Papers by Keyword: Ultra-Precision Machine Tool

Abstract: This paper describes a development of a real-time position capturing method in which branched encoder signals are recorded in external data storage, to evaluate motion trajectories of the XYZ table on ultra-precision machine tool. The method allows the capturing with minimal modification to the machine: without any additional sensors. In the previous study we generated a non-axisymmetric aspherical optical element by XZC-axis simultaneous numerical controlled ultra-precision turning process with 2 μm form deviation, the reason of form accuracy degradation wasn’t identified. Using the developed system, motion accuracy of ultra-precision machine tool is confirmed. The machine tool moves along circular trajectory in three coordinate planes (XY, YZ and ZX) respectively. The rotation direction of circle is set clock wise and counter clock wise. The circle processing interpolation command by linear interpolation control code and circular interpolation control code. The results showed the effectiveness of the proposed method for performance evaluations of machine tools, by revealing the influence of trajectory parameters on the magnitudes of quadrant protrusions.

Abstract: In order to improve the positioning resolution of the tool adapter on ultra-precision machine tool for KDP crystals, this paper presents a new piezo tool actuator. First, a new flexible membrane structure is designed after considering the characteristics of the machine tool for KDP crystals. Then, its detailed structural dimension is determined by finite element method. Finally, the piezo tool actuator is machined based on designs and its performance data is obtained by experiments. Experimental results indicate that its positioning resolution is superior to 0.5μm and its stroke reaches 4.7μm, which can meet the requirements of ultra-precision machine tool for KDP crystals.

Abstract: Numerical optimization method is increasingly applied into the design of machine tools so as to improve their performance. This paper employs Monte Carlo optimization method to predict and reduce the errors of ultra-precision machine tools in term of motion errors between cutting tool and workpiece closely associated with machine processing of ultra-precision machine tools. Using a quite different origin position of location coordinate system from traditional in that every ideal frame on current body is coincided with the reference actual one on the adjacent body, the motion errors are expressed in homogeneous matrix defined with adjacent bodies’ residuals in multi-body system analysis. This expression clearly shows that the final position errors are decided by the motion accuracy of the guideline, and gesture errors are affected by accuracy of the spindle assembly. With geometric errors extracted from the matrix, a new optimization method of error allocation is presented to maximize the machine precision by reasonable distribution of tolerances key parts. Using variables intimately related to motion errors and under constrained by cost, optimization model is established, then it is solved with Monte Carlo simulation method to compute top ten key factors contributed to errors and obtain distribution probabilities of both position error and gesture error. Case study formulated is reported to illustrate the method proposed and to evaluate its effectiveness.

Abstract: Ultra-precision machine tools is an important machinery equipment to implement ultra-precision machining. Current development and the trend of the ultra-precision machine tools was analyzed. The factors influencing machining accuracy were pointed out from the viewpoint of system. Some suggestions were put forward on the domestic development and research of the ultra-precision machine tools.

Abstract: In recent years, ultraprecision micromachining technology draws wide attention. In particular, multi-axis control ultraprecision machine tools are playing an important role in producing complicated microparts made of a variety of materials. In addition, CAM software is also an essential element to control these machine tools. The paper deals not only with the current state of multi-axis control ultraprecision machine tools but also with the manufacture of two workpieces consisting of complicated shapes by means of micromilling.

Abstract: Electrical and magnetic characteristics of motorized spindles have a great effect on machining quality of ultra-precision machine tools. Bad characteristics will result in significant heat losses, low efficiency and large vibration. Study on optimizing electrical and magnetic characteristics of an inverter-fed induction motor is presented in this paper. A method of optimization design of an inverter-fed induction motor is given. The method is used to design a motor used for an ultra-precision machine tool motorized spindle. By comparing the optimal design with the traditional one, it shows that the total electrical and magnetic heat losses are obviously decreased and the efficiency can be improved.

Abstract: Ultra precision machine tools are used in nano machining technology. Two main assemblies creating rotational and linear motion, called air spindle and linear air table are used in these machines. The linear air table has been simulated experimentally like a linear air bearing. This bearing moves in the main direction, X, while it has straightness error motions in Y and Z directions. The error values vary due to different parameters. This investigation deals with the influential parameters and their proportion in the error value. As far as the two mating surfaces are separated by a thin layer of pressurized air, the air pressure, location and amount of external load, are some of the parameters which have been studied. Results show that the more air pressure, the more stability and stiffer table. There will be less error motions as well. The error amount is not the same in X and Y directions. Finally, in order to have linear stiffness, the optimum air pressure, external load, and load location have been decided.

Abstract: For ultraprecision machine tool of the next generation, two novel positioning devices are invented by the authors. The first positioning device of nanometer and sub-nanometer resolution with long stroke is the Twist-roller Friction Drive (TFD). For long stroke with 1nm of positioning resolution, the TFD is driven by a servomotor, and it is driven by a piezoelectric actuator for short stroke with 0.1nm of positioning resolution. The second positioning device of short stroke picometer resolution is an active aerostatic guideway employing the Active Inherent Restrictor (AIR). The stroke of the active aerostatic guideway is in the order of 0.1μm, however, the positioning resolution can be 50pm. These positioning devices are integrated into a tri-mode positioning system and each positioning mode is controlled by a numerical control system.

Abstract: Micro-structured optical components (MOCs) show great promise for offering an exciting new degree of freedom and flexibility to optical designers and producers. At present, these micro/miniature components are usually manufactured by large ultra-precision machine tools in tightly controlled environment and the cost of machining is thus very high. In this study, a novel machine with compact structure and flexibility was built, specially used for machining of the MOCs. The key points of the design are given. Fresnel lens, as an example of MOCs, was machined by this machine tool, and the result shows that the form accuracy of the machine tool is in the order of sub-micrometer.

Abstract: An ultra-precision machine is developed by Precision Engineering Research Institute of Harbin Institute of Technology to machine components made of KDP crystal with single point diamond fly cutting technique . A stable ultra-low speed feed of worktable is necessary in the machining process inasmuch as the KDP crystal components to be machined must be high form accuracy, low surface roughness and low surface waveness . This paper analyses the effect on speed stability and positioning accuracy under the control of semi-closed loop and full-closed loop based on the experimental data, and also present a compensating control algorithm of error disturbance feed-forward which enhances the stability of ultra-low speed motion of the semi-closed loop feed control servo system of the machine. The simulation results indicate that the values of the steadystate tracking error decreased to 1/10 after using compensating control algorithm. The P-V value of the aluminum specimen machined by the ultra-precision machine tool was 0.27 wavelengths.