جستجوی مقالات مرتبط با کلیدواژه "reverse engineering" در نشریات گروه "مکانیک"

The accuracy of the initial design of the gears can significantly ensure the proper function of the gearbox as a part of the transmission systems. This paper discusses the economic impact of performing a virtual process, which includes computer-aided design and rapid prototyping, on reverse engineering of a Honda CB-125R motorcycle gearbox to modify existing traditional trends and examines the reduction of production costs. For this purpose, the gears were disassembled from the motorcycle gearbox and examined in terms of dimensions. Then, calculations were performed to find the modulus of each pair of gears involved. After extracting the dimensional characteristics of the gears, a computer model of each was drawn, and then physical samples of them were produced layer by layer by fused deposition modeling method. To ensure the dimensional accuracy of the gears for mass production, the produced samples were used to test with assembly in the gearbox. After the approval of the initial design, the mass production of gears with the determined parameters was performed by the hobbing machine. The results of monitoring the application of the virtual process in reverse engineering of the studied gears in the five months of mass production prove that the virtual process reduces the costs of the production errors, assembly defects, and waste parts to 100%, 55%, 71% respectively. Hence, the virtual process reduces the total mass production costs by 36%.

One important problem investigated in reverse engineering (RE) field is finding the best surface to approximate point cloud data. Swept surface is a surface type that in addition to various applications in CAD/CAM software, satisfies the whole standards required for use in RE software. The most important problem in utilization of swept surfaces for RE purposes is the finding of the areas belonging to it out of point cloud data. Through an algorithm presented in this paper, a method has been introduced to find these areas automatically. Currently, this process is performed by user intervention. In this paper, using kinematic surface formulation and slippable motion concept, a general method to find swept surfaces with any arbitrary central curve and profile is introduced. To this end, point cloud data are processed regarding slippable motion criterion using iterative segmentation algorithm, then by presenting an effective algorithm and employing the concept of hierarchical classification and drawing the dual graph, swept-surface-related areas are found. The introduced method is implemented in several models with different conditions for validation. It is observed that the results have good agreement with real model condition, showing the efficiency of this method in finding the swept surface.

Point-based models have been analyzed for different applications and depending on the demand, features are extracted by various algorithms. Surfacerecognition from point clouds is most applicable problem in machine vision and reverse engineering. In this research for estimating design parameters, planes and cylinders in point clouds are investigated and new algorithm for detecting these surfaces and calculate their parameters is proposed. According to proposed method, at first surface normal vector by using nearest neighbors must be estimated. By using surface normal vector homogeneous neighborhood is selected. Umbrella curvature is then calculated using homogeneous neighbors. The points are grouping by umbrella curvature as a criterion. Planes and Cylinders are detected by analyzing umbrella curvature values and pattern of homogeneous neighbors. A new method for calculation of planes and cylinders parameters is proposed. This method used fordetermining parameters of eachgroup of points. For evaluation that the proposed algorithm, the calculated parameters are compared with parameters are measured by coordinate measuring machine (CMM). Analyzing results shows that the proposed algorithm performs well and has appropriate abilities on automatic detection of cylinders and planes and calculation their parameters.

In reverse engineering it may be required to perform multiple measurements due to the size and part complexity limitations of the physical equipment CMM / Optical Scanner and / or settings. To model the whole part it is required to bring different point sets obtained during different scans to a common coordinate system. Registration process for point clouds is to find the geometric transform between them in which all point clouds are transformed into a single absolute coordinate system. Theoretically، it is very straight forward to perform registration by finding the six components of transformation matrix (3 angles plus 3 displacements) and this can be mathematically determined if three non-linear points are known in both global and local coordinate systems. The process of registration is strongly affected by inaccurate data and may fail in the case of noisy data، hence other methods are usually sought to find the transformation matrix. This paper tries to solve the problem in practical applications. The Nelder-Mead method was employ for point clouds registration for the first time. The registration was also performed using Singular value decomposition and Genetic Algorithm methods. The three methods were compared in terms of convergence، accuracy and computation time.