The layout of a plant or facility is concerned with the physical placement of resources such as equipment and storage facilities, which should be designed to facilitate the efficient flow of customers or materials through the manufacturing or service system. The layout design is very important and should be taken very seriously as it can have a significant impact on the cost and efficiency of an operation and can involve substantial investment in time and money. The decisions taken with regards to the facility layout will have a direct influence on how efficiently workers will be able to carry out their jobs, how much and how fast goods can be produced, how difficult it is to automate a system, and how the system in place would be able to respond to any changes with regards to product or service design, product mix, or demand volume.
In many operations the installation of a new layout, or redesign of an existing layout, can be difficult to change once they are implemented due to the significant investment required on items such as equipment. Therefore, it is imperative to make sure that the policy decisions relating to the organisation, method and work flow are made before the facilities are laid out rather than trying to fit these three into the layout. This is an important area of production and operations management since it is dealing with the capital equipment of the organisation which, in general, is difficult to relocate once it has been put into position.
Plant Layout Crtierias
Keith Lockyer (1992), in his book Production and Operations Management, explained that the plant layout process is rather complex, which cannot be set down with any finality, and one in which experience plays a great part. The author also explained that it is impossible for an organisation to design the perfect layout, however he discussed a number of criteria which should be followed to design a good layout. These criteria are discussed in brief below.
- Maximum Flexibility – A good layout should be designed in such a way that modifications could rapidly take place to meet changing circumstances, and thus should be devised with the possible future needs of the operation in mind.
- Maximum Co-ordination – The layout should be designed in such a way that entry into, and disposal from, any department or functional area should be carried out in the most convenient way to the issuing and recieving departments.
- Maximum use of volume – The facility should be considered as cubic devises and maximum use is to be made of the volume available. This principle is useful in stores, where goods can be stored at considerable heights without causing any inconvenience, especially if certain mordern lifting machinery is available.
- Maximum visibility – Locker further insists that all the workers and materials should be readily observable at all times and that there should be no hidden places into which goods or information might get misplaced and forgotten. Organisations should be careful when they make use of partitioning or screening as these may introduce undesirable segregation which reduces the effective use of floor space.
- Maximum accessibility – The machinery, equipment and other installations should not in any way obstruct the servicing and maintenance points, which should be readily accessible at all times. Obstructing certain service points such as electricity and water mains could hinder the production process in place.
- Minimum distance and Material handling – All movements taking place within the plant should be both necessary and direct. Handling work does add the cost but does not increase the value, thus any unecessary movement should be avoided and if present, eliminated. It is best not to handle the material and information, however if this is necessary it should be reduced to a minimum by making use of appropriate devices.
- Inherent Safety – All processes which might constitute a danger to either the staff or customers should not be accessible to the unauthorised. Fire exists should be clearly marked with uninhibited access and pathways should be clearly defined and uncluttered.
- Unidirectional Flow – All materials which are being used in the production process should always flow in one direction, starting from the storage, passing through all processes and facilities, and finally resulting in the finished product which is later dispatched for storage or sold directly to the customer.
- Management Coordination – Supervision and communication should be assisted by the location of staff and communication equipment in place within the chosen layout.
The Basic Plant Layout Designs
After choosing the process type which will be used within the plant, it would be necessary to select the layout of the operation. Presently, there are four basic types of production layouts, each with their own set of characterisitcs which are briefly discussed below.
1. Fixed Position Layout
A fixed position layout design is used when the product being produced is either too fragile, bulky, or heavy to move and so the conversion process would have to take place at the location where the product is created. In this particular type of layout, all resources and factors of production used to produce a particular product must be moved to the location where the product is to be produced. Scheduling and coordination of the required resources are important characterisitics of this layout, since these resources have to be available on the site where the product is to be produced in the required amounts at the required time. For example, certain activities that are carried out in construction sites are only able to take place after the completion of other activities. The utilization of equipment in such a layout is often low, since it is cheaper to leave equipment idle at a location where it will be used during subsequent days than to move it back and forth.
2. Process Layout
In process layouts, also termed as functional layouts, similar activities are grouped together in departments or work centers according to the process or function that they carry out. This type of layout is characteristic of intermittent operations, service shops, job shops, or batch production, were different customers with different needs are served. Equipment found in this particular layout is often general purpose, and workers are usually trained to make use of equipment in their department. One of the advantagous of this system is flexibility, however a high level of inefficiency takes place. This inefficiency arises since jobs and customers do not flow through the system in an orderly manner, movement from one department to another could take a long time, and queues tend to be developed.
3. Product Layout
In product layouts, which are also known as assembly lines, activities are set up in a line according to the sequence of operations that have to take place in order to produce a particular product. Therefore, each product being produced must have its own ‘line’, which is designed in a unique way to meet its requirements. The flow of work is carried out in an orderly and efficient manner, moving from one particular processing station to the next down the assembly line until the product is successfully produced. These type of layouts are often incorporated for mass production or repetitive operations, where demand is normally stable and volume is high. In such cases, the product being produced is standard, and one which is produced for the general market.
The product or line layout is known to be a very efficient production system because the use of dedicated equipment in a balanced line allows a much throughput time than in any other layout used. However, this particular layout often lacks the flexibility found in the process layout since it only able to produce a standard product or service. Another issue which often concerns manufacturing companies is that if any particular processing station fails, the output from the whole line is lost. Therefore, it lacks the robustness to loss of resources such as equipment failure or staff which are not present at work that the process layout provides.
4. Cellular Layout
A cell layout tries to combine the flexbility found in the process layout together with the efficiency found in the product layout. Machines and activities which are unalike are grouped into work centers, referred to cells, in order to create groups of parts or customers which have similar requirements. The aim of this layout is to arrange different cells in such a way that materials movement is minimized. Through this redesigning, the routing of products has been simplified and products can now be processed in a single cell and need not be transported between different departments.