Aside digital printing mainly associated with short run printing, offset and flexographic printing are the main printing technologies used in the packaging industry.
Flexography, often abbreviated for flexo, is a printing technique using flexible relief plates. The plates are inked and applied directly onto the substrate.The process was patented at the end of the 19th century. Originally, the print quality was quite poor but remarkable progress have been made in the last 20 years. Today, progress in the plate making bring the print quality to a similar level as offset printing.
Once set up, the process is cost efficient and can print fast long runs. Plate making though is costly and thus make the printing technique more suitable for large volumes. Since the focus is on large volumes, printer manufacturers have developed web-fed presses (the substrate comes in rolls) with inline finish (die-cut and folding) capabilities. Although almost all types of substrates can be printed using flexo, it is mainly used for plastic bags, sacks and flexible packaging.
Offset printing process transfers (offsets) an image from a plate to a blanket and then to a substrate. This process allows a consistant high print quality. The sharpness of the output is due to the transfer blanket conforming to the texture of substrate. Consistency of the output even on long runs comes from the long life of the plates since there is no direct contact with the substrate. Plate making is also a cost effective step (it could be 10 times cheaper than for flexographic printing) and plates could be ready within an hour.
Offset printing is often combined with lithographic technique on the repulsion of oil and water (more details here). This allows flat plates to be used for a sharper rendering and a longer lifespan.
Web-fed and shett-fed presses are available on the market, their usage depending on the volumes to be printed.
In the packaging industry, we can see a strong trend towards hyper personnalisation, regionalization, special occasions and campaign targeted designs that make shorter runs an industry standard. The same frozen pizza will “wear” many different box designs depending on the season, special promotions, co-branding campaigns and what used to be a 1 million boxes unique design is trending towards 10 or 20 (or more) different designs, shortening hence the runs.
When flexographic printing is an excellent solution for very large runs where the sharpness of the rendering is not essential, sheet-fed offset printed packaging seems to be the path to follow as a cost efficient, flexible and reactive solution.