and control operations. In the present context, however, the current measurement is used to compute stickout as described below. Current measurements are typically made periodically during the welding operation, and many such current measurements are made at pre-determined intervals under the control of processing circuitry as described below. 
         [0031]    At step  82 , then, based upon these current measurements, a stickout parameter sample is computed. In a presently contemplated embodiment, the sample is computed according to relationships: 
         [0032]    If the wire is in a short condition (wire touching the puddle or work): 
         [0000]      Sample= I*I*C 1  EQ. 1,
 
         [0033]    If the wire is in an arc condition: 
         [0000]      Sample= I*I*C 1+ I*C 2  EQ. 2,
 
         [0000]    where I represents the measured current, and the parameter C1 is a scaling constant, such as 1600, and C2 is a scaling constant, such as 2150. In this implantation, EQ. 1 generally represents wire heating, while EQ. 2 represents wire heating plus arc heating. Those skilled in the art will appreciate that determination of whether the electrode is in a short circuit condition may be made by reference, for example, to the voltage of the welding power (which will decline precipitously due to the short circuit), and/or the current. In addition to current, other parameters such as power and resistance may also be measured and used in computing stickout. 
         [0034]    With the samples computed, in a presently contemplated embodiment multiple samples are averaged as indicated by step  84  in  FIG. 4 . This averaging allows for smoothing of the samples over time and reduction of noise. In presently contemplated embodiments, for example the samples are averaged over a relatively extended period, on the order of 0.05 to 3 seconds. Additionally, the resistance may be held constant, and the integral of I 2  may be calculated and used in computing stickout. 
         [0035]    The welding system may be configured for various welding processes, including direct current welding and pulse welding, in which sampling and/or integration is employed to calculate a stickout parameter. In pulse welding processes, the sampling rate is generally greater than the pulse frequency of the welding voltage such that the sampled data is a generally accurate representation of the welding parameter. 
         [0036]    It has been determined that the stickout length may be estimated based upon the running average of the parameter sample and the wire feed speed. For example, in a presently contemplated embodiment a look-up table is used, with interpolation, to estimate the stickout length. Specifically, by way of example only, a table of the following type may be used, where a stickout length is indicated in the left-most column (in inches), wire feed speed is indicated in the top row, and the running average of the parameter sample is indicated in the body of the table. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Stickout 
                 100IPM 
                 200IPM 
                 400IPM 
                 800IPM 
                 1000IPM 
                 1400IPM 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 ¼ 
                 1000 
                 1400 
                 1500 
                 2000 
                 2200 
                 2250 
               
               
                 ¾ 
                 900 
                 1100 
                 1350 
                 1500 
                 1600 
                 1650 
               
               
                 1¼ 
                 700 
                 900 
                 1100 
                 1350 
                 1400 
                 1500 
               
               
                   
               
             
          
         
       
     
         [0037]    In a specific example, for a wirefeed speed of 150 inches per minute (IPM), the table may be used, by interpolating between the 100 IPM and 200 IPM columns, rendering interpolated values as follows: 
         [0000]    
       
         
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Stickout 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 ¼ 
                 1200 
               
               
                   
                 ¾ 
                 1000 
               
               
                   
                 1¼ 
                 800 
               
               
                   
                   
               
             
          
         
       
     
         [0038]    If, in this case, the average parameter sample value is 1100, the stickout length may be interpolated to be between ¼ inches and ¾ inches, with a linear interpolation rendering an estimated stickout of ½ inch. A number of other methods may be devised for estimating or determinating stickout, and the present techniques are not intended to be limited to any particular stickout look-up or computation approach. 
         [0039]    The system may be calibrated during manufacture or factory testing to produce such reference look-up tables. Additionally, the system may be calibrated by users at the work site to enhance customization and accuracy of the system. For example, a user may manually measure one or more stickout lengths with the corresponding parameter samples and input the data into the system. Accordingly, the lookup tables may be updated on the fly as this calibration data is inputted. The abovementioned interpolation scheme may likewise be used to calculate stickout in such user calibrated systems. 
         [0040]    Based upon the estimation of electrode stickout, then, multiple actions may be taken by the power supply, the wirefeeder, the system components, or information may simply be stored for later reference.  FIG. 5  illustrates several such scenarios, as indicated generally by reference numeral  88 . Thus, following the stickout computation method  78 , in one contemplated embodiment, stickout is displayed for the operator as indicated by reference numeral  90 . One significant advantage of the present technique is that a unitized value for stickout may be clearly indicated, such as in inches, millimeters, or any other readily-recognized unit of measure. As described below, the stickout may be displayed on the power supply, the wirefeeder, the torch, or any other component of the system that comprises a user-viewable display. Moreover, the stickout may be displayed, in certain cases, within a welding helmet in data communication with any one of these devices. 
         [0041]    Still further, as indicated at reference numeral  92 , the system simply provide for monitoring and logging of stickout. As will be appreciated by those skilled in the art, such monitoring and logging may be associated with part identifications, specific parts, specific welders, specific systems, and may further reference dates and times, and so forth. Such data may be analyzed or inspected to detect if a certain machine or component is particularly error prone and may require maintenance. Additionally, in the event of a stickout issue, stickout data may also indicate the specific workpiece or part involved such that it can be inspected to ensure quality and weld standard. Such specifications may generally be considered performance of either the welding system or the weld. Accordingly, the system may be configured to may evaluate and store performance of the welding system or a weld based on stickout. This information may be stored on the wirefeeder, on the power supply, or on any other system component connected to these, including both local to the welding system and entirely remote from the welding system. 
         [0042]    As indicated at reference numeral  96 , the system may be designed to allow for retraction of the welding wire to a desired at-rest stickout length in both manual and automated operations. This would be typically be performed by reversal of the wirefeed motor in the wirefeeder (and/or welding torch). In certain embodiments, the welding wire may not be retracted immediately if another weld is anticipated. As such, retraction may be delayed, stopped, or lessened in order to allow for repetitive welding starts with minimal delay. 
         [0043]    Finally, in certain embodiments, particularly those involving automated welding, the system may be further include a seam-tracking application  98 , in which the seam-tracking application  98  is capable of detecting the welding status such as beginning and end of the weldline. As such, the system, upon detecting a stickout issue, may initiate seam-tracking to determine the appropriate stickout. The machine may then adjust the stickout accordingly. 
         [0044]      FIG. 6  illustrates certain functional components of the welding system described above that may be called upon for carrying out functions such as those outlined in  FIG. 5 . The stickout-responsive system  98  will typically include a current measurement component  100 . In general, this component may comprise of several components which may consist of hardware, firmware and/or software. Specifically, in currently contemplated embodiments this component will include one or more current sensors, sampling circuitry (e.g., analog-to-digital conversion circuitry), current measurement circuitry based upon the analog-to-digital conversion, and so forth. As described above, this component will provide current measurements to processing circuitry  102  that executes one or more routines stored on memory circuitry  104 . In a presently contemplated embodiment, the processing circuitry  102  may be the same processing circuitry used to control other aspects of the welding power supply, such as the generation of welding power by the power conversion circuitry. The memory circuitry  104  may be part of the processing circuitry, or may be functionally associated with the processing circuitry in a conventional manner. The memory circuitry will store one or more routines carried out by the processing circuitry, including a stickout calculation routine  106 . Here again, the routine may follow any logic capable of estimating or determining stickout based upon measured welding parameter values, and being referred to a look-up table as discussed above. Also, the stickout calculation routine may call upon various other parameters of the welding operation, particularly the wire feed speed  110  which may be the commanded wire feed speed, a fed-back wire feed speed (e.g., from a tachometer or encoder) or any other desired estimation or measurement. Particularly, the memory circuitry  104  may store different programs and look-up tables that correspond to different welding processes, wire types, and other attributes. For example, the memory circuitry  104  may include a different look-up table associated with each wire size, material, or shielding gas. Thus, the user may indicate the specific welding process or wire type they are using, and the appropriate calculation routine  106  and look-up tables may be accessed to provide the appropriate operational instructions. 
         [0045]    The processing circuitry  102  may be adapted for interaction with other system components to carry out the stickout-based operations. For example, the operator interface  20  discussed above may include one or more display windows, one of which may be dedicated to or optionally programmable to display a stickout value. As discussed above, this display  112  is conveniently in the form of an easily recognizable unit, such as inches or millimeters. 
         [0046]    The processing circuitry  102  may also be designed to operate with alarms and/or switches as indicated by reference numeral  114 . Here again, these alarms may be visual alarms, such as lights, but may also include audible alarms producing sound that can be detected by the welding operator or any other operations personnel to alert them to the fact that stickout is beyond desired limits or is beyond variability criterion. 
         [0047]    Still further, the processing circuitry  102  may cooperate with communications interface circuitry  116 , such as network interface circuitry. Conventional network interface circuitry may be employed, such as for transmitting data between the welding system and remote monitors or logs as indicated by reference numeral  118 . Here again, this data may be associated with particular workpiece designs, individual workpieces, individual welds or workpieces, welding operators, automated welding systems, dates, times, or any other useful information for storing and evaluating the quality of welds as a function of the detected stickout. 
         [0048]    Finally, the processing circuitry  102  will already be associated with a motor  46  to drive the welding wire  42  to as discussed above. For retraction of the welding wire, the processing circuitry may be capable, directly or through the intermediary of separate drive circuitry (not shown), of commanding the motor  46  to reverse the direction of feed of the welding wire so as to retract the welding wire back into a desired at-rest stickout length. In one presently contemplated embodiment an encoder  120  may be used, such as in the weld and torch or in the wirefeeder to detect the movement of the welding wire back to the at-rest stickout length. Thus, consistent stickout may be offered at the end of each welding operation, and the wire may be maintained at a desired length outside of the contact tip but within the torch nozzle, for example. 
         [0049]    While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.