If you’ve recently been shopping for furniture, the term “MDF” probably came up.
If you’re wondering how MDF is made, then this article is for you! Today, we’re explaining the stages of MDF production to help you better understand the process.
What Is MDF vs plywood?
From coffee tables and kitchen cabinets to closets and decorative trims, MDF is a versatile engineered wood that offers plenty of design and building solutions for woodworkers, DIYers, architects, and builders.
MDF is short for medium-density fiberboard. It’s a type of composite wood-based panel that was invented in the USA around the 1980s.
MDF is denser than plywood, with versatile applications in interior design, furniture production, and flooring.
Plywood is made out of different plies of wood veneer. This means that different sheets of wood are glued together.
MDF, on the other hand, is made by combining wood pulp. MDF is lighter to transport and can be cheaper than plywood. MDF is also more versatile and can be used in a lot of applications.
Plywood is often more durable and can be stronger than MDF.
Both plywood and MDF are lower in quality than items that are made out of one piece of wood.
How Is MDF Produced?
Now that you have a better idea of what MDF is, it’s time we talk about its manufacturing process. The following are the main stages of MDF production:
1. Fiber Preparation
First, tree logs are debarked using a rotor or drum debarker. The goal is to separate the bark layer from the logs.
In a rotor debarker, the log spins with its longitudinal axis at the center. The rotation across the rotors removes the bark from the log. This type of debarker is used when you’re trying to peel off as much bark as possible.
In a drum debarker, the drum compartment carries multiple logs and rotates to promote the scraping of logs against the drum’s surface and each other, effectively peeling off the bark. The more time the logs spend inside the drum, the more bark is removed.
Whether a rotor or drum debarker is used, the resulting bark is discarded or used in landscaping or energy production because it’s unsuitable for manufacturing wood-based panels. The logs move on to the next stage.
To make fiberboards, we need wood fibers. This is where chipping comes in, which is done using disc chippers or drum chippers.
The raw wood material is moistened (to produce a more uniform chip size) and then transferred into the chippers for cutting via blades.
If some chips are too big, they can be processed through the chipper again. If some chips are too small, they can be used as a source of energy.
After that, a metal detector is used to screen out any metal particles that are often present in chips.
This step aims to clean the wood ships from impurities such as sand, gravel, and stones. This helps extend the lifespan of the production equipment and minimizes the silicate content for better processing.
Defibration means preparing fibers out of wood chips. This is a crucial step in manufacturing MDF because high-quality panels require high-quality fibers.
Two factors affect the grade of the produced fibers: wood type and chips’ properties.
To produce fibers, the chips are boiled and then processed through a refiner. Single-disc refiners are the staple for manufacturing wood fiberboard.
Producing fibers from wood chips is a costly process as the refiners are expensive and demand constant servicing.
2. Shaping and Pressing
Right after exiting the refiner, glue is applied to the produced fibers in a calculated amount depending on the weight of the wood chips. Some additives can be incorporated into the glue to support moisture or fire resistance.
However, gluing has to be coupled with drying to remove residual moisture caused by boiling in the previous stage. This is done in one of two ways:
- In-mixer gluing — before adding the adhesive to the fibers in the mixer, they’re first transferred through a flow tube dryer.
- BlowLine — after adding the adhesive to the moist fibers, the glued fibers are dried in a flow tube dryer.
Creating the Panel: Adding Strenght
To form a panel, the glued fibers are evenly distributed across a conveyor belt that’s continuously moving. Unlike OSB boards and particleboard, the fibers in MDF production don’t require alignment in a specific direction.
Before entering the press, the glued fibers on the conveyor belt are sprayed with a variety of liquids to induce a range of improvements such as:
- Reducing flammability
- Reducing pressing time
- Increasing fungi resistance
Also, some glue types can stick to the surface of the press upon compression. To solve this issue, releasing agents are applied to the surface of the press.
Right before entering the press, the weight per unit area of the glued and sprayed fibers is measured to check the density profile of the raw material. This way, fluctuations can be picked up and impurities can be screened for discarding.
Next, comes the pressing process which consists of two stages: pre-pressing (deaeration) and pressing. This is to improve the quality of the produced panel.
In some cases, the panel is also preheated to further enhance the quality of the panels.
Inside the press, the fibers are compressed into a board of uniform thickness. The glue solidifies due to the exerted pressure and temperature, which also cause the plasticization of wood particles so they’re permanently deformed.
After the boards leave the press, their quality is checked in various parameters such as moisture, thickness, and density.
Trimming and Cooling
Next, the edges of the produced panels are trimmed since they come out of the press all rough and jagged. Trimming results in clean borders with defined proportions.
After that, cooling of the produced boards is done to bring their temperature down to room/storage temperature as they leave the press very hot. This step is important to enable the stacking of the panels.
Sanding and Sizing
The boards then enter a sanding line where their top and bottom surfaces are sanded to become smooth and achieve the desired thickness more precisely.
Finally, the panels enter sawing lines to be cut into the appropriate retail sizes.
There you have it, a simple yet comprehensive guide to how MDF is made. It’s important to be familiar with the production process of this popular building material since it’s present in practically every home across the world!