Block spatial scheduling modelling and application in shipbuilding

Abstract

With the wide application of module-shipbuilding technology, problems related to block spatial scheduling occur in various working areas, and this restricts the productivity of shipbuilding. To address the problems and to obtain the optimum block sequence and spatial layout, typical block features and work plates were investigated. A heuristic spatial scheduling model was established based on the investigation and proposed strategies with the objective to minimise makespan. With the heuristic algorithm, a block spatial scheduling system was developed and implemented with real data from a large ship. Through the spatial scheduling system, visual results of daily block layouts and progress charts for all blocks can be easily obtained and work orders can also be created for site workers. Several other spatial scheduling methods are described and compared with the above-mentioned heuristic algorithm. The result shows that the heuristic algorithm is better than Cplex and a genetic algorithm in solving large-scale block scheduling, and the heuristic algorithm is better than a grid algorithm and manual scheduling in all aspects such as makespan, utilisation of work plates, runtime of scheduling and on-time delivery. The developed block spatial scheduling system is applied in a block production shop of a modern shipyard and shows good performance. IntroductionShipbuilding is a traditional industry for manufacturing large and heavy machines and devices, which is usually operated under a build-to-order strategy. To improve efficiency, shorten delivery time, and reduce cost, moduleshipbuilding mode has come into wide application in recent years, especially when huge docks and giant cranes are employed. In this mode, a ship is decomposed into blocks which are produced on the shop floor and then are assembled into the ship in the shipyard. Usually the shipbuilding process is classified into seven levels in the shipyard such as part fabrication, part assembly, section assembly, sub-block assembly, block assembly, super block assembly and hull erection. Most shipbuilding companies focus on their core business and outsource other works, such as part fabrication and assembly to their partner plants. When parts or sections are finished, they are carried to the shipyard for assembly and outfitting, and then commissioning. Block assembly is generally the bottleneck that limits the productivity because block assembly is conducted in work plates which are equipped with expensive handling equipments like goliath cranes and moulding beds. Also block assembly is the most time-consuming component of all. Since shipbuilding manufacturing mode keeps changing, it makes block assembly more complicated and more important in achieving high productivity. Most resources and efforts are put into improving block assembly. As a result, perfect planning and controlling of human resources, material resources and facilities is the key to meeting due dates, minimising makespan, improving efficiency, and reducing cost and work delays. It can also improve...

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