Due to the increasing globalisation, the organisations all over the world are facing intensified competition and higher customer requirements. To be able to compete with other organisations it is essential to optimize production. Thereby improvements regarding shorter lead times are common in the manufacturing industri. Lead time reduction is generally associated with several benefits such as flexibility and increased profits due to minimization of tied up capital and reduced risks of incorrect demand forecasting. This thesis consists of a case study conducted at Scania Ferruform. Their aim is to deliver high quality products in a customer order sequence in a single piece flow, which requires short lead times. However the possibility is limited due to the long lead times and large inventories of their production. The case study is delimitated to only investigate the part of the production flow, which has the longest lead time. Furthermore, the study will not investigate the possibilities of investing in new machinery. By conducting a value stream mapping, the inventories impact on the lead time was visualized. Thereafter the inventories were analysed through two different perspectives; need of inventory and the actual content of inventory. This resulted in insights regarding which factors that had a negative impact on the lead time. The focus of the study was chosen to address the inventory placed after the machine that was currently seen as the bottleneck of the production. This due to the fact that the bottleneck delimitates the throughput of the production. The following factors affecting the lead time was identified; unnecessary inventory, material shortages, set-up time, poor utilization of the bottleneck, unplanned downtime and transportation. Some of these factors were caused by the lack of connection between all processes and the production planning. Furthermore, it was identified that this lack of production planning, resulted in the absence of established guidelines concerning the inventory levels. By connecting all processes to the production planning and introducing guidelines regarding how much to stock, the lead time can be reduced. Improving the inventory content in terms of only stocking the products which is needed, results in a lead time reduction in the flow by 8%. Additionally, there are other improvements such as reduced set-up time, transportation and unplanned downtime, which will shorter the lead further and also increase the productivity.Moreover, the case study showed that the largest inventory, with the longest lead time, was created on purpose by building up stock and having a large safety stock. However, analysis indicated the possibility of reducing the lead time by decreasing the inventory. This can be done by further investigating the possibilities of smoothen the production and optimizing the safety stock levels. A potential lead time reduction of 15% was identified, which in combination with the improved inventory after the bottleneck results in 23% shorter lead time. The conclusion is that lead time can be reduced by well thought out production planning, deliberate inventories and guidelines. However careful considerations are necessary regarding what the actual effects will be on the supply chain before implementing any major changes.