Meaning of Routing
Routing lays down the flow of work in the plant. It determines what work is to be done and where and how it will be done. Taking from raw material to the finished product, routing decides the path and sequence of operations to be performed on the job from one machine to another. The purpose of Routing is to establish the optimum sequence of operations. Routing in production management is related to considerations of layout, temporary storage of in-process inventory and material handling.
Routing in continuous industries does not present any problem because of the product type of layout, where the equipment is laid as per the sequence of operations required to be performed on the components (from raw material to the finished products). In open job shops, since, every time the job is new, though operation sheets (sometimes) may serve the purpose, but the route sheets will have to be revise and this involves a greater amount of work and expertise.
Various procedural steps of Routing in production management are as follows:
- The finished product is analyzed from the manufacturing standpoint in order to decide how many components can be made in the plant and how many others will be purchased (Make/Buy decision) from outside through vendors, by subcontracting, etc. Make/Buy decision depends upon the work load in the plant, availability of equipment and personnel to manufacture all components, and the economy associated with making all components within the plant itself.
- A parts list and a bill of materials is prepared showing name of the part, quantity, material specifications, amount of materials required, etc. The necessary materials thus can be procured.
- From production standards, machine capacities, machine characteristics and the operations which must be performed at each stage of manufacture are established and listed in proper sequence on an operation and route sheet. The place where these operations will be performed is also decided. Actually, operation sheet and route sheet are separate. An operation sheet shows every thing about the operations, i.e., operation description, their sequence, type of machinery, tools, set up and operation times, whereas a route sheet besides the sequence of operations and relation between operation and machine, also details the section (department) and the machines to whom the work will flow. The difference between an operation sheet and a route sheet is that an operation sheet remains same for the components if the order is repeated but the route sheet may have to be revised if certain machines are already committed to other orders (jobs) on hand. Except this small difference, both the sheets contain practically the same information and thus are generally combined into one sheet known as ‘operation and route sheet’.
- The next step is to determine the lot size or the number of components to be manufactured in one lot or batch. In the case of an order from a particular customer, it is generally equal to a number within 10% of the order quantity. In other cases the principle of economic batch quantity can be applied to determine the batch size.
- Standard scrap factors (single or cumulative) and the places (i.e., after a particular operation or assembly) where scrap is very likely to occur are identified. The actual scrap in each batch can be recorded on the control chart. Causes for points out of control limits are explored and corrected. The variables like workers, machinery and schedules may also be adjusted to minimize scrap.
- The cost of the component is analyzed and estimated through the information obtained in steps (1) to (5) above. The cost consists of material and labor charges, and other specific and general indirect expenses.