96767990
Improvement of form accuracy in hybrid machining of microstructures
Micromachining is gaining popularity due to recent advancements in Micro Electro Mechanical Systems. Using conventional micromachining, it is relatively difficult to produce moving components in the order of microns. In this study, an attempt is made to fabricate microstructures using a combination of turning and electrodischarge machining (EDM). Several sets of experiments have been performed to study the characteristics of the hybrid machining process. From the experiments, it has been observed that a higher form of accuracy could be obtained by integrating the on-machine fabrication of the tool and by subsequently using the same tool for EDM. The main cause of the form error is due to the deflection of the shaft during turning. Hence, an attempt is made to observe the deflection of the shaft using a deflection sensor. The influence of micro-EDM parameters such as feed rate, discharge circuits, and gap control parameters on material removal rate and tool wear is also discussed in this study.
109511221
Automated process planning for the manufacture of sliders
FCAPP for the manufacture of injection moulded components, which will facilitate the standardisation of process planning and significantly reduce lead-time. The main components of the mould such as the slider, the lifter and the mould base are considered in this system. In this paper, the automated process planning for the manufacture of a lifter is described. A combination of the generative and variant approach (hybrid approach) is used for the development of the system. The input to the system is a 3D lifter model. First, the system classifies the lifter types and extracts the feature parameters from the model. Each lifter type refers to a standard process plan template, in which a set of processes is presented in sequence. Secondly, the system selects the machines, cutters, fixtures, and cutting parameters for each process in the plan template, based on the actual dimensions of the features and constraints and rules defined in the system and the available machining resources. The process plan execution is then simulated on the screen step by step.
26262056
Molecular dynamics simulation of the effect of tool edge radius on cutting forces and cutting region in nanoscale ductile cutting of silicon
Unlike in conventional cutting processes, where the undeformed chip thickness is significant compared to the cutting tool edge radius, in nanoscale cutting processes, the undeformed chip thickness is very small, on the nanoscales. Therefore, the tool edge radius can not been ignored. It has been found that there is a brittle-ductile transition in cutting of brittle materials when the cutting tool edge radius is reduced to nanoscale and the undeformed chip thickness is smaller than the tool edge radius. In order to better understand the mechanism of the transition, a molecular dynamics (MD) method, which is different from continuous linear mechanics, is employed to model and simulate the nanoscale ductile mode cutting process of monocrystalline silicon wafer. The simulated variation of the cutting forces with the tool cutting edge radius is compared with the results of the cutting force from experimental cutting tests and they show a good agreement. In the simulated results, it can be seen that the thrust force is much larger than the cutting force in cutting. The simulated results also denote that the resultant force in the cutting process is not uniformly distributed along the cutting tool edge. In the simulation, the elastic springback of small thickness is observed on the machined workpiece surface.
28342459
Process planning optimization for the manufacture of injection moulds using a genetic algorithm
This paper reports a real application of a computer-aided process planning (CAPP) system, IMOLD_CAPP, for the manufacture of injection moulds. A combination of a template and a generative approach is used for the development of this CAPP system. The input to the system is the three-dimensional mould components developed by IMOLD. Here, the process-types and their sequences for a particular type of mould component are defined in the plan template based on company practice, while selection of machine tools, cutting tools, and cutting conditions for different processes in the plan template are optimized by a method based on genetic algorithms (GAs). The objective function of optimization is to minimize overall processing time. The performance of the optimization is compared with an algorithm based on simulated annealing (SA), and the GA-method is found to be appropriate for the optimization. This approach is expected to be applicable in most mould shops based on their available machining resources.
97577218
A study on the grinding of glass using electrolytic in-process dressing
Grinding of brittle materials such as glass is gaining importance due to the rapid developments in the areas of machining of storage devices, microlenses, and optical communication devices. Grinding of such glasses is difficult because grinding wheels wear out easily due to the hard and brittle nature of the materials being machined. Grinding wheels with fine abrasive size are required in order to achieve ductile mode grinding. Problems such as wheel loading and glazing can be encountered while grinding with fine abrasive wheels. Electrolytic in-process dressing (ELID) is an efficient method to dress the grinding wheel while performing grinding. In this paper, a fundamental study on the mechanism of the ELID grinding technique is discussed in detail. Several sets of experiments have been performed to determine the optimal grinding conditions. From the experiments, it has been established that surface roughness could be further improved if the current duty ratio to dress the grinding wheel were increased. The force patterns and the changes in the profile of the grinding wheel during machining are also presented and discussed in detail.
45952050
Fourier-transform solution to the problem of steady-state transonic motion of a line load across the surface of an elastic half-space (the corrected Cole-Huth solution)
Abstract Considered in the present article is the problem of a line load load moving at a constant transonic speed across the surface of an elastic half-space. Solution of the problem is derived here using the method of Fourier transforms.
135911643
Method of dry-etching evaluation using quantum dots
Abstract New dry-etch processes, such as low-power reactive-ion etching (RIE) and electron cyclotron resonance, offer very low levels of residual lattice damage. These levels are below the resolution limits of traditional characterisation methods like Raman, photoluminescence, Schottky diode, etc. We show that the single-electron charging of a quantum dot fabricated using dry etching offers a very sensitive method of damage detection. For SiCl 4 SiF 4 RIE of GaAs we find a defect density of around 1015 cm−3, which is at the level of the background impurity concentration in the as-grown material.
15039379
From DFT to systems test-a model based cost optimisation tool
Long lasting systems like airplanes have a cost structure where the maintenance costs are larger than the purchasing costs. Testing is required, both for preventive maintenance as well as repair and a major source for cost. Previously we have analysed test and Design for Testability for digital systems, covering ASICs, boards and systems. Besides, the continuous development of technology requires cost models that can grow dynamically and, because we will never have all information, can work with incomplete data sets. In this paper we present a tool that is well suited for a wide range of applications. Previously developed cost models can be incorporated and new elements can be added to the model as needed. Due to the generic approach the tool allows modelling general systems. It is not bound to the digital domain, although it has a strong background there.
62747469
An efficient numerical technique to calculate buffer statistics
Abstract A numerical solution is presented for obtaining the buffer statistics of a G / G /1 queue. The moment generating function G M ( z ) of the number of blocks buffered at the completion of a service is assumed to be known via the Pollaczek Khinchine formula. Only finite number of arrivals during a service time are allowed. To compute the buffer statistics, poles of the denominator polynomial of G M ( z ) and the residue at each pole are evaluated. The procedure is very efficient and stable; the computational complexity grows slowly as the order of the polynomial increases.
3714667
Stochastic approximations of perturbed Fredholm Volterra integro-differential equation arising in mathematical neurosciences
This paper extends the results of synaptically generated wave propagation through a network of connected excitatory neurons to a continuous model, defined by a Fredholm Volterra integro-differential equation (FVIDE), which includes memory effects of the past in the propagation. Stochastic approximation and numerical simulations are discussed.