Molds and dies with sculptured surfaces are usually fabricated using numerically controlled (NC) 3-axis milling machines with a spherical cutter. Fine and precise visualization of the workpiece shape resulted by an NC milling operation is necessary for manufacturing a product with good surface quality. Result shape of the workpiece can be computed by geometrically simulating the milling process using solid models of the tool swept volume and the stock object. Milling simulation method based on a discrete representation of the workpiece model is widely used. This method approximates the workpiece shape as a collection of thin cubic solids called dexels. Direct displaying of dexels is not suitable for the visualization because of the staircase error remaining on the model surface. In this paper, the authors propose two technologies for improving the visualization quality of the workpiece model in the dexel representation. The first method realizes correct and smooth rendering of the model using the surface normal information at the top point of each dexel. In order to realize the precise rendering without consuming the extra memory, the second method localizes the visible portion of the workpiece and transforms only such portion to very fine dexels. An experimental program is implemented and high quality visualization of some complex milling results is demonstrated.
The purpose of this research is to develop a CAD/CAM system based on Boundary-Map geometric model. Geometric model used in a current CAD/CAM system has been developed to be suitable for representing 3D shapes precisely. When these geometric models are applied to CAM system, some problems occasionally arise in an accuracy, an execution speed for collision check, machining error due to a small deformation caused by cutting force and heat and so on. Therefore a new geometric model named "Boundary-Map geometric model", which is suitable for CAM functions, has been proposed . This paper describes the data struc-ture of Boundary-Map geometric model and three functions, which are geometric generation, geometric modification and geomet-ric rendering, to use for the CAD system. Moreover, basic algorithms to generate cutter location data and collision check betweenn a tool and work piece have been newly proposed. From the result of machining tests by employing the proposed CAD/CAM system, it is confirmed that the Boundary-Map geometric model satisfies basic functions required to a common CAD/CAM system.
In stereo-lithography fabrication process, photo-polymer resin is supplied for one layer thickness at first, then photo-polymerized selectively by laser beam, and by repeating the process layer by layer three-dimensional solid parts are fabricated. In this process, since a solidified layer must be connected to the previous layer, excessive exposure is needed to solidify the resin beyond one layer thickness. Therefore surplus growth caused by over-curing occurs at the bottom surface of the solidified layers and leads to a dimension error in the height direction. If the thickness of the surplus growth is predicted beforehand, the accuracy of an object in the height direction can be improved by cutting a few bottom surface layers from slice data in software. In this paper, a formula used to predict the thickness of the surplus growth is derived from the theoretical analysis about the mechanism of the surplus growth, and the validity of the formula is confirmed by experiments.
Labor-reducing robots need to be powerful, while to be able to work in small spaces, a micro-robot must be small. As both requirements are fundamentally different, research for micro-robots requires an approach different from that for large robots. This research has focused on elemental technology for analog electronic watches: compactness. thinness and low power consumption. As a result of this analysis, thin structures were taken as the starting point. By making each functioning unit a board-like structure and arranging the units side by side, small robot (approximately 1 cm3) was made. Because each unit is independent, individual optimization is possible. Modules can thus be assembled variously for different functions. Component parts are basically thin boards that are easily assembled by stacking in one direction to achieve a thin structure. Furthermore, because modules are simply aligned with the inner sides of the body and inserted with the required wadding, there is no need for all units to have high accuracy dimensions. Although the robots have no functions for performing specific tasks, they have proved effective in soothing nerves.
The capability of a small-sized spiral groove hydrodynamic journal bearing to keep the lubricating oil in the bearing clearance is one of the most important performances of the bearing, especially when it is applied to an HDD spindle motor system. In this paper, the oil-keeping ability of the bearing is investigated theoretically under an analytical model considering two basic mechanisms concerning the oil flow in the bearing; one is the pumping force to drive the oil flowing axially in the bearing clearance, when the rotor is in a non-concentric and tilting state against bearing center axis, and the other is the compensating force, which is derived by the meniscus of the oil at the bearing ends or by the occurrence of axially asymmetric distribution of the oil film region resulted by the axial oil flow. The tolerable unbalanced mass of the rotor is calculated supposing that the non-concentric and tilting attitude of the rotor is attributed to the synchronous whirl due to the unbalanced mass of the rotor.
Positioning tables using preloaded ball screws show nonlinearly elastic characteristics between small torque input and table displacement within microscopic range of several micrometers. The elastic property is available in nanometer positioning control because the displacement reveals no sticking and responds to the toque input, even small. However, it has not been known how the elastic property is influenced by conditions of the preload or input torque. This study aims at clarifying the elastic property of preloaded ball screw in microscopic range under various conditions, in order to apply the property to ultra-precise positioning with nanometric resolution. This report presents some experimental results on the elastic property of ball screws which are preloaded by deferent methods.
We use scratch-tests to measure the adhesion force of gold/platinum/titanium thin-film electrodes patterned on planar-lightwave-circuit devices of optical modules. In the patterning process, a sacrificial copper layer is deposited by vacuum evaporation, and the thin-film electrodes are patterned both on SiO2 over glass layers and on deep pits. A microscratch tester is used to measure the adhesion force between the SiO2 over glass layer and the thin-film electrodes: the critical load is 157.7 mN (16.08 gf) and the shear stress is 1.36 GPa. Energy-dispersive X-ray spectroscopy (EDX) of the scratch surfaces of the thin-film electrodes reveals that the peeling interface of the thin-film electrodes is the interface between the gold layer and the platinum layer. Moreover, a depth profile of the thin-film electrodes by Auger electron spectroscopy (AES) shows that there is no carbon contamination in the thin-film electrodes, no oxide layer, and no copper contamination between the titanium layer and the SiO2 over glass layer.
This paper discusses a new probe technique, the so-called laser trapping probe, whose principle is based on the dynamic properties of optically trapped dielectric particles and the Linnik microscope interferometer. Computer simulations for trapping in air and theoretical analysis for interference fringe patterns are performed. By using the newly developed laser trapping probe experimental system, single-beam gradient-force optical traps of silica particles with the diameter of 8.0μm as microprobes are successfully demonstrated in air. And then, positional detection principle is established based on fringe changes with small displacement of the laser trapped probe sphere while approximating it to work surfaces. Measurement results for glass microspheres having NIST traceable mean diameter of 168±8.4μm show its potentials as the 3D nano-position sensing probe for nano-CMM.
Signal intensity of the light diffracted from the superimposed dual transmission gratings is affected by the higher harmonic distortion (deviation from sinusoidal variation). In this study, the method using the modulated pitch grating that was proposed preciously was extended to more general conditions. The design method for modulating the grating was analyzed in detail and the distortions in the order up to the 13th were removed in the experiment using the proposed grating.
In this study, the optical technology to detect small particles adhering to a wafer and crystal originated particles(COPs)existing in the wafer, whose diameters are approximately 0.1μm, is theoretically developed. The technology to separate COPs from detected particles is also developed. The intensity distribution of light scattered by particles and COPs is calculated using the Maxwell equation under the assumption that they are illuminated by laser light. The finite difference-time domain(FD-TD)method is used to solve the Maxwell equation. The following results were obtained by these calculations. Both particles and COPs are detected when an Ar-ion laser(λ=488 nm)with P-polarization is illuminated perpendicularly downward onto the wafer. and the obliquely scattered light is detected. Only particles are detected when a YAG laser(λ=532 nm)with S-polarization is illuminated obliquely and the light scattered perpendicularly upward is detected. On the basis of the abovementioned results. it is theoretically verified that both particles and COPs Larger than 0.1μm in diameter are detected and recognized independently.
A new detective method for small convex and concave defects, which are observed in surfaces of optical films, have been proposed. The method is based on a phenomenon that regular patterns in a reflected image is blurred by the existences of their defects under an illumination having regular patterns. An algorithm to extract only blurred zones as defective zones is shown. The method is applied to defects on several sample films. The results show that only defects are successfully detected even if the films are curved and warped dynamically. Also the effectiveness of the method in manufacturing sites is shown by the robustness against the fluctuation of intensity of the illumination and executing time.
The coating effects of organic polarity substances on the orthogonal cutting behaviour have been investigated for as-annealed pure aluminum surface and work-hardened one. The work-hardened surface for cutting is obtained by pre-cutting to the as-annealed aluminum. The coated material on as-annealed or work-hardened surface is liquid paraffin containing 0-100mass% oleic acid as organic polarity substances. Orthogonal cutting speed is 1.67mm/s and cutting depth is 0.02mm. The following results were obtained. In work-hardened specimens, the coating of liquid paraffin containing over 0.lmass% oleic acid brings the decrease of cutting force, the improvement of cutting surface roughness and the thinning of chips. The coating effects are never observed not only for work-hardened specimens which are coated liquid paraffin containing 0-0.04mass% oleic acid but also for as-annealed specimens which are coated 0-100mass% oleic acid. Chemical interaction between molecules of oleic acid and dislocation might promote the above effects.
Many kinds of burrs are formed in various fabricating processes. These burrs are often manually removed even in modern factories. Therefore, these burrs make troubles on production lines in terms of automation, quality of products and working environment. In this paper, the burr formation mechanism on the exit side in drilling of metals is discussed. The idea is that the burr formation mechanism is equivalent to that of the deflection of cantilever changing the thickness under equiload. On the basis of the idea, authors have designed the burrless drill, in which the corner of cutting edge is cut by a little larger compared with a normal drill. The effect of the burrless drill is discussed in the present paper.
In OD-Blade slicing technique frequently used for high precision slicing, straightness and the reduction of waviness in a sliced groove surface needs to be improved further. This study aims at establishing the vibration OD-Blade slicing method that can decrease slicing force and examining slicing accuracy on vibration slicing experimentally. Thus, the self corrective effect of an OD-Blade using applied vibration on slicing groove accuracy should be compared with the conventional method without using applied vibration. In this paper, the slicing accuracy represented by waviness and edge chipping on the slicing groove are examined especially when an asymmetric OD-Blade is used. According to the experimental results, it is clear that the vibration slicing method reduces the elastic deformation of the OD-Blade during slicing and decreases the waviness and edge chipping owing to the OD-Blade self corrective effect. In conclusion, the vibration slicing method is capable of highly accurate slicing as compared with the conventional method.
This paper presents experimental results of the wettability and atomic diffusibility of liquid metals on clean solid surfaces. Six types of liquid metals; Au, Ag, Cu, Al, Fe, Ti, and three types of substrates; tungsten, glass-like carbon, highly oriented pyrolytic graphite (HOPG), are used as the specimens. Contact angles of liquid metals are measured with good reproducibility using a continuous Ar sputter cleaning process as is introduced in the previous paper. Interaction energies of these systems are obtained. As liquid Fe has different diffusibility for two carbon substrates, glass-like carbon and HOPG substrates, atomic concentrations of the substrate surfaces are investigated using scanning Auger electron spectroscopy. Consequently, it is found that liquid Fe has atomic diffusibility with a glass-like carbon surface but not with HOPG (001) surface.
This paper reports the study on manufacturing technology of a small and powerful AC servo motor which used for industrial devices. This motor has a linear shaped core which is divided among teeth and connected by thin bridges. In coil winding the linear shaped core is wound by several nozzles. After winding, the linear shaped core is bent as a similar conventional circular stator. This manufacturing method brings the coil density to improvement of 30-40% and the optimization of the width of the slot opening. As a result, it can be realized that 40-60% of the motor capacity has decreased in comparison with before.
Effects of tool rake angle on ductile-brittle transition in diamond turning of single crystal silicon are investigated. Straight-nosed diamond tools are used and rake angles are varied from -80°to 0°. Chips and machined surfaces are observed using scanning electron microscope and atomic force microscope, and micro cutting forces are measured with a piezoelectric dynamometer. It is found that critical depth reaches the maximum at medium negative rake angle around -40°as the result of appropriate hydrostatic pressure. The ductile-brittle transition behavior becomes remarkably different as rake angle is varied. The cutting forces decrease when the cutting mode transits from ductile to brittle at small negative rake angles, whereas at large negative rake angles they keep increasing. Large negative rake angle leads to significant downward material flow and subsurface plastic deformation. Stagnation region is formed in front of the cutting edge, which destroys the transcription accuracy in ductile regime. In brittle regime, chip formation behind tool flank face is also observed, which indicates that lateral crack occurs along the elastic-plastic boundary after the tool pass due to the elastic response of large subsurface deformation.
Electronic substrates on which precise circuits were already formed can be cleaved without leaving any micro-cracks on the cleaved surface by a thermal stress cleaving using a line heat source. In order to understand the crack extension behavior, time-dependent stress intensity factors of long and short cracks pre-induced from the end of a thin plate are analyzed when a thin plate is heated by a continual line heat source on the crack line. In the case of a long crack, the stress intensity factor is almost independent from the crack length but, in the case of a short crack, the factor is strongly dependent on the crack length. Accordingly, two different modes of crack extension appear. The condition, which mode appears, can be clarified from the comparison of stress intensity factors of two cases. With high heating power, a strip with narrow width can be cleaved stably. For stable cleaving, therefore, it is essential to use high heating power so long as the heat damage doesn't appear. This conclusion agrees well with experiments using glass plates.
This paper deals with the method of collision-free tool attitude determination for five-axis control machining using ball end mills. Five-axis control machining cannot only cope with the fabrication of complicated shapes, but also offers numerous advantages such as reasonable tool employment, great reduction of set-up process and so on. However, most of the present CAM systems for five-axis control machining have a lot of restrictions concerning tool collision, object shape, machining method, and so on. For that reason, if the obtained cutter location data is unsatisfactory, there is no way to modify the data, and a considerable time is consumed in order to calculate a desirable five-axis control tool path. In this paper, an effective method is proposed, which can determine a collision-free tool attitude on the basis of the original two-dimensional configuration space. Our two-dimensional configuration space shows the relationship between tool attitudes and the existence of tool collision at each cutting point. Thus, the calculation method of configuration space is at first extended, taking into the account of the tool shape data to be used such as diameters of holder and shank parts, and taper angle. Furthermore, the proposed method enables us to reflect machining strategies, that is, the user's machining intention on the basis of empirical knowledge. In this paper, the safety first machining strategy and the rapid determination of tool attitude are proposed by utilizing the Delaunay net. The method has been found effective experimentally for generating five-axis control tool paths.
This paper describes the characteristics of the ultra-high speed grinding and the influence of wheel surface speed V on a grindability of the grinding material. The grindability can be estimated by the Cp value that is product of C and p, where C is plowing coefficient of the material and p is the yield pressure acting onto each cutting grain. The Cp value represents a plowing energy for a unit volume of the material, i.e. the specific grinding energy for plowing, and can be calculated from the normal grinding force Fn under the condition of constant v/V value (v: workpiece speed) in various wheel depth of cut Δ. In the experiment, an ultra-high speed grinding machine was used, whose maximum wheel surface speed was 400 m/s. The change of the grindability of the material with an increase of wheel surface speed V from 30 m/s to 300 m/s was recognized through the grinding tests using cast iron workpieces. The main results obtained are as follows: (1) Cp value increases with an increase of V on shallow grinding conditions. (2) Cp value decreases with an increase of V on high-efficiency conditions. This tendency becomes more remarkable at the larger Δ under a constant v/V value. (3) Wheel wear decreases as the wheel surface speed V increases.
This paper presents an analytical simulation method to estimate a machine profile in spherical milling with a ball-nosed spiral cutting edge tool. The height of machined profile is regarded as the cross point of the moving cutting edge and a specified normal line. The geometric equations determining the rotating angle of the tool and the cross point were formulated and solved originally in numerical calculations of Newton-Raphson method. The phase difference angle of the spiral cutting edge was measured and embedded into the formula. By developing the faster method to get the initial solution of the numerical calculations, a graphic simulation of the machined surface can be displayed three times faster than that in a case of a flat cutting edge. Also the discriminant of the interference between the flank of the tool and the machined surface has been formulated and introduced into the simulation method. Then the exact profile of machined surface could be estimated by the presented method. Through the formula development and graphic simulation, the landscape features of machined surface have been well recognized and the cusp height could be exactly estimated. Experimental simulations have been illustrated and the conclusions are described briefly.