INTEGRATION OF PROCESS PLANNING WITH MRP AND CAPACITY PLANNING FOR BETTER SHOP PRODUCTION PLANNING AND CONTROL

In order to effectively utilize their manufacturing process in a production environment which is faced with an increased variety and quantity of completed products, subassemblies and component parts, many firms utilize computer data base production planning and control systems. These systems are often called Material Requirement Planning (MRP) Systems. MRP derived shop schedules which are the results of converting order book or forecast demand for completed products into master schedule completion dates through the use of a manufacturing capacity analysis. This closed loop MRP system without considering process plan is widely used throughout the current industry. However, traditionally, process plans are prepared days, weeks or even months prior to production. Available production capacity (due to current shop load) might have changed considerably during the time between creation of process plan and execution of production plan. Therefore, a lot of machines may become overloaded at operation time, and causes unexpected lateness. This research integrates the functions of process planning and production planning so as to allow process plans to be influenced by the production capacity which will be available at the time the parts will be produced. Three factors are found to significantly affect the performance of the research model. They are: complexity of the component parts, number of levels of the product structure, and system\u27s capacity (or in other words, quantities of the component parts to be manufactured). The average tardiness increases as the parts become more complicated, or the product structures have more levels, or the capacity of the system goes down (i.e. more component parts to be machined). Comparing with traditional manual process plans and closed loop MRP system, this research has obtained significant improvement (up to 88%) in the average tardiness. It is concluded that the research model can most benefit the machine shop which manufactures simple parts (less than three operations) with little capacity