| The test of wood moisture content is one of the important technical measures of making good use of wood and saving wood; it is also an important process in the manufacturing of wood. The accuracy of the test has direct influence impact on the drying of wood; making appropriate and economic use of the limited forest resources is of great important meaning to both the development of the economy and the modern construction of our country.This focuses on the detection of the high moisture content of lumber production line panels; it conducts online detection through single plane capacitance sensors and sort the panels according to the moisture content in order to lay the foundation for grading the wood in terms of the moisture content. This is of great significance for the lumber and wood manufacturing enterprises to improving the production quality and productivity, to saving energy and reducing dry costs and to enhancing market competitivity.According to the dielectric constant characteristics and the demand for the lumber production line, this article determines the composition of online detection of the moisture of panels and sorting system, the detection mechanism of the moisture content of panels, the overall programs of the moisture content detection of panels focusing of single plane capacitance sensors and the sorting system.We designed the hardware structure of the system according to the features of the moisture detection and sorting process of panels. In according to the working process of the system, we chose the photoelectric sensors which test the location of panels, determined the core part single plane capacitance sensors in the detection of the moisture content detection of panels and we decided to use the S7-200CPU226type as the master control module of the system. In the meantime, according to the characteristics of the I/O interface of the PLC master control module, we chose the corresponding voltage frequency converter, high-speed counters and multiple-purpose protocol, etc. We also built the moisture content detection and sorting hardware system.We established the PLC controlling system according to the controlling demands and flowchart of the detection and sorting system of panels so that this system can satisfy the detection and sorting demands of production line panels. In the operation system, we adopts the MD204Lminitype touch screen and computers to perform man-machine communication and real-time monitoring of the detection process.After determining the experimental conditions, we detected the panel samples using the moisture content detection machine of panels and compared this result with that acquired by weighing method; we got the deviation between the detection system and the sorting system; according to the deviation, we correct the deviation of the detection system of single plane capacitance sensors in order to maintain the detection accuracy and stability so we can improve the reliability of the system.Through experimental analysis comparation, we realized the online detection and sorting of high moisture content panels whose moisture content is above fiber saturation point, which lowers the production cost of follow-up drying of the wood, improves the production efficiency, is good for saving energy in the production and improves the drying quality of wood and outturn percentage; this is of great significance practical values. |
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