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Understanding Veneer Thickness in Plywood Production
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Understanding Veneer Thickness in Plywood Production
Veneer is a thin wood layer sliced from a log to create plywood, and its thickness plays a critical role in determining the quality and performance of the final product. Many misunderstand how veneer thickness is measured and managed. This article covers everything you need to know, including types of thickness, changes during production, factors affecting peeling, and methods to calculate it from finished plywood. Master these insights to produce high-quality plywood with optimal veneer thickness.
Types of Veneer Thickness and How They’re Measured
Veneer thickness varies across four key stages:
Nominal Thickness: The theoretical thickness based on finished plywood. For example, an 18mm plywood with 5 layers suggests a nominal thickness of 3.6mm per veneer.
Actual Peeling Thickness: Measured right after slicing, slightly thicker than nominal to account for processing allowance, compression, shrinkage, and deviations.
Thickness Before Gluing: Measured post-drying, reduced due to moisture loss and shrinkage.
Thickness in Finished Plywood: Measured after gluing and hot pressing, further reduced by compression from heat and pressure.
To ensure accuracy, use a screw micrometer consistently at the same point on the veneer—after peeling, before and after drying, and post-gluing—to track subtle changes.
Changes in Veneer Thickness During Production
The veneer thickness shifts throughout the plywood production process due to:
Rebound: Post-peeling, elastic compression from the peeling machine causes a slight thickness increase as the veneer relaxes.
Shrinkage: Drying removes moisture, shrinking the veneer and reducing its thickness significantly. Shrinkage varies by wood type, moisture content, and drying conditions.
Expansion: Gluing introduces moisture from adhesive, slightly swelling the veneer before pressing.
Compression: Hot pressing compacts the veneer under heat and pressure, decreasing its thickness in the final product.
Factors to Consider When Setting Peeling Thickness
Determining the peeling veneer thickness requires attention to:
Finished Plywood Thickness: The peeling thickness must align with the final product (e.g., 3.6mm nominal for an 18mm, 5-layer plywood).
Processing Allowance: Extra thickness (e.g., 0.2mm) to offset shrinkage, compression, and deviations, varying by wood type and conditions.
Rebound and Expansion: These increases—dependent on wood species, moisture, and processing—must be factored in to avoid underestimating the initial cut.
How to Calculate Veneer Thickness from Finished Plywood
To reverse-engineer the peeling veneer thickness from finished plywood, consider:
Compression: Calculated from the thickness before gluing (post-drying), as it occurs during hot pressing.
Shrinkage Ratio: Based on actual moisture content, not absolute dry state, for realistic results.
Use this formula: Peeling Veneer Thickness = (Finished Plywood Thickness / Number of Layers) + Processing Allowance - Rebound - Expansion
Example: For an 18mm plywood with 5 layers, a 0.2mm allowance, 0.05mm rebound, and 0.1mm expansion: Peeling Thickness = 18 / 5 + 0.2 - 0.05 - 0.1 = 3.75mm
Conclusion: Optimize Your Plywood with Precision
Understanding and controlling veneer thickness ensures top-tier plywood quality. By mastering measurement types, production changes, and calculation methods, you can tailor the process to your needs. For more insights on veneer for plywood or production tips, feel free to reach out
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