This paper presents a new method of optimal selection of cutting tools in a geometric cutting simulation. Firstly an area to be cut by an end-milling tool is calculated according to each different tool. The shape of the workpiece is represented in a hierarchical lattice space model, Enhanced Z-map model. Secondly a tool set prepared is coded as a binary bit string, i. e. gene. Each bit corresponds with a certain tool and 1 indicates its use and 0 is not. Thirdly a fundamental Genetic Algorithm consisting of selection, crossover and mutation is applied based on the index which takes account of total cutting time, uncut area, the number of tools used etc. Here it is assumed that the selected tools would be used in descent order of diameter and it would cut its corresponding area as entirely as possible. Some simulations are illustrated and the conclusions are briefly mentioned too.
This paper describes the finishing performance of lapping films based on deformation analysis of their constituents by using the Finite Element Method (FEM). The models applied to the FEM were varied by changing polyester film backing thickness, bond thickness, shape of abrasive grain and size of grain of lapping film, supposing that different types of lapping films are used in the actual finishing processes. And, the effects of them and the elastic characteristics of bond on the deformation characteristics were also estimated. As a result, the behavior of abrasive grains in the contact area between the lapping film and workpiece became clear. Furthermore, experiments on the cylindrical ceramic workpiece surface finishing, utilizing lapping films coated diamond abrasive grains, were carried out and the effects of finishing conditions on stock removal and finished surface roughness were examined. From the experimental results, it was confirmed that the experimental characteristics could be explained clearly by the obtained results of FEM analysis.
The purpose of this study is to enhance the practicability of the self-propelled rotary tools for high-performance machining of new industrial materials. Based on investigation of the rotary cutting mechanics, a new concept of rotary tool design featuring compact and simple structure has been developed and evaluated experimentally. Exhibiting superior cutting performance in machining new industrial materials equivalent to the previous design, the new cutting tools show higher rotating accuracy and stiffness resulting in better machined surface roughness. It enables the rotary cutting technology to be practicable in a number of machining operations where its predecessors have met difficulties because of their structural constraints.
This paper describes a feature of developed high-strength Si3N4 ceramics and its application for automotive engine parts. By the high speed shock compression test, Hugoniot elastic limit of various Si3N4 ceramics were evaluated. The microstructure of developed Si3N4 is controlled with the linear density of Si3N4 crystalline grains shows the superior mechanical properties compared to the conventional Si3N4. [It has JIS 3-point bending strength : 1600-1800 MPa; Charpy impact value : 14-16 kJ/m2.] The developed Si3N4 powertrain part as a adjusting shim with a mirror-finished surface has been evaluated by the motoring apparatus about the fracture behavior during the valve bouncing and the friction torque of a cam shaft. The result shows that about 50% higher shock resistance of developed Si3N4 shim and 10-20% reduction of friction torque. By using the shims, 2-3% improvement ratio of fuel-consumption has been proved by the actual driving test.
This paper describes the crack formation process by a scratching on the surface of glass. The process is observed dynamically with a dynamic observation a.id recording system which was developed by the authors. The mechanism of the generation and growth of cracks is discussed based on the observation and the three dimensional structure of cracks. Furthermore, the influence of scratching conditions such as scratching speed or loading weight on the crack formation process is discussed. The main results obtained are as follows; (1) Cracks can be classified into three types, that is, cracks A, B, C in Fig. 10. (2) After a scratching indenter passed over, crack C grows in the lateral direction at the crack front of crack A which has been already formed. (3) Crack B is also a lateral crack, while it grows more puickly than crack C directly from the top of the indenter. (4) The crack formation process is significantly affected with scratching conditions.
The slide bearing guideway gives much greater frictional force than the rolling bearing guideway and the hydrostatic bearing guideway, and lowers the slide motion accuracy of the perpendicular guideway mechanism for the surface grinding machine. But when dynamic load is applied to the wheel head, frictional force absorbes vibration energy, and therefore, the slide bearing guideway is much more advantageous than other bearing guideway in improving the coupling stiffness. This paper proposed the composite bearing guideway mechanism. This mechanism has a feature that the conventional slide bearing guideway is used for the front side slide surface, and the hydrostatic bearing guideway is used at the opposite side. The new mechanism was solved to overcome the disadvantage of the slide bearing guideway. As a result, this slide motion accuracy showed a different aspect, with a load pressure at the slide bearing guideway side of 62.5 kPa as a boundary. At a load pressure of 62.5 kPa, the slide motion accuracy became 0.3 μm/40 mm within the limits of this experiment.
A cut-away sintered carbide tool for turning operations has been proposed and successfully employed to improve the machinability of a 18%Mn-18%Cr manganese steel (HB=241). Both the chip contact length on the rake face and the chip flow direction can be uniquely determined by the energy method when the restricted length is assumed to be proportional to the real uncut chip thickness in the direction of chip flow. The optimum contact length is found to be 1.25 times as large as the real feed, which is slightly wider than that in the two-dimensional machining. The predicted cutting forces, cutting temperature and tool wear are all in good agreement with experiments. The restriction of the contact length causes the cutting forces and the heat generation on the shear plane and at the tool-chip interface to reduce, leading to the decrease in tool temperature. As a result, the wear on the rake face of a P20 carbide tool is lessened by 10% in the dry turning of such a high-hardness metal.
Laser plating of fine gold spots was carried out in a flowing solution and the effects of flow rate, argon laser power, and cathode potential were studied on obtaining a high deposition rate and good controllability of the size of deposited spot. High deposition rates of several μm/s are obtained under solution flow conditions. In situ observations revealed that vigorous boiling occurs even in the flowing solution and laser plating is enhanced by strong microstirring due to ejection of bubbles. The main function of solution flow is to remove bubbles rather than to reduce the thicknees of a diffusion layer. The relation between deposition rates, v (μm/s), and flow rates, u (m/s), is written in an empirical equation, v= Cua (C, a; constant), and the values of the exponent are about 0.3 at laser powers less than 1.5 W and about 0.5 at laser powers more than 2 W. Deposition rates increase with increasing laser power, and then they are saturated at laser powers more than 2 W. This is explained by saturation of the effect of solution flow on removal of bubbles, which cause scattering of laser beam and an increase in electrical resistance of the solution. Solution flow has a cooling effect for locally heated solution, resulting in reducing the size of deposited spots.
Shear mode grinding has recently much attention for the machining of brittle material such as a glass, ceramics and silicon. This study presents the effects of a newly developed ultra high speed grinder, which can achieve speeds five times greater than conventional grinders. Scratching modes on a surface of glass ground with a single point diamond were observed in detail by scanning tunnel microscopy. It was found from the experiments that the grinding mode depends exceedingly upon the circulating speed of the disc. The depth of cut observed with STM was about 20-30% smaller than calculated one. Grinding mode changes due to the shape of stylus tip and the cut of depth is influenced by crossing of the scratches.
Aramid fiber reinforced rubber (AFRR) is a new composite material developed for transmission belt. Transmissibility of belt is considerably dominated by frictional characteristics of belt surface contacting with pulley. Transmissibility of belt just like as V-ribbed belt made of AFRR, which is finished by grinding, is influenced by grinding conditions as well as its material. In this paper, by investigating the surface generation process in grinding AFRR with diamond wheel, a grinding technique for a required transmissibility which is represented by coefficient of friction on ground surface of AFRR, is made clear. Main conclusions in this paper are as follows : (1) The coefficient of friction on ground surface of AFRR, which is determined by a projecting length of aramid fiber from matrix surface, increases as the projecting fiber length decreases. (2) In the steady grinding state, a required projecting fiber length of AFRR is given by controlling grinding conditions with grinding force ratio. (3) There exist the matrix removal region for lower initial length of projecting fiber or the fiber removal region for higher one, than cutting depth of grinding wheel, and therefore both projecting fiber length and matrix size can be adjusted by either grinding of the two regions.
An experimental investigation was conducted for evaluating the effect of oxidation in air and flexural strength of the hot pressed silicon nitride, containing Y2O3 and Al2O3 additives. The effects of oxidizing variables, temperature and time were investigated. The specimens were high efficiently ground before oxidation, and examined the relation between the oxide conditions and flexural strength. The grinding machine was a machining center with a high rigid spindle. The surfaces of the oxidized specimens were covered with a uniform oxide layer. It was found that the oxide layer consisted of SiO2 and Y2O3·2SiO2, from the X-ray diffraction analysis. After the oxidation, the compressive residual stress in the ground surface was decreased. The flexural strength of the oxidized specimens was significantly increased at room temperature. For recover the strength of the high efficiently ground specimens, there were suitable oxidizing conditions. After the oxidation at 1200°C for 24 h, the flexural strength was most increased in this investigation.
In order to fabricate grazing incidence X-ray mirrors made of hard and brittle CVD-SiC, a large 5 axis control ultra-precision grinding machine has been developed. The machine must be capable of generating non-axisymmetric aspheric surfaces by ductile grinding. So as to obtain precise profile accuracy, new mechanisms such as flexible coupling, guide rails with fine deformation mechanism and leveling blocks for correcting warp of guide rails are applied to hydrostatic linear slideways. As experimental results, excellent straightness of X axis slide of 0.05 μm in a 500mm traverse is obtained on the grinding machine. Non-axisymmetric aspheric mirrors have been ground within a profile error of 0.9μm with the machine.
The drilling tests were performed on austempered ductile cast irons (ADI) with 2-3% silicon and 100-415/mm2 graphite nodules to clarify the factors influencing the machinability of ADI. The machinability of each specimen was evaluated using high speed steel drills of 6mm dia. The ductile cast iron specimens were austenitized at 900°C for 1 hour and then held at 375°C for 2 hours. The increase in graphite nodules raises the machinability of ADI, while the silicon content of matrix has little influence. The larger the number of graphite nodules is, the finer and the less the γ-pools are. The refinement and reduction of γ-pools suppress the fluctuation of thrust and torque loads. Furthermore, the larger number of graphite nodules promote the formation of flow type chips, which also contribute to the longer drill life.
This paper presents the minimum specimen thickness limit (Tmin) of copper alloys (brass, 2 kind of phosphor bronze and nickel silver). Standardized hardness blocks were tested by HRB·HRBQ, HR 30 T·HR 30 TQ scales, errors of the similarity in hardness were found to be lower than 1% (2nd report). To test thinner specimen, scales are extended to HR 15 T·HR 15 TQ. Hardened steel spot anvil (SSA) and diamond spot anvil (DSA) are used, both spot diameters are 4 mm. Criterions of the Tmin, are : (1) Difference of hardness measured with SSA, DSA is lower than ±0.1 hardness unit. (2) The bulge or mark appears on underside is barely visible. (3) The elastic deformation of SSA is reasonable that is 0.2-0.9 hardness unit depending on the specimen thickness. This test uses specimens which are extracted from usual factory products. They were hardened by cold rolling and hardness were changed by working ratio, heat treatment, tension annealing, etc. Therefore the hardness of these copper alloys generally vary throughout thickness of specimens and the thickness is decreased by etching (HNO3) and polishing, the hardness changes. The values in the test results shoud be taken as average ones. The hardness test data are fitted with second or third order polynomials by least square method. The above 5 materials are divided into 2 groups. (1) brass, phosphor bronze (Bs, PB) and (2) Nickel silver (NS) in the relation between Tmin and hardness. The hardness for the same Tmin differs significantly. HRB 3.7-7.3, HR 30 T 1.8-3.1, HR 15 T 1.8-3.0, in middle and high hardness range (H, EH, SH). But the difference between polynomials within the same group is lower than 1.0 unit (except phosphor bronze ≤ 1.4).
This paper describes an experimental trial for detection of defects (or special features) on a pipe inner wall using a laser-beam scanning sensor. A strategy in which two simple threshold levels are set for the sensor outputs is proposed. If either threshold is exceeded, the sensor classifies the corresponding points as defective. There is, however, an epicenter caused by the difference between the center of the sensor and the center of the measured pipe. Therefore, the sensing system easily confuses actual defects and the signal caused by the epicenter. To avoid this problem, a digital notch filter is derived by using a series of three points measured while scanning around the inner circumference of the pipe. This filter computationally eliminate the epicenter. To determine the effectiveness of the algorithm with the thresholds and the filter, a model pipe that has some defects on its inner wall is constructed. The algorithm precisely detects the two holes as well as a disconnected coupler and three other couplers.
In this study, an optical noncontact measuring instrument has been developed to measure the 3-dimensional shape of an object with a free-form surface. A linearly polarized laser from the instrument is focused on the object surface to be measured. The astigmatic focus error method has been applied to the instrument in order to achieve a focused positioning signal of the object surface. The depolarized component of the light backscattered from the object surface has been detected as the signal. In the previous report, the power of the linearly polarized laser incident on the object surface was kept constant, and two detectors were used in the instrument. In this study, properties of the developed instrument are improved when light-detecting portions of the light detector are changed and the power of the laser light incident on the object surface is varied in order to obtain an appropriate detected light power. Only one detecter is used. Using this instrument, 3-D profiles of diffuse reflection surfaces and metal surfaces on which there are both specular reflection and diffuse reflection, can be measured.
In this paper, a new five-degrees-of-freedom fine motion mechanism whose rigidity is high is proposed, and the construction and the experimental results are also described for the characteristics of newly developed three-degrees-of-freedom mechanism. This mechanism comprises three wedge-shaped plates and six multi-layered piezoelectric actuators. The mechanism which requires neither guide plane nor lubrication enables it to move without any friction, wear and badklash. The maximum movements of the stage were 3 μm in X-direction, 12μm in Z-direction and 12 second of arc in β-direction. The positioning resolutions in the translational and rotational directions were less than 0.01μm and 0.01 second of arc, respectively. The loading capacity was 400N. The positioning errors and the motion error were less than ±0.01μm and ±0.03 second of arc. 1 μm step positioning in X-direction interfered with other directions transiently because of difference of the contraction and expansion velocities of the piezoelectric actuators.
This paper describes a surface characterization method of an ultra-precision machined surface of Si wafer by means of photo-reflectance spectra in the region from visible to ultraviolet range. To detect small change of reflectance spectrum, differential reflectance (D.R.) spectrum is applied which means the relative differences of reflectance between a testing specimen and reference. A reflectometer system is designed to detect D.R. of the order of 0.01%. The reproducibility of this system is tested by measuring D.R. spectrum between two surfaces which are simultaneously cleaned by aqueous solution of HF, and the magnitude of the obtained D.R. spectrum is less than 0.05%. To investigate the influence of storage of Si wafer, D.R. spectrum is measured between the specimen stored in nitrogen gas ambients for one week after the HF cleaning and just HF cleaned. The maximum magnitude of the obtained D.R. spectrum is less than 0.3%. The influence of storage can be detected using this system. It is concluded that the measurement of D.R. spectrum is useful for the characterization of ultra-precision machined surface of Si wafer.