MDF Process

MDF process

1, stock

The first step of MDF production process is material preparation. The equipment mainly includes chipper, belt conveyor, sifting machine, bucket elevator, storage bin, etc. In fiber board production raw material basically is woodiness fiber raw material, it includes path wood, twigs, firewood, processing remnant, ideal stock material raw material is needle leaf material 60% ~ 70%, broad leaf material 30% ~ 40%, bark content does not exceed 5%.

2. Prepare fibers

Fiber preparation is mainly fiber separation, which is the core of fiber plate production process. The equipment used for fiber separation includes wood chip bin (or preheating bin), small hopper, heat mill, paraffin melting and application device, sizing and measuring device.

Steps of fiber separation:

A: hot mill. The qualified wood chips are transported to the wood chips bin, and the wood chips are steamed, softened and transported to the mill chamber. After the thermal mill compression of wood chips, the moisture content of the higher wood extrusion out of water.

B: the wax. The paraffin wax is heated and melted by steam coil. The melted paraffin wax is driven into the wood chip before grinding chamber body through pump pipe. After being separated into fibers, the paraffin wax is evenly distributed on the fiber surface.

C: sizing. Urea-formaldehyde resin enters the double measuring tank through the filter and glue pump, and then enters the pump into the discharge pipe to size the fiber. The fiber in the discharge pipe is in the state of high-speed flow, and the glue liquid becomes atomized and evenly sprayed on the surface of the fiber. Curing agent and formaldehyde capture agent can be added to the rubber tank for stirring.

3, dry

The main equipment for drying process of fibreboard production consists of main drying machine, dry pipe, cyclone separator, fiber conveying device and dry fiber bin. The exhaust pipe of the hot mill inhales the wet fiber of the dry pipe and fully contacts with the hot air. The fiber is suspended in the air pipe and is transported by airflow. The fiber runs in the air pipe for 4 ~ 5 seconds to quickly evaporate the moisture of the fiber and reach the required moisture content (8% ~ 12%).

4, molding

Molding shop is very important in medium density fiberboard (MDF) production process a process, the process includes the slab pavement, preloading, together the main parts, such as edge, transverse to the requirement of surfacing process is: the slab uniformity and stability of density, thickness, weight per unit area of the slab control continuous stable and consistent, has a certain compactness.

5, hot pressing

At present, the hot pressing technology of medium density fiberboard in China is intermittent multi-layer hot pressing technology.

A: hot press temperature. The choice of hot press temperature mainly according to the type and performance of the board, the type of adhesive and the production efficiency of the press to determine. The selection of temperature mainly depends on raw materials, tree species, fiber moisture content, adhesive performance, slab thickness, heating time, pressure and equipment conditions comprehensive factors.

B: thermal pressure. Hot pressure in the process of hot pressure is changing, pressure gradually increased to meet the requirements of slab thickness, that is, the pressure should be reduced, and the solidification of the adhesive, the formation of various binding forces between the fibers, water evaporation is mainly completed in the low pressure section, the pressure of the low pressure section generally take 0.6 ~ 1.3Mpa.

C: hot pressing time. The determination of hot pressing time is mainly related to the properties and curing time of glue, fiber quality, moisture content of slab, thickness, temperature and pressure of hot pressing. Hot pressing time is generally expressed by the time required for 1mm plate thickness.

D: moisture content of slab. In the hot pressing process, the effect of the moisture inside the slab is to increase fiber plasticity and thermal conductivity, so the appropriate moisture content to guaranteed the quality of plate, general control in 10%, if too much will make tables, core layer density gradient increases, binding force difference between core layer fiber, step-down exhaust steam, the steam is difficult to eliminate, the intraplate bubbling, layered, if too low will make the soft panel, solidified layer thickness, the decrease of strength of plate.