While dealing with sub-micrometric precision robots, all the events that can deform the robot structure or change its physics proprieties cause a loss of accuracy. In this paper we will focus on two significant issues: the first is the thermal changes acting on the robot and its environment, the second is the deformations caused by the cutting-forces generated during the robot usage. We describe a strategy to measure the deformations caused by those two effects and we propose a calibration procedure to compensate them in real-time.