The authors investigate the dynamic behavior of a lathe chuck in view of suppressing the chatter vibration in the turning operation. The dynamic behavior is greatly affected by the damping and rigidity characteristics of the system. In this paper, a model chuck with an impact damper is produced through experimentation, and its behavior is investigated. This chuck is found to control the damping capacity under the condition of effective constant rigidity. The following conclusions are drawn. (1) The most appropriate damping characteristic for suppressing chatter vibration corresponds to the rate of vibration. (2) Some damping effects can also be recognized on the surface of workpiece under stable conditions.

In this paper, the chucking behaviors of power chuck were investigated experimentally. The fluctuation of chucking force during actual cutting had not yet been measured up to this time. Especially, behaviors of the chucking force under the existing of chatter vibration were ascertained in detail. The results obtained from this study are as follow : (1) Fluctuation of the chucking force is generated, similar to the scroll chuck, periodically due to the combined effects of directional orientation of the chucking stiffness and the cutting force. (2) Under the condition of high speed spindle, the decrease of the chucking force on power chuck is bigger than that on scroll chuck by decreasing of friction force. (3) In the case of power chuck, the decrease of the chucking force after cutting with the mechanism of compensation is smaller than the case of scroll chuck.

The generating mechanism and the behavior of chatter vibration have been investigated in detail for a long time. On the other hand, very few reports have been appeared about the positive detection of chatter vibration. However, establishment of an objective method which can detect the commencing of chatter vibration in a process and its practical suppression method are the most important and urgent problems for automatic manufacturing systems. In this paper, a simple and practical approach is proposed to detect the occurrence of chatter vibration in a process and its applicability is investigated. According to the approach in this study, the occurrence of chatter vibration is detected from a trend of the factor which is produced from the signal of workpiece deflection. The authors have constructed a simple and practical hardware system using an analogue circuit developed for suppressing chatter. They have been also investigated its applicability to the manufacturing field. The authors obtained satisfactory results in this study.

The chatter vibration in machining restricts the efficiency, accuracy and automation of manufacturing. Many previous attempt have been made to reduce the chatter vibration. However, satisfactory results have not yet obtained. It would be a useful step in the industrial world to be able to predict the commencing point before machining in order to prevent chatter vibration. In this paper, therefore, the prediction is investigated on turning operations. As a result, it was proven that there is a mutual relationship between compliance characteristics of a chuck-work system and the commencing point of chatter vibration.

In this paper, the chucking characteristics were investigated experimentally. The chucking force during cutting, which had not been studied, was measured with a load washer. Many advantageous characteristics were ascertained in detail with this measuring system. The results obtained from this study are as follows: (1) Fluctuation obtained force is generated periodically with the rotation of main spindle due to the combined effects of directional orientation of the chucking stiffness and the cutting force. (2) This chucking force of a three-jaw scroll chuck decreases with an increase in the fluctuation of chucking force. Especially, the fluctuation appears remarkably in the presence of chatter vibration.

There have been many studies on chatter vibration in machining, but there seems to be no regulations to decide the commencing point of chatter objectively. The development of an objective method which can estimate chatter commencement is very much in need for automatic manufacturing systems dynamic performance tests for machine tools, and so on. In this study, therefore, the estimation of chatter has been experimentally investigated for the chuck work turning process. Consequently, the commencing point of chatter can be decided from the behavior of the mean square value of the work piece deflection, where the mean square value is suddenly increasing with the chatter commencement. Then the commencing point of chatter can be estimated practically by this method before the occurrence of excessive vibration.

本論文はチャック加工時に発生する係数励振動についてその理論的解析と実験による確認を行った結果について報告したものである.解析の結果,振動の安定判別線図を求めることができ,切削試験の結果とよく一致することがわかった.この振動は工作物支持剛性の方向依存性の大きい場合に顕著に発生する.また,再生びびり振動と混在すると不安定領域は広がる.このときの安定判別を解析的に行うことは困難である.

In this paper, the parametric instability in chuck work process is investigated. And an analytical criterion of stability is given, and experimental confirmation is carried out. The vibration of this type is considered to have a significant influence on machinability. However, the applicable isolation of this vibration has not been done. The results obtained are as follows: (1) The parametric vibration is generated by the directional orientation in the stiffness of chucked workpiece. (2) The theoretical analysis for predicting the conditions of parametric instability could be verified by good agreement with the result of cutting test. (3) In the chuck work process, the parametric vibration is amplified with mingling regenerative chatter by the condition of low and fluctuating stiffness.

切削加工における工作物支持特性の向上を意図して、チャック-工作物系の減衰特性が切削面品位、特にびびり振動発生時の切削面あらさに及ぼす影響について実験的検討を行った。種々の減衰能増加対策を系に応用し、減衰能を変化させて切削試験を行った結果、いずれの場合にも減衰能が増大すると切削面あらさは減少する。また、その効果は減衰の発生機構によって異なることがわかった。

本論文はチャックにより把握された工作物の剛性の方向依存性について実際の加工状態で実験的に検討したものである. その結果従来静的なモデル実験で報告されているものと同様の特性をもつ方向依存性が確認できた. そして, 特に三つつめチャックにおいてこの現象は顕著であり, しかも, びびり振動の発生に伴いその強さが増強される. また方向依存性による切削抵抗変動成分の振幅の増大や特異なびびりマークが観察された.

Deformation properties of the jointed surfaces are important in designing the machine tool structures, so in this paper considering the bolted joint as an example of jointed surfaces, the behaviour of the tangential displacement which are in close relation with the damping capacity of jointed surfaces, have been experimentally studied by applying the repeated cyclic tangential load to the jointed surface, also changing the joint materials and surface roughness. Even before the tangential displacement on a bolted joint shows a macroscopic sliding, a microslip can be found, and thereby the tangential load-displacement curve demonstrates a hysteresis loop under the repeated loading cycles, because the tangential displacement is a direct sum of the micro-slip and the tangential elastic displacement. The results obtained from this study are as follows. (1) The tangential displacement decreases with the repeated number of loading cycles, and the decreasing rate of the displacement depends on the joint materials and also on the joint surface roughness. (2) Both of the amount of the micro-slip and the tangen-tial elastic displacement increase with the increase of surface roughness. (3) The tangential elastic displacement on the jointed surfaces is, in general, in linear relation with the p=P/Q, which is the ratio of the tangential load P to the normal load Q. In addition, the tangential elastic displacement changes by the materials, surface roughness and the diameter of the jointed surface.

The heavy machine tools are often made of welded steel and at the same time jointed beam or a damping joint is often used. However the behaviour of the damping capacity of higher mode of vibration of the jointed beam has not been yet fully clarified. In this paper the relationships between the frequency and the damping capacity or the slip ratio and between the damping capacity and the mode of vibration have been experimentally studied by the use of an improved band-width method with two kinds of jointed cantilever beams which are connected with a single bolt and several bolts respectively.

Damping capacity is one of the most important parameters in considering the structural design in machine tools. It is not a usual means to use solvant for wiping out oil or grease from bolted joints. So, this paper describes an experimental investigation on dynamic characteristics of bolted joins having a thin layer of lubricant. It is found that the variation rate of bolt's axial force which is in propotion to a relative amplitude of two surfaces shows a smaller value as compared with dry joints. The damping effect of oiled joints dependents on fastening force of bolts and static bending force, however in the case of high contact pressure it is not dependent on them. The effect of lubricant and some other results are described.

As a serial study on the damping capacity of a bolted joint, in here effects of the machining method and roughness of joint surfaces, joint materials and also interfacial layers, on the damping have been investigated. By measuring the logarithmic damping decrement and the natural frequency of bolted cantibeams, how the damping and its amplitude dependence, and also the optimum preload, change themselves with different conditions of joint surfaces, has been also discussed. From the results it is known that the contact condition of joint surfaces has large effects on the damping capacity, but a little effect on the natural frequency. In the metal contact condition, the micro-slip on joint surface caused by the plastic deformation or the tearing of seizured points, is of importance to know the behaviour of damping. In the oiled joint, the increase of damping can not be always expected even if high viscosity oil is applied to joint surfaces.

In the Computer Aided Design for a machine tool structure being developed, there are two important problems to be solved to compute the overall stiffness of a machine tool. One is the limitation of the core size of computer, which affects largely the computing accuracy. Another is how a machine tool structure is replaced by a suitable model available to the computation with good propriety. To make some countermeasures for these problems, one trial of CAD was carried out here with the cylindrical column having collared ribs and core-holes. From the results, it can be concluded that the cylindrical column in closed cross-section is well replaced by an one-dimensional beam-like element notwithstanding the existence of collared ribs and core-holes. This means that there may be some possibility of a new CAD technique to solve the present problems. In addition to this investigation, the effects of collared ribs and the influences of core-holes on the static stiffness of cylindrical column have been also described here.

The loss energy of a jointed cantibeam may be derived from a microscopic slip and a normal pressure on the interfaces. It is however very difficult to calculate theoretically the energy dissipation between the joint surfaces, because a characteristic of the micro-slip on the interfaces has not been fully clarified yet.In this study the mechanism of the energy dissipation and also the ways of theoretically calculating the damping ratio of the jointed cantibeam have been investigated by considering experimental results of the characteristic of static micro-slip between the jointed surfaces.From the results it is clarified that the damping ratio of the jointed cantibeam can be well calculated by using the equations proposed in this paper, and how the characteristic of micro-slip influences the behaviours of the damping ratio.