II. Guess the following words using ex. I.

1. c . . e 6. p . . - . . . . . . . g

2. p . . e . b . . . k 7. . l . . . o .

3. l . . . e 8. s . . . t . . . .

4. . e . . . r 9. . . m . . . . . n

5. a . . . s . . e 10 . . . d - . . . . d

III. Use the words from exercise II in the following sentences and translate them:

1. Plywood belongs to the class of _____ composite materials.

2. The inner plies are called _____ .

3. _____ can be made either from softwoods or hardwoods.

4. After the logs are debarked they are crosscut into _____ .

5. Greater resistance to _____ is one of the advantages of the plywood

panels structure.

6. The properties of plywood depend on the quality of the different

layers of veneer, order of layer placement, _____ used, and control

of bonding conditions.

7. Plywood is a flat panel which is made of sheets of _____ called plies.

8. Peeler blocks are often heated by steaming or _____ in hot water

before peeling, which makes them easier to peel.

9. The heated blocks are brought to a veneer-cutting ____ .

10. Panels are first subjected to cold _____ to flatten the veneers.

IV. Read and translate the text. Plywood

Plywood belongs to the class of wood-based composite materials. Plywood is a flat panel which is made of sheets of veneer called plies, united under pressure by a bonding agent to create a panel. Plywood can be made either from softwoods or hardwoods. It is always constructed with an odd number of layers with the grain direction of adjacent layers oriented perpendicular to one another. The outer plies are

called face plies and their grain (fibres) is parallel to each other. The inner plies are

called core and its grain is at the right angle to the grain of the face plies. The plies can vary in number, thickness, species and grade of wood.

The structure of plywood panels provides them with numerous advantages over solid wood. Some of these advantages are: 1) nearly equal properties both along the length of the panel and width, 2) greater resistance to splitting, 3) the form makes it possible to use panels where large sheets are desirable. The properties of plywood depend on the quality of the different layers of veneer, order of layer placement, adhesive used, and control of bonding conditions. The grade of the panel depends upon the quality of the veneer used, particularly of the faces.

Generally speaking, there are two classes of plywood: 1) construction and industrial, and 2) hardwood and decorative. Construction and industrial plywood is used where strength and stiffness are more important than appearance. Hardwood and decorative plywood is normally used for decorative wall panels and for furniture and cabinet panels where appearance is more important than strength.

Fig. 1. Veneer Lathe

Today, plywood is made from low-grade sawlogs or peeler logs. After the logs are debarked they are crosscut into peeler blocks. Peeler blocks are often heated by steaming or immersion in hot water before peeling, which makes them easier to peel.

The heated blocks are then brought to a veneer-cutting lathe. While rotating at high speed, the block is pressed against a stationary cutting knife, veneer is peeled from the block in a continuous, uniformly thin strip, much like unwinding a roll of paper.

The continuous strip of veneer is then clipped into sheets of various width and defects are removed. The wet veneer is then dried in the steam- heated conveyor-drier. It is important that veneer moisture content be low at the time of adhesive is applied, so, sometimes pieces that are too wet are run through the drier again to reduce the moisture content to the desired level. The dried material is taken to the layup area.

Adhesive is applied to veneers in the layup area by spray, curtain coating, roller coating. The core sheets are coated evenly with adhesive on both sides. Veneer is laid up into plywood by hand or machine, or a combination of both.

Once assembled, panels are taken from the layup area to the pressing area. Panels are first subjected to cold pre-pressing to flatten the veneers, panels are then hot pressed. After hot pressing, panels are sawn to size, and then passed onto sanding machines where both surfaces are sanded to satin smoothness. Each panel is inspected and then graded. The panels are then ready for shipment.