A product story: plywood

12/08/2018

Chronology

Plywood is made using thin sheets of wood between 0.8 and 4mm in thickness, obtained by peeing or slicing. These so-called plies are then bonded under pressure. In France, the most commonly used species are beech, maritime pine, mahogany and poplar. These species create a stronger, more flexible material than solid wood.
The plywood technique dates back to ancient times, but it was not until 1850 that plywood began to be used on an industrial scale. 

There are several stages to plywood manufacturing: 

1) The heating and soaking process is essential for hardwoods. Logs are then steamed (60 to 85°C). This process facilitates peeling, improving the surface quality of the veneer. Dividing into sections, after debarking the logs, makes it possible to cut the blocks to size.

2) Peeling consists of rotating the blocks on two parallel two pins, steadily progressing towards a knife blade, which peels a continuous ribbon from the block between 1 and 3m in width. The guillotine cuts the peeled wooden strip to the required dimensions. Depending on the production line, guillotining can be carried out before or after drying.

3) Drying helps eliminate the water contained during veneering. Sheets pass through a ventilated machine and are heated to between 160 and 205°C.

4) Bonding consists of coating the veneer sheets with adhesive.

5) Pressing is a process that ensures the physical and chemical bonding of the plies by hot polymerisation (under pressure) of the adhesive in the presses.

6) Sanding calibrates the panels by passing them between two cylinders equipped with abrasive belts.

Bonding Quality

The adhesives we use are thermosetting resins. The quality of the plywood when in contact with moisture depends on both the performance levels of the bonding, the species and the conditions of implementation. The adhesives we use comply with current formaldehyde level standards (our adhesive is classified E1). This classification means our panels can be used indoors without any risk of any exposure to formaldehyde.

Moulded Plywood

This is made up of crossed plies which are bonded in a press comprising a mould and counter-mould corresponding to the desired shape : 
  • two dimensions (2D): half-moon, U-shape or L-shape
  • three dimensions (3D): rounded shape, seat shell, special shapes
For each particular shape, it is necessary to manufacture a specific mould and counter-mould. This moulding technique has limitations as it must be possible to create the shapes from veneer sheets without breakage during pressing.

Plywood is a multifunctional material par excellence.




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