Toshiyuki Obikawa

High Speed Machining: A Review from a Viewpoint of Chip Formation

This paper describes strong nonlinearity in log V-log L relationship, which is often found in machining of supperalloys, titanium alloys, hardened steels, cast irons, etc. The nonlinearity plays an important and favorable role in extension of life-span cutting distance at higher cutting speeds; that is, in a certain range of cutting speed, life-span cutting distance increases with cutting speed. Results of tool wear in a sliding test and cutting experiments, which showed the evidences of strong nonlinearity, were investigated and the mechanisms causing the nonlinearity were discussed.

Ultrasonic-Assisted Incremental Microforming of Thin Shell Pyramids of Metallic Foil

Single point incremental forming is used for rapid prototyping of sheet metal parts. This forming technology was applied to the fabrication of thin shell micropyramids of aluminum, stainless steel, and titanium foils. A single point tool used had a tip radius of 0.1 mm or 0.01 mm. An ultrasonic spindle with axial vibration was implemented for improving the shape accuracy of micropyramids formed on 5–12 micrometers-thick aluminum, stainless steel, and titanium foils. The formability was also investigated by comparing the forming limits of micropyramids of aluminum foil formed with and without ultrasonic vibration. The shapes of pyramids incrementally formed were truncated pyramids, twisted pyramids, stepwise pyramids, and star pyramids about 1 mm in size. A much smaller truncated pyramid was formed only for titanium foil for qualitative investigation of the size reduction on forming accuracy. It was found that the ultrasonic vibration improved the shape accuracy of the formed pyramids. In addition, laser heating increased the forming limit of aluminum foil and it is more effective when both the ultrasonic vibration and laser heating are applied.

MSEC 2009 State-Of-Art Paper: Micro/nano-Technology Applications for Manufacturing Systems and Processes

Micro/nano-technology has made tremendous impact in all science and engineering fields in last decades. While review papers on meso/micro/nano manufacturing systems and processes have been published recently, there still lacks a review on how micro/nano technology has been applied to advance fundamental understanding and to enhance practice for manufacturing systems and processes. This paper is not concerned about the advances in meso/micro/nano manufacturing processes and systems themselves, but focuses on their impact on manufacturing applications. This paper presents the state-of-art of the advances on various aspects of how micro/nano technology impacts macro manufacturing systems/processes. Due to the time and space limit, this paper particularly reviews the topics as follows, 1. Micro/nano sensor applications in manufacturing (by Toshiyuki Obikawa and Xiaochun Li), 2. Micro/nano metrology for manufacturing applications (by M.T Postek), 3. Design and manufacturing of micro patterned arrays over macro-scale areas (by David Dornfeld), 4. Functionlized nanodiamonds and applications (by Jack Zhou), 5. Computational simulations at nanoscale for machining (By Ranga Komanduri), 6. Machining surface integrity and multiscale simulation (by C. Richard Liu, Jing Shi, Yuebin Guo, and Xiaoping Yang), and 7. Simulation for forming of parts with micro features (by Jian Cao).Copyright

High Speed Machining of Difficult-to-Machine Materials under Different Lubrication Conditions

This paper describes the applicability of air jet assisted (AJA) machining to stainless steel and titanium alloy at high cutting speeds in terms of tool wear and tool life. A specially designed tool holder with an air nozzle very close to the tool tip was prepared for turning stainless steel. From the experimental results, it was found that the application of flood coolant from the side of the end flank face leads to better result in tool life in AJA machining of stainless steel than that from the side of the side flank face. The assistance of air jet can improve the tool life of the M35 CVD coated insert in machining of the stainless steel by 36 to 100% under the optimal conditions in comparison with wet machining. It was also found that the air jet assistance extended the tool life of the S10 PVD coated insert by 48% in turning titanium alloy. The tool life extension of the coated insert in AJA machining titanium alloy is much longer than that of an uncoated carbide insert.

High performance cutting using micro-textured tools and low pressure jet coolant

Tool inserts with different kinds of microtexture on the flank face were fabricated by laser irradiation for promoting the heat transfer from the tool face to the coolant. In addition to the micro-...

Machining of sintered steel under different lubrication conditions

ABSTRACT Cutting experiments of sintered steel Fe–2Cu–0.8C under different lubrication/cooling conditions and with different tool materials were performed in order to clarify the reasons for the low machinability of the sintered steel, and investigate the applicability of minimum quantity of lubricant (MQL) to the machining of sintered steel. As a theoretical approach to the short tool life in machining sintered steel, the impacts to the cutting edge caused by micro-voids were theoretically modeled, and it was revealed that the cutting edge suffered from impacts at a very short interval causing high cycle fatigue. Extremely short tool life in dry machining of sintered steel already used for wet machining proved that coolant definitely increased the stress amplitude in high cycle fatigue. Application of the air jet to a tool showed the positive effect in reducing tool wear. This indicated the possibility that micro-cracks nucleated by high cycle fatigue were healed by oxidation. MQL cutting with small amount of oil and air jet is proved to be acceptable for machining sintered steel from the results of cutting experiments using uncoated and coated carbide and cermet tools. Finally, it is confirmed that thick coating of a carbide tool is effective for dramatically improving the machinability.

Influence of Coolant Application Direction on the Cutting Performance of Ceramic Tool in High-Speed Air-Jet-Assisted Machining of Inconel 718

This paper describes the high speed air-jet-assisted machining of nickel-base superalloy with a SiC whisker reinforced alumina insert. This machining method showed already good performance in high speed machining of Inconel 718. In this paper, the influence of the application direction of coolant on the tool wear and tool life was investigated for obtaining much better cutting performance of the ceramic tool. The coolant was applied from the side of flank face with three different directions: two oblique directions from the end and side flank faces and the perpendicular direction to the cutting edges. In contrast, the application direction of the air jet was always perpendicular to the cutting edges. The experimental results showed that the best performance in the air-jet-assisted machining was obtained by applying coolant from the side of side flank at a cutting speed of 420 m/min and from the side of end flank at a cutting speed of 780 m/min. The necessary condition found for the best performance was that the size of notch wear was a little larger than that of flank wear.

Performance of a Holed-Insert in Finish-Turning of Inconel 718 under Jet Coolant

Nickel-based alloy has been widely used in the aerospace industry due to its excellent mechanical properties. As originally designed to retain mechanical strength under the high temperature environment, the tool wear problems normally represent in the severe flank/crater wear and corrosion during the machining process. In this study, two types of holed-insert (OHT and THT) were proposed to excite the coolant convection so as to increase the heat transfer from the insert to the coolant under the jet coolant (JC) method. As a result, JC method showed the ability of increasing the flank wear resistance, and the THT type of holed-insert extended the tool life by approximately 59% compared with the ordinary insert.

Air Jet Assisted Machining of Inconel 718 with Whisker Reinforced Ceramic Tool

Nickel alloy is widely applied to aero-engines, marine structures, chemical plants, etc. This alloy has superior mechanical and chemical properties, but is one of difficult-to-machine materials because of its superior properties. For this reason, various machining methods, such as cryogenic machining, hot machining, machining using high pressure coolant and rotary machining have been studied for increasing the cutting speed and cutting efficiency of this alloy. Recently, a new lubrication method called air jet assisted (AJA) machining was developed to extend tool life by 20-30% in finish-turning of Inconel 718 and Ti-6Al-4V. In this machining method air jet as well as coolant was applied to the cutting area. In this study, AJA machining was applied to high speed machining of Inconel 718 with a SiC whisker reinforced ceramic tool. The air jet was applied from an air nozzle at the tool flank face. Because the ceramic tool is likely to suffer from severe notch wear, the influence of AJA machining on flank and notch wear of the ceramic tool was investigated experimentally. As a result, it was found that as compared to conventional wet machining, AJA machining increased flank wear but reduced notch wear, which is usually critical to the tool life of the reinforced ceramic tool. The tool wear characteristics peculiar to AJA machining were effective for extending tool life in high speed machining of this alloy.

Wear Characteristics of Cutting Tools in Turning of Sintered Steel under Different Lubrication Conditions

Finish machining of sintered steel is increasingly important for near net shape technology. However, the life of a cutting tool for machining sintered steel is generally much shorter than for carbon steel and thus, finish machining increases the manufacturing cost of sintered products. For this reason, wear characteristics of several grades of cutting tools in turning sintered steel were investigated under different lubrication conditions. As a result, it is found that a P10 grade of cermet and an S01 grade of AlTiN coated carbide are recommended for dry machining. When cutting fluid is necessary for chip control and disposal, air jet assisted wet machining with a K10 uncoated cemented carbide and wet machining with a P10 cermet are recommended. It is also found that a small amount of cutting fluid remained in the workpiece during wet machining caused an intense thermal impact to a P10 uncoated cemented carbide leading to short tool life.