This report summarises a research project carried out at Forintek Eastern Laboratory on Investigation of MDF Press Strategies to Reduce Press Time. The scope of the research includes theoretical analysis of MDF hot pressing process, development of a computer simulation model for MDF continuous hot press, parametric study of hot pressing process using the simulation model, and experimental works on microwave pre-heating of the fibre mat. As results of the research project, a comprehensive computer simulation model was developed. The following conclusions can be made based on the theoretical and experimental works of this project:
The computer simulation model is capable of analysing the hot pressing process and predicting the evolution of important pressing parameters including temperature responses, gas pressure, gas density, gas flow velocity, moisture content, load and stress, and density profile development in different location of the fibre mat. The predicted data agree well in trend with the observations from the industrial MDF continuous presses.
The parameters significantly affecting the hot pressing time include panel density, initial fibre moisture content, initial fibre mat temperature, pressing temperature and width of the fibre mat.
Other hot pressing parameters, such as the initial closing speed and the temperature difference among different pressing zones, have no significant effects on the hot pressing efficiency.
Microwave pre-heating of the MDF fibre mat, not only increase the initial mat temperature, but also re-distribute the moisture towards the mat surface.
Microwave pre-heating induces an earlier increase of the core temperature in the MDF fibre mat and a greater rate of temperature increase.
As a result of microwave pre-heating, the pressing time can be substantially reduced, leading to an increase in production efficiency.