Advanced Materials Research Vols. 139-141

Abstract: A workpiece will be subject to gravity and cutting forces during the machining operation. In order to resist external loads, multiple clamping forces are usually exerted on a workpiece so that it can be hold to be the correct position during the entire machining operation. However, insufficient clamping forces cannot prevent the workpiece from motions whereas excessive clamping forces may cause the improper deformations of workpiece-fixture system. Therefore, a systematic determination of magnitudes and placements of clamping forces is formulated as nonlinear constrained equations according to the minimum total complementary energy. By solving the resulting nonlinear equations, all contact forces including clamping forces and their application placements can accurately predicted in the frictional workpiece-fixture system. This method is illustrated with example cases.

Abstract: STEP-NC provides a way for intelligent NC manufacturing and seamless connection of the computer systems in design and manufacturing industries. It also makes it a must for a new breed of CNC machines to interface directly with the new part programs in STEP format (ISO 10303-21). In this paper, the data model and structure of part programs based on STEP-NC (STEP AP 238) are overviewed. Available tools are discussed and a method of extracting the manufacturing information from STEP-NC physical files is presented, and corresponding software module are developed in ST-DeveloperTM environment. With the aid of the STIXTM and ROSETM C++ library, the general information, feature information, technological information are extracted from the STEP-NC file and organized in a tree structure according to the hierarchy of the data model, which is essential to further usage of the manufacturing data, such as process planning, tool-path generating etc.

Abstract: The analysis for die forging forming problems with finite element method can lose considerable accuracy due to severely distortional meshes. The element-free Galerkin method is suitable for large deformation analysis and provides a higher rate of convergence than that of the conventional finite element methods. A rigid-plastic meshless method based on the element-free Galerkin method has been applied to die forging problems. The arc-tangent friction model is used to handle frictional contact and the penalty method is applied to impose the volumetric incompressibility conditions. By dividing all integration points set into the point subset of the rigid zones and the point subset of the plastic zones, nonsmoothness of the rigid-plastic constitutive relation can be eliminated. A die forging example has been analyzed to demonstrate the performance of the method.

Abstract: Metal machining simulation using finite element method (FEM) is extraordinarily complex. It is essential to develop a system so as to construct simulation model and obtain valuable results conveniently and rapidly. This study developed a parametric modeling based on MSC.Marc software, which included the key techniques of three-dimensional (3D) modeling and the parametric modeling course of metal milling process. In addition, an explanation facility based on the procedure file, which could be run automatically, was performed according to a modeling procedure. The interface of the system designed using Builder, could access data, which included the geometric angles and the dimensions of a tool and a workpiece, the relative position between them, their properties and cutting conditions, etc.. Calling the procedure file, the system approached the parametric modeling. An example was given, which simulation results indicated that it is an effective methodology to develop 3D parametric modeling.

Abstract: Aim at the communication problems of computer and NC machine tool, a practical DNC system is developed in this paper. A three-layer control structure mode – which is composed by the unit layer, DNC computer workstation layer and NC system equipment layer – is presented. Based on its good real-time capability and high reliability, CAN field-bus is introduced into the DNC communication system construction, the network topology is constructed and related hardware is chosen properly. Using VC++6.0 as development tool, and assisted with special compiling tools LEX&YACC, 3D standard graphic library OpenGL and database Microsoft Access, and based on the multi-task and multi-thread technologies, the software of the system is developed. The system has the characteristics of reliable operation, simple structure and high real-time capability, can improve the efficiency of NC machining process obviously, and has a certain application prospect in the middle and small scale manufacturing enterprises of our country.

Abstract: To provide the orientation information of gear-boxes in the machining center, an algorithm was studied. The gear-box part was built based on dozens of parameterized features according to KBE (Knowledge Based Engineering), and was assumed being surrounded by six planes which were Front, Back, Left, Right, Bottom and Top. The features based on KBE were applied to the six planes one by one through the Boolean operation. Each feature was set a direction vector parameter which showed the feature orientation in the global coordinate system. After each direction vector of the six planes was calculated out based on the selected three points on each plane, the features’ direction could be identified by comparing the two orientation vector parameters. The result is that CAM system can arrange the gear-box parts’ clamping position more conveniently after the features owned orientation planes are identified.

Abstract: In order to obtain well-distributed Pareto front with less number of high-fidelity analysis during simulation optimization, a Pareto multiobjective optimization method is put forward by combining the fitness function and sequence approximate technology. Research shows that better Pareto points can be identified for the multiobjective optimization problems with convex, nonconvex or discontinue Pareto front, and the number of high-fidelity analysis can be largely reduced.

Abstract: On the basis of analyzing the structure of planetary gear reducer, this paper points out that it’s necessary to make use of optimization design method to improve the design level of the planetary gear reducer. The optimization model of planet carrier is established and the process of optimization design is studied. Taking the XJB80 single arm planet carrier as an example, whose optimization design is performed by using ANSYS software. The spacing of connecting panel, thickness of sidewall, the inner radius of the connecting panel and some other parameters are selected as design variables, the yield strength and structural deformation limitation of planet carrier material are selected as state variables and the total volume is selected as objective function. The optimal structure size of the planet carrier is obtained, result shows that the corresponding volume is reduced by 21%, thus the manufacturing cost can be reduced. The study result has already been used by planetary gear reducer enterprise.

Abstract: This paper develops an opened forging and divided flow process for spiral bevel gears. By the help of rigid-plastic finite-element software DEFORM-3D, this paper designed cold-extruding part and concave die for bevel gear in the rear running gear of tri-motorcycle and simulated the forming process of cold-heading and extruding. On condition of guaranteeing shaping quality of teeth, the optimum diameter of die porthole was made sure by analyzing the effect of porthole size on volume of billet and plastic force. The experiment results show that the design parameter is reasonable and simulation results are helpful to the design of die.

Abstract: Based on the design theory of non-circular gears, using Visual Basic 6.0 Programming language secondary developed SolidWorks software, a system of elliptical gears parametric design and motion simulation was developed. 3D parametric modeling and motion simulation of elliptical gears can be achieved by this system. The development process of system is introduced in detail, and an example which designed a transmission with two identical three rank elliptical gears was given to illustrate the system operation process in detail. Using elliptical gears pair ratio cyclical curves acquired, compared with theoretical transmission ratio can verify design whether meet the requirements. Complex design and calculation and difficult 3D modeling problems of elliptical gears are solved, and this system can also improve design precision, shorten the development cycle, and guarantee the quality of products.