In this paper, a novel method of computing heating information for triangle heating is proposed for improving the accuracy of forming in an automated thermal forming system. The current method of computing heating information through triangle heating cannot be readily used for an automated thermal forming system because of a limited range of plates that the method can handle, and undesirable deformation on the boundary such as "over-bending" and buckling when the plate is heated using the computed heating information. Therefore, a lot of man-hours are required for correcting such defects, leading to delayed fabrication in the downstream fabrication processes. In order to overcome these problems, a method is developed using formulae for handling an extended range of plates, and considering the effect of the initial curvature of a plate in the computation of heating information. Various examples used in the ship construction show that the proposed method can improve the forming accuracy of the automated thermal forming system.

1. Introduction

The bow and stern of a ship directly influences the ship's operational efficiency. Therefore, it is necessary to design and fabricate such parts with good accuracy. This means that because a ship hull is obtained by assembling a collection of small parts, maintaining accuracy in forming each curved part and accurate assemblage of them are important.

In order to create a curved plate, a thermal forming method is usually used. In this method, the plate is heated using a gas torch that generates local expansion and shrinkage on the plate, inducing deformation on the heated area. It is a standard process in fabricating curved plates in most shipyards around the world.

The thermal forming method, however, generates intense heat and noise, making the working environment unfavorable. Moreover, it is considered as a bottleneck in the whole fabrication process because it is performed manually. Hence, the demand for automating this process has been raised constantly. Recently, Park et al. (2016) presented a full-fledged automated thermal forming system. The system consists of modules for measurement, heating information computation, and heating, and yields designed curved plates with good accuracy in most cases.

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