Machine for cutting logs with grinding wheels and method

A machine for cutting logs of web material comprising:

• a feeding path for logs to be cut;
• a cutting head arranged along the feeding path, which comprises a coupling for a disc-shaped cutting blade and is adapted to impart the disc-shaped cutting blade a rotary motion around an axis thereof and a cyclic movement to cut the logs into single rolls, and to allow the logs to move forward along the feeding path;
• a grinding unit comprising at least one grinding wheel mounted onto a rotation shaft and co-acting with a side of the disc-shaped cutting blade to grind a cutting edge of the disc-shaped cutting blade;
• a controlled approach system to move the at least one grinding wheel towards the disc-shaped cutting blade and automatically adjust position of the at least one grinding wheel with respect to the disc-shaped cutting blade, said controlled approach system comprising a detection member adapted to sense position of said at least one grinding wheel;
• a support, inside which the rotation shaft of the at least one grinding wheel is supported, the rotation shaft being axially fixed to the support and the support being axially movable inside a housing;
• and an actuator configured to translate the support with respect to the housing in a direction parallel to an axis of the rotation shaft;
• wherein the at least one grinding wheel and the controlled approach system are mounted on a slide that is carried by the cutting head and said slide is provided with a movement towards and away from the coupling of the cutting blade to selectively bring the at least one grinding wheel in grinding contact with the disc-shaped cutting blade and out of contact with the disc-shaped cutting blade, the movement being automatically adjusted to compensate for wear of the disc-shaped cutting blade caused by grinding;
• wherein when the disc-shaped cutting blade is worn out the slide is adapted to position the at least one grinding wheel in a nominal non-touching position with respect to the worn out disc-shaped cutting blade as a new disc-shaped cutting blade is arranged on said cutting head to replace the worn out disc-shaped cutting blade and when the new disc-shaped cutting blade is arranged on the cutting head, the controlled approach system of the at least one grinding wheel is adapted to adjust the position of the at least one grinding wheel with respect to the disc-shaped cutting blade, by moving the at least one grinding wheel in an approach direction with respect to the slide from the nominal non-touching position towards the disc-shaped cutting blade such that the at least one grinding wheel is in a position to act with pressure against a respective side of the cutting edge of the disc-shaped cutting blade, and the actuator activated to control a gradual approach of the at least one grinding wheel to the disc-shaped cutting blade, until the at least one grinding wheel comes into contact with the side of the cutting edge detected by said detection member.