কোম্পানির খবর Main steps in corrugated cardboard production

Corrugated cardboard production is an automated and continuous process, below are the main steps for the process:
1. Preparation and preheating of raw paper
Raw paper: The raw material for corrugated cardboard is roll raw paper, which is include below three types:
Surface paper: The outermost layer of flat paper.
Inner paper: The innermost layer of flat paper.
Corrugated paper: paper that is pressed into a wavy shape in the middle.
Preheating: The base paper first passes through a preheating roller and is heated by steam. The purpose is to evaporate some water, in order to make the paper more tough, facilitate subsequent corrugated forming, and improve its affinity with adhesives.

2. Corrugated Forming (main Steps)
This is the most important step in endowing cardboard with structure and strength.
The preheated corrugated paper is compressed by a pair of corrugated rollers (toothed hot rolling rollers). Under the action of high temperature (usually 170 ℃ -180 ℃) and pressure, flat paper is pressed into a continuous wave shape - it called"corrugated".
The shape of the corrugations (corrugations), such as A corrugations, B corrugations, C corrugations, E corrugations, etc., is determined by the tooth profile of this pair of corrugating rollers.
3. Coating and bonding (single facer machine operation)
The corrugated top after molding is coated with adhesive.
After gluing, the corrugated paper is immediately combined with a surface paper, and under the action of high-temperature corrugated rollers and pressure rollers, it is preliminarily bonded into single-facer corrugated cardboard.
The equipment that completes this step is called a single facer machine, which is the core unit of the production line. For three-layer cardboard, this step produces single-sided cardboard with one side bonded together; For five or seven layer cardboard, we need multiple single facer machine.
4. Bridge type conveying and dual preheating
Single facer corrugated cardboard is transported to the next stage through an overhead conveyor belt (bridge). The function of the bridge is buffer and store, coordinate the speed of the front and back process, and make the cardboard to naturally evaporate some moisture and preliminarily form.
5. Secondary coating and multi-layer composite (double facer machine operation)
The corrugated top on the other side of the single-sided corrugated cardboard is coated with adhesive.
Then combine it with inner paper (for three-layer boards) or another single facer cardboard (for five layer and seven layer boards) in a double facer machine.
The double facer machine is comprised of a series of heating plates and heavy conveyor belts. Under the high temperature, high pressure and appropriate residence time, starch glue can complete gelatinization, gel and curing, so that each layer can be firmly bonded to form the final multi-layer corrugated board structure.
6. Drying, cooling, and shaping
The cardboard coming out of the double facer machine has high temperature, high humidity, and is relatively soft.
Drying: The cardboard enters the drying section, further evaporating moisture to thoroughly cure the adhesive.
Cooling: The cardboard pass through a cooling section (a set of cooling rollers and fans) to lower the temperature, balance the moisture content, increase the strength, and become flat and stiff.
7. Vertical and horizontal cutting (dividing paper and pressing lines)
Vertical cutting: The continuous cardboard is first through a vertical cutting machine with a circular knife according to the width required by the order, and at the same time, the crease line (pressure line) is pressed out at the designated position by a pressure wheel.
Cross cutting: Then the cardboard is will through the horizontal cutting machine (computer-controlled flying knife), according to the order's requirements to cut precisely.
8. Stacking and packaging
The cut single corrugated cardboard is automatically stacked into stacks.
Stacked cardboard is usually bundled by automatic packers for storage and transportation.

Finally, some key points need reminder you:
The essence of corrugated cardboard production is a continuous process of "forming" and "bonding".
Physical Forming: Using corrugated rollers to transform flat paper into a wavy structure, providing compressive and cushioning capabilities.
Chemical bonding: By using starch adhesive in single facer and double facer machines, with the help of high temperature, high pressure, and appropriate time, the layers are firmly bonded.

A modern corrugated cardboard production line is a continuous assembly line that connects units such as raw paper preparation, single facer machine, bridge, double facer machine, drying and cooling, longitudinal and transverse cutting, stacking, etc. The speed and coordination are the key points determining production capacity and quality.