When viewed from a different context, the operations/ production system can be equated with the flow of materials — flow into, flow through and flow out of the conversion process. When we analyze the characteristics of this flow, we find in some systems it to be very smooth, whereas in others it is much more complex. The more difficult the materials flow, the more complex is the system to manage. Depending on the flow characteristics, there are four classes of the production system.
1. Mass production or flow â€“ line production system.
2. Batch production system.
3. Job shop.
4. Projects (unit manufacture)
Problems confronting a production man are relevant with reference to a particular system. Problems which are critical for mass production may not be that
important for batch production. Thus the system determines our focus of attention.
Mass Production system or Flow-Line production Systems:
In these systems, the flow is in a straight line. All facilities are arranged as per the sequence of operations. Output of one operation becomes the input for the subsequent operation. The system is cascaded. Some peculiar problems of this system are balancing of assembly line/production function. Maintenance must be very good to prevent the breakdown of the whole system. Raw material fed initially is very important since all the operations depend upon it. Balanced workload results in a smooth output rate.
Batch Production System:
In this system, a batch consisting of a certain quantity is made on a machine. The same machine then may be used for another product. Thus here there are a variety of products; and it is not possible to maintain a separate assembly line for each product. Products compete for the share of the machine. Machines are general purpose. Pharmaceutical companies make medicinal formulations by batch production system. Production problems are complex here. There is machine assignment problem. Again, what should be the size of each batch is another problem. Scheduling becomes more complex. Production planning, in response to demand, becomes challenging. Layout of the system also merits attention.
Here, the shop accepts customerâ€™s orders and executes them. It does not have its own product mix. Primarily, we have facilities and processes in a job shop to undertake a wide variety of customer jobs in different batch quantities. Each order may be unique — requiring its own planning and tooling. Here the flow of material is also complex. A busy job shop is a difficult system to plan and control. There is need to priorities different jobs for dispatching to customers. At times, short-processing-time (SPT) becomes the yardstick to sequence the different jobs. Job shop is technically speaking a queuing problem. Simulation techniques do help in analyzing it.
Consider the manufacturing of a ship. Such products are never made in large numbers. Manpower, facilities and other resources center around such products. Each such product can therefore be treated as a project, requiring sequencing of certain activities either in series or concurrently. PERT/CPM or network analysis is a useful technique to plan and control such projects.