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Medium-density fiberboard is made from primarily from pine, but a variety of other softwoods are used as well. Much of the MDF made today contains some recycled material, which is usually in the form of sawdust, reclaimed wood or wood pieces too small to use for anything else.
The logs are stripped of bark, usually off-site, and then passed through a chipper machine that chops the wood into small chips. The chips are then compacted and heated to soften them prior to defibration. Sawdust and recycled chips, if present, are added at this stage.
The chips are fed into a defibrating machine, which is a large tank that applies constant pressure and high heat to the chips. This process breaks down the wood into its most basic, and smallest, parts. The resultant product, which resembles very fine sawdust, is known as pulp. The defibration process is often referred to as pulping.
After exiting the defibration machine, the pulp passes onto a conveyor belt and is sprayed with wax and a glue, called resin. The wax makes the material more water-resistant. The resin binds the material uniformly. The pulp mixture continues down the conveyor belt where it is dried at temperatures reaching 550 degrees.
The pulp is then formed into a mat measuring from seven to 20 inches thick, depending on the desired final thickness. This happens in a machine called a pendistor. The dry pulp is placed in the top of the machine, which infuses air as the pulp passes through the machine and exits onto a conveyor belt at a consistent size. Upon exiting the machine, the MDF mat is cut into rough panel sizes.
After being rough cut, the MDF panels are fed into a press, where high heat, extreme pressure, and time all combine to compress the several-inches-thick panels into the final desired thickness, which typically ranges from 1/2 inch to 1 3/4 inches. After the panels are pressed, they are removed from the press and stacked to cool down.
The now cool MDF panels are cut to final finish sizes and then both faces are passed through a large sanding machine to finish the process. The completed panels are then packaged on pallets for distribution around the world.