Naoya Ikawa

Ultraprecision metal cutting : the past, the present and the future

Summary A review is made of Ultraprecision metal cutting techniques which aim at micrometer or sub-micrometer form accuracy and nanometric surface roughness in optical, electronic and mechanical components. Following an overview of the fields of application of the technique in advanced science and technology, a brief look is taken at the technical bases of machine tools, metrology and control, cutting tools and relevant technologies. Some Physical aspects of the chip removal Process and related phenomena involved in micro cutting are also discussed for better understanding, controlling and improving the technique.

Diamond turning of Brittle materials for optical components

Abstract The paper deals with the diamond turning technique to obtain mirror finish of brittle materials for optical components. Taking account of material properties and cutting parameters, a model is proposed for the brittle-ductile transition in chip formation, and the requirements for ductile mode cutting are presented. As an application, Ge, Si and LiNbO3 as brittle optical materials are turned to fine finish of less than 0.02 um P-V surface roughness in some cases.

Feasibility Study on Ultimate Accuracy in Microcutting Using Molecular Dynamics Simulation

Using molecular dynamics computer simulation, the feasibility is analyzed or, nanometric or an ultimate machining accuracy attainable in microcutting of free machining work materials under perfect motion of a machine tool. Based on the analysis, the micro process of chip and surface generation can be well understood from the atomistic point of view. The minimum thickness of cut, that is a measure of the accuracy attainable, can be expected to be about 1 nm or less, that is, 1/20 to 1/10 of the edge radius of a realistic fine cutting edge available. Tile ultimate roughness and depth of deformed layer of work surface is estimated to be about 0.5 and 5.0 nm, respectively. The quality of work-surface of aluminum is worse than that Of Copper. These results suggest that the ultraprecision metal cutting the machining accuracy of which is at least 1 nm is feasible.

Minimum thickness of cut in micromachining

The authors discuss the significance of the minimum thickness of cut (MTC) which is defined as the minimum undeformed thickness of chip removed from a work surface at a cutting edge under perfect performance of a metal cutting system. Following a brief look at the relation between MTC and the extreme machining accuracy attainable for a specific cutting condition, it is shown that a very fine chip with an undeformed thickness of the order of a nanometer can be obtained from experimental face turning of electroplated copper by a well-defined diamond tool. To understand the nanometric metal cutting process, a computer simulation using an atomistic model is proposed.

An atomistic analysis of nanometric chip removal as affected by tool-work interaction in diamond turning

This paper discusses the significance of the minimum thickness of cut which is defined as the minimum uncut thickness of chip removed from worksurface at a cutting edge under perfect performance of a metal cutting system. Following a brief lock at the relation between the minimum thickness of cut and extreme machining accuracy attainable for a specific cutting condition, it is shown that a very fine chip the uncut chip thickness of which is at the order of 1 nm is obtained in a experimental face turning by a well-defined diamond tool. To understand nanometric chip removal process, a computer simulation using an atomistic model is made. The analysis of the experimental results aided by the computer simulation shows that, while the minimum thickness of cut is affected by the tool-workmaterial interaction to a certain degree. It is more strongly affected by the sharpness of cutting edge and that the minimum thickness of cut may be at the order of 1/10 of the cutting edge radius.

Brittle-Ductile Transition Phenomena in Microindentation and Micromachining

Abstract A generalized hypothesis for the brittle to ductile transition in micromachining and microindentation of brittle materials is proposed. By the hypothesis, complicated transition phenomena observed in practical machining processes are well explained. Experimental results on microturning, ELID grinding of monocrystalline Si and LiNbO 3 support the applicability of the hypothesis. Microindentation testing is shown to evaluate the intrinsic ductility and critical scale of machining for ductile mode machining. To analyze the machining process in extremely small scale, molecular dynamics computer simulations of microindentation and cutting are made on a defect-free surface. These results suggest that any material, in spite of their ductility, can be machined in ductile mode under the sufficiently small scale of machining.

Structure of Micromachined Surface Simulated by Molecular Dynamics Analysis

Using molecular dynamics computer simulation, a feasibility study is made for the quest of ultimate quality of machined surface attainable in diamond microcutting of cooper with a fine cutting edge under hypothetically perfect machine motion. Based on the analyses, the surface generation process and microstructure of worksurface are well understood from atomistic point of view. In cutting of monocrystalline cooper, the worksurface which is free from residual distortion can be obtained and ultimate surface roughness is estimated to be less than 1 nm. In cutting of polycrystalline cooper, nanometrically distorted layer inevitably remains on worksurface. However, the ultimate surface roughness is estimated to be at the same level as that of monocrystalline copper.

Molecular Dynamics Analysis as Compared with Experimental Results of Micromachining

An attempt is presented on the molecular dynamics (MD) analysis of nanometric chip removal process in micro-cutting. Comparison shows a family good agreement between the chip morphologies, the cutting forces and the specific energy in both MD simulation and micro-cutting experiments. It is also shown that MD simulation can be applied to the analysis of thermal field in metal cutting process with the introduction of a suitable scaling on the gradient in thermal field which is affected by the thermal conductivity of the workmaterial.

A New Micro-Cutting Device with High Stiffness and Resolution

Abstract A micro cutting device consisting of a pair of parallel springs and a piezo electric actuator has been developed. With the aid of the finite element method, the device was designed to have a good dynamic response up to 2 kHz with a stiffness of 80 N/μm and an infeed resolution of 5 nm. Submicrometer diamond cutting, controlled by a personal computer, was accomplished by means of the piezo electric element capable of detecting the initial contact between the tool and the cutting surface with an accuracy of ± 0.1 μm.

Crack Initiation in Machining Monocrystalline Silicon

Abstract Based on the discussion in which the defect as a source of cracks must be created during cutting a silicon monocrystal, the renormalization group molecular dynamics has been proposed to simulate the defect initiation process. The method can be applied to a model of micrometer size, which is necessary to bring about brittle mode cutting, and yet permit the observations of the defect initiation process of an atomic size. The result of the simulation shows that a microcrack-like defect can be initialed during cutting through the interaction between a local static stress distribution and global dynamic stress associated with acoustic waves