Method for building green tyres

A method for building green tyres, comprising:

• providing a forming drum;
• providing at least one feeding apparatus configured for feeding an elementary semifinished product;
• associating an anthropomorphic robotized arm with said forming drum;
• defining a correction function associated with said anthropomorphic robotized arm and with a working zone, the working zone being defined at an outlet where the elementary semifinished product exits the feeding apparatus;
• and
• after said defining, sending movement commands to said anthropomorphic robotized arm in order to move said forming drum in the working zone, said forming drum being moved in said working zone while said feeding apparatus is feeding said elementary semifinished product, so that said elementary semifinished product is laid on said forming drum in coils arranged side by side or at least partially overlapping each other for making at least one component of a green tyre of a given tyre model,
• i) wherein sending said movement commands to said anthropomorphic robotized arm comprises:
• determining target coordinates, associated with said at least one component of said green tyre, for said anthropomorphic robotized arm in order to move said forming drum in said working zone,
• retrieving from a memory area the correction function associated with said anthropomorphic robotized arm and said working zone,
• modifying said target coordinates by means of said correction function, thereby obtaining processed coordinates, and
• using said processed coordinates for said movement commands,
• ii) wherein the defining of the correction function comprises:
• defining a plurality of known positions having known coordinates;
• moving said anthropomorphic robotized arm in a manner such that said anthropomorphic robotized arm will reach, in succession, determined positions, each one corresponding to a respective one of said known positions;
• when said anthropomorphic robotized arm is in each one of said determined positions, detecting acquired coordinates of said anthropomorphic robotized arm;
• comparing the known coordinates of each one of said known positions with the acquired coordinates associated with the respective determined position;
• and
• calculating said correction function on the basis of said comparison,
• iii) wherein said known coordinates are at least in part different from the target coordinates,
• iv) wherein the correction function is independent from the target coordinates and is configured to operate also on positions, determined by the target coordinates, that are other than the known positions used for the defining of the correction function,
• v) wherein the defining of the plurality of known positions comprises:
• a) providing a calibration device, the calibration device comprising:
• a base plate;
• a support rotatably mounted on the base plate;
• and
• a reference element translatably mounted on the support, the reference element comprising a cursor and a tip;
• and
• b) moving the support and the reference element to define, by a point of the tip, the plurality of known positions, and
• vi) wherein the support is positionable in a plurality of first positions relative to the base plate and the reference element is positionable in a plurality of second positions relative to the support and is fixed into one position of the plurality of second positions by inserting at least one pin or screw into one slot of a plurality of slots on the cursor.