Hardness of the Anilox Roller
A brief timeline
Anilox rollers have been around for quite some time, with chrome anilox rollers tracing their origins back to around eighty years. Ceramic coated anilox rollers have been around for less than half of that time, around 30 years. Chrome still has it’s uses, but only in special circumstances.
Chrome production and weakness
In chrome anilox rollers, the cells were engraved mechanically by use of a knurling tool. The engravings were made in copper and coated with chrome, which is much harder than copper. Chrome-surfaced anilox rolls are still made today, but in the narrow web industry they are quite rare. A disadvantage with chrome rollers is that they damage easily and have low resistance to wear. Exposure of the underlying copper leads to rapid degradation of the surface and inhibits its performance (Kenny, 2010)
Comparison of Hardness
The process of construction is much longer and much more strenuous compared to the new ceramic rollers. The production methods have evolved significantly and so has the effectiveness and efficiency. The hardness of ceramic anilox rollers is around 1100-1300 Vickers. Whereas a traditional chrome anilox roller comes in around 850-900 Vickers, respectfully(Flexo Concepts, 2019). This is a clear indication of how far the flexographic printing industry has come in the past 30 years. As hardness has increased, so has resistance to wear. A chrome anilox roller has an expected life span of a little more than a year. There are some variables that can decrease this projection, such as use of metal doctor blades. Whereas, a laser engraved ceramic roller lasts around 3-4 years. Depending on care and activity, some anilox can see a longer life of nearly 10 years. Thus, productivity is better, and costs are significantly less.
Ceramic Hardness Testing
In order to achieve engraving standards, several variables of the anilox roller must be inspected and analyzed on a routine basis. The Ceramic Hardness Test is one of the procedures performed in routine SPC programs.
What is a Ceramic Hardness Test?
It is a hardness analyzing scale based on indentation hardness of material. In the case of evaluating ceramic, we use diamond indention. The test determines the hardness by measuring the depth of penetration from the diamond under a large load.
How does the Ceramic Hardness test work?
Most indentation hardness tests measure the deformation that occurs when the ceramic is penetrated with the diamond indenter. CTS Industries’ process uses two levels of force applied to the diamond at specified rates and dwell times.
Will this damage the ceramic surface?
Yes. Since the test is done using an impact process, the surface of the anilox roller will be damaged. This requires us to scrap the anilox roller after analyzing the results.
Can ceramic hardness testing be done after the roller is engraved?
No. The test is implemented in the manufacturing process, prior to engraving. Performing the analyzation after engraving would destroy the cells.
What is the hardness range?
CTS Industries’ standards on the Rockwell hardness N scale rate an average of 92-94, which averages 1100-1300 on the Vickers scale.