Vacuum differential pressure casting is an advanced anti-gravity precision forming method. It combines the features of vacuum suction casting, low pressure casting, and pressure vessel casting. It adopts the filling process under vacuum conditions and the high-pressure crystallization technology with superior filling. The conditions of fluid mechanics and solidification mechanics have shown great vitality in the casting, aerospace, defense, and automotive industries, with little margin, large-scale, thin-walled, and complex non-ferrous alloy castings. The key to obtaining high-quality castings by vacuum differential pressure casting is the precise control of the entire process. Therefore, the use of advanced intelligent control systems is the guarantee of the entire process.
With the continuous development of computer technology and the emergence of new programming technologies, the current control systems have universally adopted a visual interface. With the help of various powerful object-oriented visual programming techniques, people can design beautiful, easy to use, and interface. Friendly control system. Delphi is an interactive visual integrated development environment developed by Inprise Corporation and running on the Windows platform. Delphi is highly scalable and suitable for rapid development, prototype product design, and higher production efficiency than C and assembly languages. In addition, database and network development capabilities are unmatched by other tools. In this paper, VCPC-1 vacuum differential pressure casting equipment developed by ourselves is used to develop an intelligent control system with visual interface in Delphi language to control the entire process, and achieve the short-range control of the lower computer and the remote control of the upper computer.
CPC-1 Vacuum Differential Pressure Casting Equipment and Technology PC-1 Vacuum Differential Pressure Casting Equipment VCPC-1 Vacuum Differential Pressure Casting Equipment includes a main part and an auxiliary part. The main part is mainly composed of upper and lower sealing tanks, intermediate partitions, lifting tubes and bases. Such as composition, under the sealed tank put holding furnace, on the sealed cans cast mold; subsidiary parts mainly include holding furnace, crucibles, safety valves, pressure gauges, pressure sensors, thermocouples, vacuum pumps, gas tanks and gas control parts. VCPC-1 vacuum differential pressure casting working principle see.
PC-1 vacuum differential pressure casting process VCPC-1 vacuum differential pressure casting process is divided into five stages: vacuum pumping, filling, boosting, pressure keeping and pressure relief. The process curves are shown in the figure.
Fund Project: Science and Technology Commission for Science, Technology and Industry for National Defense (BB200300088); Open Project of Jiangxi Materials Science and Engineering Center (ZX200301003).
Fuzzy control, but the digital PID control is dependent on the mathematical model of the controlled object because of its PID parameter determination and self-tuning, it is not suitable for controlling nonlinear, time-varying systems. Fuzzy control is a method that is very suitable for industrial production process and large system control. The more obscure the object is, the more the control method can reflect its superiority over other control methods. Therefore, the control scheme of VCPC-1 vacuum differential pressure antigravity casting intelligent control system adopts a parameter self-tuning fuzzy control system, that is, proportional factor self-tuning fuzzy control.
In the process of vacuum differential pressure casting, three process sections of filling, boosting, and holding pressure need to be precisely controlled, and a continuous and stable transition is required between each process section.
2 VCPC-1 Vacuum Differential Pressure Casting Visual Interface Intelligent Control System 2.1 Vacuum Differential Pressure Casting Control Model Vacuum Differential Pressure Die Casting Process Generalized Objects (including Electric Valve Positioner, Pneumatic Diaphragm Control Valve, Vacuum Differential Pressure Casting Machine, Pressure Sensor, etc.) The transfer function is: In the control system, the transfer function G(s) of the continuous domain of the controlled object must be converted into the transfer function G() of the discrete domain. It can be obtained by the method of the Constantine transformation: (2) Formula (1) obtains the discrete domain transfer function %() of the vacuum differential pressure casting control system, and designs a vacuum differential pressure die casting intelligent control system with a sampling time of 7 to 100 ms.
2.2 Schematic diagram of intelligent control system The control object of VCPC-1 vacuum differential pressure casting intelligent control system is the pressure of the upper and lower two sealed tanks. The schematic diagram of its control system is shown as follows.
At present, the control schemes of the control system mainly include digital PID control and proximity control of the 2.3 lower position. The proximity control of the lower position of the intelligent control system is controlled by a single-chip microcomputer. It is mainly composed of the main CPU, input channels, output channels, keyboard display and strings. Several major components such as communication are formed to complete the vacuum differential pressure casting process control. The main CPU includes the 89C52 microcontroller, serial E2PROM, RAM, EPROM, and decoding circuits. Analog input channels consist of input amplification and conversion circuits and A/D sampling chips.
The analog output channel adopts dual-channel 12-bit serial D/A chip for analog/digital conversion. The output voltage is converted into 4~20mA current through the op amp and voltage-current conversion circuit, and the electro-pneumatic valve positioner is adjusted. Then control the opening of the pneumatic diaphragm control valve, so that the tank pressure value changes.
The keyboard display part adopts 8279 programmable keyboard/display interface chip, and the keyboard, LED display and working status indicator on the panel are all controlled by it to achieve good man-machine conversation function. Proximity control mainly facilitates real-time monitoring of the entire process in the field. It has self-checking functions of various valves and alarms, which is conducive to human-machine dialogue. The lower machine proximity control flow chart is shown.
2.4 Remote control of the upper computer The remote control of the upper computer of the intelligent control system is controlled by a PC. The RS interface is as shown in the figure. The main thread is divided into three major functional modules: a process file management module, a view switching module and a command execution module. The process file management module completes the functions of opening, saving, and printing process files, and manages the documented process data. The saved suggestion file name will be assigned a string of the current working time in order to distinguish different sets of process data. The printing function in the file management module is used to automate Excel by using Delphi, and the current online process data is inserted into the Excel spreadsheet. The user can realize the function of printing the process data by simply operating Excel. The key problem in realizing this function lies in how to use Delphi to automatically start Excel, insert process data into Excel, and automatically create a spreadsheet. The process data is displayed in Excel in the form of a table. See the data display interface. The view switching module will process data. Displayed in three different ways, namely: simulation display mode, process data table display mode and process curve display mode. The command execution module mainly executes pull-down menu commands and tool menu commands. 3 After the production and application were successfully debugged and tested, the VCPC-1 vacuum differential pressure casting equipment with visual interface intelligent control was used to pilot small-volume production of small-volume, thin-walled and complex castings for an aviation company. The casting is the starting machine housing and the gear box housing military part of a certain type of national defense aircraft in our country. The casting molds are respectively made of fusion model, metal type and complex combination sand core. The casting is a cylindrical shell with a minimum wall thickness of 0.8 mm and a maximum wall thickness of more than 20 mm. The conventional casting method has a very high scrap rate. The system uses the indicated process parameters for small-scale trial production. The actual process curve obtained is shown in the actual production process curve shown in the application is smooth and smooth, and is consistent with the ideal process curve, indicating that the VCPC-1 vacuum difference of the visual interface intelligent control. Pressure casting equipment works well and the control system is reliable.
The castings have passed the quality inspection of military products, and through transmission and flaw detection analysis, the castings have no defects, high density, and the organization and performance completely meet the requirements of military products. This shows that the VCPC-1 vacuum differential pressure casting system with intelligent control has the minimum wall thickness of 1 mm or less. Nearly no capacity for thin-walled and complex castings.
4 Conclusion The visual interface of intelligent control, the main line program is divided into three major functional modules: process file management module, view switching module and command execution module. The interface pops up in the form of a window, achieving the short-range control of the lower computer and the upper computer. Remote control, has a good one-machine dialogue function.
Visual interface The VCPC-1 vacuum differential pressure casting equipment with intelligent control is running well and the control system is reliable. It has the capability of producing near-above-thickness and thin-walled complex castings below 1 mm.
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