SU965669A1 - Method and apparatus for controlling resistance welding process - Google Patents

Description

(54) METHOD OF MANAGING THE CONTACT WELDING PROCESS AND DEVICE FOR ITS IMPLEMENTATION

one

The invention relates to electric welding technology, in particular to the field of resistance welding, is intended to control and control the process of resistance welding and can be used in welding of small parts with an open joint zone in products of the instrument-making and electronic industries.

A known method for controlling the quality of the joint during the welding process is measured by the pressure change, at which the deviation of the welding pressure is measured relative to the initial value of the compressive force, and the resulting signal is compared with the reference value and the quality of the weld is judged by the error signal.

The method is carried out by a device for controlling the quality of the joint in the process of resistance welding, containing a load sensor, a measuring amplifier with controlled transmission coefficient, a comparison circuit, a voltage source, an electronic switch, an integrating amplifier, a control unit and a display unit 1.

The disadvantage of this pressure control method is that

it is passive because it does not improve the quality of welding, but merely states the result of the welding process. The effectiveness of such control is low. In addition, passive control on the degree of reduction

5 pressure limits the technological capabilities of the welding method due to the increased likelihood of splashes and disturbances in the stability of the process during fusion welding, when the pressure in the contact Q tends to almost zero.

Closest to the invention is a method of controlling the process of resistance welding, in which one of the parameters of the welding process is measured, compare

15, the received signal with a reference and an error signal regulates the welding mode, as well as a device containing a pressure sensor, measuring and integrating amplifiers, a source of reference signals, an electronic key, a comparison circuit,

° control unit and executive body 2.

A disadvantage of the known method and device is the poor quality of the welded joint. The purpose of the invention is to improve the quality of the welded joint. The goal is achieved by the method of controlling the welding process, in which one of the welding process parameters is measured, comparing the received signal with the reference signal and adjusting the welding mode using the error signal, the change in the rate of pressure decrease of the electrode is used as the measured parameter of the welding process on the parts to be joined. A device for controlling the resistance welding process, containing a sensor of a factor, measuring and integrating amplifiers, a source of reference signals, an electronic key, a comparison circuit, a control unit and an actuator, additionally introduced two electronic keys, a source of a reference signal, an integrator and a comparison circuit, the input of the integrator is connected to the output of the sources of the reference signal through the corresponding keys, and its output is connected to one of the inputs of the additionally introduced comparison circuit, the second input d is connected to the output of the measuring amplifier, and its output is connected through a control unit to the actuating body. FIG. 1 schematically shows a device implementing the method; in fig. 2 is a diagram explaining the essence of the method of active quality control of welded joints. The device consists of serially connected force-measuring sensor 1, measuring amplifier 2, comparison circuit 3, electronic switch 4, integrator 5, the output of which is connected to the control input of the amplifier. The voltage from the output of the voltage source 6 is applied to the second input of the comparison circuit 3 and to the input of the electronic switch 7, the output of which is connected to the corresponding input of the integrator 8, and is controlled from the welding machine. The reference voltage from the voltage source 9 through the electronic key 10 is applied to the second input of the integrator 8. The key 10 is controlled from the threshold device 11, the input of which is connected to one of the inputs of the comparison circuit 12, to the second input of which a signal from the measuring output amplifier 2; the voltage unbalance from the output of the comparison circuit 12 through the control unit 13 is supplied to the actuator 14. The implementation of the method using this device is as follows. At the beginning of the welding process, a compressive force is applied to the parts to be welded (Fig. 2). The signal from sensor 1, proportional to this force, is fed to the input of measuring amplifier 2, while the keys 4 and 7 are in the open state (Fig. 1). The voltage corresponding to the magnitude Rcdc c | bb of the course. The source of the reference voltage 6 is fed through the switch 7 to the input of the integrator 8, which acts as a reference for the reference speed of pressure reduction in the contact parts. The same voltage is simultaneously applied to the input of the comparison circuit 3, the second input of which is connected to the output of the amplifier 2. If these signals are equal, the circuit 3 is triggered and the unbalance signal from the output of the comparison circuit 3 through the switch 4 is fed to the input of the integrator 5 amplifier, which provides a normalized amplitude output signal of amplifier 2, regardless of the magnitude of the initial static pressure P, At the output of the integrator 8, a voltage proportional to that supplied to sigialu input of the reference source to the reference voltage 6. terminates the measurement preparation step pressure reduction speed. Simultaneously with switching on the welding current I from the welding machine, synchronization pulses are applied closing the keys 4 and 7. As the parts heat up under the action of the welding current, the yield strength of the material being welded decreases and the actual pressure P in the contact of parts begins to decrease (curve 2, Fig. 2) . In accordance with this, the voltage Ugyxi from the output of amplifier 2 decreases and when the value reaches the upper threshold of the device 11, specified as the beginning of the measurement of the rate of decrease in pressure, the threshold device triggers and opens the key 10. The integrator 5 switches to the pre-welding level which ensures the constant transmission coefficient of the measuring amplifier 2. With the open key 10, the input of the integrator 8 from the voltage source 9 is supplied with the reverse polarity voltage from with respect to the voltage supplied before welding. As a consequence, the voltage at the output of the integrator Ug, begins to decrease at a rate exceeding the rate of decrease in pressure and the corresponding voltage at the output of the amplifier Ua, m. As soon as the voltage from the amplifier reaches the value Ipor | The lower threshold of the device And triggered as the end of the measurement of the rate of decrease in pressure, the key 10 is closed by a signal from the output of the threshold device 11 and the Unop voltage proportional to the time interval At 2 is set at the output of the integrator 8 Since the initial voltage at the output of the integrator 8, the amplifier 2 and the threshold of operation of the threshold device 11 is constant, then the steady-state voltage at the output of the integrative accumulator is proportional to the speed reducing the pressure in contact of the parts to be welded (Fig. 2),

When the voltage at the output of the amplifier 2 reaches the level of the signal at the output of the integrator 8, the comparison circuit 12 is activated and starts the control unit 13, which at time iz turns on the actuator 14.

If the effect of disturbing factors on the welding process leads to an increase in the intensity of heating, and, as a consequence, to an increase in the rate of pressure decrease in the contact of the parts to be welded (Curve 1, Fig. 2), the moment of switching on the actuator automatically shifts to the left, since the circuit Comparison 12 occurs at a higher threshold voltage value at time tj.

The time t 1 and 12 of supplying the control pulse to the executive body is selected in preliminary experiments such that, taking into account the inertia of the switching-on regulating effect, to guarantee an increase in pressure after it reaches the minimum permissible value Pj 9 corresponding to the heating of the metal in the welding zone to the welding temperature. The constant delay time t of the control action depends on its shape and type of actuator, the choice of which is determined by the type of welded joint and the requirements for the joint in terms of strength, geometrical dimensions, appearance, etc.

For example, when butt and T-shaped welding of dissimilar active and heat-resistant materials, it is effective to apply additional slump force from a controlled electric power drive. This not only prevents splashing, but also helps to remove oxides from the joint, the flow of the necessary deformation processes in the contact parts during the formation of the joint. When welding overlapping conductors, as well as wires with

The flat part of the overlapping effective regulating effect is switching off the welding current, which prevents splashing and excessive deformation of the wire at the welding point.

Thus, this method improves the quality of welding and expands technological capabilities.

Claims (2)

1. The method of controlling the process of contact welding, in which one of the parameters of the welding process is measured, compares the received signal with a reference one and regulates the welding mode by the error signal, distinguishing it in order to improve the quality of the welded joint as a measured parameter The welding process uses a change in the rate of decrease in the pressure of the electrode on the connected 0 details. 2. A device for controlling the resistance welding process, comprising a pressure sensor, measuring and integrating amplifiers, a source of reference signals, an electronic key, a comparison circuit, a control unit and an actuator, characterized in that two electronic keys are additionally introduced into the device, an integrator and a comparison circuit, while the input of the integrator through the appropriate keys is connected to the output of the reference signal sources, and its output is connected to one of the inputs This comparison circuit, the second input of which is connected to the output of the measuring amplifier, and its output is connected through the control unit to the actuator. Sources of information taken into account in the examination 1. USSR author's certificate number 616088, cl. At 23 K 11/24, 11.05.76. 2. USSR author's certificate No. 671955, cl. In 23 K 11/24, 11.02.76 (prototype). Lowering from Seat Tire FIG.