The core working principle of printing press

The core working principle of a printing press is "graphic and textual reproduction": transferring ink (or other printing materials) to a substrate (paper, plastic, fabric, etc.) through a specific method, accurately reproducing the text and images of the original manuscript. The transfer methods of different types of printing machines vary greatly, but the core process can be summarized into four key steps: "original manuscript → printing plate → ink → substrate". The following is a breakdown of the working principle of mainstream printing machines:
1、 Core universal process (basic logic of all printing machines)
Original manuscript processing: Digitize the text and images that need to be printed (such as scans and design files), and use plate making technology to create a "printing plate" (equivalent to a "template");
Ink transfer: The ink transfer system of the printing machine evenly applies ink to the "graphic and textual parts" of the printing plate (non graphic and textual parts do not stick to ink);
Substrate transportation: The substrate (paper, etc.) is accurately and continuously transported to the printing station through a paper feeding mechanism; Pressure transfer: The ink on the printing plate is transferred to the surface of the substrate through the pressure of the cylinder, completing the copying of graphics and text;
Post processing: The printed substrate undergoes drying (ink curing), cutting, binding, and other processes to become the final product.
2、 Mainstream printing machine types and specific working principles
1. Offset Printing (most commonly used, such as books, posters, packaging)
Core principle: Indirect transfer (ink is first transferred to the rubber blanket, and then transferred to the substrate), utilizing the characteristic of "oil and water immiscibility".
Key steps:
Printing plates (metal plates, such as PS plates) are divided into "graphic and textual parts" (hydrophilic and hydrophobic) and "non graphic and textual parts" (hydrophilic and hydrophobic);
The water delivery system applies water to the non graphic parts of the printing plate to form a water film (to prevent ink from sticking);
The ink delivery system applies ink to the graphic and textual parts of the printing plate, and the ink only adsorbs on the oleophilic graphic and textual areas;
Press the printing plate cylinder and rubber blanket cylinder to transfer ink onto the rubber blanket;
The rubber blanket cylinder and impression cylinder squeeze and transfer ink from the rubber blanket to the paper (indirect transfer can avoid direct wear of the printing plate on the paper and improve printing quality).
Features: High printing accuracy, uniform ink, suitable for large-scale production, and is the mainstream of commercial printing.
2. Digital Printing Machine (such as personalized printing, short form printing)
Core principle: Printless printing, which directly transfers digital graphics and text to the substrate through "inkjet" or "electrostatic imaging" methods without the need to create physical printing plates.
Classification types and principles:
Inkjet printers (such as Epson and Canon digital printers):
Digital graphic signal controls the nozzle to directly spray tiny ink droplets (with an accuracy of over 1200dpi) onto the surface of the substrate. After the ink solidifies (UV curing or natural drying), it forms graphics and text;
Features: No need for plate making, high flexibility (can be customized individually), suitable for short form printing (such as photo albums and manuals). Electrostatic imaging (such as HP Indigo, Xerox digital printers):
Similar to the principle of a photocopier: charging the photosensitive drum → laser scanning to form an electrostatic latent image → adsorption of toner (graphic part) → transfer of toner to paper → high-temperature and high-pressure solidification of toner.
Features: Quick order change, strong personalization, suitable for small batch and short cycle printing.
3. Gravure Printing Machine (such as packaging, plastic film, wallpaper)
Core principle: The printing plate is intaglio (concave in the graphic and textual parts, flat in the non graphic and textual parts), and is transferred using "ink filling concave".
Key steps:
Carving concave graphics and text on the surface of the printing plate cylinder (the depth of the concave corresponds to the thickness of the ink, determining the depth of the printed color);
The ink delivery system applies ink to the surface of the printing plate (including concave and non concave parts);
The ink scraper removes ink from non recessed areas, leaving only the ink inside the recessed graphics and text;
The printing plate cylinder and the impression cylinder squeeze and transfer the ink in the depression to the substrate (such as plastic film, paper).
Features: Thick ink layer, bright colors, wear-resistant, suitable for large-scale packaging printing (such as beverage bottle labels, food packaging).
4. Letterpress Printing (traditional process, now mostly used for special printing)
Core principle: The printing plate is a relief plate (with raised graphic and textual parts and flat non graphic and textual parts), similar to a "stamp". Key steps:
The graphic and textual parts of the printing plate are raised, and the non graphic and textual parts are lower than the graphic and textual plane; The ink delivery system applies ink to the raised graphic and textual parts;
The substrate is transported to the bottom of the printing plate, and the ink in the protruding part is directly transferred to the substrate through the pressure of the cylinder.
Features: Clear lines, uniform pressure, now mostly used for special printing (such as bills, envelopes, hot stamping).
5. Screen Printing Machine (such as T-shirts, posters, circuit boards)
Core principle: Using "wire mesh hollowing" to filter ink, only allowing the ink to transfer to the substrate through the mesh holes in the graphic and textual parts.
Key steps:
On the screen plate (nylon mesh or metal mesh), the mesh holes of the graphic and textual parts are not blocked, while the non graphic and textual parts are blocked by photosensitive adhesive;
Pour the ink onto the screen plate, use a scraper to scrape and press the ink, and the ink penetrates through the hollow mesh to the substrate below (such as fabric, metal plate);
After the ink dries, it forms graphics and text.
Features: It can be printed on irregular substrates such as curved surfaces and three-dimensional parts, with thick ink layer and strong adhesion, suitable for printing on special materials.
3、 The role of key core components
Cylinder: The core transmission and pressure component, divided into plate cylinder (carrying the printing plate), blanket cylinder (for offset printing), and impression cylinder (providing pressure to ensure ink transfer);
Ink delivery system: composed of ink hopper, ink roller, ink scraper, etc., responsible for evenly and stably delivering ink to the printing plate;
Paper feeding mechanism: Ensure accurate and continuous conveyance of the substrate (paper), avoiding paper jams or misalignment;
Drying system: By using hot air, ultraviolet, infrared and other methods, the ink is quickly cured (especially suitable for digital printing and gravure printing).
summary
The core difference between different printing machines lies in the "plate form" and "ink transfer method":
Offset printing: indirect transfer (rubber blanket)+oil-water separation;
Digital: Direct transfer without printing (inkjet/electrostatic);
Concave printing: Concave printing plate+ink filling;
Embossing: raised printing plate+direct embossing;
Wire mesh: hollow screen with ink penetration.
The choice of printing machine depends on the substrate material, printing batch size, precision requirements, and cost budget.