Purpose – The purpose with this study is to investigate how an assembly line for products with long cycle time, high product variation and operators who follow the products through the flow can be planned for a high resource utilization as well as the challenges that can arise when planning an assembly line with an increasing demand and how these can be handled.

Method – To fulfill the purpose of this study a case study was conducted at Mastec Components AB in Vaggeryd. The empirical data gathered from the case study was obtained through interviews, observations and document studies. The empirical data was then analysed against theory, which means that pattern matching was used and the analyse led to the studies results.

Findings – This study illustrates how an assembly line with special demands can be planned to gain high resource utilization. When the products cycle times are multiple they can be sorted into product families to simplify the planning and it also enables a tacted planning method to be used. The study also presents how the usage of time buffers can facilitate the planning of an assembly line. Moreover the study illuminates the importance of controlling tact, both from the customer and the own production. When demand increases it is important that the production line is capable to keep up, therefore some arrangements can be done to reduce waste and increase capacity. Possible alternatives can be buffers, allocating resources and parallel assembly lines.

Implications – The study investigates a type of assembly line where the operators follow the products through the flow. This type of assembly line is unexplored in theory and thereby a knowledge gap has been identified which partly have been covered by this study. Further on, the study contributed to an increased understanding of the consequences that occur when operators follow the flow and when products have long varying cycle times. The study also shows the value of calculating tact and use the advantages from it to easier handle variation in demand.

Limitations – The case study was performed as one case study which means that only one unit has been analysed. This was due to the lack of resources to do several case studies, both regarding time and ability to find more facilities with similar conditions. If it were possible to conduct more case studies the results could have been more general.

Keywords – Tact, tact time, tacted planning, assembly line, planning, operators, buffer.