On the Development of Protective Devices for Bending Press
Authors: Ahn Dung Ngô, Tony Venditti, Phuong Tran Nguyen Duy
Abstract: Brake presses are machines which are widely found in the manufacturing industry. They enable metal sheets and plates to be bent in multiple ways so as to shape a wide variety of parts. The very principle by which these machines function creates a pinch and crushing zone for operators notably as far as their hands and fingers are concerned. This paper recounts research projects conducted in the last 30 years at École de Technologie Supérieure (ETS). Historically, the first publication described the state of the situation in the 1990s in terms of safety of brake presses found in the transport equipment and machine manufacturing industry in Quebec. It was found that a small percentage of the brake presses surveyed were properly equipped with adequate safety devices. The research report showed a number of problematic situations arising in industry such as complex shapes (for example, cones, tubes, boxes with multiples bends) which render use of protective devices available at the time difficult and even unfeasible. To address the issue of the low prevalence of protective devices on brake presses, a study on the feasibility and applicability of light curtains on these machines was conducted. It was shown that the mode of operation of the light curtain as well as the geometry of the work-pieces were crucial factors which determined the feasibility of light curtains as effective protective devices on brake presses. Difficulties in using these devices in certain cases were uncovered. To alleviate these difficulties, a further research project sought to develop more flexible protective device on brake press. The concept was based on computer vision. A bracelet was to be worn by the operator. A system of cameras captured images of the operator’s hands and a computer algorithm calculated in real time the position of the hand with respect to a defined hazard zone. From the risk assessment and reduction viewpoint, a risk evaluation methodology based on fuzzy numbers was developed to address the issue of lack of reliability both machine and human-related in assessing probability of occurrence of hazardous events. A risk reduction methodology was also proposed helping to identify action priorities in an analytical way.
Keywords: brake press safety, machine safety, smart gloves, fuzzy risk assessment
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