Plywood & LVL – The Manufacturing Process

1.1 Introduction

Structural plywood and structural Laminated Veneer Lumber are engineered, timber veneer products,

made by bonding thin timber veneers together under heat and pressure.

1.2 Manufacturing Standards

Structural plywood is manufactured to the Australian / New Zealand Standard AS/NZS 2269 Plywood –

Structural. Structural Laminated Veneer Lumber is manufactured in accordance with the requirements of

AS/NZS 4357 Structural Laminated Veneer Lumber.

1.3 Process Control

Structural plywood and LVL products certified by the

EWPAA are branded with

the EWPAA product

certification stamp as well as the JAS-ANZ (Joint

Accreditation Scheme of Australia and New Zealand)

mark. The EWPAA / JAS-ANZ brand on a plywood or

LVL product

certifies

the

product

has been

manufactured to the relevant Australian / New Zealand

Standard, under a quality control and product

certification scheme accredited by the peak government quality control accreditation body in Australia and

New Zealand. Purchasers of products stamped with the EWPAA / JAS-ANZ brand will be purchasing a

product, manufactured under an accredited third party audited, process based quality control program

that ensures the product will have uniform, predictable, reliable properties and will be fit for purpose. A list

of EWPAA plywood and LVL manufacturing members whose products carry the EWPAA / JAS-ANZ brand is

given on the back cover of this Manual.

1.4 Manufacturing Processes

The manufacturing process for both plywood and Laminated Veneer Lumber are similar. Materials used

in their manufacture are thin timber veneers bonded with an adhesive. However as the intended end

application is different (panel product versus framing member) the essential differences in the products is in

how the veneers are orientated. In essence, LVL could be considered as plywood without cross-bands, or,

alternatively plywood could be defined as cross-laminated LVL. Hence the main differences in the

manufacturing process occur at the lay-up and pressing stages. Prior to manufacture, logs from suitable

timber species are selected for peeling based on size, straightness and nature and quantity of defects. The

majority of EWPAA branded plywood is manufactured from plantation sourced radiata, hoop or slash

pine.

Manufacturing processes may vary from manufacturer to manufacturer, however the stages of production

are essentially as follows:

Conditioning

Logs are conditioned by immersion in a heated water bath or alternatively by steam treating.

Conditioning facilitates the peeling process by assisting in producing a smooth and even veneer. Roughly

peeled veneer is undesirable as it is more difficult to bond, requires more adhesive and the veneer is more

difficult to handle without damage.3

Peeling

After conditioning, the logs are debarked and cut into

suitable lengths, ready for peeling. These lengths are

referred to as peeler billets or peeler blocks. Peeling of

the billets is usually done in a rotary lathe. The peeler

billets are centred in the lathe and rotated for their full

length against the lathe knife. The lathe knife is fed

toward the centre of the log at a constant rate producing

a continuous ribbon of veneer of uniform thickness.

Typical veneer thicknesses peeled for commercial

plywoods range from 1 mm to 3.2 mm.

Drying

After peeling, the continuous ribbon of veneer is either clipped to size and dried, or continuously dried in

ribbon form and clipped after drying. The drying process ensures the veneer moisture content is uniform

and an appropriate value is achieved for bonding. The target moisture content is dependent on a number

of factors including the adhesive used, prevailing ambient conditions and the veneer species. Common

veneer moisture content limits after drying are in the range 6 to 12 %.

Grading

Plywood

The clipped and dried veneer sheets are sorted into veneer grades. Five veneer grades, A, B, C, D and

S are permitted for structural plywood.

LVL

The clipped and dried veneer is sorted for acceptable veneer quality. Some veneers are then passed

through a scarfing machine which creates a bevel each end. This allows the sheets to overlap, be

effectively glued and remain a uniform thickness. Structural LVL veneer is graded in accordance with a

predetermined manufacturer’s specification that ensures the minimum defined and published structural

properties of the LVL will be obtained.

Lay Up & Bonding

Plywood

Adhesive is applied to the cross-band veneers and veneers are laid up with alternating long bands and

cross-bands, ready for pressing. The normal plywood assembly is laid up such that each veneer in a

finished sheet of plywood has its grain direction at right angles to each adjacent veneer. Face grade veneers

and long band core veneers have the timber grain direction running in the long direction of the veneer.

Cross-band veneers have the timber grain direction running in the short direction. The plywood laid up

in this manner has a “balanced” construction. That is, veneer orientation and thickness is equal either side of

the centre of the plywood thickness.

LVL

Glue is spread on veneers by passing them through the rollers of a glue spreader or through a curtain

coater. The veneers are then usually laid up, with the grain direction of all veneers running in the long

direction. When required, LVL can be manufactured with cross-banded veneers to improve dimensional

stability and/or increase resistance to splitting when nailed. Typically, where cross-bands are included, the

veneer immediately below the face veneers is cross-banded.

Veneer ribbon exiting lathe after peeling4

After drying, the veneer is sorted into grades ready for lay-up

Veneer passing through the rollers of a glue spreader

Pressing

The assembled veneer lay ups are then cold pressed

to facilitate the bonding process and ensure good

adhesive transfer from the spread to the unspread

veneers.

After cold pressing, the plywood or LVL is hot

pressed for a set time between heated platens at a

set temperature and time to achieve proper bonding.

Typically plywood hot presses are suitable for maximum

plywood sheet sizes of 2700 x 1200 mm and have

multiple layers of platens so that 8 to 45 sheets of

plywood are pressed in each press load.

Plywood panels exiting 15 daylight (15 layers of

platens) hot press

Structural LVL fabricated in a dedicated LVL hot

press, is laid up on a moveable conveyor belt and

progressively hot pressed in a single layer press,

such that very long, continuous lengths are achieved.

Typically, LVL hot presses are 600 to 1200 mm in width,

permitting production of beam or column elements of

1200 mm depths by lengths in excess of 24 metres and

in thicknesses ranging from 35 to 75 mm.

Structural LVL manufactured in a plywood hot press will

be 2700 mm in length maximum.

LVL production lineSanding, Trimming and Branding

After pressing, the plywood panels are cooled and then trimmed to precise dimensions. Plywood

panels are then sanded if required and inspected for face quality.

LVL slabs are ripped into increments of the LVL slab width, allowing for saw cuts. For example, a 1200 mm

wide LVL slab may be trimmed to a 1200 mm deep beam/column element or into smaller elements that are

divisors of the maximum slab width. Typically maximum LVL slab widths are approximately 1200 mm.

LVL beams ripped from the slab have depths, of for example, 95, 130, 150, 170, 200, 240, 300, 360, 400, 450,

600 mm. Structural LVL face veneers are not usually sanded, but can be if required.

Prior to packing, the LVL or plywood is individually branded to identify the product type and structural

properties.

After trimming, sanding and branding, plywood panels undergo a final inspection for face quality

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Plywood & LVL – The Manufacturing Process

Plywood & LVL – The Manufacturing Process……………………………………………………………………………2 1.1 Introduction……………………………………………………………………………………………………………………..2 1.2 Manufacturing Standards ………………………………………………………………………………………………….2 1.3 Process …

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