Plywood is an engineered wood product that is manufactured by joining multiple thin layers of wood together with a strong adhesive to form a strong board.
Plywood comes in many variants or grades, depending on the wood species, number of plies, overall quality, etc. It is used in all kinds of commercial and domestic projects, ranging from building construction to furniture making, cabinetry, shelves, and more.
Plywoods are made from raw wood. If you’re looking to know more about the process of plywood manufacturing, this article is for you.
Plywood: Definition and Uses
Plywood is an engineered wood product created by binding thin “plies” of wood veneer together. To increase the strength and resilience of the plywood board, the wood layers are bonded with their grain running in opposite directions.
Depending on its strength and quality, plywood is frequently offered in a variety of grades. For a variety of uses, including the creation of panels, structures, partitions, doors, etc., furniture creation, cabinetry, and more, it is available in different thicknesses and sizes.
The tremendous strength and structural integrity of plywood make it valuable as an alternative to real wood. It is a strong wood alternative that does not shatter or distort easily. It is also pretty simple to shape and work with. Plywood of higher quality frequently resists moisture. Additionally, plywood typically costs less than most hardwood species.
Hardwood plywood, softwood plywood, and marine plywood are some of the major types of plywood, depending on the main component and intended application.
Furniture, fundamental home construction, roofing, subflooring, and sheathing are a few major applications for plywood. Because they can swiftly cover a big area, long sheets of plywood are oftentimes utilised for sheathing. Treated plywood is typically used to construct outdoor furniture and sturdy roofing because it resists decay and moisture. Plywood is an extremely versatile material with a wide range of applications, including furniture, cabinets, boxes, and regular woodworking projects.
Step-By-Step Plywood Manufacturing Process
Step 1: Selecting the Right Timber for Plywood
As we mentioned, plywood is made from wood. So, the first step in the plywood manufacturing process is the selection of the right wood and log.
A wide range of timber species is used to make plywood. These include softwoods like pine and fir and hardwoods are oak, maple, cherry, and poplar.
Hardwoods being stronger and more durable than softwoods are generally preferred for making plywood. However, softwood plywoods are generally cheaper.
When selecting a plywood log, the selector needs to consider a few things, such as the length and diameter of the log, its quality, the presence of knots, etc. Straight logs without a lot of knots are considered ideal for plywood manufacturing. The wider it is, the more layers can be obtained from it.
To keep logs saturated, many manufacturers prefer to store their logs in freshwater ponds or similar areas with access to water to avoid drying.
Step 2: Peeling
Peeling refers to the process of obtaining thin layers called plies from a wood log.
The logs are usually conditioned with hot water before subjecting them to a lathe for peeling. This helps smoothen the process and improves peel quality.
The log is fed to a lathe machine, where a sharp blade peels it to obtain continuous thin layers of veneer.
A veneer or ply refers to a thin layer of solid wood that is generally used for decorative purposes and to make plywood. High-quality wood veneers are often attached to lower-quality wood boards to improve their appearance and durability.
The lathe machine continuously rotates the wood log while the blade slices down a continuous thin layer of veneer, which is pressed and straightened immediately.
Step 3: Drying
Since the veneer produced in the previous step is generally wet or contains a lot of moisture, it needs to be dried first to achieve optimum moisture levels. This is done in a special chamber called a kiln, which uses steak or gas which is passed through the wood under specific pressure to force the water out.
Dried veneers are stronger, more stable, and less prone to breaking, which makes them perfect for plywood manufacturing.
Step 4: Laying Up
As you may know, plywood is made by joining multiple layers of veneer or plies using a strong adhesive. Plywood generally has an odd number of plies – 3, 5, 7, and so on.
So, the wood layers or plies are stacked onto each other such that the grain of adjacent plies is perpendicular. A strong, sometimes waterproof, bonding agent is used to join plies. A predetermined amount of pressure is applied on the sheets to ensure a strong bond. The end panel, called plywood, can be as strong or even stronger than solid wood.
The quality of plywood depends on a number of factors, including the type of wood and adhesives used to manufacture it.
When manufacturing plywood, the right amount of pressure under the right temperature conditions is crucial to achieve the desired results. During the pre-press, the glued layers are pressed for several minutes to flatten the veneers and allow the adhesive to get equally in all areas of the veneers. Then, the board is processed through high heat and pressure in a hot press, which causes the glue to melt and quickly and efficiently bond the veneers.
Step 5: Trimming, Sanding, and Grading Plywood
The plywood boards produced in the previous step are trimmed to remove irregularities and cut in the required shapes.
Panels are sanded and repaired as needed to ensure smooth surfaces and ends and made ready for grading.
Grading refers to the process of assigning a grade (rating) to plywood, primarily based on the quality, type and appearance of its front and back veneers. The stronger the front and back of a plywood, the more durable it is.
In the UK and other parts of Europe, the most common grades of plywood are as follows:
- AB Grade – highest quality with consistent colour and very few or no knots.
- B Grade – Natural-looking plywood. Variations in colour. A few knots.
- BR Veneer Grade– Similar to B grade. Smaller knots. Smooth finish.
- BB Grade – Similar to B grade. Bigger knots and repairs. Not very attractive. Mainly used in construction.
- C Grade – Strong plywood but not attractive. Likely has defects. Used in construction.
- CC Grade – One attractive face while another may have defects.
After grades are assigned, plywood boards are sorted and arranged for further processing (storage or transport).