RU1773641C - Device for automatic focussing of welding electron beam - Google Patents

Abstract

The invention relates to the field of control of welding processes, namely, to control the parameters of an electron beam welding process. The device consists of a secondary electron sensor 1, a signal driver 2, analog memory circuits 3 and 4, a comparison unit 5, a sign determining unit 6, a comparator 7 controlled by a DAC 8, a current amplifier 9, a focusing electromagnetic system 10. a control unit 11, the focusing unit 12, the deflecting system 13, the selector 14. The invention allows for automatic focusing of the welding beam in real time when the distance of the welding gun-welded part, the magnitude of the accelerating voltage and beam current are varied. 1 s.p. f-ly, 1 ill.

Description

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The invention relates to the field of control of welding processes, namely, to control the parameters of an electron beam welding process.

A device for adjusting the focus of an electron beam is known, comprising secondary electron sensors, a control unit, an electromagnetic focusing lens 1. The disadvantages of the known device are the use of two sensors that are mounted symmetrically relative to the electron beam above the product and the inability to maintain symmetry of the sensor-beam-sensor system welding process

The closest in technical essence to the invention is a device for electron beam welding containing a focusing system, a secondary electron sensor, a focusing unit and a control unit 2. The disadvantages of the known device are as follows. Information on the amount of focus shift is contained in the amplitude of the signal of the secondary electron sensor. Any change in the signal amplitude caused by destabilizing factors is perceived by the device as a focus shift, i.e. the device has low noise immunity. Scanning the surface of the parts to be welded with the focal plane of the beam requires a gap at the junction; in the absence of a gap, the device does not stabilize the focus. The device does not stabilize the focal length in real time, i.e. during welding, the amplitude of the sensor signal depends simultaneously on the size of the gap in the joint and on the distance of the surface of the parts being welded - the welding gun, which significantly reduces the accuracy of determining the magnitude of the focus shift.

The aim of the invention is to improve the quality of the weld due to the automatic installation and stabilization of the focal distance of the electron beam during the welding process in real time.

The device comprises a secondary electron sensor 1, the output of which is connected to the input of the signal driver 2, and the output of the driver 2 is connected to the inputs of the sampling and storage circuits 3 and 4, the outputs of which are connected to the inputs of the comparison unit 5. The output of the comparison unit 5 is connected to the input of the character determination unit b and the output of the comparator 7, while the output of the character determination unit 6 is connected to the input of the controlled digital-to-analog converter (DAC) 8, and the output of the comparator 7 is connected to the second input of the controlled DAC 8. The output of the controlled DAC 8 is connected to the first input of the current amplifier 9, the output of which is connected to the focusing electromagnetic system 10. In this case, the first and second outputs of the block

The control 11 is connected to the second inputs 3 and 4 of the sample-storage, its third output is connected to the third input of the controlled DAC 8, and the input of the control unit 11 is connected to the output of the comparator 7. The second input of the amplifier 9

0 of the current, a signal arrives from the output of the focusing unit 12, and a deflecting system 13 is connected to the output of the unit 12. The secondary electron sensor 1 is equipped with an energy selector 14 of electrons that constructively form a single unit.

DAC 8 is designed to generate a voltage that controls the magnitude and nature of the change in current of the focusing system. Under the influence of external control signals, the output voltage changes in magnitude, sign, slew rate, shape, which allows you to implement various modes of operation of the device, which maximize

5 satisfy the requirements of the welding process.

DAC 8 only controls the current. When a series of pulses is applied to the third input, a pulse is generated at its output.

0 voltage corresponding to the digital code. The parameters of this voltage are determined by the parameters of the pulse sequence.

The device operates as follows.

Preliminary guidance and focusing of the electron beam is carried out at a low (2-5 tA) current of the electron beam. The focusing unit 12 connected to the QT0 clone system 13 generates an alternating current in the latter, under the influence of the magnetic field of which the beam makes harmonic oscillations of small amplitude. Information about the position of the beam relative to

5 of the joint is the amplitude of the signal, the frequency of which corresponds to the scan frequency of the joint. When the coordinates of the beam and the joint coincide, in the spectrum of the sensor signal of the secondary electrons are present only

0 components that are multiples of the double scan frequency. The beam and the beam are focused and aligned at the maximum signal amplitude with a double scanning frequency. The maximum signal amplitude with a double scanning frequency is achieved by adjusting the output current of the amplifier 9, which controls the voltage from the first output of the focusing unit 12 and changing the constant value component of the second output unit

12, the output signal of sensor 1 is input to a signal former 2, where a signal with a double scanning frequency is extracted from the spectrum of the secondary emission signal. The focus position and the relative position of the beam relative to the joint are indicated using the indicator included in the shaper 2. After the pre-focusing and aiming of the electron beam is completed, the device is prepared to switch to the automatic focusing mode of the welding electron beam. The transition to welding mode is accompanied by an increase in the beam current to a nominal (working) value. The output signal of the sensor 1 is input to the shaper 2 of the signal. A constant component of the output signal of the sensor 1 is allocated in the signal driver 2. The output signal of the driver 2 is supplied to the first inputs of circuits 3 and 4.

Their operation mode is determined by command signals generated by the control unit 11. The time interval between the signal sample in scheme 3 and the signal sample in scheme 4 is determined by the value of the welding speed and the expected value of the rate of change of distance the surface of the parts to be welded - welding gun. The output signals of circuits 3 and 4 are fed to the inputs of the comparison unit 5, where two signals are compared, between which there is a time interval. The output signal of block 5 is input to the sign determining block 6, where the sign of the comparison result is determined, and the input of the comparator 7, where the magnitude of the comparison result is determined. If the output signal of block 5 does not exceed the set value, then the output signal of comparator 7 is absent, the output voltage of the controlled DAC 8 does not change, the output current of amplifier 9 remains unchanged, and the current in the electromagnetic focusing system 10 is equal to the originally set 10. In block 11 command signals are generated that control the operating mode of circuits 3 and 4, sampling and comparison cycles are repeated. If the output signal of the comparison unit 3 exceeds the set value, then the output signal of the comparator 7 displays the enable signal for the second input of the controlled DAC 8, the output signal of the unit 6 determines the direction of the output voltage of the DAC 8 from the first input, and the third DAC from the third input 8 receives sequentially a series of pulses causing successive increments of the current of amplifier 9 and current

electromagnetic focusing system 10. A change in the output signal of the sensor 1 after each current increment is processed in the former 2 and stored in 5 in circuits 3 and 4. If the output signal of the comparison unit 5 does not exceed the set value, the sampling and comparison cycles are stopped. Otherwise, the sampling-comparison cycles are repeated until the output signal of the sensor 1 reaches the maximum possible value at the current distance values, the surface of the part to be welded-welding gun, the thickness of the material to be welded, the welding current is 15 and the accelerating voltage the wife.

The electron selector 14 does not transmit low energy electrons to the sensor 1.

Structurally, the sensor 1 is made in the form of a disk, which is mounted on the lower end section of the welding gun. A through hole is made in the center of the disk to allow the passage of electrons (welding beam).

5 Selector 14 electrons constructively

made in the form of a set of metal grids that are electrically isolated from each other, the cell sizes of each grid are different. Constant potentials are applied to the grids. The number of grids, cell size and constant potentials are selected depending on the type of materials being welded. A selector 14 is mounted on the surface of the sensor 1, which faces the weld pool 5.

The device has the following advantages: it provides automatic focusing and stabilization of the focus of the welding beam directly during 0 electron beam welding; it is efficient in the absence of a gap in the joint and with the help of a welding beam from 60 W to 15 kW. The device uses an unambiguous relationship between the amplitude of the information signal and the distance of the surface of the part to be welded — the welding gun, which increases the focusing accuracy.

Claims (2)

SUMMARY OF THE INVENTION 01. A device for automatically focusing a welding electron beam, comprising a focusing electromagnetic system, a secondary electron sensor, a focusing unit, a control unit and a deflecting system, characterized in that, in order to improve the quality of the weld by stabilizing the focal distance no electron beam during the welding process, it is equipped with a signal conditioner, two sampling-storage circuits, comparing units The identification and sign of the comparator controlled digital-to-analogue convertible digital-to-analogue converter, to the third input of which is a driver and a current amplifier, and the sensor switches the third output of the control unit, to the secondary electrons through the formiro-second - the input of the control unit, and the signal output device is connected to the first inputs5 through a current amplifier connected to a sampling-storage circuit, the second inputs are co-magnetic focusing system, the blocks of which are connected to the outputs of the control-focusing unit, the outputs are connected ene deviation to laziness, and outputs connected to inputs blokan yoke and to a second input of comparator amplifiers whose output is connected to current cells. inputs of the unit for determining the sign and compara-10 2. The device pop. 1, characterized by the outputs of which are connected in accordance with the fact that the sensor of primary electrons With the first and second inputs, it is equipped with an electron selector for energy m.