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Title: A cost-effective device for online measurement of sheet metal bending angle on CNC press brakes based on capacitive sensors

Authors: Stefanos Raftopoulos; George-Christopher Vosniakos

Addresses: National Technical University of Athens, School of Mechanical Engineering, Manufacturing Technology Section, Heroon Polytehneiou 9, 15780 Athens, Greece ' National Technical University of Athens, School of Mechanical Engineering, Manufacturing Technology Section, Heroon Polytehneiou 9, 15780 Athens, Greece

Abstract: Sheet metal bending on press brakes is one of the most widespread manufacturing processes. A common issue in press brake bending is the deviation of the actual bending angle from the theoretical one due to elastic spring-back of the sheet metal. This is typically rectified by a systematic trial-and-error process, which has to be based on a suitable measuring device that is flexible enough to adapt to a wide range of computer numerically controlled machines, accurate enough with respect to modern manufacturing needs and cost effective enough to be used on low cost press brakes. This work presents the development of such a device resembling a miniature robotic arm and employing capacitive sensors. Two stepping motors adapt the arm to any bending angle sheet configuration. The measuring process is commanded by a microcontroller. Statistical evidence on accuracy and repeatability of the system is provided, being better than 0.1° and 0.3° whilst cost is kept reasonable.

Keywords: press brake; elastic springback; measurement; capacitive sensors; microcontroller; bending angle; repeatability; stepping motors; sheet metal.

DOI: 10.1504/IJMMS.2020.109796

International Journal of Mechatronics and Manufacturing Systems, 2020 Vol.13 No.2, pp.153 - 168

Received: 17 Feb 2020
Accepted: 28 Apr 2020

Published online: 16 Sep 2020 *

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