Tomomi Yamaguchi

Thermo-Chemical Wear Mechanism of Diamond Tool in Machining of Ferrous Metals

Abstract To understand the wear mechanism of diamond tool in machining of ferrous metals, an erosion test simulating wear process and ab-initio molecular orbital calculation are carried out. The results of the tests and analyses show that the essential wear mechanism at the temperature higher than 1000K is the dissociation of carbon atoms on diamond surface due to the interaction with iron surface. The wear rate is controlled by the removal rate of dissociated carbon atoms from the tool-work interface such as diffusion into workpiece. At the temperature lower than 900K, the mechanism involves the removal of carbon atoms due to oxidization of diamond accompanied with deoxidization of iron oxide.

Mechanism of Cutting Edge Chipping and Its Suppression in Diamond Turning of Copper

This paper investigates the mechanism of cutting edge chipping in diamond turning of copper in terms of the change in Hertzian strength of diamond specimens subjected to thermal histories. The study suggests that the strength of diamond decreases as the result of the propagation of existing surface micro cracks caused by the thermo-chemical erosion of oxygen at the crack tips. The catalytic reaction involving copper is also shown to accelerate the crack propagation. Then, a cutting technique of reduced oxygen atmosphere is proposed to suppress the cutting edge chipping in diamond turning of copper over an extended cutting time.

Scientific Screening of Raw Diamond for an Ultraprecision Cutting Tool with High Durability

The wide scattering in tool life of natural mono-crystalline diamond tools is considered to depend on intrinsic crystalline defects due to nitrogen impurities in raw diamond. In this paper, the correlation was investigated between the amounts and types of the impurity evaluated by infrared absorption (IRA) and the crater wear and chipping resistances. As a result, diamonds including less total amount of impurity show larger wear resistance and that with larger amount of B2-aggregates show larger chipping resistance. This suggests that the inspection by IRA can be a useful method for screening of raw diamond for highly durable cutting tools.

ASSEMBLY SYSTEM BY USING PROTOTYPE OF ACTIVE FLEXIBLE FIXTURE

ABSTRACT Our goal is the development of fixture with the function of handling of various works with practicability in automated assembly system for job shop type production. This paper describes the “active flexible fixture (AFLEF)” on plane level as a prototype of the goal. The AFLEF is an active and practical fixture, and it can fix any work rigidly and position the work at a few millimeters to correct the position error after holding. It is multi-fingered hand type, but it is not more dexterous than general hands of this type but more practical than those. As results of the experiments in rigid fixing and short positioning, the fixture rigidity to external force was within about 0.031 mm/N and 0.88 deg./N·m and the maximum error in positioning of a fixed work at ±3.0 mm or ±3.0 deg. was within about 0.3 mm and 0.3 deg.

Highly responsive and stable flow control valve using a PZT transducer

Pneumatic actuators are widely used because they are lightweight and inexpensive. However, highly controllable devices for pneumatic actuators generally have large volume and low response and are heavy. We have developed the flow control valves that have highly controllable using PZT elements. These control valves can downsize the control valve with high response. Using a PZT transducer, we introduced a new mechanism of the control valve for stable continuous flow rate. In this report, we proposed a new mechanism to realize stable continuous flow with a PZT transducer. We designed prototype using a bolt-clamped Langevin transducer (BLT) and show the characteristics of the valve.

Small size pneumatic valve for smooth flow control using PZT vibrator

Pneumatic actuators have the potential to be downsized because they have simple structure. However, many control devices that can control pneumatic actuators continuously have large volume and weight. We have designed a flow-control valve driven by PZT vibrator. This control valve has small volume and low weight, and it can control air flow smoothly. This valve is suited to control small pneumatic actuators. The flow control valve that we propose uses resonance vibration with a PZT vibrator. The valve consists of an orifice plate, a PZT vibrator and iron particles that work as the poppet. From experimental flow quantity evaluation, this control valve controls air flow smoothly with low hysteresis at a large flow rate. In addition, this flow control valve achieves a maximum flow rate of 65 L/min under air pressure of 0.70 MPa. The results show that the valve has high controllability and can control a relatively large flow rate compared to its weight and size.

Application of the Active Flexible Fixture to a Peg-in-hole Task

This paper describes the application of prototype of the AFLEF to a peg-in–hole task. This AFLEF is an active fixture and can fix any hole-work and position the fixed work at short range. We have combined the prototype of it and a 1-DOF inserting device with the RCC device into a new assembly system for such assembly task as a peg-in-hole task. However, there are two problems to realize this task. One is the “incomplete contact condition,” and another is the modification of location of a hole-work to the insertion point. In this paper, in order to solve the former, the AFLEF has been newly equipped with two touch sensors to judge the contact condition and it can modify the contact condition to the complete contact. Moreover, in order to solve the latter, we propose the modification method without any vision sensor. In order to confirm the effectiveness of our proposing modifications of the contact condition and the hole-work’s location, we have tried a peg-in-hole task with the assembly unit. As a result of this trial, although it took a little long time to finish a task, a task has been realized without failure.

DEVELOPMENT OF A WELFARE ROBOT BASED ON RECS CONCEPT - TASK OF SETTING A MEAL ON THE TABLE -

ABSTRACT In this paper, a home robot is developed based on RECS (Robot Environment Compromise System) concept. This concept aims to share the technical difficulties with robot and environment. In other words, RECS modifies the environment in order that the robot task would be possible or easy. Among the various domestic tasks, setting a meal on the table is focused. This task comprises preparing a meal and loading tableware with meals to a tray at a kitchen, transporting this tray to the table, putting the tableware on the table, and pouring bottled drinks to cups on demand.

Development of Micro Cutting Device with Silicon Micro Tool

Abstract This paper describes a new cutting device by using a new tool for nanometer level cutting. This “Silicon Micro Tool” is a multi-edged tool like a grinding stone and consists of silicon micro pyramids, which are about a few hundred nanometers tall and formed on the wet anisotropic etching in the silicon fabrication process. The cutting device, which we have made as the prototype, is millimeter-sized self-moving device and can machine Al-Mg alloy plate by the silicon micro tool in nanometer level.

Development of Design Technology of Porous Superfinishing Stone Using Fractal Geometry (1st Report). Construction of Characteristic Equations Required for Design.

A common design technology of machine products is to verify whether an assumed physical structure correctly implements the specified function or not. In the case of porous superfinishing stones, however, the design technology depends on the trial manufacture and test. That very empirical way of designing is requiring urgently to discuss the engineered design. Therefore, the establishment of an integrated design procedure, from producing a preliminary drawing of stone structure in conformity to the specified cutting performance to quantifying the manufacturing parameters of the stone, has been intended. In this paper, the seemingly complex and irregular structures of the superfinishing stones have been described using fractal geometry which provides a geometric model for the stone structures at the same time. Further, the intrinsic parameter characterizing fractally the stone structure has been related experimentally to the manufacturing parameters and the cutting performance of the stones.