Plywood Manufacturing process
Plywood Manufacturing process
1. Hydrothermal wood logs processing
Wood logs which are the raw material for plywood manufacturing undergo hydrothermal processing. The hydrothermal processing is carried out in soaking pools filled with water at a temperature of 40–60°C depending on the wood species. Next, through mechanical debarking, the logs are cleared of bark and mineral residues accumulated in the bark during the process of logging and transport.
2. Debarking
The debarking process in plywood manufacturing involves the removal of the bark from logs before they are processed into veneer. This step is crucial for ensuring the quality of the final product, as bark can introduce defects and impurities. Typically, logs are fed into a debarker machine, which uses mechanical means, such as rotating blades or rollers, to strip away the bark while preserving the wood underneath. After debarking, the logs are usually cut into manageable lengths and prepared for further processing, such as peeling or slicing, to produce the thin sheets of veneer used in plywood.
3. Peeling
A cut to size wood log is delivered to a rotary peeling machine. Once fitted at right angle against a rotary peeling Once fitted at a right angle against a rotary lathe, a log is being rotated against the blade. The peeling blade cuts a layer of veneer in the form of a veneer band.
a. Vacuum pressure treatment
b. Thermo Mechanical treatment
4. Core Processing
Material Feeding System: Automatically feeds core materials (like wood veneers or strands) into the compression chamber.
Compression Chamber: The area where the layers are compressed together.
Hydraulic or Pneumatic Ram: Applies controlled pressure to the layers, ensuring proper bonding.
Control System: Monitors and controls the compression process, often equipped with sensors for pressure and temperature.
5. Drying and surface repairing of veneers
At this stage veneers have a moisture content of 30–120%. In order to reduce the moisture to the required level, veneers are dried in a continuous process in a band drying facility or as sheets in roller drying facilities, at a temperature of 160–180°C, to reach the desired moisture content of about 8 – 12%. Any veneer defects caused by the wood anatomy (e.g. knots, close shakes, bud traces, etc.) are identified by using specialist scanning systems. Such surface defects are repaired with veneer inserts or chocks that match in colour and woodgrain pattern.
6. Panel Composure
Feeding System: A conveyor or loading mechanism that delivers plywood panels to the compression chamber.
Compression Chamber: The area where the panels are compressed.
Hydraulic or Pneumatic Press: Applies controlled pressure to the panels.
Control System: Manages the compression process, often equipped with timers and pressure sensors.
Heating Elements (optional): Some machines include heating elements to activate adhesives during compression.
Discharge System: Releases the compressed panels after processing.
7. Adhesive application and plywood sets assembly
The sets of face and core veneers are assembled by selecting and arranging veneer sheets in a proper way. Depending on the intended use of the final product and a customer’s requirements, the sheets are laid cross-grained in a classic way, cross- and parallel-grained or parallel-grained in relation to each other. The adhesive is applied on both sides onto every second sheet of veneer. The type of the adhesive compound determines the type of bonding used for the specific plywood.
8. Cold Pressing
Pressing: The stacked veneers are placed in a cold press, which applies mechanical pressure. This pressure helps to bond the layers together without the need for heat.
Duration: The pressing time can vary depending on the type of adhesive used and the thickness of the plywood, usually ranging from a few minutes to a couple of hours.
9. Hot Pressing
Press Setup: The stacked veneers are placed in a hot press, which consists of heated platens.
Temperature and Pressure: The platens are heated to temperatures typically ranging from 120°C to 200°C (248°F to 392°F) while applying significant pressure (often between 1 to 2 MPa).
Pressing Time: The duration of pressing varies based on thickness and type of adhesive, generally lasting from a few minutes to over an hour.
We also use Plasma – Technology based on customers requirement. It is an advanced process that enhances the surface properties of plywood using plasma technology. Plasma treatment involves exposing the plywood to an ionized gas (plasma), which modifies the surface properties to improve adhesion, water resistance, and durability without the use of chemical treatments. This eco-friendly method is gaining popularity due to its ability to enhance surface properties without affecting the core structure.
Plasma Treatment System / Plasma Chamber: After the Hot Pressing of the Plywood Panel the same is processed in an enclosed chamber where the plywood panels are exposed to plasma generated by ionizing gases such as oxygen, nitrogen, or argon. The plasma modifies the surface without penetrating into the plywood’s core, ensuring structural integrity is maintained.
After plasma treatment, the plywood panels are inspected for surface quality and bonding improvements. Plasma treatment also prepares the plywood for further coatings or laminations.
10. Calibration
A calibrator is a specialized machine used for finishing and sizing plywood sheets after they have been pressed and cured. The calibrator plays a crucial role in ensuring that the plywood meets specific thickness, smoothness, and surface quality standards
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Feeding: Plywood sheets are fed into the calibrator, usually using rollers to ensure consistent movement.
Trimming: The cutting heads move across the surface, removing material to achieve the specified thickness.
Smoothing: Sanding or polishing the surface for a smoother finish.
Quality Control: Continuous monitoring ensures that the finished sheets meet quality standards.
Duration: The pressing time can vary depending on the type of adhesive used and the thickness of the plywood, usually ranging from a few minutes to a couple of hours.
11. Second Cold Pressing
Second cold pressing is a critical step in plywood manufacturing that occurs after the initial adhesive application and assembly of veneer layers. In this phase, pressure is applied to the assembled plywood at room temperature, ensuring a strong bond between the layers without the influence of heat. This process allows for better control over the adhesive curing time, minimizing the risk of defects caused by heat exposure. It is particularly useful for enhancing the uniformity and flatness of the panels, leading to improved quality and dimensional stability in the final product.
13. Final processing and sanding
Following the seasoning of plywood, the plywood sheets are finally processed and cut to target size with the excess mate rial cut off on a profiling machine. Next the surfaces of face Veneers are calibrated and sanded in a precise sanding machine.
14. Overlaying, filming, surface treatment
If required by the end application of plywood panel, at this stage in the process a special paper impregnated with resin (also referred to as film) is applied onto the surface of plywood board. This process is carried out in high pressure and high temperature environment, causing the resin to pass to the core veneers and, as a result, to produce a surface with new performance properties.
15. Quality inspection and grade sorting
Sorting of plywood is based on quality inspection and classi- fication of plywood face veneers in line with quality systems’ requirements, technical standards and specifications.
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SY.NO.132/16 TO 28, Maruvada Village, Arjunavalasa Post, Ranasthalam Mandal, Srikakulam District, PIN-532409
info@pandoply.com
+91 99633 22663
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