Toru Tachibana

Determination of an Optimum Geometrical Arrangement of Workpiece in the Ultrasonic Elliptic-Vibration Shoe Centerless Grinding

This paper clarifies the influence of the geometrical arrangement of the workpiece on workpiece roundness in the ultrasonic elliptic-vibration shoe centerless grinding, and determines an optimum geometrical arrangement for minimizing the roundness error of the workpiece. The influence of the geometrical arrangements ( , , ) of the workpiece on workpiece roundness were investigated by computer simulation involving a cylindrical workpiece of 5 mm in diameter with an initial roundness error of 25 μm. The results indicated that the final roundness error of the workpiece after grinding reaches a minimum at + =7° for various values of . It was found that the smaller the blade angle , the more precise the workpiece in terms of final roundness. Practical grinding operations involving pin shaped workpieces, such as SKH51, 5 mm in diameter and 15 mm in length, were carried out on the experimental apparatus previously developed. The experimental results agreed closely with those obtained by the simulation, showing that the optimum geometrical arrangement of the workpiece can be determined at + =7° and =60°, in which the workpiece roundness was improved from an initial roundness error of 25 μm to the final one of approximately 0.6 μm.

Laser Truing and Dressing of Small Vitrified CBN Grinding Wheel

This paper aims at the development of an alterative technique for truing and dressing a small vitrified CBN grinding wheel used for the internal finishing of small holes measuring several millimeters in diameter. In conventional truing and dressing, a single-tip diamond dresser or a rotary GC cup wheel dresser is employed. This levels off the improvement in the wheel truing accuracy because the stiffness of the grinding wheel shaft with an open-sided structure is low, and the shaft is thus deformed easily due to the truing force. In the present work, a new truing and dressing technique is proposed in which a Nd:YAG laser beam is employed as the dresser. Experiments were carried out with respect to the effects of the laser beam conditions (amplitude, width and frequency of pulse, and focus offset) and the relative motion between the laser beam and CBN wheel. It was found that the run-out of the CBN wheel was decreased significantly, and the wheel surface condition was improved greatly after laser truing and dressing.

Effect of Ultrasonic Elliptic Vibration on Friction between Shoe and Workpiece in Ultrasonic Elliptic-Vibration Shoe Centerless Grinding

This paper describes an experimental investigation of the effect of ultrasonic elliptic vibration of the shoe on the friction between the shoe and the workpiece in ultrasonic elliptic-vibration shoe centerless grinding, a new centerless grinding technique proposed previously by the present authors. In the new technique, an ultrasonic elliptic-vibration shoe is employed to control the workpiece rotational speed as a regulating wheel does in conventional centerless grinding. The grinding accuracy is affected significantly by the workpiece rotation stability, which is dependent on the frictional force between the workpiece and the ultrasonic elliptic-vibration shoe. The issue relating to the friction between the workpiece and the shoe is therefore very important in the complete establishment of the new centerless grinding technique. In the present work, in order to clarify the effect of ultrasonic elliptic vibration of the shoe on the frictional coefficient and to determine the appropriate ultrasonic elliptic vibration conditions, a measurement apparatus was built up in-house and used to measure the frictional coefficient under the presence and absence of the ultrasonic elliptic vibration. The measurement results indicated that the frictional coefficient decreases with increase in the size of the ultrasonic elliptic motion, and a shape of the elliptic motion, in which the frictional coefficient reaches maximum, exists.

Ultrasonic assisted electrolytic grinding of titanium alloy Ti-6Al-4V

Aiming at the development of a novel grinding technology for the high efficient machining of difficult to machine materials such as titanium alloy Ti-6Al-4V, an ultrasonic assisted electrolytic grinding (UAEG) method was proposed. Firstly, an experimental apparatus was constructed by installing an electrolytic mechanism on an existing 3D CNC machine tool attached with an ultrasonic spindle. Then, after the performance test has been carried out for the constructed apparatus, UAEG experiments of Ti-6Al-4V specimen were conducted on the apparatus to investigate the effects of the ultrasonic vibration of grinding wheel and the electrolytic phenomenon on the grinding force and the work surface quality. The experimental results indicate that the ultrasonic assisted electrolytic grinding is greatly beneficial to the decrease in grinding force and the improvement in the work surface quality compared to conventional grinding.

Automatization of Changeover for Centerless Thrufeed Grinding

センタレス研削は高精度・高能率研削加工に適した加工 方法として知られており,特に円柱状および円筒状ワーク 外周面の研削加工に対しては,スルフィード研削方式が広 く用いられている. しかしながら,この研削方式における段取り作業は,経 験と熟練を要する作業が必要であり,ワークの仕上り精度 は機械の性能と同様,またはそれ以上に作業者の技能に依 存しているともいわれている.このことは,熟練作業者が 減少する生産部門において,ワークの安定した品質と生産 量を確保する上でのボトルネックとなる要素ともいえる. ワークのセンター穴で支持する円筒研削とは異なり,セ ンタレス研削においては,良好な仕上り精度を確保するた め,工具の位置,ワーク回転速度,切込速度など,最適な 研削条件を探し出すまで数回,調整作業を繰り返すことが ある.しかし,一度段取りが終了すれば,連続的にワーク を砥石間に供給するだけで高精度な研削加工を安定して行 うことができ,その加工効率はセンター支持の円筒研削を はるかにしのぐ.製品の多様化,ライフサイクルの短縮化 に伴い,多くの生産ラインが多品種少量生産方式に移行 し,さらにコスト削減の要求が高まる昨今,このセンタレ ス研削の段取り作業の効率化,さらに自動化への取り組み は,それら課題の解決に有効な手段であると考える.

Studies on Centerless Grinding. Influeuce of Grinding Wheel Irregularity on Workpiece Roundness.

The workpiece rounding mechanism in centerless grinding is very much complicated compared to that in cylindrical grinding. Even a very small disturbance such as irregularity on the grinding wheel or the regulating wheel circumference, which makes the depth of cut at grinding point to change, may causes significant workpiece roundness deterioration in a centerless grinding operation. To minimize the effect of disturbance on the roundness, this paper investigates the mechanism of roundness deteriorating action analytically and determines the roundness error caused by disturbance quantitatively. It is found that the roundness deterioration can be avoided by controlling the ratio of grinding wheel and workpiece rotational speed.