As soon as the issue of insufficient flute height in corrugated board is mentioned, many people immediately assume that the board has collapsed. In fact, this phenomenon is distinct from actual collapse; therefore, it is advisable to conduct a thorough investigation from several aspects—including raw materials, the single-facer, the top bridge, the gluing machine, the conveyor belt, the pressure rollers, and the downstream section of the corrugating line—to identify the root cause and implement appropriate corrective measures.

(1) Raw Materials

The corrugated paper used must meet national standards. For example, 105-gram corrugated paper must be produced by a base-paper manufacturer that complies with the Grade B national standard; Grade C paper does not provide sufficient ring crush resistance and is prone to corrugation collapse.

Quality control at every cardboard box manufacturing plant must be rigorously implemented: the company first establishes enterprise standards and then requires suppliers to comply with these standards.

(2) Single-Flute Machine

1) Temperature.

Is the corrugating roll temperature adequate? When the corrugating roll temperature is insufficient, the resulting flute height will be inadequate. Typically, a well-managed company will assign a dedicated person to monitor the temperature along the entire production line (it is recommended that the boiler operator perform this task). If a temperature issue is detected, the on-duty supervisor and the machine operator must be notified immediately, the maintenance technician should be informed for repair, and all preheating cylinders should be inspected and overhauled monthly.

2) There is dirt on the surface of the corrugating roll.

Before starting the machine each day, the corrugating rolls are preheated and then wiped with light machine oil to remove any adhesive residue and debris.

3) Adjusting the clearances between the rollers is critically important in production.

The gap between the sizing roller and the corrugating roll is typically set after the corrugating roll has been preheated for 30 minutes, allowing it to expand to its maximum extent. The gap is then adjusted to match the thickness of the lightest-weight corrugating medium produced by our company, and must be checked before each day’s start-up.

The gap between the corrugating roll and the pressure roll is generally determined based on production conditions, with the requirement that proper contact be maintained.

The gap between the upper and lower corrugating rolls is critically important; if it is not properly adjusted, the resulting corrugated profile will be irregular, and thickness deficiencies are most likely to occur.

4) Degree of wear on the corrugating rolls.

Monitor the production status of corrugating rolls at all times to determine whether they need to be replaced. It is recommended to use tungsten carbide corrugating rolls, as their superior wear resistance can reduce production costs and, under stable operating conditions, typically allow the investment to be recouped within 6 to 8 months.

(3) Pedestrian Overpass

Do not allow excessive accumulation of single-wall corrugated paper on the overhead conveyor; excessive tension can cause the paper to sag and fail, resulting in insufficient cardboard thickness. It is recommended to install a computerized production management system, which can effectively prevent such incidents. However, many domestic manufacturers already have such systems yet fail to utilize them—what a waste!

When selecting a manufacturer for the paper-overpass installation, exercise careful consideration to prevent production from being adversely affected by excessive suction on the overpass; excessive suction can easily cause the corrugated board to collapse. It is essential to monitor the rotation of each shaft and regularly check the parallelism of each shaft, maintaining constant vigilance at all times.

(4)糊机

1) If the pressure roller on the sizing roller is pressing too low, adjust the gap between the pressure rollers—typically by lowering it by 2–3 millimeters.

2) Pay attention to the radial and axial runout of the pressure roller; it must not be elliptical.

3) Selecting the pressure-rolling bar involves considerable expertise. Increasingly, factories are opting to use pressure-rolling bars as nip rollers, which represents a significant innovation; however, in many cases, operators still need to fine-tune the pressure to the optimal setting.

4) The amount of adhesive applied should not be excessive, as this can cause deformation of the corrugated flutes. A higher adhesive application does not necessarily result in better bonding; therefore, careful attention must be paid to the adhesive formulation and manufacturing process.

(5) Canvas Belt

The canvas belt should be lightly cleaned once daily at a set time, and undergo a thorough cleaning once a week. Typically, the belt is soaked in water for a period to soften it, after which it is scrubbed with a wire brush. Under no circumstances should you rush the process in an attempt to save time, as this can lead to accumulated grime that ultimately requires far more time to clean up later.

To produce high-quality products, the canvas belt must have excellent breathability. After a certain period of use, it must be replaced; compromising on this due to short-term cost savings can lead to warping of the cardboard, which would ultimately outweigh any savings.

(6) Pressure Roller

1) A reasonable number of pressure rollers must be used. The number of pressure rollers employed should vary with the season and be adjusted promptly based on actual conditions.

2) The radial and axial runout of each pressure roller must be controlled within 2 mils; otherwise, an elliptically shaped pressure roller will crush the corrugated flutes, resulting in insufficient flute height.

3) The gap between the pressure roller and the heating plate must be properly adjusted, with sufficient fine-tuning capability, to accommodate variations in corrugation height.

4) It is recommended that carton manufacturers replace pressure rollers with heated press plates, provided that the operators’ skill level meets the requirements for operating automated equipment.

(7) Rear Section of the Tile Line

The inlet and outlet of the cross-cutting blade must be fitted with appropriately graded sun wheels, typically with a Shore hardness of 55 to 60, to prevent crushing the cardboard.