Designing MRP Model in the Condition of Capacity Constraints andVariability of Delivery for Critical Items in ABC Inventory Model âÂÂCaseStudy in National Company of SouthâÂÂs Oil-richâÂÂ

In productive enterprises, timely preparation and procurement of goods is very important due to that related costs to the production and working capitals of organization is severely affected. In available scientific methods, including MRP, regardless of resource constraints and other factors, the amount of lead time of goods has always considered to be fixed. In this paper, then a model will present that lead time of goods is considered as dynamic by using statistical and also effectiveness models from internal and external environment variables of organization and optimized the cost of production in order to reduce the latency in timely receiving and balancing the warehousing time. At the end, researcher with the implementation of issue in a simulated environment and compare it with the real environment, shows the advantage of proposed model compared to other models by numbers and figures.