01. Introduction to laser cleaning theory

This section covers the fundamentals of anilox roll laser cleaning and flexographic printing. It is intended for readers who want to understand how anilox rolls are made and how laser cleaning works.

LaserEcoClean provides anilox roll laser cleaning services. To make these terms clear, let us begin with the terminology:
Anilox roll — a cylinder designed to meter ink from the ink chamber (ink reservoir) onto the flexographic plate and then onto the substrate, most commonly polyethylene film or paper. Ink is pumped into the chamber under pressure and fills the anilox cells. The doctor blade removes excess ink from the roll surface. A schematic of the printing unit is available here.

Main printing processes

The main printing processes include flexography (relief printing), offset lithography (planographic printing), gravure, screen printing, digital printing and inkjet printing. Most of our customers are flexographic printing companies.

Flexography is a relief printing process. In relief printing, there is a pronounced height difference between the non-image and image areas of the plate, with the image areas raised above the non-image areas.
Anilox rolls are used most widely in flexographic printing.

In offset printing, anilox rolls are used to apply a coating over an image that has already been printed by the offset process. Coating units fall into two main types: ductor-roll systems and chambered doctor blade systems. Ductor-roll systems, which use two or three rollers, do not include an anilox roll. We successfully clean anilox rolls used to apply all types of coatings in offset printing. 
A small number of offset printing companies use an anilox roll to meter ink (we clean these rolls as well). Examples include Heidelberg Anicolor, KBA Genius.
Anilox rolls are also used occasionally in digital presses to apply coatings, and we clean these too. One example is the HP Indigo press.

In gravure printing, the image areas are recessed well below the non-image areas. LaserEcoClean technology can clean gravure cylinders; however, because of the way gravure production is organised, purchasing a stationary laser cleaning system is generally more economical than using a mobile cleaning service.

Main types of flexographic printing

Flexographic printing can be divided into three main segments:

• narrow-web flexographic printing;
• wide-web flexographic printing;
• corrugated flexographic printing.

Narrow-web flexographic printing is used for labels and certain types of flexible packaging. The image is printed on self-adhesive stock, which is then converted into labels for bottles, such as alcoholic beverages, or containers, such as shampoo and ketchup bottles. You can see what our customers produce on their websites: CCL-Label, Schreiner Group.

Wide-web flexographic printing is used to print packaging. The image is printed on films used to package foods such as confectionery, ice cream, dumplings and bread. You can visit our customers’ websites: Delo GmbH, Wentus.

Flexographic printing on corrugated board means printing directly onto corrugated board. Images are applied to packaging such as television boxes, bicycle boxes and corrugated food cases.

LaserEcoClean equipment specifications

Equipment for mobile cleaning with LaserEcoClean can clean anilox rolls from 100 to 5,000 mm long, including inline cleaning. Rolls weighing up to 200 kg can be cleaned off press. There is no roll-weight limit for inline cleaning. We remove all types of ink and coating, including white ink and varnish.

Equipment for stationary cleaning with LaserEcoClean can clean anilox rolls from 100 to 2,900 mm long. The maximum roll weight is 500 kg.

Anilox rolls used in narrow-web flexographic printing usually have a working face length of 100 to 400 mm and generally weigh less than 20 kg. Solid rolls are more common than sleeves in narrow-web applications. UV-curable, alcohol-based and water-based inks are used.

Anilox rolls used in wide-web printing are 500 to 2,400 mm long. Most modern flexographic presses use sleeves, which are considerably lighter than solid anilox rolls. A solid anilox roll may weigh up to 160 kg. Wide-web presses use alcohol-based, solvent-based, water-based and two-component inks.

Corrugated presses generally use water-based inks. Their rolls are 1,500 to 5,000 mm long and weigh 500 to 1,000 kg. We clean these rolls directly in the press (inline). 

Anilox rolls used to apply coatings in offset presses have a working face length of 600 to 1,600 mm and weigh 50 to 250 kg.