PLANT LAYOUT
DEFINITION
Plant Layout is defined as, “A technique of locating machines, processes and plant services within the factory in order to secure greater possible output of high quality at the lowest possible total cost of production.”
Plant layout provides a broad framework within which production and all other activities have to take place. All facilities like equipment, raw-materials, machinery, tools, fixtures, finished goods, in-process inventories, workers and even scrap and waste etc., are given a proper place in the layout. The design of plant layout is a strategic decision and the analysis and planning of a sound plant layout is very important.
OBJECTIVES OF GOOD PLANT LAYOUT
Some of the important objectives of a good plant layout are:
1) Overall simplification of production process in terms of equipment utilization, minimization of delays, reducing manufacturing time and better provisions for maintenance.
2) Overall integration of man, materials, machinery supporting activities and other considerations in a way that results in the best compromise.
3) Minimization of material handling time and cost by suitably placing the facilities in the best flow sequence.
4) Effective space utilization.
5) Reduced inventory-in-process and easy availability of materials for assembly.
6) Better supervision and control.
7) Worker satisfaction and reduction fatigue.
8) Better working environment and present look to create the same.
9) Minimization of waste and higher productivity.
10) Avoid unnecessary capital investment.
11) Higher flexibility and adaptability to changing conditions.
DETERMINANTS OF LAYOUT
The following factors should be taken into consideration while determining the layout for a factory.
1) Type of Product
The type of product to be produced affects the layout strongly. The layout depends on whether the products are goods or services. If they are goods, then whether they are small or light, heavy or bulky or fragile. Layout designs depend on product designs and quality standards to be maintained as well. Product layout is preferred for one or a few standardized products whereas process layouts are useful for producing a large variety of non standardized products.
2) Type of Production Process
This relates chiefly to the production technology used and the type of materials handled. The type of production system i.e., continuous production, job production, process production and on largely governs the type of plant layout.
3) Volume of Production
The plant layout in a large scale organization will be different from the same in the small scale manufacturing industry especially with respect to material handling equipment, space utilization, communication, etc.
4) Management Policy
A layout can often reflect the policy of the management. It is the Management, within its cost constraints, which has to decide on many matters like nature and quality of products, size of the plant, plans for expansion, storage facilities, employee facilities etc.
5) Service Facilities
The layout of Factory must include proper service facilities required for the comfort and welfare of workers. These include canteen, lockers, gardens, parking area, drinking water, first aid etc.
6) Possibility of Future Expansion
The type of layout depends upon the possibility of future expansion and installation of additional facilities.
TYPES OF LAYOUTS
Plant Layouts can be classified as four basic types. But most of the practical layouts are a suitable combination of these basic types to match the requirements of activities and flow for a particular organization.
The basic types are:
1) Product or Line Layout.
2) Process Layout or Functional Layout or Job Shop Layout.
3) Cellular or Group Layout.
4) Fixed Position Layout.
Product or Line Layout
In this type of layout, only one product, or one type of product is produced in a given area. A product layout is one where work centers and equipment are arranged in a sequence such that the raw material enters at one end of the line and goes from one work centre to the next rapidly in the smooth flow and the finished product is delivered at the other end of the line. In this, each unit of output requires the same sequence of operations from beginning to end.
Eg: Automobile assembly lines, Beverage bottling, Cafeteria, Automatic car washing etc.
Product layouts are suitable for continuous production and are adopted by those organizations which produce a few products in large volume.
A line layout or product layout can be adopted on conditions that
i) Product is standardized.
ii) There is a reasonably stable product demand.
iii) There is a continuous supply of raw material.
iv) There is no breakdown of machinery or absenteeism of key personnel.
Disadvantages:
1) Lack of Flexibility - any change in product requires the modification of layout.
2) Sequence of operation is disturbed if there is any problem at any of the work centers.
3) Capital investment is high.
4) Absence of labor at any of the work centers stops production.
Process Layout or Job Shop Layout
In this type of layout, similar equipments and operations are grouped together to perform similar work in each area. Process layouts are widely used both in manufacturing and other service facilities especially in job and batch production, and non-repetitive type of work. It is employed when designs are not stable and volume of production is small. The path of flow of raw materials through the various sections varies from one product to another. Usually the paths are long and there will be possibility of backtracking.
Eg: Job shops, Hospital, Universities, Large Officers, Paper mills, Cement industries, Chemical industries etc.
Advantages of process layout:
1) It allows variety of products can be made on the same equipment.
2) The equipment is general purpose and less expensive than equipment used in product layouts.
3) The operations can continue, if some equipment is unavailable because of breakdown or planned maintenance.
4) It is suitable for low volume variable demand.
5) Products can be made for specific orders.
Disadvantages of process layout:
1) Scheduling work on equipment is complicated and must be done continuously.
2) High levels of operator skills are needed.
3) Large amount of work-in-progress, more waiting for next operation.
4) Higher total production time.
5) Multiple handling of materials leads to higher materials handling cost.
6) Effective and quick supervision is difficult.
7) Large floor space is required.
8) Rate of production is low. Not feasible to incorporate automation.
Cellular or Group Layout
This is a combination of product and process type of layouts. In this type the area is divided into several cells. Each cell has a few different equipment or facilities so that a 'family' of parts which require similar processing can be produced in each cell. Each member of this 'family' of parts is made complete in this small specialized area with all the necessary machining sequences. Families of parts come together later in another cell for assembly.
This layout is called Group layout since Group Technology is used. Group Technology (GT) is the analysis and comparison of components so as to group them into families with similar characteristics. GT is used to develop a hybrid between pure process layout and pure product layout. This technique is very useful for companies that produce variety of parts in small batches. Each batch can be processed in each cell taking the advantage of a flow line. The application of Group Technology involves two basic steps. The first step is to determine component families or groups. The second step is to arrange equipment used to process a particular family of components. This is similar to having small plants within the plant.
Advantages of Cellular Layout:
1) Reduced material handling cost.
2) Less work-in-process Inventory.
3) Simplified Production Planning and Control.
4) Better Utilization and Specialization of labor.
5) Rate of production is high. Feasible to incorporate automation in each cell.
6) Product variety can be higher than line layout but lesser than process layout.
7) Suitable for incentive Pay Scheme.
8) Delivery times can be estimated more precisely.
Disadvantages:
1) Increased machine down time since machines dedicated to a particular cell may not be used all the time.
2) Cells having a particular combination of facilities may become out-of-date as products and processes change.
Fixed Position Layout
In this type of layout, the product stays in one location while tools, equipments and workers are brought near it and fabrication is carried out. A fixed position layout is appropriate when it is not feasible to move the product because of its size. This type of layout is suitable,
1) when one or few pieces of identical heavy products are to be manufactured
2) when the assembly consists of large number of heavy parts
3) when the cost of transportation of the products being processed are higher than the cost of movement of tools and equipments
Eg: Ship building, building of bridges, agricultural operations, satellite erection, etc.,
Advantages of Fixed Position Layout:
1) Capital investment is lower in the layout.
2) Flexibility to changes in product design.
3) Responsibility for quality can be pin-pointed.
4) Helps in job enlargement and upgrades the skills of the Operator.
5) The workers identify themselves with the product and take extra interest and pride in doing the job.
Disadvantages:
1) Equipment needed for fabrication may not be mobile
2) Work may suffer due to climatic conditions.
LINE BALANCING IN ASSEMBLY LINE
It is an important method of minimizing costs in product or line layout. As we already know, a line layout is one where work centers are arranged in a sequence such that raw material enters at one end of the line and goes from one work centre to the next and the finished product is delivered at the other end of the line.
Although the product layout produces a large volume of goods in a relatively short time, once the line is established there are numerous problems that arise in connection with this type of layout that do not become important in the process layout. One of these complex problems is the problem of line balancing, which might be considered the problem of balancing operations or stations in terms of equal times and times required to meet the desired rate of production. In practical cases, perfect balance is achieved in straight line layouts.
The problem in line balancing is minimizing the idle time on the line for all combinations of workstations subject to certain restrictions. An important restriction is the production volume that is to be produced. If the demands for the product change, then there should be a change in line balancing. Usually an assembly line is used for a variety of products; it becomes necessary to consider a fixed number of workstations.
In general, there are two types of line-balancing situations, each of which involves different considerations. It is sometimes difficult in practical cases to distinguish between the two categories, but it is useful to consider the line balancing problem as: (1) assembly-line balancing and (2) fabrication-line balancing. The distinction refers to the type of operations taking place on the line to be balanced. The term "assembly line" has gained a certain popular interpretation as it is used with reference to the automotive industry. The term "fabrication line", on the other hand, implies a production line made up of operations that form or change the physical or chemical characteristics of the product involved. Machining operations would fit into this classification, as would heat-treat operations.
DESIGN OF MATERIAL HANDLING SYSTEM
Materials handling systems are closely integrated with a plant layout. Many different combinations of equipment could be used to achieve this purpose. In order to move materials at minimum cost the alternative equipment and materials handling system must be carefully evaluated before installation. In addition, the systems that are installed must be reviewed periodically to ensure that it continues to be as effective as possible.
The rapid changes in materials handling technology can make an existing approach obsolete and non-competitive. An increase in production delays by lower machine utilization and greater idle labor time or rise in material breakage or spoilage rates are danger signals.' Such inefficient practices and transferring materials from one container to another can be a major handling problem.
A check list of factors to consider during an audit or in the initial design of a material handling system has been developed. It is the result of considerable experimentation and experience and may serve, as a rough guide in analyzing a materials handling problem; however
• Eliminate all handling as for as possible,
• Maintain a simple line of flow,
• Maintain a steady rate of material flow,
• Mechanized handling wherever economically feasible,
• Accommodate the largest workload possible,
• Minimize travel distance,
• Use flexible equipment wherever possible.
The initial step in the design of a materials handling system is to determine what material must be transported. This may be accomplished by preparing a list of all end products, sub-assemblies, components and raw materials, involved in the production process. When will be the move take place and how much will be moved? To determine this production forecast for end product must be extended until it is possible to estimate the total amount of sub-assemblies, components and raw materials that must be moved. Then the average daily movement required to meet production forecast is determined.
