Common Classification of Printing Machinery and Printing Methods

Common Classification of Printing Machinery and Printing Methods

Table of content.

Common Classification of Printing Machinery and Printing Methods

 

Printing Machinery

Printing machinery refers to the collective term for machines and equipment used to produce printed materials.
 Its primary function is to transfer ink from the image areas of the printing plate onto the surface of the substrate.

 

 

Main Classifications

Classified by Plate Type

  • Relief printing presses

  • Planographic (offset) printing presses

  • Gravure printing presses

  • Stencil (screen) printing presses

 

 

Classified by Paper Format

  • Sheet-fed printing presses

  • Web-fed (roll-fed) printing presses

 

 

Classified by Number of Colors

  • Single-color printing presses

  • Two-color printing presses

  • Multi-color printing presses

 

 

Classified by Printing Format Size

  • Octavo presses

  • Quarto presses

  • Folio presses

  • Full-sheet presses

  • Oversize full-sheet presses

 

 

Classified by Impression Method

  • Flat-to-flat

  • Cylinder-to-flat

  • Cylinder-to-cylinder

 

 

1. Flat-to-Flat Printing Press

In flat-to-flat printing presses, both the plate mounting unit and the impression unit are flat in structure.
 During printing, the flat impression bed reciprocates around the main axis to complete sheet feeding and impression.

Printed results typically feature heavy ink coverage, with full and solid lines and strokes.

 

2. Cylinder-to-Flat Printing Press

In this type, the plate mounting unit is flat, while the impression unit is a cylindrical roller.
 During printing, the plate bed moves back and forth relative to the impression cylinder, which remains in a fixed position. The impression cylinder rotates while pressing the substrate.

This type is mainly used for printing book and magazine text pages.

 

3. Cylinder-to-Cylinder Printing Press

The structural characteristic of this press is that both the plate mounting unit and the impression unit are cylindrical rollers.
 During printing, the impression cylinder carries the substrate and rotates in the opposite direction relative to the plate cylinder while applying pressure.

4. Piezoelectric Inkjet Technology (Piezo)

Detailed Explanation Piezoelectric Inkjet Technology (Piezo) is An on-demand Inkjet Technology.

 

 

Screen Printing

 

Concept of Screen Printing

Screen printing is one of the main printing methods within stencil printing.
 The screen used in screen printing is a fine fabric made of natural silk, synthetic fibers (plastics), or metal wires. Today, plastic or metal meshes are most commonly used.

Ink is transferred or overprinted through the open mesh areas that are not covered by the stencil. Therefore, a screen printing plate is a combination of the mesh and the stencil.

 

Influencing Factors of Screen Printing

The factors that determine the characteristics of screen printing and the quality of the mesh (fabric) include:

  • Type of mesh material

  • Mesh fineness (number of warp and weft threads per centimeter)

  • Mesh thickness

  • Distance from the top of the mesh to the bottom

  • Degree of mesh opening (the percentage of open mesh area relative to the total fabric surface area)

Mesh fineness typically ranges from 10 to 200 mesh/cm, with 90–120 mesh/cm being the most commonly used.

For very complex halftone images and printing, fabrics with very high mesh fineness are required to match the resolution demands of image reproduction.
 In halftone printing, the mesh fineness (mesh/cm) is generally about 3–4 times the halftone screen ruling (lines/cm). This means that 9–16 halftone dots are contained within the surface area of a single mesh opening.

 

Principle of Screen Printing

The substrate is laid flat on the base of the printing table assembly and remains firmly positioned throughout the printing process.

Under the action of the squeegee, the ink on the screen moves like a wave. Ink beneath the ink flow passes through the mesh openings—this stage is known as the flooding stage.

During the contact stage, ink at the leading edge of the rubber squeegee passes through the mesh again and comes into contact with the substrate.
 In the adhesion stage, the trailing edge of the squeegee ensures adhesion between the ink, the stencil, and the substrate.

During the release stage, the tension of the screen pulls the ink filaments out of the ink film. Residual ink remains in the mesh openings, while a uniform ink layer is deposited onto the substrate.

 

 

Screen Printing Process

  1. Apply ink onto the printing screen

  2. Place the substrate beneath the screen and use a squeegee with controlled pressure to force the ink through the mesh openings

  3. Transfer the ink onto the substrate to form the printed image

 

Screen Printing Methods

1. Flat-to-Flat Method (Flatbed Method)

Both the screen plate and the substrate are flat. Ink is forced through the mesh openings by the squeegee and transferred onto the substrate.

2. Flat-to-Cylinder Method and Direct Object Printing

a. A flat screen plate is used while a rotating cylinder carries the substrate. The screen plate and impression cylinder move synchronously in the same direction, and the squeegee forces ink through the mesh onto the substrate.

b. The screen plate and squeegee are adapted to the shape of the substrate (curved, arched, or cylindrical). The screen plate and substrate move synchronously in one direction, while the squeegee remains stationary.
 This method is used for printing cans, spherical objects, and other curved surfaces.

3. Cylinder-to-Cylinder Method (Rotary Screen Printing)

The printing screen is cylindrical. The screen, substrate, and impression cylinder move synchronously, and ink is transferred from the cylindrical screen to the substrate.

 

 

Application Fields of Screen Printing

  1. Textiles and textile materials

  2. T-shirt printing

  3. Toy printing

  4. Housings of electrical appliances such as televisions and radios

  5. Automotive dashboards and measuring instruments

  6. Packaging (plastic bags)

  7. Printed circuit boards (PCBs)

  8. Large-format advertising and posters

 

Letterpress Printing

 

Characteristics of Letterpress Printing

The common characteristic of letterpress printing is that the printing areas on the plate are raised above the non-printing areas.
 All printing elements are at the same height (the image area). An even layer of ink is applied by ink rollers, and the ink is then transferred onto the substrate.

 

Principle of Letterpress Printing

  • Ink rollers pass over the surface of the printing plate, allowing ink to adhere to the raised image areas

  • The substrate comes into contact with the inked printing plate

  • Under pressure, the ink on the image areas is transferred onto the surface of the substrate

 

Letterpress Printing Process

  1. Ink is applied to the printing areas by ink rollers

  2. Impression brings the plate into contact with the substrate

  3. Ink is transferred to the substrate

 

Application Categories of Letterpress Printing

  1. Book and publication printing

  2. Flexographic printing

  3. Offset letterpress printing

 

 

1. Book and Publication Printing

In book and publication printing, common printing methods include:
 a. Flat-to-flat (flatbed printing)
 b. Cylinder-to-flat (flatbed cylinder printing)
 c. Cylinder-to-cylinder (rotary printing)

Large-format, high-quality printing can only be achieved using cylinder-to-flat printing presses, but the production output is relatively low.

A key feature of letterpress printing is the diversity of plate types and compositions, including hot-metal plates, original movable type plates, and duplicated letterpress plates. These plates are made from materials such as lead alloys, zinc, copper, photosensitive resins, and plastics. In artistic printing, wood and linoleum plates are also used.

Plates used in flatbed and flatbed cylinder presses are generally composed of several rigid, flat, and fixed individual components.
 Semi-cylindrical cast lead plates (lead plates), also known as wash-up or molded plates, and flexible plastic plates are suitable for rotary printing.

 

 

2. Flexographic Printing

The main characteristic of flexographic printing is the use of relatively soft printing plates compared to those used in book printing, enabling it to meet special ink transfer requirements.

By using flexible plates and suitable low-viscosity inks, flexographic printing can be applied to both absorbent and non-absorbent substrates.

In flexographic printing, low-viscosity ink is transferred to the printing plate via a roller with evenly distributed ink cells, known as the anilox roller.
 Anilox rollers are typically ceramic or hard chrome–plated metal rollers, with screen rulings ranging from 200 to 600 lines/cm.

Ink is transferred onto the substrate under the pressure of the impression cylinder.
 During printing, a doctor blade mounted on the anilox roller, together with the ink supply system, ensures that the ink cells are uniformly filled, providing stable and consistent ink transfer.

 

3. Offset Letterpress Printing

In offset letterpress printing, the image on the rigid and durable letterpress plate is first transferred to an intermediate carrier (a rubber-blanket-covered cylinder) and then transferred onto the paper—this is known as indirect letterpress printing.

Similar to offset lithography, offset letterpress printing is therefore also referred to as offset letterpress technology.

 

 

Gravure Printing


Principle of Gravure Printing

The distinctive feature of gravure printing is that the image areas are engraved below the surface of the printing cylinder, while the non-image areas remain on the same original plane.

Before printing, the entire plate (including both image and non-image areas) is flooded with ink. A doctor blade then scrapes ink off the non-image surface areas, leaving ink only in the engraved cells.
 Under high printing pressure and due to the adhesion between the substrate and the ink, the ink is transferred from the engraved cells onto the substrate.

In gravure screening, the image areas are divided into basic printing units—cells, while the non-printing units are cell walls. The cell walls help guide the doctor blade to remove excess ink.
 After doctoring, ink remains only in the cells. If ink remains on the cell walls, plate smearing may occur. If the doctor blade is locally damaged, doctor blade streaking or breakage may result.

 

 

Gravure Printing Process

  1. Flood the entire plate surface with ink

  2. Use a doctor blade system to remove ink from the flat (non-image) areas, leaving ink only in the recessed image areas

  3. Place a highly absorbent substrate onto the plate and apply high pressure

  4. Ink from the engraved image areas is transferred to the substrate to form the printed product

 

 

Characteristics of Gravure Printing

During operation, the gravure cylinder is immersed in the ink fountain, allowing the engraved cells to be fully filled with ink.
 A doctor blade scrapes off excess ink so that ink remains only in the cells, with no ink on the cell walls.

After doctoring, dynamic ink back-pressure is generated. This pressure mainly depends on the doctor blade contact angle, printing speed, and ink viscosity.
 In modern printing, high-performance gravure presses and doctor blades with larger contact angles are commonly used.

Because multicolor gravure printing adopts a wet-on-wet printing process similar to offset printing, a drying unit after each printing station is essential.
 Low-viscosity gravure inks cannot be used; typical ink viscosity is approximately 0.1 Pa·s.

 

 

Basic Features of Gravure Printing

  1. Text and fine lines may exhibit serrated edges

  2. Excellent image reproduction quality; due to varying cell depths (ink volumes), a near continuous-tone effect can be achieved

  3. In variable-depth gravure printing, square cells of the same size can reproduce the full tonal range; in highlight areas, cells are often engraved deeper

  4. In variable-depth and variable-area gravure printing, dots of different sizes and color saturation levels can be produced

 

Main Applications of Gravure Printing

Typical gravure products are large-volume, high-quality printed materials, such as:

a. Journals, magazines, and mail-order catalogs
 b. Plastic films
 c. Metal foils
 d. Transparent films and shopping bags
 e. Security paper, postage stamps, and financial documents

 

 

Offset Printing


Characteristics of Offset Printing Plates

In offset printing, the image areas and non-image areas are almost on the same plane, with no obvious height difference between them.

 

Principle of Offset Printing

  • Dampening rollers supply fountain solution to the printing plate, allowing the non-image areas to absorb moisture

  • Inking rollers supply ink to the plate, causing the image areas to attract and retain ink

  • Under applied pressure, the ink from the image areas is transferred via a rubber blanket cylinder onto the surface of the substrate

 

Offset Printing Methods

(Offset printing can be classified according to press structure and feeding method, such as sheet-fed offset and web offset.)

 

Offset Printing Process

  1. Dampening solution is applied to the printing plate

  2. Ink is applied to the image areas of the plate

  3. The inked image is transferred to the rubber blanket

  4. The ink is transferred from the blanket to the substrate, producing the printed image

 

Printing Results of Offset Printing

Offset printing delivers high image quality, smooth tonal gradation, and accurate color reproduction, making it suitable for high-volume commercial printing such as books, magazines, brochures, and packaging materials.

 

Comparison of Offset Printing vs. Letterpress, Gravure, Screen Printing, and Inkjet Printing

 

1. Offset Printing vs. Other Printing Methods

Offset Printing

Offset printing is a planographic printing process in which the image and non-image areas are on the same plane. Printing relies on the chemical principle that oil and water repel each other. Ink is first transferred from the plate to a rubber blanket, and then onto the substrate.

Key characteristics:

  • High image quality and smooth tonal gradation

  • Excellent color consistency for long print runs

  • Requires printing plates and complex setup

  • Economical only for medium to large production volumes

 

 

2. Letterpress Printing (Relief Printing)

In letterpress printing, the image areas are raised above the non-image areas. Ink is applied directly to the raised surface and transferred to the substrate under pressure.

Characteristics:

  • Strong ink impression and tactile effect

  • Simple printing principle

  • Limited image quality for photographs and gradients

  • Largely replaced by offset and digital printing in modern applications

Typical applications: specialty books, artistic printing, flexographic packaging

 

 

3. Gravure Printing

Gravure printing uses engraved cells recessed into a cylinder to hold ink. Ink is transferred from these cells to the substrate under high pressure.

Characteristics:

  • Outstanding image reproduction and near continuous-tone quality

  • Extremely stable color consistency in long runs

  • Very high plate-making cost and long setup time

  • Best suited for ultra-large-volume production

Typical applications: magazines, packaging films, foils, security printing

 

 

4. Screen Printing

Screen printing is a stencil-based printing method where ink is forced through a mesh screen onto the substrate.

Characteristics:

  • Very thick ink layers and strong color saturation

  • Can print on almost any substrate, including curved and irregular surfaces

  • Lower resolution compared to offset or gravure

  • Slower production speed

Typical applications: textiles, T-shirts, signage, electronics, industrial components

 

 

5. Inkjet Printing (Digital Printing)

Inkjet printing is a non-impact, digital printing technology in which ink droplets are precisely deposited onto the substrate without physical contact.

Characteristics:

  • No printing plates required

  • Image data is printed directly from digital files

  • Supports variable data and on-demand printing

  • Suitable for both small-batch and customized production

 

 

Summary: Advantages of Inkjet Printing

Compared with traditional printing methods, inkjet printing offers several decisive advantages:

  1. No Plate Making Required
     Eliminates plate costs, setup time, and material waste, making it ideal for short runs and rapid production.

  2. High Flexibility and Customization
     Supports variable data printing, personalization, and quick design changes without stopping production.

  3. Fast Time-to-Market
     Digital workflows significantly reduce preparation time, enabling faster response to market demands.

  4. Cost-Effective for Small and Medium Volumes
     Particularly economical for short runs where traditional printing becomes expensive.

  5. Wide Substrate Compatibility
     Can print on paper, plastics, films, textiles, ceramics, glass, and even three-dimensional objects.

  6. Environmentally Friendly
     Lower ink waste, reduced chemical usage, and fewer consumables compared to plate-based processes.

  7. Scalable from Desktop to Industrial Production
     Inkjet technology is applicable across office printing, commercial printing, and high-speed industrial manufacturing.

 

 

Conclusion

While offset, gravure, letterpress, and screen printing remain essential for specific high-volume or specialty applications, inkjet printing stands out as the most flexible, digital, and future-oriented printing technology, especially in an era driven by customization, speed, and sustainability.

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