This paper is a report of a simulation study that investigates a dynamic approach to scheduling jobs in a conventional shop floor, especially in an assemoly-type welding process. We consider both JIT arrival and JIT delivery. Various dispatching rules are tested for the following performance measures; mean flow time, rate of tardy jobs, mean tardiness, sum of mean tardiness and mean earliness. The results indicate that SPT rule is the best for the mean flow time. MSLACK that we suggest in this paper, is the best for the mean tardiness and the sum of mean tardiness and mean earliness. However, it is not clear that which rule is the best for the rate of tardy jobs.