Sheet-fed lithographic printing, often referred to as “sheet-fed litho printing” or simply “litho printing,” is a widely used commercial printing process that involves transferring ink from a printing plate to a printing surface (typically paper or other materials) in individual sheets. This process is distinct from web offset printing, where continuous rolls of paper are used.
Here’s a breakdown of the key components and steps involved in sheet-fed litho printing:
1. Printing Plate Preparation:
- A lithographic printing plate is created for each color used in the final print. These plates are usually made of aluminum or a similar material.
- The image areas on the plate are chemically treated to attract ink, while the non-image areas repel ink.
2. Ink Application:
- Ink is applied to the printing plate, typically using a series of rollers. The ink adheres to the treated (image) areas of the plate.
3. Printing Process:
- The paper or sheet material to be printed on is fed into the printing press one sheet at a time.
- As the sheet passes through the press, it comes into contact with the inked printing plate.
- The ink is transferred from the plate to the surface of the paper, creating the desired image or text.
4. Colour Separation:
- In multi-colour printing, each colour requires a separate printing plate and pass through the press.
- The different colours are carefully aligned so that they overlap correctly, resulting in a full-colour image.
5. Drying and Finishing:
- After the ink is applied, it needs to dry before further processing. This can be done through various methods, including air drying and heat drying.
- Once the ink is dry, the printed sheets may undergo additional finishing processes like cutting, folding, binding, or coating.
Sheet-fed litho printing is favoured for its ability to produce high-quality prints with precise colour control. It is commonly used for a wide range of printed materials, including brochures, catalogs, posters, packaging, and stationery. This printing method is well-suited for short to medium print runs and allows for customisation on a per-sheet basis, making it versatile for various print jobs.
