Printing Shrink Sleeves and Printed Cans on a Flexographic Printing Process
If you’re developing shrink sleeve can labels for the very first time or diving in the deep end with a truck full of printed cans, it’s worth getting to grips with the flexographic printing process. Both our shrink sleeve label providers, IMS, and our printed can manufacturers, Crown Beverage Packaging, use Flexographic (commonly referred to as Flexo) printing presses to transfer your artwork from the computer screen to the can or shrink sleeve. Understanding the printing process from the outset can save you time, money and hassle, and will help inform your design decisions so you can produce the most effective branding possible.
What is Flexo printing?
Flexographic printing is essentially a modern version of letterpress printing. Modern Flexo presses use flexible printing plates attached to a series of rotating cylinders on what’s called a “web press”. A continuous ream of your chosen material (the substrate) – in our case either sheet aluminium for printed cans or pvc for shrink labels – is fed through this series of printing plates attached to rollers. The raised surface of each plate transfers a single colour of ink to the substrate as it passes through. It is perfect for high volume printing runs, such as your new shrink sleeve labels or printed cans.
Let’s take a look at the processes involved in printing shrink sleeves on a Flexo printing press:
Designing your shrink sleeve can labels: working with West Coast Canning’s specialist can design team or your own graphic designer, develop your artwork in accordance with our supplier’s artwork guidelines. The guidelines are specifically set out to ensure your artwork can easily be converted for flexographic printing
Prepress: IMS’ art department prepare your shrink wrap label design for printing. Every colour used in the design must be separated out into layers which are used to create each of the flexible printing plates that will be mounted on the rollers of the press.
Platemaking: There are two common modern methods of flexographic platemaking. The first involves a light sensitive polymer (photopolymer) plate. A film negative is created from each layer of your design and placed on the plate, which is then exposed to UV light. The areas of photopolymer that are exposed to light harden and the soft areas are then washed away, leaving just the hardened raised surface. It is this raised surface that will transfer the ink to the pvc shrink sleeve substrate.
The second method is known as digital engraving and uses a computer-guided laser to etch your design on to the printing plate. Digital etching is a less labour-intensive process and allows a little more flexibility with minimum order quantities, due to the lower initial setup costs. So if you’re only after a small amount of shrink sleeves, this could be the answer for you.
Printing: Ink is transferred to the raised surface of the printing plate, transferring that image to the substrate as it passes through the rollers. The sheet is then fed through a dryer and onto the next roller which prints the next layer of your label design. This continues until the entire image has been built up, colour by colour, to produce your final shrink can label. This ain’t your everyday office printer!
Simply put, colour spaces refers to the colours that will be used to print your design onto your chosen substrate. In the case of shrink sleeve label printing, we either work in CMYK or we use the Pantone Matching System (PMS).
In CMYK printing layers of Cyan, Magenta, Yellow and Key (black) are combined in varying amounts to reproduce the desired colours. Tiny rows of dots of each base colour are printed one on top of the other at varying angles to give the illusion of one solid colour. The colour is changed by adjusting the size of the dots in each colour. This is called halftoning. A limited number of plates can be used in a printing press, which would normally limit the number of colours in your design. CMYK printing mixes four base colours to print a range of different colours using just four plates.
Pantone Matching System (PMS)
The Pantone Matching System is a standardised colour reproduction system that allows printers and manufacturers across the globe to reproduce colours precisely, without direct contact with the designers. The PMS system can produce colours that cannot be reproduced by CMYK printing. If using PMS inks, each plate on the press would print a specific PMS colour of your design. PMS colours are often referred to as spot colours as they can be printed in one run, as opposed to process colours which are produced by printing a series of other colours, as in CMYK printing. The standardised colour space of the PMS is a huge bonus to designers and printers alike.