In accordance with this study, the following conclusion has been obtained by introducing the SN technique into evaluation of the abrasive grinding of magnetic disk substrate and examining the reasonability to use characteristics value for determining an optimum machining condition. (1) It is found that evaluation of an optimum machining condition according to the minimizing characteristics, aiming characteristic and maximizing characteristic is controlled by the confidence limit and error to the confirmation test islconsiderably small where the evaluation is applicable as an evaluation characterisitc value.(2)The optimum machining condition determined by the evaluation characteristic value gives the result enabling to explain and examine well the phenomena caused by the conditional changes of respective control factors. (3) By means of the evaluation characterisitc value proposed, the scale of action effect of each factor is converted to a value, which can be judged quantitatively.
Precision machining achieves high levels of accuracy through the use of a highly accurate spindle and feed mechanisms, a highly rigid base and a single-point diamond tool. Researches are under way aimed at achieving even higher leveles of accuracy by adding computers, interferometers or encoders for practical control. In this report a control system (Workpiece- Refered Form Accuracy Control) is proposed in which the control is based on the workpiece, instead of the conventional approach which achieves high accuracy by increasing that of each mechanical element. This system performs in-process measurement of the workpiece and uses that information to execute direct control over the machining.
In this closed-loop position control system, the mechanism's oscillatory characteristics were considered in the design of the control loop. Using the usual P and PI modes for position and velocity controls, the oscillations become unstable as the control gain was set larger. For (P, I-P) controls, on the other hand, those characteristics become more stable as the gain increased. For this reason, the latter can be set at higher gain for faster response. For this oscillatory mechanism having a 40 Hz natural frequency and a 0.15 damping ratio, the maximum gains were 147 s-1 using (P, I-P) and 62 s-1 in (P, PI). A stable response was obtained in (P, I-P) at a gain of 60 s-1 but severe oscillations were observed in (P, PI) at the same gain. An experiment using an X-Y table resulted in seven-times higher gain using (P, I-P) over (P, PI), and ±0.2μ m contouring error using (P, I-P) as opposed to from +3.0 to-0.5μm using (P, PI) for 10 mm-radius-circle generations at a speed of 100mm/min.
An economical method to manufacture aerostatic journal and thrust bearings has been established. The spindle or master spindle is used as a mold, and the epoxybased resin is poured into the clearances between the mold and the housing to reproduce the shape of the mold. Thus, comparatively accurate bearing surfaces can be obtained easily. After the resin is hardened, air feed holes are drilled. This method is applied to manufacture bearings of wheel-support and work-support systems of a small cylindrical grinding machine in order to verify the performances in practical use. Radial maximum stiffness and load capacity of the wheel spindle journal bearing, for example, are 54N/μm and 250N respectively. The wheel spindle radial motion error is 0.1-0.2μm.
In this report a simplified design method of bolted joints against fatigue is described and it is discussed from a practical viewpoint. Two type of bolted joints are treated ; one is the simplest cylindrical joint, and the other is more practical T-flange joint. The relation between the load applied to the above mentioned joints and the stress in the bolts are calculated by using spring-beam model. A diagram is proposed in which the fatigue limit (Haigh) diagram is superposed on the relation between the appied load and the axial stress in the bolt of the joint. The fatigue failure of the bolt can be estimated by comparing the stress in the bolt to the fatigue strength of the bolt in the above diagram. The estimated values of fatigue strength show good agreement with the experimental results which have been published.
In terms of measuring the fall-off fragments of the built-up edges on the finished surface during orthogonal cutting, it is shown to be capable of estimating the turning surface roughness. The distributions of the over cuts by the built-up edges on the orthogonal cutting consist with the Weibull distribution, and provide information on the mechanism of the formation process of the finished surface during three dimensional cutting. The actual depth of cut is varied by the position at the turning tool edge, therefore, the results indicate that maximum height (Rmax) of surface roughnesses on the turning are assessed from integration of over cuts on the orthogonal cutting.
The thermal deformation of a workpiece during grinding is one of the most important factors that affect a flatness of a ground surface. This paper represents an approximate analysis method of the thermal deformation during one-pass surface grinding. In the analysis a simple model of the stress distribution, based on the results of a finite element calculation, is applied. The analyzed results are compared with profiles of ground surfaces. The main results obtained are as follows: (1) The tangential thermal expansion of a workpiece surface causes a bending moment on the workpiece. (2) The bending moment causes a convex deformation of the workpiece and it leads to a concave profile of the ground surface. (3) The shape of the ground surface has a good agreement with the analyzed deformation of a workpiece.
In this study, an experimental apparatus designed to test abrasive wear by mean of an abrasive belt was used to rub between virgin surfaces. The effects of contact load, the rubbing direction and amplitude of vibration on wear characteristics were examined in a series of the experiments. Results obtained are as follows. (1) The wear volume of CFRP becomes larger in the order, L, T, N. (2) The wear volume in both the X- and Y-directions decreases corresponding to the amount of over lapping. (3) In the Y-direction, wear volume is influenced by the rubbing direction.
In this paper, the characteristics of the tightening force reduction and of the wheel displacement with time by its force reduction are examined in detail. And those mechanism are made clear and the way of high precision holding of the grinding wheel over a long period of time is discussed. The following points should be taken into account to hold the grinding wheel very precisely. (1) to make the surface roughness of the holding surface of the grinding wheel smaller. (2) to use the packing materials which are easier to creep such as polyethylene in tightening. (3) to well-balance the stiffness of the fixed and loose flange to cause the same creep strain at the holding surface of the both after tightening.
This paper deals with the electron beam drilling of alumina green sheet. The following results were obtained through some experiments by multi-pulse drilling under various duty factors and a thermal calculation. (1) The number of beam pulse does not affect the diameter and taper of drilled hole. Furthermore, hole taper is kept constant for various value of workpiece thickness when drilling are performed in same conditions. (2) Hole diameter and taper increase dramatically at high duty factor even though drilling conditions are kept constant. (3) Material removal in the drilling of green sheet is taken place through scattering of surrounding material by explosive vaporization of organic binding material in the green sheet. (4) The increase in hole diameter and taper is due to the focal movement taken place through the space charge neutralization by positive ions generated by the ionization of vaporized gas.
For the purpose of developing precision polishing method of diamond stylus for video disc player (CED type), cutting technology of precise spiral groove on polishing plate is discussed experimentally in this paper. The groove cutting experiment is carried out using diamond cutting tools which have cutting edges with 30°, 90° or 140° included angle. The burr is generated on both corners of cut groove. The height and width of the burr are affected by the included angle of the cutting tool, cutting depth and crystal grains orientation of workpiece. For example, the burr height is 2-3 μm when the groove is cut using a diamond cutting tool having 30° included angle with 8 μm cutting depth, but, no burr is generated using the diamond cutting tool which has 140° included angle. This burr can be removed completely using a diamond cutting tool for mirror-finishing after groove cutting. This deburring method is very available to obtain desirable polishing plate for the diamond stylus. Furthermore, a diamond cutting tool wihch has 15° included angle is developed to improve the diamond stylus geometry.
Need for the controllable finishing of materials such as semiconductors and ceramics, has remarkably increased in the fields of electronics and precision machinary. A new lapping method has been developed by utilizing functional magnetic fluid which has the ability to move in the magnetic field. The magnetic fluid is a suspension of fine magnetite Fe3O4(smaller than 150Å) in liquid. This lapping method is based on the floatation of nonmagnetic grains suspended into the magnetic fluid in the magnetic field. Lapping experiments were conducted on soda lime glass. It was found from the experiments that the new lapping method is able to control the stock removal rate through varying the current to the electromagnet. The present method may be usefully employed in finishing such parts as aspherical lenses.
The present paper deals with the influence of the different type of chip breaker on the cutting force and chip controllability. A tool dynamometer which can measure separately the cutting force acted on the major cutting edge and the chip breaker is designed and constructed. The experiments in orthogonal and oblique cutting are carried out. The results obtained are as follows. (1) In orthogonal cutting, the decrease of the breaker width and the increase of wedge angle in the obstruction-type are improved the cutting mechanism by the decrease of the tool-chip contact length. In the groove-type, the decrease of the land width shows a similar tendency to the former, but the cutting forces are fairly different from the former because of the rake face controlled. (2) The chip curl radius is more fairly in accord with the change which appeared in the coefficient of friction on the major cutting edge than that on the chip breaker. (3) In oblique cutting, the effective rake angle and the chip width are increased according to the increase of the inclination angle. Under the influence of these factors, the region which minimizes the forces on the chip breaker is present.
Grinding experiments on structural ceramics have been carried out with various diamond grinding wheels. It is found that there exist microcrack layers in the ground surface. Below the microcrack layers, voids are formed. The thicknesses of both microcrack and void layers increase with an increase of the grain size of wheel, and become smaller by turns of HP-Si3N4, HP-Al2O3, SC-ZrO2 and NS-SiC. Voids are denser near surface than away from surface.
The circular cutting with a single point diamond cutting edge, in which the depth of cut is very small and takes maximum at some point, is carried out for making clear a cutting process of partially stabilized zirconia under conditions similar to practical grinding, investigating sliding phenomenon of a diamond cutting edge, normal cutting force, groove profile, stock removal and so on. Main conclusions obtained in this study are as follows : (1) There are three different regions with depth of cut ; elastic, plastic and cutting region. (2) There are critical depths and critical normal forces at the beginning point of plastic deformation and cutting. (3) In the transitional cutting process, there are following three types of interference with maximum depth of cut ; (i) elastic region through the contact length, (ii) elastic-plastic-elastic, (iii) elastic-plastic-cutting-plastic-elastic. (4) Surface generation of a groove is performed by plastic deformation as well as brittle fracture.
This paper describes the part which forms exit burr at the end of ground surface. In order to clarify the burr formation process, the deformation of corner shape at the exit end is observed. The effect of plastic flow in the ground layer and the residual stock removal are investigated. The results obtained are as follows : (1) In the vicinity of the workpiece edge, the plastic flow in the ground layer is expanded at an angle of 20-25° with respect to the grinding direction regardless of the edge angle of the workpiece. (2) The burr root is formed by the plastic flow part below the depth of cut. The burr is mainly formed by the residual stock removal at the workpiece edge. (3) In the growing up process of exit burr, the part width of about 30μm at workpiece edge (i.e. residual stock removal) turns to burr. corner shape, grinding burr, residual stock removal, plastic flow, edge angle
This paper describes a systematic method which can generate effective robot motion for handling constrained objects automatically. In this study, constraints which appear in the time of object manipulation are divided into following three parts. The first one is a natural constraint which is observed between an object and a base on which the object is constrained. Most of the natural constraints of industrial products are considered as a kinematic pair and this fact makes costraint problem simple. The second one is an artificial constraint which exists between an object and an end-effector whenever the object is handled. In this study, every artificial constraint is reduced to primitive relation between two fundamental surfaces. The last one is a configurational constraint which corresponds to a capability of robot. With evaluating these constraints, effective positions and orientations of the end-effector which can perform the specified task are calculated and robot motion to deal with a constrained object can be generated appropriately.
This paper describes a general method of detecting collisions among 3-D objects in the simulation world. It has been well recognized that geometric simulation using 3-D geometric models plays an important role in the preparatory phases of manufacturing. Collision detection is one of the important technologies, and several methods have been proposed based on the ideas, such as multiple static checking, swept volumes and intersection calculation. Since the computational cost for solving this problem is large in general, some consideration has been given to the shape complexity in the conventional methods. However, in addition to the shape complexity, the complexity of the trajectory also influences the computational cost. In this paper, therefore, we propose a new algorithm considering the trajectories of the moving objects. We have introduced the conditions which can indicate whether any collisions may occur or not at a tracjectory. If any collisions may occur, the trajectory is divided into two parts and both of them are checked in the same way. This process is recursively continued until a collision is detected or the whole trajectory is checked to have no collision. The average computational cost of this algorithm is estimated to be less than that of the conventional methods.