Jun Shinozuka

Chip breaking analysis from the viewpoint of the optimum cutting tool geometry design

Abstract The chip breaking process mechanism of the grooved rake face tools is simulated by thermo-elastic plastic finite element method. The shape, temperature and flow stress of the deformed chip in the initial model of this simulation are obtained from the finite element analysis of the steady state metal cutting mechanism. In this chip breaking simulation, a stress-dependent fracture criterion is used. The chip breakability and the force change at the chip breaker edge are obtained. The simulated results are in good agreement with experimental results for various cutting conditions and various tool geometries. It is verified that this simulation is effective as an analytical approach to the optimum metal cutting tool geometry design.

Sheet steel lamination for rapid manufacturing

Abstract A layer manufacturing method using thin sheet steel has been developed for the direct and rapid manufacturing of laminated steel products with high accuracy. The laminated steel products were manufactured by repeating two principal processes: (1) welding of thin sheet steels in a layer-by-layer fashion for heaping up a laminated workpiece; and (2) cutting of a CAD model cross section out of each welded sheet steel. The sheet steel used was 0.2 mm thick and was coated with U-alloy, a low melting point solder, 40 μm thick on the both sides of the sheet. A specially designed induction heater was used for welding the sheet steels using a hot press. For every repeat welding of a sheet of steel, the height of the workpiece was measured with a laser displacement meter. Then a personal CAM installed in a personal computer calculated a tool path at the height of the workpiece to cut the CAD model cross-section out of the top sheet steel. Finally laminated steel products were obtained by removing the unnecessary parts surrounding the products. In addition to the manufacturing of laminated steel products, the welding strength of U-alloy coated sheet steels and the strength of the laminated steel bars were evaluated by a peel test and a bending test, respectively.

Analysis of Mist Flow in MQL Cutting

It is widely required not to use cutting oils containing surface reactive chlorine compounds in metal cutting for conservation of the global environment. Therefore, the minimal quantity lubrication (MQL) attracts attentions. In MQL machining, it is necessary to optimize the supply of oil mist so that the mist will concentrate near the tool tip for a better lubrication condition. The mist flow between the tool clearance faces and finished surfaces in MQL cutting was analyzed using a general purpose FEM software ANSYS/FLOTRAN. Through the analysis, the mist flow and pressure between the tool clearance faces and finished surfaces were visualized. Influences of the velocity and direction of the mist flow, and the cutting speed, on the amount of mist supplied to the space near the cutting edge were investigated quantitatively. Finally, optimal conditions of MQL were presented for the cutting process. Introduction Cutting oils are widely used for the disposal of chip, improvement of machining accuracy and surface roughness, and prolongation of tool life. These days, it is required to use chlorine-free cutting oils in machining for the conservation of the global environment. Disposal cost of the waste cutting oils is increasing. Regulations of use of the cutting oils are enforced. Therefore, from the environmental and economical points of view, minimal quantity lubrication (MQL) attracts attentions and has been investigated vigorously [1, 2, 3]. MQL machining that a small amount of vegetable oil or biodegradable synthetic ester (about 10 ml/h) is blown to the tool tip with compressed air is nearly equal to the traditional wet machining in tool life, efficiency of lubrication and surface roughness when appropriate conditions are selected in turning [4], milling [5], drilling [6] and tapping [7]. Cutting oil turns into mist in MQL machining. Therefore, it is necessary to investigate the flow of oil mist to concentrate it near the tool tip effectively. In this study, the optimization of MQL cutting-off was examined based on the analysis of mist flow. First, the analysis visualized the mist flow and pressure between the tool clearance faces and finished surfaces, and illustrated the influences of the mist blowing velocity, mist blowing angle and cutting speed on the amount of mist supplied to near the cutting edge quantitatively. Secondly, measurement of pressure distribution on the flank face when turning air blow off, proved that the suction generated near the cutting edge caused the mist flow to near the tool edge effectively. Finally, better conditions of MQL cutting-off were discussed. Three Dimensional Analysis of Mist Flow The mist flow between the tool clearance faces and finished surfaces in MQL cutting-off was analyzed under three-dimensional conditions using a FEM code ANSYS/FLOTRAN. The region of analysis and its finite element mesh are shown in Figs. 1 and 2, respectively; the clearance angle is 5 degrees, cutting width is 5 mm, the cross section of tool holder is 4 mm×25 mm and the depth of the groove is 5 mm. It is not necessary to take the rake angle and undeformed chip thickness into consideration. Because of the symmetry of the tool, only the half of the region is modeled with Key Engineering Materials Online: 2004-02-15 ISSN: 1662-9795, Vols. 257-258, pp 339-344 doi:10.4028/www.scientific.net/KEM.257-258.339

Development of Cutting Tool With Built-In Thin Film Thermocouples for Measuring High Temperature Fields in Metal Cutting Processes

In order to measure temperature fields on tool face during cutting, a cutting tool with built-in thin film thermocouples (TFTs) has been devised. The TFTs composed of a nickel and nichrome thin films were fabricated on the rake face near the cutting edge of a sintered alumina tool insert using a physical vapor deposition and photolithography technique. An empirical formula that shows Seebeck coefficient of a TFT depends on electrical resistance of the TFT circuit was established. Three different types of tools in number and size of TFTs were developed and temperature fields on the rake face in cutting of a plain carbon steel S45C were measured. The results of the cutting thermometry experiment reveal that the devised tool with built-in three TFTs can measure temperature fields on the tool face and can sense slight change in cutting situation.

Development of Cutting Tools with Built-In Thin Film Thermocouples

Cutting temperature and cutting force are important basic physical parameters, which should be known to achieve high efficiency and high quality machining. However, it is difficult to measure the cutting temperature in machine shops. A new cutting tool with temperature sensors fabricated by photolithography was devised to measure the cutting temperature directly during machining. In this study, tools with a thin film thermocouple (TFT) fabricated on a ceramics tool insert were developed. Thermometry cutting experiments with the developed tools were carried out at different cutting speeds and feed rates. The performance and capability of the tools with a built-in TFT were discussed.

Analysis of Grinding Temperature Considering Surface Generation Mechanism

Grinding temperature was analyzed considering heat generation by cutting with each abrasive on the wheel working periphery. A geometrical analysis of interference between the abrasives and workpiece gave the instantaneous cutting cross section, and visualized the surface topography generated by the time. Using the specific grinding energy and the instantaneous cutting cross sections, the instantaneous distribution of heat generation on the wheel-workpiece contact area was obtained. Then grinding temperature was calculated for a given heat partition into the workpiece. Since a cutting with an abrasive generated an impulse of heat flux, temperature distribution calculated for grinding carbon tool steel varied drastically, and very high local temperature or temperature spikes appeared.

Effect of MnS on the cutting mechanism of powder metallurgy steel in cutting speeds ranging from 1 m/s to 150 m/s

Orthogonal cutting experiment of powder metallurgy steel was performed in cutting speeds ranging from 1 m/s to 150 m/s. High-speed cutting experiment was carried out with a high-speed impact-cutting tester. This study focuses on the change in the effects of free-cutting of manganese sulfide with cutting speed. The principal force and thrust force were measured. The cross sections of the chip and of the machined surface were observed. Color mapping analysis of the tool-chip contact region on the rake face with EPMA was done. Although the serrated type of chip formed in all experiments, the cutting mechanism was analyzed by employing a shear plane model. This paper discusses how the effect that MnS promotes the ductile fracture and the effect that MnS improves the friction property at the tool-chip interface change as the cutting speed increases.

Ultra High-Speed Cutting Experiment under the Cutting Condition that Cutting Speed Exceeds Plastic Wave Speed of Workpiece

Raising a cutting speed to above speed of a plastic wave of a workpiece material induces the high levels of the hydrostatic stresses in the shear zone, because a plastic wave traveling there becomes a shock wave. In order to ascertain the cutting phenomena occurring under the ultra high-speed cutting condition, the cutting experiments of a pure lead with cutting speeds of up to 140 m/s are performed with a high-speed impact cutting tester developed. The experimental result reveals that the cutting mechanism, especially chip formation, changes remarkably and the friction angle at the tool-chip interface rises in the ultra high-speed cutting. It can be explained that these phenomena arise from the plastic shock wave in the shear zone.

Fabrication of Multiple Micro-Grooves by Ultrasonic Machining with a Tool that Laminated Thin Hard-Material and Thin Soft-Material

A micro-grooving method by ultrasonic machining with a lamination tool has been devised. Thin walls on the tip of an ultrasonic tool can fabricate many grooves on a workpiece by one ultrasonic-machining process. Thinner wall for fabricating micro grooves, however, poses the lack of the stiffness of the tool, resulting in the difficulty of the grooving. Then the walls are enfolded with a soft material such as a polymer plastic to supplement the lack of the stiffness. Since soft material absorbs the energy of the ultrasonic vibration, the damage by the impacts of the abrasive particle on the workpiece surface under the soft material is little. Therefore multiple micro-grooves can fabricate efficiently by using of a lamination tool in which thin hard-materials and thin soft-materials are laminated alternately. In this paper, the lamination tools were developed with a thin shim-sheet as the hard material and an epoxy adhesive as the soft material. The fabrication experiments of the parallel grooves on alumina ceramics were conducted. This paper investigates the influences of the parameters of ultrasonic machining such as the grain size of the abrasive particle, the static machining load or static normal stress applied to the tool-workpiece contact region and the grooving time upon the characteristics of the micro-grooves. The results show that the grooving efficiency depends on the grooving time and the static normal stress. Finally, some applications are shown.

Development of Orthogonal Impact Cutting Testing Machine

FEM cutting simulation predicts that the plastic shock waves are generated that develop the high levels of hydrostatic stress in the shear zone when cutting speed exceeds the plastic wave speeds of the workpiece material. The orthogonal impact cutting testing machine was developed to confirm this phenomenon experimentally. In the testing machine, two guide rails are set up in parallel. The cutting tool and the workpiece are installed on the blocks that slide on the rail. Each block connected with the piston in the air tube by the pushrod is launched by the expansion of compressed air, and is accelerated rapidly. When the two blocks passes each other, cutting is done. This paper describes the details of the developed impact cutting testing machine and experimental results of cutting a pure lead at cutting speed up to 65m/s.