Tojiro Aoyama

Development of Fixture Devices for Thin and Compliant Workpieces

Fixturing of thin and compliant workpieces is in many ways technically more demanding than fixturing of stiff workpieces. Nowadays, thin and compliant workpieces, e.g., electrical parts containing semiconductor substrates must be supported with uniform contact force in order to assure high positioning accuracy. In particular, workpiece supporters must suppress workpiece deformation during machining. This study presents new fixture devices that can support thin and compliant workpieces securely and minimize the deformation due to the machining force. A low melting temperature alloy was used in the support structure to fulfill the required functions with simple structure.

Development of a Mixture Supply System for Machining with Minimal Quantity Lubrication

Abstract The minimal quantity lubrication (MQL) technique is used in cutting processes in order to reduce the environmental pollution caused by cooling lubricants. However, there can be problems with the MQL technique in high-speed machining. In high-speed machining, a spindle-through coolant supply method can effectively supply an oil mist to the cutting area. However, the centrifugal force from the high-speed rotation of the spindle causes the oil mist to separate. As a result, there is a decrease in the oil mist supplied to the cutting area. In this study, a new oil-mist supply mechanism was developed and installed in a high-speed spindle system. The performance of this proposed mechanism was evaluated by numerical simulation and an actual cutting test.

Numerical and experimental analysis for the small vibration of aerostatic guideways

Aerostatic guideways have been used in many fields and are absolutely essential for ultraprecision machining. Recently, with increasing demand for ultraprecision devices, the accuracy of 1nm or less has become necessary. On the other hand, conventional aerostatic guideways are not designed considering the influence of small vibration which occurs by supplying air. This vibration is hampering the improvement in accuracy. In this study, a new design of the outlet of orifice restrictors is proposed from the result of numerical analysis and its effect is examined numerically and experimentally. The mechanism for the occurrence of small vibration is analyzed and the methods to suppress the small vibration are proposed.

Application of electrorheological fluid dampers to machine tool elements

Abstract Electrorheological fluids (ERF) are colloidal suspension whose apparent viscosity is variable in response to the strength of an electric field. In this paper, the application of electrorheological fluids to machine tool elements is proposed. The dynamic characteristics of machine tool table systems with linear motion rolling element bearings are improved by using an ERF film damper. A high damping force can be induced by increasing the ERF viscosity when the table is being moved during machining and the viscosity can be reduced when the table is being moved rapidly so providing less viscous drag. The performance of the hydrostatic bearing can be controlled by using ERF instead of hydraulic oil. The bearing clearance and load carrying capacity can be controlled by adjusting the intensity of the applied electric field.

Performances of HSK tool interfaces under high rotational speed

Abstract The static and dynamic performance of the HSK tool interface is investigated at high rotational speed, including an experimental and numerical analysis of the influence of spindle speed on the radial stiffness of the tool interface. The behavior of the flange and taper contact of the HSK tool interface is simulated by means of the finite element method. The performance of a 7/24 tapered tool interface is also evaluated using the same spindle system, and the advantages of using HSK tool interfaces in machining are discussed.

BASIC PROPERTIES OF GEL-STRUCTURED ELECTRO-RHEOLOGICAL FLUIDS

Electra-rheological fluids (ERFs) are composed of a functional fluid and colloidal suspension. Their rheological properties vary rapidly and reversibly with the applied electric field intensity. ERFs are mixtures of nonconductive silicone oil and inorganic/organic composite electro-rheological particles. Investigations into the properties of ERFs have led to remarkable advances in their performance in recent years. However, ERFs exhibit an undesirable property that obstructs the long-term use of ERF devices, namely the sedimentation and separation of ER particles from the silicone oil. The sedimentation of ER particles reduces the electro-rheological effect. In order to suppress the sedimentation and thereby improve the performance of ERF devices, a new functional material called Gel Structured ERF (ERG) is developed and its basic properties are analyzed in this study. The ER particles are sustained in the gel component, and thus will not precipitate out. This suppresses the decrease in ER effect associated with precipitation. The developed ERG shows large shear stress variation in response to the applied electric field. This high performance of ERGs involves a different mechanism than that observed in ERFs. In order to elucidate the mechanism in ERGs, the behavior of ER particles was observed under an electric field. Conditions at the interface between the electrode and ERG were found to change rapidly in response to the applied electric field, resulting in the variation of shear force.

A computer simulation method for dynamic and stability analyses of air bearings

Abstract A computer simulation method for the dynamic and stability analyses of air bearings is proposed in this study. The general form of the time-dependent Reynolds equation, which includes the effects of high rotating speed, vibration and air supply, is studied. The finite element method is employed to obtain the numerical solution of the pressure distribution and the Galerkin weighted residual method is applied to discretize the Reynolds equation. To analyse the dynamics and stability of air bearings, the motion of the shaft supported by the bearing is simulated by a large computer and the Runge-Kutta method is employed to give an accurate description of the shafts motion. Some examples of simulated results are shown to confirm the applicability of the proposed method and the possibility of developing a computer-aided design system for air bearings.

Development of High-performance ERG based on the Principle of Electro-adhesive Effect

Electrorheological gel (ERG) is a novel functional elastomer, which has frictional and adhesive surface properties that vary according to the intensity of an applied electric field. This peculiar phenomenon is referred to as the electro-adhesive (EA) effect. The shear stress of ERG generated under an applied electric field is approximately 30-40 times higher than that of electrorheological fluids (ERF), due to its high adhesive strength. However, the generated EA effect of ERGs varies widely due to surface conditions, especially the density and distribution of ER particles at the surface. In order to stabilize and improve the performance of ERG, the electrical field-assisted molding process is proposed as a production method. In this process, the mixture solution including ERFs and gel agent is gelling under electric field. The principle of the EA effect is theoretically investigated and a high-performance ERG produced by the proposed process, in which ER particles are aligned densely at the surface, is developed and the performance is experimentally evaluated by surface observation and shear test, revealing a highly dense arrangement of ER particle at its surface and a higher shear stress twice that of conventional ERG.

Development of gel structured electrorheological fluids and their application for the precision clamping mechanism of aerostatic sliders

Abstract Electrorheological fluids (ERF) are functional fluids whose viscoelastic property varies according to the intensity of the applied electric field. The disadvantages of ERF are the sedimentation of ER particles and the requirement of a seal mechanism. In order to solve these problems, gel structured electrorheological fluids (ERG) are developed in this study. The basic characteristics of the ERG film are experimentally analyzed. The ERG is applied to the clamping mechanism of aerostatic slider. By using the ERG element, the aerostatic slider can be clamped with extremely low clamping force. The ERG clamp also serves as a variable damping element of aerostatic slider.

Development of gel-structured electro-rheological fluids and their application to mechanical damper elements

Electrorheological fluids (ERF) are functional fluids whose viscoelastic property varies according to the intensity of the applied electric field. The disadvantages of ERF are the sedimentation of ER particles and the requirement of seal mechanism. In order to solve these problems, gel structured electrorheological fluids ERF are developed in this study. The basic characteristics of ERF film is experimentally analyzed. Based on the results of basic analysis, the ERF was applied to the mechanical damper elements.