Beslutsmodell för inköp och lagerhållning av motorer i ett produktionssystem : En fallstudie på Sandvik

Sammanfattning: Abstract It is important to choose which spare parts to keep in stock. With the right spareparts in stock the costs for inventory and production loss will decrease. Cavalieri et al. (2008) highlights that the balance between inventory cost and production loss is underestimated.  It affects the company and must be considered before decision on purchase. The problem with spare engines is that they are all more or less critical for the production. That can be a reason for why no previous research targeting engines and classification of with engine should be kept in stock has been found. This study can help to fill that gap in research and contribute general knowledge that can be used by all company’s and not only the one where the study took place. The purpose with this thesis has been to design and develop a decision model for keeping the right engines in stock for a production system. In the decision model there is also a system for how engines should be classified through leadtime analysis to get the priority order to purchase engines. The model consists of four steps to give a foundation regarding purchase of the spare engine: lead time analysis, cost for production loss, purchase cost and warehousing cost. To classify the engines the study has detected leadtime as the most important factor. The leadtime from the order is placed until delivery of a new engine to the company. After constructing the model it has been tested and evaluated in a operation. Within Sandvik SMT at Rörverk 60 the model was tested. The test showed that the model is user friendly and gives a foundation to make a decision about purchase.  Problems found with the model are the many different ways to calculate the different steps in the model. The cost for production loss can be calculated in different ways. In the model it is important that the same equation is used all of the time to give a result that can be used to compare between different cases and decisions. A decision on how the work should be carried out should be made when the model is being implemented to strengthen the validity of the model.