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.

An alternative twin rudder system known as the Gate Rudder© has been applied to newbuild vessels and an existing ship with the aim to improve their hydrodynamic performance and reduce greenhouse gas emissions. The system consists of two asymmetric cross-sections and L-shaped blades located either side of a propeller. The blades generate thrust (duct effect) from the propeller and ship-included flow. Initially, forces and moments of a single blade were measured using a 6-axis strain gauge sensor in the towing tank without a propeller. An alternative measuring device, consisting of a Piezoelectric Macro-Fiber Composite Actuator, was then attached to the blade to investigate flow-induced forces. Finally, Computational Fluid Dynamic (CFD) simulations were compared with the experimental results to identify the source of the oscillating forces. The results show that flow-induced vibrations may occur on the gate rudder blades at both shedding frequencies and the structure’s natural frequency.

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