Hydrostatic Slideways Research Articles

Three Dimensional Fluid Simulation and Experimental Verification of Hydrostatic Guideway for Large Rotary Worktable

Relying on the major national science and technology special project, this study used the table 12 fan-shaped oil cavity hydrostatic guideway of CKS5235 CNC vertical lathe worktable, applied FLUENT processing software GAMBIT modeling and mesh generation the flow static pressure guide film, setting boundary conditions. Used simulation software FLUENT numerical analysis the dynamic process of hydrostatic slideway oil film flow field with temperature field and the basic bearing capacity, the effectiveness of three dimensional fluid simulation method for hydrostatic guideway in engineering design is verified by experiments. According to the results of three-dimensional fluid simulation, the hydrostatic guide structure of CKS5235 CNC vertical lathe worktable has been improved, achieve the speed performance improvement of the table, complete the major special technical research and acceptance.

Numerical modelling of the flow in the annular multi-recess hydrostatic thrust bearing using CFD methods

The current research of hydrostatic bearings and hydrostatic slide-ways is far from being over. The topic is constantly evolving, creating new geometries of the sliding bearings, developing new types of friction materials and lubricants. The control elements of hydraulic mechanisms that serve to regulation of the hydrostatic bearings tipping are still in progress. Almost every application has different requirements for the bearings, whether in terms of loading capacity, speed rotation, and also the price. All these aspects should be included in the design of hydrostatic thrust bearings. Thanks to great advances in the development of computer technology and software for numerical modelling, we can simulate real movement of viscous fluids. To create a numerical model of hydrostatic thrust bearing, Ansys Fluent 14.0 software package has been applied. The article describes the basic methods of numerical modelling of the given problem and evaluates the pressure field and the loading capacity of annular multi-recess hydrostatic thrust bearing and its dependence on the change in static pressure.

Time–frequency analysis for ultrasonic measurement of liquid-layer thickness

Lubricant film thickness is one of the most important parameters to indicate the operating condition of machine elements, such as mechanical seals and hydrostatic slideway. When ultrasonic waves illuminate the interfaces between the substrates and a lubricant film, it will be reflected due to the change of the material properties at the interfaces. These reflected ultrasonic waves contain information about film thickness. In this paper, wavelet transform modulus maximum method was explored to extract the film thickness from its reflection ultrasonic signals. The performance of different wavelet functions within various scale factors was experimentally investigated, and the optimal wavelet function with the optimal scale factor was pointed out. It has been shown that the measurement error is less than 5% when the thickness of liquid layer is within a certain range.

Integrated Design of Hydrostatic Slideway Driven System

In order to achieve the design of mechatronic system rapidly, an integrated design process is used for a hydrostatic slideway driven by linear motor. Control model of the linear motor and FE model of the slideway carriage are established, besides, force analysis of the carriage and relevant optimization are carried out. Software Simulink is used to simulate the linear feeding system. Subsequently, the advantages of the integrated design compared with traditional method are analyzed. This study could provide important insights for the design of the hydrostatic slideway with linear motor driven system.

Performance Analysis of Hydrostatic Slideways Systems with Different Types of Restrictors

In fluid hydrostatic closed-type slideways systems, restrictor will take an important role of improving the performance of machine tools. Generally there are four types of restrictors to be utilized, capillary type, orifice type, slot type, and dynamic feedback type. The general oil film stiffness model of different types of restrictors was constructed and the characteristics of different types of restrictors are analyzed and compared. The analysis results demonstrated that the stiffness of restrictors depend on the geometry and structure parameters, and according to the analysis results the all types of restrictors can be designed optimally.

Simulation and Experimental Research of the Grinder'S Wheelhead Dynamics

In this paper we present a simulation based on the physical model of a cylindrical, plunge grinder with hydrostatic slideways and hydrostatic bearings of a grinding wheel spindle. The simulation was carried out in order to check the influence of the grinding process on the forced vibration damping of the wheelhead. The experimental research was undertaken to verify the idea of the damping facility of the grinding process. The results of the experiments and the simulation were used to draw the final conclusions.

The mathematical description of dynamics of the cylindrical grinder

In this paper the physical model of a cylindrical plunge grinder with hydrostatic slideways and hydrostatic bearings for the grinding wheel spindle has been presented. The model was created in order to check the influence of the grinding process on forced vibration damping of the grinding wheel headstock. The mathematical description of the model and the stages of the experimental and analytical derivation of its parameters have been included in the paper.

The influence of grinding process on forced vibration damping in headstock of grinding wheel of cylindrical grinder

The paper describes theoretical analysis of dynamics of system: machine–tool–workpiece for cylindrical plunge grinding. The functional as well as mathematical model of grinder equipped with hydrostatic bearing of grinding wheel spindle and hydrostatic slideways has been presented in the paper. Simulations based on that model allow qualitative investigation of grinding force characteristics and its influence on forced vibrations in grinder. Results of simulation supported the thesis, that grinding force significantly influences the forced vibration damping of headstock of grinding wheel.

荷重によらず摩擦力一定な空気半浮上すべり面の設計法

The hydrodynamic slideway, which is often adopted for machine tools, usually possesses a large friction and induces a lost motion (backlash), hence the positioning and contouring accuracies are decreased. These defects can be overcome if the hydrostatic slide way is adopted, but it is inevitable that the stiffness along the feed direction will become low and the manufacturing cost will increase. The authors have revealed that a proper amount of solid friction should work between the sliding faces in order to satisfy both the accuracy and the stiffness, and it is very important from the point of consistency of performance that the amount of the above frictional force does not vary with an applied vertical load and a given feed rate. The present paper uses the Half-floating Slideway which has a composite property between the hydrodynamic and the hydrostatic slideways. Air is supplied as a lubricant, hence a variation of hydrodynamic effect with the feed can be avoided. Furthermore, a load compensation mechanism which changes supply pressure automatically corresponding to the variation of the vertical load is provided. The principle and the design procedure of these slideways are reported.

Dynamic Stiffness of Machine Tool Feed Driving System : 2nd Report, Experimental Evaluation on the Damping Capacity of Slideway

A feed driving model facilitated with a hydrodynamic, a half-floating, or a hydrostatic slideway was prepared and its dynamic stiffness was measured under the condition that when a Coulomb friction acted on the slideway, an exciting force, and a feed rate were varied. It is verified that the previous theory can well explain the experiment, that is, the dynamic stiffness can be estimated quantitatively if an equivalent damping capacity is evaluated from the Coulomb friction during vibration, and that, for a practical application, this friction can be replaced by the one somewhat smaller than the steady friction force measured for a steady feed.

Fifth Paper: The Design of Machining Centres

Design features of a range of machining centres are described. A four-axis horizontal machining centre with a 1 1/2 m diameter table is described in detail. It is fitted with a 60-station tool changer and automatic pallet loading and uses hydrostatic slideway and spindle bearings. The elements of the machine are of modular design and other configurations and sizes of machine can be made from the same modules.

DETERMINATION OF OPTIMUM CONDITIONS OF CAPILLARY COMPENSATED HYDROSTATIC SLIDEWAYS*

Abstract This paper presents the determination of the greatest stiffness and least power consumption of capillary compensated hydrostatic slideways, prestressed and non-prestressed, respectively. Design equations for determining the optimum values of supply pressure, pocket pressure, length of free-periphery of slideways rim, thickness of land of slideways rim, viscosity, capillary-discharge coefficient and power consumption are determined, other variables held constant. The paper determines the operative conditions which correspond strictly or approximately to the conditions assumed in the equations. Diagrams show the effect of discrepancy between optimum and actual conditions on the stiffness of slideways.

Floating and Bouncing on Oil

IN A HYDROSTATIC thrust bearing the two flat metal bearing surfaces are held apart by a film of oil two or three thousandths of an inch thick, the oil film being maintained from a pressurized supply. In this way coefficients of friction between the bearing surfaces can be reduced to very low values, usually less than 0.00005. The Mount Palomar telescope weighing nearly 500 tons is supported on three hydrostatic pads and the whole system can be rotated by a 1/12 h.p. clock motor. In machine tool practice the use of hydrostatic slideways enables the moving member to move along straight lines to a tolerance of a few millionths of an inch. The author has been concerned with the design of hydrostatic thrust bearings for machine tool applications. In this case it is not enough to design a bearing merely to lift a given weight, but the bearing must be designed so that its stiffness (i.e. load per unit deflection, as for a simple spring) is adequate and so that the damping ratio of the oil film is nearly critical. The Mount Palomar bearings have theoretically no stiffness at all, and would be quite unsuitable for machine tool applications, or for any other application where the amount of deflection under load is important or where there is a possibility of vibrattion occurring. In this article the author will show how the stiffness and damping characteristics of hydrostatic thrust bearings can easily be found.