Feed Axis Research Articles

Compact configurations of hexagonal microstrip antennas

AbstractThis article proposes compact configurations of hexagonal microstrip antennas (HMSA). The hexagonal microstrip antenna is modified by shorting along the zero potential line, perpendicular to the feed axis resulting in shorted half‐hexagonal and quarter‐HMSA for the two feed configurations along X and Y axes. The fundamental principle is to keep the field distribution same so that the resonance frequency remains unaltered while achieving a compact footprint. The area reduces by a factor of four, for the quarter patch, while maintaining approximately the same resonance frequency. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:604–608, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27396

Multi-degree of freedom robust control of the CNC X-Y table PMSM-based feed-drive module

Multi-degree of freedom robust control of the CNC X-Y table PMSM-based feed-drive module The paper presents results of studies on linear synchronous motors controlled in CNC feed axes through an intelligent digital servodrive. The research includes a conceptual design of an open servodrive control system and identification of dynamic models of a test stand with an open CNC system. Advantages of robust control over the classic one are discussed. A hybrid predictive approach to robust control of milling machine X-Y table velocity is proposed and results of simulation tests are presented. was prepared during the work for the Ministry of Science and Higher Education grant number N N502 336936, (acronym for this project is M.A.R.I.N.E. multivariable hybrid ModulAR motIon coNtrollEr), while its main purpose is the development of new robust position/velocity model-based control system, as well as to introduce the measurement of the actual state into the switching algorithm between the locally synthesized controllers. Such switching increases the overall robustness of the machine tool feed-drive module. The paper is the extended version of material proposed in [10].

Highly Integrated Piezo-Hydraulic Feed Axis

Currently used micro-machines are mostly based on macro machine tool principles. This leads to an unfavorable ratio of build and work space and also to high moving masses in comparison to the workpiece mass. To address these disadvantages it is necessary to develop new approaches for micro machines, micro machine components and new kinematic chains especially adapted to the requirements of micromachining. Therefore a new feed unit is designed featuring a highly integrated piezo-hydraulic feed axis, a parallel kinematic and a millimeter based radar measurement system. In this paper the design approach and the characterization of the compact highly integrated piezo-hydraulic feed axis is presented.

A27 高精密部品・金型加工用立形マシニングセンタ「MP-46V」の開発と加工事例(OS1 最新工作機械(2))

This paper presents the development concept and new technologies adopted to the vertical machining center "MP-46V" for high-precision parts and dies/molds machining. In this machine, the rotational speed of the spindle and acceleration of feed axes are increased for reducing the machining time. Moreover, in order to minimize "Junction steps" the new spindle with the rotary shaft cooling system and the advanced Thermo-Friendly Concept for the spindle, "TAS-S" are adopted. In addition we introduce sample cases of dies/molds machining with "MP-46V".

NURBS Curve Design and CNC Machining Principle

Used fixed equal step cubic spline interpolation in non-circular machining, the influence of acceleration may be too strong to cause burns and vibration. To suppress the acceleration influence of feed axis, take cam grinding as an illustration, first derived acceleration and its change from the cubic spline function, then adopting the method of off-line fuzzy model logical reasoning combined with five points of three power smooth, obtained the modified variable interpolation time steps. The experiment results that the feed axis acceleration stability used fuzzy step cubic spline interpolations is much better than equal step spline in cam grinding under the same processing efficiency.

Fault diagnosis of a machine tool rotary axis based on a motor current test and the ensemble empirical mode decomposition method

Faults frequently occur in the rotary axis of machine tools due to their complicated drive mechanism. The machining accuracy and life time span will decline when there is a fault in the machine tool. Hence, it is necessary to develop a method to detect faults efficiently. In this article, a fault diagnosis method of the rotary axis of a computer numerical control (CNC) machine tool based on servo motor current analysis is proposed. A two-degree-of-freedom dynamic model of worm and worm gear is used in this study to analyse the relationship between the current signal and the fault of the rotary axis of the CNC machine tool. The ensemble empirical mode decomposition method is used as a self-adaptive low-pass filter to extract valuable information from the current signal. A number of experiments are carried out on a CNC machine tool which is in a fault state to validate the presented method. The result shows that the current of the servo motor contains enough information to detect the fault state of the feed axis of the machine tool. After being calculated by the dynamic model, the current signal clearly reveals the fluctuation of stiffness of the teeth which is caused by the fault of the rotary axis.

Development of Table-on-Table-Type Five-Axis Machining Center: New Structure and Basic Characteristics

The demand for five-axis machining centers has been increasing rapidly, as companies seek “intensive processes” and “high accuracy.” However, it is generally more difficult for five-axis machining centers to achieve the same or higher accuracy than three-axis machining centers since it is necessary to have two more rotary feed axes besides the three linear feed ones. Many kinds of five-axis machining centers with various structures have been developed to date; an analysis of the advantages and disadvantages of major five-axis machining center structures was done first. As a result of this analysis, this paper focuses on the “table-on-table type” five-axis machining center. It is capable of accuracy because of its wide range of rotation for the rotary axis and its advantages in the adjustment process of the axis. and this paper proposes a five-axis machining center which has this construction. Furthermore, a new high-speed, highaccuracy, “table-on-table type” of five-axis machining center which uses a direct-drive motor for the rotary axis and a driven center of gravity for the linear axis has been developed based on this concept, and its accuracy has been verified.

Temperature Variables Selection for Thermal Error Modeling of Heavy-Duty CNC Milling-Boring Machine Tools

One of the difficult issues in thermal error modeling is to select appropriate temperature variables. In this paper, two selection strategies are introduced to overcome this difficulty. After measuring the temperatures and thermal errors of a heavy-duty CNC milling-boring machine tool by a laser tracker, four temperature variables which are the foundation of thermal error modeling are selected for each feed axis from fifteen temperature variables according to major factor strategy and non-interrelated strategy.

Learning-based Accurate Compensation of 2x/y Tow-dimensional Circular Contour Error for Linear Feed Axes

To improve circular interpolation accuracy of 2x/y gantry linear feed axes,an error compensation methodology is focused on in the work.The technique consists of three parts: circular error measurement,evaluation and compensation.The causes of the error generation during the interpolation process and its compensation difficulties are discussed.Laser interferometer with dynamic precision measurement function is introduced to obtain the dual feed axis coordinate data during the process.The roundness error is evaluated through calculation of the data with least square roundness evaluation method.A model based on least square support vector regression(LS-SVR) approach is established to learn and recognize the rule of the error.With the support vectors derived from the learning process,the magnitude for error compensation is acquired through the real-time regression calculation.In addition,the compensation output control strategy is constructed and a corresponding system is developed to realize the online control process.To illustrate the procedure of the combination approach,an experiment is conducted on the self-construction linear axis feeding platform with the developed system.The data from the experiment show that the technique can compensate the interpolation circular error.As a result,the study finds 68.7 percent roundness accuracy improvement with the online compensation method.

2X/Y直线进给轴直线轮廓误差的学习补偿方法

To improve the linear contour accuracy of 2X/Y gantry linear feed axes,the research of the literature focuses on the straightness accuracy measurement,evaluation and error compensation of the axes.Firstly,the cause of linear contour error in interpolation process and its compensation complexity were analyzed for a 2X/Y gantry feed axis driven by linear motors.Then a learning algorithm based compensation method was applied to increase the contour accuracy for this type of gantry axis.In the method,2D time function of a laser interferometer was utilized to acquire real-time interpolation error data and least square method was taken to evaluate and determine the ideal linear equation.A model based on least square support vector regression technique was established to recognize the errors.With the support vectors from learning process,the real-time compensation values were acquired through the model regression calculation.Finally,the compensation output strategy and corresponding realization system were also proposed.To demonstrate the procedure of the proposed approach,an experiment was conducted on the self-construction 2X/Y axis feeding platform.The result shows that the combination technique can compensate the interpolation error and increase the straightness accuracy by 53%.

Advanced calculation of static and dynamic stiffness in mechatronic machine tools

Static and dynamic stiffness are essential in machine tool design. Especially for electro-mechanic driven controlled drives, methods for calculating these properties will be discussed. It will be shown how finite element models (FEM-models) can be used for correct calculation of the static stiffness of controlled feed axes without using a mechatronic model. Furthermore it will be shown, how to use a new compact form of mechatronic simulation model for improved determination of static and dynamic stiffness.

Implementation of control elements in FEM calculations of machine tools

In structural dynamic calculations of machine tools, coupled systems play a decisive role. The article shows the implementation of additional differential equations, representing the control, in a FEM environment on the example of ANSYS. Therefore, the existing cascade control, which is typical in machine tool feed axes, can be considered directly in the FEM environment. By merging into a macro, an element which is particularly easy to handle is created. The applications in analyses in the time- and frequency range are discussed in a couple of examples.

Evaluating the use phase energy requirements of a machine tool system

This paper has an energy consumption reduction perspective by considering alternative machining strategies and system components interactions translated into variable and constant power flows with respect to various use phase regimes of a machine tool system. The methodology is able to estimate the mechanical energy requirements of the spindle and feed axes with respect to 2.5D machining strategies by taking into account steady-state and transient regimes. In addition, the specific amount of fixed energy drawn by a machine was determined based on a careful monitoring of the energy share amongst the auxiliary equipment that supports the accomplishment of the machining tasks. The numerical results were experimentally validated and the good agreement between them led to the conclusion that the proposed methodology can be used effectively for the calculation of the total energy required by a machine tool system for the milling of a part. This enables a straightforward comparison of different milling part programs with respect to their energy consumption levels.

Control concept for piezo-based actuator-sensor-units for uniaxial vibration damping in machine tools

Additional piezo-based components in drive trains can significantly improve the dynamic behaviour of machine tools. In this article we present a piezo-based actuator-sensor-unit that is able to reduce uniaxial vibrations in ball screw driven feed axis of machine tools. A complex model of a feed axis including ASU was developed to design a controller. The control concept is based on the direct velocity feedback. A modular test bench was designed, assembled and investigated to verify the ASU’s suitability for different feed axis configurations. In conclusion, the results for the different configurations where evaluated regarding economical aspects.

Influences of oil additives on the wear behavior of ball screws

The lubrication in a tribosystem has a significant influence on the resulting friction and wear behavior. The spectrum of the used base oils for lubrication preparation increases continuously. That affects especially the use of environmentally friendly substances in order to save the environment. Regardless of the chemical origin, the lubrication systems should primarily take over the function of positive influencing of the friction and wear behavior. The ball screw as a central component of the machine tool feed axis transforms the rotational motions of the servo motor to a linear motion of the slide and takes over the fine positioning function in machine tools. According to the roller bearing lubrication specifications a grease or oil lubrication for ball screws is indispensable. The lifetime calculation is based on an elastohydrodynamic lubrication film. Within the research activities of the collaborative research center (CRC 442) ball screws with additived oils and nonadditived synthetic ester, which are developed within the collaborative research center, are tested on the test stand. The aim is to clarify the question, which influence the oil additives have on the wear behavior and preload loss in ball screws for machine tool applications. Investigations have clarified that oil additives have a significant influence on the preloading of the ball screws which are operated in the mixed friction area. The investigations of the axial rigidity as well as the investigations of the no-load torques clearly showed that oil additives cause a lower preload loss in ball screws compared to nonadditived oils.

Energy optimized jerk-decoupling technology for translatory feed axes

Dynamic feed axes for machine tools are usually optimized for high jerk rates. This, however, might lead to excitations of the machine frame due to reaction forces of the linear motor. This paper describes the development of a jerk-decoupled feed axis with an innovative guidance system and energy-optimized spring-damper-elements. An accomplished system simulation is based on an energy observer applied to accomplish the energy-optimal design of an example jerk-decoupled feed axis. The simulatory results are verified at a test bed using adjustable adaptronic components. A concluding verification proves the positive effects of this technology without negative effect on the accuracy.

Resonance frequency of hexagonal and half hexagonal microstrip antennas

AbstractClosed form expressions for the accurate calculation of the resonance frequency of a hexagonal and half hexagonal microstrip antennas, based on their equivalence with rectangular microstrip antenna, have been presented. These proposed empirical formulae have been validated using simulations and experiments. Design curves, for the input impedance variation along the feed axis, have been presented for hexagonal and half hexagonal patches for two feed positions. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 448–452, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24087

Monitoring of slowly progressing deterioration of computer numerical control machine axes

The feed axes of computer numerical control (CNC) grinding machine tools are among the most mechanically stressed components of machine tools owing to the high process forces and rough manufacturing environment which they encounter. The resulting wear and tear depends strongly on the product range and the manner of machine operation. To counteract a functional deficiency of these central machine units, the current usual approach is preventive maintenance. The manual inspection of feed axes is complex and time consuming. A complicating matter is that the deterioration normally progresses very slowly and depends on the position of the stress along the axis. Existing approaches to automated estimation of the ‘health status’ of feed axes do not take this factor into account. This paper presents a procedure that addresses this gap. During simple test routines, the drive current, axis position, and feed rate are recorded. With the help of additional machine data, characteristic values are computed directly at the computer of the human—machine interface (HMI). The results are then transferred to and stored on a database server at the machine manufacturer. This approach enables the service technician to trace the progression of the axes’ ‘health status’ over a long time. This approach makes it possible to detect trends in the characteristic values at an early point in time. This leads to a better planning of necessary maintenance actions adapted to the remaining lifetime of the wearing component.

Adaptronic gantry machine tool with piezoelectric actuator for active error compensation of structural oscillations at the tool centre point

In modern high dynamic gantry type machine tools rotary motors for feed axes have been replaced by linear direct motors. Thus, the limiting parameter in terms of the dynamic response is now the mechanical structure itself. Current design wisdom to improve the cutting accuracy is to increase the rigidity of essential machine components. This detrimentally results in either higher masses to be moved or sophisticated reinforcements being applied to the cross-arm or both. The adaptronic gantry concept proposed in this paper overcomes the need for stiffer machine structures but incorporates a light weight cross-arm. The occurring cross-arm’s structural oscillations are actively compensated by means of an additional piezo actuator that is attached between the cutting head, that moves along the cross-arm, and the tool. The piezo command is obtained from an observer that utilises additionally sensed acceleration information.

A12 テーパコーン加工動作の軌跡誤差を用いた5軸制御工作機械の幾何誤差同定方法(OS-1 最新工作機械(3))

Cone frustum machining with simultaneous five-axis control, which is prescribed in NAS979, is one of the most general method for the accuracy test of five-axis controlled machine tool. And instead of the machining, the measurement with double ball bar device has been proposed. In our previous work, we showed that the geometric errors between feed axes in five-axis controlled machine tool influence the accuracy of machined cone frustum, and it depends on the location, apex angle, tilt angle or diameter of the cone frustum. It indicates that all geometric errors might be identified with the profiles of cone frustum. In this paper, we suggest a method to identify the geometric errors in five-axis controlled machine tool with tilting table using the multiple motion trajectories of cone frustum machining measured by double ball bar device.