May 27, 2016
The sole function of anilox is to ensure that a consistent amount of ink is delivered onto the printing plate, time after time. If the anilox rolls are not clean or kept in perfect condition, this will reduce the quantity of ink transferred, potentially causing one of the common flexo printing defects we see today (e.g., low print density, pinholing, mottled print). Also, if you don’t monitor anilox rolls, it is sometimes easy to lose track of anilox specifications, perhaps selecting an anilox roll or sleeve that is not best suited to your printing requirements. Hence, for flexo printers who want to optimize print quality, anilox selection and regular care and maintenance are essential to ensure your anilox rolls are delivering consistent print performance using your unique graphics, inks, and substrates.
Follow these three steps to maximize print performance:
- Measure — analysis of anilox roll/sleeve specification and condition.
- Clean — deep cleaning of your anilox rolls.
- Maintain — regular maintenance of your anilox rolls.
“For flexo printers who want to optimize print quality, anilox selection and regular care and maintenance are essential to ensure your anilox rolls are delivering consistent print performance.”
Left: Microscope: a 200x microscope is an excellent tool for identifying any signs of wear or ink plugging | Right: An example of an effective cleaning solution
Step 1: Measure
The first step in the process is to establish exactly the current condition of your anilox rolls. As all flexo printers know, even with careful handling and use, anilox cells can be prone to damage, wear, and ink plugging (a buildup of dry ink within the cells). All of these have a negative effect on achieving consistent print performance. Low print density is often an indicator of low anilox cell volume, demonstrating that the anilox roll could be dirty and subject to plugging. Therefore, it is essential to initiate regular inspection and measurement of the anilox roll. So, what are the most effective techniques?
There are several low-cost methods to measure anilox cell specifications and conditions:
- Direct measurement with a microscope.
- Direct cell volume measurement with anilox test strips.
- Remote laboratory analysis.
Using a low cost 200x magnification microscope and a simple inspection guide, printers can not only identify most of the critical selection parameters of the anilox roll—such as screen count and cell angle—but can also highlight whether the anilox cells look worn or have signs of ink plugging. Secondly, by the use of anilox cell volume test strips and a screen/cell volume selector, printers can also obtain an immediate indication of the current anilox cell volume. Although it can be argued that both of these simple techniques have some limitations of accuracy, both can be carried out on press or in the press room. They provide the busy printer with low-cost, instant information. This can often be essential so the printer can make prompt, informed decisions about whether the anilox roll is suitable for use in the press or if it needs cleaning or rectification work.
For a more accurate and considered approach to anilox measurement, some companies can provide an anilox audit service and remote laboratory analysis. These programs often involve taking a direct microfax impression on the anilox surface. This step can be carried out by a technician or by one of your own operators following simple microfax audit training. The microfax takes a perfect impression of the anilox roll surface, which can then be analyzed in the specialist’s laboratory. Once the analysis is complete, you will receive a full inspection report of the anilox roll’s condition, together with recommendations on any next steps for repair or maintenance of the anilox roll to suit your individual needs.
Step 2: Clean
At some stage in the lifetime of the anilox unit, it will be essential to carry out periodic deep cleaning. This intensive cleaning routine ensures all ink debris is removed from the cells and your anilox roll remains in excellent condition, performing at maximum potential for the longest period of time. It is recommended that deep cleaning be implemented as part of a regular maintenance schedule and be carried out on a weekly, monthly, or quarterly basis to suit your individual printing requirements.
Deep cleaning can be carried out using a variety of cleaning methods, including:
- Ultrasonic cleaning — an off-press cleaning technique that uses a
combination of ultrasound and cleaning solutions to deep-clean single
or multiple rolls and sleeves;
- Chemical rinse and high-pressure spray — an off-press method
generally for cleaning single rolls using a combination of chemical
rinse to break down dried ink, followed by high-pressure rinsing using water;
- Sani-Blast media system — a versatile and environmentally safe system
that can be carried out either on press or off press using high-pressure
sodium bicarbonate;
- Lasering — a nonabrasive technique (on- or off-press system) using a
defocused laser beam to vaporize dried ink from the cells; or
- Manual cleaning — with concentrated solutions; again, this can be carried out
on press or off press.
Step 3: Maintain
Once you know exactly the condition and specifications of your anilox rolls and you have a good, cost-effective deep-cleaning regime in place, the last important step is to keep the anilox rolls in good condition on a daily basis. This regular cleaning ensures not only the best day-to-day and job-to-job print consistency, but also extends the period between deep-cleaning cycles. Set up and document daily cleaning routines using the press inking wash-up systems. These regimes can be carried out at color or job changes, or at the start or end of production shift periods.
So, if you are a flexo printer looking to optimize your print performance, save money on press downtime and replacement of anilox rolls, take note of these three key steps to improve print consistency and overall quality. Measure, clean, maintain—it’s that simple.
Graham Racey is the distribution sales manager at Pamarco, Europe. He can be reached at graham.racey@pamarco.com.
