Method for determining the position of mutual contact between a printing roller and at least one counter roller

A method for determining the position of mutual contact between a printing roller (40) and at least one counter roller (30;

• 50), wherein the printing roller (40) and the counter roller (30;
• 50) to be placed in contact with said printing roller (40) are both arranged in a flexographic printing press (10), wherein the printing roller (40) is arranged between two counter rollers (30;
• 50), of which one counter roller (30) is in the form of a central drum (30) and the other counter roller (50) is in the form of an inking roller (50), wherein the printing roller (40) and both of the counter rollers (30;
• 50) to be placed in contact with said printing roller (40) each have a first electric motor (31;
• 41;
• 51) and can be moved in rotation, each by means of its respective first electric motor (31;
• 41;
• 51), wherein each of these first electric motors (31;
• 41;
• 51) has a first encoder (32;
• 42;
• 52), wherein at least the printing roller (40) and the inking roller (50) each have a second electric motor (43;
• 53) and can be moved translationally, each by means of its respective second electric motor (43;
• 53), in the direction (D) of a mutual approach between the printing roller (40) and the counter roller (30;
• 50) to be placed in contact with said printing roller (40), wherein each of these second electric motors (43;
• 53) has a second encoder (44;
• 54), and wherein the method comprises the following steps:
• (a) moving the counter roller (30;
• 50) that is to be placed in contact with the printing roller (40) in rotation by means of its respective first electric motor (31;
• 51) while the printing roller (40), which is arranged spaced from said counter roller (30;
• 50), is left in a predetermined angular position and not rotating;
• (b) moving the non-rotating printing roller (40) translationally in the direction D toward the counter roller (30;
• 50) that is to be placed in contact with the printing roller (40), by means of the corresponding second electric motor (43;
• 53);
• (c) detecting at least one non-zero value of a parameter by means of the first encoder (42) of the corresponding first electric motor (41) of the printing roller (40), wherein this parameter indicates an idling rotation induced by the mutual contact between the counter roller (30;
• 50) that has been placed in contact with the printing roller (40) and the printing roller (40);
• (d) determining the position of mutual contact between the printing roller (40) and the counter roller (30;
• 50) that has been placed in contact with the printing roller (40), based on the value of the detected parameter;
• characterized by the following steps:
• (e) changing the previous angular position of the printing roller (40) by a non-zero angle;
• (f) repeating steps (a) to (d) and determining the corresponding position of mutual contact between the printing roller (40) and the counter roller (30;
• 50) that has been placed in contact with said printing roller (40) for the angular position of the printing roller (40) that was changed in step (e);
• (g) calculating an average position of mutual contact between the printing roller (40) and the counter roller (30;
• 50) that has been placed in contact with said printing roller (40), on the basis of every position of mutual contact between the printing roller (40) and the counter roller (30;
• 50) that has been placed in contact with said printing roller (40), determined for a specific angular position of the printing roller (40), wherein the position of mutual contact between the printing roller (40) and the counter roller (30;
• 50) that has been placed in contact with said printing roller (40) is determined for each axial end of the printing roller (40) independently of the other end, and the average position of mutual contact between the printing roller (40) and the counter roller (30;
• 50) that has been placed in contact with said printing roller (40) is calculated for each axial end of the printing roller (40) independently of the other end.