Double Backer Machine: Technical Guide for Corrugated Board Production

The double backer is where corrugated board is completed. Understanding this machine is essential for quality board production.

What is a Double Backer?

The double backer (also called double facer) is the corrugating line section that

Receives single-face webs from bridge

Applies adhesive to exposed flute tips

Bonds the second (outer) liner

Cures adhesive with heat and pressure

Outputs finished corrugated board

Double Backer Components

1. Glue Machine

Applies adhesive to single-face web(s)

Metering roll controls glue amount

Doctor blade maintains film thickness

Glue dam prevents overflow

2. Liner Preheater

Heats outer liner before bonding

Removes excess moisture

Improves bond formation

Usually steam-heated cylinders

3. Hot Plate Section

Series of heated plates (typically 20-40)

Steam or thermal oil heated

Temperature: 150-180°C (traditional)

Cures adhesive through heat transfer

4. Cooling Section

Reduces board temperature

Stabilizes adhesive bond

Prevents moisture issues

5. Pull Section

Weighted belt or roll system

Provides tension and pressure

Transports board through machine

Types of Double Backers

Belt-Over-Hot-Plate

Most common design

Belt presses board against hot plates

Good heat transfer

Belt maintenance required

Ballast Weight System

Uses weighted rollers

Lower maintenance

Popular in modern lines

Cassette Hot Plate

Quick-change hot plate sections

Reduced downtime for maintenance

Premium pricing

Key Specifications

Working Width: Match to single facer (1400-2800mm)

Speed: Match to line speed (100-400 m/min)

Hot Plate Length: 10-25 meters typical

Temperature Range: 80-180°C

Heating System: Steam or thermal oil

Boiler-Free Double Backer

Xuegong's room-temperature technology

Operating temperature: <100°C

Works with instant-setting adhesive

No steam boiler required

60% energy savings

Same quality results

Optimization Tips

Temperature Settings

Start from entry end

Gradually decrease toward exit

Adjust for paper weight and speed

Monitor board moisture at exit

Belt Tension

Too tight: marks on board

Too loose: poor bond, bubbles

Check regularly and adjust

Speed vs. Quality

Higher speed needs higher temperature

Or longer hot plate section

Balance based on adhesive gel point

Common Issues

Blisters/Bubbles

Too much adhesive

Insufficient heat

Paper moisture too high

Delamination

Insufficient adhesive

Temperature too low

Speed too high for conditions

Board Curl/Warp

Uneven moisture in liners

Temperature imbalance

Check preheater settings

Contact Xuegong for double backer technical support and boiler-free solutions.