Slide Way Research Articles

荷重によらず摩擦力一定な空気半浮上すべり面の設計法

The hydrodynamic slideway, which is often adopted for machine tools, usually possesses a large friction and induces a lost motion (backlash), hence the positioning and contouring accuracies are decreased. These defects can be overcome if the hydrostatic slide way is adopted, but it is inevitable that the stiffness along the feed direction will become low and the manufacturing cost will increase. The authors have revealed that a proper amount of solid friction should work between the sliding faces in order to satisfy both the accuracy and the stiffness, and it is very important from the point of consistency of performance that the amount of the above frictional force does not vary with an applied vertical load and a given feed rate. The present paper uses the Half-floating Slideway which has a composite property between the hydrodynamic and the hydrostatic slideways. Air is supplied as a lubricant, hence a variation of hydrodynamic effect with the feed can be avoided. Furthermore, a load compensation mechanism which changes supply pressure automatically corresponding to the variation of the vertical load is provided. The principle and the design procedure of these slideways are reported.

Design Procedure of Pneumatic Half-Floating Slideway with Load Compensation and its Application to Machining Center

It is known that slideway friction plays an important role for machine tool performance, and therefore a proper amount of solid frictional force is preferable to satisfy various requirements of static and dynamic properties, accuracy and stiffness etc. This frictional force, however, changes in accordance with the feeding conditions of slider, in particular, that of the load and speed. The present paper shows the design procedure of a new type of slideway which can keep the frictional force being almost constant independent of the feeding conditions. The principle uses Pneumatic Half-Floating Slide way, in which the slider is supported by either an externally pressurized aerostatic force and a metal to metal contact force. If the load, mostly the workpiece weight and the static cutting force, applied on the slider increases, the increment can be compensated by a special device which is composed of a load detector (a type of air micrometer) and a pressure amplifying valve. By the application of this new slideway design to an existing machining center, it was revealed that the frictional force could be kept at almost constant independent of the applied load and the feed speed. Consequently, the amount of backlash and lost motion could also remain the same under different working conditions, which could improve, under the load of 500 kgf, both the positioning and the contour accuracies up to several micron meter better than those obtained by the conventional machine.

すべり案内面の動摩擦力変動と位置決め精度

In the 1st report, it was shown that the positioning accuracy of machine tool table can be described with the over travel length XOR of the table after the moment of the positioning signal input, and the limitation of the positioning accuracy may be given with the dispersion of XOR caused by the fluctuation of frictional force in slide way. In the present paper, the correlation between the repeatability of positioning of the table and the fluctuation of frictional force in slide way is investigated under various conditions, and the following conclusions are obtained: (1) By decreasing the surface roughness of slide way, the fluctuation of frictional force in slide way may decrease and high repeatability can be achieved. (2) The periodicity of low frequency in the surface roughness of slide way makes the positioning accuracy lower. (3) At a particular feed velocity, the fluctuation of frictional force in slide way may cause a kind of resonance in feed drive device.

しゅう動体の停止挙動

In positioning of machine tool table, the table over travels some length xOR by the inertia after the moment of positioning signal input. The xOR, called over run in this paper, is one of the most important factors determining the positioning accuracy of machine tool table. The other factor is the dispersion of xOR caused by fluctuation of frictional force in slide way. This dispersion of xOR may give the limitation of positioning accuracy. Representing the feed drives of machine tool by the spring mass system with one degree of freedom, the over run length xOR and its dispersion are analysed by digital simulation. The analysis shows that the over run length xOR in conventional machine tools may be about 5-50 μm. It can be minimized by increasing the natural frequency of feed drives or decreasing the feed velocity. The dispersion of xOR is about 0.5-5 μm, and it can be reduced by decreasing the fluctuation of frictional force in slide way.

工作機械すべり案内面の摩擦振動発生限界

In this paper the analysis of friction vibration in the slide way which has been developed by the authors is applied to the practical slide way of machine tool and the discussion about the availability of the theory, the fundamental policy for the design of machine tool slide way from the view point for friction vibration and the method to suppress the onset of friction vibration are described. The results obtained are as follows : 1. The avilability of the basic theory for the friction vibrations is verified from the experiment with the machine tool slide way. 2. It is possible to predict the critical condition of friction vibration at the design stage of slide way. 3. It is important to make the each effect of the sliding pads on the critical condition equal and to decrease it. 4. The oil groove on the slide way plays a important role for the critical conndition of friction vibration and it is recommended to make the effective width of the sliding pad as large as possible.

工作機械油圧送り機構の過渡応答の解析

This paper dealts with a transient response analysis of a hydraulic feed system of machine-tool. For a general model of the hydraulic feed system, the basic equations of the system are introduced. The experimental analysis of the transient response good agrees with the simulation of it using a analog computer and from this result it is confirmed that the basic equations are valid for the transient response. From the discussion of the effects of the various parameters on the transient response using the analog computer, it is made clear that the hydraulic feed system includes three different maa-spring-damper vibration systems where one is constructed by the table mass, the viscous resistance of the slide way and the interference of the piston-cylinder and the spring due to the compressibility of the oil in the cylinder and other system are constructed by the masses, the viscous resistances of the oil in the inlet and outlet pipe lines and the spring due to the compressibility of the oil in the cylinder.

On the Dynamic Behaviour of Machine Tool Slide way : 1st Report Characteristics of Static Friction in Stick-Slip Motion

On the Dynamic Behaviour of Machine Tool Slide way : 1st Report Characteristics of Static Friction in Stick-Slip Motion

On the Dynamic Behaviour of Machine Tool Slide way : 2nd Report Characteristics of Kinetic Friction in "Stick-Slip" Motion

On the Dynamic Behaviour of Machine Tool Slide way : 2nd Report Characteristics of Kinetic Friction in "Stick-Slip" Motion