CN100528445C - Two-stage welder and method of operating same - Google Patents

Abstract

The present invention provides an arc GMAW welding machine (A) comprising a high-speed switching power supply (10) with a controller (130) that operates between a workpiece (W) and a The gap between the electrodes (E) of (W) produces the first or second welding process. The first process uses a first current waveform and the second process uses a second current waveform. A circuit is provided for switching between the first and second welding processes, the switching circuit comprising a counter for counting waveforms in the first and second processes, and a circuit (190) for switching between the welding processes in progress When the waveform count of the welding process reaches a preselected value for such a welding process, the ongoing process is switched to another welding process.

Description

Two-stage welding machine and method of operation thereof

technical field

The present invention relates to the field of arc welding machines, and more particularly, to an arc welding machine with dual-stage or two-mode operation and a method implemented by the dual-stage arc welding machine.

Background technique

By way of background, co-pending Application No. 866,358, filed May 29, 2001, is hereby incorporated by reference along with documents incorporated by reference in that application. Kawai 4,889,969 shows a switch for switching between DIP welding and pulse welding, which is incorporated by reference as a background art.

Arc welders of the GMAW type are usually powered by a high-speed switching power supply or a power supply with a controller that controls the current waveform during the welding process. The Lincoln Electric Company of Cleveland, Ohio has pioneered the idea of an arc welder with a waveform controller that controls the shape of the current waveform in each cycle by using high frequency current pulses, the amplitude of each pulse Controlled by a pulse width modulator. In these welding machines, the waveform of the current is precisely controlled to perform different welding processes such as pulse welding, constant pressure welding, spray welding, pulse welding, short arc CV welding and STT welding. In these processes, the waveform of each welding cycle is controlled by a pulse width modulator to generate a series of welding cycles that perform the specified process. Such arc welders are very versatile; however, they operate in selected modes by controlling the pulses generated by the waveform controller.

Contents of the invention

The present invention relates to an arc welder of the above type in which the controller alternates between two independently distinct welding processes or welding modes. According to the invention, a pulse shaper or pulse generator shapes the train of pulses forming the first welding process. The controller is then switchable to be able to perform a second welding process by implementing a series of different pulse waveforms constituting different modes of operation. By counting the cycles in the first mode of operation, the first process is terminated and the second process is initiated. Thereafter, the cycles of the next process are counted until they reach a set value indicating that the welder will switch back to the first welding process. Thus, the arc welder has the ability to perform two independent welding processes by switching the controller from one operating mode to the other. Through the unique dual-stage or dual-state operation of the arc welder, the welder is capable of performing welding operations that alternately use a first process and a second process. For example, a high energy process is performed for a short period of time, and then the welder switches to a low energy welding process. If these two processes are STT, the low energy STT cycle is realized after the high energy STT cycle is realized. Thus, in one embodiment, the first process is a high energy process and the second process is a low energy process. The cycle count of each process is used to perform an overall welding operation by sequentially implementing the first and second welding processes in the welding process. As an example, in a specific embodiment, the first process is a constant pressure spray welding process with high heat. The second process is a pulsed GMAW or low heat welding process. In a welding operation, the controller first executes a first process for several cycles, and then executes a second process for several cycles. In another embodiment of the invention, the first process is a pulse welding process, wherein the pulses are of high energy or heat. The process in turn uses a low heat STT soldering process for many cycles. By alternating between the pulse period and the STT period, a desired overall welding process can be performed. In another embodiment, the first process is a high heat pulse welding process. This process is transformed into a second welding process, and the second welding process is a short arc constant pressure welding process. In yet another embodiment, the first process is a high heat pulse welding process. The second welding process is a series of pulses where the energy of the pulses is determined by closed loop feedback of the applied power. Yet another example of the present invention is a pulse welding operation in which the first series of pulses is the positive electrode that generates high heat. The second series of pulses in the pulse welding process are negative, including electrode constant voltage pulses. By switching between these welding processes, the actual welding operation can be controlled so as to optimize the performance of the welder.

According to another solution of the present invention, the first welding process of the dual-stage or dual-state electric arc welding machine is a pulse welding process. This process continues until the arc voltage shows a short circuit. Then, the two-stage welder switches to a short circuit cleaning process, such as an STT welding cycle. In the preferred embodiment, the signal converted from the pulsed welding process is not only dependent on the short circuit indicated by the interruption of the arc voltage, but also on the time of the timer. The arc welder control changes from the first welding process in pulsed mode to the short circuit clearing process only if the short circuit persists for a set period of time. The timer is preferably set to indicate that the short circuit is maintained for at least 1.0 ms, and preferably longer than a set time in the range of at least between 0.2 and 0.5 ms. Therefore, only when there is an actual short circuit, instead of an initial short circuit, does the arc welder switch to the second welding process for clearing the detected short circuit.

In accordance with the present invention there is provided an arc welding machine comprising a high speed switching power supply having a controller which produces first and second welding processes across a gap between a workpiece and an electrode moving towards the workpiece . The first process uses a first current waveform and the second process uses a second current waveform. A circuit for switching between first and second welding processes, wherein the circuit includes a counter for counting waveforms in the first and second processes. The welder switches from the ongoing welding process to another welding process when the waveform count of the ongoing welding process reaches a preselected value for each welding process. By using the dual stage welder, the arc welder can switch between two independently distinct welding processes based on counts or other parameters.

According to another aspect of the present invention, there is provided a two-stage arc welding machine of this type, which includes a high-speed switching power supply with a controller for generating a pulse wave welding process and a welding process for clearing the short circuit detected. process. When the arc voltage is lower than a value indicating a short circuit, a circuit is activated to generate a short circuit signal, and a switch is provided to switch the controller from the pulse wave process through a process change signal formed with the short circuit signal. Transformed into a short-circuit clearing process. In one solution of the present invention, the two-stage welding machine includes a timer, and the timer generates the switching signal only when the short-circuit signal remains for a set time, and the set time is about greater than 1.0 ms, and preferably greater than one A setting time ranging from 0.2 to 0.5ms. Thus, when the short circuit remains for a preselected period of time, the two-stage welder switches from the pulse mode of operation to the short circuit clearing mode of operation. In the preferred embodiment, the short clearing mode of operation is an STT welding process.

According to yet another aspect of the present invention, there is provided a method of operating an arc welder of the type comprising a high speed switching power supply with a controller. The controller passes through a gap between the workpiece and an electrode moving toward the workpiece through a wire feeder to generate first and second welds. The first process of the method has a first current waveform and the second process has a second current waveform. The method includes switching between first and second welding processes and is accomplished by counting waveforms in the first and second processes. When the waveform count of the ongoing welding process reaches a preselected value, the ongoing welding process is switched to another welding process. In another aspect of the present invention, there is provided a method of operating an arc welder including a high speed switch and a power supply having a controller for generating a pulse wave process and a short circuit clearing welding process. The method includes generating a short circuit signal when the arc voltage is lower than a value indicative of a short circuit, and then converting the controller from a pulse wave process to a short circuit clearing process through a switching signal generated by the detection of the short circuit signal. In this method, the switching signal is generated only when the short-circuit signal is maintained for a set time, which is actually less than 1.0 ms, and actually roughly in the range between 0.20 and 0.50 ms.

The main object of the present invention is to provide a two-stage arc welding machine capable of performing two welding processes alternately during a signal welding operation.

It is a further object of the present invention to provide a dual stage arc welder as described above having a counter capable of counting a process cycle to determine when a change is made in the process being performed by the welder.

Another object of the present invention is to provide a two-stage arc welding machine as described above, which performs a pulse welding process until a non-initial short circuit is detected. The two-stage welder then switches to a second mode of operation for clearing short circuits.

Another object of the present invention is to provide a method of operating the two-stage arc welding machine as described above.

It is a further object of the present invention to provide an operation of a dual stage arc welder as described above, wherein the dual stage involves one of a plurality of combinations of a different first welding process and a distinctly different second welding process. These two processes alternate back and forth during a single welding operation.

These and other objects and effects will become more apparent from the following description taken in conjunction with the accompanying drawings.

Description of drawings

Fig. 1 is the combined block diagram and the wiring diagram that represent the preferred embodiment of the double-stage arc welding machine of the present invention;

Figure 2 is a flow chart representing in block diagram format a method and operation of a dual stage arc welder in which a detected non-initial short circuit alters the welding process being performed;

Fig. 3 is to represent the flow chart that further realizes in the two-stage welding machine that constitutes according to the present invention with block diagram format;

FIG. 4 is a current graph showing the operation of a two-stage welder according to the invention embodying the invention shown in FIG. 3. FIG.

Detailed ways

Referring now to the accompanying drawings, wherein the purpose of these illustrations is to illustrate a preferred embodiment of the invention and not to limit the invention, Fig. 1 shows a novel two-stage welding machine A having a power supply 10 comprising A high speed switching power supply is shown as a converter 12 having a three phase input power supply 14 which is converted by a rectifier 16 to a DC rail power supply 20,22. The output winding 30 of the converter 12 is the primary winding of a transformer T having a secondary winding 32 for supplying current to a rectifier network 40 . The network provides a current potential through positive lead 42 and negative lead 44 . A smaller standard inductor 50 is connected to a standard contact tip 54 through which the electrode 60 is passed which forms the electrode E spaced from the workpiece W thereby defining a space through which current can flow during arc welding. arc gap. The welder A performs various types of arc welding by passing a current of a preselected waveform through a gap between an electrode E and a work W. As the arc melts the electrode 60 and workpiece W to perform the welding operation, the wire feeder 100 pulls the electrode from the spool 102 at a speed (WFS) determined by the rotational speed of the motor 104 . The speed is read by a feedback tachometer 110 and controlled by the input voltage of the pulse width modulator 112 output by the error amplifier 114 . The amplifier has a first input 120 representing a desired electrode feed speed (WFS) voltage. The speed can be controlled by an analog circuit or rather a look-up table of the waveform controller 180 . Input voltage 120 determines the speed of motor 104 , the actual speed of which is monitored by tachometer 110 for comparison with the voltage on line 120 . Actual speed feedback is the voltage on input line 122 . In this way, the electrode feed speed is consistent with the welding process that welder A is performing. The current waveform through the electrode E and workpiece W is controlled by a software controller 130, which type of software controller 30 includes a software pulse-width modulator 132 for A pulse rate of 0 produces a voltage on output control line 134. Thus, the high frequency pulse on line 134 is controlled by the voltage on line 140 which is the output of a second error amplifier 150 having a first input controlled by a current sense or sense shunt 152 . The voltage on line 154 represents the arc current of the welding process. The command signal on line 160 is compared to the actual arc current represented by the voltage on line 154 to enable pulse width modulator 152 to track the desired waveform produced by waveform controller or generator 180 via command line 160 . The electrode feed speed of the error amplifier 114 is also controlled by the waveform controller or generator. Generator 180 is a cooperating type generator so that command signal 160 and the electrode feed speed signal or voltage (WFS) on line 120 are coordinated.

According to the new solution of welding machine A, a switch 190 is provided, which is actually a software switch, as shown in FIG. 1 , which has a first position 192 and a second position 194 . With the switch in position 192, waveform controller 180 is controlled by a first process A of process control system 200 according to process A. In this way, the process control system 200 is connected to the cooperative waveform controller 180 so that the process A of the waveform controller 180 can be realized by the controller 130 . Likewise, with switch 190 in position 194 , process control system 202 causes waveform controller 180 to implement second process B via signals on command line 160 . Thus, by reversing switch 190 between positions 192,194, welder A is able to perform two independent welding processes. Of course, switch 190 can be provided with more than two positions in the present invention so that the welder can perform more than two welding processes sequentially or sequentially, if such operation is desired. In practice, it is preferable that welder A is only capable of alternately performing two independent welding processes. According to another aspect of the invention, the position of switch 190 is controlled by logic on dashed line 210 from cycle counter 212 output. The counter counts each cycle in process A or in process B. At the end of the count, as set by count selector 214 or count selector 216, logic on line 210 changes switch 190 to other positions enabling other welding processes. The counter 212 counts to a value CA, and then changes to process B which is held until the counter counts to a value CB. The switch 190 then changes back to the first process, Process A. In the preferred embodiment, one of the processes is a high heat process and the other process is a low heat process. The values CA and CB are essentially the same. Thus, the welding operation includes a low heat portion and a high heat portion which are repeated throughout the welding process to be able to control the performance of the operation, whether it is STT, pulsed or otherwise. As shown, different welding processes can be alternately selected by means of a counter. In fact, welder A can interact to determine the transition from one process to another by a parameter different from the count value. For example, voltage sensors 170 to 172 generate a voltage that detects a short circuit and is used in FIG. 2 for transition between a first process A and a second process B, where the second process is an arc clearing process. Counting significant differences, the parameters of the interaction were chosen to enable switching to a preselected process after a given process transitions to a detectable welding condition.

In fact, process A is the usual high-energy process, and process B is a low-energy process. The count values CA and CB are essentially the same. In order to change the welding operation, the value CA is increased, or the value CB is decreased to increase the heat during welding. Likewise, to reduce heat, the value CA is reduced or the value CB is increased. Of course, combinations of these increases or decreases can be used in selecting the total heat required for the welding process. In a preferred embodiment, Process A and Process B are the same, but have different waveform sizes. It can be pulse welding or STT welding. However, according to the present invention, these procedures may be completely different. For example, in practice, process A is a high heat constant pressure spray welding process, while process B is a pulsed GMAW low heat process. Counter 212 is set by count selectors 214, 216 to the total heat required for the welding operation. In fact, process A is a high heat pulse welding process, while process B is a STT welding process with a lower electrode feed speed. Moreover, in practice, process A is a high-heat pulse welding process, and process B is a short-arc constant-voltage process. In another embodiment of the present invention, the process A is a pulse welding process, and the process B is a closed-loop control process, such as a process in which the current is controlled by an output power supply. In yet another embodiment of the present invention, process A is a pulsed positive electrode constant voltage welding process, and process B is a pulsed negative electrode constant voltage welding process. In an embodiment of the present invention, a polarity reversing switch is added to the output circuit preceding inductor 50, while the corresponding polarity circuit is switched to switch 190. Other embodiments of the invention include different combinations of welding processes to be able to perform all welding processes required.

An interactive control system 220 is schematically illustrated in FIG. 2 in which a waveform generator and controller 222 generates voltages on control line 134 as previously described. The controller 130 is in block 222 . As shown in FIG. 1 , this voltage, along with the voltage output by voltage sensor 170 onto line 172 , controls power source 12 monitored by process control network 224 . The timer 226 of the process control network is set to a time typically greater than 1.0 ms, preferably greater than the set time in the normal range of 0.2-0.5 ms. The output of the timer network is directed to logic on line 232 of decision block 230 for determining if there is a short detected for a time greater than the timer 226 set time. The position of switch 190 is controlled by decision block 230 . When there is a short circuit that exceeds the time set by timer 26, switch 190 is changed to position 194. Thus, when there is a long-term non-initial short circuit, switch 190 is changed to another position to perform the second welding process. In an embodiment of the invention, the first process is a pulsed waveform controlled according to a system-determined waveform shown at block 240 . Block 242 represents a system for generating STT waveforms or other short-circuit clearing welding processes. System 220 executes a first mode of operation defined as a system-controlled pulse waveform represented by block 240 . Whenever a short occurs, the voltage on line 172 drops below a threshold. This identifies a short circuit. This detection condition is timed by timer 226 . If the short circuit time exceeds the time set by the timer, the logic on line 232 points to the decision block that there is no non-initial actual short circuit. The logic immediately changes the software switch 190 to an arc clear welding process, denoted as an STT process. When the short circuit clears according to the short circuit clearing process, the voltage on line 172 immediately changes to a plasma potential or arc voltage. This condition is above the threshold and will cause decision block 230 to shift switch 190 to position 192 to achieve the pulse shape controlled by the system represented by block 240 . Thus, the system 220 does not involve a cycle counter, but instead detects welding parameters as the actual welding process changes from one welding process to another. This process will happen quickly and generate whenever the selected parameters are detected.

In FIGS. 3 and 4 , system 250 includes a low heat soldering process represented by block 260 . Process A is a low heat STT soldering process. Likewise, a high heat STT welding process is represented by block 262 . Counter 212, as shown in FIG. 4, causes the first STT pulse 260a to be processed. Logic on line 120 toggles switch 190 to position 194 after period counter 212 has counted the expected number of STT pulses 260a. As shown in FIG. 4, this produces a larger or hyperthermic STT pulse 262a. These high heat pulses are counted according to the selected number of counters 212 . Thus, the number of waveforms or cycles of low heat and high heat STT can be adjusted to determine the total heat in a welding process.

The present invention relates to a two-stage or multi-stage welding machine capable of sequentially implementing substantially different welding processes. Preferably, the duration of these processes is determined by a counter; however, a parameter may be used for switching between welding processes. Only representative processes are discussed, and other welding processes may be used in practicing the invention.

Claims (68)

1. An arc GMAW welding machine comprising a high-speed switching power supply having a controller which produces a first or second welding process in the gap between a workpiece and an electrode moving towards said workpiece, the said first welding process uses a first current waveform, said second welding process uses a second current waveform, and a circuit for switching between said first and second welding processes, said circuit comprising a counter for counting said waveforms in said first and second welding processes, and a circuit for when said waveform count of said welding process in progress reaches a preselected value for that welding process , the ongoing welding process is changed to another welding process among the first and second welding processes. 2. The arc GMAW welding machine of claim 1, wherein said first welding process is a low thermal surface tension transition process. 3. The arc GMAW welding machine according to claim 2, characterized in that: said second welding process is a high heat surface tension transition process. 4. The arc GMAW welding machine according to claim 1, characterized in that: said second welding process is a high heat surface tension transition process. 5. The arc GMAW welder of claim 1, wherein said first welding process is a high heat process and said second welding process is a low heat process. 6. The arc GMAW welder of claim 1, wherein said first welding process is a pulsed welding process. 7. The arc GMAW welder of claim 6, wherein said second welding process is a surface tension transition process. 8. The arc GMAW welding machine according to claim 1, characterized in that: the second welding process is a short arc constant voltage process. 9. The arc GMAW welding machine according to claim 1, characterized in that: said first welding process is a constant pressure spray welding process. 10. The arc GMAW welder of claim 9, wherein said second welding process is a pulsed welding process. 11. The arc GMAW welding machine according to claim 1, characterized in that: said first welding process is a closed-loop power feedback welding process. 12. The arc GMAW welder of claim 11, wherein said second welding process is a pulsed welding process. 13. The arc GMAW welder of claim 1, wherein said first welding process is a high heat process. 14. The arc GMAW welder of claim 13, wherein said second welding process is a low heat process. 15. The arc GMAW welder of claim 1, wherein said second welding process is a low heat process. 16. The arc GMAW welder of claim 1, wherein said first welding process is a positive electrode process and said second welding process is a negative electrode process. 17. The arc GMAW welder of claim 16, wherein said preselected value is substantially the same during both said first welding process and said second welding process. 18. The arc GMAW welder of claim 14, wherein said preselected value is substantially the same during both said first welding process and said second welding process. 19. The arc GMAW welder of claim 7, wherein said preselected value is substantially the same during both said first welding process and said second welding process. 20. An arc welding machine comprising a high speed switching power supply having a controller for generating a pulse wave welding process and a surface tension transition welding process, a circuit where the arc voltage falls below a value indicating a short circuit , it can be activated to generate a short circuit signal, and a switch, which can switch the controller from the pulse wave welding process to the surface through a process change signal formed with the generation of the short circuit signal Tension transition welding process. 21. The arc welder of claim 20, including a timer for generating said switching signal only when said short circuit signal is maintained for a set time. 22. The arc welder of claim 21, wherein said time is generally greater than 1.0 ms. 23. The arc welding machine of claim 21, wherein the time is greater than a set time ranging from 0.2 to 0.5 ms. 24. An arc welding machine comprising a high speed switching power supply having a controller for generating a pulse wave welding process and a short circuit clearing welding process, a circuit which, when the arc voltage is below a value indicative of a short circuit , which can be activated to generate a short circuit signal, and a switch capable of switching the controller from the pulse wave welding process to the short circuit clearing via a process change signal formed with the generation of the short circuit signal welding process. 25. The arc welder as claimed in claim 24, including a timer for generating said switching signal only when said short circuit signal is maintained for a set time. 26. The arc welder of claim 24, wherein said time is generally greater than 1.0 ms. 27. The arc welding machine of claim 24, wherein the time is greater than a set time ranging from 0.2 to 0.5 ms. 28. A method of operating an arc GMAW welder comprising a high-speed switching power supply having a controller that generates power in the gap between a workpiece and an electrode that is moved toward said workpiece by a wire feeder A first or second welding process, the first welding process using a first current waveform and the second welding process using a second current waveform, the method comprising: (a) switching between said first and second welding processes; (b) counting said waveforms during said first and second welding processes; and (c) switching from an ongoing welding process to another one of said first and second welding processes when said waveform count of the ongoing welding process reaches a preselected value for that welding process. 29. A method according to claim 28, wherein said first welding process is a low thermal surface tension transition process. 30. A method according to claim 29, wherein said second welding process is a high thermal surface tension transition process. 31. A method according to claim 28, wherein said second welding process is a high thermal surface tension transition process. 32. A method according to claim 28, wherein said first welding process is a high heat process and said second welding process is a low heat process. 33. A method according to claim 28, wherein said first welding process is a pulse welding process. 34. A method according to claim 33, wherein said second welding process is a surface tension transition process. 35. A method according to claim 28, wherein said second welding process is a short arc constant pressure process. 36. A method according to claim 28, wherein said first welding process is a constant pressure spray welding process. 37. A method according to claim 36, wherein said second welding process is a pulse welding process. 38. A method according to claim 28, wherein said first welding process is a closed loop power feedback welding process. 39. A method according to claim 28, wherein said second welding process is a pulse welding process. 40. A method according to claim 28, wherein said first welding process is a high heat process. 41. A method according to claim 40, wherein said second welding process is a low heat process. 42. A method according to claim 28, wherein said second welding process is a low heat process. 43. A method according to claim 28, wherein said first welding process is a positive electrode process and said second welding process is a negative electrode process. 44. A method according to claim 43, wherein said preselected value is substantially the same during said first welding process and said second welding process. 45. A method according to claim 41, wherein said preselected value is substantially the same during said first welding process and said second welding process. 46. A method according to claim 34, wherein said preselected value is substantially the same during said first welding process and said second welding process. 47. A method of operating an arc welder comprising a high speed switching power supply having a controller for generating a pulse wave welding process and a short clear welding process, the method comprising: (a) capable of generating a short circuit signal when the arc voltage falls below a value indicative of a short circuit; and (b) switching said controller from said pulse wave welding process to said short clearing welding process by a process switching signal generated in response to formation of said short circuit signal. 48. A method as claimed in claim 47, comprising: (c) The change signal can only be generated when the short circuit signal is maintained for a set time. 49. A method according to claim 48, wherein said time is usually greater than 1.0 ms. 50. A method according to claim 48, wherein said time is greater than a set time ranging from 0.2 to 0.5 ms. 51. A method according to claim 50, wherein said short clearing welding process is a surface tension transition process. 52. A method according to claim 49, wherein said short clearing welding process is a surface tension transition process. 53. A method according to claim 48, wherein said short clearing welding process is a surface tension transition process. 54. A method according to claim 47, wherein said short clearing welding process is a surface tension transition process. 55. An arc welding machine comprising a high speed switching converter based power supply providing a current waveform for a specific welding process between an electrode and a workpiece controlled by a series of currents from a pulse width modulator generation of pulses having a width determining the real-time current of the waveform, and a switch for alternating between two welding processes based on a signal to the switch. 56. The arc welding machine of claim 55, wherein said switch is operated in response to a counter for counting cycles. 57. The arc welding machine of claim 55, wherein said switch is operated in response to a sensed welding parameter. 58. The arc welding machine of claim 55, wherein said switch is operated in response to an arc voltage level detected by a sensor. 59. The arc welding machine of claim 55, wherein said switch is operated in response to a timer. 60. An arc welding machine comprising a high speed switching converter based power supply providing a current waveform for a specific welding process between an electrode and a workpiece, said waveform being generated by a waveform generator, said waveform generating having a pulse width modulator output according to a selected input to said waveform generator's input circuit, and a switch such that said selected input circuit operates based on a signal to said switch at Change between two welding processes. 61. The arc welding machine of claim 60, wherein said switch is operated in response to a counter for counting cycles. 62. The arc welding machine of claim 60, wherein said switch is operated in response to a sensed welding parameter. 63. The arc welding machine of claim 60, wherein said switch is operated in response to an arc voltage level detected by a sensor. 64. The arc welding machine of claim 60, wherein said switch is operated in response to a timer. 65. An arc welder comprising a high speed switching power supply having a controller that utilizes a first current waveform comprising a first series of pulses to produce a pulse wave welding process, and utilizes a current waveform comprising a second series of pulses The second current waveform produces a short circuit clearing welding process; a circuit capable of being activated to generate a short circuit signal when the arc voltage falls below a value indicative of a short circuit; and a switch capable of passing a short circuit signal in response to said short circuit signal A process change signal is generated to change the controller from the pulse wave welding process to a short clear welding process. 66. The arc welder of claim 65, including a timer for generating said changeover signal only if said short circuit signal is maintained for a set period of time. 67. The arc welder of claim 65, wherein said time is generally greater than 1.0 ms. 68. The arc welder of claim 65, wherein said time is greater than a set time in the range of 0.2 to 0.5 ms.

Images