Hiromi Isobe

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.

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.

Ultrasonically Assisted Micro Drilling for Acrylic Resin μ-TAS

Recently, technologies for medical inspection have been increasing rapidly. In biomedical industry, a demand of Micro Total Analysis System (μ-TAS) has been growing which used in automatically inspection for chemical analysis. The μ-TAS have micro passageway which is constructed by many fine micro holes. Final polishing by skilled workers are carried out after drilling to obtain smooth surface of holes. Because new manufacturing technique is required instead of skilled workers, it increases productivity and cost performance of the μ-TAS. Drilling technique with low temperature environment around cutting edge is required to prevent heat crack or adhesion on holes surface, because acrylic resin heats sensitive material. In this study, ultrasonically assisted micro drilling technique is proposed to increase productivity of μ-TAS and quality of micro holes. Ultrasonically assisted machining has effective technique to improve machinability, e.g. reduce cutting force, increase chip removability and machined surface quality. This paper describes the cutting characteristics of ultrasonically assisted micro-drilling for acrylic resin to employ the μ-TAS manufacturing to solve above problems.

Experimental Verification of Machining Process of Ultrasonic Drilling

Drill processing of difficult-to-cut materials such as ceramics, hardened steel, glass and heat-resistant steel is widely required in the industrial world. Furthermore the drilling process becomes more and more difficult in the case of hole diameters less than one millimetre. In order to achieve the requirements for the drilling process, ultrasonically assisted machining is applicable. Ultrasonic vibration assisted machining techniques are suitable for machining difficult-to-cut materials precisely. However, the cutting process of ultrasonic drilling has not been clarified. It is difficult to observe directly the effect of vibration. The aim of this study is to observe the dynamic, instantaneous and micro cutting process. In this report, a high-speed camera with a polarized device, which is appropriately arranged, realized the visualization of the process of ultrasonic drilling based on photoelastic analysis. For conventional drilling, the stress distribution diagram showed that the intensive stress occurred in limited areas under the chisel because the chisel edge of the drill produces large plastic deformation. On the other hand, the ultrasonic drilling produced spread stress distribution and a stress boundary far away from the chisel. The photoelastic analysis showed the explicit difference of drilling processes.

Effects of Grinding Fluid Excited by Ultrasonic Vibration

Ultrasonic excited fluid has been researched for machining of hard-to-grind materials. Ultrasonic vibration is applied to grinding fluid by an ultrasonic oscillating comb-shape effecter with integrated nozzle. Grinding fluid discharges from a nozzle placed between the comb’s feet and passes through the vacant space between comb teeth. By this setup, flowing grinding fluid can be continuously excited by ultrasonic vibration. Based on the principle of an ultrasonic washing machine, impulsive force caused by cavitation bubble will reduce the adhesion of chips on the cutting face of grain and chip pockets. Some effects of ultrasonic excited grinding fluid have been recorded such as reducing grinding heat in the case of grinding for Titanium alloy and decreasing in grinding force, improving surface roughness in the case of grinding for Aluminum and stainless alloy. However, the reason of better grinding performance is still unknown. Therefore, experiments conducted with different type of grinding fluids with and without ultrasonic vibration are needed. Pure Titanium, which considered a hard-to-cut material, is chosen as work material. Grinding forces and grinding heat during grinding will be measured and evaluated to clarify the mechanism of ultrasonic excited grinding fluid.

Machinability Improvement on High Speed Ultrasonic Turning - The Effect of Tool Oscillating Direction and Tool Chip Shape

Ultrasonic cutting is a technique that can improve machinability such as fine surface, reduce tool worn out and etc. To improve processing speed of ultrasonic cutting is difficult due to the effects of tool oscillation are invalidated when cutting speed exceeds maximum tool oscillating velocity. In previous report, high speed principal direction ultrasonic turning experiments for stainless steel were carried out to improve processing speed and products quality. In ultrasonic turning, tool worn out and built up edge generation were reduced compare with ordinary turning. In this study, the effects of tool oscillating direction and tool chip shape for cutting properties of soft magnetic stainless steel were investigated. Cutting properties such as turned surface roughness, cutting force and ejected chip were compared.

Design of a positioning device using piezo element and investigation of a simple compensation method

Demand for miniaturized and higher integration of various optical and electronic elements has increased along with the development and implementation of information technology in recent years. Holographic optical elements, which are attracting attention in the field of optical elements, can satisfy these demands. For this study, a prototype precision positioning device of a dual servo mechanism was designed and produced for microtrench processing. The coarse motion actuator incorporates a ball screw and a linear guide. Also, a laminated type piezoelectric actuator is used as a micro-motion actuator. A laser length measuring device was used to evaluate the precision positioning of the device. This study also examined a method for compensation of hysteresis by polynomial function fitted to displacement-voltage data and displacement characteristics of the piezoelectric element. Furthermore, for decreasing voltage, compensation by the lowest ordered second-order polynomial function must be preferred because no great difference in compensation performance was recognized in compensation by three different polynomials.