Intermittent Flow Processes

This process is very suitable for a large variety of output, each output taking a different route and hence operations, with different time requirements and sequence. In this process the different outputs are called batches or lots. These follow a different processing route through the facilities. Here the production is split into a series of manufacturing stages or operations. Each operation is completed on each one of the single items being made, before the next operation is started. In this way a group of identical products of a batch are made. This process is appropriate for all service organizations like a hospital where the offering is made as per the customer’s demand and follow a different sequence (pathological lab, blood bank, radiography etc).

The characteristics of intermittent form are as follows:

1. It is suitable when the output variety is large and the volumes are low.
2. It is flexible in approach since it uses general purpose machines for a variety of outputs.
3. The transformation process is organized around standard operations in the intermittent form ( e.g. in a bank we have saving accounts counter, current account counter, cash counter, advances and time deposits departments etc). Here each functional group is a specialist group.
4. Material handling here depends upon standard operations, and there is a work in process (WIP) inventory.

Intermittent manufacturing: Under this type of manufacturing, the product is processed in lots rather than on a continuous flow basis. The product design and the machines set up are tailor made to a particular lot production. It is the duty of the works manager or plant engineer to determine the economic manufacturing lot size for each components part, sub-assembly or assembly. Unlike the continuous flow production, the product design and the machine set up changes as the lot changes. Generally, the general purpose machines are used in this type of manufacturing. It is desirable to arrange the machines on the process layout basis rather than on product layout which is more suited to continuous manufacturing.

The problem of production planning and control are relatively more complex as compared to continuous manufacturing. The routing function changes along with they the change in the lot be manufactured. The scheduling function is performed in the light of the jobs on hands, their stage of completion, commitment for completion etc. Unlike continuous manufacturing it is relatively difficult to maintain the balance in the production line. The chances of waiting, rushing, and bottlenecks are more, resulting in either idle capacity or pressure on existing production capacity. The dispatching also becomes a complex function. The job assignment to men and machines necessitates the up to date information about their existing and probable work loads. The investments in the inventories tend to be high due to the maintenance of reservoirs of materials in the sub stores and the prolonged operating cycle. Due to all these factors, the follow up function is difficult as well as inevitable in the intermittent manufacturing.

Job lot manufacturing: Under the intermittent manufacturing system, the production is done for stock or according to a customer’s order. When the manufacturing is carried on according to the specifications of the customer’s order, it is popularly known as “job lot manufacturing”. Here the whole product is looked as one job which is to be completed before going on to the next. The job lot manufacturing signifies that the sales orders from the customers are obtained in advance and then they are translated into manufacturing operations. Generally, the job lot production is undertaken by engineering firms who are manufacturing machines and equipment according to the specification of the customers. The materials are procured on the basis of bills of materials prepared for each order. The cost of each job is ascertained on the basis of job costing. The orders may be of a repetitive or non-repetitive nature. In case of repetitive orders, the tools, patterns, dies etc, are stored and the product design is preserved for reproduction in the future. As repetitive orders ensure certain cost advantages to the manufacturing firm, a part of them are usually passed over to the customers in the form of reduced price for the jobs.