The anilox roll has been referred to as the heart of the printing press. It carries the huge responsibility of delivering the precise amount of ink required to create an image exactly according to the customer’s specifications. That’s a big job! If anilox rolls are taken care of, they are your workhorses: consistently and repeatedly executing the desired image, job after job. They can last for years and provide a great return on your investment.
So the “health” of your anilox rolls is extremely important. There are several steps you can take to maintain their integrity. First, follow a good cleaning regimen to prevent ink from drying in cells. Plugged anilox cells can’t carry the volume of ink for which they were designed. (Read “Anilox Roll Cleaning is Essential to Effective Ink Delivery”) Second, make sure to handle the rolls properly to avoid damaging the ceramic coating. Once the edges become chipped, ink and solvent can leach under the surface and ruin the roll.
Protect your rolls from scoring
A third way to get the most out of your anilox investment is to protect your rolls from scoring. Anilox scoring occurs when a piece of metal becomes trapped against the doctor blade as the roll rotates. The fragment causes a deep scratch, or “score line,” destroying the cells in a stripe around the circumference of the roll. Not only is this expensive in terms of repairing or replacing the roll, but also costs a lot in substrate and ink waste, press downtime and unhappy customers.
If the roll’s surface becomes scored, the defects will show in the printed image. Sometimes a score line is a deep gouge across several cell widths. The band of damaged cells results in a dark streak in the print as more ink is delivered in this area. More often, the metal fragment wears down the walls of the cells, resulting in a “polishing” score line. In this case, the affected part of the anilox roll is not able to carry as much ink as the surrounding cells, and the corresponding area of print appears as a light streak.
Causes of anilox scoring
While there are many causes of anilox scoring, the most common ones relate to the use of steel doctor blades. Large pieces of the blade can break away as it wears or if the blade is installed with too much pressure. An excessive amount of pressure on the tip will cause it to bend back and eventually fracture off. Excessive pressure can occur when an operator neglects to adjust the blade holder setting when replacing a worn blade with a new (wider) one. Sometimes an operator will intentionally over-pressure the blade to compensate for other problems such as chamber leaks, chamber misalignment or warped or rippled blades.
Some ways to prevent anilox roll scoring are:
- Ensure proper chamber alignment and blade installation
- Use non-metallic doctor blades
- Do not over-pressure blades
- Clean anilox rolls regularly
- Do not run the press dry or let ink dry in cells
- Filter ink to remove metal fragments
Once a roll is scored, it must be reconditioned or replaced at the cost of hundreds to thousands of dollars. Not to mention lost substrate, ink waste, press downtime and being without the roll while it’s being reconditioned or replaced. Treat your anilox rolls like the important parts of the press that they are; in addition to proper cleaning and handling, preventing score lines will go a long way to ensure that you get the most out of your anilox investment!