Vertical high temperature vacuum sintering furnace control system
With the continuous development of science and technology, industry, national defense, aerospace and other fields in China have made great progress, the vacuum equipment manufacturing equipment level, production process, control technology also has the very big enhancement. Prompted materials along with the continuous improvement of science and technology in the field of development, in the aviation, aerospace, military industry, energy and chemical industry in areas such as some special material, the new material has been widely used. The vacuum heat treatment technology plays an increasingly important role in the production and manufacture of these special materials and new materials. Described in this paper, vertical high temperature vacuum sintering furnace is mainly suitable for cemented carbide, ceramics, magnetic materials, porous materials of vacuum sintering, can meet all kinds of high temperature oxidation resistant coating the surface of the parts sintering requirements, is developed for a domestic space military enterprise space equipment specialized equipment, mainly by the vacuum system, furnace, bottom sliding on the oven door and locking mechanism, closed water system, heating power systems and electrical automatic control system, etc. It is characterized by high vacuum degree, economical and compact. The furnace body USES double-layer water-cooled sleeve, vertical structure, heat screen, pressure gauge, thermocouple, cable, workpiece support and so on. The water-cooled electrode ensures the reliability of the electrode seal. The heater is directly connected to the electrode. Bottom oven door adopt four screw and the lifting of the gearbox, and through the elastic device is fixed on the roller type oven door and whole landing to the ground after use translation before and after the implementation of the gearbox, convenient unloading workpieces; The heating of furnace body is supplied by closed-loop stepless voltage regulating power supply, which is divided into three large districts and five districts for control, which is conducive to the adjustment of the furnace body's temperature uniformity. The whole system adopts self - circulation closed water cooling method.
1. Design of system control scheme
1.1 the operating process of the system loads the workpiece into the bottom furnace door car, which is properly fixed by tooling. Start bottom furnace door car to shift to the bottom of the shaft furnace body, bottom furnace door car automatically stop positioning. Start the bottom furnace door car lifting, the bottom furnace door flange is attached to the bottom flange of the shaft furnace body, start the furnace door gear ring locking system, and circle the teeth to the lock position. Start the furnace vacuum system. When the vacuum degree of furnace reaches the requirements of heating process, start the heating system and heat the furnace body to the working temperature according to the set thermal process curve. After the process curve is completed, the furnace body stops heating and the workpiece is cooled naturally with the furnace. When the temperature of the furnace body temperature down to rated blow-in, open furnace surprises valve to rise to the local atmospheric pressure, the furnace pressure start furnace incisors ring lock system, tooth outline to rotate to loosen the position. Start the bottom furnace door car lifting and moving system, the workpiece exits the furnace body to the given position outside the furnace, the sintering process ends. It is required to realize the real-time measurement and control of air pressure, water pressure, water temperature and water flow in the whole process. The process of vacuum degree on-line monitoring and interlocking control, such as roots pump, high level before the valve, drainage valve, vacuum valve automatically start vacuum, heating process curve, suspend, and reset operation vacuum control points, a variety of pump valve interlocking between; On-line monitoring of temperature control, temperature detection and workpiece temperature in all temperature zones, failure detection and alarm of heating power in all temperature zones and over-temperature control; Accurate positioning of the workpiece vehicle's incoming and outgoing materials, the lifting of furnace door and the rotation of gear ring, etc. In view of the complex operation process and large control scale of the system, it is difficult to operate manually. Therefore, the system must be controlled automatically.
1.2 design of control scheme. This system is large in scale and has a large amount of controlled quantity. It has both input and output of various switch quantities and real-time monitoring and control of analog quantities, and requires high control precision. Therefore, it is difficult to control the above controlled quantity with a controller. Based on different system structure of computer control system, such as direct digital control (DDC), computer supervisory control system (SCC), distributed control system (DCS), fieldbus control system (FCS) (PCS) and programmable controller system, this scheme control system USES a similar to the hierarchy structure of DCS for different charged with multiple controller to achieve. The controller includes industrial control computer, programmable logic controller (PLC), high precision intelligent temperature controller, import vacuum meter, wide width long graph printing recorder. These controllers form a small distributed, modular control system (DCS). PLC is dedicated to all kinds of switch quantity control, the system USES a set of PLC (OMRON CQM1H) measurement and control of vacuum sintering furnace switch input and output, the CQM1H programmable controller and related electrical components, finished products such as vacuum gauge, pressure controller motion mechanism, vacuum system, surprises such as part of the electrical control. Manual/automatic control. The furnace vacuum meter adopts a CM51 three-way digital display vacuum meter of Leybold company of Germany, which can measure the vacuum degree of the furnace and system pipeline. Furnace temperature control part adopts the United States Honeywell signal type system requires actual configuration allowance for measurement and control technical indicators to open (close D volume I) input to the dry contact 72 80 8 real measurement without open shut (D O) dry contact output of 68 80 12 with the point control means no analog control index (AI) B I 3 3 has no real control 600 ℃ + 1 ~ 1 ℃ 800 ℃ found accidentally telemetry warning degrees 6 6 B when no real measuring 600 ℃ + 5 ~ 1 ℃ 800 ℃ B artifacts dividing accidentally 9 12 3 real measuring 3 ~ 1 ℃ 800 ℃ to 600 ℃ + workers accidentally furnace degrees C unit 1 When there is no real measuring 1 to 0 ℃ + ~ 11080 ℃ 0 ℃ 0 ~ 1's empty when there is no real monitoring 0 v degree 3 3 (110-045-41 Pa analog 4 ~ 20 (AO) temperature control system of m A 5 5 have no real control stepless adjusting DCP551 and UDC3500 closed-loop control of the intelligent temperature control, PID self-tuning and adaptive function, and can be set and store up to 20 (99) each process curve. Also equipped with 3 sets of the United States Honeywell UDC2500 as overtemperature control, equipped with 1 American Honeywell DPR - 250 wide and long figure print recorder is responsible for the record the working process of the vacuum degree, temperature control, monitoring and workpiece temperature. The printing width of the recorder is 250mm, and the temperature recording range is adjustable.
2. Software function design
2.1 programmable controller program design PLC(OMRON CQM1H) software adopts the CX - Programmer development software provided by OMRON company, supports operating systems such as WIN98, WIN2000/XP, and has a flexible and easy-to-use programming development environment. The control quantity of the whole system is large, and the variables are interlocked with each other. In order to meet the control requirements more accurately, the program is modular. Several subroutines are written to simplify the program structure and shorten the scanning cycle. The main program includes the real-time control of the switch volume. The sub-programs are: workpiece car program, furnace door lifting subroutine program, heating subroutine program, backfill void subroutine, etc. The control program can be programmed according to the requirements of equipment and technology, with perfect interlock protection function, intuitive and eye-catching alarm method, high degree of automation, flexible and convenient operation.
2.2 man-machine interface program to design the system of monitoring configuration interface is provided in the accused by Beijing of KINGVIEW KINGVIEW 6.53 software for secondary development, according to the needs of system requirements and actual conditions, altogether creates the eight interface, including: the home page, working condition of system, alarm system, temperature control interface, report forms and curve setting, real time curve, history curve, etc. And the interface between the switching between simple, fast. The control dual temperature and workpiece dual temperature are displayed in the form of histogram, and color is used to distinguish them. See figure 3. The temperature setting curve, control dual temperature curve and workpiece dual temperature curve are tracked and displayed in the form of dynamic curve. The setting parameters of the process curve can be displayed in the form of table, and the unexecuted program segment can be modified online, and the vacuum degree in the furnace can be displayed in real time. During the execution of thermal curve, it has the function of pause and online modification. 20 pieces of pre-storage, each 99 pieces of process setting (section number, parameters, time, starting temperature, target temperature, temperature difference of workpiece, vacuum degree, batch, operator, program period event). Automatically generate process data report, friendly and convenient operation interface.