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.