OFFSET PRINTING- HOW DOES IT WORK?

Offset printing is the most commonly used printing method today. Over 40% of all print jobs are carried out using offset printing.

WHAT IS OFFSET PRINTING?

Offset printing (also called Offset Lithography), is a printing technique in which the images on a metal plate are transferred to a rubber blanket, then to the printing surface. The printing surface, usually paper, does not come into direct contact with the metal plates. This help prolongs the plate life. Instead, the flexible rubber conforms readily to the print media surface, allowing the process to be used effectively on rough-surfaced media such as canvas, cloth or wood.

HOW DOES IT WORK?

Offset printing works in a simple manner. It uses three cylinders to transfer the image onto the substrate. 

The first cylinder: Plate Cylinder

The second cylinder: Rubber Blanket Cylinder

The third cylinder: Impression Cylinder

The first cylinder is mounted with the printing plate. The image on the printing plate is ‘right’ reading or written with the right side up. The first cylinder is inked and the image transferred or offset onto the second cylinder, which is mounted with a rubber blanket. The image on the second cylinder is thus reversed or becomes ‘wrong’ reading. Finally the image is transferred from the blanket cylinder onto the third cylinder or the substrate. The substrate is mounted on the third cylinder also known as the impression cylinder. The image once again is reversed and becomes ‘right’ reading or right side up in the final printed version.

CLASSIFICATION?

There are two types of offset printing machines in common use for publication today: Sheet-fed offset printing and Web offset printing

In sheet-fed offset printing, individual pages of paper are fed into the machine. The pages can be pre-cut to the final publication size or trimmed after printing. Sheet-fed offset printing is popular for small and medium-sized fixed jobs such as limited-edition books

Sheet-fed offset printing machine

Hanoi Printing’s most noticeable sheet-fed printing machines are the Mitsubishi Diamond 3FR-12 colors  and the Mitsubishi 3FR-8 colors which offer the maximum size of 72 x 102 cm for color printing. 

In web offset printing, larger, higher-speed machines are used. These are fed with large rolls of paper and the individual pages are separated and trimmed afterwards. Web offset printing is more cost-effective for high-volume publications whose content changes often, such as metropolitan newspapers.

Web-offset printing machine

For this type of printer, we own 2 City Line Web Presses originated from Germany which provide capacity to 45,000 sheets/hours. 

PROS AND CONS?

Pros?

Offset printing is usually used for high-volume printing such as with magazines, books, newspapers, brochures, and stationery. While it does add some steps in the process, for massive orders, it makes financial sense for several reasons.

The ink, which fades and then runs out in direct printing methods, is actually controllable with offset printing. The operator can twist some screw keys to adjust the amount of ink flow on the fountain roller. This minimizes the creation of wasted prints with insufficient contrast. The printing plates themselves are easy and fast to make with today’s technology. And the plates each have the potential to run a million impressions or more.

It costs less to produce high quality printing when it is done with offset printing methods. Additionally, the image quality is consistently good as the rubber blanket, on the printing plate, fits itself to the texture of the printing surface, leaving a clean and detailed image every time.

Cons?

The disadvantages are fewer, but they include the tediousness and cost associated with the production of the printing plates and setup. The printing plates are made of anodized aluminum, making them vulnerable to chemical oxidation, so they need some extra care and maintenance. 

But all in all, the advantages outweigh the disadvantages with offset printing, at least when it comes to high-volume printing jobs.


Some pictures of our printed products: