Production Process and Quality Inspection Checklist for 100% PINE FILM FACED PLYWOOD and RECYCLED FULL PINE JOINT CORE FILM FACED PLYWOOD
1. 100% PINE FILM FACED PLYWOOD
1.1 Production Process
Log Preparation: Select high-quality 100% pine logs (Pinus sylvestris or Pinus radiata preferred) with no severe decay, insect infestation, or mechanical damage. Debark the logs completely using a rotary debarker, ensuring no residual bark remains on the log surface to avoid defects in veneers.
Veneer Peeling: Use a rotary veneer lathe to peel the debarked logs into continuous pine veneers. Control veneer thickness uniformity (common thickness: 1.2mm-2.5mm) and ensure smooth veneer surface without cracks, tears, or excessive wood fiber fluffing. The veneer moisture content after peeling shall be controlled at 40%-60%.
Veneer Drying: Convey the green veneers to a continuous hot-air drying kiln. Dry the veneers to a moisture content of 6%-12% (optimal range: 8%-10%) to meet gluing requirements. Control drying temperature (70℃-90℃) and airspeed to prevent veneer warping, discoloration, or cracking.
Veneer Grading and Trimming: Grade veneers based on surface defects (knots, cracks, discoloration) and thickness deviation. Classify into face veneer, core veneer, and back veneer. Trim unqualified parts to ensure veneer size meets production specifications, and remove impurities on veneer surface.
Glue Application: Adopt cold-press or hot-press urea-formaldehyde resin adhesive (for interior use) or phenol-formaldehyde resin adhesive (for exterior use). Apply glue uniformly on core veneer surfaces using a roller coater, with glue spread rate controlled at 200g/m²-250g/m² (double-sided). Ensure glue layer is even without missing coating or excessive glue accumulation.
Mat Formation: Stack veneers in cross-grain direction (face/back veneer grain parallel to board length, core veneer grain perpendicular) to enhance board strength. The number of layers is determined by target board thickness (common layers: 3, 5, 7, 9). Ensure mat is flat and veneers are aligned without offset.
Hot Pressing: Transfer the mat to a hot press. Set parameters: temperature 120℃-150℃, pressure 1.0MPa-1.5MPa, pressing time 0.8min/mm-1.2min/mm (based on board thickness). Control pressing speed and pressure stability to ensure sufficient glue curing and firm bonding between veneers. Avoid over-pressing or under-pressing.
Post-Pressing Treatment: After hot pressing, cool the board to room temperature naturally (cooling time ≥24h) to release internal stress. Trim the board edges to standard size using a precision edge trimmer, ensuring straight edges and right angles. Sand the board surface lightly to remove burrs and unevenness.
Film Lamination: Laminate phenolic resin film (or melamine film) on the face and back surfaces of the plywood. Use hot pressing for film bonding: temperature 130℃-160℃, pressure 0.8MPa-1.2MPa, pressing time 30s-60s. Ensure film is tightly bonded with no bubbles, wrinkles, or peeling. The film thickness shall be 0.12mm-0.20mm.
Final Trimming and Packaging: Perform final trimming to ensure board size accuracy and edge smoothness. Inspect finished products, then package with waterproof paper or plastic film, and bundle firmly to prevent damage during transportation.
1.2 Quality Inspection Points
1.2.1 Appearance Quality
Surface: Film surface shall be flat, smooth, and uniform in color, with no bubbles, wrinkles, peeling, scratches, or stains. Face/back veneers shall have no loose knots (diameter >3mm), dead knots, cracks, or discoloration that affects appearance.
Edges: Straight and smooth, no edge splitting, delamination, or fiber fluffing. Edge perpendicularity error ≤0.5mm/m, edge straightness error ≤0.3mm/m.
Shape: No warping, twisting, or bowing. Warpage degree ≤1.0mm/m, bowing degree ≤0.8mm/m.
1.2.2 Internal Performance
Moisture Content (MC): 6%-12%, measured at 3 different positions of the board, with maximum deviation ≤2%.
Glue Bond Strength: ≥1.0 N/mm² (for exterior grade), ≥0.7 N/mm² (for interior grade). No delamination or glue failure after testing.
Film Defects: Bubbles (caused by insufficient glue curing or air entrapment during lamination), wrinkles (uneven film tension), peeling (poor glue adhesion or low pressing temperature), scratches (mechanical damage during processing).
Veneer-Related Defects: Loose knots (unstable knot bonding), dead knots (fallen knots), cracks (drying too fast or veneer quality issues), discoloration (moisture imbalance or mold growth).
2. RECYCLED FULL PINE JOINT CORE FILM FACED PLYWOOD
2.1 Production Process
Recycled Pine Material Collection & Sorting: Collect waste 100% pine plywood, pine lumber scraps, or pine veneer leftovers. Sort by material type, removing non-pine components (metal, plastic, hardwood) and severely decayed/damaged parts. Classify recycled materials into core material (for joint core) and supplementary veneer.
Core Material Processing: Shred the sorted recycled pine materials into small wood strips (width 20mm-50mm, length 50mm-200mm) using a wood shredder. Dry the wood strips to moisture content 8%-12% to avoid internal stress and glue failure. Trim wood strips to uniform size, removing burrs and uneven ends.
Joint Core Fabrication: Arrange the dried pine wood strips in a staggered joint manner (joint gap ≤2mm) on a forming machine. Apply phenol-formaldehyde resin adhesive to the joint surfaces, with glue spread rate 180g/m²-220g/m². Press the joint core under cold press (pressure 0.8MPa-1.2MPa, pressing time 30min-60min) to form a solid core board. Trim the joint core to standard size, ensuring flatness and thickness uniformity (core thickness based on final board specification).
Face/Back Veneer Preparation: Use new 100% pine veneers (thickness 1.5mm-2.0mm) as face/back veneers. Process as per 100% PINE FILM FACED PLYWOOD: peeling, drying (MC 6%-10%), grading, and trimming. Ensure face veneers have no obvious defects to guarantee appearance quality.
Glue Application & Mat Formation: Apply phenol-formaldehyde resin adhesive on both sides of the joint core and the inner surfaces of face/back veneers. Glue spread rate: 220g/m²-260g/m² (double-sided for joint core). Stack in the order: face veneer → joint core → back veneer, with grain direction cross-aligned. Ensure mat alignment, no offset, and tight fitting between layers.
Hot Pressing: Transfer the mat to a hot press. Set parameters: temperature 130℃-160℃, pressure 1.2MPa-1.8MPa, pressing time 1.0min/mm-1.5min/mm (longer than conventional plywood due to joint core). Control temperature and pressure uniformity to ensure full glue curing and firm bonding between face/back veneers and joint core. Avoid joint core delamination during pressing.
Post-Pressing Treatment: Cool the pressed board to room temperature (cooling time ≥36h) to release internal stress caused by recycled core. Trim edges with precision edge trimmer, ensuring straight edges and right angles. Sand the surface lightly to remove burrs and unevenness, preparing for film lamination.
Film Lamination: Same as 100% PINE FILM FACED PLYWOOD. Laminate phenolic/melamine film on face/back surfaces via hot pressing (temperature 130℃-160℃, pressure 0.8MPa-1.2MPa, time 30s-60s). Ensure film adhesion, no bubbles, wrinkles, or peeling. Strengthen edge film bonding to prevent edge peeling.
Final Inspection & Packaging: Inspect finished products for appearance, size, and performance. Package with waterproof materials, bundle firmly, and mark “recycled pine” for identification. Ensure packaging prevents moisture absorption and mechanical damage during transportation.
2.2 Quality Inspection Points
2.2.1 Appearance Quality
Surface: Film surface flat, smooth, uniform color, no bubbles, wrinkles, peeling, scratches, or stains. Face/back veneers free of large knots (diameter >4mm), cracks, or discoloration. No obvious joint marks of the core layer showing through the face veneer.
Edges: Straight, smooth, no splitting, delamination, or fiber fluffing. Joint core shall not be exposed at edges. Edge perpendicularity error ≤0.6mm/m, edge straightness error ≤0.4mm/m.
Shape: No warping, twisting, or bowing. Warpage degree ≤1.2mm/m, bowing degree ≤1.0mm/m.
2.2.2 Internal Performance
Moisture Content: 7%-13%, maximum deviation between different positions ≤2.5%.
Glue Bond Strength: ≥0.9 N/mm² (exterior grade), ≥0.6 N/mm² (interior grade). No delamination between face/back veneers and joint core, or within joint core.
Joint Core Defects: Joint separation (insufficient glue application or pressing pressure), joint gap excessive (≥2mm, causing surface unevenness), core cracking (dry wood strips or excessive pressing pressure), core exposure at edges (improper trimming or mat alignment).
Film Defects: Same as 100% PINE FILM FACED PLYWOOD; additional edge film peeling (caused by exposed joint core or insufficient edge pressing).
Gluing Defects: Delamination between face veneer and joint core (uneven glue application on core surface), glue line voids (air entrapment in joint core gaps), glue failure (low adhesive quality for recycled materials).
Shape Defects: Severe warping/twisting (uneven moisture content of recycled core or unbalanced mat stacking), bowing (uneven cooling or joint core density inconsistency).
Surface Defects: Joint marks showing through (thin face veneer or uneven joint core surface), discoloration (recycled core with mold or residual stains), surface unevenness (joint core height difference).
Other Defects: Foreign matter inclusion (unremoved metal/plastic in recycled materials), edge splitting (dry joint core or dull trimming blade), reduced strength (mixed non-pine materials in core).
