Offset Printing Technology

A Comprehensive Overview of Offset printing Technology

The offset printing is the conventional and most used printing process by businesses and organizations for high volumes of best quality with low-cost prints.  Other common names of offset printings are the offset lithography or the litho-offset printing. It is a primary technique for mass printing images on the aluminum plates transferred over the rubber rollers to print those images. The litho-offset printing is used in commercial printing for bulks of magazines, books, manuals, flyers, letterheads, banners, labels, and packaging. The fixed cost is involved in setting up each printing job; thus, the per print cost is higher in fewer prints than the prints’ bundles. For instance, each print cost in a 250-prints will be higher than each piece’s cost in a 10,000-prints.

THE OFFSET PRINTINGS PROCESS

The modern offset printing machines consist of fixed aluminum plates, water phobic inks, and three rolling cylinders.

  1. Plate cylinder: zinc, aluminum, or a mixture of metals are fixed to these plates
  2. Blanket cylinder: covered by a rubber sheet
  3. Impression cylinder: it presses the paper on the blanket sheet to transfer images on the paper

The plates are made, so water repellant inks stick to the plate’s bits containing the pictures and text. A thin film of water over the empty portions of the plate snubs the oil-based inks.

The ink on the plates is initially moved to a rubber-covered blanket. This way, when the inked rubber blankets roll over the printing media, the ink reaches the paper’s surface to print images and texts.

The offset printing process entails separate plates and cover rollers for each ink color utilized for printing. Various varieties of presses, plates, and inks are utilized for various run lengths and substrate prerequisites. For instance, a few presses may print many duplicates of a magazine. Different presses may print 250 huge sheets that will be collapsed to make multi-page flyers.

Different types of Offset printing

There are various types of lithographic printing machines such as,

Web Press

Web Press Offset Printing

Web offset printing machines use continuous moves of paper through the print machine. After the pages are printed, they are isolated and cut. This kind of offset printing machine is utilized to print 10,000 or more copies of prints, such as public or local papers, magazines, and mass-market books.

The web press is further classifies into two types, such as the coldest web press, where the inked is etched into the paper by absorption, and the Heatset web press, along with ink absorption evaporation at high temperatures, takes place to imprint ink into paper.

Sheet-Fed Press

Sheet-Fed Press Offset Printing

Unlike Web Press, sheetfed printing machines do not use rolls of papers but feed just pre-cut pages through the printing press. As offset Web press, the Sheetfed machines are not economical for high-volume printing. Though, they are simpler to work and keep up with. They also allow imprinting on cardstock, plastics, and metal.

A Perfecting Press is a press to imprint images or text on both sides of the paper. All web pressers are recognized as perfecting press because the paper move goes through the press once, and the two sides of the sheet are printed as the paper flies through it; however, not all sheetfed presses are worked to print on the two sides.

Pre-press

Pre-press offset printing

Pre-press is a term used for the processes taking place between print layout and final printing. Nowadays, CTP (Computer To Plate) technology can directly output the image into the printing plate, exposed to UV light to engrave printing data from digital media to printing plates. This technology has abridged the time and cost of setting up offset-printing jobs and making last-ditch amendments to the plates.

Offset Printings Inks

An enormous range of inks is offered for different types of offsets printings. Other than the four tones (cyan, magenta, yellow, and black), the customer needed Pantone brand tones can also be applied. These inks are formulated using plant-derived oils such as soya bean to or water phobic liquids made with synthetic compounds to carry pigment on the printing plates.

Offset Printings Inks

Some inks are prepared to change the pigmentation presentation on paper; for instance, the polymer bases inks make instant-dry prints when exposed to UV light without using heat sprays to quicken the sheetfed drying press processes. With efficiently prepared UV-LED inks and the best-restoring units, sheetfed offset presses can print on paperboards for bundling, non-permeable artificial sheets, foil-covered sheets, plastic sheets, cards, and tag stocks.

Substrates

The offset printing can print on a broad range of smooth and finished papers, paperboards, tear-resistant manufactured papers, and different plastics used for gift vouchers, sacks, bundling, and envelopes. The Security papers, carbonless papers for business structures, and metal-covered papers with silver and gold foils are some of the specialty materials available for offset printing.

TO control the expenses of high volumes of books, manuals, magazines, web offset presses principally use low-priced coated and uncoated papers. But the vast portion of these specialty materials is intended for use on sheetfed presses.

Finishing Process

Offset Printing Finishing Process

The finishing tools depends upon the type and volumes of prints, standard mail pieces, manuals, writing material, or packaging.

Finishing processes incorporate gadgets to manage and cut the paper, fold, bind, punch, etc. Some printed sheets might be foil engraved, laminated, glued, or embedded into mailing envelopes. Some finishing devices also conceivably apply transparent UV-treatable inks for toughness or enhancing decorative impacts on prints.

The last words about offset printing technology: 

With the advancements and innovations in the digital printing arena, offset printing’s productivity has improved dramatically. The producers of offset printing devices have created prepress processes,  programming tools, software, and consumables that empower offset presses to deliver quick turnaround, short-run print jobs of high image quality using customized print page sizes and paper types. The offset press also offers customized inks like metallic and Pantone to their customers. The press producers, such as Heidelberg, are developing efficient systems for offset printings machine sets that will allow the offset printings processes to be handled entirely robotically without human intervention such as press operators.