Improved coordination of the production cycle in the paper industry : To manage a wide product range and sequence-dependent changeovers

Abstract: Today the manufacturing industry is faced with the challenge to stay competitive in an era of shorter product lifecycles and increased product variety. This has forced manufacturing companies to deal with an increased amount of products and more and faster changes to the product line. The same trend can also be seen in the paper industry where bulk products decreasing and more diversified products in smaller lot-sizes increasing, with a greater focus on customer specific products. Traditionally the paper industry has focused on a volume- based strategy, which is not adapted to the new situation. This has led to problems with coordinating manufacturing, to manage a wide product range and sequence-dependent changeovers. Because of the sequence-dependent changeovers the production is often scheduled through a production cycle. This reduces the waste between grade changes and gives high machine utilization, but also leads to problem with producing the right quality at the right time. This leads to high inventory levels and difficulties to react and meet changes in demand. Therefore there is a need for paper producers with a wide range of products to find a balance between high machine utilization and the ability to react to changes in demand. The aim of this thesis is to investigate how paper producers can coordinate their production cycle and by that manage a wide product range with sequence- dependent changeovers to achieve mix flexibility and improve the scheduling at the plant level. To coordinate the production cycle on a paper machine the product wheel concept has been used, which is a technique for production scheduling, developed and modified from the lean tool heijunka to fit in the process industry. In this thesis a single case study has been done on a producer of colored tissue. Findings from this thesis show a shorter production cycle with fewer products in each cycle, which results in the opportunity to be more flexible in the production, as there are more opportunities to produce a specific product during a year. The product wheel concept is also shown to take in to account the key factors that are important for mix flexibility. The results from the case study show that the product wheel concept is an appropriate model for scheduling problems in the context of managing a wide product range on a paper machine. The production wheel concept is though a heuristic model and will require knowledge and experience about the observed object.