SU1743765A1 - Method of, and device for, automatic control of resistance welding process - Google Patents

Abstract

Usage: in contact welding of small parts with an open zone of formation of a joint in the manufacture of products of the electronic and instrument-making industry. SUMMARY OF THE INVENTION: A method for automatically controlling a resistance welding process consists in measuring the reduction in compression force at the contact of the parts to be welded, comparing it with the reference one, and turning off the welding current when they are equal, while setting the reference level for reducing the force as an inclined direct compression force. to zero at the moment of time determined during the uncontrolled welding process with the lowest possible value of the welding current. The device contains a trigger, generator, regulator legal for trade prescaler, counters, tsifroanalogo- stems transducers, force-measuring sensor, amplifier, comparator circuit, a key, the welding power source. 2 sec. f-ly, 2 ill.

Description

The invention relates to resistance welding and can be used mainly in the manufacture of products of electronic equipment and instrumentation during welding of small parts with an open zone of formation of a joint.

The aim of the invention is to improve the process stability and quality of welding.

FIG. 1 is a block diagram of a device implementing a control method; in fig. 2 - diagrams explaining the essence of this method.

The device contains serially connected force-measuring sensor 1, measuring amplifier 2, comparison circuit 3, electronic switch 4, welding power source 5. In addition, the device

contains a series-connected generator 6, an adjustable frequency divider 7, a subtracting counter 8 and a first digital-to-digital converter 9, a trigger 10, a series-connected summing counter 11 and a second digital-to-analog converter 12, and a synchronizer 13, with the output of the first digital-to-analog converter 9 connected with the second input of the comparison circuit, and the input of the reference voltage with the output of the second digital-to-analog converter 12, the input of the summing counter 11 is connected to the output of the generator 6, the installation inputs in zero and one trigger 10 are connected respectively with the outputs of the comparison circuit 3 and the synchronizer 13, the direct and inverse outputs of the trigger 10 are connected respectively to

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the enable inputs of the summing 11 and deducting 8 counters, and the installation inputs to the initial state are one for subtracting 9 and zero for the summing 11 meters are connected to the output of the synchronizer 13,

The device works as follows.

The parts to be welded are placed between the electrodes and compressed with the force chosen according to the mode. On a Start command from the welding machine, the synchronizer 13 sets up the measuring amplifier 2, the trigger 10, the subtracting counter 8, the summing counter 11, and all the outputs of the summing counter 11 are set to zero, and the output of the subtracting counter 8 - single logical level. The reset signals of counters 8 and 11 prohibit their operation. After a time interval sufficient to establish the initial static compressing force, the synchronizer 13 removes the signal to prohibit the operation of the counters, and the trigger 10 allows the summing counter 11 to work. The rectangular pulses from the generator 6 begin to flow to the counter 11 and increase its contents. This leads to an increase in the output voltage at the output of the second digital-to-analog converter 12, respectively, the output voltage at the output of the first digital-analog converter 9 increases. This voltage goes to one of the inputs of the comparison circuit 3, to the second input of which through the measuring amplifier 2 the signal goes from the load sensor 1. When the voltage at the output of the first digital-to-analog converter reaches 9, the magnitude is quite close, but less than the voltage at the output of the amplifier 2, Corresponding to the initial static compressive force, the comparison circuit 3 triggers, which flips trigger 10 and opens electronic key 4. Trigger 10 with its outputs prohibits operation of summing counter 11 and enables operation of subtractive 8, while summing counter 11 becomes self-blocking and pulses from generator 6 through an adjustable frequency divider 7, they begin to flow into counter 8 and reduce its content, respectively, the voltage level at the output of the first digital-to-analog converter 9 decreases,

This voltage decreases linearly and is a reference. Simultaneously with the start of operation of the subtracting counter 8, the electronic key 4 allows the operation of the source of welding current 5.

As the parts heat up with a welding current pulse (capacitor or one-half-period), the metal in the welding zone softens and the force at the contact of the parts being welded begins to decrease (Fig. 2). When the signal from the sensor drops to the level specified by the reference signal from the output of the first digital-to-analog converter, a comparison circuit 3 is triggered, which triggers trigger 10 and closes the electronic switch 4 with its output signal. This leads to the inhibition of the subtractive counter 8 and the welding current is turned off. The totalizing counter does not start until it is reset from self-locking by the initial setting signal from the synchronizer 13. This completes the welding cycle. The PTS-19 piezoceramics with a diameter of 4 mm, the measuring amplifier — operational amplifiers K140UD8, comparison circuits — the integral comparator 521 САЗ, electronic key — K2184KN1 microcircuit, welding current source — capacitor energy meter, adjustable frequency divider, and counters — digital microcircuits were used as a force sensor. K155IE6, first and second digital-to-analogue converters K572PA1 microcircuit, trigger - K155TM2 microcircuit, generator and synchronizer circuit implemented on K155 integrated circuits .

This method and device were implemented in automatic equipment for welding contact nodes of resistors of the type ML T equipped with a mechanism for compressing and precipitating parts, a capacitor metering device for welding current energy, and an automatic control and quality control system for the connection, consisting of the control device itself, electrode equipment, force sensor, synchronization and rejection devices. A tin-plated copper tinned wire with a diameter of 0.6 mm was welded with tamping nickel-plated caps 0.2 their thickness.

The initial static compressive force of the parts was set to 6 daN. The parameters of the welding current pulse were as follows: the current amplitude was 2.1 kA, the rise time to the maximum was 1.5 ms, and the total pulse time was 4 ms. The basis of the choice of the mode parameters was the hall. No. The fulfillment of two conditions of the uncontrolled welding process with technological deviations in the real range:

heating the weld zone to the melting temperature and splash of the molten metal at a current value close to the amplitude one;

metal deposition along the entire length of the overhang of the wire, equal to its diameter. The use of a current pulse with more than necessary energy to heat the welding temperature with real technological deviations ensures that there is no penetration in the joint. In this case, the task of controlling the welding process is to prevent the splash of the molten metal. This is ensured by the choice in preliminary experiments of the optimum angle of inclination of the reference voltage level and automatic adjustment of its initial value.

The reference level for reducing the compressive force is set in the form of a straight line connecting the point corresponding to the value of the static compressive force at the initial moment of time, with the point corresponding to the point in time at which the compressive force becomes zero during an uncontrolled welding process. current, ensuring a high quality connection.

The impact on the welding process of a disturbing factor, for example an increase in the amplitude of the current, ceteris paribus, leads to an increase in the intensity of heating. In the process oscillogram (Fig. 2a), this is expressed in the fact that the compressive force at the contact of parts decreases with greater speed (Fa curve) than during welding with a given current amplitude (FI curve). Accordingly, the reference level in the form of an inclined straight force curve F2 is reached earlier, and the time allowed for the actuation of the actuator switching off the welding current is increased. The current is shut off before the splash of molten metal from the weld zone is prevented.

In another case, when a disturbing effect on the welding process is a decrease in the initial static compressive force (Fig. 2.6), simultaneously with a change in the force, the angle of inclination of the reference level also changes due to automatic adjustment of its initial value. This ensures timely shutdown of the welding current and, accordingly, reduction of the likelihood of molten melt

metal when welding at low initial static forces x.

The use of the invention allows to significantly improve the stability of the process and the quality of welded joints.

Claims (2)

1. The method of automatic control of the process of resistance welding, which consists in measuring the decrease in the compressive force at the contact of the parts being welded, comparing it with the reference level and turning off the welding current when reaching their equality, characterized in that, in order to increase the stability of the process and the quality of welding, the reference level is set to decrease linearly from the point corresponding to the magnitude of the static force compression at the initial moment of time, to the point corresponding to the point in time at which the compression force becomes equal to zero with an uncontrolled welding process with the lowest possible value of the welding current. 2. A device for automatic control of the process of resistance welding, containing a serially connected load sensor, measuring Amplifier, comparison circuit, electronic key and welding current source, characterized in that, in order to increase the process stability and quality of welding, a synchronizer, a trigger, coherently connected generator, an adjustable frequency divider, a subtractor counter / k -l first digital-analog converter are entered into it , and also consistently connected summing counter and the second a digital-to-analog converter, the input of the summing counter is connected to the output of the generator, and the output of the second digital-analog converter is connected to the input of the reference voltage of the first a digital-to-analog converter, the output of which is connected to the second input of the comparator unit, wherein the input of the setting to zero of the trigger is connected with the output of the reference circuit, and the direct and inverse outputs of the trigger connected to the resolution inputs of the summing and subtractive counters, respectively, and the synchronizer outputs are connected to the measuring amplifier, the installation input to the trigger unit, the second input of the welding current source and the installation inputs to the initial state - the unit for the subtracting and zero for the totaling - counters.