Job shop production system is characterized by manufacturing feature with low volume and high variety of product designs. It is a process with high flexibility which produces a wide variety of products in low quantities and high divergence. Generally, a job shop production line follows sequence of orders with specific process flow for each particular job. In each work station, special skills of workers are required to perform explicit tasks. Due to these distinctive process characteristics, effective production planning is crucial for job shop manufacturing process. Ineffective production planning may cause several types of waste in production line. This study proposed simulation modeling for job shop production process in machine parts manufacturing. Simulation models present the great benefits to assist in performance improving, problems solving, including a great help in decision making. The experimental results of the study showed that group technology, plant layout, job enlargement, and capacity expansion accomplished the definite value in reducing operating cost and increasing average worker utilization, thereby increasing the efficiency of the system.