Study On Intelligent Controlled System Of Hot-pressing For Medium-density Fiberboard's Production

Medium-density Fiberboard's production involves the processes of materials preparing, textile fiber separation, drying, gluing, waxing, forming, hot-pressing, side-cutting, there among, hot-pressing is one of the most crucial processes in the production and its parameters closely interrelate with the quality of medium-density fiberboard. Accurately controlling the course of the processes parameters and intelligent regulating, the hot-pressing procession according to the principal parameters in current cycle can be qualified to produce the final product, which is also an important economic measurement to improve product quality and increase productivity. Depended on the in-depth study of internal mechanism for semi-finished fiberboard forming in hot-pressing processes, and oriented by algorithm and intelligent cybernetics, this paper studies the Distributed Intellectual Controlled System based on fieldbus composed by Programmable Controller while the system improves the production efficiency and product quality through the processes respectively controlling and centralized monitoring. Main results and conclusions are as follows:1. The paper chiefly discusses the transfer mechanism of the interior heat and humidity, the physical behavior of the mat and mechanism of the transferring course during hot-pressing, and the density distribution and transformation of fiberboard along the thickness direction. Based on the researching achievements before and theoretical analysis, Guided by the theory and experimental data from producing line, the mathematic models are established for heat transfer and temperature distribution inside the board, for the humidity transfer and humidity content distribution of the board, for the physical behavior transformation and relationship between stress and of the stressed board, and for the formation of VDP of fiberboard.Through these models, the way to accurately calculate hot-pressing time was proposed, and the density distribution of the product can also be forecasted, which providing theoretical basis for the hot-pressing's design and further control.2. Distributed Intellectual Controlled System of fuzzy PID regulation was designed and adopted in the process of medium-density fiberboard hot-pressing for the first time, which realized the fuzzy PID regulation for hot-pressure, provided the PID adjusting parameters according to the vague rules, and achieved the optimized controlling for hot-pressing associated with PLC. Another preliminary attempt, closed-loop process control which based on the density of fiberboard, becomes the breakthrough for substituting the former technique's curves experienced-oriented processing circuit.3. Advanced ultrasonic test technology was preliminary tentatively used to accomplish the real-time testing for different layers of MDF. Based on PROFIBUS technology, a distributed intelligent control system was established to achieve a production process of Medium-density Fiberboard which provides discretization, network and intelligence of producing line for MDF in the term of producing line control. PLC was served as the control core in site-monitored level and used to real-timely adjust every process and controlling parameters of the production process, according to the intelligent control algorithm. The hardware was configurated for PLC and hot-pressing control program is developed according to the input and output counts. Human-machine interactive monitoring interface was programmed based on host computer utilized WINCC configuration software to show the real-time technical situation of each section and achieving the setup and display of the technology curve.