facility design and layout

7/30/2019 Facility Design and Layout

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Facility Design and Layout


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1. To understand different types of layout patterns,

how they relate to process choice, and some ofthe methods to evaluate alternative layout plans.

2. To understand the key issues involved in

designing product layouts and balance assemblylines to enable efficient and economicalproduction of goods and services.

3. To understand the major issues involved indesigning process layouts, and to be able toapply simple tools to develop a good processlayout design.

Learning Objectives


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4. To understand the issues that operations

managers must address in designing individualworkstations to meet productivity, quality, andemployee safety requirements.

5. To understand the importance of addressing thesocial and environmental aspects of work indesigning jobs and team-based processes toenhance employee motivation and satisfaction.

Learning Objectives


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Facility layoutrefers to the specific arrangement

of physical facilities. Facility-layout studies arenecessary whenever

(1) a new facility is constructed,

(2) there is a significant change in demand orthroughput volume,

(3) a new good or service is introduced to the

customer benefit package, or(4) different processes, equipment, and/or

technology are installed.


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Purposes of layout studies are to:

minimize delays in materials handling and customermovement,

maintain flexibility,

use labor and space effectively,

promote high employee morale and customersatisfaction,

provide for good housekeeping and maintenance, &

enhance sales as appropriate in manufacturing andservice facilities.



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Other Facility Layout Issues

Essentially, a good layout should support the ability ofoperations to accomplish its mission.

If the facility layout is flawed in some way, process

efficiency and effectiveness suffers.

In manufacturing, facility layout is generally unique, andchanges can be accomplished without much difficulty.

For service firms, however, the facility layout is oftenduplicated in hundreds or thousands of sites. This makesit extremely important that the layout be designedproperly, as changes can be extremely costly.



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Innovations at McDonalds

Indoor seating (1950s)

Drive-through window (1970s)

Adding breakfast to the menu(1980s)

Adding play areas (1990s)

Three out of the four are layoutdecisions!


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McDonalds New Kitchen Layout

Fifth major innovation

Sandwiches assembled in order Elimination of some steps, shortening of

others No food prepared ahead except patty New bun toasting machine and new bun

formulation

Repositioning condiment containers Savings of $100,000,000 per year in food

costs


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McDonalds New Kitchen Layout


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Types of Facility Layouts

Aproduct layoutis an arrangement basedon the sequence of operations that areperformed during the manufacturing of a

good or delivery of a service.

Examples: winemaking industry, Subwaysandwich shops, paper manufacturers,

insurance policy processing, and automobileassembly lines.



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Product Layout

Advantages of product layouts include lowerwork-in-process inventories, shorter processing

times, less material handling, lower labor skills,and simple planning and control systems.

Disadvantages include a breakdown at one

workstation can cause the entire process to shutdown, a change in product design or theintroduction of new products may require majorchanges in the layout, and little job satisfaction.



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Exhibit 1 Product Layout for Wine Manufacturer


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Aprocess layoutconsists of a functionalgrouping of equipment or activities that do

similar work. Examples: legal offices, shoe manufacturing,

jet engine turbine blades, and hospitals use aprocess layout.



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Process Layout

Advantages include a lower investment in generalpurpose equipment, and the diversity of jobs

inherent in a process layout can lead to increasedworker satisfaction.

Disadvantages include high movement andtransportation costs, more complicated planningand control systems, longer total processing time,higher in-process inventory or waiting time, andhigher worker-skill requirements.



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Exhibit 2 Process Layout for a Machine Shop


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Cellular/Group Layout

Group technology, or cellularmanufacturing,classifies parts into familiesso that efficient mass-production-type layouts

can be designed for the families of goods orservices.

In a group, or cellular, layout, the design is not

according to the functional characteristics ofequipment, but rather by groups of differentequipment (called cells) needed for producingfamilies of goods or services.



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Cellular/Group Layout

Group layouts are used to centralize peopleexpertise and equipment capability.

Examples: groups of different equipment (calledcells) needed for producing families of goods orservices, group legal (labor law, bankruptcy,divorce, etc.) or medical specialties (maternity,oncology, surgery, etc.).



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Exhibit 3 Cellular Manufacturing Layout

Source: E. Paul Degarmo, J. T. Black, and Ronald A. Kosher,Materials and

Processes in Manufacturing, 9th Edition, John Wiley & Sons, 2003.


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Exhibit 4 Two Part Families


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Exhibit 5 Process Layout Without Part Families


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Exhibit 6 Group Layout Based on Part Families


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Exhibit 7.7Exhibit 7 Process (Job Shop) Layout atRockwells Dallas Factory


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Exhibit 8 Cellular Layout at Rockwells Dallas Factory


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Afixed-position layoutconsolidates theresources necessary to manufacture a goodor deliver a service, such as people, materials,and equipment, in one physical location.

The production of large items such as heavymachine tools, airplanes, buildings,locomotives, and ships is usually

accomplished in a fixed position layout.



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Fixed-position layout

This fixed-position layout is synonymouswith the "project" classification of processes

Service-providing firms also use fixed-position layouts; examples include majorhardware and software installations,sporting events, and concerts.



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Exhibit 9 Comparison of Basic Layout Patterns

It is clear hat basic trade-off in selecting among these layouttypes is flexibility versus productivity.

Process layout offer high flexibility with low productivity, andproduct layouts have limited flexibility with high productivity.

Group layouts are designed to balance the advantages of bothtypes.

Fixed-position layouts are most productive when resources are

on-site, and offer flexibility to change as the situation changes.


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Materials Handling Issues and Systems

Industrial trucks Fixed-path conveyor systems

Overhead cranes

Automated storage and retrieval systems

Tractor-trailer systems

Automated guided vehicles (AGVs)



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Facility Layout in Service Organizations

Facility Design in Service Organizations

Service organizations use product, process,group, and fixed-position layouts to organize

different types of work.

Process Layout ExamplesLibraries place reference materials, serials, andmicrofilms into separate areas; hospitals groupservices by function also, such as maternity,

oncology, surgery, and X-ray; and insurancecompanies have office layouts in whichclaims, underwriting, and filing are individualdepartments.


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Facility Layout in Service Organizations

Facility Design in Service Organizations

Product Layout ExamplesService organizations that provide highly standardizedservices tend to use product layouts. For example,Exhibit 10 shows the layout of the kitchen at a small

pizza restaurant that has both dine-in and delivery.

Lenscrafter Uses Both Process and ProductLayouts

In Exhibit 11 we see the customer contact area isarranged in a process layout. In the lab area,however, where lenses are manufactured, a grouplayout is used.

E hibit 10 P d t L t f Pi Kit h


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Exhibit 10 Product Layout for a Pizza Kitchen

E hibit 11 A S h ti f T i l L C ft St L t


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Exhibit 11 A Schematic of a Typical LensCrafters Store Layout


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Designing Product Layouts

Aproduct layoutis an arrangement based on thesequence of operations that are performed duringthe manufacturing of a good or delivery of a service.

Flow-blocking delayoccurs when a work centercompletes a unit but cannot release it because thein-process storage at the next stage is full. Theworker must remain idle until storage spacebecomes available.

Lack-of-work delayoccurs whenever one stagecompletes work and no units from the previousstage are awaiting processing.


E hibit 12 A T i l M f t i W k t ti L t


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Exhibit 12 A Typical Manufacturing Workstation Layout

E hibit 13 P d t L t D i O ti


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Exhibit 13 Product Layout Design Options

bl l


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Assembly Line Balancing

Assembly-Line Balancing

An assembly line isa product layout dedicated tocombining the components of a good or servicethat has been created previously.

Assembly line balancingis a technique to grouptasks among workstations so that eachworkstation has in the ideal case the sameamount of work.

It is an analysis process that tries to equally dividethe work to be done among workstations so thatthe number of workers or workstations required on

a production line is minimized.

A bl Li B l i


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Assembly-Line Balancing

To begin, we need to know three types of informationto balance an assembly line:

the set of tasks to be performed and the time

required to perform each task (work content),

the precedence relations among the tasks thatis, the sequence in which tasks must be

performed, and

the desired output rate or forecast of demand forthe assembly line.

A bl Li B l i


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Terminology Tasks elements of work

Task precedence-sequence or order in which task mustbe performed

Task times - amount of time required for a well trainedworker or unattended machine to perform a task.

Cycle time-time between products coming off the end of aproduction line Production time per hour-number of minutes in each

hour that a workstation is working on the average. Workstation physical location where a particular set of

tasks is performed. Work center- physical location where two or more

identical workstations are located. If more than oneworkstation is required to provide enough production

capacity, they are combined to forma work center

A bl Li B l i


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A bl Li B l i


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Let us say that we need a product to come off the end of aproduction line every 5 minutes; then the cycle time is 5 minute.

This means that there must be a product coming out of everyworkstation every 5 minute or less. If the time required to do the tasks at a were 10 minutes, then

two workstations would be combined into a work center suchthat two products would be coming out of the center every 10

minutes, or equivalent of one every 5 minute. On the other hand, if the amount of work assigned to a

workstation is only 4 minutes, that workstation would work 4minutes and be idle 1 minute.

It is practically impossible to assign tasks to workstations such

that each one produces a product in exactly 5 minutes. In line balancing, our objective is to assign tasks to workstations

such that there is little idle time. This means assigning tasks to workstations and work centers

such that a finished product is completed very close to but notexceeding the cycle time.


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Line Balancing Procedure

1. Determine the tasks involved in completing 1 unit2. Determine the order in which tasks must be done

3. Draw a precedence diagram

4. Estimate task times

5. Calculate the cycle time6. Calculate the minimum number of workstations

7. Use a heuristic to assign tasks to workstations

A bl Li B l i


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Line Balancing Heuristics

Heuristic methods, or methods based on simple rules, have been usedto develop good solutions to these problems

Among these methods are Incremental Utilization Method

Add tasks to a workstation in order of task precedence one at a time untilutilization is 100% or is observed to fall

Then the above procedure is repeated at the next workstation for theremaining tasksPro Appropriate when one or more task times is equal to or greater than thecycle timeCon Might create the need for extra equipment

Longest-Task-Time Method

Adds tasks to a workstation one at a time in the order of task precedence.If two or more tasks tie for order of precedence, the one with the longest tasktime is addedConditions for its use:

No task time can be greater than the cycle timeThere can be no duplicate workstations

Exhibit 14 A Three Task Assembly Line


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Exhibit 14 A Three-Task Assembly Line

The total time required to complete one part is0.5+0.3+0.2 = 1.0 minute

Suppose that one worker performs all three tasksin sequence. In an 8-hour day, the worker couldproduce (1part/1.0min)(60 minutes perhour)(8hours per day) = 480 parts/day.

Hence the capacity of the process is 480parts/day

A Three Task Assembly Line


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A Three-Task Assembly Line

Suppose that three workers are assigned to the line, each performingone of the three tasks.

The first operator can produce 120 parts per hour, since the task timeis 0.5 minute.

Thus a total of (1 part/0.5 min)(60 minutes per hour)(8hours per day)= 960 parts/day could be sent to operator 2.

Since the time operator 2 needs for the operation is only 0.3 minute,operator 2 could produce (1 part/0.3 min)(60 minutes per hour)(8hours per day)=1,600 parts/day.

However, operator 2 cannot do so because the first operator has alower production rate. The second operator will be idle some of thetime waiting on components to arrive.

Even though the third operator can produce (1 part/0.2 min)(60

minutes per hour)(8 hours per day) = 2,400 parts/day, we see thatthe maximum output of this three-operator assembly line is 960 partsper day.

That is workstation 1 performing task A is the bottleneck in theprocess.



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A third alternative is to use two workstations.

The first operator could perform operation A while thesecond performs operations B and C.

Since each operator needs 0.5 minutes to perform theassigned duties, the line is in perfect balance, and 960parts per day can be produced.

We can achieve the same output rate with two operatorsas we can with three, thus saving labor costs.

How you group work tasks and activities into workstationsis important in terms of process capacity (throughput),cost, and time to do the work.



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Cycle timeis the interval between successiveoutputs coming off the assembly line.

In the three-operation example shown in Exhibit14, if we use only one workstation, the cycle timeis 1 minute; that is, one completed assembly is

produced every minute.

If two workstations are used, as just described,the cycle time is 0.5 minute.

If three workstations are used, the cycle time isstill 0.5 minute, because task A is the bottleneck,or slowest operation. The line can produce onlyone assembly every 0.5 minute.


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Example: Armstrong Pumps

Armstrong produces bicycle tire pumps on a

production line. The time to perform the 6 tasks

in producing a pump and their immediate

predecessor tasks are shown on the next slide. Ten pumps per hour must be produced and 45

minutes per hour are productive.

Use the incremental utilization heuristic to

combine the tasks into workstations in order to

minimize idle time.


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Line BalancingTasks that Time to

Immediately Perform

Task Precede Task (min.)

A -- 5.4

B A 3.2C -- 1.5

D B,C 2.8

E D 17.1

F E 12.8Total = 42.8


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Line Balancing

Network (Precedence) Diagram

A

C

B ED F


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Line Balancing

Cycle Time

= 45/10 = 4.5 minutes per pump

Productive Time per HourCycle Time =

Demand per Hour


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Line Balancing

Minimum Number of Workstations

Minimum

Number of

Workstations

= [(42.8)(10)]/45 = 9.51 workstations

(Total Task Time)(Demand per Hour)=

Productive Time per Hour


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Line BalancingIncremental Utilization Heuristic


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Line Balancing

Utilization of Production Line

= 9.51/10 = .951 = 95.1%

Minimum Number of WorkstationsUtilization =

Actual Number of Workstations

Incremental Utilization Heuristic


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Incremental Utilization Heuristic

Line Balancing at Texttech

Texttech, a large electronics manufacturer, assembles model AT75handheld calculators at its Midland, Texas, plant. The assembly tasks thatmust be performed on each calculator are shown on the next slide. Theparts used in this assembly line are supplied by materials-handlingpersonnel to parts bins used in each task. The assemblies are moved alongby belt conveyors between workstations.

An average of six minutes is not productive because of lunch, personal time,machine breakdown, and startup and shutdown time.

Texttech wants this assembly line to produce 540 calculators per hour:a. Compute the cycle time per calculator in minutes

b. Compute the minimum no of workstationsc. How would you combine the tasks into workstations to minimize the idle

time? Evaluate your proposal.



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Task Task that must immediately

precede

Time to Perform Task

(minutes)

A 0.18

B A 0.12

C A 0.32

D A 0.45

E B, C, D 0.51

FE 0.55

G F 0.38

H G 0.42

I H 0.30

J I 0.18

K J 0.36L J 0.42

M K, L 0.48

N M 0.30

O N 0.39

TOTAL 5.36

Solution


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Solution

Solution


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Solution



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C. Balance the line

A

D

C FE G

B

H I J

K

J0M

L

N



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Work Centre Tasks Min/Calc No of WS [(3) /

CT]

Actual no of

WS required

Utilization of WS

[(4) / (5)] x 100

1 A .18 1.8 2 90 %

1 A,B .30 3.0 3 100

2 C .32 3.2 4 80

2 C,D .77 7.7 8 96.3

2 C,D,E 1.28 12.8 13 98.5

2 C,D,E,F 18.3 18.3 19 96.3

3 F 5.5 5.5 6 91.7

3 F,G 9.3 9.3 10 93.0

3 F,G,H 13.5 13.5 14 96.4

3 F,G,H,I 16.5 16.5 17 97

3 F,G,H,I,J 18.3 18.3 19 96.3

4 J 1.8 1.8 2 90

4 J,K 5.4 5.4 6 90

4 J,K,L 9.6 9.6 10 96

4 J,K,L,M 14.4 14.4 15 96

4 J,K,L,M,N 17.4 17.4 18 96.7

4 J,K,L,M,N,O 21.3 21.3 22 96.8

Total 55



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Summarize the assignment of tasks to workstations on the production line

Compute the efficiency of your proposal

Tasks in work centers A,B C,D,E F,G,H,I J,K,L,M,N,O

Work Centers 1 2 3 4

Actual number of workstations 3 13 17 22 55 TOTAL



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Line Balancing with the Longest-Task-Time Heuristic

a. Draw a precedence diagram.b. Assuming that 55 minutes/hour are productive, compute the cycle timeneeded to obtain 5o units per hour.c. Determine the minimum number of workstations.d. Assign tasks to workstations using the LTT heuristic

e. Calculate the utilization of the solution in part d.

Task Immediate

Predecessor

Task Time

(minutes)A - 0.9

B A 0.4

C B 0.6

D C 0.2

E C 0.3

F D,E 0.4

G F 0.7

H G 1.1

Total 4.6



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sse b y e a a c g

Steps in the Longest-Task-Time Heuristic

1. Let i=1, where i is the number of workstation being formed.2. Make a list of all tasks that are candidates for assignment to thisworkstation. For a task to be on this list, it must satisfy all of theseconditions.a. It cannot have been previously assigned to this or any previous

workstation

b. Its immediate predecessors must have been assigned to this or aprevious workstation

c. The sum of its task time and all other times of tasks already assignedto the workstation must be less than or equal to the cycle time. If nocandidates can be found, go to step 4.

3. Assign the task from the list with the longest task time to theworkstation. Go back to step 2.

4. Close the assignment of tasks to workstation i. This can occur in twoways. If there are no tasks on the candidate list for the workstation butthere are still tasks to be assigned, set I = i+1 and go back to step 2. OF

there are no more unassigned tasks, the procedure is complete.



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Line Balancing with the Longest-Task-Time Heuristic

a. Draw a precedence diagram.

A

E

B FC G

D

H



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d. Assign tasks to workstations using the LTT heuristic

(1) (2) (3) (4) (5) (6)

Workstation Candidate List Task Task Time Sum of TaskTime

UnassignedTask Time atWorkstation[1.1 (5)

1 A A 0.9 0.9 0.2

2 B B 0.4 0.4 0.7

2 C C 0.6 1.0 0.1

3 D,E E 0.3 0.3 0.8

3 D D 0.2 0.5 0.6

3 F F 0.4 0.9 0.2

4 G G 0.7 0.7 0.4

5 H H 1.1 1.1 0



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d. Assign tasks to workstations using the LTT heuristic

Summary of the assignment of tasks to workstations on the production line:

Tasks in Workstation Workstation

A 1

B,C 2

E,D,F 3

G 4

H 5



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facility design and layout

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