Screen selection
Select the screen first to ensure the integrity of the bright dot, but also to consider the dark dot reproduction.However, due to the dot enlargement, the level with an area ratio of more than 90% is the field, while 90% of the dark dot size is equivalent to 10% of the bright dot size. Take the original manuscript of 40cm’ as an example, as shown in Equation (2.1), the dot diameter is 90um.From the point of view of mesh/line ratio, 40cm’ manuscript should be selected at least 120 mesh /cm above the screen, otherwise there will be moire.As can be seen from the table Ⅰ, 120 mesh/wire mesh opening of 52 cm above um, its diagonal distance is 74 um, but as long as the dark dot diameter greater than opening the diagonal distance can guarantee the dark dot get enough support and not lost.To sum up, as long as the screen can ensure the integrity of the bright dot can meet the dark dot reproduction, so in the selection of screen only consider the bright dot reproduction.Therefore, select the screen can be according to the following steps (1) first, according to the number of positive pictures and the number of bright dot to determine the printing of the minimum dot diameter.(2) Secondly, according to the minimum mesh diameter D, determine the required mesh diameter and mesh number.When purchasing the screen, ask the supplier for the screen parameter specification. You can use Equation (2.2) to calculate which screen can meet the minimum dot replication (3). Finally, according to the thickness of the ink layer and the requirements of actual production, choose different series of screen for the same mesh.