Manipulator for moving and positioning a piece between a first position and a second position along a predefined path, having: - a load-bearing structure provided with a support element; - a mobile arm for gripping the piece comprising a driven pin or transferor projecting transversely from said mobile arm; - a guide wall supported by said support element having a rear face (15") facing towards the support element and an opposite front face wherein said guide wall comprises a curvilinear guide groove or cam configured to slidingly engage said driven pin or transferor so that said pin or transferor can travel along the curvilinear guide groove or cam for its entire length dragging the mobile arm; - an input shaft of the oscillating rotary movement rotatably connected to said support element in a substantially orthogonal manner to the guide wall, said shaft defining a rotation axis (S-S); - an oscillating arm fixed orthogonally to said input shaft of the movement, said oscillating arm having a groove radial in relation to the input shaft of the movement, said radial groove slidingly engaging said driven pin or transferor so that said driven pin or transferor can cross the radial groove for its entire length; so that the input shaft of the rotary oscillating movement drags in rotation the oscillating arm, said oscillating arm dragging the driven pin or transferor simultaneously along the radial groove and along the guide groove, dragging the mobile arm along said predefined path; wherein said guide wall is a flat plate made of two plate portions (11, 12) substantially parallel to each other or lying on the same plane, and wherein said two plate portions (11 and 12) are movable away from/towards each other along said lying plane so as to vary the shape of the guide groove or cam; said manipulator being characterized in that said support element is a wall parallel to the guide wall, comprising an upper spacer element adapted to form an upper support surface for said guide wall, and a lower spacer element adapted to form a lower support surface for said guide wall forming an interspace of a thickness such as to house inside it said oscillating arm and allow the rotation of said oscillating arm within said interspace. - a load-bearing structure provided with a support element; - a mobile arm for gripping the piece comprising a driven pin or transferor projecting transversely from said mobile arm; - a guide wall supported by said support element having a rear face (15") facing towards the support element and an opposite front face wherein said guide wall comprises a curvilinear guide groove or cam configured to slidingly engage said driven pin or transferor so that said pin or transferor can travel along the curvilinear guide groove or cam for its entire length dragging the mobile arm; - an input shaft of the oscillating rotary movement rotatably connected to said support element in a substantially orthogonal manner to the guide wall, said shaft defining a rotation axis (S-S); - an oscillating arm fixed orthogonally to said input shaft of the movement, said oscillating arm having a groove radial in relation to the input shaft of the movement, said radial groove slidingly engaging said driven pin or transferor so that said driven pin or transferor can cross the radial groove for its entire length; so that the input shaft of the rotary oscillating movement drags in rotation the oscillating arm, said oscillating arm dragging the driven pin or transferor simultaneously along the radial groove and along the guide groove, dragging the mobile arm along said predefined path; wherein said guide wall is a flat plate made of two plate portions (11, 12) substantially parallel to each other or lying on the same plane, and wherein said two plate portions (11 and 12) are movable away from/towards each other along said lying plane so as to vary the shape of the guide groove or cam; said manipulator being characterized in that said support element is a wall parallel to the guide wall, comprising an upper spacer element adapted to form an upper support surface for said guide wall, and a lower spacer element adapted to form a lower support surface for said guide wall forming an interspace of a thickness such as to house inside it said oscillating arm and allow the rotation of said oscillating arm within said interspace.