Intermittent and continuous manufacturing are the mutually exclusive activities. The following comparison will clarify their true nature of operations:
The typical processing industries are bulk drugs plants, fertilizer plants, petrochemical plants and milk dairies which have highly automated system and sophisticated controls. They are not labor-intensive and the worker is just an operator to monitor the system, and take corrective steps if called for. They are continuous process industries. In these industries a single input is processed generally to give one or more different products (e.g. petroleum refinery gives from petroleum several products like diesel, petrol, kerosene, furnace oil, naphtha etc). Processing industries are thus following analytical processes. In discrete manufacturing, continuous flow processing however uses synthetic processes. Here the plant installation also- is more complex to begin with.
In this process, similar items needed in large volumes are produced. The process is divided into appropriate stages. Orders are processed stage by stage. Next stage is set when the first is completed. At each stage, the capacity is used and reused. Printing is an example of batch processing. The essential feature of batch production is to stop the first process and reset the whole thing to produce another product or provide another service.
Selection of the Process
In practice, the process forms (project, intermittent continuous flow, and continuous process) are not observed in pure extreme forms. More of these are combined to get different components and the final product. In auto industries the components are made by the intermittent form, and the vehicle is assembled on a continuous basis. Group Technology and FMS (flexible manufacturing system) referred to already are in fact attempts to combine the features of these forms.
Traditionally, services were offered on intermittent basis. However, services of an architect or a solicitor may be on project basis. In some countries, surgeries of certain natures like heart by-pass surgeries or eye surgeries have been so standardized have so standardized that they can be given on continuous basis. Here the patient is passing along a health care line, where each surgeon performs a small task.
Product and process life cycles are related. Something may be started in an unorganized way on project basis. Soon there is batch production. Later in the growth phase, more and more sub-processes come into operation, thus resulting in adoption of continuous phase. Even in the maturity phase, it is better to use continuous form. Here the fixed costs of operations are high but per unit cost of output is low.
The whole thing is evolutionary — the process evolves with the market and the output. While choosing the process form, the organization also takes into account its distinctive competence which ultimately decides its focus in operations. Process is crucial ingredient of this focus.