Moulded plywood - manufacturing techniques, properties, uses

I can't think of anyone who hasn't seen chairs, armchairs, armchairs, poles or other pieces of furniture that, although they have different shapes, have a continuous wood design all over. You've probably wondered if it isn't just a design printed on paper, as it is laminate flooringwhich has no trace of wood in it. But this time we're talking about wood. It's molded plywood, which can be used to create furniture with interesting designs. Chairs made of molded plywood are light and comfortable, elastic but very strong. The emergence of molded plywood was a turning point not only in the furniture industry. It is an interesting and attractive material, both for large furniture manufacturers and for passionate carpenters and designers.

What is moulded plywood

I've talked about plywood before when I did a brief history or when we talked about wood-based panels. In short, plywood is a material that has long been used to make furniture, and there are pieces of furniture in museums with plywood parts dating from the late 1700s - early 1800s. Plywood is a wood derivative that is made by overlapping and gluing veneers. The resulting material is more stable and durable, with a generous surface area that can be worked like solid wood.

The furnaces can be laid perpendicular to each other or parallel along the fiber. In the first case the number of veneer sheets must be odd in order to balance the tensions. The resulting material is rigid, stable and lightweight. In the second type the number of veneer sheets is only important in terms of the thickness of the resulting plywood. It is also called laminated plywood and is very elastic and strong. If, after applying the adhesive and overlapping the veneers along the fibers, drying is carried out in a mold under pressure, the result is moulded plywood.

Short history

The first attempts to make molded plywood were made as early as 1830 by Michael Thonet. But he abandoned this direction and concentrated on curving solid wood. This is how - from curved beech - Thonet chairthe best-selling piece of furniture of all time.

In the 19th century there had been various attempts - in Europe, the USA and Canada - to produce molded plywood, but without any impact on the industry. In the late 1920s designers and architects discovered the versatility of plywood and increasingly worked with it. The turning point for molded plywood's entry into industrial furniture manufacturing was 1933. That was when mass production of the chair began Paimio (more of an armchair), created in 1932 by Finnish architect Alvar Aalto for the sanatorium in the town of Paimio. The chair was soon exported to England, Germany and even the USA.

Another important moment in the evolution of molded plywood was the Second World War. That's when it was manufactured Mosquito plane with a molded plywood fuselage, the lightest and fastest fighter at the time and the one that flew at the highest altitude. During the war the airplane was manufactured in England, Canada and Australia.

Other milestones in the history of molded plywood furniture were the creation of the chair in 1952 Ant by Danish architect Arne Jacobsen and the collection of pieces of furniture realized in 1956 by Ray and Charles Eames for American manufacturer Herman Miller. These were the moments that triggered a wave of molded plywood furniture production worldwide. Waiting rooms, canteens, canteens, restaurants, movie theaters began to use them extensively, and molded plywood furniture became commonplace. But that's not to say there aren't still spectacular and unique designer pieces.

What it takes to get a molded plywood

Enough history, let's get back to technique.🙂 To make molded plywood you need :

• veneer sheet
• adhesive
• mold, template
• Press

Furnace used for plywood is between 0.5 and 3-5 mm thick. Veneers below 1 mm are called fAesthetic Urn and are used for plywood faces. They can be different in essence from the others so you can get plywood from lime or plop with the faces of nuc or cherry. The plywood will be light and very nicely designed. The thicker sheets are called technical furnishing.

Allocation adhesive must be correlated with the working technology. Certain types of adhesive are used for cold bonding (PVA), for hot processing, other types (ureoformaldehydic, resorcinic, phenolformaldehydic). Hot process may also have emissions of free formaldehyde.

The matrix is what will give the final shape to the molded plywood. Usually, when heat curing, the mold is part of the Press. It is of the mother-father type, i.e. there is a mold on which the veneer packet is placed and over which comes the "negative" of the original mold which presses and heats at the same time. It is also possible to obtain the patterns in vacuum presses, in this case we do not need a "negative" of the mold. Regardless of how you attach it to the die, you can get 2D or 3D models, depending on how elaborate the die is.

Modeling can also be done with a template made of various materials, including molded plywood. The veneers on which glue has been applied are modeled after this template and clamped with clamps to create the pressure needed for a proper bond. You must work quickly to clamp them to the template before the adhesive begins to dry. It is a good idea to check beforehand how the clamping will be done using the veneer pack without adhesive applied.

Manufacturing techniques

How the molded plywood is made depends on whether the adhesive cures cold or hot.

Getting by cold press is used to make one-offs or for designer or DIY projects. As mentioned above, templates cut from plywood or plastics are usually used. A flexible steel strip or sheet is placed between the stencil and the bundle of veneer sheets to be pressed. During clamping, excess glue will come out and the plywood may stick to the template unless there is a non-stick bar. It is good practice to apply excess adhesive to be sure that the veneers stick all the way through. Many clamps should be used, clamped often, so that the pressure is as even as possible (this is why clamps are never enough 🙂).

The advantage is greater flexibility. The disadvantage is the long pressing time, sometimes taking up to 24 hours for the plywood to take the desired shape.

Press hot can be made in presses with normal heating or in CIF presses, i.e. using high-frequency currents. The advantage of the second method is the very short working time, requiring only 1.5-2 minutes for the plywood to come out of the press ready molded. Hot pressing is mainly used in industry where short curing time and identical reproduction of the pattern is needed.

CIF hardening is widely used worldwide and because heat is spread evenly within the adhesive layer. The resulting plywood is more homogeneous with even properties across the surface. The high frequency currents are supplied by a generator that is attached to the press. The generator can also work with 2 or more presses.

Properties, processing

After fabrication, molded plywood can be processed like any other type of plywood or wood derivative. Immediately after pressing, the edges are trimmed to remove hardened glue leaks or loose parts. This results in clean edges where the wood and adhesive layers are visible. Sometimes the differently colored adhesive layer (brown tones) gives a very nice and interesting look.

The molded plywood can then be cut into narrower elements that will represent the legs or arms of chairs and armchairs, or machined on various traditional woodworking machines or on CNCs.

The connection between the molded elements can be made with dowels, nails, screws or by gluing. Fastening to metal scaffolding can be done with screws. In spite of its elasticity, plywood is a tough and resistant material that can be processed without problems.

The final quality of the plywood depends on the quality of the veneers used. Veneers without defects, fiber tears or breaks will result in very high quality plywood. After processing and jointing, the molded plywood object can be sanded and finished in the same way as veneered furniture.

I hope you find the information interesting. If you think it would be useful to others, please feel free to share. If you have any additions, questions or comments, please leave them below in the space provided.