As we develop from discrete to repetitive, materials planning goes from job order based to demand-pull, or rate based.MRP is an order launching system that works well in a discrete environment with very vertical bills of material with defined lead times.

Repetitive manufacturing does not work in discrete lots which makes MRP more difficult to work with it. But, by using phantom bills, we can explode our requirements through the product and use MRP to help us plan our resources.

Capacity Requirements Planning

Most discrete manufacturing processes or job shops are very conscious of the need to match capacities to capabili­ties and create workable plans from this information. Because of variations in routings, this is an area which requires both a combination of infinite capacity planning to determine loads, and finite capacity planning to create the actual plan.

Discrete manufacturing can take advantage of alternate routings to help deal with capacity constraints and possible bottlenecks. Capacity can be increased with overtime and more shifts.

In repetitive manufacturing, the routings cannot be changed, only taken off-line. Rate and mix of demand have a major impact on capacities with major changes not easily accomplished due to equipment dedicated to pre-set levels of production.
Production Activity Control

There are two major systems for controlling the shop floor: job orders and signals. How we manufacture is going to deter­mine which system will work best in our environment.

Where volume is small and variety high, such as in a job shop, a job order fits best for controlling production. Priorities become a major factor, since the various work orders compete for work center capacity. Using work orders can be thought of as a way of reserving the capacity needed at the work centers. In addition, we report back to the system the completion of operations to allow updates and status reports.
Due to the flow nature of repetitive manufacturing, we work better by responding to a signal of need from work center to work center. We need not reserve capacity, nor need we report the completion of individual operations. Instead, we report the completion of an item which can then backflush through the process to charge material and labor.

In a mixed mode environment, both types of control will be found. The ability to produce to work orders and report against them, along with the ability to produce to signals and backflush after the fact, becomes a necessity. A KANBAN signal system for manufacturing can be used while still producing to work orders in anticipation of customer orders for final assembly.

Organizational Change

As we evolve into focused factories and our processes become more sophisticated, planning systems have to be compatible with methods of manufacturing.

Manufacturing planning software needs to be acquired with the ability to accomplish all that we demand from it. The software firm has to be able to advise and train us as to how we can best implement and use it, and then be available for continued support.

For mixed mode manufacturing to be successful, there has to be a change from centralized to a more decentralized planning organization. This is where people empowerment becomes necessary since any attempt to control every aspect of the process over a mix of processes becomes an impossible task.

One method is to empower the workers to build on their knowledge of the product and what it takes to build it. This is done through education and trust that workers have intelligence and know their job better than anyone else.

This is a revolutionary change in thinking that is occurring out of absolute necessity. When you embrace mixed mode, the environment is so dynamic that decentralization may be the only way to accomplish your goals. The days of the central planning organization are giving way to a central­ized management that creates the business plan or strat­egy and then empowers the executors of the plan to make it happen.
Getting There and Staying There

Most companies will adopt whatever manufacturing strat­egies are necessary to meet their goals and needs. Whether mixed mode is in a company's future depends on its market niche, market share, or what is needed internally to manufacture the product. It can be an evolutionary process of change, or be fully embraced and become a revolution. In the long run, the benefits of mixed mode manufacturing are substantial.
The first step is to recognize what you have, then what you need. Make any necessary changes and use them for your continuing success. The concepts discussed can adjust to increases or decreases in either variety or volume over the life of a product. This recognition is the key to success.