Operation Management - Process choice and Layout planning

Characteristics of project, jobbing, batch, flow, and process production systems, with examples for each.

Project, jobbing, batch, flow and process production are the process types used in manufacturing. The figure below shows the trade off between volume and variety of outputs. In choosing one of these systems, high volume means low variety and high variety means low volume.

(see figure 1)

Project processes - The essence of project processes is that they are all different, so very low volume and very high variety.

The identification of activities and their relationship are uncertain, they can change during the production process itself. Each job has a defined start and finish and the time interval between starting two different jobs is quite long. The resources must be organised exclusively for each project and they are re-allocated after the end of them. Examples of this system are movie production companies: obviously every single movie is different from the others.

Jobbing processes - As for project processes, they deal with high variety and low volume.

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The difference is that the resources are not organised especially for each project, each product has to share them with many others. Although all the products require the same attention, each will differ in its exact needs. Jobbing requires a general purpose layout and highly skilled and versatile workers to interpret drawings and specifications. An example is a painter, who sells his own skill.

Batch processes - With higher volume and lower variety than jobbing process, the essence of these processes is that each time they produce a product, they produce more than one.

The size of the batch can be very small (e.g. two or three), therefore batch process becomes very similar to the jobbing, but usually the batches are large, with repetitive operations. They require careful planning and control to ensure proper use and buffer stocks to "decouple" processes. Finally they typically implies high Work in Progress between work centres. An example could be the production of music instruments.

Flow processes - This kind of process is dedicated to the production of a low variety of product in a high volume. Products are perceived as standard, even if there are superficial differences between them. The process does not have to stop to accommodate differences between products. There are not buffer stocks between processes, that means 'zero' set up time. All workstations must operate to the same cycle time. The classical example is an automobile plant, like every mass operations it is repetitive and predictable.

Processes production - Characterised by very high volume and almost zero variation. Products lend themselves to flow, sometimes they are literally continuous, being produces in an endless flow. They require very high capital investment in equipment. The process is proved before beginning and it usually needs very low manual intervention. An example is the paper making.

LAYOUT PLANNING

Explain the differences between fixed position, product, process, and a cell system layouts, indicating a suitable application for each one.

One of the most obvious characteristics of an operation is deciding where to put all the facilities, machines, materials, staff, etc. This is what layout concerns, the physical location of the transforming resources and the way in which the transformed resources flow through the operation. There are four basic layout types.

Fixed position layout - The process recipient remains stationary and the equipment, machinery, plant and people, instead of the transforming resources, move through it. It happens because the product is too large or delicate to move, or because it could object to being moved. The purpose should be to design so that all of the resources can easily access the point of delivery. There are two types of this layout: forming and treating, in which the nature of the materials changes, and assembly, like a spaceship building.

Process layout - Its characteristic is that processes with similar needs are located together. The reason for this is that the transforming resources dominate the layout decision. Different products and different customers take routes unique to their own needs through the layout. The advantage is that grouping together common processes should increase their utilisation. Other advantages of process layout are high mix and product flexibility, relatively robust in case of disruptions and relatively easy supervision of plant and equipment. Examples are some hospitals departments.

Cell layout - In cell layout the individual processes are moved together to form a cell. The transformed resources entering the operation are preselected to move to one part of the cell in which all the transforming resources to meet their immediate processing needs are located. Transportation costs are reduced, keeping high flexibility and high productivity. Examples could be snack bars in supermarkets.

Product layout - In this case is the convenience of the transformed resources which dominate the operation decision, the opposite of process layout. Everything is arranged around the product's progression through the system. The transformed resources flow along a line of process, following a predetermined route. The advantages of this layout are mainly the low unit cost for high volume and the low staff skill levels needed. An example is a canteen, in which the sequence of customers requirements is generally common for all customers.

As shown in the figure below, volume and variety have different effects on the layout's flow. When volume is very high and variety very low, continuous flow must be the major issue, when variety is very high and volume very low flow should be intermittent.