facility layout types of layout mathematical models/algorithms facility location problem

Facility layout

Types of layout

Mathematical models/algorithms

Facility location problem

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Introduction

• Facility layout refers to the specific arrangement of physical facilities.

These studies become necessary when:1. A new facility is constructed,2. There is a significant change in demand or throughput

volume,3. A new good or service is introduced to the customer benefit

package, or4. Different processes, equipment, and/or technology is

introduced.

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Introduction

Purpose of facility layout is:• To minimize delays in material handling and customer

movement,• Maintain flexibility,• Use labor and space effectively,• Promote high employee morale and customer satisfaction,• Provide for good house-keeping and maintenance,• Enhance sales as appropriate in manufacturing and service

facilities.

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Types of layout: Product layout

Product layout

• An arrangement based on the sequence of operations that are performed during the manufacturing of a good or delivery of service.

• Continuous-flow, mass-production, and flow shop processes are usually physically organized by a product layout.

• Other examples include: credit card processing, Sub-way sandwich shops, automobile assembly line.

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Advantages of product layout• Since the layout corresponds to the sequence of operations,

smooth and logical flow lines result.• Since the work from one process is fed directly into the next,

small in-process inventories exists.• Total production time per unit is short.• Since the machines are located so as to minimize distances

between consecutive operations, material handling is reduced.• Little skill is usually required by operators at the production

line; hence, training is simple, short, and inexpensive.

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Advantages of product layout

• Simple production planning and control systems are possible.

• Less space is occupied by work in transit and for temporary storage.

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Disadvantages of product layout• A breakdown of one machine may lead to a complete stoppage

of the line that follows that machine.• Since the layout is determined by the product, a change in

product design may require major alterations in the layout.• The pace of production is determined by the slowest machine.• Supervision is general, rather than specialized.• Comparatively, high investment is required, as identical

machines are sometimes distributed along the line.

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Types of layout: Process layout

• Consists of collection of processing departments or cells. • All machines involved in performing a particular process are

grouped together in a process layout.• It is used when there exist many low-volume, dissimilar

products to be produced.• Or when rapid changes occur in the mix and/or when other

layouts are not feasible.• Typical example: job shops.

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Advantages of process layout• Better utilization of machines can result; consequently, fewer

machines are required.• A high degree of flexibility exists relative to equipment or

manpower allocation for specific tasks.• Comparatively low investment in machines is required.• The diversity of tasks offers a more interesting and satisfying

occupation for the operator.• Specialized supervision is possible.

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Disadvantages of process layout

• Since longer flow lines usually result, material handling is more expensive.

• Production planning and control systems are more involved.

• Total production time is usually longer.

• Comparatively large amounts of in-process inventory result.

• Space and capital tied up by work in process.

• Because of diversity of the jobs in specialized departments, higher grades of skills are required.

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Types of layout: Group layout

• A group layout is used when production volumes for individual products are not sufficient to justify product layouts.

• By grouping products into logical product families, a product layout can be justified for the family.

• The groups of processes are referred to as cells; hence the group layout is also referred to as cellular layout.

• Typically has a high degree of intradepartmental flow.• A compromise between a product layout and a process layout.

• In layout design the families of products are formed depending on the sequence of operations.

• Families can also be formed based on part geometry, requirements etc.

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Advantages of group layout:

• Increased machine utilization.

• Team attitude and job enlargement tend to occur.

• 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.

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Limitations of group layout:• General supervision required.• Higher skill levels required of employees than for product

layout.• Compromise between product and process layout, with

associated disadvantages.• Depends on balanced material flow through the cell;

otherwise, buffers and work-in-process storage are required.• Lower machine utilization than for process layout.

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Types of layout: Fixed product layout

• Static product layout is used when product is too large or cumbersome to move through the various processing steps.

• Rather than take the product to the processes, the processes are brought to the product.

• Typical examples: ship-building, aircraft industry, construction.

• Developed by locating workstations or production centers around the product in the appropriate processing sequence.

• Since the work-piece remains stationary, equipment and personnel movements are generally higher than any other type of layout.

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Advantages:• Material movement is reduced.• Promotes job enlargement by allowing individuals or teams to

perform the “whole job.” • Continuity of operations and responsibility results from team.• Highly flexible; can accommodate changes in product design,

product mix, and production volume.• Independence of production centers allows scheduling to

achieve minimum total production time.

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Limitations:

• Increased movement of personnel and equipment.

• Equipment duplication may occur.

• Higher skill requirements for personnel.

• General supervision required.

• Cumbersome and costly positioning of material and machinery.

• Low equipment utilization.

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Exercise: Identify the type of layout

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Facility design

• Direct correlation between operations and facility design.

• Design and layout represent the supporting facility component of service package.

• Factors influencing facility design: Nature and objective of organization; land availability; flexibility; security; aesthetics; community and environment.

• Community and environment: Design of facility has the greatest important where it directly affects the society.

e.g. A prison in a locality?

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Facility design factors

• Nature of organization: The core service offered should dictate the parameters of design. Appropriateness of design also important.

e.g. Physician’s office should give patients privacy while undergoing medical check-up.

Would you open an account in a bank which operates out of a tin-shade?

• Land availability: Space constraints, zoning rules are a reality which a good design should accommodate.

e.g. Franchise for Reid and Taylor in India should have certain minimum sq. feet area.

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Facility design factors

• Flexibility: Design should be dynamic to allow for future growth and changes in services.

e.g. Parking lot for a restaurant.

• Security: Airport design of today needs to consider space for passenger and luggage screening.

• Aesthetics: Service providers delivering essentially same service could be perceived different because of aesthetics.

e.g. Staff canteen and Tifanis?

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Facility layout

• Process terminologyCycle time: Average time between completions of successive

units. Bottleneck: Factor that limits production. Slowest operating

component in the production line. Capacity: Measure of output per unit time when fully busy.

(typically measured as reciprocal of cycle time)Capacity utilization: Measure of how much output is achieved

with respect to the total capacity available.Throughput time: Time taken to complete a process from arrival

to exit. Sum of critical path operations plus waiting time in queue.

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Product layout and work allocation problem

• Standard services can be divided into inflexible sequence of steps that all customer have to go through.

• Resembles manufacturing assembly line.

• The job requiring most time per customer is the bottleneck.

• A well-balanced line would have all jobs of nearly equal duration.

• Grouping of activities (operations) should focus on line-balancing and avoiding bottlenecks.

• Additional stations at the bottleneck could also be considered.

• e.g. Himalaya mess layout.

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Work allocation at an airport

Activity Average time, seconds

1. Deplane 20

2. Immigration 16

3. Baggage claim 40

4. Customs 24

5. Check baggage 18

6. Board domestic flight 15

Bottleneck operation

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Work allocation at an airport

1(20, 180)

2(16, 225)

3(40, 90)

4(24, 150)

5(18, 200)

6(15, 240)

3(40, 90)

1(20, 180)

2, 4(40, 90)

3(40, 90)

2, 4(40, 90)

5(18, 200)

6(15, 240)

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Process layout and relative location problem

• Arrangement by similar processes grouping.• Can simultaneously handle a wide variety of services. • Give flexibility in equipment use and in employee assignment. • Downside: customer has to travel more than in product layout.e.g. Law offices, banks, amusement parks etc.

• Key to a good layout: arrange departments or service center depending the flow of customers and travel time between the pair of departments.

• Pair-wise switching algorithm is one of the methods to solve this problem.

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Objective of process layout algorithm

• Objective function

• Instead of distance, it could be time taken or cost of movement.

facility in the stations ofnumber Total :

from station of Distance :

tostation from moving customers of # :

where

, 1 1

k

jiD

jiN

DNMin

ij

ij

k

i

k

jijij

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Walters Company

Transportation cost of Re. 1 for adjacent departments andCost of Rs. 2 for nonadjacent departments

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Walters Company

• Cost of the default layout = 50+2*100+2*20+30+50+10+2*20+100+50 = Rs. 570

• Cost of new layout = 50+100+20+2*30+50+10+2*20+100+50 = Rs. 480

facility layout types of layout mathematical models/algorithms facility location problem

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