Frequent Scratches On The Anilox Rollers? This Pitfall-Avoiding Guide Must Be Memorized!

Frequent scratches on the anilox rollers? This "pitfall-avoiding" guide must be memorized!

In flexible printing, the anilox roller is the most core and most expensive component. However, even a slight neglect can cause damage, and scratches are among the most troublesome and costly quality defects in anilox rolls.

On some printed products, a lighter line or a noticeably darker line is found compared to other parts of the printed area. These are called anilox roller scratches, which damage the lines carved into the ceramic material on the anilox roller, representing external damage to the engraved parts of the anilox roller. Scratches can cause uneven printing results, and the maintenance cost of analox rollers is also very high.

So, what are the causes of scratches on anilox rollers? How can we prevent scratches on anilox rollers? In this article, I will analyze the relevant factors causing anilox roller scratches, hoping to offer some advice and assistance to industry peers.

PART.01

Types of anilox roller scratches

By observing the printed product, anilox roller scratches can generally be divided into two types: light-colored streaks appearing in the printed area are called mild wear marks, while dark streaks are deep scratch marks. Below is an analysis of two different types of scratches:

01

Deep scratches and lines

When the ceramic layer of the anilox roller is severely damaged, deep scratches and scratches will occur. Generally, when the operator of the flexographic printing machine applies excessive pressure to prevent ink leakage, the tip of the ink scraper scrapes against the ceramic surface of the anilox roller, damaging the engraved pits on the surface and causing scratches on the anilox roll.

Therefore, more ink is delivered to the damaged engraving area of the anilox roller, where the printed color appears noticeably darker. Therefore, the appearance of these scratches is darker than the color of other areas on the printed material. In addition, the occurrence of deep scratches and sribing is also a factor leading to ink waste.

02

Minor, abrasion-like scratches

Mild wear scratches are most common in flexographic printing, appearing as light-colored streaks on printed products. Therefore, in areas with minor wear scratches, the printed product either has no ink or the ink color is very light.

Mild wear scratches are caused by a foreign object stuck on the anilox roller, which can scrape off the top layer of the anilox roller. This reduces the amount of ink the anilox roller can carry, resulting in light streaks or no ink on the final printed product.

PART.02

Causes of anilox roller scratches

To identify the root cause of anilox roller scratches, a variety of issues related to anilox rollers must be considered. Once the causes of scratches are fully understood, operators can proactively prevent anilox roller scratches in future printing production, avoiding high maintenance costs and cost losses caused by downtime for repairs.

01

Small particles accumulate during ink metering

Generally, anilox roller scratches usually form during ink metering, at the contact point between the squeegee and the anilox roller. This is because hard particles get stuck between the cure knife and the anilox roller. Smaller particles may scratch the ceramic surface of the anilox roller, causing roller scratches and resulting in light-colored streaks on the printed product.

02

Excessive braking pressure

In addition, excessive braking pressure applied by operators is also a major cause of anilox roller scratches. Braking pressure can interfere with the normal operation of the ink scraper blade and damage the engraving layer of the anilox roller. Operators apply excessive braking pressure to cover issues such as positional deviations, ink leakage, or mechanical creep. Due to the applied pressure, the tip of the ink scraper blade may fall off, resulting in scratches on the surface of the anilox roller.

03

Particles are embedded in the ink device

Sometimes, over time, small particles and impurities can get stuck in the ink device. During normal operation, the ink device can easily deliver these particles to the contact point between the ink squeegee knife and the anilox roller, scratching the surface of the anilox roller and forming scratches. Additionally, these particles may cause the tip of the squeegee blade to break, leading to more ink overflow. This results in dark stripes on the printed product.

04

The knife rack is not aligned

In flexographic printing, each doctor blade is suitable for a specific number of network lines. Therefore, when replacing the anilox roller, the alignment of the ink scraper blade must be adjusted. Similarly, when removing the old ink scraper and replacing it with a new one, the alignment of the tool holder must also be adjusted. If the tool holder is not aligned in time, it is likely to damage the surface of the anilox roller, resulting in scratches.

05

Small particles are blocked

Clogging of small particles in the engraving area of the anilox roller is also one of the main causes of mild wear scratches. Small particles can clog the surface of the anilox roller, reducing the engraving area and making the ink marks on the final printed product lighter.

PART.03

Textured roller scratch solutions

Scratches are undoubtedly one of the "nightmare" in flexographic printing, as they are extremely costly to repair and expensive to replace. It is best to take preventive measures to avoid the formation of anilox roller scratches. Below are some of the solutions I have summarized to prevent scratches on anilox rollers:

01

Use non-metallic ink scrapers

The ink scraper is one of the main factors causing scratches on anilox rollers. Ink scraper materials can be roughly divided into two main categories: steel and plastic. Traditionally, squeegee knives are made of metal, so when excessive pressure is applied, both the blade itself and the engraved rollers in contact can suffer serious damage. Because plastic squeegee blades have less rigidity than carbon steel ones, plastic squeegee blades wear more slowly and cause less wear to the anilox rollers. From the perspective of stiffness of the squeegee blade, plastic squeegee cutters need to be thickened to achieve the ideal strength for continuous production. Therefore, to avoid scratches on anilox rollers, it is recommended to use a non-metallic ink scraper.

02

Regularly clean the anilox roller

Regularly perform deep periodic cleaning of the anilox roller to remove any fine particles stuck in the engraving area. Using the correct cleaning methods and cleaning agents ensures the mesh cavity of the anilox roller is clean, preventing ink drying, clumping, and impurity accumulation, thereby minimizing the occurrence of scratches.

03

Optimized ink properties

Similarly, ink devices can contain jammed fine particles and impurities. By adjusting the formula of UV ink, reducing its viscosity and thixotropy, and using appropriate solvents and slow-drying agents, the ink drying speed is controlled to prevent caking caused by overly rapid drying. Additionally, filters capture small particles that could cause scratches, so thoroughly cleaning and filtering the ink device is also very important.

04

Reduce the pressure applied by the ink scraper

Excessive pressure on the squeegee blade can cause the blade head to break, and the resulting metal fragments can damage the ceramic surface of the anilox roller, eventually forming scratches on the printed surface. Therefore, it is recommended to apply appropriate pressure to the squeegee to prevent damage to the anilox roller caused by abnormal pressure from the blade.

05

When installing the ink scraper, ensure the ink chamber is properly aligned

When installing a new squeegee blade, cavity alignment is crucial for orderly printing production in the future. If misaligned, the squeegee blade will scratch the engraved surface of the anilox roller, resulting in scratches. Therefore, when installing the squeegee blade, the ink chamber must be aligned, which can greatly reduce the likelihood of scratches on the anilox roller.

In summary, anilox roller scratches are a very common quality issue in flexographic printing. Factors such as ink clumping, excessive squeegee blade pressure, and particle blockage can all cause anilox roller scratches. Therefore, the preventive measures of "targeted treatment" can greatly avoid the occurrence of anilox roller scratches. We hope the solutions shared in this article can help industry colleagues better address this printing quality issue and better apply flexographic printing.