Demands of the metal forming industry made the real time simulation method programs essential for good manufacturing of the finished product. In this paper, the CLF (critical liquid fraction) factor which is necessary for determining whether or not the solidification needs feeder and also where the feeder/feeders is/are needed to be placed is studied. If the value of liquid phase fraction inside a certain region is less than CLF, then liquid cannot pass through this region even under pressure or in the same meaning the feeder does not feed into more depth anymore. This study simulates the CLF factor in a range from 20% to 80% on nodular cast iron castings (GGG50). The solid model formation is considered and discussed with simulation program used. The results showed that by increasing CLF factor, the shrinkage ratio in feeder cavity decreases. (c) 2007 Elsevier B.V. All rights reserved.