Studies on springback in I.C. leadframe forming by using a servo-motor-actuated forming machine equipped with a machine vision system

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Studies on springback in I.C. leadframe forming by using a servo-motor-actuated forming machine equipped with a machine vision system

 

Author: Ngan, Ka-wah
Title: Studies on springback in I.C. leadframe forming by using a servo-motor-actuated forming machine equipped with a machine vision system
Degree: M.Sc.
Year: 2000
Subject: Integrated circuits -- Design and construction
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Manufacturing Engineering
Pages: x, 114, 34 leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1527683
URI: http://theses.lib.polyu.edu.hk/handle/200/3721
Abstract: Springback is a common phenomenon in sheet metal forming. However, most of the studies on the problems of springback are based on wide strips. Therefore, the objective of this dissertation project is to develop an automatic servo-motor-actuated forming fixture and to incorporate a machine vision system for studying the springback in I.C. leadframe forming. A servo-motor-actuated system has been successfully developed to accurately control the position and the speed of the punch movement, so that, the springback bahaviour in I.C. leadframe forming can be studied in various aspects. Besides, a springback angle measurement program called 'Machine Vision system for Microbeam Bent Angle Measurement' (MVMBAM) has been incorporated to on-line measure the springback angle with mean error of -0.0906o and standard deviation of 0.7334o. The program MVMBAM is calibrated by using a calibration block with three circular patterns marked on it. To reduce the computing time, the processing area is confined to a small area called Region of Interest (ROI). The uninterested area is covered by a mask in black colour. To determine the center-lines of the leads, two groups of vertical parallel lines and horizontal parallel lines are superimposed on the images of the un-bent lead and the bent lead respectively. By locating the intersecting points between the edges of the leads and the parallel lines, the center-lines of the leads can be found by applying linear regression. A series of mathematical operations are then performed to determine the springback angle. Experiments were conducted to investigate the effects of die gap, die radius, anisotropic and mechanical properties of the leadframes on springback. The experimental results show that springback increases with increasing die gap and die radius. On the contrary, it is found that the larger the Young's modulus, the smaller the springback angle. Besides, the springback of the specimens oriented in the rolling direction is greater than that of oriented perpendicular to the rolling direction.

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