Coating board is unforgiving. The base sheet needs high bulk, excellent formation, and enough surface strength to hold a coating layer without picking or dusting. Get the refining wrong, and you’ll see one of two problems: low bulk from over-refining, or poor surface smoothness and coating holdout from under-refining.

Why Refiner Plate Geometry Matters for Coating Board

The refiner is where you engineer the fiber properties that define your final board quality. For coating board, the goal is fibrillation without excessive cutting — you want to develop bonding area on the fiber surface (for internal strength) while preserving fiber length (for bulk and stiffness).

This is fundamentally different from tissue refining (where softness and bulk are the goal) or kraft liner refining (where strength dominates). Coating board demands a precise balance.

Disc Refiner Plate Configurations for Coating Board

Leizhan’s disc refiners offer three primary plate pattern types, each producing distinct fiber development profiles:

Fine Bar Plates (Type F)

• Bar width: 2.0–3.2 mm
• Groove width: 2.5–3.5 mm
• Bar angle: 15–20°
• Best for: Top layer stock where surface smoothness and coating holdout are critical
• Freeness reduction: 35–50° SR per pass at 40–60 kWh/t specific energy

Medium Bar Plates (Type M)

• Bar width: 3.2–4.5 mm
• Groove width: 3.5–4.5 mm
• Bar angle: 10–15°
• Best for: Middle layer or filler ply — balances strength development with bulk retention
• Freeness reduction: 25–40° SR per pass at 30–50 kWh/t

Coarse Bar Plates (Type C)

• Bar width: 4.5–6.0 mm
• Groove width: 4.5–6.0 mm
• Bar angle: 5–10°
• Best for: Back layer where bulk and stiffness are prioritized over surface quality
• Freeness reduction: 15–25° SR per pass at 20–40 kWh/t

Specific Edge Load (SEL): The Critical Parameter

For coating board, the target SEL range is 1.0–2.0 W·s/m for top layer and 1.5–3.0 W·s/m for filler/back layers. Lower SEL values produce more fibrillation and less cutting — exactly what the top layer needs. Higher SEL increases cutting action, which can be useful for breaking down shives in the filler layer.

The formula: SEL = Net Power (kW) / (Bar Length × Rotational Speed × Number of Bars)

For a typical Leizhan 26-inch double disc refiner operating at 200 kW net power with fine bar plates at 980 RPM, SEL runs approximately 1.6–1.8 W·s/m — right in the sweet spot for coating board top layer stock.

Energy Efficiency in Coating Board Refining

Modern Leizhan disc refiners achieve no-load power as low as 10–15% of motor rating thanks to precision-balanced rotors and optimized plate design. This means more of your kWh go into fiber development, not heat and noise. Typical specific energy for coating board stock preparation:

• Top layer: 50–80 kWh/t (depending on virgin/ratio and target freeness)
• Filler layer: 30–50 kWh/t
• Back layer: 20–35 kWh/t

Plate Life and Replacement Indicators

Refiner plates are a consumable, and their condition directly impacts product quality. Replace plates when:

• Bar height reduction exceeds 50% of original
• Specific energy increases more than 15% to achieve the same freeness target
• Plate gap must be closed beyond 0.05 mm to maintain load
• Typical plate life: 6–12 months for fine bars, 8–18 months for medium/coarse bars (virgin fiber feeds extend life)

Getting the refining right is the difference between coating board that runs at full machine speed with zero coating defects, and board that generates customer complaints. The investment in the right plates pays back every day on the machine.

📧 Contact us at leizhanzhang@gmail.com for plate selection assistance, energy audits, or to schedule a trial with your specific furnish.