The purpose of this study is to build a database, named an engineering history base, which stores histories of engineering cases. Attentions are paid to a distinction between two types of knowledge used during engineering processes ; product knowledge and process knowledge. The product knowledge represents products, e.g. drawings, while the process knowledge represents information how to make and how to use the product knowledge including design intent. One of the most important requirements for the engineering history base is to access the data conveniently, taking account into the nature of the histories. For this, a methodology which uses constraints to describe process is proposed. To use constraints facilitates connections among process data and explanations. A prototype system has been developed to show the validity of the proposed methodology.
In high-speed sampling, a digital control algorithm in terms of the shift operator Z easily becomes numerically illconditioned. In such situations, a control algorithm in terms of the delta operator δ is useful. However, when the delta operator δ is applied to a control algorithm based on fixed-point arithmetic, there appear coefficient-quantization errors and product-quantization errors. As a result, a control algorithm becomes numerically illconditioned again. To solve this problem, the modified delta operator δ' is proposed, which is defined as subtracting one from the shift operator Z. This definition can make an easy transformation from the shift form to the delta form. Then, its applicability to a control algorithm is proved and its physical meaning is considered. Also, it is shown that sensitivity function approaches one, as the sampling period T approaches zero. And the number of multiplications becomes about two-thirds of that of a usual delta operation. Simulations show that the modified delta form can decrease the numerical errors in fixed-point arithmetic, in particular, with short word length. Thus, the modified delta operator δ' can be applied to a control algorithm just like the usual delta operator.
For the purpose of fabricating free-form optical elements to an accuracy of 80 nmPV, the CSSP (Canon Super-Smooth Polisher) has been developed. This device fmishes workpieces by alternately repeating contour measuring and corrective polishing. The tactics of corrective polishing are based on the tool's dwell-time control. In such a system, total processing time closely depends on the performance of a dwell-time calculation called deconvolution. A new deconvolution algorithm has been proposed, by which less residual error and shorter calculation time than the conventional algorithm, based on a simulation of polishing, is possible. This method is based on an analysis of spatial frequency domain. Therefore, by using an FFT (Fast Fourier Transformation) it can greatly reduce the calculation time. In this case, however, it tends to give unstable dwell-times because the unit removal function has limited frequency response. To address this difficulty, two methods have been devised. The first one is based on a low-pass filter technique, and the second is based on optimizing a functional. By comparing these methods to the simulation method, their performances are checked in the fields of residual error, predicted processing time and calculation time. An areal calculation shows that the new method can achieve a 1/4.3 smaller residual error, a 4 % longer but much smoother dwell-time distribution, and 1/45 shorter calculation time.
The demand of liquid crystal display panels for handy type personal computers etc. have been remarkably increased. Liquid crystal display panels were generally formed on glass substrates. In these production process, precise arid fine cutting of glass plates is very important because of the final manufacturing process. Hard and brittle materials like glass plates are conventionally cut by growing vertical cracks. They are generated by scribing with a diamond point or a rotating chisel under optimum load and grown by applying mechanical force onto the scribed trace successively. In the laser braking method, vertical cracks formed on glass plates are grown by tensile stress due to thermal expansion which arises from temperature rise by a CO2 laser beam irradiation onto the scribed trace. High quality and high speed breaking can be achieved without applying mechanical force. In this breaking process, formation of fine vertical cracks by scribing is indispensable. This paper deals with the effect of scribing conditions on features of scribed trace and the vertical crack length experimentally and theoretically. Generation and growing process of vertical cracks were observed. Close agreement of vertical cracks length grown between observed and calculated values was obtained.
Influence of the grain size of diamond stone on the superfinishing performances is investigated experimentally. The mechanism of chip formation is investigated by observing the shape of chips and the finished surfaces of workpiece with scanning electron microscope. The work materials used are alumina (Al2O3), silicon carbide (SiC), silicon nitride (Si3N4) and zirconia (ZrO2), which are sintered under the atmospheric pressure, and Mn-Zn ferrite, which is sintered under HIP. The grain size of stone is changed from # 500 to # 8 000. The results are as follows. The diamond stone with suitable bonding strength makes it possible to remove the work material as chips even if its grain size is finer than # 1 000. Two types of chips are obserbed; one is the crack-type chips which are made by brittle fracture, and the other is the flow-type chips which are made by plastic deformation. As the grain size of stone becomes smaller, the shape of chips changes from crack-type to flow-type. The critical grain size is dependent on the work materials and it becomes smaller in the order of ZrO2, Mn-Zn ferrite, Al2O3, Si3N4 and SiC. The condition of making the flow-type chips is important to obtain the mirror surface of ceramics.
This paper deals with the tuning method of mechanical parameters of the single axis feed drive system in NC machine tools. In this method, tuning map is proposed to support the designers to know what level of the total servo performance is achieved and how to modify the mechanical parameters to fulfill the design targets. In the case study, tuning of the ballscrew design parameters and selection of the servo motor are demonstrated on the machine tools for flexible transfer line and machining center.
Anisotropic etching process is expected as one of the micro-machining processes and some studies have been made with respect to its chemical reaction and finished accuracy, however, because of being affected by many complicated parameters associated with material, etchant, etc., its favorable condition so as to maximize both the finishing accuracy and etching efficiency is not yet established. The present paper has proposed a guideline for selecting this favorable etching conditions and summarized the result in a form of flowchart.
In a centerless grinding, a roundness error of ground workpiece depends on various parameters such as center height angle γ, blade angle φ, rotational speed of workpiece nω and stock removal rate Z'. This paper investigates the influence of these parameters through a computer simulation method to optimize grinding conditions for a minimum roundness error. Centerless infeed grinding tests were conducted and the results were compared to those of the simulation. Conclusions are as follows: (1) The new computer simulation method, which is combined with the geometrical and grinding conditions, is proposed, and the results agreed with actual grinding results. (2) Roundness can be improved by adjusting nω. (3) Optimum grinding conditions can be expressed by a pair of parameters (γ, κ). As the results of simulation and grinding tests, the values of (γ, κ) were about (6°, 0.45).
The purpose of this study is to develop a new method in order to improve efficiency and accuracy on cutting using OD-blade for hard and brittle materials, such as various ceramics, single-crystal silicon, etc. This new method is the cutting technique applying mechanical vibration. In this paper, the findings of this investigation on the vibration cutting applying low frequency vibration for a workpiece at parallel direction to the cutting, are reported. The main results obtained are as follows. When the vibration velocity amplitude is larger than the cutting speed (feed speed of the workpiece), grinding force in the vibration cutting is less than the one in the conventional cutting. The tool life in the vibration cutting is improved to compare with the conventional method, and further processing accuracy is improved. With this study, it is proved that this vibration cutting has the possibility of effective cutting method using OD-blade.
This paper investigates the removal mechanism of high electric resistance materials in EDM processing by calculation of the distribution of the workpiece temperature taking the Joule heating caused by voltage drop in the workpiece into account. The voltage drop in the workpiece is extensive in the EDM processing of high electric resistance materials such as conductive ceramics. The voltage drop was therefore estimated by a numerical calculation, and its results were used to calculate the distribution of Joule heating inside the workpiece. Then considering both the Joule heating and the heat flux from the arc column, the time dependent workpiece temperature was computed by the finite-difference method. The expansion of arc column with time lapse which affects greatly the result of the above calculation was obtained experimentally and taken into account in the calculation. The calculated results show that the voltage drop mostly occurs in the vicinity of the discharge spot, and the calculated total voltage drop coincides well with the measured one. From the computed temperature distribution it is found that the Joule heating causes a temperature rise nearby the discharge spot which is comparable to what is given by the heat flux from the arc column, which was confirmed by the measured material removal by a single pulse which is greater than the removal of steel. Consequently, sufficient cooling of the discharge spot may assure the stability of machining and increase the material removal rate of conductive ceramics rather than metallic materials.
In order to fabricate ultra-precision diamond tools and delineate ultra-fine patterns into diamond chips without adding a radiation damage, etching characteristics of diamond chips with electron beam assisted chemical etching (EBACE) has been investigated. EBACE system is composed of a scanning electron microscope (SEM) which has an oxygen introduction system was used to etch synthetic single crystal diamond chips. When electron beam was focused on diamond surface, very small holes with a diameter of about 0.5-2 μ m, and a depth of about 0.01-0.5 μ m were obtained. Line and rectangular patterns with several μ m and sub-μ m depths were also obtained.
This paper presents a new high speed and high precision NC-lathe for machining a piston-head of a reciprocating engine. In the machining of a piston-head, a cutting tool positioning servomechanism is needed, because the machining of a piston-head is the non-circular machining, in which the stroke of the cutting tool positioning is 0.1-0.5 mm. Previously a new servomechanism actuated by electromagnetic attractive force was developed as a cutting tool positioning mechanism. But a prototype of this servomechanism did not make a high speed non-circular machining possible, as the response performance was not at a satisfactory level. Thus, to enhance the response performance, the prototype has been redesigned with the use of some plate springs, the decrease in mass, the restraint of eddy-current loss and so on. Also the periodic learning control method with the inverse transfer function compensation has been applied to the positioning control for the high accurate positioning. These modifications lead the developed NC-lathe for a piston-head to the achievement of practical machining with an accuracy of 2 μm at 3000 min-1.
In this paper, the cutting performance and the wear characteristics of ceramic tools such as Al2O3, Al2O3+ZrO2, Al2O3+ TiC and Si3N4 are presented when turning three-phase sintered carbons containing nongraphitized materials and are compared with these of the cemented carbide tool K 10. Further, since the wear of alumina ceramics is influenced by surrounding moisture, cutting tests are carried out on the sintered carbons containing water. The wear rate of alumina ceramic tools is slower for carbon phase (1500°C) than for graphite phase (2500°C). This behaviour is different from that of K 10 and Si3N4. In particular, the wear pattern consists of two areas of wear and carbon adhesion in the cutting of carbon phase. The same behaviours are also observed when turning two-phase sintered carbon. A tendency of wear rate corresponds to that of coefficient of friction in rubbing tests.