A method for operating a system including at least two robots for handling parts and a robot control unit arranged for control of said at least two robots. Each of the robots is arranged with a parts handler device including a rigid arm with one end connected to the end element of an arm of the robot by a first swivel arranged for radial movement of the rigid arm in relation to the end element. Each of the robots is also arranged with a gripper connected to the rigid arm by a second swivel arranged for free, passive rotation of the gripper in relation to the rigid arm. The method includes generating instructions for the at least two robots to pick and/or move and/or place a part and sending the instructions to each robot simultaneously.