Intelligent power supply | FJY Brush Plating

The characteristics and application of intelligent brush plating power supply

Abstract

Brush plating technology is a new type of surface processing method that is gradually improved, perfected and developed on the basis of electroplating (slot plating) technology. It is a special form of high-speed electroplating. Therefore, the development of brush plating power supply is synchronized with the development of electroplating power supply.

All brush plating power supplies are DC power supplies with specific auxiliary functions. Therefore, the types of brush plating power supplies can be distinguished according to the rectification method, additional functions, output waveforms, and intelligent characteristics of the DC power supply.

According to the different rectification methods, the DC power supplies used for brush plating can be divided into four categories: ① Large-capacity batteries; ② DC generators; ③ Silicon rectifier power supplies (including SCR rectifier power supplies); ④ Switching power supplies (high Frequency inverter power). The basic characteristics, development trends, and purchase principles of different types of DC power supplies are briefly described as follows.

Types of DC power supply

1. Large-capacity storage battery: storage battery is the simplest DC power supply (DC power supply that directly converts chemical energy into electrical energy). In remote and field construction sites that cannot provide industrial power and no mobile AC generators, high-power industrial batteries can be used as a simple brush-plating power supply. The inconvenience of using industrial batteries is that the output voltage of the batteries cannot be adjusted continuously. Unless it is a last resort, few people use batteries as a brush-plating power supply.

2. DC generator: A DC generator is an energy conversion device that directly converts mechanical energy into direct current. It can provide the direct current required for brush plating, and the output voltage can be adjusted at will. Although in principle, the DC generator can be used as a brush plating power supply, but it does not have many advantages compared with other forms of rectified power supply. Besides, it is bulky. Nowadays, few people use this type of power supply except for military purposes.

3. Silicon rectifier power supply (including SCR rectifier power supply): With the rapid development of high-power semiconductor technology, it has become simple and easy to convert alternating current into direct current. Silicon rectifier power supply is a form of power supply that uses high-power semiconductor devices to convert industrial AC power into DC power. For the silicon rectifier power supply for brush plating, the power frequency AC voltage is first reduced to a safe voltage (36V) through a transformer, and then the voltage is adjusted by a voltage regulator and then sent to a high-power rectifier diode (such as a rectifier bridge). The rectified output contains Ripple DC can output DC that meets the requirements of brush plating voltage after filtering and stabilizing. The quality of silicon rectifier power supply is stable and reliable, and it is the main form of brush plating power supply from the late 1970s to the beginning of this century.

If the alternating current that has been stepped down by the transformer is delivered to the thyristor, and the output voltage is changed by controlling the conduction angle of the thyristor, it constitutes the main body of the SCR rectifier brush plating power supply.

Since silicon rectifier power supplies (including SCR power supplies) must use transformers (voltage regulators), and high-current transformers must be wound with thick copper wires, this type of brush plating power supplies are usually bulky and expensive. They are gradually being replaced by switched power supplies (high-frequency inverter power supply).

4. Switching power supply (also known as high-frequency inverter power supply or pulse power supply): In recent years, with the rapid development of modern electronic technology, the stability of high-current power switching tubes (IGBT) has been significantly improved, and high-frequency/high-voltage rectification technology has made breakthroughs Sexual progress. Since the high-frequency/high-voltage rectification process does not require bulky and heavy transformers (and low-voltage regulators), switching power supplies are gradually becoming the main body of current rectifying power supplies due to their lightweight, small size, and low cost. However, if the quality of its important rectifier components is unstable, compared with the traditional silicon rectifier power supply, the reliability of the high-current switching power supply is slightly worse. Because the current required for brush plating usually does not exceed 200A, using a switching power supply as a brush plating power supply basically has no reliability problems.

Basic characteristics of brush plating power supply

Brush plating is a special form of slotless plating. Therefore, compared with the DC power supply for electroplating, the brush plating power supply should have the following characteristics.

The power supply should have constant voltage output characteristics: in electroplating production, the output current of the power supply is generally controlled. Once the current value of the power supply output is approved, the current value should be kept stable during the entire electroplating process. Therefore, the electroplating power supply output has Constant current characteristics. The power supply used for brush plating is different. During the brush plating process, the size of the contact area between the anode and the workpiece cannot be strictly controlled, and the phenomenon of open circuit often occurs, so it is not suitable to use a plating power supply with constant current characteristics. Therefore, the DC power supply used for brush plating should have constant voltage characteristics, and the constant voltage value should not change with the change of the load (that is, it has flat and hard external characteristics).
The output voltage of the power supply should be continuously adjustable: during brush plating, multiple steps (such as electro-cleaning, activation, plating formation, etc.) are required to complete a complete brush plating process. Each step is required to be completed under a specific voltage. Therefore, The output voltage of the brush plating power supply should be adjusted arbitrarily according to the requirements of the process steps. In the early brush plating process, the output voltage range of the brush plating power supply is required to be 0 ~ 30V (if the FJY series brush plating products are used, the voltage range is 0 ~ 15V).
The output polarity of the power supply can be changed arbitrarily: during the brush plating process, the output polarity of the power supply is often changed. For example, the workpiece is used as a cathode during electric cleaning; when activated, the workpiece is used as an anode; when a coating is deposited, the workpiece is used as a cathode. Therefore, the brush plating power supply should have a polarity conversion function. The easiest way to change the output polarity of the power supply is to swap the cord clamp. It can also be commutated with double-pole double-throw switches, double-circuit relays, or solid-state electronic commutation circuits. In order to facilitate the maintenance of the power supply, it is best to use dual-circuit relay commutation.
The power supply should have over-current and short-circuit protection devices: during the brush plating process, short-circuit phenomena often occur (such as damaged anode sheath, etc.). In order to prevent damage to the power supply or burn the workpiece due to a short circuit, the brush plating power supply should have a short circuit and current limiting protection circuit to ensure that no accident occurs when the external circuit is short circuited.
The power supply should have a power recording device (coulomb meter): each step of the brush plating process is an electrochemical reaction process, and the amount of electrochemical reaction (reaction amount) can be expressed by Coulomb's law (or Faraday's law of electrolysis), that is, the substances involved in the reaction The amount of is proportional to the amount of electricity flowing through the loop. If the electrochemical reaction that occurs is a reduction reaction of deposited metal, the amount of deposited metal is proportional to the amount of electricity flowing through the loop. Once the current efficiency (or power consumption coefficient) of reducing metal from a certain plating solution is determined, the quality (or thickness) of the deposited metal coating can be converted according to the electricity value recorded by the electricity meter.
The power supply is light and reliable; the brush-plating power supply should be small in size, light in weight, easy to transport (repair on-site with faulty equipment), and reliable and durable.

Trends of brush plating power supply

In recent years, there has been a lot of publicity about the new type of brush-plating power supplies, and the titles are also varied, which is very confusing. For novices who wish to purchase brush plating power supplies to engage in brush plating technology applications, they usually do not know that the improvements in brush plating power supplies are in line with the future development direction of brush plating technology. This article puts forward several key points for readers' reference.

The brush plating power supply for maintenance should be lightweight and practical. Brush plating repairs usually need to go to the fault equipment site for service. If the brush plating power supply is too bulky (such as silicon rectifier brush plating power supply), it is inconvenient to go to the construction site for service (such as going to the field site to repair excavators, mining machinery, road construction machinery, etc.) ). Therefore, the research and development of reliable and portable high-frequency inverter brush plating power supply has wide applicability.
The power output waveform can be set manually. In the field of electroplating, for different types of plating, people will choose power supplies with different output waveforms for electroplating (such as half-wave rectifier power supply copper plating, asymmetric AC-DC power supply low-temperature iron plating, pulse power supply gold plating, etc.). To learn more about the research results on the correlation between the power output waveform and the coating performance, please refer to the academic papers published by Fei Jingyin and others (eg: "Electrodeposition of Zn-Co alloys with pulse containing reverse current", Electrochimica Acta, 2005, 50 (13); "Preparation of high-P nickel-based alloy coating by pulse electrodeposition method", Chinese Journal of Corrosion and Protection, 2012, 32(6), "Pulse Electrodeposition High Speed Ni Process Research", Chinese Journal of Corrosion and Protection, 2013, 33 (4) etc.). Although brush plating is a slotless plating method, its working principle is the same as that of electroplating. Therefore, the output waveform of the brush plating power supply will also have a significant impact on the performance of the coating. However, in the brush plating industry, few people have studied the dependence between the power output waveform and the performance of the brush plating layer. Some power suppliers claim that they can provide pulsed power. In fact, what they provide is only high-frequency inverter pulsed power, which is not a multi-waveform output power that people want to modulate on demand. In foreign countries, people use computer-aided control technology to produce large-current brush-plating power supplies with artificially adjustable output waveforms, which lays the foundation for the development of new functional brush-plating.
Special purpose brush plating power supply with single chip microcomputer data acquisition, analysis, output and control. The brush-plating power supply with the most complete functions currently available on the market is the brush-plating power supply with a coulometer. The current integration circuit is used to record the amount of electricity flowing through the circuit during brush-plating, which provides a basis for calculating the thickness of the brush-plating layer. However, in the actual brush plating process, the current efficiency of the plating solution is constantly changing. The brush plating machine with only power recording cannot meet the needs of precise control. Instead, intelligent data collection and control. For example, in the process of application of surface brush plating technology for anti-stick buckle of drilling tools, deep hole repair of coal mine machinery, non-cyanide gold plating of precision parts in aerospace, brush plating of anti-electromagnetic interference surface of long-range missiles, and high-conductivity surface modification layer of controlled nuclear fusion, etc. It is necessary to strictly control the process parameters of each step, such as voltage, time, speed, power and even real-time display of coating thickness. The development of special-purpose intelligent brush plating power supplies and precise control of the brush plating implementation process are the key elements to ensure the quality of the coating .
Research and development of practical special brush plating power supply. Although the brush plating power supply with more functions provides convenience for the technical research and engineering application of the brush plating workers, in the actual brush plating production process, sometimes a practical brush plating power supply with simple operation is required. Such as general tinned power supply, decorative gold-plated power supply, hydraulic rod (cylinder) repair the special power supply, etc. For users who use FJY oil cylinder repair technology to repair local defects in the hydraulic system, the output current of the power supply can meet the construction requirements within 50A. Because of the partial damage of the hydraulic system, although the depth is large, the damaged area is small, and the power supply does not need a large current output during brush plating. It is easier to go to the site (especially in the field construction site) for maintenance services by choosing a brush plating power supply with lower power and lightweight. For users who use FJY non-cyanide gold plating technology, they only need to precisely control the output voltage. The gold-plated power supply should have the function of displaying the plating thickness. Because gold raw materials are expensive, the thickness of the gold-plated layer must be precisely controlled during the brush plating process to avoid unnecessary waste.

FEIST intelligent brush plating power supply with the capability of monitoring and displaying coating thickness in real-time

Although the brush plating power supplies provided by domestic and foreign brush plating power suppliers have many varieties and different names, they can be classified into two categories according to the basic functions of the power supply: 1. DC power supply with polarity conversion function (internal replacement To relay), is the most sold brush plating power supply on the market; 2. On the basis of the commutation DC power supply, it has a built-in fuel gauge (Coulomb meter), which is a brush plating power supply commonly used in China in the late 1980s.

Northwestern Polytechnical University has been committed to the research, development and application of brush plating technology and products since the 1960s. Published nearly 200 academic research papers related to brush plating, combined with the needs of aviation, aerospace, and marine engineering to develop brush plating power supplies with special characteristics. FEIST coating thickness real-time display brush plating power supply is currently the only practical new type of brush plating power supply that can directly display the thickness of the brush plating layer in China. Different from the brush plating power supply with a built-in fuel gauge, the thickness display window of this power supply can display the true value of the current coating thickness, which is convenient for the operator to accurately control the brush plating process and provides convenience for achieving precise and flexible brush plating.

Declaimers

The purpose of introducing brush plating power supplies is to facilitate beginners or purchasers of brush plating power supplies to quickly understand the basic characteristics and development status of brush plating DC power supplies, as well as the matters that should be paid attention to when purchasing brush plating power supplies. Although the content described in the article is objective and true, it does not deny that there may be more abundant brush plating power supplies on the market.