MAIN SYSTEMS OF PLANT LAY OUT
Types of Layouts
Depending on the nature of product and the type of manufacturing (low volume versus high volume, product mix etc.) being performed, plant layouts are categorized as follows:
Static Product
Static Product plant layouts are used when the product to be made is large and bulky. In such cases, the product is manufactured or assembled at a fixed location and machinery is moved around the product as needed. Examples of such layouts are found in aircraft manufacture, shipbuilding yards etc. The manufacture of such products is controlled on a project basis and the location of machinery changes as the project evolves.
Advantages
1. Material movement is reduced.
2. Promotes job enlargement by allowing individuals or teams to perform the “whole job”.
3. Continuity of operations and responsibility results from team.
4. Highly flexible; can accommodate changes in product design, product mix, and product volume.
5. Independence of production centers allowing scheduling to achieve minimum total production time.
Limitations
1. Increased movement of personnel and equipment.
2. Equipment duplication may occur.
3. Higher skill requirements for personnel.
4. General supervision required.
5. Cumbersome and costly positioning of material and machinery
6. Low equipment utilization.
Product or Production Line Layout
Product layouts are used when a single or a closely related set of products is to be manufactured in high volumes. Machines/workstations are arranged in a manufacturing/assembly line. The order of machines in the line follows the order in which processing is to be performed. Prior to the design of such a layout, an assembly line balancing problem is often solved or determines the best set of tasks/activities that should be performed at each station.
The layout corresponding to the sequence of operations, results in smooth and logical flow lines.
2. Work from one process is fed directly into the next, resulting in small in-process inventories.
3. Total production time per unit is short.
4. Material handling is reduced since the machines are located so as to minimize distances between consecutive operations.
5. Operators at the production line usually require lesser skill; hence, training is simple, short, and inexpensive.
6. Simple production planning control systems are possible.
Less space is occupied by work in transit and for temporary storage.
Group incentives possible
Group or Cellular Layout
Group layouts are used when a family of components is to be manufactured by a small manufacturing cell. In this arrangement, a cluster of machines forms a cell. Each cell has it's own material handling system, typically a robot or a conveyor system. If at all possible, a component part is completely processed in a single machine cell. Components are then routed to assembly areas.
Advantages
Increased machine utilization.
Tends to team attitude and job enlargement.
Compromise between product layout and process layout, with associated advantages.
Supports the use of general purpose equipment.
Shorter travel distances and smoother flow lines than for process layout.
Process Layout
Process Layouts group machines, which perform similar activities into processing departments. Thus, in a plant with a process layout, there may be a turning department (all lathes), a milling department, a grinding department etc. Such layouts are common in older plants and in job-shops. They require a large amount of material handling as parts move between departments for various operations. They have the advantage that, the workers and supervisors can specialize in their process
Advantages
Better machine utilization can be achieved; consequently, fewer machines are required.
A high degree of flexibility exists in equipment or man power allocation for specific tasks.
Uses general purpose machines. Hence comparatively lower investment in machines is required.
The diversity of tasks offers a more interesting and satisfying occupation for the operator.
Specialized supervision is possible.
Breakdowns of machines can be tolerated
Individual bonus / incentive schemes possible
Systematic Layout Planning (Muther)
* Quantify Flow of material between departments
* Create Activity Relationship Chart
* Create Relationship Diagram
* Determine Space Requirements
* Create Space Relationship Chart
* Create Alternate Layouts
1. Measuring Flow
As a first step we must determine the amount of material flow between different departments. The data required for this can be obtained from production and engineering documents. Typical documents, which can provide data on component movement through the plant, include:
* Bill of Materials
* Route Chart
* Assembly/Operations Process Chart
* Precedence Diagrams
Data on production volumes can be obtained from forecasted production. Combining the process data with the production volume data it is possible to determine the amount of material that flows between workstations/departments.
2 From-To Charts
To represent the amount of flow between departments a from-to matrix is employed. The from-to matrix is a square matrix with the number of rows (columns) equal to the number of departments / workstations in the problem. The (i,j) th entry in the matrix represents the amount of material flow from department i to department j
3REL ChartThe REL Chart can be used to determine the adjacency between departments. If material flow is an important consideration or if common supervisory control is important then a high rating between two departments suggests that these departments should be geographically close to each other. The shape and size of the departments limits the number of departments, which can be adjacent to one another. One of the first steps in developing a layout is to determine the adjacency between different departments.
The REL chart represents the importance of adjacency between departments using a six-level rating scheme as follows:
A Absolutely necessary
E Especially important
I Important
O Ordinary Importance
U Unimportant
X Undesirable
It is up to the analyst to determine the exact rating to be assigned to a pair of activities
Depending on the nature of product and the type of manufacturing (low volume versus high volume, product mix etc.) being performed, plant layouts are categorized as follows:
Static Product
Static Product plant layouts are used when the product to be made is large and bulky. In such cases, the product is manufactured or assembled at a fixed location and machinery is moved around the product as needed. Examples of such layouts are found in aircraft manufacture, shipbuilding yards etc. The manufacture of such products is controlled on a project basis and the location of machinery changes as the project evolves.
Advantages
1. Material movement is reduced.
2. Promotes job enlargement by allowing individuals or teams to perform the “whole job”.
3. Continuity of operations and responsibility results from team.
4. Highly flexible; can accommodate changes in product design, product mix, and product volume.
5. Independence of production centers allowing scheduling to achieve minimum total production time.
Limitations
1. Increased movement of personnel and equipment.
2. Equipment duplication may occur.
3. Higher skill requirements for personnel.
4. General supervision required.
5. Cumbersome and costly positioning of material and machinery
6. Low equipment utilization.
Product or Production Line Layout
Product layouts are used when a single or a closely related set of products is to be manufactured in high volumes. Machines/workstations are arranged in a manufacturing/assembly line. The order of machines in the line follows the order in which processing is to be performed. Prior to the design of such a layout, an assembly line balancing problem is often solved or determines the best set of tasks/activities that should be performed at each station.
The layout corresponding to the sequence of operations, results in smooth and logical flow lines.
2. Work from one process is fed directly into the next, resulting in small in-process inventories.
3. Total production time per unit is short.
4. Material handling is reduced since the machines are located so as to minimize distances between consecutive operations.
5. Operators at the production line usually require lesser skill; hence, training is simple, short, and inexpensive.
6. Simple production planning control systems are possible.
Less space is occupied by work in transit and for temporary storage.
Group incentives possible
Group or Cellular Layout
Group layouts are used when a family of components is to be manufactured by a small manufacturing cell. In this arrangement, a cluster of machines forms a cell. Each cell has it's own material handling system, typically a robot or a conveyor system. If at all possible, a component part is completely processed in a single machine cell. Components are then routed to assembly areas.
Advantages
Increased machine utilization.
Tends to team attitude and job enlargement.
Compromise between product layout and process layout, with associated advantages.
Supports the use of general purpose equipment.
Shorter travel distances and smoother flow lines than for process layout.
Process Layout
Process Layouts group machines, which perform similar activities into processing departments. Thus, in a plant with a process layout, there may be a turning department (all lathes), a milling department, a grinding department etc. Such layouts are common in older plants and in job-shops. They require a large amount of material handling as parts move between departments for various operations. They have the advantage that, the workers and supervisors can specialize in their process
Advantages
Better machine utilization can be achieved; consequently, fewer machines are required.
A high degree of flexibility exists in equipment or man power allocation for specific tasks.
Uses general purpose machines. Hence comparatively lower investment in machines is required.
The diversity of tasks offers a more interesting and satisfying occupation for the operator.
Specialized supervision is possible.
Breakdowns of machines can be tolerated
Individual bonus / incentive schemes possible
Systematic Layout Planning (Muther)
* Quantify Flow of material between departments
* Create Activity Relationship Chart
* Create Relationship Diagram
* Determine Space Requirements
* Create Space Relationship Chart
* Create Alternate Layouts
1. Measuring Flow
As a first step we must determine the amount of material flow between different departments. The data required for this can be obtained from production and engineering documents. Typical documents, which can provide data on component movement through the plant, include:
* Bill of Materials
* Route Chart
* Assembly/Operations Process Chart
* Precedence Diagrams
Data on production volumes can be obtained from forecasted production. Combining the process data with the production volume data it is possible to determine the amount of material that flows between workstations/departments.
2 From-To Charts
To represent the amount of flow between departments a from-to matrix is employed. The from-to matrix is a square matrix with the number of rows (columns) equal to the number of departments / workstations in the problem. The (i,j) th entry in the matrix represents the amount of material flow from department i to department j
3REL ChartThe REL Chart can be used to determine the adjacency between departments. If material flow is an important consideration or if common supervisory control is important then a high rating between two departments suggests that these departments should be geographically close to each other. The shape and size of the departments limits the number of departments, which can be adjacent to one another. One of the first steps in developing a layout is to determine the adjacency between different departments.
The REL chart represents the importance of adjacency between departments using a six-level rating scheme as follows:
A Absolutely necessary
E Especially important
I Important
O Ordinary Importance
U Unimportant
X Undesirable
It is up to the analyst to determine the exact rating to be assigned to a pair of activities
