Single Crystal Diamond Tool Research Articles

Investigation of Interatomic Potential on Chip Formation Mechanism in Nanometric Cutting Using MD Simulation

Nowadays, the nano-machining process is used to produce high quality finished surfaces with precise form accuracy. To understand and analyze the chip formation mechanism of nano-machining process on an atomistic scale, since the experimentation is not an easy task, numerical simulation such as molecular dynamic (MD) simulation is a very useful method. In this paper, MD simulation of the nano-metric cutting of single-crystal copper was performed with a single crystal diamond tool. The model was solved with both pair wise Morse potential function and embedded atom method (EAM) potential to simulate the inter-atomic force between the work-piece and a rigid tool. The chip formation mechanism, dislocation generation, tool forces and generated temperature were investigated. Results show that the Morse potential cannot perform an appropriate defect formation and plastic deformation in nano-metric cutting of metals. Also, tool forces in Morse potential are more than the forces in EAM potential. Furthermore, the fluctuations of resultant forces in Morse potential are greater than that of EAM. In addition, using many-body interaction potentials like EAM can lead to substantial changes in surface energies, elastic-plastic properties and atomic displacement, compared with the pair-wise potentials like Morse. Finally, the atomic displacement investigation shows that in EAM potential study, only the atoms in a local region near the cutting process are displaced, but in Morse potential a large portion of atoms has affected during cutting process. Subsequently, the chip temperature in EAM potential is more than that of Morse potential.

초정밀 FTS 시스템을 이용한 CNC Lathe 스핀들 이송오차 보상 및 가공정밀도 향상

The ultra-precision products which recently experienced high in demands had included the large areas of most updated technologies, for example, the semiconductor, the computer, the aerospace, the media information, the precision machining. For early 21st century, it was expected that the ultra-precision technologies would be distributed more throughout the market and required securing more nation-wise advancements. Furthermore, there seemed to be increasing in demand of the single crystal diamond tool which was capable of the ultra-precision machining for parts requiring a high degree of complicated details which were more than just simple wrapping and policing. Moreover, the highest degree of precision is currently at 50 nm for some precision parts but not in all. The machining system and technology should be at very high performed level in order to accomplish this degree of the ultra-precision.

Influence of Microstructure of Steel on Diamond Tool Wear

Excessive tool wear occurs when commercial steels are single-point diamond turned. Therefore, the development of diamond turnable steel is expected in the manufacture of molds for complex and precise optical components. As an initiate approach to this subject, various kinds of quenched and tempered steels were turned using single-crystal diamond tools, and tool wear measurement was made with a scanning electron microscopy. As a result, the various amounts of coner wear was observed by the diamond tool, and the width of wear was found to be different in a kind of steels. In order to clear up this cause, constituent phase analysis of the steels used in the turning experiments was carried out by X-ray diffraction. It gave that their microstructures differed considerably from steel to steel and were classified into four group, those are α-ferrite, α-ferrite + γ-austenite, γ-austenite, and α-ferrite + such carbides as Fe3C, Cr23C6 and WC. On the basis of these results, the inductive inference methodology was applied to the tool wear measurement and phase analysis. From the results, the steel whose microstructure consists of particle carbide precipitation on α-ferrite matrix, e.g. JIS SK85, SUS420J2, SKS3 etc., suppresses diamond tool wear because the carbides prevent carbon diffusion into iron in turning of steel.

Surface Generation and Chip Formation when Ultra-Precision Turning of SiC<sub>p</sub>/Al Composites

Chip formation and surface generation were investigated when ultra-precision turning of SiCp/2009Al and SiCp/ZL101A composites using Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) tools. The results showed that the machined surfaces took on many defects of pits, voids, microcracks, grooves, protuberance, matrix tearing etc. It was noticed that most of these defects had an intimate relationship with the removal process of SiC particle. The surface finish was much better when the SiC particles were removed by cut through or in-situ pressed into mechanisms. Material swelling and side flow, tool-workpiece relative vibration, feed rate and tool nose radius, removal mode of SiC particles were these main mechanisms of surface generation. Generally, a saw-toothed chip was formed when ultra-precision turning this kind of material and the mechanisms of this type of chip were dynamic microcrack behavior and strain concentration, which induced by the non-uniform deformation of the workpiece material.

Micro/nano sculpturing of hardened steel by controlling vibration amplitude in elliptical vibration cutting

A new ultra-precision sculpturing method in micro/nano scale for difficult-to-cut materials is proposed in the present research. Elliptical vibration cutting technology is well-known for its excellent performance in achieving ultra-precision machining of steel materials with single crystal diamond tools. Elliptical vibration locus is generally controlled and held to a constant in practice. On the contrary, the proposed method utilizes the variations of the elliptical vibration locus in a positive manner. Depth of cut can be actively controlled in elliptical vibration cutting by controlling vibration amplitude in the thrust direction. By utilizing this as a fast tool servo function in elliptical vibration cutting, high performance micro/nano sculpturing can be attained without using conventional fast tool servo technology. A high-speed amplitude control system is developed for elliptical vibration, with a bandwidth of more than 300 Hz, where the vibration amplitude can be controlled within 4 μmp–p. The developed control system is applied to sculpturing ultra-precision nano textured grooves on hardened steel with single crystal diamond tools. It is confirmed that the textured grooves have the desired shapes, and their profiles agree well with the vibration amplitude commands input to the control system. Further, a high performance micro/nano sculpturing system for plane surfaces is developed, where the vibration amplitude is controlled in synchronization with the planing motion of an ultra-precision machine tool. Nano sculpturing experiments on hardened steel, carried out by the developed system, are reported, as well as consequent picture images and a variety of dimple patterns that were formed successfully on the hardened steel as nano-scale sculptures.

Diamond Tool Wear Mechanism in Ultra-Precision Turning of SiC<sub>p</sub>/Al Composites

The wear pattern and its mechanisms of Single Crystal Diamond (SCD) tool has been investigated experimentally and theoretically during ultra-precision turning of SiC particle-reinforced aluminum matrix composite. The results showed that micro wear, chipping, peeling, abrasive wear and chemical wear were the dominating wear patterns of SCD tools. Coupled with XRD analysis on the machined surface and Raman studies on the flank wear land of SCD tool, it was pointed that the combined effects of abrasive wear of SiC particles and catalysis of copper in the aluminum matrix have caused the severe graphitization.

E01 単結晶ダイヤモンド工具を用いた高速シェーパ加工における加工誤差の解析(OS1 最新工作機械(1))

In these days, there are increasing demands for high precision and high efficiency machining in the industry of optical parts. The purpose of this research is the speed-up of shaping with a single crystal diamond tool. In order to investigate the effect of cutting speed on cutting errors, a cutting experiment is conducted under several cutting speeds. As a result, periodic cutting errors appear on workpiece surface in cutting speeds above 10m/min. The pitch of the error does not depend on the cutting speed. In order to investigate the cause of cutting errors, the tool motion is compared with the workpiece profile. The pitch of the cutting error corresponds to that of a periodic component in the tool motion. The pitch of the cutting error increases when a lubricant is used.

Machining of micro-channels and pyramid patterns using elliptical vibration cutting

Precision machining of micro-channels and quadrangular pyramids was studied using elliptical vibration cutting (EVC). A single crystal diamond tool with the trapezoidal shape was specially developed, and the tool was attached to the orthogonally arranged dual piezoelectric actuators to make the tool traverse an elliptical path at a frequency of 18 kHz for EVC. When the conventional micro-shaping method was applied to create microgrooves and patterns on workpieces of different materials, it was observed that (1) relatively large shear deformation induced periodic waves and partial tearing on the surface of brass which has relatively small brittleness, (2) a significant amount of burrs were formed on ductile copper, and (3) fractures of microstructures were observed on brittle nickel. In contrast, the application of EVC greatly reduced cutting resistance which, in turn, inhibited formation of burr and fracture of the microstructure and prevented degradation of surface quality from shear deformation, collectively contributing to significantly improving form accuracy of micro-channels and pyramid patterns.

Diamond tools wear and their applicability when ultra-precision turning of SiCp/2009Al matrix composite

Abstract The wear pattern and its mechanisms of single crystal diamond (SCD) and polycrystalline diamond (PCD) tools have been investigated experimentally and theoretically during ultra-precision turning of SiC particle-reinforced 2009 aluminum matrix composite under wet machining conditions. The results showed that microwear, chipping, cleavage, abrasive wear and chemical wear were the dominating wear patterns of SCD tools, and PCD tools mainly suffered from abrasive wear on the rake face and adhesive wear on the flank face. The local temperature increase in the workpiece material adjacent to the contact surface of SCD tool was approximately as high as 505 °C. The combined effects of abrasive wear of SiC particles and catalysis of copper in the aluminum matrix caused the severe graphitization of SCD tool with (rake face 1 1 0-flank 1 1 0) crystal orientation. The adhesive wear on PCD tool was induced by the intermittent growth and breaking off behavior of build-up-edge. SCD tool with the crystal orientation of (rake face 1 1 0-flank 1 0 0) had the best cutting performance among the three types of tools, by which the machined surface roughness Ra was less than 49 nm after cutting for over 9 km. PCD tool had a steady and favorable cutting performance and could produce acceptable surface quality when the cutting distance was less than 6 km, during which the value of Ra was less than 46 nm and varied in the range of 12–15 nm. For this tool, adhesive wear on the rake face and abrasive wear on the flank increased gradually with the increase of cutting distance. The flank wear value of PCD was only 50 μm which was slightly higher than that of straight-nose SCD (40 μm) when cutting for 6.22 km. For all the three types of tools, with the increase of cutting distance, the machining induced defects such as craters and scratches increased too. Especially, when cutting distance was long enough to cause severe tool wear, material swelling on the machined surface was severe due to the plastic side flow. The chips formed by PCD tool were more discontinuous and fragmentary than that for straight-nose SCD tool.

Influence of tool deflection on micro channel pattern of 6:4 brass with rectangular tool

Machining experiment of micro channel structure with 6:4 brass was carried out by shaping process using a single crystal diamond tool. FEM simulation using solid cantilever beam model was analyzed. In result of experiment, tool deflection is observed as machining characteristics through result of experiments such as surface roughness, cutting force and burr formations. And the influence of tool deflection is experimentally proved.

Machining characteristics of complex prism pattern on electroplated roll by copper

The BLU (back light unit) is the core component of the LCD for notebook, mobile-phone, navigation, as well as large sized TV, PID (public information display), etc. In order to enhance optical efficiency of LCD, optical films with the uniform prism patterns have been used for BLU by stacking two films up orthogonally. In this case, light interference-phenomenon occurred such as Morie, wet-out, u-turning, etc. It caused several problems such as low brightness, spots and stripes in LCD. Recently, the high-luminance micro complex prism patterns are actively studied to avoid the light interference-phenomenon and enhance the optical efficiency. In this study, the roll master to manufacture complex micro prism pattern film was machined by using the high precision lathe. The machined patterns on the roll master were 50, 45, 40, 35, 30, 25, 20, 15, 10 and 5 μm in the pitch with 25.0, 22.5, 20.0, 17.5, 15.0, 12.5, 10.0, 7.5, 5.0 and 2.5 μm in the peak height, respectively. The roll was 2 000 mm in length and 320 mm in diameter. The electroplated roll by copper and the natural single crystal diamond tool was used for machining the patterns. The cutting force was measured and analyzed for each cutting condition by using the dynamometer. The chips and the surfaces after being machined were analyzed by SEM and microscope.

전해니켈도금된 대면적 롤금형 가공시 단결정 다이아몬드공구의 마모에 관한 연구

Nickel-phosphorus alloys are attractive materials for diamond turning applications such as fabrication of large optics and other high precision parts. It is also well-known that the higher phosphorus content of the alloys minimizes the diamond tool wear. Due to the weakness of electoless nickel plating that the phosphorus contents is limited to 13-14% (wgt), increased attention has been paid at electro-nickel plating which enables the alloys with 15-16% phosphorus. In this study, experiments were carried out to observe the wear characteristic of single crystal diamond tools in micro-grooving of electro-nickel plated drums. The experiments shows that long distance (50km) machining of micro-grooving on electro-nickel plated drum is possible with a single crystal diamond tool without any significant tool wear and defective machined surface.

Development of ultra-fine-grain binderless cBN tool for precision cutting of ferrous materials

A new cutting tool was developed from ultra-fine-grain (<100 nm), binderless cubic boron nitride (cBN) material fabricated by transforming hexagonal boron nitride to cBN by means of sintering under an ultra-high pressure of 10 GPa at 1800 °C. The cutting edges of the newly developed cBN tool can be made as sharp as those of single-crystal diamond tools. In this experiment, cBN and single-crystal diamond tools of the same shape were compared by precision cutting tests using stainless steel specimens and steel specimens coated with an electroless Ni-P layer. The surface roughness ( R z ) of specimen surfaces cut with the cBN tool by means of planing was approximately 100 nm for both the Ni-P-coated steel and stainless steel specimens. Though similar R z values were obtained for Ni-P layers cut by the cBN and diamond tools, an R z value exceeding 2000 nm was obtained for stainless steel cut by the diamond tool. High-precision surfaces with R z values of 50–100 nm were obtained for stainless steel specimens cut with the cBN tool under high-speed milling (942 m/min) conditions. These results indicate that the newly developed cBN tool is useful for the ultra-precision or precision cutting of ferrous materials.

Nanometric ductile cutting characteristics of silicon wafer using single crystal diamond tools

In current wafer fabrication, most machining processes, such as slicing, edge grinding, finishing, lapping, polishing, back thinning, and dicing, are based on grinding or abrasive process, which always generated microcracks and subsurface damage. In this article, theoretical analysis on ductile mode cutting of silicon wafer showed that the machined silicon surface with free of fracture and nanometer scale surface roughness can be achieved when dislocation dominated the chip formation rather than crack propagation. Nanometric cutting on silicon wafers using an ultraprecision lathe with a single crystal diamond tool has been carried out to verify ductile cutting performance of silicon wafer. The machined workpiece surfaces and diamond tools used were examined using scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The experimental results are found to well substantiate the analytical findings, and nanometric ductile mode cutting of silicon wafer has been successfully achieved under the critical cutting conditions.

Diamond milling of nitrided steels for optical mold making

So far ultraprecision diamond machining of steel molds for optical applications is not possible because of excessive wear of the applied diamond tools. This article discusses a thermochemical approach for steel machining with single crystal diamond tools as well as the process of material modification. Ultraprecision raster milling experiments for the nitrided carbon steel C45 (AISI 1045) and the tempering steel 42CrMo4 (AISI 4140) are presented. In both materials a surface roughness of Ra&amp;lt;10nm could be achieved. The observed flank wear of the cutting tools was VB&amp;lt;2μm for all experiments after cutting work pieces with a diameter of 30mm.

Characterization of the Pt-Hf-Zr-Ni Thin Film Amorphous Alloys for Precise Optical Glass Lens Mold

We researched the characteristics of the Pt-Hf-Zr-Ni thin film amorphous alloys for precise optical glass lens mold. The five Pt-Hf-Zr-Ni thin film amorphous alloys having various alloy composition were prepared. Desired characteristics for the glass lens mold were researched. Thus, the Pt51Hf20Zr17Ni12 sample was found as the candidate material for the glass lens mold. This sample showed the crystallization temperature of 994 K, the fractured stress of 1.01 GPa and anti-sticking properties to molten glass. However, since the Pt51Hf20Zr17Ni12 sample exhibited insufficient oxidation resistance, it is necessary to inhibit oxidation with protective coating in order to apply this sample to glass lens mold. Moreover, the Pt51Hf20Zr17Ni12 sample fabricated using alloy target could be cut to taperd shape by the single crystal diamond tools without tool wear.

S1302-1-1 高Siアルミニウム合金の超精密切削に関する研究(超精密加工(1))

The objective of this study is to clarify a mechanism of the surface formation in ultraprecision cutting of high Si aluminum alloys using a single point diamond tool. For this purpose, ultraprecision cutting experiments of AC9A aluminum alloy have been conducted by means of the fly-cutting method using a single crystal diamond tool with a round nose. When the feed rate is smaller than a critical feed rate under a constant cutting speed and a constant depth of cut, the ductile mode cutting can be performed on Si particles.

単結晶ダイヤモンド工具によるAl合金の超精密切削加工における工具摩耗の監視（第１報）

Geometrical quality like surface roughness and accuracy of form has been very important in ultra-precision machining. However, because of improvement of quality of finished surface with progress of ultra-precision machining technology, quality of subsurface material like affected layer also becomes important lately. In ultra-precision cutting tool wear is serious problem since tool wear fairly affects surface integrity of machined part. However it is difficult to directly detect tool wear on machine since the tool wear affecting surface integrity is extremely small. Therefore the purpose of this study is to find out effective parameters obtained during cutting to detect single crystal diamond tool wear in ultra-precision cutting of aluminum alloy. Wear of cutting edge with large nose radius was observed by a scanning electromicroscope. Cutting forces and AE signals during cutting were also measured to calculate values of the parameters from them. As a result of cutting tests and considerations, it was concluded that area of flank wear land can be related with static and dynamic components of cutting forces and area of rake wear land can be related with RMS values of AE signals.

T1501-2-1 鉄系金属/ダイヤモンドの熱化学反応を利用した単結晶ダイヤモンドの加工(マイクロ・ナノ技術のロボティクス応用(2))

Demands for sub-meso scale devices from millimeters to sub-millimeter in size are rapidly growing. However, currently we have no effective methods of manufacturing these devices. We aim at development of ultra fine single-crystal diamond tools that are high precision, mass producible and low costs. In this paper, we propose the processing principle of a single-crystal diamond using photolithography process and thermochemical reaction with sidero-metal based on the processing experiments with various conditions and surface element analysis. We have elucidated that our processing is initiated by the diffusion of carbon into the metal and then promoted by the owidation of diamond. The etching rate of diamond increases with the annealing temperature, and we ascertain that annealing temperature should be less than 1150K to prevent combustion of diamond. Additionally, we found that the etching rate depended on the crystal orientation.

C21 Wear Mechanism of Diamond Tools in Ductile Machining of Reaction-bonded Silicon Carbide(Ultra-precision machining)

Wear mechanisms of single-crystal diamond tools in ductile machining of reaction-bonded silicon carbide (RB-SiC) were investigated. It was found that tool wear could be generally classified into two types. One is microchippings on the cutting edge, which were induced by micro impacts between the cutting edge and SiC grains. The other is two kinds of gradual wear patterns on flank face caused by different mechanisms: non-periodical scratches caused by scratching effects of the SiC grains, and periodical grooves caused by transcribing effect of tool feed marks on the machined surface. A tool-swinging cutting method was proposed to improve the service life of diamond tools.