wiadomości o firmie How much do you know about the working principle of cardboard printing machines?

The core working principle of cardboard printing machines, especially modern mainstream flexographic printing machines, can be summarized as follows: through a set of printing units consisting of mesh rollers, plate cylinders, and impression cylinders, water-based ink is transferred from the ink tank to the substrate (corrugated cardboard), and finally, after drying and line processing, the cardboard box is printed and formed.

Below, we will break it down into several core systems and workflows for a detailed analysis.

1.Core Printing System (Taking Flexographic Printing as an Example)
This is the "heart" of the cardboard printing machine, which works based on letterpress printing.
1.)Ink supply system ink tank: a container for storing water-based ink.
Mesh roller: This is a key component for quantitative ink supply. It is a metal roller with countless tiny holes (ink holes) of uniform size, shape, and depth engraved on its surface. The number of lines on the mesh roller (the number of ink holes per inch) determines the size of the ink transfer, thereby affecting the color difference and precision of printing.
Working principle: The mesh roller rotates in the ink tank, and the ink holes on its surface will dip and carry a certain amount of ink.
2) Ink scraping system
Function: Scrape off excess ink on the surface of the mesh roller, leaving only the ink inside the ink hole.
Type:
Reverse scraper system: A flexible steel scraper contacts the surface of the mesh roller in reverse at a certain angle and pressure, accurately scraping off excess ink. This is currently the mainstream configuration for high-precision printing.
Rubber roller ink scraping system: Using a rubber roller in contact with a mesh roller, excess ink is squeezed out by pressure. The structure is simple, but the accuracy is low, and it is mostly used for low-speed or low requirement printing.
3)Ink transfer and printing system
Plate cylinder: A cylinder equipped with a flexible printing plate (usually a photosensitive resin plate). The graphic and textual parts on the printing plate are raised (higher than the non graphic and textual parts).
Impression cylinder: A smooth and hard surface cylinder located on the other side of the cardboard, providing back pressure.
Core Transfer Process (Three Steps):
Ink is transferred from the anilox roller to the printing plate: the anilox roller carrying a certain amount of ink rotates in contact with the flexible printing plate on the plate cylinder. Due to the raised graphic and textual parts of the printing plate, it will come into contact with the mesh roller, thereby transferring the ink in the ink hole to the raised graphic and textual parts of the printing plate.
Cardboard enters the printing unit: Corrugated cardboard is transported between the plate cylinder and the impression cylinder.
Ink is transferred from the printing plate to the cardboard: Under the pressure of the printing cylinder, the graphic and textual parts on the printing plate come into contact with the surface of the cardboard, and the ink is pressed onto the cardboard to complete a color printing.

2.Whole machine workflow (series multi-color printing)
A standard cardboard box printing slotting machine typically includes multiple printing units as described above to achieve multi-color printing.
Process steps:
Paper Delivery Department
The stacked corrugated cardboard is smoothly and accurately fed into the machine one by one by an automatic paper feeder. Use vacuum adsorption or friction pushing to ensure that only one cardboard is fed in each time.
Printing Department
The cardboard passes through multiple printing units in sequence (such as a 4-color machine with 4 units). Each unit is responsible for printing one color (CMYK or spot color).
The order of units is usually: first color ->second color ->third color ->fourth color.
Each unit has an independent ink supply, ink scraping, and printing system that can adjust color and pressure independently.
Drying department
Between each color printing or after completing all printing, the cardboard will go through a drying system.
Drying method:
Hot air drying: The most common method is to quickly evaporate the moisture in water-based ink by blowing hot air through a hot air nozzle.
Infrared drying/UV drying: used for special inks or situations that require rapid curing.
Function: To prevent wet ink from getting dirty during subsequent printing or transportation processes.
Slotting and die-cutting department
This is the key step in processing printed cardboard into the shape of a cardboard box.
Slotting: Use a top and bottom matching slotting wheel to cut vertical gaps in the cardboard, forming creases in the cardboard box.
Crimping: Use a crimping wheel to press indentations on the cardboard so that the cardboard box can bend into the predetermined shape.
Die cutting: If the cardboard box requires an irregular structure (such as handle holes, windows, etc.), a pre made die will be used to punch out the shape through pressure.
Folding and Counting Stacking Section
Fold the processed cardboard along the pressure line, count and stack it into a stack for easy packaging and transportation.

3、 Key technologies and principles
Dot printing: Even with solid color blocks, modern cardboard printing uses dots to express layers. By controlling the size and density of the dots, different colors and gradient effects can be mixed, similar to the principle of offset printing.
Pre printing and post printing:
Post printing: The above principle describes the most common form of post printing, which involves printing directly onto the already formed corrugated cardboard. The advantages are flexibility and fast delivery, but the printing accuracy is affected by the corrugated pattern.
Pre print: First, high-precision printing is performed on a smooth surface paper (commonly known as gravure printing), and then the printed surface paper is laminated with corrugated core paper. The advantage is that the printing quality is extremely high, suitable for large quantities of high-end cardboard boxes.
Alignment principle: The machine detects the edges of the cardboard or pre printed marks (marking lines) through photoelectric sensors, and fine tunes the position of subsequent printing or processing units to ensure accurate alignment of various color patterns and slot positions.
summary

The cardboard printing machine is a complex system that integrates mechanical transmission, fluid control (ink), chemical drying (ink curing), and automation control. Its core working principle always revolves around the two basic points of quantitative ink transfer by the mesh roller and graphic transfer by letterpress printing. Through precise mechanical structure and automation control, it efficiently prints design patterns onto corrugated cardboard and completes the forming processes such as slotting and die-cutting in one step, ultimately producing various packaging boxes that we see in our daily lives.