In Intermittent manufacturing systems, the goods are manufactured specially to fulfill orders made by customers rather than for stock. Here the flow of material is intermittent. Intermittent production systems are those where the production facilities are flexible enough to handle a wide variety of products and sizes. These can be used to manufacture those products where the basic nature of inputs changes with the change in the design of the product and the production process requires continuous adjustments. Considerable storage between operation is required, so that individual operations can be carried out independently for further utilization of men and machines. Examples of intermittent systems are: machine shops, hospitals, general office etc.
Characteristics of intermittent manufacturing systems are:
- Most products are produced in small quantities.
- Machines and equipment are laid out by process.
- Workloads are generally unbalanced.
- Highly skilled operators are required for efficient use of machines and equipment.
- In-process inventory is large.
- Flexible to suit production varieties.
Under intermittent 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.
Planning and Control Mechanism for Intermittent Manufacturing Systems
Organization of production planning and control operations in intermittent manufacturing systems needs estimation of jobs, routing, scheduling, preparation of manufacturing orders, dispatching and production control. Here customer provides the blue print and other specification regarding the product to be manufactured. Then the organization formulates their production strategy to suit the needs of the customer.
- This type of manufacturing system covers specialties of every type and sub assemblies or parts which are required to manufacture the product. Due to this there is continuous planning at each fresh order.
- Due to variety of orders and different lot sizes, the system needs wise and careful sequencing of operations which makes routing and scheduling operations elaborate and complex.
- Proper regulation and close inspection is required at different stages of production.
- Storage facilities are to be provided at each operational stage.
So the job of stock control of raw materials, semi-finished goods and finished goods should be entrusted to competent personnel, who can regulate the operations and flow of material smoothly. Intermittent production systems can be further classified into three categories, namely;
- Project production: Project production where a single assignment of complex nature is undertaken for completion within the given period and within the estimated expenditure.
- Job production: Jobbing production where one or few units of a product are produced to customer’s requirement within the given date amid within the price fixed prior to the contract.
- Batch production: Batch production where limited quantity of each type of product is authorized for manufacture at a time.
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.