RU2584058C1 - Device for plasma-electrolytic oxidation of valve metals and alloys thereof - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to equipment for electrolytic treatment of surface of valve metals and alloys thereof for formation of oxide-ceramic coatings. Device consists of power supply, two pulse voltage converters, two output filters, two current sensors, switching device, electrochemical bath with electrolyte, microcontroller, two digital-analog converters, and personal computer. Peculiar feature of device consists in that both pulse voltage converter are covered with negative feedback by current that ensures their operation in mode of program-controlled current sources.

EFFECT: technical result consists in increasing reproducibility of process of formation of oxide-ceramic coatings at changing number of processed parts, geometry of processed parts and electrolytic bath due to process control in terms of total current of process, as well as in flexible increase of output characteristics by way of combined operation of several devices for common load.

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Description

The invention relates to equipment for electrolytic surface treatment of valve metals and their alloys with the aim of forming oxide-ceramic coatings. IPC C25D 11/02, 19/00, 21/12.

A device is known from the prior art (patent RU No. 2395631, IPC C25D 11/00, C25D 21/12, 2008) for microarc oxidation of metal and metal alloy products, comprising a power source, an electrolyte bath for oxidizing the product, a power step-up transformer controlling an electronic computer based on a microprocessor with peripheral analog-to-digital converters, a current sensor and a voltage sensor, the inputs of which are connected to the oxidized product, a microcontroller control, a secondary power source, switching voltage generators.

The disadvantages of the known device are the presence of a low-frequency power boost converter, the operation of high-frequency voltage converters at high input voltages, the absence of high-frequency output filters, the use of one power transformer to operate both channels of the anode and cathode voltages.

It is also known a device (patent RU No. 2422560, IPC C25D 11/00, 2009) for microarc oxidation of metals and their alloys, containing a power source connected to a secondary power source, an electrolyte bath, the housing of which is connected through a voltage sensor and a current sensor connected in series with an oxidizable part, a control machine based on a personal computer, a step-up transformer. The known device ensures the independence of the frequency of the pulses of voltage supplied to the oxidized part, and the frequency of the change of modes from the frequency of the supply voltage, independent formation of the anode and cathode voltages.

However, the known device contains a thyristor voltage regulator and a low-frequency step-up transformer that does not meet the current level of requirements for weight and size indicators. In addition, the known device uses a two-stage voltage conversion system in both the anode and cathode arm (low-frequency boost thyristor-transformer converter and high-frequency pulse converter), which increases the number of electronic components and reduces the overall reliability of the device and the manufacturability of its production. In addition, in the known device, the outputs of the high-frequency converters are connected to the mode switch without high-frequency filters, which leads to the appearance of a high-frequency component of the current in the circuit of the workpiece, which is mainly capacitive in nature, which causes shunting of the supplied current and a decrease in the current output of the coating.

The closest to the claimed technical essence and the achieved result is a device for plasma-electrolytic oxidation of metals and alloys (patent RU 2441108, IPC C25D 11/00, C25D 19/00, 2011), which contains a power source, a bath with an electrolyte for oxidizing the product , two rectifiers, two filters, two pulse voltage converters, a driver unit, an operating mode switch, a current sensor and a voltage sensor, an analog-to-digital current converter, an analog-to-digital voltage converter, microcontrol management, control electronic computer. The known device allows you to generate alternating positive and negative voltage pulses on a galvanic cell, as well as maintain the voltage on the cells at a constant level, while the known device has two separate circuits for the formation of anode and cathode voltages. The described device is taken as a prototype of the invention.

The disadvantages of existing devices are:

- low reproducibility of coatings, arising from the need to change processing conditions when changing the number of parts, changing the geometry of the part or electrochemical cell, and due to the fact that the process is controlled in terms of the voltage applied to the bath;

- limited ability to increase the output current of the device due to the impossibility of parallel connection of several devices to increase the output power.

The objective of the invention is the creation of a new device for plasma-electrolytic oxidation of valve metals and their alloys, forming positive and negative current pulses of a given amplitude and duration, providing feedback on the output current independently in the positive and negative half-periods, which allows to increase the output power by the joint inclusion of several of the same type devices to the total load.

The technical result of the invention is to increase the reproducibility of the process when forming oxide-ceramic coatings when changing the number of workpieces, the geometry of the workpieces and the electrolytic bath by controlling the process in terms of the total process current (uniquely related to the current density on the surface of the parts), rather than applied to the voltage bath, the value of which contains difficult to control components and depends on the total current in the circuit; in a flexible capacity increase through the joint work of several devices on a common load; in increasing the level of automation of technology for plasma-electrolytic oxidation of valve metals.

The stated technical problem is solved in a device for plasma-electrolytic oxidation of valve metals and their alloys, which consists of a power source, two pulse voltage converters, two output filters, two current sensors, a switching unit, an electrochemical bath with an electrolyte and a workpiece, a microcontroller, two digital-to-analog converters, a personal electronic computer, the power source being connected to the first input of the first pulse converter voltage generator and to the first input of the second pulse voltage converter, the output of the first pulse voltage converter is connected to the input of the first filter, and its output is to the input of the first current sensor, the first output of which is connected to the second input of the first pulse voltage converter and provides negative current feedback, the second output of the first current sensor is connected to the first input of the switching unit, while the output of the second pulse voltage converter is connected to the input of filter, and its output is connected to the input of the second current sensor, the first output of which is connected to the second input of the second pulse voltage converter, providing negative current feedback, and the second output of the second current sensor is connected to the second input of the switching unit, while the first output of the switching unit unit is connected to the workpiece, and the second output is connected to an electrolytic bath with electrolyte, in addition, the first output of the microcontroller is connected to the input of the first digital-analog about the converter, the output of which is connected to the third input of the first pulse voltage converter, and the second output of the microcontroller is connected to the second digital-to-analog converter, the output of which is connected to the third input of the second pulse voltage converter, the third output of the microcontroller is connected to the driver input, the output of which is connected to the third input of the switching unit, while the input of the microcontroller is connected to the output of a personal electronic computer (PC), in addition, the microcontroller The scooter is connected to the digital synchronization bus via connector D. Thus, the totality of the features of the claimed solution allows to achieve the specified technical result.

The invention is illustrated by the functional diagram of the device (Fig. 1.) and the wiring diagram, demonstrating the ability to connect several inventions to the total load (Fig. 2.), where the following notation is introduced:

1 - power source;

2 - electrochemical bath;

3 - electrolyte;

4 - product on which the coating is applied;

5 - the first pulse voltage Converter;

6 - second pulse voltage converter;

7 - the first day off;

8 - second output filter;

9 - the first current sensor;

10 - the second current sensor;

11 - switching unit;

12 - driver;

13 - microcontroller;

14 - the first digital-to-analog converter;

15 - the second digital-to-analog converter;

16 - personal electronic computer;

G - device (unit module);

GA — anode current source;

GC - cathode current source;

CU - switching unit with driver;

MK - control microcontroller together with the first and second analog-to-digital converters;

S1, S2 - power tires;

SD - synchronization bus;

A, B, C, D, E - connectors;

N is the total number of devices working together,

at the same time, the lower index with the letter designation symbolizes the number of the device among devices operating on a common load.

The device contains a power source 1, an electrolytic bath 2 with an electrolyte 3 and a workpiece 4 placed in it, pulse voltage converters 5, 6, output filters 7, 8, current sensors 9, 10, a switching unit 11, a driver block 12, a microcontroller 13, digital-to-analog converters 14, 15, connectors A, B, C, D, E and a personal electronic computer (PC) 16.

The purpose of the inputs for each pulse voltage converter is as follows: the first is the input power from the power source, the second is the input of the current feedback signal, the third is the signal input of the amplitude of the output current pulse. It should be noted that for the formation of the pulse shape with an accuracy of 1%, the working frequency of the converters must be at least 100 times higher than the maximum working frequency of the output current.

The device has two independent current sources, which are connected and disconnected from the load (electrochemical cell with an electrolyte and a part), alternately in the sequence specified by the parameters of the current mode from the microcontroller's memory: the first current source (anode) includes a pulse voltage converter 5, output filter 7, current sensor 9, the second current source (cathode) includes a pulse voltage converter 6, an output filter 8, a current sensor 10, while connecting and disconnecting the ano sources of the current and cathodic currents to the load occurs by turning on and off the key elements of the switching unit 11, in addition, the device provides operating modes as a “master” and “slave”, which is necessary for the joint operation of several devices for a common load.

The device operates as follows.

The operation of the device begins with filling the bath 2 with the required electrolyte 3 and immersing the workpiece 4 into it. The required current mode, characterized by such parameters as the duration of the anode current pulse, the duration of the cathode current pulse, pause durations, the amplitude of the anode current pulse, the amplitude of the cathode current pulse, as well as the operating mode “master / slave” is loaded into the memory of the microcontroller 13 from the PC 16 through the connector E. Then the voltage of the power source 1 is fed to the first input q the first switching voltage converter 5 and the first input of the second switching voltage converter 6.

The microcontroller 13, in accordance with the current mode parameters stored in the memory, generates at the output 1 a signal that controls the digital-to-analog converter 14, at the output 2, a signal that controls the digital-to-analog converter 15, at output 3, a signal that controls the driver 12, the output of which is connected to the third input of the switching unit 11 , in addition, depending on the selected master / slave mode, the microcontroller 13 generates a signal to the synchronization bus via connector D, or receives a synchronization signal through l D respectively. The control analog signal from the output of the digital-to-analog converter 14 is fed to the third input of the pulse voltage converter 5, providing adjustment of the output anode current, and the control analog signal from the output of the digital-to-analog converter 15 is fed to the third input of pulse-voltage converter 6, providing adjustment of the output cathode current, and the zero level an analog signal at the third input of pulse voltage converters 5, 6 corresponds to a zero output current. In addition, the control of the digital-to-analog converters 14, 15 and the switching unit 11 is synchronized so that the switching of the load by the switching unit 11 occurs only when the switched pulse voltage converters 5, 6.

When a non-zero signal appears at the third input of the first voltage converter 5, it starts and through the output filter 7 the anode current is supplied to the input of the current sensor 9, the first output of which is connected to the first input of the switching unit 11, while a signal is generated at the second output of the current sensor 9 proportional to the flowing anode current, which is supplied to the second input of the pulse voltage Converter 5, forming the first negative current feedback circuit.

When a second voltage converter 6, which is different from the zero signal, appears, it starts up and, through the output filter 8, the cathode current is supplied to the input of the current sensor 10, the first output of which is connected to the second input of the switching unit 11, and a signal is generated at the second output of the current sensor 10 proportional to the flowing cathode current, which is supplied to the second input of the pulse voltage Converter 6, forming a second circuit of negative current feedback.

The switching unit 11, controlled by the microcontroller 13 through the driver 12, in accordance with the recorded parameters of the current processing mode, connects the first output to the first input, and the second output to the common circuit wire when forming the anode current pulse in the load, or the first output to the common circuit wire, and the second output to the second input during the formation of the cathode current pulse in the load.

If it is necessary to increase the current passed through the workpiece, the design of the invention allows you to combine several devices to work on a common load (see Fig. 2.). To do this, at least two devices G ₁ -G _{N are} electrically connected so that the connectors A ₁ -A _N are connected in parallel to the power supply 1, the connectors B ₁ -B _N are connected to the power bus S2, the connectors C ₁ -C _N were connected to the power bus S1, and the connectors D ₁ -D _{N are} connected to the synchronization bus SD, while one device, for example G ₁ , is transferred to the “master” mode by loading the corresponding current mode parameters into the microcontroller MK ₁ through connector E ₁ from PC 16, and the remaining, for example, G ₂ -G _N - transferred to the "slave mode », By downloading the appropriate parameters in the current mode microcontroller MC -MK _{2 N 2} through connectors E .. _N E of the PC 16. Thereafter, the entire set of devices G ₁ -G _N is controlled with one PC via connector E _1, wherein the microcontroller MK _{1 of the} master device G ₁ automatically distributes the set parameters of the current mode between the remaining devices G ₂ -G _N using the SD synchronization bus. In addition, the synchronization bus provides synchronous operation of the anode GA ₁ -GA _N and cathode GC ₁ -GC _N current sources, as well as the common-mode operation of the switching units CU ₁ -CU _N so that the switching states are equivalent for all cooperating devices.

A distinctive feature of the prototype is that in the proposed device, the pulse voltage converters are covered by current feedback, which ensures their operation in the mode of program-controlled current sources. Devices in the form of program-controlled current sources in the synchronization mode between microcontrollers allow you to combine several devices to work on a common load in order to increase the output current and implement the modular principle of scaling the output characteristics.

Pulse voltage converters are turned on only if it is necessary to form the corresponding current pulse in the load, the rest of the time they are turned off by applying a signal to the third input corresponding to the zero output current, which facilitates the thermal operation of the device. Switching voltage converters can be either raising or lowering depending on the voltage of the mains, provided that the maximum output voltage is in the range from 600 to 1000 V for the first switching voltage converter and from 150 to 300 V for the second switching voltage converter. The maximum output voltage is determined from the technological needs of production. When operating from 220 V or 380 V networks, the most optimal is the functioning of the first current source in the mode of a step-up voltage converter, and the second current source in the mode of a step-down voltage converter, which provides the best dynamic range of regulation and efficiency. When operating from networks of 127 V or less, both converters must be step-up, and when operating from 660 V and higher, both converters must be step-down.

The proposed device can be implemented and manufactured industrially using known radio components and devices of electronic equipment. For example, the first switching voltage converter can be made according to the bridge converter with a step-up transformer made on a N87 / ETD-59 ferrite core ("EPCOS", Germany), the second switching voltage converter - according to the step-down voltage converter, the power switches of the first and second voltage converters based on powerful field-effect transistors of the 2P829B brand (Iskra Design Bureau, Russia), if necessary connected in parallel, as a control controller of the first and second imp The pulse converter can be used with a PWM controller of type 1114EU3 (OAO NPT ElTom, Russia), galvanic isolation of the control key circuits is carried out using high-speed optical drivers HCNW3120 (Avago Technologies, USA), as a current sensor, you can use a sensor from the DTX series (NIIEM OJSC, Russia), the switching block can be manufactured using power modules based on bipolar transistors with an insulated gate of the M2TKI-50-12 type (OJSC Elektrovypryamitel, Russia).

The device layout has the following key features:

1. Input power: 220 V-1F or 380 V-3F.

2. Maximum output voltage: + 750 / -300 V;

3. Maximum output current: +6.5 A / -10 A;

4. The minimum duration of the current pulse or pause: 250 μs;

5. The maximum duration of the current pulse or pause: 10000 s;

6. The frequency of conversion of the anode current source: 200 kHz;

7. The frequency of conversion of the cathode current source: 100 kHz;

8. Weight (without PC): 7.5 kg;

9. Efficiency, excluding losses in the electrolyte:> 95%.

10. Dimensions (without PC): 350 × 120 × 250 mm;

Claims (1)

A device for plasma-electrolytic oxidation of valve metals and their alloys, containing a power source, two pulse voltage converters, two output filters, two current sensors, a switching unit, an electrochemical bath with an electrolyte, a microcontroller, two digital-to-analog converters, a personal electronic computer, and the power source is connected to the first inputs of both pulse voltage converters, characterized in that the output of the first one is connected to the input of the first liter, and its output is to the input of the first current sensor, the first output of which is connected to the second input of the first pulse voltage converter with the possibility of providing negative current feedback, the second output of the first current sensor is connected to the first input of the switching unit, while the output of the second pulse voltage converter connected to the input of the second filter, and its output is connected to the input of the second current sensor, the first output of which is connected to the second input of the second pulse converter voltage, with the possibility of providing negative current feedback, and the second output of the second current sensor is connected to the second input of the switching unit, while the first output of the switching unit is connected to the workpiece, and the second output of the switching unit is connected to an electrolytic bath with electrolyte, while the first output of the microcontroller is connected to the input of the first digital-to-analog converter, the output of which is connected to the third input of the first pulse voltage converter, and the second to stroke microcontroller connected to the second DAC, the output of which is connected to the third input of the second pulse voltage converter, the third output of the microcontroller is connected to the driver input, the output of which is connected to the third input of the switching unit, wherein the microcontroller input connected to an output of personal computing machinery.

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