Flexo Printing:The Definitive Guide (2022)

Flexographic printing is one of reliable printing method.It features high speed printing production and high printing quality

For over 30 years, Flexographic printing (also known as Flexo printing) has continued to be one of the most reliable ways to produce great-looking labels and other printing products.

It has evolved considerably with innovations, making it the most used printing technology today in the label and food package printing industry

These improvements have resulted in less material waste, more consistency, and predictability with elements like colour and fast make-ready times.

It’s vital to understand the terms used in flexographic printing to understand the whole process.

Here’s a summary of the flexographic printing process and what it entails

What is Flexo printing?

Flexographic printing is a widely used form of relief printing. Its ink is applied to a raised image on a flexible plate and then impressed onto a substrate. Ink is transferred through tiny holes from the anilox roll to the substrate, with each colour requiring a different plate. These flexible plates can allow customization options with your logo and design

Here is an easier way to think of it would be as if you’re stamping something – the plate acts as the stamp.

stamp-mark-logo

The advancements in technology make it possible to produce large orders of custom labels at high speeds.

The process adapts well to different materials and can be printed on any substrate, including metal, plastic, corrugated cardboard, flexo printing on paper, and non-woven fabric.

This material flexibility has led to its increased use on various products such as plastic bags, cut and stack labels, food packaging, and self-adhesive labels.

Flexo printing provides an optimal combination of quality, flexibility, and productivity. It can use different inks, such as water-based and UV inks.

Moreover, the inks are in the form of gels, not liquids, thus fast drying. This makes flexo printing ideal for printing wallpaper, books, food packaging, calendars, and laminated tetra packs.

What Are Flexo Printing Plates?

Flexographic printing plates are flexible photopolymer plates that transfer images or ink onto the surface you want to print on. They are designed in relief, meaning that the print surface is raised where the image is exposed.

When ink is applied to the plate, the plate surface contacts the substrate, leaving out relieved areas. They are a crucial element of the flexo printing process since the quality of the printed image largely depends on the quality of the flexo plates used.

Originally, flexo plates were made from rubber, but today they are made from photopolymer material, an organic substance that undergoes polymerization when exposed to light.

Depending on how often they’re used and maintained, flexible printing plates tend to last approximately three years. They are also flexible and can be wrapped around cylindrical plate rollers.

Flexo printing process

The Flexographic printing process transfers images from a flexible relief plate onto a substrate supplied in reel form.

It can work on uneven surfaces such as corrugated boards and is ideal for cartons, printing labels, packaging pharmaceutical products, and security applications. This printing method can also be used in printing newspapers and magazines.

How the Flexo printing process works

  • Artwork design

The printing process begins with an artwork design. Coming up with a flexo printing design that meets the requirements needed to produce the final product can be challenging.

The artwork must be designed to perfection since the image plates cannot be changed once made, resulting in costly errors. Once created, it is optimized for the flexographic printing press

  • Web-fed substrate materials

The continuous printing process of the flexo press allows substrate materials to be fed through the machine. This feature of the flexo press allows the constant printing process to achieve maximum large print production, rapid speeds, and accuracy

  • The Flexo printing press

Substrate materials in roll-form are first fed into the press machine while maintaining tension to prevent print defects and web breaks. The continuous printing process then fills the enclosed chamber with printer ink.

This ink is transferred to the anilox roller while the doctor blade removes the excess—the print ink cycles in and out of the enclosed system.

 Anilox roller carries a thin layer of ink from the inking system to the image carrier. Then the image is then transferred to the substrate by the image carrier.

Flexo press pulls the substrate between the impression cylinder and the image carrier. The impression cylinder ensures even ink distribution by holding the right amount of pressure on the substrate.

The substrate goes through various sections to dry the ink. The substrate can go through numerous impression cylinders, image carriers, and drying sections for each colour used in a single print rotation.

The final step involves rolling up the substrate again to prepare it for the cutting die, separating individual prints

Flexographic printing ink

Flexo ink comes in three distinct specifications: solvent-based, water-based and UV-LED curing ink or UV. The commonly used are water-based and UV inks since they are eco-friendly and offer excellent print quality.

The general composition of the ink consists of pigments, resins, solvents, and additives

A water-based ink replaces organic solvent with water and pigment with assorted additives like defoamers and agents to aid drying and adhesion.

It has high surface tension, making it popular in corrugated packaging. It’s also less expensive and works on a wide range of materials.

A solvent-based ink is composed mainly of alcohol, acetates, and pigments, with most of it being alcohol and a small number of acetates being common starting ratios. It usually has much lower surface tensions than water-based ink.

UV ink is composed of prepolymers, monomers, photoinitiators, and pigments, which adhere only when exposed to UV light or electron beam. It has a higher viscosity, and an EPDM elastomer is recommended for its resistance to ozone.

Since they are cured by an ultraviolet lamp that turns them from liquid to solid, they dry fast, producing sharper colours. As a result, they reduce energy consumption but are more expensive than other ink types.

Flexographic inks need to be fast-drying to match the printing speed of the press machine. These inks need to be maintained and controlled at a certain PH, viscosity, and temperature range during the flexo printing process for best results.

While this can be time-consuming, most flexographic press manufacturers introduce an auto control ink system to the flexo press.

Ink colour systems

Ink colour systems used in flexo packaging are GCMI and Pantone (PMS) colours. The Glass Container Manufacturers Institute (GCMI) created the FLEXO colour guide that featured multiple types of inks that were numbered for easy identification and shown on both white and Kraft paper.

The GCMI colour might not match a client’s vision, so Pantone colour options are selected. The options available are coated and uncoated colours. Coated Pantone colours are coded with a ‘C’ at the end, while uncoated colours have a ‘U .’

Pantone colours have a disadvantage compared to GCMI colours because they don’t provide swatches printed on Kraft, making the colours appear warmer, darker, and more muted than expected

What are the applications of Flexographic printing?

Applications of flexo printing refer to how consumers use the flexographic printing method for their printing needs. Flexographic printing is emerging as a popular method of printing for various reasons. As such, most organizations are turning to flexography, terming it as an effective method for printing

Flexographic printing uses non-toxic inks, making it desirable to print food packaging. It can be used to print food packages like milk cartons, beverage containers, food containers, and disposable cups and containers. The correct ink makes it equally safe to use in printing packages for medicines and other medical supplies. It can also be used on foil wrappers, hygienic bags, plastic, and cardboard packaging.

Applications of Flexographic printing

Flexographic printing can be used in almost all applications, making it the most flexible printing method. Its flexibility and proven ability to provide an optimal combination of quality and productivity make it a popular choice among industries looking to print attractive, well-designed consumer products

  • Newspaper and print media

One main advantage of flexo printing is printing high volumes of work within the shortest time possible. Therefore, it is used in companies that have large volumes of printing work that are needed within a short time, such as print media, magazines, newspapers, and books. It can also be used to print envelopes and wallpaper containers.

  • Consumer products

Flexographic printing uses non-toxic water-based inks to print on products. This makes it ideal for food packaging, for instance, since the package contents are kept safe from ink poisoning. Besides, the ink dries fast, making it suitable for fast-moving food packaging industries. 

Additionally, flexo printing can be used to print other consumer goods, such as laundry bags, gift wrappers, paper plates and napkins, and garbage bags

  • Medical and Pharmaceutical industry

Printed packaging is essential in the medical and pharmaceutical industries to ensure the safety of consumers and build brand awareness. Due to its flexibility and ability to print on various substrates, flexography accommodates different packaging materials used for medical supplies and medications

  • Non-rigid materials

Most digital printers are accustomed to rigid printing materials, meaning that they cannot be used on non-rigid materials. But, flexographic printers can be used to print non-rigid materials such as polythene and plastics. This makes them an excellent choice for industries that package and label their products with plastics or polythene.

  • Self-adhesive labels

Labels play a crucial role in conveying a wide range of information, from contact details to product descriptions. For example, in retail products, brands help market the product by grabbing customers’ attention.

While labels can also be done manually, machines are an effective solution to meet high production demand and reduce labour. Flexo printers are a good option since they can be used to print labels for different retail products at high speed and are cost-effective

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  • Home, school, and office

Since it offers consistency and accuracy, flexography is used to print various ruling products such as graph papers, medical charts, stationery, steno pads, and lined notebooks. Flexo printing will remain consistent with achieving high-quality end products even in large printing quantities.

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Flexographic printing advantages

  • Fast Speed

Since the printing process is done continuously on long prints and runs at high speeds, it creates high volumes of labels and packages within short time frames.

  • Available for different material

Flexo press can print different materials and substrates, making it a viable alternative to complying with national and international regulations. It also has low maintenance costs, thus eliminating the need for additional work and expenses.

  • Less waste

In addition, the flexo press produces minimal waste in terms of material, time and resources; hence environment and economically friendly.

  • Integrated with other process

It can integrate other online print processes such as lamination and die-cutting and convert them into a single pass. Also, it involves a controlled printing process, which requires less-trained personnel to achieve maximum output.

  • Food grade ink

What’s more, numerous types of inks can be used, depending on the type of application and processes applied to the printing process. Inks with low viscosity can be used, including bio-inks.

Besides, it allows you to apply only the necessary amount of ink on the printing plate to minimize ink consumption.

Flexographic printing disadvantages

  • Not suitable for small order

The printing plates suitable for Flexo are costly and are not economical for short print runs. The set-up and plate preparation time is usually much longer and less flexible when compared to other printing processes and techniques.

  • More expensive logo plate

Flexographic printing is preferable for large and medium orders due to the cost of setting up and making printing plates.

This is because a task that comprises numerous colours will require you to provide a printing plate for each colour. So, setting up a flexographic press will take time, and the more the colours, the longer it takes to set up.

  • Not suitable for mottle  design or complicate logo

Ink transfer is very important for successful flexographic printing.The amount of ink will go through through the components of the printing process and finally tranfer onto the substrate.

In the case of mottled image, however, too little pressure between the print cylinder and substrate causes not enough ink to transfer fully. The result will be a solid color that appears lighter than intended, uneven, or incomplete.

Why does flexo printing need to specify colours?

Digital printers have specific sets of inks, generally cyan, magenta, yellow and black (CMYK). Each colour is produced as tiny dots, which blend to form the desired colours in the document. However, a flexo plate creates a larger dot size, which, when viewed up close, becomes visible, and graphics appear pixelated.

You may also notice matching colours, especially on printed Kraft substrates. Even though CMYK approximates a wide range of colours, it cannot fit exactly what is seen on the computer screen.

Colours may appear to have a distinct tone when printed, making it difficult to maintain colour consistency across applications.

Additionally, while flexo printing requires different plates for each colour, printing graphics using CMYK will require you to purchase at least four separate plates.

This creates a huge price difference if your package involves one or two visible colours. Therefore, it’s more reliable and cheaper to specify colours in flexographic printing unless colour photos are involved.

Conclusion

Flexographic printing has snowballed, making it one of the most reliable printing methods. It can be used on various substrate materials and run at extremely high speeds, making it ideal for large, bulky printing works.

For this reason, most organizations have opted to switch from traditional printers to flexographic printers, as they are more effective and guarantee high-quality output. More so, flexo printers require low-cost maintenance, helping companies save money.

Now that you have a clear picture of what flexographic printing is, how it works, the pros and cons of using it, and the different applications. You best understand how essential flexographic printing services can benefit your production business. Choosing a flexo printing press is a step to achieving maximum output.

One Response

  1. I never knew that printing solutions could now offer printing functions for different industries such as label and screen printing functions. After moving to our current area, my business partner and I were hoping to find a UV printer that could offer custom flexographic functions to increase our printing production. He asked if I had thoughts on the best buying approach. Thanks to this helpful printing guide article for effective planning. I’ll be sure to check UV printing websites to gather information about their printers.

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