Printing machine and printing group for variable format offset

A printing machine for variable format offset which incorporates in combination at least one printing roller or central printing drum in a fixed position, and at least one printing group, said printing group comprising:

• a fixed linear guide system fixed in a support structure in relation with said printing roller or central printing drum;
• a first carriage arranged to be displaced by first actuating means along said linear guide system and provided with support devices configured for supporting in a rotatable and exchangeable manner an offset rubber-wrapped blanket roller or sleeve selected from a set of offset rubber-wrapped blanket rollers or sleeves of different sizes;
• a second carriage arranged to be displaced by second actuating means along said linear guide system and provided with support devices configured for supporting in a rotatable and exchangeable manner an offset plate roller or sleeve selected from a set of offset plate rollers or sleeves of different sizes;
• and
• a third carriage arranged to be displaced by third actuating means along said linear guide system and on which is installed an offset inking head provided with devices for approximating said third carriage to said offset plate roller or sleeve installed in said second carriage, and identifying and fixing a reference working position of the third carriage in relation with the offset plate roller or sleeve.