Electric arc welder and controller therefor

#The present invention relates to the art of electric arc welding with a welder having a power supply of the switching type and more particularly to an electric arc welder of this type combined with a novel and unique controller.

#Electric arc welding involves the movement of an electrode toward a workpiece while current is passed through the electrode and across an arc between the electrode and workpiece. Although some electric arc welders utilize a non-consumable electrode, most of the mass production arc welding involves an electrode which is consumed during the welding process whereby the electrode is melted by the arc and deposited on the workpiece. Thus, an arc welding process includes variable process characteristics, such as wire speed or electrode speed, gas composition, electrode diameter and workpiece metal. The actual electrical arc welding process at the production site takes into consideration these characteristics and involves a non-linear complex control system which determines the applicable metal transfer mode and the electrical parameters of the power supply performing the welding process. In order to achieve desirable results, a waveform is selected having several control parameters, which waveform is customized for the exact condition of each welding application. Thus, controlling arc welding has become an art which demands substantial knowledge and experience to select a waveform having several control parameters to produce an optimum welding process. A large number of controllers have been developed for use with electric arc welders that have real time current waveforms developed by welding engineers to optimize the welding process performed in the field. To accomplish this objective, a microprocessor based controller has been developed and is now used that allows an operator in the field to select one of many welding waveforms by merely using one of several overlays. This successful microprocessor based controller is illustrated in Blankenship U.S. Pat. No. 5,278,390 that is incorporated by reference herein. By using a known template for the controller, an operator selects a welding process having the desired control parameters especially developed for the process by a skilled welding engineer. This successful controller had a certain amount of adjustability in the field; however, such on-site adjustments were limited. Mass production use of arc welders has created a demand for the ability to conveniently adjust certain control parameters of the welding cycle in the field, especially when the welding process is continued over several hours as experienced when the electric arc welders are used for a robot application in industrial manufacturing procedures. Thus, there has been developed a need for a controller to be used with an electric arc welder, where the controller can process a desired waveform that is adjusted interactively at the manufacturing site.

#The present invention relates to an improvement over the controller as generally disclosed in Blankenship U.S. Pat. No. 5,278,390, incorporated by reference herein as background information relating to the environment to which the invention is directed. In practice and under normal circumstances the controller of the present invention is used for controlling the waveform and monitoring the operating parameters of an electric arc welder utilizing a power supply of the switching type. These switching type power supplies control the real time current waveform by rapidly switching a D.C. current in a controlled fashion by a pulse width modulator, or other control device for creating a series of current pulses having duty cycles modulated to create the desired output current. Such switching power supplies are used extensively in arc welding and take such forms as an inverter, such as generally described in Blankenship U.S. Pat. No. 5,349,157, or a down chopper or other converter, as generally shown in Stava U.S. Pat. No. 4,972,064. These two patents are incorporated by reference herein to show types of switching power supplies wherein the current waveform used in a welding process is controlled by rapidly switching current pulses to the welder. Other types of switching power supplies could be used for creating a real time current waveform generator by the controller of the present invention. Indeed, a power supply where the waveform is controlled by an analog signal of a known waveform can be used in the present invention.

#FIG. 1 is the control architecture of the preferred embodiment of the controller and dedicated electric arc welder with a stand alone implementation of JAVA technology;

#FIG. 2 is a front view of the CRT screen showing the waveform and other visual devices when the controller is used to implement the control application program aspect of the present invention;

#FIG. 3 is a function block diagram of the control application program implemented in JAVA language and dedicated to a particular welder, which program is used to program the architecture shown in FIG. 1;

#Referring now to the drawings wherein the showings are for the purpose of illustrating the preferred embodiment of the present invention and not for the purpose of limiting same, FIG. 1 shows an electric arc welder A controlled by a somewhat standard microprocessor based controller B which, in accordance with the invention, is a real time control and monitor for welder A. Controller B is combined with the welder as a commercial product purchased for use in various welding processes, especially for mass production welding of consumer products, which welding is often done by a robot. The stand alone unit incorporating welder A and controller B uses any of a number of switching type power supplies, such as an inverter generally illustrated in Blankenship U.S. Pat. No. 5,349,157 or a converter or chopper as generally shown in Stava U.S. Pat. No. 4,952,064. For the purposes of simplicity, welder A is shown as a down chopper where the power supply 10 is used to switch a D.C. current at terminals 12, 14 in accordance with the operation of a switch 20. In practice, an inverter may use a plurality of switches or switches arranged in various configurations. A simplified switching type power supply utilizes switch 20 controlled by a pulse width modulator 22 driven at a pulse rate determined by oscillator 24, which pulse rate is normally 10 to 20 kHz and preferably approximately 20 kHz. Current pulses occur at a rapid rate and are directed through a relatively small inductor 30 to perform a welding process implemented between electrode E, normally in the form of an advancing welding wire, and workpiece W. The duty cycle of the various pulses of switch 20 is controlled by pulse width modulator 22 so that the waveform of the current in the welding process between electrode E and workpiece W is accurately controlled and repeated consistently. In accordance with standard practice, welder A has a freewheeling diode 32, an arc voltage sensor for creating a voltage across lines 40, 42 and a current shunt 50 for creating a voltage across lines 52, 54 representative of the arc current. The voltages across lines 40, 42 and lines 52, 54 are directed to the input of controller B for the purpose of monitoring the welding process, which process is controlled by the voltage on line 56 that changes in a real time fashion to follow the shape of a waveform governing the welding cycle of welder A. In accordance with standard practice, electrode E is an advancing welding wire represented as a wire feed device 60 having a speed controlled by and monitored by controller B as indicated by line 61. The welding process performed by welder A is modified according to the shielding gas employed in the welding process. The shielding gas is identified by data on line 62. When welder A is used for an automatic welding processes, such as robotic processes, the welding head is moved on a real time basis in accordance with a program in controller B that operates motion control device 64 in accordance with standard practice. The present invention relates to the control of welder A during the welding process and not necessarily to the individual control of the X, Y and Z motors used for adjusting the welding gun and the speed of the movement of the welding gun as schematically illustrated by motion control 64. As so far described, welder A is standard and controller B is a device well known in the art and known to manufacturers of electric arc welders having microprocessor based controllers. One such controllers is generally illustrated in Blankenship U.S. Pat. No. 5,278,390.

#In accordance with the present invention, controller B is operated by the logic on I/O conduit or bus 70, which logic is the control parameters inputted into the controller. This same I/O bus outputs data or operating parameters from controller B. These control and operating parameters are processed in accordance with a software operating system 100 that may have any platform configuration with an overlay JAVA virtual machine 102. The virtual machine loaded with one or more JAVA application programs for performing the waveform editing or soft oscilloscope functions of the invention, as hereinafter described. Hardware 104 interacts with display 110 and is controlled by manual data entry device 112 in the form of a keyboard or mouse. As so far described, the total product of welder A and controller B, with real time control and monitoring of the welder by JAVA technology, is novel in the arc welding field. Waveforms exhibited on interactive display 110 are modified by manual data entry device 112 to create a new waveform to generate the desired control parameters on I/O bus 70 for real time control of the welding process between electrode E and workpiece W. When the "scope" or oscilloscope application program in JAVA language loaded into virtual machine 102 is executed, the control parameters continue to control the welding process in accordance with the final waveform; however, visual display 110 plots the real time operating parameters of the welding process. Thus, controller B monitors the ongoing welding process dictated by waveform ultimated selected by the control application program loaded in virtual machine 102. In practice, display 110 and manual data entry device 112 are adjacent welder A; however, I/O bus 70 can be a remote communication line without departing from the intended spirit and scope of the present invention.

#In accordance with the invention, virtual machine 102 is provided with program tailored specifically to welder A, so data input indicated by block 111 relates to welder A and is converted to JAVA source mode, as indicated by block 113. The control program shown in FIG. 3 is also in JAVA language whereby the JAVA source code of the control program and the data specific to welder A are compiled and converted into byte codes as indicated at block 116. This programming procedure is well known in the art and can be accomplished by persons in the welding industry to create a stand alone welder and controller having a JAVA virtual machine for implementing the unique control program to which the present invention is directed. Compiler 114 compiles byte codes at block 116 for use by virtual machine 102. Blocks 111, 113, 114 and 116 can be a CD ROM separate from welder A as shown by line 118. The CD ROM for the particular welder A is preferred; however, a tape or telephone line could be used to load application programs into virtual machine 102. In accordance with the invention, welder A and controller B are commercial products, sold in the welding industry as a stand alone unit which is programmed by an appropriate device, in practice a CD ROM containing byte codes for application programs in JAVA language, such as an operating program illustrated in FIG. 3, a scope program illustrated in FIG. 4 or other programs for implementation by dedicated welder A.