Search

The die design of forged products greatly affects the quality, cost, and delivery of cold- and warm-forged products. However, such design is often not easy even for experienced engineers because extensive knowledge and experience of plastic forming, forging, blanking, and punching are required. This paper proposes a general forging die design method termed GeneDie on the basis of the basic die structure and the forming surfaces configuration which are introduced as basic concepts for the support of simple but general die design. The basic die structure is the relative positional inter-relationship among the components of forging dies and is used to represent the structure of forging dies simply. Meanwhile, the forming surfaces configuration is the correspondence between functions allocated to the surfaces of forging dies and the surfaces of a forged product and used to represent the shapes of forming dies concisely. Die design plans are generated by exhaustively assuming a basic die structure and a forming surfaces configuration that satisfy design requirements and then verifying design constraints regarding formability, workability, and economy. An experimental knowledge base is implemented adopting the GeneDie method and applied to a forging process plan for an electrical connector. Experimental results show that die design plans that are functionally equivalent to those of an experienced engineer are included in the plans generated for all forming steps of the forging process plan.

A forging process planning method, including blanking and punching, termed General Step Reduction and Enlargement (GeneSteR+E), is discussed for cold- and warm-forged products. It is applicable to non-axisymmetric forged products that consist totally of non-axisymmetric shape elements and can generate multiple process plans without relying on design cases. The shape of a forged product is split into outer and inner shapes, which are then split into axisymmetric and non-axisymmetric shape representation units termed basic elements (BEs) according to shape separation rules. Process plans are generated in reverse order from a final forged product by applying shape transformation rules that reduce the number of steps between BEs until a billet (or a blank) is obtained. The shape transformation rules are defined not only for forging, but also blanking and punching. An experimental knowledge base was implemented and applied to several non-axisymmetric forged products, such as an electrical connector. The results show that the GeneSteR+E method is applicable to the design of forging processes including blanking and punching of totally non-axisymmetric products and can generate satisfactory process plans comparable to those developed by an experienced engineer.

Fine blanking (FB) is a press shearing process that can obtain a smooth clean-cut sheared edge surface in one press stroke. However, the convex portion of the punched out part or product will generally include a large amount of die-roll or shear-droop defined by a component (Z) in the shear plane direction (z-direction) as well as in the planar direction (x-direction). The droop often will cause various product malfunctions, such as decrease in the contact length as in the engagement of a gear pair by the larger z-directional droop, and a reduction of the effective contact area with the x-directional droop. Since the FB process inevitably causes droop, leading to the reduced functionality of parts, the amount of droop is an important factor, when fabricating parts, using the FB method. Therefore, our final aim is to realize fine-blanked components without droop. As the first step, we attempted to predict the dependence of the amount of droop on the FB parameters which include the punch-die clearance, the material and its thickness, the included angle, and the radius of the convex portion in the case of common work piece profile components. From careful observation of the experimental results for various work materials and that were fine-blanked by an FB die set, we were able to obtain a simple and integrated formula to predict the amount of droop. We believe that the use of this formula will increase the efficiency of trial-and-error procedures performed before mass production, enabling the manufacture of components for customers with a shorter lead time.

We propose a process planning method, which is termed the General Step Reduction (GeneSteR) method, for non-axisymmetrical cold- and warm-forged products. The GeneSteR method can produce process plans for non-axisymmetrical forged products without relying on any design cases. The basic principle of the GeneSteR method is to produce reversed forging process plans by reducing the steps that are contained in a forged product by a stepwise approach until a cylindrical billet is obtained. An experimental knowledge base was implemented based on the GeneSteR method and was applied to a universal joint yoke used in automobiles. The experimental results show that the proposed method has sufficient capability to generate satisfactory process plans that include a comparable plan as designed by an experienced engineer in a shorter time.

In conjunction with experimental simulation of metal forming, the development of model materials, by which forming simulation can be carried out at a low stress level at room temperature, was performed. The model materials are mixtures of microcrystalline wax, rosin, mineral oil and powder. The flow curves of the model materials show three typical configurations, i.e., work-softening type, steady state deformation type and work-hardening type, which are observed in metals and alloys. The above configurations of the flow curves of the model materials could be changed and controlled by adjusting powder content. The flow curves of the model material could be predicted accurately using the work-hardening rate equation determined in this work. As an application example, experiments on and visio-plasticity analyses of the plane strain backward extrusion of magnesium alloy and its model material, which represent the deformation property of work-softening type materials, were carried out. We confirmed that the material flow and strain conditions in both materials correspond to each other with sufficient accuracy for engineering purpose.

Metal flow representing continuous plastic deformation in a metal forming process is visualized by mathematical tequnique such as FEM analysis or by experimental tequnique such as Visioplasticity method. The authors developed the physical simulation system by which a metal flow characteristics and strain conditions in the workpiece can be visualized quantitatively in the realistic deformation conditions. The flow field can be observed from the distortion of grid pattern which has been placed by print or by machining on the observation plane in the physical simulation.Model material, Plasticine in the present workpiece, or actual material, was deformed by in-cremental steps, and the metal flow and strain condition in a workpiece in non-steady state deformation condition could be observed and determined by numerical analyses. The above procedure was applied to optimal process design of bolt head forging process, heading.

The design tasks of cold forged products are very important because they have a great influence on the quality of the final products and the life of the forging dies. However, the design expertise required for the design tends to get scattered and lost, and therefore there is a need for a framework that will enable the accumulation, utilization and evolution of this expertise. The authors have been developing a knowledge-based system to support process planning and the design of dies and die-sets for cold forged products. The knowledge base contains design knowledge on cold forging, which is systematized based on the formal definition of die design problems and on methods with high generality for resolving these problems. These features facilitate the improvement of product quality using an exhaustive search of process plans and die structures, and the improvement of design performance by automating the design work. They also make it easier to pass on and evolve expertise by allowing design experts to self audit and maintain their own knowledge base. The proposed system has been applied to several cold forged products. Experiments show that it can generate multiple forging process plans, dies, and die-sets based on the design knowledge, and that feasible solutions can be obtained within a practical time span.

We report on a knowledge-based system for process planning in cold forging. In this system, a forged product is represented as an aggregation of forming patterns that consists of cylindrical pillar parts. The basic principle of the inference method we propose is to adjust the diameters of neighboring stepped cylinders so that they are identical. Plural deformable process plans are generated using expert knowledge about working limits, die configurations, and metal flow. This system can eliminate ineffective plans by using the knowledge of how to combine plural forming patterns into a single process. Moreover, it can evaluate process plans and interactively select the optimal one by considering production costs, the forming load, the effective strain in the product, the equipment, and other factors. We applied this system to actual forged products. As a result, this system is widely applicable to various shapes and types of equipment and can improve both maintenance and operation.

We propose a knowledge-based system for process planning in cold forging. In our study, we had developed FORTEK-L (FORging Technology of process planning using Expert Knowledge for Layout), which is widely applicable to various shapes and types of equipment. In the next step, we have developed a knowledge-based die configuration design system, FORTEK-D (Die configuration design), which can generate suitable die configurations from layouts obtained from FORTEK-L. In the development of FORTEK-D, we have analyzed and reproduced the expert engineer’s thinking process during die configuration design. Moreover, we have formulated the data representation, inference method, and knowledge-base for use with this system. In accordance with the formulation, we have developed a prototype system. We applied FORTEK-D to actual forged products and obtained appropriate results. The knowledge using the basic principle is widely applicable to various shapes and on a variety of equipment. Therefore, the abilities to maintain and operate the system have been improved.