یک مطالعه بر روی سیستم برنامه ریزی عملیات خودکار برای فورج سرد قطعات غیر متقارن با استفاده از شبیه سازی FVM

A process planning system for cold forging of non-axisymmetric parts of comparatively simple shape was developed in this study. Programs for the system have been written with Visual LISP in AutoCAD. When a product is drawn on AutoCAD, it needs that the shape of the product is drawn with the solid line and the hidden line, and with the plane and front view, as well. At the plane, the system recognizes the external shape of non-axisymmetric portions—the number of the sides of the regular polygons and the radii of circles inscribing and circumscribing the polygon of n sides. At the front view, the system cognizes the diameter of axisymmetric portions and the height of the primitive geometries such as polygon, cylinder, cone, concave, convex, etc. And the system perceives that the list developed from the solid line must be formed by the operation of forward extrusion or upsetting, and that the list developed from the hidden line must be formed by the operation of backward extrusion. Suitability of the process planning was analyzed using SuperForge of FVM simulation package. The results of analysis showed good formability.

Up to now, works on the process planning of cold forging have been mainly concentrated on the rotationally symmetric parts. But works on non-axisymmetric parts was not so actively going on, due to difficulties of shape cognition and expression, calculations of the process variables such as forming load, effective strain, effective stress. As for the study about this fields, Cho et al. [1] have studied about the computer-aided design system for the stepped asymmetric parts and Kim et al. [2] proposed a simple kinematically admissible velocity field to determine the final-stage extrusion load and the average extruded length in the square-die forward extrusion of non-axisymmetric bars from circular billets. Kim et al. [3] have developed UBET program to predict forging load, die-cavity filling, and the preform in non-axisymmetric forging. Lee et al. [4] have analyzed forward and backward extrusion of hexagonal and trochoidal-shaped wrench bolts using UBET. The object of this study is to construct the automated process planning system of cold forging about relatively simple non-axisymmetric products such as special bolts being produced in the industries. To investigate formability and calculate the process variables such as forming load, and to verify suitability of operation sequences, a 3D metal forming simulation package—SuperForge was used. It has been reported that SuperForge provides results very close to those obtained from a validated 3D finite element analysis package—Deform 3D [5]. The finite volume technique used in SuperForge eliminates the remeshing problem that makes simulating a metal forming process with severe deformation so difficult. And the simulation time was saved considerably.

As the result of this study, the following conclusions were obtained: (1) The diameter to be considered in the regular polygon was the one of the circle calculated to the area after converting the area of regular polygon into the area of a circle. If larger than the billet diameter, the polygon pillar was formed through extrusion operation, and if smaller than the billet diameter, the polygon pillar was formed through upset operation. (2) By redesigning the operations considering clearance between die and workpiece, the process planning system applicable to the fields for cold forging of non-axisymmetric parts was constructed. (3) It was found that to design the operations sequence utilizing general process planning rules to non-axisymmetric parts was possible. (4) The polygon pillar was formed by the trapped extrusion operation, regardless of the ratio of the used circular billet sectional area to the polygon area. (5) It was found that non-axisymmetric shape such as hexagon and octagon was formed satisfactorily.