By Eric Frank, SVP Marketing, Koenig & Bauer (US)/(CA)
I get this question all the time, and it baffles me. Just take a walk through your local grocery or big box store. Starting in the food aisle, you’ll see rows and rows of printed folding cartons. In the beverage aisle, you’ll find numerous logos printed onto metal cans, labels glued onto plastic bottles, and writing engraved into pop tops. In the toy aisle, you’ll see more paper boxes, clear film, and multi-colored foils. Even in the garden section, printing can be seen on seed bags and fertilizer packaging.
Printing is everywhere and alive and thriving, with many types of analog printing processes used currently across the world. Below is an intro to five essential types, which I teach twice per year at PPC’s Folding Carton Boot Camps. There, newcomers to the industry learn about printing and the rest of the exciting and varied process of folding carton manufacturing.
Now, let’s get printing!
A versatile printing process, flexography can be used for many types of products and has the ability to produce batchs of 1,000 to 1 million. In flexo printing, the ink is carried directly from a raised image on an etched plate onto the substrate. It can be used to print on paper and paperboard, plastic film, corrugated cardboard, and metallic surfaces. The telltale sign of flexography is a slight halo around the print.
While producing large batches of products and goods can sometimes sacrifice quality, this is not always the case for flexography, as its print quality can range from standard to very good.
Gravure printing is used much less frequently than other processes. Often employed to produce publications like magazines and catalogs, the process relies on engraved cylinders that transfer ink directly onto paper via an intaglio cell. The process begins when the ink picks up cells on the surface of the metal cylinder. From there, excess ink is removed with a doctor blade, and the remaining ink in the cells is transferred directly to the substrate. A distinguishing sign of this printing style is a slightly ragged edge around the print.
Gravure printing is of a high-quality resolution and is typically used for producing large quantities of products, ranging of 250,000 to 10 million pieces.
Offset lithography is another very commonly used printing process around the world. With diverse automation opportunities, there are many, many different printing options available within the process. Offset litho can print folding cartons, labels, commercial work and even currency.
The process involves an oleophilic, or ink-loving, image on the printing plate and a non-image hydrophilic area. From there, the printing plate transfers the image onto a blanket cylinder, then onto the substrate. The impression or back cylinder holds the paper securely and evenly to ensure the highest print registration and quality. Each printing unit has a different color, and rollers wet the plates before adding ink.
While other processes have just one roller, offset lithography has many rollers to smooth out the ink, ensuring it covers the substrate very clean and easy with few or no imperfections. Offset lithography can produce a vast range of products amount from 500 to 500,000 and up to millions. This leads to a range of good-to-excellent printing quality with no ridges, stamps, or marks visible around the print.
Though not widely used, screen printing is perfect for non-traditional substrates like fabric, posters, stickers, vinyl, and wood. Screen printing uses woven mesh to support an in-blocking stencil to produce the desired image. This process involves using a fill blade, or squeegee, across a screen stencil, which forces or pumps ink through the mesh openings for transfer action during squeegeeing.
Due to the nature of the process and the time it takes to make products, screen printing is used to create small amounts of goods or when you need a real thick layer of ink.
Another less common technique, letterpress was invented by Johannes Gutenberg and is one of the oldest forms of printing. In this form of relief printing, ink is applied to a plate that has carved, raised surfaces of the desired image. The ink-ridden plate is then applied to the substrate using pressure.
Due to the time-consuming nature of the process and inability to load many substrates at once, letterpress printing is today used to create small batches of items such as wedding invitations or stationery.
There you have it: the unique and intricate world of analog printing today! Ready to learn more? I recommend checking out an article about digital printing found in the Industry Voice section of PPC’s website. PPC also offers a primer on some of the most common types of paperboard. And don’t forget PPC’s next Folding Carton Boot Camp, held each Spring and Fall, for a crash course in all things folding carton!
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