The relationship of your printing plate dot to your anilox line screen cell directly affects the quality of your flexo print.
Keep in mind that when using a low line screen printing plate (such as 55) you will typically use a lower line screen anilox roll (such as 250 – 500). When using a high line screen printing plate (such as 150) you will typically use a higher line screen anilox roll (such as 600 – 1200). The following chart outlines proper anilox line count to printing plate dot relationships:
| % Plate Dot | ||||
| 1% | 2% | 3% | 4% | |
| Plate Screen (per inch) | Minimum Anilox Line Count (per inch) | |||
| 55 | 500 | 330 | 280 | 250 |
| 65 | 550 | 400 | 330 | 280 |
| 85 | 700 | 500 | 400 | 360 |
| 100 | 900 | 600 | 500 | 440 |
| 110 | 900 | 660 | 550 | 500 |
| 120 | 1000 | 700 | 600 | 500 |
| 133 | 1200 | 800 | 660 | 600 |
| 150 | 1200 | 900 | 700 | 600 |
| 175 | N/A | 1000 | 900 | 700 |
| 200 | N/A | 1200 | 900 | 800 |
For example, in imperial measurements, when you are using a 100 line screen plate and trying to hold a 2% dot, the chart above indicates that you will need a 600 line screen anilox roll. Whereas, if you’re using a 100 line screen plate, and you’re trying to hold a 4% dot, you’ll only need a 440 line screen anilox roll.
The reason for this is simple. You do not want the dot on your printing plate to be smaller than the cell on your anilox roll. If that occurs, the dot can actually enter the anilox cell, picking up excess ink. This phenomena is referred to as "dot dipping" and can lead to very dirty printing situations.
The following models visually represent various line screen anilox rolls in relationship to various line screen printing plate dots. Notice that some of the printing plate dots are smaller than the anilox cells. In these situations, you will experience "dot dipping" and dirty printing. In other cases, you will notice that many anilox cells support a single printing plate dot. In extreme situations, this can lead to dot starvation and low densities on press.
Understanding the relationship of printing plate dots to anilox cells will help change your flexo printing process from an art to a science. By following the guidelines in this article, you should avoid the problems of dirty printing and print starvation, and save time and money in the process.
If you have further questions, please do not hesitate to e-mail technical service department, or call Harper at 800-438-3111 / 704-588-3371
