There are different types and sizes for packaging 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 the most popular printing methods for jobs that require consistency, quality, and long-term operation. But what is the difference between offset and flexo printing? Before we begin, let’s explore the methods of flexographic printing and offset printing.
What is offset printing?
The offset printing method involves transferring an image from a rubber “blanket” to a plate (usually aluminum) and then to the printing surface. This form of offset printing is called offset because it involves transferring an inkjet image from the plate to the blanket.
How does flexography work?
The process involves the image rolling over the web.
Each color is produced on a photopolymer sheet wrapped around a rotating drum. Like letterpress, graphics and text for each color are lifted from the printing plate. Only those raised parts of the plate receive ink.
Similarities between offset printing and flexographic printing.
Here are some similarities between flexo printing and offset printing which may help explain the main differences:
- Each process requires a printing plate or other photo holder.
- Both methods use wet ink.
- These processes can be applied to a wide variety of substrates.
- Setup times and the need for image vectors make these operations suitable for long-term jobs.
- In contrast, flexographic printing can be done on almost any flexible surface, while offset printing can only be done on flat surfaces.
The drum transfers the ink to the printing plate during offset printing. Depending on the type of offset press, this can be either a flat or rotary operation. Usually, aluminum plates are used. During the drying process, wet images are transferred onto a blanket, and then transferred to a 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. A laser is used to depict the relief image on the plate, and then the polymer is dissolved in a solvent or aqueous solution in a processing unit to stabilize it. The rotating “anilox” drum transfers the 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. Galleys can be reused multiple times if they are stored properly until they are eventually replaced.
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A typical offset printing process consists of four colors; Cyan, Magenta, Yellow, and Key (which is black). The four colors have their own printing stations. Spot colors are made by combining process colors. The ink can be water based or UV curable.
Although process colors are used in the flexo process, spot colors are usually printed on additional printing stations. Depending on the requirements, the colors can be pre-mixed or mixed internally. In addition to water-based and UV-cured flexo inks, there are also water-based inks. Solvent-based inks can also be used. UV inks allow for faster print speeds and can be left to press for the rest of the day without the need to empty and clean individual print stations. During idle periods, water-based inks should be removed from the presses to prevent the ink from drying on the rollers and ink trays.
Flexographic printing 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 flexographic printing, and many presses can handle multiple transfers in one pass.
In addition to paper, metal, cardboard, cellophane, and vinyl, offset printing machines can print on many other materials. Your printing surface should be flat and smooth. Among its many applications are the printing of newspapers, books, magazines, stationery, posters, brochures, etc. It will require a second pass to print both sides of the substrate. In the same way, die cutting, slitting, folding, creasing, lamination, etc. are all secondary operations.
Making the right choice between offset printing and flexo printing
Flexography results in high-speed production and high-quality results. Overall, it is an effective choice for large-scale print jobs in many ways.
It is expensive to use an offset press because it has complex printing units, but it is guaranteed to produce high quality images. Label materials can be customized using this printing technology.
These key differences may help you make the right decision between offset and flexo printing based on your printing press intent.