The fundamental characteristics of “stick-slip” motion in a machine tool slideway is ascertained experimentally, and it is clarified that the time-dependence of static friction has a great influence on the behavior of the stick-slip motion. An empirical formula is proposed to express the characteristics of static friction and the mechanism of the time-dependence of static friction is examined experimentally and theoretically. The influence of properties of lubricants and surface topography on the static friction is investigated quantitatively. Finally, a general conception to prevent stick-slip motion is offered.
The cause and the mechanism of regenerative chatter vibrations due to the deflection of workpiece occurring in machining metals are investigated experimentally. The regenerative chatter vibration is induced by the phase lag of the undulations in successive cutting. This means that small undulations initially produced on a work surface by the transient vibration of the workpiece become larger and the undulations extend over the whole work surface because a given amount of energy is available for exciting or maintaining the vibration owing to the phase lag of successive undulations. Then, a differential equation of chatter vibration is introduced based on the experimental results, and some remarks on the properties of chatter vibration are given.
A method was developed to measure tool temperature distribution within the tool by means of fine powders that have a constant melting point. The method involves observation of the boundary line formed by melted and unmelted powder scattered on the tool surface. It is clarified that temperature distribution within the tool is easily and accurately measured in this manner. Temperature distributions were compared with results obtained from analyses based on Loewen and Shaw’s theory, modified on the assumption that heat distribution due to friction along the rake face is not uniform but, rather, like real frictional distribution in cutting, and the fraction of heat flowing into the tool varies along the rake face.
A new boring process is introduced and machining properties are examined. In this process, a drilled hole is finished with a plug-type rotary cutting tool which has a ring-like cutting edge. The plug-type rotary cutting tool is forced into the hole while rotating about the central axis. The effects of the tool rotation on cutting forces and surface finish are experimentally examined, and a practical tool which has a burnishing guide just behind the cutting edge is designed. The machining accuracy of this tool is compared with that of a chucking reamer. Test results show that the inside diameter of the hole finished by the plug-type tool is accurate and stable, even if the tool has an eccentricity.
Based on a new boundary lubrication model, the characteristics of lubricants under boundary lubrication at low sliding speed and low contact pressure such as in machine tool slideways are investigated in relation to surface topography. It is clarified theoretically and ascertained experimentally that the property of lubricants under boundary lubrication can be estimated by the newly defined appraisal coefficient of boundary lubrication property determined by the thickness and load carrying capacity of adsorbed lubricant film and the surface topography.
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