Akira Kyusojin

Study on mirror surface grinding of die steel by using ultrasonically assisted diamond tools

This paper describes Ultrasonically Assisted Grinding (USG) to obtain a glossy surface quickly and precisely. In this research, diamond electroplated tools perform grinding experiments on a 3D milling machine equipped with an ultrasonic spindle system. Generally, diamond tools cannot cut ferrous materials because of the terrible wear due to diffusion of carbon into the bulk and chips. In USG temperature rising of tool abrasive is prevented due to discontinuous contact between tool and workpiece by periodical vibration. So, ultrasonically assisted diamond grinding can make fine surface (roughness Rz is 0.4-0.84 µm) of die steel, without severe tool wear. Effects of tool feed rate, radial depth of cut and axial depth of cut on the ground surface were investigated.

Development of a new lapping method for high precision ball screw (1st report)-feasibility study of a prototyped lapping tool for automatic lapping process

Ball screws are being lapped as a finishing process to improve the travel variation, drunkenness and surface finish in order to provide high precision requirements in various mechanical applications. However, the existing manufacturing method is very labor intensive that needs a highly skilled machinist to perform the hand lapping operations using the conventional laps which have two or three slits. These types of lap cannot eliminate and improve the special components of drunkenness such as ellipsoidal, triangular and other polygonal cross sections. This paper presents a new lapping method to determine the technical and operational feasibility of a prototyped lapping tool with the combination of a flexible lap and polyurethane elastomer which can be mounted in the vertical-type automatic lapping machine. This new type lapping tool with six slits, is especially designed which each section can move in radial direction wherein the uniform lapping pressure is applied on the test piece from six directions. Based on experimental results, it showed that the travel variation was greatly reduced along with drunkenness and lapping time.

Effects of Cutting Edge Truncation on Ultrasonically Assisted Grinding

High precision mold grinding technique to obtain mirror surface is required which realizes minimization or omission of final polishing by skilled workers. In the previous reports, ultrasonically diamond grinding experiments were carried out to confirm ultrasonically oscillation effect for die steel face grinding. Mirror surface was obtained successfully and little abrasive worn out was found. In the above technique, the cutting edge shape of a tool affects the ground surface resulting from transcription of cutting edge. In other words, cutting edge truncation of grinding tool is required to be smooth and glossy surface. This paper describes the cutting edge truncation of diamond electroplated tools which are used in ultrasonically assisted grinding. Experiments were carried out to confirm truncation effects on the ground surface and grinding force. It was confirmed that cutting edge truncation is effective method to obtain mirror surface and excessive truncation causes large grinding force and chattering.

New method of best-fitting on curved surface

With the coordinates measuring machine the measured points are obtained as a series of points consist of the original feature and the deviations caused by misalignment i. e. translated deviation and angular deviation. To evaluate the form deviation accurately it is required to best-fit the measured feature to the ideal feature. Conventional best-fitting has been done to minimize the sum of squares of deviations between measured feature and ideal feature by translating and rotating the measured feature. It is possible for the curved line but too difficult for the curved surface. This paper gives a new method of best-fitting using datums which minimize the sum of squares in its normal direction. The datum is defined as straight line for the curved line and plane for the curved surface. When the datum of measured feature is coincided with that of the ideal feature the deviations caused by misslignment are eliminated. In order to confirm the reliability of this method computer simulations and practical measurements were made. Then close agreement was obtained. Key words: coordinate measuring machine best-fitting curved surface datum method of least-squares form deviation software on the measurement accuracy y C) - Measured feature . /Ideal feature -I. Fig. 1 Conventional bestfitting method Ideal Measured feature feature eviation a) curved line Fig. 2 Designation of form deviation 54 / SPIE Vol. 2101 Measurement Technology and Intelligent Instruments (1993) b) curved surface

High precision lapping for polygonal holes

Abstract Lapping has been used as a finishing method to improve the roundness of shafts and holes. This paper introduces two methods for the finishing of polygonal holes whose shapes are ellipsoidal, three-lobed, four-lobed, and so on. One method is the “regular polygonal lap” in which the amplitude of the desired Fourier component of the out-of-roundness is kept constant and the other components are decreased. The other is the “tripod lap,” which can increase the amplitude of any Fourier component using special types of lapping tools produced by applying the “tripod roundness measuring method.” Based on a theoretical analysis, this study shows that any component of the out-of-roundness can be increased by using the new tripod lap method.

Development of precise cylindrical grinding by ball centres—contact stiffness between ball and centre hole

Abstract In high precision cylindrical grinding it is cutomary to support the workpiece with dead-centres. Then, the geometrical deviations of cone centres and centre holes, and their misalignments have an influence on the roundness of ground surfaces. It is known that the misalignments and geometrical deviations of centre holes do not influence the roundness of ground surfaces with the accurate and inexpensive steel balls in place of cone centres. Few reports, however, are found which are concerned with the characteristics of the ball centres. In this paper, experiments on the axial and radial stiffness were performed, at the contact parts between balls and centre holes. The obtained main results are as follows. (1) The relationships between the elastic deformations and the loads exhibit hysteresis. (2) The axial and radial contact compliances are from 0.0025 to 0.006 μm N −1 . In the ball centres, the stiffness is smaller than that of the cone centres, but the variances of stiffness are smaller than these. (3) The stiffness decreases according to the increase of the circumferential waviness of centre holes, and to the decreases of ball diameter and Youngs modulus. (4) The ellipsoidal component of centre holes decreases the radial contact stiffness remarkably.

Comparison of cone-centre and ball-centre for roundness in cylindrical grinding

Abstract In high precision cylindrical grinding it is customary to support the workpliece with dead-centres. The workpiece is rotated as a guide to the points o

Motion error compensation of a mechanical contact spindle using a multi-degree-of-freedom micropositioning stage

A three-degree-of-freedom micropositioning stage has been developed for controlling spindle runout. The stage consists of three wedge-shaped plates and PZT-stacked actuators. This stage can expand to 6 degrees of freedom and moves precisely without a stick-slip effect because there is no friction. Moreover, this stage has high loading capacity and stiffness because most of the load is placed on actuators having high compressive strength. In a trial, a PI controller actuated the stage to decrease the runout of a ball-bearing spindle weighing 400N. As a result, radial and axial motion errors of the spindle mounted on the stage were decreased from 0.2μmto0.04μm.

Development of a new lapping method for high precision ball screw (2nd report): Design and experimental study of an automatic lapping machine with in-process torque monitoring system

Abstract This paper presents a new approach in lapping process in making appropriate condition to improve the manufacturing operations for ball screw. After grinding, high precision ball screw is lapped by highly skilled operators. These operators have the ability to control and maintain the lapping conditions by sensing the lapping torque manually. Prior to lapping process, the effective diameter must be measured to find out the effective threaded profile along the screw shaft. The section which has a large effective diameter will be primarily lapped wherein the lapping torque is high. The aim of this study is to establish a control scheme on the automatic lapping machine for high precision ball screw in both measuring and finishing process. A prototyped horizontal lapping machine with in-process torque monitoring system has been designed, built, and tested. This is to determine the relationship among lapping torque, effective diameter, and error on travel to establish the measurement system to control the finishing operations efficiently and eventually improve and eliminate the various sorts of error components in a ball screw. The experimental results showed that the new lapping method could adequately predict the effective diameter and error on travel by observing the lapping torque.

Optimization of Cutting Edge Truncation Depth for Ultrasonically Assisted Grinding to Finish Mirror Surface

High precision mold grinding technique to obtain mirror surface is required which realizes minimization or omission of final polishing by skilled workers. In the previous reports, ultrasonic diamond grinding experiments were carried out to confirm ultrasonic oscillation effect for die steel face grinding. Smooth and glossy surfaces were obtained successfully and little abrasive worn out was found. In the above techniques require cutting edge truncation because the cutting edge shape of a tool affects the ground surface resulting from transcription of cutting edge. This paper describes optimization techniques for the cutting edge truncation of diamond electroplated tools which are used in ultrasonically assisted grinding. Experiments were carried out to confirm truncation effects on the ground surface and grinding force. It was confirmed that roughness was proportional to inverse of thrust force. Minimum roughness in grinding conditions were estimated from the proportional diagrams. The minimum roughness shows limit of roughness on an each grinding condition.