The positioning error of ultra-precision machine tools is the primary factor directly affecting the machining accuracy. It mainly depends on the machine tools guide. And its variation trend contains ...the same inertia as that of the machine tools movement. The variation trend of the positioning error is the derivative of a function fitted with the positioning errors of three adjacent testing points. The variation trends function is fitted with the variation trend of many points. The model of positioning error is the integral of the variation trends function. Because the variation trend of positioning error has certain inertia, the model of positioning error which is obtained in this way is more precise and more reliable than error function model which is directly fitted with limited discrete data.
Recently, the ultra-precision parts have become essential in many areas of advanced technology, including medical equipment, aircraft equipment, optical equipment and so on. These ultra-precision ...parts are required to have a high surface quality. Therefore, further precise machining and motion accuracy are required for the ultra-precision machine tools that machine these parts. Thus, the water-driven spindle, which is equipped with water hydrostatic bearings and a water-driven mechanism, was developed for ultra-precision machine tools. This spindle has higher stiffness than a spindle supported by aerostatic bearings. However, the heat generation due to fluid viscosity occurs at the bearings. If the temperature of each part in the spindle changes, undesirable deformation of the parts will occur. Deformation of the spindle during the machining process will then degrade the machining accuracy. In contrast, the water-driven spindle uses water as a lubricating fluid. Furthermore, water flow is supplied into the spindle in order to generate the driving power. Therefore, the water flow is an effective cooling medium for the water-driven spindle. Water cooling can be used to improve the thermal stability of the spindle because water has higher thermal conductivity and higher specific heat. In the present paper, the thermal stability of the water driven spindle is investigated experimentally. As a preliminary step, the changes in temperature of the water flow and the outer surface of the spindle are measured experimentally during spindle rotation at various rotational speeds. Furthermore, the influence of the power loss during spindle rotation on the temperature change of the water flow is investigated through calculations and experiments.
V-groove structure is extensively used for planar optical-fiber alignment, and its quality is critical to the functionality of the fiber connector. The core pitch of v-groove structure is the most ...important machining parameter, which determines the v-groove quality. And its machining precision is dominated by the machine tool motion precision in the z-axis direction. Six single kinematic errors derived from the multi-body system theory are the main factors affecting the accuracy of the machine tool motion in the z-axis direction. Therefore, this paper presents a single kinematic errors accurate fitting methodology for the micro v-groove machine tools. A function is fitted with a set of data using the existing fitting method and verified by another set of data measured at other testing points. Each set of test points have the same intervals, but their starting points are different from each other. The fitted function is constantly upgraded in the process of the verification. And the accurate fitted function is finally obtained by the recycling verification process. The results show that the accurate fitting method is effective and practical.
This paper discusses the resistance force, including the friction force, of guideways used in ultra-precision machine tools. Among linear rolling guideways, V-V roller guideways enable particularly ...high motion accuracy. In this study, the resistance force of the V-V roller guideways is measured to investigate its fluctuation behavior. The feed drive system consists of V-V roller guideways and linear motors. The resistance force is calculated from the motor current feedback of the linear motor. The experimental results confirmed that the resistance force remaining after table motion, the so-called stick friction force, is small with the V-V roller guideways. Similar to the resistance force of general linear rolling guideways, the resistance force is dependent on the Herzian contact area at the start of motion. Compared with general linear rolling guideways, the variation of the resistance force is small with V-V roller guideways.
This study discuss the dynamic stiffness of guideways of a ultra-precision machine tools. V-V roller guideways have been employed in ultra-precision machine tools, as they can provide very smooth ...motion and good straightness. Recently, general linear ball guideways are also employed in ultra-precision machine tools. In the design of the machines, it is necessary to obtain the stiffness of these guideways. Therefore an identification method of the guideway stiffness is verified in this paper. In this method, the guideway stiffness is identified from the natural frequency of the moving body. First, the impact test is carried out for an ultra-precision machine tool to obtain the vibration mode of its moving body. Next, a simple vibration model is developed based on the obtained vibration mode to identify the equivalent stiffness of the guideways. Then, the static stiffness of the guideways is measured for the verification of the identified equivalent stiffness. For further verification, natural frequencies of the moving body are calculated by FEM with the identified equivalent stiffness and compared with the measured natural frequencies. The identified equivalent stiffness agreed well with the measured static stiffness. Furthermore, the natural frequencies were calculated almost correctly with the identified equivalent stiffness.
The goal of this research is to develop a multi-functional ultra precision machine to generate micro features on large surfaces. Design and characteristic analyses of our machine are presented. The ...analyses include its structural analysis and accuracy tests. Each axis of the developed machine was corrected and/or compensated from accuracy tests enough to generate grooves on workpieces with a less than 10 µm pitch size. After compensation, the 2-dimension position error between X-axis and Y-axis was reduced to 1.4 µm for a 400×400 mm
2
surface. From a 24 hours relative thermal displacement test between Y-axis and Z-axis, the machine showed a stable thermal displacement which was measured to be less than 1 µm. From groove machining tests, our machine could successfully generate 5 µm and 10 µm pitch grooves and showed a stable micro machining characteristics. From this research, we can conclude that the developed machine has mechanical characteristics enough to generate less than 10 µm pitch grooves on a 400×400 mm
2
surface.
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