The goal of this work is to support workers doing repetitive tasks with Franka Emika Panda robot manipulator. The use case is about hitting rotors on the work table until the residues of material are eliminated (requested from a mechanical industry). This kind of effort stresses human articulations and it can lead to muscoloskeletal problems for workers in long periods. So a solution about cooperation between employees and robots is developed through a cartesian impedance controller that allows to the arm to control the impact requested from the user. Quadratic programming has been applied to optimize the configuration of the robot redistributing the efforts, due to the impacts, along the joints.