This paper investigates the wear mechanism of a vitrified bonded CBN wheel in grinding mild steel (SS400). Wheel wear after grinding mild steel is extremely large compared to cast iron (FC200), hardened steel (S45C) or high-speed steel (SKH57), even though the grinding force is small. It became clear that the wheel wear increases under the condition of longer arc contact. Furthermore, a single grain cutting test reveals that the actual chip length of SS400 almost doubles compared to the SKH57 or FC200 chip, and that the chips are very brittle. Therefore it seems that the chips do not erode the bond material directly. Through SEM observations of the wheel and workpiece surfaces before and after grinding, it was found that SS400 chips are easily loaded into the chip pockets on the wheel surface, and there are many deposited chips and embedded CBN grits on the ground surface. These phenomena, therefore, indicate the possibility of the consecutive fracture of CBN grits, and lead to the severe wear of CBN wheel.
The present paper presents a new cutting method named “Elliptical Vibration Cutting”. Synchronized twodirectional vibration is applied to the cutting edge in the plane including the cutting direction and the chip flow direction. The chip formed is mainly pulled out by the tool while the tool moves in the chip flow direction, and then the tool is restored to the cutting point without cutting in each cycle of the vibration. Orthogonal cutting experiments of copper are carried out within a scanning electron microscope, and it is confirmed that chip thickness, cutting force and cutting energy are reduced remarkably by applying the method proposed. Generation of burr is restrained, and quality of finished surface is also improved.
The requirement of producing metallic micro-parts for micro-machine and/or micro-mechanism will be increased. The study deals with manufacturing of tiny parts in mm-size by use of micro-machining technique of an ultra-precision milling machine. The ultra-precision milling machine, consisting of Z-motion table, positional spindle on it as C-rotational axis, X-motion table, is equipped with a pseudo-ballend mill composed of a single crystal diamond tool mounted at the top of high speed air spindle on X-motion table. A new manufacturing procedure is devised to manufacture a propeller of 3 mm in diameter as an example of micro-parts by use of ultra-precision milling machine. On the basis of CAD data of a propeller, two kinds of NC data, for front face and back one, are generated to machine the whole shape together with preparation of jig. It is found that the machined propeller mounted to the micro motor shaft works.
A new approach is proposed in order to clarify theoretically the stability of a regenerative chatter vibration in end mill operation. In this analysis, the dynamic cutting force due to the penetrating velocity of a cutter is considered in addition to the cutting force proportional to the uncut chip thickness. Furthermore, an unstable region to the chatter vibration is examined on a surface generated by one cutting. The results obtained are as follows. The chatter vibration occurs easily in the region where the instantaneous depth of cut is small. A low cutting speed and a high helix angle of the cutting edge increases the chatter stability. On the contrary, width of cut and depth of cut does not affect the chatter stability in usual cutting condition. The increasing of stiffness, natural frequency and damping ratio of the end mill is effective for preventing the chatter vibration. The chatter stability in down milling is lower than that in up milling.
A clear understanding of the energy distribution in the EDM process is very important for the explanation of some phenomena which cannot be explained well up to now. In this paper, methods and results of measuring the energies distributed into the tool electrode, workpiece and dielectric in the continuous EDM-sinking process are described. The energies distributed into the tool electrode and workpiece are obtained by means of measuring the temperatures and removal amounts of the electrode and workpiece, and the energy distributed into dielectric fluid is obtained by measuring the temperature rise of the dielectric fluid after flowing through the discharge gap. It is found from the experimental results that the energy distributed into the tool electrode is greater than that into the workpiece independently of the pulse duration and that the energy distributed the dielectric is quite small compared with the energies into the electrodes and the workpiece.
For monitoring tool wear state of three dimensional turning process under various cutting conditions, a active monitoring method-diagnostic impulse excitation method-was proposed. It was clearly shown that the dynamic characteristics of the impact response of tool vibration, especially, the damping ratio was closely related with flank wear development. In order to separate the damping ratio only concerned on the wear from total damping ratio, the ratio of wear free tool was obtained experimentally and formulated under various cutting conditions and various tool edge geometry. The ratio of wear free tool was shown to be linearly increased with the contact edge length with workpiece, and also with the feed force. The ratio concerned with flank wear may be separately measured using the results of wear free tool. The energy consumption concerned on wear land may be easily obtained using the measured damping ratio under various cutting conditions for various tool geometry with flank wear land. The energy consumption mechanism on flank wear land for various tool geometry and under various cutting conditions was discussed. The consumption was quantitatively obtained, which is caused by interaction between a flank wear land and a machined surface. Through the discussions the relation between the measured damping ratio and the flank wear area was shown. The theoretical relation can give the flank wear development for various tool geometry under various cutting conditions based on only the damping ratio measured.
Chip formation process is analyzed by implicit-type elastic-plastic FEM (Finite Element Method). The implicit formulation of radial return method for elastic-plastic constitutive equation is described comparing with conventional explicit formulation. The implicit-type elastic-plastic FEM is effective for cutting simulation because it can treat the difficult problems of elastic-plastic analysis such as stress equilibrium, consistency condition of plastic element, unloading process easily. The simulation results of carbon steel (S 45 C) cutting including chip shape and principal cutting force are compared with experimental results, and they are in good agreement. The chip curl process is also simulated by considering no-friction condition. In this simulation, chip curl radius decreases as the tool rake angle increases. It is conducted that implicit-type elastic-plastic FEM is useful for cutting simulation.
In this paper, a new grinding technique, the thermal deformation rate control grinding, in which the thermal deformation rate of workpiece is controlled by changing the fluid flow rate at the beginning of spark-out state, is proposed in order to improve remarkably the surface roughness of workpiece. Main conclusions obtained as follows : (1) From a viewpoint of the surface roughness improvement, the most suitable fluid flow rate exists in spark-out state. For example, the surface roughness of workpiece can be improved 32 % at the point of 10 s spark-out time when the fluid flow rate is changed from 15L/min to 3L/min comparing with the constant fluid flow rate 15 L /min. (2) The surface roughness improvement'process in the thermal deformation control grinding is made clear by considering the relationship between the actual size generation rate and the surface roughness rate of workpiece. (3) An in-process measurement method by which the thermal deformation of workpiece can be estimate, is developed to make clear the surface roughness improvement process.
Chip breaking processes of the grooved rake face tools are simulated to predict the chip breakability and forces change at the chip breaker edge in detail. This simulation is focused on the deformed chip and is carried out by elastic plastic finite element method with non-steady state heat conduction analysis. The initial model is made using the results of the steady state metal cutting analysis by thermo-elastic plastic finite element method with iterative convergence method. It is assumed that cracks develop on the chip surface when the maximum principal stress criterion or the maximum shear stress criterion are satisfied. These cracks propagate in the direction of the minimum principal stress for the former case or in the direction of the maximum shear rate for the latter case. The crack propagation is considered as node separation. The broken chip shapes simulated are in good agreement with those experimentally obtained. There is very good correlation between the simulated and measured cutting force changes. It is found that the breakability can be changed dramatically by rather changing the tool geometry than changing the other cutting conditions.
This paper deals with the analysis of axial loads in the tie rods to clarify the relationship between the axial loads and the ordinal number of the nuts of built-up columns which are applied the fastening torque. First of all, an experimental analysis of the change of axial loads is performed while fifteen cylindric parts of the built-up columns of spiral staircase are assembled. Next, a numerical analysis of axial loads in the first tie rod is made by the finite element method. The results are summarized as follows. (1) As the ordinal number of the nuts increases, the values of axial loads in the tie rods become higher, and as a result, the first tie rod gets the maximum load. (2) The value of axial load in the first tie rod becomes higher as the set up value of fastening torque increases and the ordinal number of the nuts increases. (3) The calculated values of axial loads in the first tie rod mostly agree with the experimental values. (4) When a set up value of the fastening torque takes 107.9, 147.1 or 186.3 N·m, the values of additional axial loads in the first tie rod decrease at a constant rate as the ordinal number of the nuts increases. (5) The proposed method used in this paper can generally analyze the actual change of axial loads in the tie rods sufficiently and accurately for the practical usage.
The point-in-polygon test is one of the most fundamental geometric tests and appears very frequently in computer graphics and geometric modeling. The algorithms based on parity counting for this test, are widely being used and have been discussed in many papers. However, geometric and numerical problems still remain in many of those algorithms. In this paper, a new algorithm based on parity counting is presented for the point-in-polygon test, By using a sign correction technique and exact integer arithmetic, both geometric and numerical problems have been improved. Finally, the efficiency of the algorithm is discussed. All of the processing in the algorithm is based on the 4 × 4 determinant method.
This paper deals with a method for presenting reaction forces in virtual assembly environments, which is used for instructing or training techniques of assembly works. There is an important demand for the reaction force on stress of parts in the virtual assembly environment. In this paper, the C-Space (Configuration Space) representation and the hierarchical processing are proposed for satisfying the demand. The C-Space can represent all stress relations of parts clearly, and can indicate the current location immediately by making the space divided into some zones of geometrically important states for works. The hierarchical processing is realized with two-levels layer and reduces the calculation delay for controlling the reaction force. The qualitative level processing recognizes a task by kinematic reasoning with the C-Space, and the quantitative level processing calculates the reaction force by task based reaction models and physical data. A case study with two experiments shows that the method is effective for presenting reaction forces on a screw tightening work.
This paper is concerned with an application of optimal regulator to control for mechanical systems. The properties of limiting form is discussed in detail, which is derived by letting the weighting matrix of state vector tend to infinity in standard optimal regulator problem. In this study, the limiting form is derived under the general initial conditions. Then it is shown that the limiting form includes delta functions and its derivatives. Further, it is pointed out that the limiting form leads to the solution for the output zeroing problem. Control inputs are bounded in some initial conditions, although the feedback gain increases with the weighting matrix. This clarifies the reason why the linear regulator can be applied to the control for certain mechanical systems with a constraint. A simulation is carried out to evaluate the effectiveness of this control method.
When an inspection process compares a detected circuit pattern with a reference pattern to search for pattern defects, slight differences between the two patterns can cause false-alarms to be generated. Less mismatch between images is therefore desirable to achieve accurate automatic-defect detection. This paper presents a simple method for adjusting the shape of a reference pattern so that it more closely resembles the shape of an actual circuit pattern which has undergone deformation during the pattern manufacturing process. In this method, a virtual circle scans every pixel in a reference pattern and the center of the circle traces out a locus of the new pattern boundary provided that the area occupied by the pattern in the circle is constant. The method can round-off pattern corners in a flexible manner and can decrease a mismatch of up to 5 pixels to 1 pixel.
A new method has been developed to measure particle sizes of nanometer order on raw Si wafers by using a photomultiplier (PMT). The dynamic-range of a PMT used to detect extremely weak light is narrow generally. And moreover, as its rated current has a very low value, a protective circuit needs to guard the PMT against over-current due to unexpected very large particles. In this study, it was tried to derive theoretical formula for calculating the output current on the PMT quantitatively. By estimating the characteristics of the output current by the obtained formula, a method for protecting the PMT by using the saturation region at the characteristic of output current can be devised. As a result, it can be verified that this method could simplify the measuring method and the instruments, and it could magnify the dynamic range of the PMT in measuring extremely weak lights.
Recently 5-axis control NC machine tool have become a center of attraction in manufacturing of woody furniture. They are expected its high intricate machining performance beyond the capabilities of standard one, however, it has not been used widely yet. One of the most serious problem to prevent them from introducing the NC machine tool is the difficulty in generating NC data by using general postprocessor. This paper describes a post-processor which has a simple and easy user interface and can generate NC data for 5-axis control NC machine tool with tiltinghead in a short time. The post-processor is made up of two modules;the first one corrects the value of coordinates in CL data by considering only the tool length which is that from the center of swing to the top of tool; the other generates NC data (X, Y, Z, B, C) from the corrected CL data. By actual machining test it is shown to get the NC data from the normal CL data and run 5-axis control NC machine tool with tilting-head as the computer simulates the motions.