森田 昇

The newly developed cutting force and temperature measuring system with high response speed and fine resolution can monitor cutting process as well as tool wear during high-speed endmilling of hard materials. The system enables us to precisely determine a transient cutting force and temperature action which is generated by each cutting edge of an endmill tools with various rake angles and helix angles. It is found that the cutting force and temperature in high-speed endmilling are sensitive to the helix angle rake angle and tool wearing process. When the helix angle and rake angle are 60 degrees and -15 degrees respectively the cutting force and the flank wear of each cutting egde generated is smaller than those for other angles of helix and rake.

The micro-indentation and micro-scratch device is newly developed for trial purposes aiming to evaluate the mechanical characteristic of the material surface layer by a precision machining or a micro-processing. The device enables us to precisely measure an indentation load-depth curve, and to determine the micro-hardness, the micro-scratch hardness and friction coefficient of a subsurface damaged layer and a thin film layer of 1μm or less with the same equipment. It is found that the depth profile of the micro-hardness characterizes the thickness of a stress hardening layer of a diamond cutting surface, and that the friction coefficient of a monocrystal silicon is different from a silicon oxide thin film.

In order to clear the behavior of material deformation and fracture during machining the hard and brittle materials such as a glass, the indentation tests have been carried out in various environment. The results of the experiments showed that the crack length and velocity of crack propagation, depends on a percent relation humidity in the environment, and on the stress of the surface of glass, and increases with increasing the percent relation humidity in the environment. The experimental data also showed that the dependence of crack length and velocity of crack propagation on humidity will be stronger with increases applied load. Experimental results are discussed in this paper. ? 1998, The Japan Society of Mechanical Engineers. All rights reserved.

This paper describes the mechanism of brittle-ductile transition of monocrystal silicon at a high temperature and its feasibility for ductile mode cutting. The micro-cutting tests were carried out at various temperatures, and for various cutting speeds and depth of cut by using a newly developed cutting device. The critical depth of cut is closely related to the material temperature and cutting speed. When the material temperature is 973 K at a cutting speed of 1 mm/s, the critical depth of cut is about two times that at room temperature. The critical depth of cut decreases with increasing in cutting speed. The specific cutting force is nearly constant at various temperatures. The residual stress on the ductile-mode cutting surface is compressive about 200 MPa.

In order to control the process of the nanometer scale machining precisely, it is necessary to understand the change of mechanism in nanometer-scale removing process. In this point of view, a unique nano-machining and measurement system, which utilizes the mechanisms of FFM, has been newly developed for the purpose of observation on nano-machining in the scale from 1 to 100 nm. The system has both an original micro?cantilever for machining and an ordinary micro cantilever for AFM measurement, and it also has a device which can exchange two cantilevers alternatively. To evaluate the performance of the system, a single crystal silicon was machined and scratched by a single diamond grain which was fixed on the end of the cantilever. Then, the system could make 2 μ m x 2 μm square holes of 70 nm in maximum depth. Moreover it also could make scratches obviously and measure the lateral reaction force at a time. Those results proved the system effective in nano-machining experiments. ? 1998, The Japan Society of Mechanical Engineers. All rights reserved.

Nano-machining expeiment is necessary for factual understanding of the nano-machining process. From this point of view, a unique nano-machining FFM system, which has very stiff cantilever for machining, has been developed. In order to grasp the characteristics of the developed system, single crystal silicon was machined using the function of line-scanning and area-scanning. As a result, two essential characters of the system have been extracted. Firstly, the shape of the traces machined by different cantilevers vary obviously because of the geometrical irregularity of the tip. And, even in case of using the same cantilever, the traces also vary little by little as repeat machining because of the wear of the cutting edge. Secondly, the depth of the trace machined by the area-scanning is about 10 times as large as the line-scanning. To explain the reason, a machining model was proposed, in which machining and removing efficiency is raised up by the feed of the scanning line. The lateral machining force changed by the type of scanning, and the shape of the cutting chips, which were observed by SEM, also vary by the feed condition. These results could prove the proposed model. ? 1998, The Japan Society of Mechanical Engineers. All rights reserved.

The results of basic experimental study on cryogenic machining of hard and brittle materials are presented in this paper. In order to understand the basic phenomenon of material deformation and fractue during machining the hard and brittle materials such as a glass and a semiconductor at low temperature, the indentation tests and single point diamond scratching tests have been carried out. The results of tests showed that the crack length and the indentation depth decreases, the hardness and the critical depth of brittle-ductile transition increases with the decrease of material temperature for both soda-lime glass and single crystal silicon. The optical microscope observations showed that the deformation behavior and cracking patterns at low temperature are different from those at room temperature. From our experiments, we can conclude that the cryogenic machining is advantageous to restrain generation and propagation of cracks during machining the hard and brittle materials. ? 1998, The Japan Society of Mechanical Engineers. All rights reserved.

In this paper we describe the mechanism of brittle ductile transition of monocrystal silicon at a high temperature and its feasibility for ductile mode cutting. Micro Vickers indentation tests were carried out at various temperatures, and for various indenting loads and speeds. The critical indenting speed at a fixed load, which causes cracks to form in the material surface layer, directly depends on the material temperature and load rates. The micro cutting test were carried out at high temperatures by applying the temperature dependence of the critical indenting speed. The critical depth of cut is closely related to the material temperature and cutting speed. When the material temperature surpassed 883 K at a cutting speed of 1 mm/s, the critical depth of cut quickly increased by about six times that at room temperature. ? 1998, The Japan Society of Mechanical Engineers. All rights reserved.

The effects of temperatures on the stress evaluation of boron doped silicon in solid and film forms are investigated. Several techniques, such as fluid cooling to eliminate the temperature raise and/or simultaneous observation of Stokes and anti Stokes peaks to compensate the temperature effects, are applied. The advantages and disadvantages of each method and the abilities and limits of these techniques are discussed.

In this study, which is aimed at understanding the machining characteristics in vacuum for a super-clean room and outer space, a high-speed machining system in a vacuum chamber whose pressure can be reduced to 6×10-6Pa, is newly developed and diamond cutting experiments using aluminum and copper workpieces are carried out. Some unique phenomena are observed, which are (a) a strong dependence of the cutting force on oxygen pressure, (b) a deposited product like a build-up edge on the rake face at pressure above 102Pa, (c) an adhering and sticking of chips on the workpiece surface at pressure under 102Pa . These phenomena can be well explained by an oxygen adsorbing model for the newly generated workpiece surface and chip surface. The cutting force increase in high vacuum is closely related to a chemical interaction between a chip and a tool surface.