Automatic Edge Machining System for Collar Plate

As the performance standards for protective coatings of the International Maritime Organization (IMO) became mandatory, shipyards must perform 2R or 3P grinding on the edges of collar plates. However, 2R or 3P grinding by manual work can cause many problems in terms of work environment and productivity. In this study, an automatic edge machining system was designed for collar plates used in hull structure for shear reinforcement of slot holes. Shape recognition and processing path generation algorithm were introduced to establish edge machining process. It is expected that an automation system capable of meeting IMO regulation will be constructed and productivity will be improved at the same time. Introduction The International Maritime Organization (IMO) made the regulation, performance standards for protective coatings, mandatory to minimize hull corrosion and improve structural stability. This regulation applies to the water ballast tanks of all newly constructed ships with 500GT or more and the double hull structure of bulk carriers with the entire vessel length of more than 150m. However, for application, various related technical issues, such as hull surface pretreatment, paint selection, painting process and inspection, must be addressed effectively [1]. In particular, for hull surface pretreatment, there are technical issues that the sharp edges of collar plates, which are installed for shear reinforcement of slot holes must be rounded to the minimum radius of 2mm (2R), or the edges must be subjected to 3-pass (3P) grinding [2]. Most shipyards depend on manual work and use general grinders for the edge machining of collar plates, and they are performing only 1-pass work. Therefore, work intensity must increase significantly to meet the 2R or 3P regulations with the existing method, raising concerns over the musculoskeletal disorder occurrence to workers and thus degradation in pretreatment quality. To address such problems, it is necessary to develop and apply a fully automated or partially automated edge machining system instead of manual work. Meanwhile, studies on grinding automation can be divided into the ones related to the cutting force of the tool as well as cutting conditions and the others related to the processing path creation and optimization. Joo et al. [3] performed computer simulation and cutting experiments to establish a mathematical model for predicting the cutting force of face milling. As a result, they confirmed that the face milling cutting force could be predicted under various conditions. Kim et al. [4] determined optimal cutting conditions using complex experimental designs in a milling process that uses the existing machine tools. Studies on processing path creation and optimization include the cutting-path-based manufacturing simulation and experimental research performed by Wang et al. [5]. This study proposed a method for predicting the stress distribution and deformation shapes of parts through simulation and milling experiments on various milling-cutting paths for aircraft blade thin plate parts. These previous studies focused on in-depth research topics, such as the cutting force of the milling tool, cutting conditions, and cutting path based on commercial milling machine tools or the existing experimental devices. However, it is urgently necessary to develop a new-type system to automate the edge machining of collar plates of various shapes, and to meet the IMO regulations. In this study, an automatic edge machining system was designed for collar plates, and a manufacturing process was established by applying the shape recognition and process path generation algorithm. It is expected that an automation system capable of meeting IMO regulation will be constructed and productivity will be improved at the same time.