In order to obtain the machining requirements of the machining features, it is necessary to develop a proper fixture locating scheme to constrain correctly the degrees of freedom (DOFs) of a workpart. In this paper, a machining-requirement-based design approach to locating scheme is for the first time created. Firstly, the relationship is established between the machining dimensions and the DOFs to be constrained theoretically. Secondly, the fixture locating scheme is established to characterize practical constrained DOFs of a workpiece in terms of the locator number and positions. As a result, locating correctness is defined according to the relationship between the theoretical constrained DOFs and the practical constrained DOFs, and then the determination algorithm of locating parameters is proposed quantitatively for the first time to design the fixture locating scheme.
During the milling operation, milling forces are the main factor to cause the machining deformation of the workpiece. The flow stress of Al 7075-T7451 was first described as a function of strain, stain rate and temperature in order to obtain the true behavior in machining process. Second, a finite element method of milling process of Al 7075-T7451 was developed to obtain milling force simulations. Finally, simulated results are compared with experimental data and are shown to be in good agreement with each other.
Machining deformation has always been a bottleneck issue in the manufacturing field of aeronautical monolithic components. On the base of finite element method, the effect of the process steps and tool paths on the workpiece stiffness and the redistribution of residual stress in the machining process of aeronautical frame monolithic component was investigated under the given fixturing scheme. Thus, the prediction of the workpiece deformation can be carried out in reason. The proposed simulation approach to deformation analysis can be used to observe the true characteristic of milling forces and machining deformations. Therefore, the proposed method can supply the theoretical basis for the determination of the optimal process parameters.
In the field of aeronautical and astronautical manufacturing, milling is a basic machining process by which a surface is generated by progressive chip removal. Therefore, this paper reports a complete procedure of the finite element model for the 3D oblique milling process using the commercial software package ABAQUS. Effect of various parameters on cutting forces is mainly discussed. The model correctly exhibits the observed transition from small to large force with increasing cutting speed and cutting depth.
In order to efficiently design a fixture, it is necessary to establish a standard fixel library for CAFD system. Therefore, a SQL Server-based development technology is first employed to manage the parameterized fixel models. And then, in order to construct a fixel model, MFC is adopted to carry out the secondary development of Unigraph environment. Thus, arbitrary fixel can be dimension-drive designed according to a parameterized fixel model. The establishment of the fixel library can to a great extent reduce the trivial and repetitive tasks in the fixture design.
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