How Is Plywood Made? Step By Step Ply Manufacturing Process

Plywood is made by peeling logs into thin sheets of wood called veneers, drying them, coating them with resin and stacking them with the grain of each layer at right angles to the next. The stack is then hot-pressed into one solid board, trimmed to size, sanded and inspected before it leaves the factory.

The Plywood Manufacturing Process at a Glance

There are about a dozen steps between a log and a finished sheet, and each one affects how strong, flat and water-resistant the plywood will be. This table sums them up; the sections below explain them.

Step by Step: How Plywood Is Made

The process falls into five stages: preparing the logs, making the veneers, gluing and laying up, pressing, and finishing.

Preparing the logs

Logs are selected for size, quality and moisture content, then debarked. In north India, plantation timbers such as poplar and eucalyptus are widely used for core veneers, and hardwoods such as gurjan are common for face veneers. The debarked logs are then conditioned: soaked in hot water or steamed so the wood softens and peels without cracking. How long and how hot depends on the species and how wet the wood is.

Making the veneers

A rotary lathe spins each log against a long blade and peels off a continuous ribbon of veneer, much like unrolling paper from a roll. Veneer thickness varies with the product, but is typically around 1–3 mm. The ribbon is clipped into sheets and dried in a hot-air dryer to about 6–10% moisture content. Veneers that are too wet warp and do not bond properly in the press.

Dry veneers are then sorted and graded. Veneers with the fewest defects become the face veneers that you see; the rest go into the core. Splits and gaps in core veneers are patched or filled at this stage, because a gap left in the core becomes a hollow spot in the finished sheet.

Gluing and laying up

Resin is spread evenly over the veneers, usually by passing them through glue-spreading rollers. The resin decides how the finished plywood copes with water:

• Urea-formaldehyde (UF) resin is typical for MR (moisture resistant) plywood for dry interiors.
• Phenol-formaldehyde (PF or phenolic) resin is used for BWP (boiling waterproof) and marine plywood, because its bond holds even in boiling water.

Many manufacturers also add a chemical treatment to the glue line to protect the board against borers and termites.

The glued veneers are then laid up with the grain of each layer at right angles to the one below. This cross-grain construction is what makes plywood strong in both directions and less likely to split, shrink or warp than solid wood. Plies are laid in odd numbers so the two faces run the same way and the sheet stays balanced. Thin sheets may have only three plies, while 18–19 mm boards have many more.

Pressing

The stack is first pressed cold (pre-pressing) so the layers hold together and can be checked and handled. It then goes into a hot press, where heat and pressure cure the resin, squeeze out air pockets and bring the sheet to an even thickness. Press temperatures are roughly 120–150 °C, depending on the resin. Sheets are then left to cool and settle before they are cut.

Trimming, sanding and inspection

Cooled sheets are trimmed square to the finished size, such as 8 × 4 ft (2440 × 1220 mm), and sanded smooth. Each batch is inspected for voids, splits, overlaps and delamination, and sheets are marked with their grade and the manufacturer's name before dispatch. Most plywood leaves the factory plain and is finished on site with laminate, veneer, polish or paint; decorative plywood has a decorative face veneer pressed on at the factory.

What Changes Between Grades

The steps are the same for every grade; what changes is mainly the glue and the quality of the veneers. MR plywood is usually bonded with UF resin and suits dry interiors. BWP plywood uses phenolic resin, which is why it is the grade for kitchen sink units, bathroom vanities and exteriors; our guide to BWP plywood explains where it is worth using. Marine plywood (IS 710) uses the same kind of waterproof glue as BWP, with higher-grade veneers and tighter tolerances; see our marine plywood guide.

Some manufacturing faults show up at the edges of a sheet, such as gaps between core veneers, overlapping layers or layers coming apart. Our guide on how to check plywood quality explains what to look for before you buy.

How MRS Woodcraft Makes Its Plywood

MRS Woodcraft makes its plywood at its factory in Jhajjar, Haryana, following the same basic process with a few specific steps:

• Veneers are mechanically dried and stress-relieved before lay-up.
• Layers are laid in cross-grain construction for a balanced, dimensionally stable sheet.
• Veneers are bonded with fortified synthetic resins and hot-pressed at over 16 kg/cm².
• Smart Core Interconnect Technology (SCIT) is used to keep the core gap-free.
• The glue line is chemically treated against borers.
• Every batch is inspected before dispatch.

Sheets come in thicknesses from 4 mm to 25 mm, in 8 × 4, 7 × 4 and 7 × 3 ft sizes, with custom sizes on request. You can see the grades we make and ask for a quote on our plywood page.