SU460139A1 - The method of resistance spot welding - Google Patents

Description

(54) METHOD OF CONTACT DOT ELECTRIC WELDING

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This invention relates to resistance welding.

There is a known method of contact spot electrofusion, in which, during the compression of parts with electrodes, the transient resistance is measured and its specified value is switched on, the welding current is switched on.

When the value of the transient resistance deviates from the specified value of the welded part, the latter is removed from the machine, and the BOB is re-prepared (maintenance, which is a rather time-consuming operation.

The proposed method makes it possible to increase labor productivity due to the fact that the specified value of the transient resistance is obtained by compressing with an increasing force, after which the welding current is corrected depending on the steady state value of the compression force of the electrodes.

The proposed method can be carried out, for example, due to the refinement of the pneumatic system of the electrical circuit of a welding machine with an interrupter PIT-100-4.

FIG. 1 is a diagram of the redesign of the drive compression of the welding machine; in fig. 2 - finalized electrical circuit breaker concept.

The compression drive of the welding machine contains a valve 1, an additional electropneumatic valve 2, which stops the flow of compressed air into the working chamber of cylinder 3 when a predetermined contact resistance is reached at the contact of parts. Consistently with

Valve 2 is equipped with a throttling valve 4, which provides a gradual increase in pressure on the electrodes to eliminate measurement error due to the inertia of the measuring device. A pressure sensor 5 is installed in the working chamber of the cylinder; operating resistance 6 of which is included in the resistance circuit of the Regulator Heating PIT-100-4 interrupter to effect additional correction of the welding current when the deviations of the steady pressure on the electrodes from the optimum value, an increase in pressure causes an increase in current.

In the secondary circuit of the welding machine, a power contactor 7 is installed, breaking the secondary circuit when measuring the contact resistance at the contact of the parts.

The process of compressing the parts, measuring the transient resistance and welding is carried out as follows.

When the starting pedal of the welding machine is pressed, after the time regulator relay 8 is activated, valve 1 is activated, and

the measurement circuit is powered. Relay

9 triggered and ICBOHM n. about. contact includes a relay circuit 10.

Relay 10 is activated and turns on-its n. about. contact-winding electropneumatic Pana 2, and N. 3. contact breaks the circuit of the relay 11, which is his n. 3. By contact — prepares for switching on the target of relay 12. Compressed air from the reducer flows through valve 1 and electromotive valve 2 into the working chamber of the cylinder, the electrodes begin to compress the parts. When the closure of the electrodes on the part of the relay 12 and its n. about. contact includes a circuit of the measuring device, namely, millivoltmeter 13. The process of measuring the resistance 14 begins at the electrode-part-electrode section, whereby the pressure on the electrodes constantly increases.

The voltage drop on the measured resistance 14, resulting from the current flowing through it, the value of which is regulated by the resistance 15, is constantly compared with the set voltage from the photocell 16. The magnitude of this voltage is regulated by the resistance 17 and (determines the selected resistance in the contact details. At the initial moment, when the pressure on the electrodes is insignificant, the resistance in the contact of the parts is large, the voltage drop across resistance 14 is large, and the needle of millivoltmeter 13 deviates to the left or stands as the pressure increases, the resistance at the contact of the parts decreases, the voltage drop across the resistance 14 also decreases, and the needle of the millivoltmeter 13 begins to deflect to the right.

When the specified resistance is reached at the contact of the parts, the deviation of the arrow of the millivoltmeter 13 is such that the photocell 18

shaded by a light screen located on the arrow of the millivoltmeter 13. When this happens, relay 9, relay 10 and electric pneumatic valve 2 are turned off, the air supply to the working chamber is stopped.

N. 3. The relay contact 9 turns on the relay 11, the relay winding circuit 12 turns off, the measuring device switches off. N. On the contacts of the relay 11 switch on the relay 19 and start the lamp 20 in the time controller.

Relay 19 its n. about. contact includes the winding of the power contactor 7, which connects the secondary circuit of the welding machine to the electrodes.

At the end of the delay time, "compression" switches on the welding current, the magnitude of which is corrected by the pressure sensor b.

At the end of the delay time, the forging of the time controller relay 8 is switched off,

the electrodes are opened, the measuring circuit is turned off, and the initial state arrives.

Subject invention

The method of contact spot electric welding, in which during the process of compressing parts with electrodes they carry out a transition resistance and for a given value turn on a welding current, characterized in that, in order to increase productivity, a given resistance value is obtained by compression by an increasing force, after which the welding value is corrected current as a function of the magnitude of the compression force of the electrodes.