For high volume, mass or continuous production a line layout is preferred. In this the equipments are laid out according to the sequence of operations that must be performed on the raw material to convert it into the finished product. The sequences of the equipments ad the sequence of the stages through which the raw material progress from the raw material stage to the finished product correspond to each other. Such a Line layout is preferred in most of the assembling operations where a number of components he to be put together to produce the final product. This is called Assembly Line.
Production planning in Mass Production Systems:
In a mass type of production system, such as the assembly lines, the production planning problem basically boils down to (1) establishing the production rates of the final product from the line and (2) obtaining this production rate with the optimal work force level. The assembly line confers social benefits by significantly reducing production and inventory costs by virtue of significantly, the smooth and regulated flow of the material through series of operations at a uniform rate. The more an assembly line resembles a moving conveyor passing through a series of ‘work stations’ at a uniform rate the better are the advantages from such layout. Interrupted flow and delays or stoppages will increase the costs associated with this layout. In fact, the flow rate of the materials trough the entire path of the assembly line (this flow rate being the rate of production of the desired final product) depends on the rate of flow through a bottleneck operation.
If one of the operations takes 10 minutes, whereas all the other operations take less than 10 minutes, then the rate of production of the product will be one unit per 10 minutes. The material on its way through different departments has a wait at various departments, after the job is over, till it can be taken up for the next operation. If we have an operator at each of the work stations, all the work stations (excepting the work station where it takes 10 minutes) will experience idle-time, e.g. the operator manning the operation taking 2 minutes will be idle for (10 – 2) = 8 minutes. The main problem before the assembly line layout is to reduce these idle-times: or, to put it in other words, the problem is to have as much equality of output at each working station as possible. This equalizing of the output rates at different work stations is termed as balancing And hence the term Assembly line Balancing.
Grouping Elemental Tasks:
How can one achieve the balance of an operation that takes 2 minutes, whereas the next operation takes 10 minutes? It can only be achieved by adding some more work at the work station taking 2 minutes and making the total work component more or less equal to 10 minutes. The balancing of the line really means to group the various work elements or elemental tasks involved in production into different work stations in such a way as to have more or less equal working time at each of the work stations.
When this balancing is carried out the product will be produced at the rate of one unit of product per 10 minutes. It is possible that we desire a higher rate of production than this say 12 units of product per hour (the line balanced for 5 minutes). In such a case the elemental tasks which have times less than 5 minutes have to be grouped to form work stations, so that at each work station the total amount of time taken is equal to or less 5 minutes. Of course, the elemental tasks taking more than 5 minutes, such as the one which took 10 minutes need to be share by two operators so that the production rate through that operation does not exceed 5 minutes. So the assembly line work can be grouped or it can be split and then grouped, if necessary.