This paper describes the results obtained to identify the optimal control gain for a servoaxis of a Cartesian numerically controlled tooling machine. The problem was solved using a numerical model of the servoaxis and analysing the sensitivity of the performance to construction and control parameters, such as stiffness and proportional gain. The model was developed considering only the positioning movements of the machine, when large movements and velocities are required. The paper discusses the modelling of the machine and the results obtained in a multicriteria optimisation process that considers positioning error, energy consumption and axes promptness.