Plywood production in Russia has demonstrated constant growth in recent decades. Export-oriented Russian birch plywood manufacturers invest in expansion of production capacities and more value-added products. Russian plywood producers have numerous competitive advantages in comparison with other producers, such as wood raw material and labor costs.
Birch logs serve as raw material for plywood manufacture. The raw material is supplied to the enterprises by railway, by trucks and also by waterway/
The hydrothermal processing of plywood raw material is performed before veneer peeling to increase the plastic properties of timber and to provide qualitative veneer. The hydrothermal processing is carried out by boiling of raw material in boiling pools. There are open pools of cyclic type, and also covered pools of continuous type.
Debarking and Cutting
Timber products for the peeled veneer manufacture are supplied to the enterprise in blocks. The blocks for peeling after hydrothermal processing are cut for blocks ready for peeling.
Peeling is a process of timber cutting at which a continuous tape of wood - veneer - is removed from the rotating block by the forward moving knife. The continuous tape of wood is cut for the format with the help of scissors and piled. Then veneer is moved to drying.
Drying of veneer
Drying of veneer is performed by roller dryers. Veneer is moved along the dryer by the system of a pair of rotating rollers. When passing the drying chamber, veneer is dried up to humidity of 6 ±2%. In the cooling chamber veneer is cooled.
Sorting of veneer
Veneer is sorted by the grades: B, BB, CP (WG), C - for the external layers and for internal layers according to the technological instruction.
Repairing of veneer
Repairing of veneer is a technological process of veneer elevation with the purpose of increase of its grade. The repairing includes removal of defects from veneer sheets with the subsequent closing up of these places by inserts from qualitative veneer, and also gluing of face cracks with glutinous tape, or stapling of cracks with metal clips.
Plywood manufacture from veneer
The technological process of plywood manufacture consists of the following operations:
- Preparation of glue;
- Application of glue to veneer;
- Formation of packages;
- Preliminary cold pre-pressing
- Hot pressing.
Gluing and laying up
This process includes application of a glutinous layer to veneer by the glue application machine tool by passing of the veneer sheets between the rotating glutinous drums and stacking of veneer sheets in a certain sequence depending on the grade and thickness of plywood.
Plywood is glued by hot technique in hydraulic press with maintenance of a certain temperature mode depending on the mark and thickness of plywood. Before hot pressing the plywood packages pass cold pre-pressing. Stuck together plywood after 24 hour conditioning is sent to edge scrapping and grinding.
Plywood edge trimming
This operation is made with the purpose of giving the certain geometrical sizes to plywood. The operation is made over each sheet by format-edging machine tools located one after another and making paired scrapping of two parallel edges of a sheet.
Sanding of plywood
This operation is carried out for alignment of plywood surface and elimination of difference in thickness, and also for giving the product more attractive commercial appearance. The supreme and average grades of plywood only are exposed to sanding.
Grading of plywood
At sorting the following is determined: the amount and defects of timber, defects of processing, durability of gluing, sizes, deformation of sheets. The sorters of plywood visually determine the grade of each sheet and reveal the hidden defects: stratifications, bubbles. Bubbles are found by knocking the surfaces of plywood with wooden hammer or with the help of automatic ultrasonic defect scopes. The plywood with stratifications is rejected. At sorting the manual completion of plywood is also carried out with the purpose of elimination of some defects, for example, additional polishing of separate places, puttying of cracks. Some sheets of plywood are directed for additional scrapping with the purpose of elimination of defects which cannot be removed by sorting.
Marking and packing of plywood sheets
On each sheet of plywood precise marks as a round stamp are put by an indelible paint. The stamps are put in the right corner of the reverse side of plywood. All plywood is packed into the packages providing integrity and safety while delivery. Plywood is subject to protection from above and from below by covers and from the lateral faces - by facings. The marks of packages are made by an indelible typographical paint and are put onto two opposite facings of a package.
Plywood is stored in the specially equipped warehouse of finished goods with the environment protection provided.