• We often know well in advance what has to be produced
• We can use computer programs to come up with a ‘near perfect’ schedule for all jobs, ahead of time.
• These methods at the present time are not well enough developed to handle sudden disruptions on the shop floor (See next section on Shop Floor Control).
• Schedules are often made up weekly
*************** ADD DETAILS FOR MRP I and MRP II
• This is one very popular approach to planning
• Uses Master Production Schedules to determine how much of each product should be produced within given periods. Master Production Schedules are based on customer, or projected demand.
• The elements used by MRP to plan are,
- Master Production Plan (Schedule)
- Current of Purchased and Manufactured Orders
- Rules for each part produced (including WIP)
• The rules about each step in production include,
- Order quantity per final part
• MRP then tries to determine quantities required using the data input from the users, and a set of rules, such as,
- Fixed Order Quantity - Product are produced as required using a prespecified lot size.
- Economic Order Quantity - The cost of carrying inventory is weighed off against the cost of setup for one production run.
- Lot for lot - Lots are produced as required, any batch size.
- Fixed-period Order Quantity - Produce parts to cover more than a single order.
• Lot sizes required are subtracted from available stocks.
• The required production quantities are used to order from suppliers, etc, while considering lead times, and delays.
• You should note that this approach is concerned more with inventory minimization than with utilization of machines.
• While this system can lead to easy production scheduling, it is susceptible to errors in BOMs, routings, etc.
- improved competitive position
- improved coordination of marketing and finance
• MRP II (Manufacturing Resources Planning) - A closed-loop MRP system that, at a minimum, includes detailed capacity analysis (see next section). Some MRP II systems include the business plan in the closed-loop system.
• While MRP is concerned with determining how much should be produced, it is not concerned with how to produce it.
• Capacity planners attempt to determine how to assign jobs to machines, people, etc.
• Information used by capacity planners includes,
- Orders in process (order status)
- Routings, including setup and run time (from process plans)
• There are some strategies used by the Capacity Planner to Assign jobs to machines,
- Splitting of lots (batches) across identical machines
- Splitting of lots to expedite a smaller quantity
- Sequencing of lots to minimize setup times
- Alternative routings that require different resources
- Loading a facility by weight, volume, etc. (eg. heat treating)
• After jobs have been assigned to machines, the capacity of the machines must be considered.