Design Of Slab Internal Environment Detection System For Wood-based Panels Hot Pressing

As the rapid growth of demand of wood-based composite panels world widely, the quality requirements in every application fields of the products are also increasing. In the panel manufacturing, hot-pressing is one of the most important processes which are highly related to the panel quality. Local internal-mat conditions of temperature, moisture content, stress history, and gas pressure influence on wood densification, adhesive cure, and the subsequent panel properties. With this information, researchers and engineers in wood-based panel industry can optimize hot-pressing parameters and improve the production efficiency as a result. How to measure the local gas pressure and temperature, on a real-time basis, during board manufacture is the key of the problem. Therefore, a technique for internal-mat environment measuring need to be established. This research is based on the question mentioned above. After literature review about effects of variables in wood-based panel hot-pressing on panel properties, this research is mainly focused on developing a system to measure local gas pressure and temperature of the mat. Requirement of hot-pressing and internal-mat environment during the pressing process were analyzed. Thermal couple was used as a sensor to measure local temperature and the transducer diaphragm was use as a sensor to measure local gas pressure. By comparing assembling methods of various modern measuring system, virtual technique and the automatic measurement system based on VI with PC—DAQ(Data Acquisition) were used in the designing of real-time internal-mat environment measuring system during hot-pressing. PC—DAQ system consists of sensors, signal conditioning, data acquisition card, computer and software. Working principle and function of every part in the system were introduced in this paper. The development of testing hardware and software design of the system was detailed as well. Finally, the feasibility and applicability of the designed system was verified by practical particleboard hot-pressing experiment. The development of the Automatic measurement system for monitoring the internal-mat environment was based on LabVIEW program which is a powerful virtual instrument design workbench. Developed system in this paper can provide a friendly interface, an animated process-monitoring window including a real-time data acquisition of 2 pressure signal channels and 4 temperature signal channels, as well as the asynchronous serial communication between measuring computer and the data acquisition. Practical application testing and data analysis showed that this measuring system was useful and easy to operate by providing accurate and reliable data. Further more, since PC-DAQ virtual instrument design mode and graphic program language was adopted; this system was endowed with good versatility, flexibility and expandability. The interface between LabVIEW language and exterior code was also discussed in this paper. The interlink between local-made data acquisition card and labVIEW program was realized which can reduce the system cost and shorten the developing cycle of the product. The designed system in this paper is provided a flexible and efficient useful tool for real-time measuring the internal-mat environment during wood-based panel hot-pressing. It also could be a good mode for research and development of testing instrument in wood-based panel industry.