PROCESS SELECTION AND FACILITY LAYOUT Chapter 6 MIS 373: Basic Operations Management.
Layout in operations Management
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Transcript of Layout in operations Management
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FACILITIES LAYOUT
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The Problem In this lesson, we shall discuss how a plant or
workplace should be laid out.
Consider the problem of finding suitable locations for
machines, workstations, storage areas and aisleswithin a plant.
How to find suitable locations for departments,
lounges and mail rooms and labs within a building
that houses a faculty.
The layout problem may also occur in other places
such as grocery stores, hospitals, airports, etc.
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Objectives of Facility LayoutA facility layout problem may have many objectives. In
the context of manufacturing plants, minimizing material
handling costs is the most common one.
Other objectives include efficient utilization of
space
labor
Eliminate
bottlenecks
waste or redundant movement
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Basic Types of Layouts
Process Layout
Used in a job shop for a low volume, customized
products
Product Layout
Used in a flow shop for a high volume, standard
products
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Fixed position Layout
Lathe Press Grind
Weld AssemblyPaint
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Product Layout
Drill Grind Drill
Lathe
Drill
Drill
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As
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Lathe
Bend
Lathe
Mill
Press
Drill
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Product Layout (cont.) Advantages
1. Since the layout corresponds to the sequence of operations, smooth and logical flow linesresult.
2. Since the work from one process is fed directly into the next, small in-process inventoriesresult.
3. Total production time per unit is short.
4. Since the machines are located so as to minimize distances between consecutive operations,material handling is reduced.
5. Little skill is usually required by operators at the production line; hence, training is simple,short, and inexpensive.
6. Simple production planning control systems are possible.
7. Less space is occupied by work in transit and for temporary storage.
Limitations
1. A breakdown of one machine may lead to a complete stoppage of the line that follows thatmachine.
2. Since the layout is determined by the product, a change in product design may require majoralternations in the layout.
3. The pace of production is determined by the slowest machine.
4. Supervision is general, rather than specialized.
5. Comparatively high investment is required, as identical machines (a few not fully utilized) aresometimes distributed along the line.
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Process Layout
Lathe Drill Weld
Mill
Drill
Grind
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Lathe
Lathe
Mill
Mill
Lathe
Mill
Paint
Grind
Assembly
Assembly
Paint
Weld
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Process Layout (cont.) Advantages
1. Better utilization of machines can result; consequently, fewer machines are required.
2. A high degree of flexibility exists relative to equipment or man power allocation forspecific tasks.
3. Comparatively low investment in machines is required.4. The diversity of tasks offers a more interesting and satisfying occupation for the operator.
5. Specialized supervision is possible.
Limitations
1. Since longer flow lines usually exist, material handling is more expensive.
2. Production planning and control systems are more involved.
3. Total production time is usually longer.4. Comparatively large amounts of in-process inventory result.
5. Space and capital are tied up by work in process.
6. Because of the diversity of the jobs in specialized departments, higher grades of skill arerequired.
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Product vs. Process Layouts
A process layout is a functional grouping of machines.
For example, a group of lathe machines are arranged
in one area, drill machines in another area, grinding
machines in another area and so on. Different jobjumps from one area to another differently. Hence, the
flow of jobs is difficult to perceive. This type of layout is
suitable for a make-to-order or an assemble-to-order
production environment, as in a job shop wherecustomization is high, demand fluctuates, and volume
of production low. Since a wide variety of products are
produced, general purpose equipments and workers
with varied skills are needed.
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Product vs. Process Layouts
A product layout arrangement of machines. Every job
visits the machines in the same order. This type of
layout is suitable for a make-to-stock or an assemble-
to-stock production environment, as in a flow shopwhere products are standard, demand stable, and
volume of production high. Since variety is low, special
purpose equipments and workers with a limited skill are
needed. Advantage
A process layout provides flexibility
A product layout provides efficiency.
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Product vs. Process Layouts
Inventory
A product layout has a low work-in-process
inventory and high finished goods inventory because
production is initiated by demand forecast.
On the other hand, a process layout has a high
work-in-process inventory and low finished goods
inventory.
Material handling
A product layout can use automatic guided vehicles
which travels in a fixed path. But, variable path
forklifts are suitable for a process layout.
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Product vs. Process Layouts
Scheduling
In case of a process layout, jobs arrive throughout
the planning period. A process layout requires
dynamic scheduling where a new scheduling
decisions is made whenever a new job arrives.
In case of a product layout, sequencing and timing
of product flow are standard and set when the line is
designed.
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Every cell contains a group of machines which are
dedicated to the production of a family of parts.
One of the problems is to identify a family parts that
require the same group of machines.
These layouts are also called as group technology
layouts.
Cellular Layouts
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Parts 1 2 3 4 5 6 7 8 9 10 11 12
A x x x x x
B x x x xC x x x
D x x x x x
E x x x
F x x x
G x x x x
H x x x
Machines
Cellular Layouts Example
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Parts 1 2 4 8 10 3 6 9 5 7 11 12
A x x x x x
D x x x x xF x x x
C x x x
G x x x x
B x x x x
E x x x
H x x x
Machines
Cellular Layouts Example
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Advantages of Cellular Layouts
Reduced material handling and transit time
Reduced setup time
Reduced work-in-process inventory
Better use of human resources
Better scheduling, easier to control and automate
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Group Layout
Drill Grind Assembly
Drill
Weld
Assembly
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Lathe
Assembly
Grind
Press
Mill
Lathe
Paint
Drill
Drill
Press
Grind
Assembly
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Group Layout (cont.) Advantages
1. Increased machine utilization.
2. Team attitude and job enlargement tend to occur.
3. Compromise between product layout and process layout, with associated advantages.
4. Supports the use of general purpose equipment.5. Shorter travel distances and smoother flow lines than for process layout.
Limitations
1. General supervision required.
2. Higher skill levels required of employees than for product layout.
3. Compromise between product layout and process layout, with associated limitations.
4. Depends on balanced material flow through the cell; otherwise, buffers and work-in-process storage are required.
5. Lower machine utilization than for process layout.
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Factors that Affect the Flow Pattern
Number of parts in each product
Number of operations on each part
Sequence of operations in each part
Number of subassemblies Number of units to be produced
Desired flexibility
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Flow Pat.: Flow between Departments Flow between departments is a criterion often used to evaluate
flow within a facility.
Flow typically is a combination of the basic horizontal flowpatterns shown below. An important consideration in combiningthe flow patterns is the location of the entrance (receiving
department) and exit (shipping department).
Straight
U flow
Serpentine
L flow
S flow
Circularflow
Simplest. Separate
receiving/shipping
crews
Very popular.
Combine receiving/shipping. Simple to
administer
When line is too long
Similar to straight.
It is not as long.
Terminate flow.Near point of origin
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Flow within a facility considering the locations of
entrance and exit
At the same location
On adjacent sides
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Flow within a facility considering the locations of
entrance and exit (cont.)
On the same side but
at opposite ends
On opposite sides
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Vertical Flow Pattern
Flow between buildings exists
and the connection between
buildings is elevated
Ground level ingress (entry)
and egress (exit) are required
Ground level ingress (entry)
and egress (exit) occur on the
same side of the building
Travel between floors occurs on
the same side of the building
Some bucket and belt
conveyors and escalators result
in inclined flow
Backtracking occurs due to the
return to the top floor
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Flow Planning Planning effective flow involves combining the above patterns with adequate
isles to obtain progressive movements from origin to destination.
An effective flow can be achieved by maximizing directed flow paths, reducingflow, and minimizing the costs of flow.
A directed flow path is an uninterrupted flow path progressing directlyfrom origin to destination: the Figure below illustrates the congestion andundesirable intersections that may occur when flow paths are interrupted .
Uninterrupted flow paths
Interrupted flow paths
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Measuring Flow
1. Flow among departments is one of the most important factors in the arrangement of
departments within a facility.
2. Flows may be specified in a quantitative manner or a qualitative manner.
Quantitative measures may include pieces per hour, moves per day, pounds per week.
Qualitative measures may range from an absolute necessity that two departments show be
close to each other to a preference that two departments not being close to each other.3. In facilities having large volumes of materials, information, a number of people
moving between departments, a quantitative measure of f low will typically be the basis for
the arrangement of departments. On the contrary, in facilities having very little actual
movement of materials, information, and people f lowing between departments, but having
significant communication and organizational interrelation, a qualitative measure of flowwill typically serve as the basis for the arrangement of departments.
4. Most often, a facility will have a need for both quantitative and qualitative measures
of f low and both measures should be used.
5. Quantitative flow measure: From-to Chart
Qualitative flow measure: Relationship (REL) Chart
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Activity Relationship Chart
An activity relationship chart is a graphical tool usedto represent importance of locating pairs ofoperations near each other.
Importance is described using letter codes defined
below:A - absolutely necessary
E - especially important
I - important
O - ordinarily important
U - unimportantX - undesirable
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Production area
Office rooms
Storage
Dock area
Locker room
Tool room
A A
A
O
O
U
O O
U
U
U
U
EX
I
Activity Relationship ChartExample: Its ordinarily
important to locate
office rooms near
loading/unloading area
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Activity Relationship Chart
Sample interpretation of the diagram on theprevious slide:
To find how important it is to locate office
rooms near loading/unloading area, find thediamond shaped block at the intersection ofoffice rooms and loading/unloading area. Theblock contains O meaning ordinarilyimportant. Therefore, its ordinarily important to
locate office rooms near loading/unloadingarea.
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From-To Chart
Punch
Saws Milling Press DrillsSaws 18 40 30
Milling 18 38 75
Punch Press 40 38 22
Drills 30 75 22
A from-to chart is used to analyze flow ofmaterials between departments. The examplebelow shows distances in feet. So, the distance
between Saws and Drills is 30 feet. The chartmay also show material handling trips or costper period.
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Flow Patterns
Store
Turning
Milling
Press
Plate
Assembly
Warehouse
Stores Turning Milling
Warehouse Assembly Plate
Press
Stores Press Plate Assembly
Turning Milling Warehouse
Stores Milling Warehouse
Turning Press Plate Assembly
Straight-line flow U-shaped flow
W-shaped flowS-shaped flow
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