Intelligent press-brake forming of sheet metals

Pao Yue-kong Library Electronic Theses Database

Intelligent press-brake forming of sheet metals

 

Author: Chan, Tze-chiu
Title: Intelligent press-brake forming of sheet metals
Degree: M.Sc.
Year: 1999
Subject: Sheet-metal work -- Data processing
Sheet-metal work -- Mathematical models
Intelligent control systems
Computer integrated manufacturing systems
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Manufacturing Engineering
Pages: v, 74, [50] leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1479247
URI: http://theses.lib.polyu.edu.hk/handle/200/3055
Abstract: In this project, a modern control algorithm is applied to a conventional sheet metal fabrication process, press-brake bending. In bending, a punch and a pair of die blocks are used to create bend for a blank sheet metal. The recovery or "springback" of the bend after the release of punch load is usually encountered in the bending process. The springback of the sheet metal results in a greater curvature of the bend than the desired one. The accuracy of the bending process depends very much on the inherent springback properties of the metal sheet. Recently, Kwok has developed a bending model and applies it to sharp corner die and punch in air bending. However, sharp corner tools cannot meet all the requirements in industrial bending processes (e.g. maximum curvature). In this project, a new algorithm and a modified mechanical model were developed for round corner tools to improve the bend shape control. The machine equipped with a piezoelectric force transducer, a laser displacement sensor, a computer vision system as well as a signal processing unit for real-time capturing the punch load, punch displacement and the geometry of the bend during the bending process. The performance of the adaptive control system has been evaluated through a series of bending experiments. The experiments have been conducted on electro-glavanized steel. Satisfactory results have been attained. The form accuracy was controlled within one degree in most instances. The results have also been compared with other sharp corner bending models and control algorithms. It is shown that the performance of the adaptive control system is superior than the sharp corner bending models and overbending technique. With the successful establishment of the adaptive control system, it is now feasible to produce accurate bends in the first time without the need for subsequent processing. Expensive components can also be formed right at the first time. The system can also be adapted for different materials and different variation of batch material quality. This not only improves the productivity of production but also eliminates the expensive trial-run production for process setup. The product quality can also be ensured in the long production run.

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