Flexographic label printing is still the most common form of label printing today as it produces high quality labels and is ideal for long runs involving hundreds of thousands of labels. Labels are printed on a continuous roll at speeds of up to 7,000 metres per hour. The inks are water-based and dry quickly. Preparation costs are high with four printing plates required for four colour process label printing. The plates are soft and flexible and are laid on large cylinders which allow a rotary process. This is more than off-set by speed and quality. The label stock is fed through a number of inking stations. Flexographic label printing machines also provide the option for lamination, die-cutting and waste stripping.
Letterpress label printing technology also produces high quality but lacks the speed of flexographic label printers so it is more suitable for medium length runs. Plates are adhered to a flat surface but the label stock is still fed through continuously. Again, preparation costs are high as four printing plates are required for four colour process label printing. The label stock passes over the printing plate and goes back to its starting position to enable continuous printing.
Screen printing is another process that is used for highly durable labels such as vinyl labels. The disadvantage of this method is that only one colour can be applied at a time. It is more commonly used for printing on unusual materials such as t-shirts but is also used for printed labels. The ink is applied through a mesh screen and uses negative film.
Thermal transfer label printing applies heat to get the colours onto the labels. Basically, coloured ribbons are melted and applied to the labels. The disadvantage of this process is the limitation in printing colours. You are restricted to the colours of the ribbons. Also, the speed is quiet slow but is still fast enough for short run label printing.
Digital label printing is the biggest growing sector of the label printing industry. This is because the demand for short to medium length runs is increasing all of the time. The advantage is that the cost is reduced substantially for these printed labels because no printing plates are required so the setup costs are reduced significantly. The recent improvement in digital technology has meant that labels printed digitally are now very comparable to the quality provided by flexographic and letterpress label printing machines.