Quantifying the relevant parameters of a flexographic mask, or plate, lies at the very heart of plate certification. The ideal quantification process yields the maximum amount of information from the minimal amount of measurement. To qualify a mask or a plate, you need image elements and measurement tools.
An example of an image element is a 1 percent dot of a 150 lpi screen. If this were part of a quantification process, you would image the digital file to a mask, then make a plate from the mask. You would then need some way to assess, or measure, the mask and some way to assess, or measure, the finished plate. You then compare these numbers to some standard numbers to assess pass/fail.
The exact elements that Esko uses and the exact tools to measure and assess results are considered proprietary information.
For this article, we will describe one of the simplest, but most effective test elements used for XPS Plate Certification. Referred to as the “dot-fail test,” this element has square or rectangular “dots” of different sizes at different frequencies. The higher the frequency, the smaller the element that can be held. Through visual observation of the finished plate, one might record that in the top row, the 9-pixel spot is the smallest that can be held, in the middle row, the 25-pixel element is smallest to hold and in the lower row, nothing smaller than a 36-pixel element can be held. These numbers are then compared to standard numbers for the specific plate material to assess pass/fail. They can also be measured through time to assure the plate you make in the future has not changed since certification.