An automatic electric welding system for maintaining uniforme heat in a welding operation

Automatic electric welding system designed to maintain uniform heat in the welding operation so that

THE BUDD COMPANY, intends to obtain privilege of invention in Portugal.

Welding control systems have taken different and very varied forms. Many systems have been used for current or voltage monitoring and the use of their data for signals that are included in the backfeed to control welding operation.

In order to provide an average caloric input value, individual parameters such as current, voltage and speed of movement have also been used. This technique, however, produces a control signal of the fait accompli and does not allow alteration of the caloric intake values ​​inherent in the process of maintaining a constant heat intake level.

There are, however, many cases where it is important that the welding has to feed it a constant heat input. An example of the importance of keeping heat intake constant in the arc welding operation is the manufacture of a truck wheel. In this operation, there is a disk manufactured from a relatively thin, cold-worked material that is sun-fed to a relatively thick rim, generally consisting of a hot-rolled product. And in this wheel welding it is important that the caloric intake values ​​are well defined so that there is a minimum penetration of the weld and the heat inlet while preserving the resistance of the disJo

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cold working, which, to be achieved, implies that the annealing of the tej zone is minimal? affected mint.

It is an object of the invention to introduce an improved welding system in which heat input is kept relatively constant.

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? It is a second object of the invention to introduce an improved welding system in which heat input is kept uniform and at a certain: i. so that the penetration is minimal and the welding is reliable without giving rise to excessive annealing of the welded parts together.

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According to this invention there is an electrical signal. Standard shape that forms and represents the speed of movement of the workpiece, the arc current, and the arc voltage required to maintain a uniform heat in said part. Representative of the same parameters, there are electrical signals that form during operation. Two of the signs

Electrical signals are combined with the standard electrical signal, giving rise to an output signal essentially equal to the signal representative of one of the parameters used in the production of the standard electrical signals. Combined electrical signals refer to the same parameter as current. The output of the combined signals is compared with the corresponding electrical signal that forms during operation, giving an error indicator signal. 0 error indicator signal is used._z It is used in the return feeder network to control the function chosen to maintain the desired heat uniformity.

Other objects and advantages of the invention will be made clear and patentable to those skilled in the art from reading the specification and claims that follow, taken in conjunction with the accompanying drawings.

Fig. 1 is a block diagram illustrating the welding system according to this invention;

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Fig. 2 is a block diagram illustrating the welding system of Fig. 1 in greater detail; and

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Figs. 3a and 3b represent on two separate sheets, joined together, which constitutes a schematic diagram, part of which in blocks, illustrating circuit details of one embodiment of the invention.

In the description of this invention, it is assumed that there is a common welding system in which the arc welding operation is performed on two pieces to be connected together. In the arc welding operation, a welding tool may be entered wherein the welding wire is continuously fed from the welding gun to the workpiece to form an arc between the wire and the piece to heat both the wire and the weld. unworked metal and give rise to welding.

In these common or conventional systems, the three parameters involved are the arc welding voltage, the arc current, relative to the advancing speed of the welder wire, as well as the movement speed of the weldment. In accordance with this invention, there is a control signal which is produced which takes into account a predetermined arc voltage, a predetermined arc current (ie, weld wire advance location) and a predetermined velocity. of the workpiece. An electrical signal is produced which represents the appropriate combination of these three parameters. Caioric absorption is the energy in joules per inch of the length of the workpiece. And this sign represents the heat entered and applied to said part, which heat must be kept constant during the welding operation.

With reference to fig. 1, from it we can see that there is a multiplier-divider circuit 10 adapted to receive a number of signals, namely the arc welding current I_ft from line 12 formed on welding machine 14, arc welding voltage E1 formed on line 16, and velocity S of the workpiece from the welding instrument formed on line IS. The signals of lines 12, 16 and 18 are analogous voltage signals representative of the parameters involved.

Calibration control signal Hç is formed on line 20 and applied to circuit 10. The control signal

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The caloric value is an analog signal which is predetermined θ representative of the arc voltage, arc current and workpiece speed programmed for the welding machine. The heat control signal dB represents the amount of heat that is desired for the sun joint. Dadura. The circuitry shown in block 10 is designed to perform a number of calculations to form an E signal indicating output error at line 22.

In block 10, in addition to several multi-splitter-splitter circuits, there is a comparator circuit, which we will explain in detail below. In the illustrated embodiment, the actual welding current is compared with the calculated current Ig to produce the caloric control signal on the line.

The algebraic comparison of these two signals produces an error indicator signal on line 22. This caloric control signal or error indicator is used to accelerate or retard the wire feed mechanism, which in turn will directly affect the arc current to stabilize it at the standard value determined by the caloric control signal produced on line 20.

heat control signal is multiplied by the signal representing the welding speed.

The product is further divided by the actual arc voltage signal producing an output signal proportional to the current required to produce the desired heat. Actual arcing current I 'of line 12 is subtracted or algebraically compared with the resulting signal from the calculation made on the basis of the caloric control signal, workpiece speed and arc voltage, giving the line error indicator signal. 22 which, in turn, is used to accelerate or retard the drive mechanism of the wire wire as well as its advancing speed in the welding machine 14.

The circuitry covered by dialog 10 illustrates how the error indicator signal is produced by the algebraic sum of two sliding signals. In some cases, it may be desirable to use the input voltage signal to produce an error indicator signal or, in another case, the signal representing the speed of the workpiece to produce the error indicator signal, comparing each signal separately with each other. the standard signal that corresponds to it.

• Referring to Fig. 2, there are three parameters initially involved in producing analog signals.

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The heat control signal is formed by circuit 24 representing joules per inch (2.54 cm) of the workpiece. The signal produced by circuit set 26 is determined by operating on the three parameters, namely control heat, arc value and workpiece speed, until an analog signal representing the current required to produce the desired heat input is reached. Hj-. □ Circuit 24 output signal is applied to the multi circuit. splitter-splitter 26. A speed indicating signal from a suitable circuit transducer that measures the speed of the workpiece is conditioned and graduated in circuit 28 for application to the splitter-circuit 26, and in circuit 26 which operates at multiplication of the signals of the heat input circuit 24 by the speed conditioning circuit 28. 0 The arc voltage signal is packaged in circuit 30 and fed into multiplier-splitter circuit 26, being combined with the product of the two signals of circuits 24 and 28, and giving a signal representing the ideal current signal used to form the ideal heat input signal at 24. The product of the caloric input signal by the conditioned speed signal is divided by the arc voltage signal, giving a signal representing the ideal current signal. This current signal is the guiding standard to follow in order to maintain the process with the desired uniform heat absorption. Control power source 32 is the source used to supply power to the various circuits involved.

The output signal of the multi-divider circuit 26 is summed with the arc current signal of circuit 38 at point 36 by summing resistors 34 and 74. The error indicating signal at point 36 from circuits 26 and 38, is amplified by amg. 40. The signal amplifier circuit 40 produces a signal indicating error in line 22 which is applied to control the wire 44 drive mechanism that is part of the welding machine 43. For purposes of illustration, there is a welding gun 45 disposed in a suitable location for feeding wire 47 to weld workpiece 49, which part is operated by conventional means. The truck wheel to which we have already referred is an example of illustration of the work to be done.

The wire feedrate has to do with the arc current. When the wire enters the arc or its puddling proceeds too quickly, the arc current will rise due to the power source.

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-6 constant power energy and will melt more of the wire 47. If the wire 47 enters the arc too slowly, the current will be reduced to maintain the arc at a preset length (arc voltage ) and do not melt as much of the wire. There is therefore a direct relationship between the wire feedrate and the arc current, so it is relatively easy to control the wirefeed velocity; otherwise it would be almost impossible to control the current itself.

error indicator signal is applied to the wire feeder motor circuit which causes the wire feeder motor to accelerate or delay response to instantaneous signal BS values. Due to the return feeder network, the instantaneous error indicating signal is reduced to an acceptable low value. Basically, this system consists in comparing a pre-calculated value of one of the welding parameters with the raal value of the same parameter obtained during the welding operation.

Referring to the combined drawings 3a and 3b, they illustrate in detail the Operation circuits of the various blocks of FIG. 2. The heart or center of the system resides in circuit 26 which is an integrated circuit which performs multiplier and divisive function. This special circuit receives the control signal of the caloric intake circuit 24, multiplied by the speed indicator signal from the speed conditioner 28, dividing the respective product by the voltage signal of circuit 30, obtaining an output signal that represents the arc coherent to control.

integrated circuit 46 &amp; an extra-standard element that receives a digital speed control signal at input 48 and converts it to a proportional DC voltage. The input signal to circuit 46 may consist of a series of pulses, for example, counting the number of teeth of the motor drive gear or by other applicable processes. The teeth of the gear in question, for example, may fall under a sensory element and produce impulses. These sensory elements are of the ordinary type and well known to those skilled in the art.

The variable resistance 50 S is used to determine the exact scalar factor that gives a specific output voltage for a given number of even second gear teeth, representative of the transmission speed. For example, the scalar factor may

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1 volt equal to 1 inch (25.4 cm) per minute of welding speed.

integrated circuit 52 is an impedance compensating amplifier for adapting the signal to the low processing impedance of integrated circuit 54. integrated circuit 54 makes it possible to change the input speed on the processor in order to correct the speed changes at which operation The welding force is subjected when the center of rotation of the moving part is a fixed installation within which the diameter of the workpiece may vary.

Circuit 24 comprises an integral circuit 56 and a potentiometer 56, which makes it possible to choose the required shutdown control. The control is an analogous voltage proportional to the input of shutter jacks per inch (2.54 cm). For example, 10 volts in a potentiometer may equal 100,000 joules per inch (2.54 cm). Potentiometer 60 is a control element which makes it possible to regulate the gain and start performing the appropriate multiplier-splitter functions of circuit 26.

Controls 61 and 62 of the control power source have the function of regulating the integrated circuit 26 so that it performs this multiplying-divider operation linearly over a wide range of backgens ranging from levels from C 8 to about 0.01 to 10. volts over each of the three signal inputs.

The arc voltage, which is received directly from the welding circuit between the anode (wire) and the mass of the welding circuit of the part to be welded, develops through resistors 64 and 66. These resistors have the function of grading the voltages. higher for the welding arc to the appropriate analog level required by integrated circuit 26.

It is in the integrated circuit 66 that the current signal processing is done. This current is measured by the high current shunt in series with the mass of the welding circuit. The differential voltage across shunt 70 is fed into the integrated circuit 6B via the back feed resistor 72. This resistor 72 determines the gain of the amplifier integrated circuit 68 and has the same scalar factor in amps as the output of circuit 26 has in amps.

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The polarity of the output signals of circuits 26 and 38 is such that, when combining the output signals of circuits 26 and 38, the output of circuit 38 is subtracted from the output signal of integrated circuit 26.

&lt;4 In this way a vol7 / ting error indicator 36 is formed which is the difference between the ideal current signal of the circuit 26 and the actual signal of the current.

X of circuit 38. This is the error indicator signal which, drawn from resistor 76, is applied to the internal circuit.

Ador grinder 78 of circuit 40.

integrated circuit output circuit 78 is also controlled by potentiometer 80, with which it is possible to make an adjustment which at the output of the circuit. 40, provides a reference level to lend a minimum wire feed rate according to the wire gauge specific to the wire gauge at that time inside the machine, the output signal from circuit 40 is applied to a pair of diodes 02 and 84 of the wire feeder motor control circuit within the welding machine (Fig. 2).

Several of the detail elements used in the electrical circuits referred to herein are well known to those skilled in the art. For example, re. The illustrated resistors are used to determine the voltage levels at which the various integrated circuits will operate. And the various capacitors are used to couple or shunt signals in a well known manner.

This invention has been first described in connection with the simple or collective comparison of representative signals of welding parameters. And, as stated above, any of the three parameters, arc current, arc voltage, or velocity of p £. can be used for producing error indicator signals. This means that the circuit, the multiplier-divisor 26 will take different forms. : · To perform different mathematical operations, foj?

itself is well known until the desired error indicator signal is reached.

As noted, this invention has introduced means for producing relatively uniform heat intake over the workpiece.

This is important when joining or welding elements that have two different characteristics. As already said, one of the elements

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may be a cold worked part, while the other may be a hot rolled part. And in order to achieve a good welding joint between the two parts without causing annealing of the cold-rolled parts, it is necessary to operate with a compatible and certain heat intake so that the quality of the obtained welding is the best possible.