Putting in place effective anilox roller cleaning procedures, adapted to the facility’s needs, should be a priority for every printing house. If done right, they will translate into longer anilox lifetimes and better ink transfer, which improves the stability and repeatability of printing. It is a crucial component of pre-press and should be a key part of an advanced quality control system.
It is worth answering these questions: Why pay several thousand euros for new anilox rollers? How much production time and materials are wasted because of inadequate set-up? Why compromise the business reputation and printing quality? What is the best anilox cleaning solution for my printing house?
We analyzed the advantages and disadvantages of commonly used methods to help printing houses make informed decisions about anilox cleaning solutions.
Chemical anilox roller cleaning – manual
How it works: There are usually two types of chemical anilox roller cleaning: daily cleaning after each new set-up and deep, acid-based cleaning every 1-3 months. Daily, anilox rollers are washed with link-specific solvents after each retooling. Every 1-3 months, aggressive chemicals are used for deep cleaning, with a noble steel brush applying the agent to the roller and letting it react, penetrate the ceramic surface, and clean.
Advantages: No tools necessary. Quick cleaning process.
Disadvantages: Chemical use on some anilox rollers containing light metal or rubber elements and bodies can damage the surface. The process is manual and, therefore, not fully repeatable and precise. Manual washing with chemical agents may harm the operator’s health, the environment, and the generation of chemical waste that needs to be neutralized. Operators must wear safety clothes and equipment (goggles and protective gloves).
Chemical machine Anilox cleaning
How it works: The anilox roller is first treated with ink-specific solvents and then blasted with heated chemical agents (usually alkaline wash). Solvents quickly separate the binding agent from the ink. Alkaline cleaning agents (e.g., caustic soda) dissolve the remaining mixture, which takes more time.
Advantages: Chemical anilox cleaning can be very effective with a good selection of solvents relative to ink. It is a fast-paced process that takes place within a sealed machine. Some environmentally friendly solutions (e.g., water-based) make it less troublesome for operators and the environment.
Disadvantages: Using chemicals on some anilox rollers can lead to corrosion of metal parts and blister problems under ceramic microcells that may affect the physical properties of the roller, interaction with doctor blades and ink transfer. Stains on the anilox surface are likely. Many worker safety and environmental concerns are also connected with the chemical method.
Anilox blasting
How it works: The anilox roller is dry cleaned by blasting powdered agents such as sodium bicarbonate (NaHCO3) from a nozzle at relatively low pressure. Tiny particles of NaHCO3 granulate penetrate the microcells, brushing off dried ink and other types of contamination. Powder residues can be removed with water. The cleaning cycle takes about 40-60 minutes!
Advantages: The process is worker and environment-friendly. Sodium bicarbonate waste needs no special treatment. The system is easy to operate and takes little space
Disadvantages: Small amounts of cleaning granulate residue may remain in cells even after water washing. Blasting may leave white traces on the anilox roller. Individual grains of sand may be bigger than the area of anilox cells, which makes cleaning anilox rolls with a screen ruling larger than 800 lpi more difficult.
Ultrasonic Anilox roller cleaning solutions
How it works: A combination of ultrasound waves and a cleaning agent thoroughly cleans the roller. The anilox roll rotates in the heated chemical agent solution (e.g., caustic soda). Ultrasound waves activate a cavitation process, forming gas bubbles whose implosion on contact with the anilox surface releases pressure and temperature that help dissolve and destroy contamination in anilox cells. The process takes approximately 20-30 minutes.
Advantages: Ultrasonic cleaning is very effective with all types of ink used in flexography. It is also easy to install and operate. The process is fully automated. It is easy to filter the cleaning agent so it can be reused for an extended period, which is very economical. The system has low water consumption. Investment costs are relatively low, and the washing machines can be easily adapted to suit the individual needs of the printing company. Ultrasonic washer specifications contain the number of units in the machine, working unit length, and internal and external diameter. The machine can be fitted with single or double-frequency and rinsing functions.
Disadvantages: With mechanically damaged anilox, cleaning agents may penetrate metal parts, causing corrosion or blisters. The roller must cool down to room temperature before re-installation.
Laser anilox cleaning system
How it works: The anilox roller absorbs the laser beam’s energy, which has a high-intensity impact on its ceramic surface. It leads to the so-called cold evaporation of all types of contamination from the roller. A suction unit for removing ink resides, and other contaminations are required. The process takes about 45 minutes to complete.
Advantages: It is a dry and gentle method that uses no chemicals. The results are very good if the laser focus is set correctly (laser focus, power relative to ink type, rotational speed). It is suitable for inline cleaning. The anilox surface is not heated, so the risk of damage during cleaning is smaller, and the roller can be sent to production right after cleaning.
Disadvantages: Effective and damage-free cleaning with a laser is only possible with the right settings, such as anilox rotational speed, laser beam scan width, or feed speed. This requires knowledge and experience. Poor setup can cause permanent damage, such as cracks in the ceramic surface. The operator must wear protective goggles. Investment costs can be very high, so specialised providers usually offer this cleaning method as an outside service.
Conclusions
The decision to choose an anilox cleaning technology needs to be made in accordance with the needs of a particular production process. The key element should be an honest analysis of the advantages and disadvantages of particular cleaning methods relative to the production profile and inventory of anilox rollers. Considering the speed, efficiency, investment costs, and environmental impact, the Ultrasonic Anilox Roll Cleaning system seems the most favourable choice.
Before investing, it is important to be able to test the method under production conditions, verify its impact on the condition and wear of anilox, and check the efficiency of a chosen cleaning method through volumetric measurement (cm3/m2 / BCM) after washing anilox with different screen rulings.
Anilox cleaning solutions? We recommend the QUICKER ultrasonic anilox roll cleaner.
Author:
Kamil Cołoś – Technical Advisor. Measurement systems in flexography expert, responsible for technology audits and implementation of quality control systems in Print Systems.
