A PC-BASED CAD/CAM SYSTEM FOR SHEET METAL BENDING

Abstract

In sheet metal working, hours of drawing and calculation efforts are spent to determine blank shapes and sizes, and feasible and effective bending sequences. Manual planning often depends heavily on experience and is highly subjective, labour intensive, inconsistent, tedious and error-prone. To alleviate the above problems, a feature-based system for sheet metal bending has been developed. The PC-based system is built on top of AutoCAD. The platform is chosen because of its low cost and popularity in industry. A two-dimensional or a three-dimensional part can be designed in a design-with-features environment using the standard features from a feature library, and modified using the functions of an operation library. The user can also design the part using the conventional CAD commands and then define the features. Flat plate features that are joined by linear bends are considered. The design procedures are planned to capture the high level part representation which is required for downstream applications. The flat pattern development module adapts the part representation data and performs folding and unfolding with bend allowance consideration. The generated flat patterns can be represented in the formats which are required by existing nesting, cutting and bending software developed over the last few years. The bending simulation module generates feasible bending sequences by simulating the bending process and checking for hardware interference during bending. The simulation starts from the final configuration of the part and reasons towards the flat pattern stage. By reversing a feasible unfolding sequence, a feasible bending sequence is obtained. The outputs of the program are the flat pattern drawings with bend sequence labels and the selected tool information, which can be used for programming the CNC press brake. Using real-life products, the system has been proven to be more efficient than the conventional approach.