How is Plywood made : The Full Process Explained | Part-5

In the previous article, we explored the intermediate processing steps—including trimming, putty filling, calibration, face veneer overlaying, and both cold and hot pressing with the face layer.

In this final part of the series, we will look at the finishing operations that transform the panel into a market-ready plywood sheet.

• Trimming
• Side Gap Filling
• Sanding
• Dipping
• Grading & Quality Check

Trimming

After the face-veneered panel comes out of the hot press, its edges remain slightly oversized or uneven. To bring the sheet to precise commercial dimensions, it is trimmed using a DD Saw or an edge-trimming machine.

Earlier—before calibration—the Mat Ply was trimmed with a small margin to allow for face veneer overlaying. Now, in this final trimming stage, the panel is accurately cut to the standard 4 ft × 8 ft size.

Side Gap Filling

When the plywood edges are inspected closely, small gaps or voids may sometimes be visible in the cross-section. If left unfilled, these gaps can allow moisture, dust, or even insects to enter the panel, eventually compromising its durability and performance.

To prevent this, a process called Side Gap Filling is carried out. In this step, suitable fillers are applied to seal these edge gaps completely. The filler may be putty-based or resin-based, depending on the manufacturing standards and the desired finish. Once applied and dried, the edges become smooth, compact, and better protected from external elements.

With the dimensions perfected and side gap filled, the plywood moves to the next finishing stage: Sanding.

Sanding

Sanding is a crucial finishing stage in plywood manufacturing, responsible for giving the plywood its smooth, uniform, and visually appealing surface.

While the calibration phase removes thickness variations and undulations from the Mat Ply using hard steel rollers, the sanding phase focuses on refining the final surface quality using soft rubber rollers that allow controlled, uniform abrasion without damaging the face veneer.

After the face veneer has been applied during pressing, sanding ensures that the surface becomes clean, even, and ready for further use. It removes minor imperfections, glue squeeze-out, and grain roughness. The process also enhances the natural sheen of the plywood, especially when finer grits are used toward the end.

The machine used for this process is a Wide Belt Sanding Machine, equipped with abrasive belts of progressively finer grit sizes. Typically, a 150-grit belt is used on the first head, followed by a 180-grit belt on the second head. In some cases, a finer combination of 180–220 grit is also employed to achieve a smoother finish.

Dipping

Plywood is naturally susceptible to termites, borers, fungi, and other biological threats unless it undergoes proper chemical treatment.

The Dipping Process is a preservation technique in which dried veneers or fully pressed plywood sheets are immersed in a specially formulated chemical solution. This solution typically contains a blend of preservatives, anti-borer agents, anti-termite chemicals, and antifungal additives, designed to penetrate the wood and enhance its long-term durability.

The primary purpose of this treatment is to protect the plywood from:

• Termite attacks
• Wood-boring insects
• Fungal growth
• Moisture-related degradation
• Microbial or biological decay

For the dipping process, a large tank is filled with the protective chemical solution. The plywood is then submerged in it for a duration that can range from a few minutes to several hours, depending on the plywood grade and the level of protection required. After immersion, the sheets are taken out and thoroughly dried to ensure the chemicals are properly set and effective.

Grading & Quality Check

After the dipping process, the plywood sheets are dried and moved to the final grading and quality inspection stage. The first step is a detailed surface examination, where each sheet is checked for smoothness, uniform chemical absorption, and overall finish after sanding. Inspectors look for defects such as cracks, overlaps, open core gaps, dents, or resin patches. Any sheet showing these minor defects is sent for correction through re-sanding, edge filling, or touch-ups.

Next comes the dimensional and structural evaluation. Technicians measure the sheet’s thickness, ensure proper flatness, and check for warping or twisting. The edges are inspected for any remaining gaps, and bonding quality is assessed using tapping tests to detect internal delamination or weak spots. Sheets that fail these checks are either rejected or downgraded depending on the severity of the issue.

Finally, suitable sheets are classified into grades based on face appearance, structural performance, and bonding type. This includes assigning face grades (A, B, C, or D) and confirming bonding grades such as MR, BWR, or BWP. Once grading is complete, the plywood is stamped with ISI markings, batch numbers, and manufacturer details before being packed and dispatched for sale or further distribution.

Conclusion

This brings us to the end of our five-part blog series on how plywood is manufactured. Throughout the series, we walked step-by-step through the entire journey—from harvesting logs to the final quality checks that determine the grade of each sheet. If you’ve read along, you now understand just how much science, engineering, and care are involved in making plywood. We hope this series has been informative and valuable.