AN INTRODUCTION TO PLANT LAYOUT

By Madhu Shankar UndurtyM.Tech, IEM1221311102

Facility Layout Definition• A facility layout is an arrangement of everything needed

for production of goods or delivery of services. A facility is an entity that facilitates the performance of any job. It may be a machine tool, a work centre, a manufacturing cell, a machine shop, a department, a warehouse, etc. (Heragu, 1997).

ProductLayouts

FixedPositionLayouts

Mixed Layouts Process Layouts

Quantity

Number of Different Products

The layout design generally depends on the products variety and the production volumes. Four types of organization are referred to, namely fixed product layout, process layout, product layout and cellular layout (Dilworth, 1996).

Need for Plant layout

• Congestion and bad utilization of space.

• Excessive stock in process at the facility.

• Long distances in the work flow process.

• Simultaneous bottle necks and workstations with idle time

• Qualified workers carrying out too many simple operations.

• Labor anxiety and discomfort. Accidents at the facility.

Difficulty in controlling operations and personnel

Objectives of Plant Layout• The main objective consists of organizing equipment and

working areas in the most efficient way, and at the same time satisfactory and safe for the personnel doing the work.– Sense of Unity

• The feeling of being a unit pursuing the same objective.

– Minimum Movement of people, material and resources.

– Safety• In the movement of materials and personnel work flow.

– Flexibility• In designing the plant layout taking into account the changes over

short and medium terms in the production process and manufacturing volumes.

Objectives of Plant Layout• These main objectives are reached through the attainment of the

following facts:– Congestion reduction.– Elimination of unnecessary occupied areas.– Reduction of administrative and indirect work.– Improvement on control and supervision.– Better adjustment to changing conditions.– Better utilization of the workforce, equipment and services.– Reduction of material handling activities and stock in process.– Reduction on parts and quality risks.– Reduction on health risks and increase on workers safety.– Moral and workers satisfaction increase.– Reduction on delays and manufacturing time, as well as increase in

production capacity.• All these factors will not be reached simultaneosly, so the best solution

will be a balance among them.

Types of Plant Layout• The production process normally determines the type of

plant layout to be applied to the facility:– Fixed position plant layout

• Product stays and resources move to it. – Product oriented plant layout

• Machinery and Materials are placed following the product path.

– Process oriented plant layout (Functional Layout).• Machinery is placed according to what they do and

materials go to them.– Cell Layout

• Hybrid Layout that tries to take advantage of different layouts types.

• Fixed position Layout

Product Oriented LayOut

truckstrucks

Spur of Railroad

• Product oriented plant layout– This type of plant layout is useful when the production

process is organized in a continuous or repetitive way.• Continuous flow: The correct operations flow is

reached through the layout design and the equipment and machinery specifications.

• Repetitive flow (assembly line): The correct operations flow will be based in a line balancing exercise, in order to avoid problems generated by bottle necks.

– The plant layout will be based in allocating a machine as close as possible to the next one in line, in the correct sequence to manufacture the product.

• Process oriented plant layout (Functional Layout)– This type of plant layout is useful when the production process is

organized in batches.– Personnel and equipment to perform the same function are

allocated in the same area.– The different items have to move from one area to another one,

according to the sequence of operations previously established.– The variety of products to produce will lead to a diversity of flows

through the facility.– The variations in the production volumes from one period to the

next one (short periods of time) may lead to modifications in the manufactured quantities as well as the types of products to be produced.

Cellular Layout

Process (Functional) Layout

Group (Cellular) Layout

Similar resources placed together

Resources to produce similar products placed together

T T T

MM M T

M

SG CG CG

SG

D D D

D

T T T CG CG

T T T SG SG

M M D D D

M M D D D

A cluster or cell

• Work cells– Definition:

• Group of equipment and workers that perform a sequence of operations over multiple units of an item or family of items.

– Looks for the advantages of product and process layouts:• Product oriented layout: Efficiency• Process oriented layout: Flexibility

– Group Technology• Grouping outputs with the same characteristics to

families, and assigning groups of machines and workers for the production of each family.

Layout Design Process

• Formulate the design problem

• Process oriented plant layout– Working area space.

» Static area (Se): Physical space for equipment and workstations.

» Gravitation area (Sg): Allocation of tools and materials. Area where operators develop their work.

» Evolution area (Sv): Space to allow operators and material movements.

St=Se+Sg+SvSg=Se*n Sv=(Se+Sg)*k

n=number of accessible sides k=industry coefficient (0,05-3)

• Analysing the Design Problem

• Process oriented plant layout– Analysis

• Information gathering– When the objective is the reduction of material handling costs,

we can solve the problem in quantitative terms:» Traffic intensity matrix: Number of material handling moves

among departments (information provided by historical data, route sheets and production plans).

» Distance matrix: Distances among areas at the plant and places where the different working areas could be allocated.

» Cost matrix: Cost of material transportation.- It depends on the type of equipment to be used.

• Process oriented plant layout– Analysis

• Quantitative criteria: Transportation costs.– With the information gathered in the previous 3 matrixes, the

objective is to minimize the transportation costs.– Total Transportation Cost:

– Objective: Finding the combination of dij that minimizes TTC.– This formula is complicated for common cases, due to the

number of different possibilities (i.e.- for 10 sections, the alternatives would be 3,628,000).

TTC= ΣΣ tij dij cij

• Searching for alternative layout designs

• Evaluating the alternative designs

• Selecting the preferred design

• Specifying the layout design to be installed

Layout Design Cycle

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