FACTORY LAYOUT PRINCIPLES
Mark Allington, December 2006
This note is intended to provide guidance on laying out machines in a factory, based upon decisions about the type of manufacturing process to be accommodated.
Laying out a factory involves deciding where to put all the facilities, machines, equipment and staff in the manufacturing operation.
Layout determines the way in which materials and other inputs (like people and information) flow through the operation. Relatively small changes in the position of a machine in a factory can affect the flow of materials considerably. This in turn can affect the costs and effectiveness of the overall manufacturing operation. Getting it wrong can lead to inefficiency, inflexibility, large volumes of inventory and work in progress, high costs and unhappy customers. Changing a layout can be expensive and difficult, so it is best to get it right first time.
The first decision is to determine the type of manufacturing operation that must be accommodated. This depends on product volume and variety. At one extreme, the factory will produce a wide variety of bespoke products in small volumes, each of which is different (this is called a ‘jobbing’ operation). At the other extreme it will produce a continuous stream of identical products in large volumes. Between the extremes, the factory might produce various sized batches of a range of different products.
BASIC LAYOUT TYPES
Once the type of operation has been selected (jobbing, batch or continuous) the basic layout type needs to be selected. There are three basic types:
• Process layout
• Cell layout
• Product layout
Jobbing operations (high variety/low volume) tend to adopt a process layout. Batch operations (medium variety and volume) adopt either a cell or process layout. Continuous operations (low variety/high volume) adopt a product layout.
1. Process layout
In process layout, similar manufacturing processes (cutting, drilling, wiring, etc.) are located together to improve utilisation. Different products may require different processes so material flow patterns can be complex.
An example is machining parts for aircraft engines. Some processes (such as heat treatment) need specialist support (e.g. fume extraction), while other processes (e.g. machining centres) need technical support from machine setters/operators. So the factory will be arranged with heat treatment together in one location and machining centres in another. Different products will follow different routes around the factory.
2. Cell layout
In cell layout, the materials and information entering the operation are pre-selected to move to one part of the operation (or cell) in which all the machines to process these resources are located. After being processed in the cell, the part-finished products may go on to another cell. In effect the cell layout brings some order to the complexity of flow that characterises process layout.
An example is specialist computer component manufacture. The processing and assembly of some types of computer components may need a dedicated cell for manufacturing parts to the quality requirements of a particular customer.
3. Product layout
Product layout involves locating the machines and equipment so that each product follows a pre-arranged route through a series of processes. The products flow along a line of processes, which is clear, predictable and relatively easy to control.
An example is automobile assembly, where almost all variants of the same model require the same sequence of processes.
Another is paper making. Although different types of paper can be manufactured, all types have the same processing requirements. First the wood chips are combined with chemicals, water and steam in the ‘cooking’ process to form pulp. The pulp is then put together through a cleaning process before being refined to help the fibres lock together. The...
Bibliography: Apple J M (1977) Plant layout and materials handling, John Wiley
Slack N et al (1998) Operations Management, Prentice Hall
Wu, B (1994) Manufacturing facilities – location planning and design, PWS-Kent
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