Offset Printing Process: How it works?

Offset printing or offset lithography is a printing press technique that transfers the ink from a plate to a rubber roller (or blanket) and then to various substrates.

It is typically used for mass production, such as printing large quantities of newspapers, brochures, stationeries, magazines, and boxes.

It is one of the most widely used printing options for its high-quality prints and low cost aside from flexography printing and digital printing.

Types of Offset Printing

Web-Fed Offset Printing

Web offset lithography is mostly seen in the printing of newspapers and boxes. In this process, rolls of paper are fed continuously through the press and can produce over 5,000 printed materials.

The paper is cut afterward (this is also part of the press) to create identical sheets. Web-fed offset printing presses can produce over 3,000 papers per minute, which translates to about 80,000 identical sheets per hour.

This option is ideal for organizations that need to produce large quantities at a small period of time.

Sheet-Fed Offset Printing

Unlike Web-fed, sheet-fed offset lithography produces smaller quantities as sheets of paper are fed individually. It is still considered a quick printing option compared to other printing operations available.

Sheet-fed printing can print up to 12,000 sheets to 24,000 per hour. Over the years of modernization, sheet-fed has also improved in speed, which allowed it to do similar functions as the web-fed press.

The Process of Offset Printing

Pre-Press Process

The preparation for the artwork before going through the press is a vital step to produce the exact printing output.

One of the common mistakes designers make during their artwork preparation is not converting their work from RBG to CMYK.

The best way to make sure you are preparing your files correctly is by contacting a product specialist of the packaging or printing company you are working with.

A print product specialist can provide full expertise and advice on preparing your artwork.

Offset Printing Process

• The impression of the type that appears on the reverse side is first transferred to another plate, and then on to another rubber cylinder. 
  
  
• The impression of the image/text/graphics (or ‘type’) is first obtained on a ‘plate’ – this is usually a sheet of metal (although paper/polyester may also be used). It has been found that aluminum tends to give the best results.
  
  
• It is the impression on the plate that is transferred to a rubber roller/cylinder, which is then used for offset printing. There will be two plates involved in the process if both sides of the paper need to be printed on.
  
  
• A roller then feeds in the paper into the press. The cylinder (this is also made of rubber) containing the impression from the plate transfers the impression or ‘prints’ to the paper.

Benefits of Offset Printing

• High quality and true color: Since Offset uses ink instead of toner (digital printing), the result of the print is a lot richer and clearer
  
  
• Low cost: Medium to large quantity printing is best used with offset printing. The more quantities that are produced, the cheaper the unit cost becomes.
  
  
• Fast and efficient: Web-fed can produce over 80,000 copies of printed materials while producing them in high quality
  
  
• Flexible and dynamic: Offset printing works on a wide range of materials including paper, cardboard, wood, leather, and plastic while providing solutions to print finishing and other special requests

What this video for more detailed information about what I m talking about.