The Research of Shipbuilding Schedule Planning and Simulation Optimization Technique Based on Constant Work-In-Process System
Authors: Yue Wang , Rui Ma , Yan Lin 
Published: January 2018

This paper proposes a shipbuilding schedule planning system based on the constant work-in-process (CONWIP) as a new way to deepen the schedule planning management and implement the lean shipbuilding. It fully discusses the forms, key elements, the ways and processes of implementation, etc. It demonstrates the advantages of the CONWIP system over the KANBAN system and the feasibility of applying the CONWIP system in shipbuilding by taking the flat section manufacturing of the shipbuilding as an example and applying the plant-simulation software to simulation analysis. We also provide the corresponding solutions to solve the problems, found in the application of the CONWIP system, and discuss the process and result of a simulation of the solutions.

1. Background
The level and the structure of the shipbuilding production plan are relatively complex, and the derivative of the plan has many kinds of the species. After many years of researches and practices of shipbuilding enterprises in domestic and foreign, the types and classifications of the shipbuilding production plan have become consistent, which means that the shipbuilding production plan is composed of the three types of plans: basic plan, load plan, schedule plan. Basic plan is a programmatic plan in system, load plan is a system of protection plan, and schedule plan is implementation plan. Shipbuilding production planning system is shown in Table 1.
Schedule plan usually decomposes the plan into each workstation and process, and then comes into the schedule plan of workstations and processes according to the general production task, the basic plan and building procedure. The plan mainly contains large schedule plan, medium schedule plan, and detailed schedule plan. Large schedule plan mainly refers to the construction of the main process planning, main material demand date, and comprehensive plan of each professional drawing; the medium schedule plan includes preinstallment medium schedule plan, the succeeding medium schedule plan, and installment medium schedule plan, which are based on the erection network scheduling; detailed schedule plan mainly refers to the monthly, weekly, and daily production plan which are made on the standard of the medium schedule plan by the production department. The traditional shipbuilding planning is top-down push plan system. In this system, it requires a complete production management data for production department from the design and planning departments. Load plan and schedule plan are strictly made and carried out on the basis of production load balance which conducted by working hours, capacity, and the data of energy consumption. However, because of the planning system in which monthly plan is made to meet the line table as a starting point, so it lacks of the balance of the actual state. Eventually, this plan system leads to a poor balance and operability, random plan execution, and a great deviation in the actual production situation of the system, because of these the scheduling production relies heavily on spot control. Therefore, during the current time when the lean shipbuilding idea is a consensus of the industry development, how to enhance the schedule planning management has become a key issue for the realization of the lean shipbuilding.