Simulation in production management is becoming increasingly important for efficient and competitive manufacturing. Production planners have to focus on several main goals: scheduling the plan efficiently, keeping inventories low, satisfying customer demand and anticipating the impact of every decision on the supply chain. They should understand how much inventory is needed to support demand during the production cycle and how much is needed to support a desired level of customer service. They should know how to reshape plans smoothly and responsively, without breaking the rhythm of the plan. And they should be able to visualize the impact of a planning decision on the entire supply chain. But before making decisions about management of the production they have to organize manufacturing system. In this article we would like to present example how to organize the level of stock to shorten the time of executing orders and satisfy the needs of any given customer by using simulations in software application Arena.