A Beginner's Guide to Flexography Printing and Its Uses

When you want to print on cardboard or plastic, you need flexography

Flexography is a modern version of letterpress printing. This traditional method of printing can be used on almost any type of substrate, including corrugated cardboard, cellophane, plastic, label stock, fabric, and metallic film. The flexographic printing process uses quick-drying, semiliquid inks. In this age of digital printing, flexography holds its own in the areas of large orders and long print runs, particularly of packaging products and labeling.

Flexographic printing uses flexible photopolymer printing plates wrapped around rotating cylinders on a web press. The inked plates have a slightly raised image and rotate at high speeds to transfer the image to the substrate. Flexography inks can print on many types of absorbent and nonabsorbent materials. Flexography is well-suited to print continuous patterns, such as for gift wrap and wallpaper.

Unlike the individual sheets of paper used in offset printing, the rolls of material used in flexography allow large orders to run with few interruptions to reload the substrate.

Advantages

The flexographic printing process:

• Runs at extremely high press speeds.
• Prints on a wide variety of substrate materials.
• Uses cost equipment that requires little maintenance.
• Uses relatively low-cost consumables.
• Is ideally suited for long runs.
• Handles all printing, varnishing, laminating, and die cutting in a single pass.

Disadvantages

• The cost of the flexo printing plates is high, but when they are properly cared for, they last for millions of impressions. 
• It takes several hours to set up complex jobs that print, varnish, laminate, and die cut.
• A large amount of substrate is consumed to set up the job, potentially wasting expensive material.
• If version changes are necessary, they are time-consuming to make.

Designing for Flexography

Like all types of printing, flexography has specifics relating to types of proofs, template and die cut specifications, issues with knockouts, drop shadows, fonts, tints, ink colors, image resolution, and image formats. The design and file preparation affect the quality of printing you get from flexography, so perfecting its specific requirements—some of which differ from the more familiar offset printing—is essential.

For example, the minimum font sizes used for both positive and reversed serif or sans serif type is based on the type of web press and whether you are printing to corrugated coated paper, uncoated newsprint, a polyester film or other substrates. For most purposes, the minimum size is 4 point to 10 point type, but that is a wide range. Sans serif type can usually be printed smaller than serif type, while reversed type is tricky to use in flexographic printing at any size. 

For designers new to flexography, a visit with the flexographic printing company is essential to learn how to best structure a print project to avoid delays and errors.