Method for creating an overlap by sheet welding

Method for forming an overlap by welding sheets, comprising the steps of:

• placing a main sheet (2) and a additional sheet (5) overlaid on one another, connected to one another by means of a contact area;
• the contact area selected from the group consisting of:
• a main sheet contact surface (3), a additional sheet contact surface (6), a contact sheet and a combination thereof;
• the contact area being opposite main sheet and additional sheet outer surfaces (4,7);
• heating the contact area (3,6) to a melting temperature for melting same, applying pressure between the outer surfaces (4,7);
• and
• cooling;
• the contact area (3,6) being made of a thermoplastic material and the main sheet outer surface (4) having a main sheet critical temperature;
• the method being characterized in that:
• the main sheet outer surface (4) is heated to a temperature comprised within the temperature range that is higher than ambient temperature and less than or equal to the main sheet critical temperature;
• and
• the additional sheet outer surface (7) is heated to a temperature that is higher than the heating temperature of the main sheet outer surface (4) and suitable for melting the contact area (3,6) in a heating time.