Computer-aided die design for axis-symmetric cold forging products by feature elimination

The authors consider forging to be a procedure for adding features to a raw material, and process planning to be the inverse procedure. Each step of the forging process is thought of as a combination of feature eliminating processes. Depending on the above, the authors have developed a CAD system to design forging sequences and die profiles. The system designs the forging sequences and die profiles from the product to its raw material by eliminating features, which is the inverse of forging processes. First, the system detects features from a product’s shape. A shape is represented by its cross-section including the axis with free curves. Its outline is described as successive finite vectors. The system extracts features by using the change of the vector direction. Second, the system searches a database of “manufacturing cases” using features such as search keys to find a candidate case in which the manufacturing process can be applied to the product. A manufacturing case is a data set having three kinds of data; search key, validity checking procedure of itself, and eliminating the procedure to get a partial preform after the elimination of the feature. Search key is the name of the feature to which a case can be applied. If the system finds a matched case by using the search key, it applies a validity checking procedure described in the matched case data. Please note that, by only eliminating features it is not possible to obtained a process plan. Each case must represent an actual forging method by which the feature can be manufactured. The validity checking procedure ensures that the eliminating process is actually to be realized as the inverse of forging. The system checks if the case can be applied on the feature or not by the validity checking procedure. If it passes, it eliminates the feature by the eliminating procedure described in the case. The procedures in each case are independent, but they exchange information about the cases and dimensions by using a working memory like a blackboard. Using the working memory, the system combines eliminating procedures automatically to get an actual manufacturing process. Thus, the system designs one forging process and preform, and after then, it also does the internal profiles of dies and exports them as point line into general purpose CAD systems. Repeating the above procedures, the system generates process plans and die profile design from the product’s shape to its raw materials. Multiple plans and profiles are designed by repeating the procedure recursively.