This paper describes a method to improve allocation and re-allocation of resources in manufacturing systems, such as machine tools and robots that are linked by carriers such as AGVs. The proposed method uses the result of scheduling as an index of suitability of the resource allocation. The behaviors of AGV are analyzed and included in the production scheduling problem. The production scheduling problem is solved by employing some well-known dispatching rules. The search for the best scheduling is executed for different assignment of resource allocation, and the suitability of the resource allocation is evaluated based on the schedule obtained. The procedure is repeated to improve the allocation of the resources by applying simulated annealing method. The validity of the proposed method is verified by computational simulations for typical production scheduling problems.
Computer Tomography (CT) has been used for inspection purposes in the industry today. It is also used for measuring shapes of mechanical parts. In order to generate shape information from CT data, it is general to use Marching Cubes (MC) method which reconstructs triangular mesh models (MC mesh). Nowadays, because of the high resolution of CT devices, MC meshes become so dense and large to process on ordinary PCs. We propose a method to convert such MC meshes into the form of triangular strips so that they can be compressed and efficiently displayed. The method is based on characteristics particular to the MC meshes, that is, the vertices of the MC meshes are located on the three dimensional grids. In this paper, we describe this method to generate strips from MC meshes and also show experimental results using a realistic example to prove the effectivity of the method.
Electrostatic linear motor for vacuum environment is reported in this paper. The authors have developed high-power electrostatic linear motor called Dual Excitation Multiphase Electrostatic Drive (DEMED). DEMED is a linear synchronous motor and consists of pairs of thin plates. It possesses a power per weight ratio of 230W/kg and acceleration of over 100G in open loop systems. These performances are higher than those of typical electromagnetic drives. Previously, DEMED has been studied in dielectric liquid environment. In this study, DEMED for vacuum environment is fabricated, and its characteristics in vacuum environment is investigated. The fabricated motor equips mechanical guides for vacuum environment and a function of built-in position sensor. Estimated maximum force density of 2.82kN/m 2 at driving voltage of 3.4kV is obtained through experiments under pressure of 10 -4Pa Capability of electrostatic motor application in vacuum environment is verified.
A one-dimensional sensor is developed for the purpose of an analog probe with nanometer order resolution for coordinate measuring machines. The manufactured sensor has parallel-spring structure, to which a single-crystal silicon of 3mm cube is broached and on which the piezoresistances are processed. The piezoresistance can be constructed in a Wheatstone-bridge, and a signal output can be obtained. The result of characteristics evaluation of a single parallel-spring sensor shows that the elastic compliance is 3 micrometer/N, the measuring resolution is 15nm and the eigenfrequency is 29kHz. These values are well in agreement with the theoretical values. From theoretical consideration, it is estimated that the measurement ranges are 180 micrometers and the minimum eigenfrequency is about 10kHz in a 3-dimensional probe.
This paper describes a novel phase-shifting point diffraction interferometer (PS-PDI) that employs 2 fiber-optic point sources, as a tool for measuring surfaces for SOR and EUV mirrors with sub-nanometer accuracy using visible light optics. In conventional interferometry, the figure accuracy of the reference surface determines the measurement accuracy. We therefore need an absolute reference surface with sub-nanometer accuracy. One of the qualified surfraces is a spherical wavefront which comes from point light source. The proposed PS-PDI system uses 2 single-mode optical fibers as point light sources. The system is applied to the measurement of a commercial spherical concave mirror with 500 mm in radius of curvature and 30 mm in diameter. The repeatability of measurement for the mirror is estimated to be about 3 nm in peak-to-valley value at the wavelength of 632.8 nm in He-Ne laser.
Carbon onions were synthesized by heat treatment of diamond clusters or sub-micron particles that are less than 0.5 μm in diameter. X-ray diffraction and transmission electron microscopy were employed to evaluate microstructure of the carbon onions. Solid lubricant properties of the carbon onions were measured by ball-on-disk type friction testing using silicon wafers and steel balls in air and vacuum. The heat treatment up to 1730°C in argon ambient at atmospheric pressure results in synthesis of carbon onions in various particle sizes which correspond to original diamond particles. The carbon onions with fewer defects, which have been obtained from smaller diamond particles, have shown lower friction and wear-resistant properties in both air and vacuum. These superior tribological properties have been exhibited in humid ambient on smooth surface of which roughness is less than the particle size of carbon onions.
The Precession Motion Ball Reducer is introduced and analyzed which has been newly developed. The element of the reducer consists of four coaxial components; an inclined input shaft, a fixed ring, a precession motion rotor with the freely rotating balls, and an output ring. These balls reduce a friction of meshing. And these are arranged in a uniform angular pitch. Also these are preloaded structurally to eliminate backlash The fixed ring has many looped grooves on inside of its surface. And the output ring has a spatial wave groove just like a "trochoidal-wave" on inside of its surface. Also these grooves conform to the loci of each ball attached on the precession motion rotor. This Precession Motion Ball Reducer is suitable for the positioning mechanism that needs a non-backlash characteristic. In this report, the motion principle is analyzed using polar complex vectors. It is proved that the position of each ball attached on the precession motion rotor is the important parameter to choose a reduction ratio and to generate a shape of groove.
In coordinate metrology, how to estimate the uncertainty of measurement in the specific measuring strategy is a key technique. The estimation method for uncertainties of measured parameters has been already proposed when the only random errors are put in the consideration. In this paper, the effects of systematic errors are theoretically analyzed to estimate the uncertainties in feature-based metrology. A circle feature with form deviations is measured by a coordinate measuring machine. When form deviations have autocorrelation function in position of measured points, the autocorrelation function influences the results of measurement as unknown systematic errors. The method to calculate the error matrix is statistically derived. Using this method, the uncertainties of the measured parameters can also be calculated dealing with autocorrelation function of the measured circle. The series of simulations for this method in statistical way directly implies that the concept and the basic data processing method in this paper are useful to the feature based metrology.
This study deals with the microstructure of TiC hard layer which is produced by electrical discharge machining with semi-sintered electrode. This technology were developed to improve the wear-proof of cutting tools, molds and dies mainly at the first. But, it was observed that the wear of cutting tools with TiC hard layer by EDM is more shorter than PVD or CVD coated tools under high-loaded cutting conditions. Therefore, there is some limitation to apply to cutting tools in full range. In this reports, some experiment is done to be cleared above mentioned problem by means of characterizing the microstructure of TiC by EDM. The main result of experiments are as follows; (1) The microstructure of hard layer made with semi-sintered electrode exhibits extremely amorphous character-istics with lattice constant a=4.3062Å, (2) Comparing with molecule ratio 1:1 of TiC, piled TiC atomic composition shows Tic 0.45. Carbon composition is extremely reduced. Therefore, It is thought that TiC is deposited on the substrate breaking down atomic distribution of electrode. (3) Above mentioned microstructure and grain morphologies were caused by ultra high cooling velocity in discharged crater on substrate. (4) As compared with the TiN coated carbide square end mill tool, EDC tool does not result in a precise coated layer like a CVD or a PVD coated layer, which tends to be relatively shorten in tool life.
Critical motion error sources of rotary axes with respect to linear axes in 5-axis machining center (MC) include: 1) the alignment error of rotary axes, and 2) the angular error due to e.g. the inclination of rotary axes. Each motion error has a particular "sensitive" direction where it causes the largest motion error in DBB measurement plane. In this paper, the diagnosis method for the motion error sources of rotary axes is proposed as: the first is to find out such the sensitive direction of each motion error source by using numerical simulation, and the second is to determine the diagnosis procedure according to the simulation results. Moreover, the applicability and effectiveness of the proposed diagnosis method is validated by this experiment.
This paper deals with experimental investigation on the generation of damping capacity of structures packed with balls. The relation between the vibration damping capacity and the noise damping capacity of the structures is examined. In the structures closely packed with balls, a linear relationship is not recognized within the vibration damping capacity and the noise damping capacity. The excitation packing is necessary for the close packing. However, this process is troublesome. Also, in the optimum packing ratio where the maximum damping capacity is obtained, the excitation packing is also inevitable. On the contrary, at 50% packing ratio, this excitation packing process is not necessary, and a linear relationship is seen between the vibration damping capacity and the noise. Therefore, the effect of magnitude of impulse, specific gravity, friction coefficient and repulsion coefficient of packed balls on the damping capacity is investigated at 50% packing ratio. Moreover, the generation mechanism of damping capacity is discussed by observing the behavior of balls in the cavity during vibration.
In single discharge machining of a 0.1mm tungsten electrode with discharge current of between 30 to 50A and pulse duration of several hundreds microseconds, a needle of 20 to 35μm in diameter has been produced instantaneously. In the 1st report, we studied the effect of the discharge conditions on the shape of the formed electrode's tip. However, the forming mechanism could not be understood clearly from several experiments in the 1st report. To understand this phenomenon, a stroboscopic imaging system with a Q-switched Nd:YAG laser is used to observe the dynamical change of the electrode during and after the discharge pulse. Formation of the needle-shaped electrode occurs after a single discharge in an interval of 100 to 300μs. Therefore, the electrostatic or electromagnetic force may not be considered to have an effect on the thin electrode formation phenomenon. Air currents are suggested as one possible contributor to the formation mechanism and its effect on wear length for positive and negative electrode polarities is discussed.
The trial manufacture of the ultra-thin SOI (Silicon on Insulator) wafer has already been carried out by numerically controlled plasma CVM (Chemical Vaporization Machining). In this paper, it is evaluated whether the wafer machined by plasma CVM can use as a substrate for a semiconductor integrated circuit. Though metal contamination and some particles are brought in the machining, it has been confirmed that they are removed by usual wet cleaning after the machining. The characteristic of the MOS diode formed on the machined wafer and the reference wafer is evaluated, and it is shown that both characteristics are equivalent. Furthermore, the ID-VG characteristic of the MOSFET formed on the machined SOI wafer and the reference SOI wafer is compared, and it is shown that both characteristics are also equivalent. That is to say, it has been concluded that the wafer machined by plasma CVM is usable as a substrate for a semiconductor integrated circuit.
A double nut preloaded ball screw changes a ball contact points from three to two while the motion direction change. The transient friction torque after motion direction change is less than that in the steady state and cause contouring error of circular interpolation. Oversize ball nut preloaded ball screw don't change the ball contact points, and for this reason, friction torque almost changeless at the motion direction change. As a result of using the oversize ball nut preloaded ball screw for a machine tool, the contouring error by the ball contact points change delete.
This paper deals with the method to minimize the total machining time of drilling multiple holes by determining the cutting condition considering both the cutting torque and the tool life. Based on the ACC(Adaptive Control Constraint) system that controls the cutting torque, the proposed method controls the tool life by determining the cutting conditions according to the "machining control plan". Among several machining control plans, the plan that maintains tool wear progress rate is found to be effective through the simulation. The proposed method is installed to a CNC machine tool, and its performance is verified by cutting tests. The results show that the proposed method reduces the cutting time by 7-13% compared to the conventional control methods.
The material properties of thin films (C 60, CN and TiN) are studied using a homebuit surface force apparatus (SFA). Elastic modulus and surface energy of these films are derived from the load-contact area relationship, based on the continuum elastic theory. The elastic modulus and surface energy of C 60 thin films 3-50 nm in thickness almost remain constancy and are estimated to be 9.0±3 GPa and 40 mN/m, respectively, which is in agreement with those of C 60 thick films. The method proposed in this paper is applicable for an ultrathin film 3 nm in thickness, although the conventional method such as a nanoindentor are not possible. Furthermore, the elastic modulus (surface energy) of a CN film 36 nm in thickness and a TiN film 46 nm in thickness are estimated to be 82±10 GPa(34 mN/m) and 104±10 GPa (13 mN/m), respectively.