Products bent plywood furniture
Technology
Bent or curved plywood components in Northern Europe most commonly are made from birch veneer in middle layers and any other wood veneer or laminate in surface layers. Large-scale veneer usually 1.5 mm thick is cut according to product block dimensions. Highest quality veneer that looks clean, free of knots and mineral streaks and no significant differences in color are used for surface veneer.
Presstool or mould in necessary shape is made for pressing bent plywood components. Commonly used are electric heating or high frequency moulds, which operates like a microwave oven with an induction heating method. There are also steam heated moulds.
Presstool consists of two parts: the upper called puanson and bottom part called matrix. Pressed together bent plywood gets the required shape. Most molds are made from upright oriented milled straight plywood that is fixed together with screws. Then plywood shape is coated with a heat-resistant material. Into this insulation material is incorporated heating elements that are covered with 4 to 6 mm thick aluminum plates. Aluminum plate acts as the heating surface and it is formed into desired product shape. Mould is installed in the press, which performs the compression function.
Veneer layers are coated with adhesive with mechanic glue rolls and then stacked according veneer set developed by technologist. Then veneer pack is inserted into the mould to the corresponding marks. Heating and veneer surfaces are cleaned with air pressure pistol to avoid any dirt. The presstool is closing slowly to be able to control the process. Pressing time for instance for 10 mm thick block is about 5 - 6 minutes depending on the glue. Temperature in the mould is from 90 to 110 ° C depending on the surface of tree species or material.
After removal of the block from presstool it is left for 24 hours drying and curing. During this time blocks tend to change the bending radius. The block is opening or closing. These trends are taken into account when producing the mold. After drying the block is sawn, milled, drilled the according to technical card made from the technical drawing. Milling can be done either with a band-saw and plunge routers or 5 axes that is 3 dimensional cutting CNC machine (Computer Numeric Control machine). Components are then sanded and varnished or painted, stained according to the order.
Application
Glued bent parts are widely used especially in furniture manufacture of chairs and cabinets, shelves, wall panels of the various interior elements or skateboard ramp production. Advantage of bent plywood furniture is that it is more resistant and therefore can be made lighter constructions than solid wood or metal furniture and it is natural wood. Production of plywood is more material efficient than constructions of massive wood because in plywood all of the wood is used, in invisible inner plies lower quality veneer and high quality veneer or laminate on surface. Because of plywood construction strength certain wood furniture can be made only from plywood not massive wood.