The EMRP Project 'Thermal design and dimensional drift'

摘要

With current trends in precision engineering demand of higher accuracies for industrial high-end production and measurement equipment, temperature effects and time-dependent drift, are a serious limitation for achievable system performance. These limitations can be stretched by a more insensitive design of machine components and active compensation of thermal gradients caused by heat sources. For insensitive machine design knowledge and control of medium to long-term dimensional drift and thermal properties are required. The study of dimensional drift including aging and thermal expansion using interferometric methods [1] is well known, but will also be utilized here for the investigation of joints, sensors and actors. For the determination of influences of forces, indentation methods will be used with a focus on the creep of materials and the thermal dependence of hardness [2]. The influence of heat sources on precision engineering instruments can be reduced by improved placement as well as by use of appropriate materials, which can be effectively supported by thermal modelling [3]. Even more compensation can be achieved by active thermal control of machine subsystems. Cooling elements with low vibrational and thermal backlash has to be developed and thermal modelling will allow for an improved model based control. Reliable and low maintenance temperature measurement [4] is a key for active thermal control. Current state of the art temperature measurement equipment needs regular re-calibration, which will be addressed by the development of a miniaturized fixed point cell for use near 20 °C for in place calibration of platinum thermometers with respect to the temperature scale 1TS90 [5]. The use of thermocouples is a promising choice for the measurement and even more for the active control of temperature gradients. The characteristic of different thermocouple devices in dependence of temperature differences and mounting conditions will be investigated.