Plant layout

Department of
Mechanical Engineering
Dr Gaurang Joshi
Unit no 2
Product / Process
Planning and Design
CAPM (01ME0721 )

Facility Layout
 Layout refers to the configuration of departments, work centers,
and equipment, with particular emphasis on movement of work
(customers or materials) through the system.
 Layout decisions are important for three basic reasons:
1. require substantial investments of money and effort;
2. involve long-term commitments, which makes mistakes difficult
to overcome; and
3. have a significant impact on the cost and efficiency of
operations

Factors affecting Plant
Layout
1. Plant location and building
2. Nature of Product
3. Type of Industry
4. Plant Environment
5. Spatial Requirements
6. Repairs and Maintenance
7. Balance
8. Management Policy
9. Human Needs
10. Types of machinery and equipment

Factors affecting Plant
Layout
 The basic objective of layout design is to facilitate a smooth flow of
work, material, and information through the system. Supporting
objectives generally involve the following:
 To facilitate attainment of product or service quality.
 To use workers and space efficiently.
 To avoid bottlenecks.
 To minimize material handling costs.
 To eliminate unnecessary movements of workers or materials.
 To minimize production time or customer service time.
 To design for safety.

Plant Layout : Types
 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.
• Combined Layout
 Combine aspects of both process and product layouts

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.

Product Layouts
Product layouts are used to achieve a smooth and rapid flow of large
volumes of goods or customers through a system.

Product Layouts
Disadvantages
 Morale problems and to
repetitive stress injuries.
 Lack of maintaining
equipment or quality of
output.
 Iinflexible for output or
design
 highly susceptible to
shutdowns
 A high utilization of labor and
equipment
 Preventive maintenance, the
capacity for quick repairs, and
spare-parts inventories are
necessary expenses
 Incentive plans tied to
individual output are
impractical
Advantages
 A high rate of output
 Low unit cost due to high
volume
 Labor specialization
 Low material-handling cost
per unit
 A high utilization of labor and
equipment
 The establishment of routing
and scheduling in the initial
design of the system
 Fairly routine accounting,
purchasing, and inventory
control

Process Layouts
 Process layouts are designed to process items or provide services that
involve a variety of processing requirements.

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.

Process Layout
Advantages
 Handle a variety of processing
requirements
 Not vulnerable to equipment
failures
 General-purpose equipment is less
costly and is easier and less costly
to maintain
 Possible to use individual incentive
systems
Disadvantages
 In-process inventory costs can be
high
 Routing and scheduling pose
continual challenges
 Equipment utilization rates are low
 Material handling is slow and
inefficient, and more costly per unit
 Job complexities reduce the span of
supervision and result higher
supervisory costs
 Special attention necessary for each
product or customer and low
volumes result in higher unit costs
 Accounting, inventory control, and
purchasing are much more involved

Fixed-Position Layouts
 In fixed-position layouts, the item being worked on remains
stationary, and workers, materials, and equipment are moved
about as needed.
 Fixed-position layouts are widely used in farming, firefighting, road
building, home building, remodeling and repair, and drilling for oil.
In each case, compelling reasons bring workers, materials, and
equipment to the “product’s” location instead of the other way
around.

Ship Building yard

Advantages
 Saves time and cost in
movement
 Flexible as changes in job
design can be easily
incorporated
 More economical when
several orders in different
stages are executed
 Adjustments can be made to
meet shortage of materials or
absence of workers.
Disadvantages
• Production period being very
long, capital investment is
quite heavy
• Very large space is required
for storage of materials and
equipment
• As several operations are
carried simultaneously,
possibility of confusion and
conflicts are high

Combination Layouts
 Supermarket layouts are essentially process layouts, yet we find
that most use fixed-path material-handling devices such as roller-
type conveyors in the stockroom and belt-type conveyors at the
cash registers.
 Hospitals also use the basic process arrangement, although
frequently patient care involves more of a fixed-position approach,
in which nurses, doctors, medicines, and special equipment are
brought to the patient.
 Faulty parts made in a product layout may require off-line
reworking, which involves customized processing. Moreover,
conveyors are frequently observed in both farming and
construction activities.
 Cellular manufacturing - Group technology
 Flexible manufacturing systems

Essentials of Ideal Layout
1. Principle of minimum movement
2. Principle of flow
3. Principle of space
4. Principle of safety
5. Principle of flexibility
6. Principle of interdependence
7. Principle of overall integration
8. Principle of minimum investment

Computerized Relative
Allocation of Facilities
Technique (CRAFT)/
or
Computerized technique
for relative allocation of
facility
Computerized Relative Allocation of Facilities Technique (CRAFT) is a
tool that used to help improve the existing layout of the facilities.
The facility is improved by swaping two or more departments to help
arrange the facility to an optimal floor plan
1. CRAFT is more popular than the other computer based layout
procedures.
2. It is improvement algorithm & starts with an initial layout &
proceeds to improve the layout by interchanging the
department’s pair wise to reduce the total material
transportation cost.
3. It does not give the Optimal Layout; but the results are good &
near optimal, which can be later corrected to suit the need of
the layout planner.

Features of CRAFT
1.It attempts to minimize transportation cost,
Where Transportation cost=flow × distance × unit cost
It Requires assumptions that:
(1) Move cost are independent of the equipment utilization &
(2) Move costs are linearly related to the length of the move.
1. Distance matrix used is the rectilinear distance between department
centroids
2. CRAFT being a path-oriented method, the final layout is dependent on
the initial layout. Therefore, a number of initial layouts should be used
as input to the CRAFT
3. CRAFT allows the use of dummy departments to represent fixed areas
in the layout

Features of CRAFT
CRAFT input requirements are as follows:
 Initial Layout
 Flow Data
 Cost per unit distance
 Total number of departments
 Fixed departments & their location
 Area of departments

CRAFT
When will CRAFT be used?
 CRAFT is used when the number of departments is enormous that
the manual computation would be nearly impossible to do.
 CRAFT is basically used with process layout approach, which also
known as a functional layout that usually used in job shops or a
batch production facility.
What does the CRAFT do?
 CRAFT do uses a pair wise exchange algorithm that may not return
the optimal result because the final solution depends on the initial
layout of the plant.
 Rather than examine all the possible swaps, CRAFT considers the
swap of only adjacent department pair or pairs that have the same
area.

Steps of using CRAFT
 Basic step of CRAFT has been modified a number of times, but we
use COFAD (Tompkins and Reed, 1976) as a reference, a four step
algorithm, tackles the selection of MHS and layout.
 These are the following steps:
1. Determines an initial layout.
2. Selects an MHS for the layout obtained in the first step from a
candidate list of equipment.
3. Calculates and revise the cost of each move based on material
handling equipment to each move. (These three first step is
repeated until a satisfactory solution obtained) To get a good-
quality final solution, the user must provide different starting
solution, evaluate the final solution obtained by CRAFT for each
of these and choose the best one.

Advantages of CRAFT
1. The fact that the calculation is done by computer – sophisticated
calculating machine – is clearly advantages that save a lot both
time and money in the process.
2. It gives us rooms to define the variable and constraints that we
have out here in the real world.
3. Flexibility can be seen as there are 6 buttons that can be utilized
to generate series of different end solution

disadvantages of CRAFT
1. Inefficient
2. Jobs time occurred Jobs do not flow through in an orderly
fashion, therefore backtracking occurs often. Idle time, more
idle time may be experienced while workers are waiting for
more work to arrive from different departments.
3. The (not) end result. End result may need to be modified,
because once CRAFT has determined a solution it may need to
be managed to create a layout that fits in the plant.
4. Greedy algorithm. It is the algorithm that always takes the best
immediate solution. In contrary, a job shop that flow through
the system is not always constant and causes fluctuations in the
process.

Example of CRAFT
Initial Layout
Mid
point/Centroids
of departments

Dept 1 2 3 4 5 6 7 8
1 0 18.5 8.5
2 0 16.5
3 0 14.5
4 8.5 8 0 11
5 0 4.5
6 14.5 10 4 0
7 0
8 8.5 8 0
Computing Inter department distances
Distance measurement
should be for department
where we can have
commuting
Here 1-3,1-7,2-8,3-5,4-2,4-
7,5-8,6-1,6-3, 6-4,8-1,8-4

Dept. 1 2 3 4 5 6 7 8
1 0 18.5 8.5
2 0 16.5
3 0 14.5
4 8.5 8 0 11
5 0 4.5
6 14.5 10 4 0
7 0
8 8.5 8 0
F * C 1 2 3 4 5 6 7 8
1 0 20 2
2 0 1
3 0 2
4 1 0 2
5 0 1
6 10 5 4 0
7 0
8 2 8 0

Exchange 1 and 4
Exchange 1 and 3
Exchange 1 and 2

Dept. 1 2 3 4 5 6 7 8
1 0 7.5 11.5
2 0 16.5
3 0 14.
5
4 11.07 8 0 8.43
5 0 4.5
6 4 10 4 0
7 0
8 7.43 0

Dept. 1 2 3 4 5 6 7 8
1 0 7.5 11.5
2 0 16.5
3 0 14.
5
4 11.07 8 0 8.43
5 0 4.5
6 4 10 4 0
7 0
8 7.43 0
F * C 1 2 3 4 5 6 7 8
1 0 20 2
2 0 1
3 0 2
4 1 0 2
5 0 1
6 10 5 0
7 0
8 2 0

Problem 1
The present layout is shown in the figure. The manager of the company
would like to interchange the department C and F. the handling frequencies
(Cost per unit movement) between the department is given. Can we
interchange the department ? Why?
A
F
C E
B D
Dept. A B C D E F
A 0 90 160 50 0
B 70 0 100 130
C 20 0 0
D 180 10
E 40
F

Solutions
From/to A B C D E F
A 1 1 2 2 3
B 2 1 3 2
C 1 1 2
D 2 1
E 1
F
A
F
C E
B D
Distance between the department….assuming that there is
no back tracking

Dept. A B C D E F
A 0 90 160 50 0
B 70 0 100 130
C 20 0 0
D 180 10
E 40
F
From/to A B C D E F
A 1 1 2 2 3
B 2 1 3 2
C 1 1 2
D 2 1
E 1
F
Dept
.
A B C D E F Tota
l
A 0 90 320 100 0 510
B 140 0 300 260 700
C 20 0 0 20
D 360 10 370
E 40 40
F
Total 1640

A
C
F E
B D
From/to A B C D E F
A 1 3 2 2 1
B 2 1 3 2
C 1 1 2
D 2 1
E 1
F
Dept. A B C D E F
A 0 90 160 50 0
B 70 0 100 130
C 20 0 0
D 180 10
E 40
F
Dept
.
A B C D E F Tota
l
A 0 270 320 100 0 690
B 140 0 300 260 700
C 20 0 0 20
D 360 10 370
E 40 40
F
Total 1820

Problem 2
The defense contractor is evaluating its machine shops current process
layout. Figure shows the current process layout and the table shows the
current trip matrix for the facilities. Health and safety regulation demanded
fixed position of department E and F. Can we change the layout? If yes then
propose the new one with resuced cost
E
D
B F
A C
Dept. A B C D E F
A 8 3 9 5
B 3
C 8 9
D 3
E 3
F

Solution
Identify the maximum trip/traveling/handling frequency of any department
with E and F department
E
D
B F
A C
Dept. A B C D E F
A 8 3 9 5
B 3
C 8 9
D 3
E 3
F

E
D
C F
A B
E
D
B F
A C
E
D
C F
A B
E
D
C F
A B
Dept. A B C D E F
A 8 (3) 3 9 (2) 5
B 3
C 8 (1) 9 (1)
D 3
E 3
F

E
D
B F
A C
E
D
C F
A B
Existing Plan Proposed Plan
Departm
ent pair
No if trips Existing Layout Proposed Layout
Distance Load (No
of trips) *
Distance
Distance Load (No
of trips) *
Distance
A-B 8 2 16 1 8
A-C 3 1 9 2 6
A-E 9 1 3 1 9
A-F 5 3 15 3 15
B-D 3 2 6 1 3
C-E 8 2 16 1 8
C-F 9 2 18 1 9
D-F 3 1 3 1 3
E-F 3 2 6 2 6
92 67

Problem 3
fixed position of department A. Can we change the layout? If yes then
propose the new one with reduced cost
E
D
B F
A C
Dept. A B C D E F
A 4 3 16 2 10
B 3
C 8 9
D 8 8
E 3
F

Dept. A B C D E F
A 4 (4) 3 (5) 16 (1) 2 10 (2)
B 3 (5)
C 8 (3) 9 (3)
D 8 (4) 8 (4)
E 3 (5)
F
E
D
B F
A C
F
B
C E
A D
F
C
B E
A D

F
B
C E
A D
E
D
B F
A C
Departmen
t pair
Distance Load (No of
trips) *
Distance
trips) *
Distance
A-B 4 2 8 2 8
A-C 3 1 3 2 6
A-D 16 2 32 1 16
A-E 2 1 2 3 6
A-F 10 3 30 1 10
B-D 3 2 6 1 18
C-E 8 2 16 1 8
C-F 9 2 18 1 9
D-E 8 3 24 2 16
D-F 8 1 8 2 16
+6=1
19
E-F 3 2 6 =153 2

Problem 4
fixed position of department F & D. Can we change the layout? If yes then
propose the new one with resuced cost
E
D
B F
A C
Dept. A B C D E F
A 4 3 16 2 10
B 3
C 8 9
D 8 8
E 3
F

E
D
C F
B A
Dept. A B C D E F
A 4 3 16 (1) 2 10 (1)
B 3
C 8 9(2)
D 8 8 (3)
E 3
F
E
D
B F
A C
E
D
B F
C A

E
D
C F
B A
E
D
B F
A C
Departmen
t pair
trips) *
Distance
trips) *
Distance
A-B 4 2 8 1 4
A-C 3 1 3 1 3
A-D 16 2 32 1 16
A-E 2 1 2 2 4
A-F 10 3 30 2 20
B-D 3 2 6 2 6
C-E 8 2 16 1 8
C-F 9 2 18 1 9
D-E 8 3 24 3 24
D-F 8 1 8 1 8+6 108
E-F 3 2 6 =153 2

Thank you for your Kind
Attention
Dr Gaurang Joshi
Assistant Professor
Department of Mechanical engineering
Marwadi University, Rajkot, Gujarat, India
Email:- gaurang.joshi@marwadieducation.edu.in

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