Difference between Offset and Flexo printing

There are various types and sizes of package printing. Flexographic, digital, gravure, and offset printing are the four primary types of packaging printing processes used by printers and label makers. In packaging, offset, and flexographic printing are two of the most common printing methods for jobs requiring long-term consistency, quality, and long-run runs. But what is the difference between offset and flexo printings ? Before we begin, let us explore the flexography and offset printing methods.

What is offset printing?

The offset printing method involves moving an image from a rubber “blanket” to a plate (usually aluminum) and then onto the printing surface. This form of printing is called offset because it involves the transfer of an inked image from the plate to the blanket.

How does flexography work?

The process involves the roll-feeding of an image onto the web.

Every color is produced on a photopolymer plate wrapped around a rotating cylinder. Similarly to letterpress, the graphics and text for each color are raised from the printing plate. Only those parts of the plate that are raised receive ink.  

The Similarities between Offset and Flexography printing.

Here are some similarities between flexo and offset printing that might help explain the key differences:

• Each process requires a printing plate or another image carrier.
• Both methods use wet ink.
• These processes can be applied to a wide range of substrates.
• The setup times and the need for image carriers make these processes suitable for long-run jobs.
• In contrast, flexographic printing can be done on almost any flexible surface, while offset printing can only be done on flat surfaces.

Plate

A roller transfers ink onto a printing plate during offset printing. Depending on the type of offset press, this can either be a flat-bed or rotary process. Aluminum plates are typically used. During the drying process, wet images are transferred onto a blanket, then transferred onto the substrate.

Flexible plates are used for rotary printing with flexo printing. Photopolymer compounds are used to make these plates, which can be wrapped around a printing cylinder. Lasers are used to image the relief image on the plate, and then the polymer is dissolved into a solvent or a water solution in a processing unit to fix it. A rotating ‘anilox’ roller transfers ink from the ink well to the flexo plate. A separate printing station and flexographic plate are needed for each color to be printed. After printing, the image is applied directly to the substrate. It is possible to reuse printing plates several times if stored correctly until eventually, they need to be replaced.

Ink

A typical offset printing process consists of four colors; cyan, magenta, yellow, and key (which is black). The four colors have their print stations. Spot colors are made by combining the process colors. Ink can be water-based or UV curable.

Even though process colors are used in the flexo process, spot colors are typically printed on additional print stations. Depending on the requirements, colors can either be pre-mixed or mixed in-house. As well as water-based and UV-curable flexo inks, there are also water-based inks. Inks based on solvents can also be used. Inks with UV properties enable faster press speeds and can be left on the press for the remainder of the day without needing to empty and clean individual print stations. During inactive periods, water-based inks should be removed from printing presses to prevent the ink from drying on the rollers and ink trays.

Surface

Flexography can be applied to absorbent or non-absorbent materials, such as cellophane, foil, cardboard, fabric, plastic, or metal. Packaging products include envelopes, retail bags, wallpaper, paper, newspapers, sweet wrappers, labels, etc. A flat surface is used with offset printing, while with Flexographic printing, a flexible surface can be used almost anywhere. High-speed flexographic printing can be achieved using flexo printing, and many presses can handle multiple converting operations in a single pass.

In addition to paper, metal, cardboard, cellophane, and vinyl, offset printing machines can print on many other materials. Your printing surface must be flat and smooth. Among its many applications are printing newspapers, books, magazines, stationery, posters, brochures, etc. It will require a second pass to print both sides of a substrate. In the same way, die-cutting, slitting, folding, creasing, laminating, etc., are all secondary processes.

Making the right choice between Offset & Flexo printing

In flexography results in high-speed production and high-quality results. Generally, it is an efficient choice for large-scale printing tasks in many ways.

It is expensive to use an offset printing press because it has complex print units, but it is guaranteed to produce high-quality images. Label materials can be customized using this printing technique.

These key differences may help you make the right choice between offset and flexo printing based on your printing objective.

Read next about Gravure vs Flexo Cost Comparison