Production process of plywood
| STORAGE AND PRESERVATION OF RAW MATERIAL Wooden raw material delivered to the factory is being stored partly on the ground storage unit, partly in the water (river and lake). Storingin the water preserves the wood mainly from damage caused by biological factors. Raw material kept on the ground is preserved permanently from early spring until early autumn by a system of sprinklers, which serves the same purpose as storing in the water. |
| HYDROTHERMAL TREATMENT The whole of raw material is treated thermally in the water to soften it.The logs are soaked in water pools in temperature 40-60°C depending on the type of wood. Soaking time depends on season, type of wood and log diameter and varies between 30 hours for birch, alder, pine, spruce and 72 hours for beech. |
| DEBARKING Mechanical debarking removes bark from logs, with mineral intrusions accumulated during life of the wood or acquired in process of cutting or transporting. |
| PEELING Block is transported to a rotary peeling machine. Axially fitted in the machine it starts rotate around its axis. The peeling knife moves forward and peels a layer of veneer in the form of a long band. Standard thickness of final veneer is 1.5 mm (we peel other thickness too: 0.8, 1.2, 2.0and 2.5 mm). |
| DRYING Acquired veneer, with moisture content of 30-120%, is dried in bands in belt-convey or dryers or in sheets in roll-conveyor dryers at 160-180°C to a final moisture content around 4-7%. |
| VENEER REPAIRS Veneers with natural defects (e.g. knots) are being repaired by removing defect areas and inserting in their place inserts from sound veneerin the shape of shims or patches (plugs).Stripes of veneer are jointed by edge gluing to form whole sheets. |
| SCARF JOINTING In order to obtain long grained veneer sheets of bigger sizes e.g. 3000mm standard size sheets are scarf jointed. |
| LAY-UP Lay-up – it is a selecting of veneer sheets for core and those for outer plies and putting them together. Usually panels are completed from odd number of veneers placed at right angle to each other. Glue is applied on both surfaces of every second veneer sheet on roll spreaders. The type of glue used depends on the type of plywood produced. |
PRESSING Assembled piles of veneer are pressed in multi-opening hot presses. |
| FINISHING TREATMENT Plywood panels are given final sizes by trimming on panel saws and calibrating thickness and smoothing surfaces by mechanical sanders. |
| SORTING Plywood panels undergo final quality control and are graded for defects. |
PACKING |
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