The Double backer (also called the double facer) is the section of a corrugator line where the single‑face web (fluted medium + one liner) is bonded to the outer liner to form single‑wall, double‑wall, or triple‑wall corrugated board.
It uses heat, adhesive, and pressure to cure the glue applied in the glue machine, ensuring a flat, well‑bonded, and dimensionally stable board.
It also transports the board through the hot plate section and into the dry end for slitting, scoring, and cutting.
Construction Features
Hot Plate Section
Rows of steam heated plates that transfer heat to cure the adhesive.
Pressure System
Ballast rolls, pressure shoes, or sandwich systems to press the board against the hot plates.
Conveyor Belt
Heat resistant, air permeable belt (corrugator belt) to hold the board flat and allow steam to escape.
Belt Tracking & Tensioning System
Manual or automatic setting of the gap between applicator and doctor rolls for precise coating.
Cooling Section
Stabilizes the board after bonding.
Drive System
Synchronizes belt speed with upstream sections.
Frame & Access Doors
Heavy duty frame with large access for cleaning and maintenance.
Control System
PLC/HMI for temperature, pressure, and speed control.
Common Types
- Ballast Roll Systems – Heavy rolls press the belt onto the board; simple but less adaptable to edge caliper loss.
- Pressure Shoe Systems – Continuous shoe contact for uniform pressure; better heat transfer.
- Sandwich Systems – Belt runs between upper and lower pressure elements for maximum control.
- Hybrid Systems – Combine rolls and shoes for optimal heat and pressure distribution.
- Short Double Facers – Compact design for quick grade changes and reduced waste
Key Selection Factors
When specifying or upgrading a double facer:- Board Grades & Flute Types – Heavy double/triple wall needs higher pressure and heat capacity.
- Production Speed – High‑speed lines (>350 m/min) require advanced belt, pressure, and heat systems.
- Heating Capacity – Number and size of hot plates, steam pressure, and temperature control.
- Pressure System Type – Roll, shoe, or hybrid based on product mix and quality requirements.
- Belt Specification – Heat resistance, air permeability, thickness, and tracking stability.
- Warp Control – Ability to adjust heat and moisture to prevent warp.
- Automation Level – Servo‑controlled pressure, automatic belt tracking, recipe storage.
- Maintenance Access – Easy cleaning of plates, belt, and glue areas.
- Energy Efficiency – Insulation, heat recovery, and optimized steam usage.
Key Selection Factors
When specifying or upgrading a double facer:- Board Grades & Flute Types – Heavy double/triple wall needs higher pressure and heat capacity.
- Production Speed – High‑speed lines (>350 m/min) require advanced belt, pressure, and heat systems.
- Heating Capacity – Number and size of hot plates, steam pressure, and temperature control.
- Pressure System Type – Roll, shoe, or hybrid based on product mix and quality requirements.
- Belt Specification – Heat resistance, air permeability, thickness, and tracking stability.
- Warp Control – Ability to adjust heat and moisture to prevent warp.
- Automation Level – Servo‑controlled pressure, automatic belt tracking, recipe storage.
- Maintenance Access – Easy cleaning of plates, belt, and glue areas.
- Energy Efficiency – Insulation, heat recovery, and optimized steam usage.
Maintenance & Care
- Daily Cleaning – Remove starch build‑up from belt edges and hot plates.
- Belt Care – Keep belt clean, check tension and tracking, rotate or flip periodically.
- Hot Plate Maintenance – Inspect for flatness, clean surfaces, check steam traps.
- Pressure System Checks – Inspect rolls, shoes, and bearings for wear.
- Alignment – Ensure belt and board path are straight to avoid edge damage.
- Lubrication – Follow OEM schedules for bearings and moving parts.
- Temperature & Pressure Calibration – Maintain consistent curing conditions
Key Parameters to Order
| Parameter | Why It Matters | Typical Range / Note |
|---|---|---|
| Machine Width | Must match corrugator | 1800–2800 mm |
| Max Speed | Matches line capacity | 150–400 m/min |
| Hot Plate Length | Heat transfer capacity | 20–40 m typical |
| Hot Plate Size & Number | Heating efficiency | OEM‑specific |
| Pressure System Type | Bond quality & warp control | Roll, shoe, hybrid |
| Belt Type | Heat resistance & stability | Aramid/polyester blend, 6–10 mm thick |
| Belt Air Permeability | Steam escape | Measured in CFM or L/m²/s |
| Heating Source | Energy & control | Steam, oil, or electric |
| Cooling Section Length | Board stabilization | 3–6 m typical |
| Automation Features | Efficiency & quality | Servo controls, recipe storage |
Latest Technology Trends
- Hybrid Pressure Systems – Combining rolls and shoes for optimal heat transfer and uniform bonding.
- Advanced Belt Materials – Higher wear resistance, better drying performance, and improved board flatness.
- Servo‑Controlled Pressure & Heat Zones – Automatic adjustment for different grades and speeds.
- Integrated Warp Control – Sensors and software adjust heat/moisture in real time.
- Quick Grade Change Designs – Short double facers with reduced waste during order changes.
- Energy Efficiency Upgrades – Insulated hot plates, optimized steam traps, and heat recovery.
- Machine Control Centers (MCC) – Centralized monitoring, diagnostics, and maintenance scheduling.
- Self‑Cleaning Hot Plates – Height‑adjustable loading systems and large access doors for easier cleaning.
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