Papers by Keyword: High Speed Spindle

Abstract: Instantaneous speed (IS) is of great significance of fault diagnosis and condition monitoring of the high speed spindle. In this paper, we propose a novel zoom synchrosqueezing transform (ZST) for IS estimation of the high speed spindle. Due to the limitation of the Heisenberg uncertainty principle, the conventional time-frequency analysis (TFA) methods cannot provide both good time and frequency resolution at the whole frequency region. Moreover, in most cases, the interested frequency component of a signal only locates in a narrow frequency region, so there is no need to analyze the signal in the whole frequency region. Different from conventional TFA methods, the proposed method arms to analyze the signal in a specific frequency region with both excellent time and frequency resolution so as to obtain accurate instantaneous frequency (IF) estimation results. The proposed ZST is an improvement of the synchrosqueezing wavelet transform (SWT) and consists of two steps, i.e., the frequency-shift operation and the partial zoom synchrosqueezing operation. The frequency-shift operation is to shift the interested frequency component from the lower frequency region to the higher frequency to obtain better time resolution. The partial zoom synchrosqueezing operation is conducted to analyze the shifted signal with excellent frequency resolution in a considered frequency region. Compared with SWT, the proposed method can provide satisfactory energy concentrated time-frequency representation (TFR) and accurate IF estimation results. Additionally, an application of the proposed ZST to the IS fluctuation estimation of a motorized spindle was conducted, and the result showed that the IS estimated by the proposed ZST can be used to detect the quality of the finished workpiece surface.

Abstract: Recently, there has been an increasing demand for miniaturization and multi-functionalization of electronic equipments due to the developments in information technology (IT). Thus, the miniaturization of printed wiring boards (PWBs) and fabrication of highly dense electrical circuit layers are needed to realize the miniaturization and densification of the semiconductor package PWBs. Micro-drilling technology has been attracing attention to machine the electronic micro-through holes with an ultra-high-speed spindle, more than 160 krpm. However, problems have emerged; the drill tool bends and suffers breakage in the drilling process and the heat damage around the drilled hole after a drilling process occurs due to the increase in the drilling aspect ratio between hole depth and diameter. In general, a step feed drilling method is considered an effective way to solve these problems. However, short stroke alternating motion in the spindle axis is needed to do the step drilling process and its motion causes various kinds of vibration. We constructed a machine tool with a novel counter balance mechanism in the spindle driving Z-axis and investigated a model to estimate a proper balance mass for the step drilling process. We compared the frequency response results from a proposed model with the experimental ones, and discussed a control on vibration due to the counter balance mechanism. The results demonstrate that a proposed vibration proof method was found to reduce the vibration in high-speed step-micro-drilling motion and to improve the drilled hole quality and the efficiency of micro-drilling process in the PWB manufacturing fields.

Abstract: Tool based mechanical micromachining technology is gaining importance in MEMS device fabrication because of its ability to machine 3D micro features on different engineering materials. This paper presents the development of tool based mechanical micromachining center with piezoactuated workpiece feeding system. A high speed spindle is used to rotate the micromilling/drilling tool at a speed of 12,000 to 60,000 rpm. A thermoelectric based liquid cooling system is developed to control the temperature of the high speed spindle at a set value. Along with the X-Y positioning system, the workpiece is also mounted on a piezoactuator to provide Z-axis motion during machining operation. An electrical continuity based tool-workpiece contact detection system is developed to overcome premature tool failure during initial tool registration with the workpiece. Based on the developed tool-workpiece contact sensor, an in-situ measurement system is developed to measure the micromachining depth. Experiments were conducted to measure the performance of spindle cooling system and in-situ measurement system.

Abstract: The performance of a high speed spindle is mainly attributed to the thermal behavior of spindle bearings. Hence, it is very significant to simulate the thermal behavior of spindle bearings. Finite element analysis is carried out for a typical high speed spindle by considering bearing and motor heat generation under various loading conditions to investigate the transient temperature rise of the spindle assembly. The influence of different cooling arrangements on the thermal behaviour of spindle bearings is then investigated with the objective of minimization of transient temperature fluctuations.

Abstract: High speed spindle is a multivariable and strong coupling complex system. In order to improve its dynamic response characteristics and control effectively, based on vector control, the high speed spindle needs to be decoupling first. Then neural network theory and BP algorithm are adopted to form a speed controller to adjust the rotational speed. In this controller, gradient searching technique is applied and the proportional and integral parameters are used as weight of neural network which is employed to adjust the corresponding control parameters. Therefore, a new model of high speed spindle is set up and simulated. The result of simulation indicates that the way combine the decoupling method and the speed controller based on neural network can track the rotational speed more accurate and promote the robustness of high speed spindle.

Abstract: Based on the internal model control theory and combined the structural characteristics of high speed spindle, the control method of high speed spindle is discussed. And the view of applying the double internal model control to high speed spindle is put forward. Then controllers of current, flux linkage and speed are designed. According to the double internal model control plan, its simulation model is set up. Simulation results indicate that the double internal model control has better dynamic response curve, shorter response time, higher steady state precision by comparing with the vector controller.

Abstract: Due to the structural characteristic, the dynamic performance of the high speed spindle is influenced by multi-coupled parameters. Conventional control method can’t attain the satisfied control result. So the view of internal model decoupling control of high speed motorized spindle is put forward, which can improve the performance of vector control system. In this paper, mathematical model based on internal model control of high speed spindle is set up. And voltage and current of stator are decoupled. At last, through simulation, it is proved that the method can improve the control effect and has better robustness, dynamic characteristic. Therefore, internal model decoupling control of high speed spindle is feasible and effective.

Abstract: High speed motorized spindle plays an important role in high speed grinding. However, for high-speed machining, the spindle system usually generates excessive vibration due to the high speed and large mass. The vibration transfers to the bed of grinding machine and affects the precision of machining. To analyze and control the vibration generated by the spindle system, this paper develops a dynamic model for the high-speed spindle system, and further analyzes the eccentricity and the mass of the spindle system which affects the amplitude of the vibration of the bed by producing the impulse. Based on the result of analysis, the vibration is finally controlled by modifying the structure of the shaft. After optimization, the amplitude of the vibration of the bed of reduces significantly to 0.046um, which was 0.056um before. In addition the eccentricity of the spindle is decrease by 0.1um.

Abstract: The dynamic characteristics of a hydrostatic and hydrodynamic journal bearing with two arrays of eight holes have been investigated theoretically by the three-dimensional Computational Fluid Dynamics (CFD) models with respect to equilibrium position. The various dynamic coefficients for design parameters, such as orifice diameter, length to diameter ratio, eccentricity ratio, supply pressure, and rotational speed, are analyzed systematically under the action of displacement disturbance and velocity disturbance which are considered by the User Definition Function (UDF) programs. Results show that the dynamic coefficients greatly affected by design parameters. The cross stiffness coefficients increase rapidly more than direct stiffness with an increase of length to diameter ratio and rotational speed. Conversely, the direct stiffness coefficients are larger than cross stiffness with an increase of supply pressure and eccentricity ratio. It indicates that the journal bearing with two arrays of eight holes is suitable for their applications to small diameter grinding spindle by the means of optimizing the operating parameters and the structural parameters in order to obtain a better dynamic characteristic.

Abstract: Temperature data and vibration acceleration signals of both ends of high-speed spindle in different speeds are gathered by the DHDAS dynamic signal testing analysis system when spindle is in the working status. And the own analysis software and MATLAB are applied to analyze it. Temperature curves and vibration displacement curves are obtained after real and effective information is extracted. It can provide the basis for the research and analysis of spindle performance. The experiment results show that the method is real-time, efficient and has strong anti-jamming capability and small error. It can perform effectively in high-speed spindle studies.