The Application of Vacuum Configuration Software in Electron Beam Furnace Vacuum System CHEN Hua, SUN Tao, ZHANG Zhou-Ping, YU Da-Yuan (College of Mechanical and Electrical Engineering, Shaanxi University of Science and Technology, Xianyang 712081, Shaanxi, China) Based on the analysis of the causes of the instability of vacuum in electron beam furnaces, A new vacuum system control scheme and its algorithm. The new system has a stable vacuum and convenient adjustment, which greatly improves product quality and output.
Electron beam furnace is a kind of vacuum melting equipment that utilizes the kinetic energy of high-speed electron beam to transform into heat energy and melt the metal. Vacuum, melting power and smelting speed are the main process parameters. First of all, both the thermodynamic and dynamical aspects, the high degree of vacuum is good for the removal of impurities. Secondly, the degree of vacuum also affects the emission of the electron beam. If the vacuum degree is lower than 1d2Pa, the glow discharge is liable to overload the device and the melting cannot be performed. Therefore, it is required that the vacuum system has a large capacity for exhaust gas, and the gas discharged during the smelting process can be quickly eliminated, and at the same time, its ultimate vacuum degree is required to be high.
In addition, the fluctuation of the power supply voltage causes a change in the rotation speed of the mechanical pump motor, which affects the instability of the vacuum degree, and even the equipment cannot work normally. At the same time, due to over-current and phase loss caused by the heat of the motor burned, it will also cause damage to equipment and work in progress. Therefore, the control of the furnace vacuum is very important.
1 vacuum system configuration and pull single crystal process 1.1 vacuum system configuration Northwestern Institute of Nonferrous Metals 20kW electron beam vacuum system consists of a mechanical pump and a diffusion pump in series. The vacuum system configuration is shown as 20 kW.; electron beam furnace vacuum system. 2 The process flow of the device when pulling the single crystal 1 Pass the cooling water first and turn on the compressed air; 2 Turn on the power and start the furnace body pump; 3 Open the diffusion pump immediately, and after 5 minutes, open the main valve; D Valve, clamping material rod; after completion of sealing material sealing furnace, close the main valve to open the pre-pump valve; 6 When the vacuum pumped to 3.8 102Pa, close the pre-pump valve, open the main valve, open the valve at the same time; 7 continue to pump Vacuum, until the pressure is less than or equal to 3102Pa; Teng cathode, plus the main high-voltage power supply, the electron gun begins to smelt the metal, adjust the filament current to 10A, turn on the excitation; the hopper stick smelting is completed, cut off the high pressure; 1 After the billet cools down Close the big valve and open the furnace body bleed valve.
If you need to continue work: 1 open the take-out door to take out the smelted blank and install a new material stick; 2 repeat the 5G process; if it is necessary to stop the furnace: stop the diffusion pump first, close the large valve after cooling for about 1 hour, and close the main valve , Stop the mechanical pump, stop the cooling water, compress the air, cut off the power supply.
1.3 Vacuum system control scheme The vacuum system control scheme is as shown. The vacuum gauge outputs 4 to 20mA of current. After calculation by the PLC, the output signal controls the AC drive so that the AC motor powered by the mechanical pump maintains a stable rotation speed. At the same time, the AC drive has overcurrent and phase loss protection.
Vacuum System Control Solution 1.4 Hardware Configuration * The vacuum gauge uses a computerized ionization vacuum gauge (vacuum gauge).
Instrument matching sensor: Z-10 series vacuum ionization gauge. The instrument uses a single-chip microcomputer-specific control system to assist in vacuum measurement and control.
* The inverter uses ABB's ACS600 series inverter. It is a high performance frequency converter using direct torque control (DTC) technology combined with many advanced manufacturing processes. With a high power range, excellent speed control and torque control features, complete protection features and flexible programming capabilities.
Series PLCs are monolithic structures that are compact, compact, low cost, and easy to install.
1.5 PID algorithm of vacuum degree Because the vacuum degree in the vacuum chamber has strong non-linearity, time-varying and various kinds of interference, it is difficult for the traditional control method based on precise mathematical model to obtain satisfactory dynamic and static control effect, in order to make vacuum Degree of control is reliable and accurate, using incremental PID control method. For a typical PID control, its control type is Kp proportionality coefficient Ti integral time constant Td differential time constant e(1) Deviation of the given quantity and output quantity After the digital discrete processing of (1) formula, an incremental PID formula T-sampling can be obtained. Cycle e/current value 1 previous value The controlled object in the closed-loop control system is an electron beam furnace body, and the control quantity is the motor speed of the vacuum pumped mechanical pump, and the given amount is 31CT2Pa. The adjustment amount (unipolar signal) consists of The vacuum gauge detects and converts the current to 4~20mA and sends it to the PLC. The signal used to control the output frequency of the inverter to adjust the speed of the mechanical pump motor is sent by the PLC after the PID instruction is executed and the single-polarity signal is converted by D/A. . Siemens S-200224 with the PID instruction: PID TABLE, L00P very easy to complete the closed-loop control, adjust its output value to ensure that the error is zero, so that the system reaches a stable state.
2 configuration king in the vacuum system application configuration software. With Kingview, users can easily configure the 'monitoring system' that they need. When needed, the production site information is transmitted to the control room in real time. On-site operators and plant managers can optimize based on these real-time and historical data. Control on-site operations to increase productivity and product quality.
The modified electron beam furnace control system uses a typical two-stage control mode. The upper computer production management level, completes the control to the lower position machine and the production operation management, etc., is mainly for the operator; the lower position machine is the basic measurement and control level, completes the production scene data collection and the process control and so on, it faces the production process. The upper computer adopts Advantech IPC, Win2000 as the operating system, and Kingview as the tool to develop the monitoring system. The lower machine chooses Siemens S-200 series programmable controllers and intelligent control instruments, such as micro-ionization vacuum gauges, current transducers, and voltage transmitters. Considering the matching of field wiring distance and communication speed, configure an RS232/485 communication card and connect the serial port on the card directly to the PLC communication module to realize real-time monitoring of the production site. Configuration of the main screen during operation: page (1) eyebrows, pull single crystal shop, monitoring center, main menu four screens, as shown in JamdmeetroniePublis. (When the e-project is run on the KingView platform, the main screen t will be displayed until the user switches to other screens, such as historical trend curves, historical alarm windows, etc. When designing the monitoring software, the King's own database is configured. The 'vacuum level' variable is defined in the table. The basic attribute settings are shown in Table 1. The alarm events can be grouped into different alarm groups and the desired alarm group can be displayed in the specified alarm window.
The Kingview trend curve is used to reflect the variable name of the data variable over time. Name of the variable Type of variable Minimum original value Maximum raw value Connection device Device address Use frequency Data type Read-write property Vacuum degree Real Read-only potential curve. During the running of the screen program, the real-time trend curve of the vacuum degree is automatically scrolled over time to quickly reflect the new change in the vacuum degree, but cannot be scrolled with the time axis/rollback, and historical data of the vacuum degree cannot be consulted; the historical trend curve can be Complete the viewing of historical data, but it will not scroll automatically, but need to use the command language to help implement the review function.
Kingview's database is divided into real-time database and historical database.
The real-time database provides real-time monitoring data for the system. It cannot be accessed directly by users other than the programming language or the Kingview. However, it can be connected with back-end databases such as Access or SQL Server by means of the Kingview SQL Accessor. Access by accessing the back-end database. The DBMS used in this system is Access2000. One of the fields is set to vacuum, and the vacuum degree can be recorded in the table of database name/monitoring table. In addition, the system also designs two kinds of real-time and historical reports. The real-time production status of the reaction system can also be used for the statistics and analysis of the long-term production process, so that the management personnel can grasp and analyze the production situation in real time, and the report can be printed out when needed.
After the electron beam furnace starts to smelt, the 4-20mA DC current output by the vacuum gauge is sent to the analog expansion module EM231 of the PLC. The module is responsible for converting the current signal into a binary number and storing it in the register on the card. After reading the data from it, it is scaled, reduced to vacuum, and assigned to the defined variable. After the vacuum degree variable gets the data of the production site, functions such as alarm, real-time display, curve analysis, and report generation can be realized.
Kingview automatically monitors the variables that require alarms. When the value or value of the vacuum level changes abnormally, an alarm will be generated so that the operator can take necessary measures. When an alarm occurs, the alarm event is displayed in the alarm window. The display format is determined when the alarm window is defined. There are two types of alarm windows: real-time alarm windows and historical alarm windows. The real-time alarm window only displays the most recent alarm event. To view historical alarm events, you can only use the historical alarm window. In order to classify 3 conclusions Vacuum system stability has been greatly improved after the vacuum system has adopted a new control scheme. The electron beam furnace monitoring system has a beautiful interface, simple operation, complete functions, and strong monitoring of the vacuum degree, which provides valuable information for improving production quality and efficiency as well as accident analysis.
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