RU72894U1 - TECHNOLOGICAL CURRENT PULSE GENERATOR - Google Patents

Abstract

The utility model relates to electroerosive methods of metal processing and can be used as a wide-range pulse generator of EDM devices.

The technical task of the utility model is to increase processing productivity due to the formation of pulses of various shapes and amplitudes in a wide frequency range and increase efficiency by reducing the power of controlling the power keys of the power amplifier.

The technical problem is solved due to the fact that a memory device, a digital-to-analog converter, a pulse amplitude regulator, a current sensor and a voltage amplifier are additionally introduced in the pulse generator, and the voltage amplifier at the input is connected to the current sensor, and at the output to the comparator, the comparator, in turn, the input is connected to a voltage pulse amplitude regulator, a digital-to-analog converter and a storage device connected in series, and the output is also connected to series-connected and a power amplifier, frequency filter and a current sensor, moreover the current through the diode sensor connected to the electrode-tool EDM gap.

Description

The utility model relates to electroerosive methods of metal processing and can be used as a wide-range pulse generator of EDM devices.

Known pulse generators of a technological current, including a power source, storage capacity with a charge-discharge circuit, control and process control units (AS USSR No. 837715, class B23P 1/02, 06/15/1981; AS USSR No. 1323268, CL B23H 1/02, 07/15/1087).

The well-known pulse generator ShGI 63-440 for electrical discharge machining of metals (Technical description ZEI 729.016.70, 1079), including a power supply, power key boards and ignition keys.

A disadvantage of the known generators is the lack of the ability to automatically control the magnitude of the current during processing, depending on the state of the interelectrode gap.

Also known is a ShGI-M2 pulse generator for electrical discharge machining of metals (ShGI-80 × 2 - 200 M 2, technical description IAVK435312-042 TO, 1991), including a power supply unit, a control system unit, power key boards and ignition keys. This generator is equipped with a current regulator located on the panel of the control unit and providing the ability to automatically control the amount of current during processing, depending on the state of the interelectrode gap. The current is regulated using the current regulator by changing the pause duration between the pulse packets. The current decreases to the minimum value if the critical state of the interelectrode gap lasts more than 5 s. or decreases partially, if during 30 s. 9 relaxation of the interelectrode gap occurred. The current increases stepwise, one discrete after 5 s. after elimination of a critical condition.

The disadvantages of this generator include the following: during electrical discharge machining, quite often the critical state of the interelectrode gap leads to a slagging process with subsequent destruction of the component and the tool electrode; stepwise increase in current with a time interval of 5 s. after

relaxation of the interelectrode gap, in the case of frequent repetition of this process, leads to a decrease in processing productivity.

Closest to the proposed technical solution is a technological current pulse generator that includes a power source, a storage capacitance with a charge-discharge circuit and a discharge key control unit, in addition, the power supply is pulsed with a storage capacity charge current control unit, while the discharge circuit contains a discharge a transistor switch, in the collector circuit of which a smoothing filter and a regenerative diode are connected, connected by the anode to the emitter, which is connected to the cathode wiping the diode and an electrode tool (Sex. model №51547, Cl. V23N 1/02, publ. 27.02.2006 g).

The main disadvantage of the known technical solution is the low quality of the layer in terms of physicochemical properties, which can be improved by increasing the frequency of technological current pulses, but this circuit, in particular the RC circuit, will not have time to respond to each discharge pulse and, accordingly, the number of discharge pulses in discharge circuit: electrode-tool-part surface remains at the same level within 60-70 Hz.

In addition, the known technical solution is characterized by a complicated electrical circuit.

The technical task of the proposed utility model is to increase processing productivity due to the formation of pulses of various shapes and amplitudes in a wide frequency range and increase efficiency by reducing the power of controlling the power keys of the power amplifier.

The stated technical problem is solved by the fact that a memory device, a digital-to-analog converter, a pulse amplitude regulator, a current sensor and a voltage amplifier are additionally introduced in the pulse generator, the voltage amplifier being connected to the current sensor at the input, and the compiler, in turn, to the input connected to a voltage pulse amplitude controller, a digital-to-analog converter and a storage device connected in series, and connected to a series connection at the output a power amplifier, a frequency filter and a current sensor, in addition, the current sensor through a diode is connected to the electrode-tool of the erosion gap.

The proposed utility model is illustrated by drawings:

figure 1 shows a block diagram of a pulse generator;

figure 2 presents the electrical circuit of the power amplifier.

The pulse generator for electrical discharge machining contains connected to the first electrode of the discharge discharge (MP) 1 first electrode of the diode 3 and the sensor input 2 breakdown of the discharge discharge, the input of which is connected to the first input of the frequency divider 4, to the second input of which the driving pulse generator 6 is connected, and the third input - encoder 5 code for the duration of the voltage pulse, the output of the frequency divider 4 is connected through the shaper 7 pause duration to the generator 8 of ignition pulses, the outputs of which are connected are connected with the first and second electrode of the EDM gap 1, a read-only memory device (ROM) 9, a digital-to-analog converter (DAC) 10, a voltage pulse amplitude controller 11, a comparator 12, a power amplifier 13, a low-pass filter 14, a current sensor 15 and an amplifier are connected in series 16 voltage, the output of which is connected to the second input of the comparator 12, the output of the current sensor 15 is also connected to the second electrode of the diode. One embodiment of the power amplifier 13 comprises a first resistor 17, the first output of which is connected to the base of the transistor 18, the collector of which is connected to the anode of the first diode 19 and the first output of the first winding 20 of the current transformer, the second output of which is connected to the first output of the second resistor 23 and the anode the second diode 24, the cathode of which is connected to the cathode of the first diode 21, the second winding 25 of the current transformer 22 is connected to the base-emitter junction of the second transistor 26, the collector of which is connected through the third winding 27 tra from the current transformer 22 to the positive bus 28 of the first power supply, the negative bus of which and the emitter of the second transistor 26 are connected to the output buses 29, 30, the input bus 31 is connected to the second terminal of the first resistor 17, the second terminal of the second resistor 23 and the cathode of the second diode 24 are connected respectively with negative and positive buses 32, 33 of the second power source, the positive bus 33 of which is connected through the third resistor 34 to the base of the first transistor 18.

The pulse generator (figure 1) works as follows.

After the pause formed by the shaper 7 ends, the generator 8 generates a pulse of MP 1. At the time of breakdown of MP 1, the breakdown detected by sensor 2, the output signal of sensor 2 of breakdown

allows the count of the divider 4 of the frequency of the pulses arriving at its second input of the generator 6 pulses.

The division coefficient of the frequency divider 4, set by the encoder 5 of the code for the duration of the voltage pulse, determines the duration of the "power" current pulse in the interelectrode gap 1.

The output signal of the frequency divider 4 blocks for the duration of the formation of the current pulse duration, the shaper 7 pauses the duration and, arriving at a part of the address inputs of the ROM 9, generates at the data inputs of the ROM 9 codes of voltage pulse shape points from a certain memory area of the ROM 9, which is set by applying the remaining address inputs of the ROM 9 of the code from the encoder 17 of the voltage pulse shape code, with which the desired shape of the current pulse in the interelectrode gap is selected 1. Codes of the points of the shape of the current pulses it approximated, pre-recorded in the corresponding memory area of the ROM 9 and stored in it permanently. The output signal from the data outputs of the ROM 9 is supplied to the DAC 10, which generates a pulse of a given shape from the digital code of the shape of the voltage pulse curve. The pulse of a given voltage form from the output of the DAC 10 through the voltage pulse amplitude regulator 11, the value of the output signal of which determines the amplitude of the current pulse in MP 1, is fed to the first input of the comparator 12, to the second input of which the signal of the current sensor 15 passes through the amplifier 16.

The signal supplied to the second input of the comparator 12 is proportional to the current value of the current in the interelectrode gap 1. It is compared with the current value of the signal supplied to the first input of the comparator 12, changing the amplitude of the voltage pulses by the voltage amplitude regulator 11 at the first input of the comparator 12, the current amplitude changes in the interelectrode gap 1.

Depending on the sign of the difference of the signals, the output signal of the comparator controls the power amplifier 13 (turns transistor switches on or off). Moreover, the switching frequency of the comparator 12 is very high and is determined by the speed and accuracy of its operation. The output signal of the power amplifier 13 is filtered by the low-pass filter 14, which, filtering the signal with the switching frequency of the comparator 12, emits a current pulse of the desired shape and, through the current sensor 16 and the diode 2, which separates the ignition and power voltage circuits, enters MP 1.

The signal taken from the first output of the current sensor 15 is amplified by an amplifier 16 and is a feedback signal fed to

the second input of the comparator 12, which is compared with the signal supplied to the first input of the comparator 12. Thus, the shape of the voltage pulse is converted to the shape of the current pulse.

After the end of the current pulse of the required shape, the signal from the output of the frequency divider 4, received at the input of the shaper 7 of the pause duration, begins the formation of a pause and the process is repeated again.

The circuit of the power amplifier 13 (figure 2) works as follows.

At a low input level, due to the current flowing through the resistor 17 and the base-emitter junction of the transistor 18, the latter is open, i.e. a current flows through the winding 20 of the current transformer 22, the magnitude of which is not more than several tens of milliamps and is mainly determined by the resistance of the resistor 23. When the input level takes a positive potential, the transistor 18 turns off and the stored magnetic field energy of the current transformer 22 causes surges of the reverse polarity at the same time three windings 20, 25 and 27 of the current transformer 22. The surge of voltage on the winding 25 causes the regenerative inclusion of the transistor 26 due to the positive feedback through the winding 27.

When the input level again takes on a low potential, the transistor 18 turns on again and, together with the diode 24, shunts the winding 20 of the current transformer 22, which leads to the cessation of the flow of control current in the winding 20, and therefore to the flow of current in the load connected to the output of the circuit. As soon as the flow of current in the load stops, the magnetizing current begins to flow in the winding 20 of the current transformer 22, and the entire cycle repeats.

The proposed electrical circuit allows increasing the current to 5.5 A, which, along with improving the quality of the coating, will allow increasing the layer thickness by increasing mass transfer, i.e. the proposed technical solution makes it possible not only to alloy, but also to restore the worn surface of the parts.

Example

For experimental verification of the claimed utility model, a batch of 20 woodworking knives was processed. -

10 pcs. - according to the proposed utility model and 10 pcs. - using the well-known ShGI generator - 80 × 2 - 200 M2.

The comparison was carried out by the time of insertion of the tool electrode to a depth of 0.6 mm, when the instability of the EDM process is most fully manifested, and the duration of processing directly depends on the efficiency of the current regulator. The cutting knives had the shape of a narrow rectangular plate 4 mm thick with dimensions of 50 × 400 mm, the plates were made of ordinary carbon steel.

A large surface of the knife was subjected to EDM, starting from the cutting edge over the entire length of the insert and with a width equal to half the width of the insert.

Doping was carried out with VK-6 brand electrodes with the following parameters: open circuit voltage - 80 V, current - 5.0 A, electrode diameter - 10 mm, processing speed - 120 mm ² / min., Alloying layer thickness - 0.20 mm, the capacitance of the capacitors is 500 μF., the pulse frequency is 200 Hz., the roughness is 4.2 Ra.

Tested prototypes confirmed the efficiency of the proposed technical solution.

The tests carried out in comparison with the known device showed an improvement in the quality of the applied coating: by continuity - up to 98%, increase in wear resistance - by 1.5 times, increase in the thickness of the applied layer - by 1.75 times, decrease in roughness - by 2 times.

Thus, the claimed technical solution fully fulfills the task.

Claims (1)

A technological current pulse generator including a power source, an electrode-instrument control unit, storage capacitors with a discharge circuit and a control unit, the discharge circuit containing a discharge transistor switch, in the collector circuit of which there is a smoothing filter and a regenerative diode connected to the electrode-tool, characterized in that a memory device, a digital-to-analog converter, a pulse amplitude regulator, a current sensor and a voltage amplifier are additionally introduced into it, the input voltage amplifier is connected to the current sensor, and at the output to the comparator, the comparator, in turn, is connected to the voltage pulse amplitude controller, a digital-to-analog converter and a storage device at the input, and also connected to a power amplifier, a frequency filter at the output and a current sensor, in addition, the current sensor through the diode is connected to the electrode-tool of the EDM gap.