Key Engineering Materials Vol. 516

Abstract: A structural analysis model including the temporomandibular joint (TMJ), external auditory canal, tympanic membrane, auditory ossicles and cochlea was made. Loads through the TMJ were applied to this model in three-dimensional finite element analysis. It became clear that stress concentration occurred at the lower portion of the external auditory canal, superior tympanic portion (attic), incus long crus, stapes crus and inlet of cochlea. The lower portion of the external auditory canal and attic are favourite sites of cholesteatoma (pearl tumour). Incus long crus and stapes crus are favourite sites of auditory ossicular defects, which are the cause of otitis media. Damage of the cochlea entrance causes high-frequency hearing loss which is age-related.

Abstract: A novel diaphragm-control restrictor (DCR) is proposed for improving the performance of the hydrostatic-bearing spindle used in machine tools. The unique function of the proposed DCR is the wide adjustability of its restrictor characteristic. A two-step restriction system is adopted for the DCR; a spool restrictor is used as the first step restrictor. By changing the restrictor resistance of the spool restrictor, the effect of the active control in the DCR, the second step restrictor, can be altered. The proposed DCR is incorporated into a hydrostatic bearing supporting a precision spindle, and the performance of the bearing is analyzed. Numerical and experimental analyses show that the stiffness of the hydrostatic bearing with the proposed DCR can be five times as large as a conventional hydrostatic bearing of the same dimensions. Analysis of the dynamic compliance shows that the effect of the active control can be observed up to 20Hz. These results show that the proposed DCR is useful for improving the performance of the hydrostatic-bearing spindle in precision applications.

Abstract: Recently, technology for electric vehicles (EV) and hybrid vehicles (HEV) has been focused on by the automotive industry to address environmental problems including CO₂ reduction [. In particular, in HEV, planetary gears are used to control differential rotation of the motor, engine and generator. For these vehicles, the noise level inside the vehicle is low because the motor is used as the main power source. As a result, further decrease of gear noise is desired compared with the conventional planetary gear mechanism. However, research into the gear noise of the planetary gear mechanism is extremely scarce. Therefore, in this study, we focus on the three axes of I/O rotation, and a new method of measuring the meshing force of the planetary gear mechanism. In this report, a gear-driving device, which is able to make 3-axis differential rotation, was designed for experimentation.

Abstract: In recent years, studies have been conducted about creating metal moulds using a five-axis controlled machining centre with ball end milling. Most of these reports concern the programming of CAM based on geometry. However, there have been few reports related to polish-less finished surface. Furthermore, a specular surface like a mirror and finishing under a constant angle between ball end milling and the work piece have not been investigated. Therefore, this paper deals with the gloss of the machined surface when feed rate and pick-feed rate are changed to maintain constant surface roughness considering tool run-out under the condition that the angle between the tool and work piece in contact are inclined at 15. However, by changing the combination of feed rate and pick-feed rate, various specular changes and direction of disposition of reflected light were obtained. Therefore, we suggest a new method of evaluating the gloss of these finished surfaces. Comparing results by the proposed method with ones by a glossmeter, it is clear that an appropriate ratio of feed rate and pick-feed rate is important for obtaining finished surface. Moreover, it is demonstrated that the proposed method is effective for estimating the gloss of the machined surface.

Abstract: Based on the ultra precision machine tool, using Matlab/Simulink and considering the linear and nonlinear factors of the processing such as environmental vibration, machine movement, servo control technology, work piece material, cutting force and built-up-edge, the simulation system of ultra precision machining for microstructured surface based on fast tool servo (FTS), which integrated machine control system, machine mechanical system and surface generation, was established and verified by processing sinusoidal microstructured surfaces. The experimental results showed the simulation output errors were 15 % or so, and the simulation system could predict the microstructured surface morphology, optimize the processing parameters and provide support for follow up studies.

Abstract: Ultra smooth and defect-free 4H-SiC wafers are strongly demanded in the next-generation power semiconductor devices. However, such SiC substrates are relatively difficult to machine because of their mechanical hardness and marked chemical inertness. In this study, we attempt to polish 2-inch 4H-SiC wafers by our proposed method, which utilizes Fe particles and a hydrogen peroxide solution. The processed surface was observed by phase shift interferometric microscopy, Nomarski differential interference contrast microscopy and atomic force microscopy. These observational results show that the surface roughness was improved over the entire 2-inch wafer by our proposed method. These results offer useful information for preparing a smooth SiC wafer.

Abstract: Three-dimensional shapes created from photographic imagery using a photometric stereo method is restored in the present study. We used one object and one digital camera. The source of light was moved and the camera took a picture of two or more object shape data. The radiance value of the obtained photographic imagery was requested respectively. It was restored to three-dimensional geometry by calculating the normal vector from the radiance value, and combining the data of the photographic imagery. As for this method, it is well-known that application is difficult for objects that have lustre. Therefore, an improvement was attempted using spline interpolation. It has been understood that the method which reproduces it by using spline interpolation as a result is effective. Furthermore, because an error margin is caused when an object with colour variation is reproduced, an improvement was tried. First of all, the colour component of the image was extracted. Then, the image with a small change in brightness was chosen and reproduced. Consequently, a shape near the theoretical value was able to be reproduced for the reproduction of a two-colour object including white.

Abstract: This paper presents a new pulse generator for cutting of polycrystalline diamond (PCD) by micro wire-EDM. Three pulse control methods (AC power supply pulse control method, fixed pulse width modulation pulse control method and improved AC power supply pulse control method) have been proposed to achieve high frequency and low energy discharge pulses. The improved AC power supply pulse control method enables the pulse generator to provide a period of 20 μs off duty cycle followed by a period of duty cycle for reionization of the dielectric in the spark. Compared to the other two methods, the improved AC method can provide smaller peak current and discharge duration and thereby achieve a smaller slit width and better surface finish. Tests revealed that the developed power supply using anti-electrolysis circuitry and a digital signal processor-based pulse control circuit can provide very low discharge energy pulses with a frequency of 200 KHz, discharge duration of 0.75 μs and a peak current of 3 A. Experimental results demonstrate that the proposed pulse generator can achieve a feed rate of 0.4 mm/min, a surface finish of 0.53 μm R_a and a damaged layer of 5 μm on PCD surface through proper machining settings.

Abstract: Numerical controlled local wet etching is a novel non-contact deterministic figuring method in ultra precision optics fabricating and functional material manufacturing fields, and the cross-sectional shape of the traditional removal spot is a simple cylinder, so the removal function has no adjustability. In order to create more practical and regular removal function, an eccentric rotation system is introduced to improve the LWE system. By controlling the eccentricity, it can achieve varied shapes removal function. When the rotary axis is controlled to a proper eccentricity, the removal function can be close to the Gaussian function. Moreover, the theoretical calculation and experimental validation are coincident and can give the research a steady foundation. The improvement not only can increase the adjustability of the removal function in LWE, but also can expand its applied field and provide reference for other ultra precision machining methods whose removal function does not have circular symmetry.

Abstract: Recently, the idea of sustainable development has become more and more important. In the previous report, we focus on downsizing industrial goods and discuss the environmental load of industrial goods. As a result, by downsizing machine tools we verified that the environmental load of mother machines in making copies of themselves could be reduced. On the other hand, we verified that the environmental load of use of the machine itself increased relatively. Thus, in desktop machine tools, we verified that reducing the environmental load of use of the machine itself would increasingly become an issue in the future. In this paper, we discuss methods of using desktop machine tools from the aspect of power consumption. As a result, we verified that in cutting along the linear-axis and rotational-axis, we have to consider back clearance after cutting.