7-1 copyright 2009, john wiley & sons, inc. chapter 7: capacity and facilities capacity...

7-7-11Copyright 2009, John Wiley & Sons, Inc.Copyright 2009, John Wiley & Sons, Inc.

Chapter 7: Capacity and FacilitiesChapter 7: Capacity and Facilities

Capacity Planning Basic Layouts Designing Process Layouts Designing Service Layouts Designing Product Layouts Hybrid Layouts


Capacity

Maximum capability to produceMaximum capability to produce Capacity planningCapacity planning

establishes overall level of productive establishes overall level of productive resources for a firmresources for a firm

3 basic strategies for timing of capacity 3 basic strategies for timing of capacity expansion in relation to steady growth in expansion in relation to steady growth in demand (lead, lag, and average)demand (lead, lag, and average)


Capacity Expansion Strategies


Capacity (cont.)

Capacity increase depends on volume and certainty of anticipated demand strategic objectives costs of expansion and operation

Best operating level % of capacity utilization that minimizes unit costs

Capacity cushion % of capacity held in reserve for unexpected

occurrences


Economies of ScaleEconomies of Scale

it costs less per unit to produce high levels of output fixed costs can be spread over a larger number of

units production or operating costs do not increase

linearly with output levels quantity discounts are available for material

purchases operating efficiency increases as workers gain

experience


Best Operating Level for a Hotel


Facility LayoutFacility Layout

Minimize material-handling costs Utilize space efficiently Utilize labor efficiently Increase capacity Facilitate communication and interaction Incorporate safety and security measures Provide flexibility to adapt to changing conditions Increase quality

Arrangement of areas within a facility to:


BASIC LAYOUTS

Process layouts group similar activities together

according to process or function they perform

Product layouts arrange activities in line according to

sequence of operations for a particular product or service

Fixed-position layouts are used for projects in which product

cannot be moved


Process Layout in ServicesProcess Layout in Services

Women’s lingerie

Women’s dresses

Women’s sportswear

Shoes

Cosmetics and jewelry

Entry and display area

Housewares

Children’s department

Men’s department


Manufacturing Process LayoutManufacturing Process Layout

L

L

L

L

L

L

L

L

L

LM

M

M

M

D

D

D

D

D

D

D

D

G

G

G

G

G

G

A A AReceiving andShipping Assembly

Painting Department

Lathe DepartmentMilling

Department Drilling Department

Grinding Department

P

P


A Product LayoutA Product Layout

InIn

OutOut


Description

Type of process

Product

Demand Volume Equipment

Description

Type of process

Product

Demand Volume Equipment

Sequential arrangement of activities

Continuous, mass production, mainly assembly

Standardized, made to stock

Stable High Special purpose

Process

Comparison of ProductComparison of Productand Process Layoutsand Process Layouts

Functional grouping of activities

Intermittent, job shop, batch production, mainly fabrication

Varied, made to order

Fluctuating Low General purpose

Product


Workers Inventory

Storage space Material handling Aisles Scheduling Layout decision Goal

Advantage

Workers Inventory

Storage space Material handling Aisles Scheduling Layout decision Goal

Advantage

Limited skills Low in-process, high

finished goods Small Fixed path (conveyor) Narrow Part of balancing Line balancing Equalize work at each

station Efficiency

Process

Comparison of ProductComparison of Productand Process Layoutsand Process Layouts

Varied skills High in-process, low

finished goods Large Variable path (forklift) Wide Dynamic Machine location Minimize material

handling cost Flexibility

Product


Fixed-Position LayoutsFixed-Position Layouts

Typical of projectsTypical of projects Equipment, workers, Equipment, workers,

materials, other materials, other resources brought to the resources brought to the sitesite

Highly skilled laborHighly skilled labor Often low fixed costOften low fixed cost Typically high variable Typically high variable

costscosts


Designing Process LayoutsDesigning Process Layouts

Goal: minimize material handling costsGoal: minimize material handling costs Block DiagrammingBlock Diagramming

minimize nonadjacent loads minimize nonadjacent loads use when quantitative data is availableuse when quantitative data is available

Relationship DiagrammingRelationship Diagramming based on location preference between areasbased on location preference between areas use when quantitative data is not availableuse when quantitative data is not available


Computerized layout Computerized layout SolutionsSolutions

CRAFT Computerized Relative Allocation of Facilities

Technique CORELAP

Computerized Relationship Layout Planning PROMODEL and EXTEND

visual feedback allow user to quickly test a variety of scenarios

Three-D modeling and CAD integrated layout analysis available in VisFactory and similar software


Designing Service Layouts

Must be both attractive and functional Types

Free flow layouts encourage browsing, increase impulse purchasing, are flexible

and visually appealing Grid layouts

encourage customer familiarity, are low cost, easy to clean and secure, and good for repeat customers

Loop and Spine layouts both increase customer sightlines and exposure to products,

while encouraging customer to circulate through the entire store


Types of Store LayoutsTypes of Store Layouts


Designing Product Layouts

Objective Balance the assembly line

Line balancing tries to equalize the amount of work at each

workstation Precedence requirements

physical restrictions on the order in which operations are performed

Cycle time maximum amount of time a product is allowed to

spend at each workstation


Desired Cycle Time, Desired Cycle Time, Cd

Cd = production time available

desired units of output

Cd = (8 hours x 60 minutes / hour)

(120 units)

Cd = = 4 minutes480

120


Flow Time vs Cycle TimeFlow Time vs Cycle Time

Cycle time = max time spent at any station Cycle time = max time spent at any station Flow time = time to complete all stationsFlow time = time to complete all stations

1 2 3

4 minutes4 minutes 4 minutes4 minutes 4 minutes4 minutes

Flow time = 4 + 4 + 4 = 12 minutesFlow time = 4 + 4 + 4 = 12 minutesCycle time = max (4, 4, 4) = 4 minutesCycle time = max (4, 4, 4) = 4 minutes


Efficiency of Line

ii

ii = 1= 1

ttii

nCnCaaEE = =

ii

ii = 1= 1

ttii

CCddNN = =

EfficiencyEfficiency Minimum number Minimum number of workstationsof workstations

wherewhere

ttii = completion time for element = completion time for element ii

jj = number of work elements= number of work elementsnn = actual number of workstations= actual number of workstations

CCaa = actual cycle time= actual cycle time

CCdd = desired cycle time= desired cycle time


Line Balancing RulesLine Balancing Rules

Use heuristics to assign tasks to Use heuristics to assign tasks to workstationsworkstations Longest processing time (LPT) ruleLongest processing time (LPT) rule

(Pick the feasible task with the LPT) (Pick the feasible task with the LPT) Most number of following tasks ruleMost number of following tasks rule

(Pick the feasible task with the (Pick the feasible task with the largest number of following tasks)largest number of following tasks)

Ranked positional weight ruleRanked positional weight rule


Designing Product Layouts – Designing Product Layouts – con’tcon’t

Step 1:Step 1: Identify tasks & immediate predecessors Identify tasks & immediate predecessors

Step 2:Step 2: Determine output rate Determine output rate

Step 3:Step 3: Determine cycle time Determine cycle time

Step 4:Step 4: Compute the Theoretical Minimum number of Compute the Theoretical Minimum number of StationsStations

Step 5:Step 5: Assign tasks to workstations (balance the Assign tasks to workstations (balance the

line)line)

Step 6:Step 6: Compute efficiency, idle time & balance delay Compute efficiency, idle time & balance delay


Step 1:Step 1: Identify Tasks & Identify Tasks & Immediate PredecessorsImmediate Predecessors

Example 10.4 Vicki's Pizzeria and the Precedence DiagramImmediate Task Time

Work Element Task Description Predecessor (secondsA Roll dough None 50B Place on cardboard backing A 5C Sprinkle cheese B 25D Spread Sauce C 15E Add pepperoni D 12F Add sausage D 10G Add mushrooms D 15H Shrinkwrap pizza E,F,G 18I Pack in box H 15

Total task time 165


Layout CalculationsLayout Calculations

Step 2:Step 2: Determine output rateDetermine output rate Vicki needs to produce 60 pizzas per hourVicki needs to produce 60 pizzas per hour

Step 3:Step 3: Determine cycle timeDetermine cycle time The amount of time each workstation is allowed to The amount of time each workstation is allowed to

complete its taskscomplete its tasks

Limited by the bottleneck task (the longest task Limited by the bottleneck task (the longest task in a process):in a process):

sec./unit 60

units/hr 60

sec/min 60x min/hr 60

units/hroutput desired

sec./day time available)(sec./unit time Cycle

hourper pizzasor units/hr, 72sec./unit 50

sec./hr. 3600

time task bottleneck

time availableoutput Maximum


Layout Calculations (continued)Layout Calculations (continued)

Step 4Step 4:: Compute the theoretical minimum Compute the theoretical minimum number of stationsnumber of stations TM = number of stations needed to achieve TM = number of stations needed to achieve

100% efficiency (every second is used)100% efficiency (every second is used)

Always round up (no partial workstations)Always round up (no partial workstations) Serves as a lower bound for our analysisServes as a lower bound for our analysis

stations 3or 2.75,

nsec/statio 60

seconds 165

time cycle

times taskTM


Layout Calculations (continued)Layout Calculations (continued)

Step 5Step 5:: Assign tasks to workstationsAssign tasks to workstations Start at the first station & choose the Start at the first station & choose the longest eligible tasklongest eligible task following following

precedence relationshipsprecedence relationships Continue adding the longest eligible task that fits without going over the Continue adding the longest eligible task that fits without going over the

desired cycle time desired cycle time When no additional tasks can be added within the desired cycle time, begin When no additional tasks can be added within the desired cycle time, begin

assigning tasks to the next workstation until finishedassigning tasks to the next workstation until finishedWorkstation Eligible task Task Selected Task time Idle time

A A 50 10

B B 5 5

C C 25 35

D D 15 20

E, F, G G 15 5

E, F E 12 48

F F 10 38

H H 18 20

I I 15 5

1

2

3


Layout Calculations (Continued) Layout Calculations (Continued)

Step 6Step 6:: Compute efficiency and balance delayCompute efficiency and balance delay Efficiency (%) is the ratio of total productive time Efficiency (%) is the ratio of total productive time

divided by total timedivided by total time

Balance delay (%) is the amount by which the line Balance delay (%) is the amount by which the line falls short of 100%falls short of 100%

91.7%100sec. 60x stations 3

sec. 165

NC

t (%) Efficiency

8.3%91.7%100%delay Balance


Hybrids LayoutsHybrids Layouts

Cellular layouts group dissimilar machines into work centers

(called cells) that process families of parts with similar shapes or processing requirements

Flexible manufacturing system automated machining and material handling automated machining and material handling

systemssystems which can produce an enormous variety of items

Mixed-model assembly line processes more than one product model in one

line


Cellular Layouts

1.1. Identify families of parts with similar Identify families of parts with similar flow pathsflow paths

2.2. Group machines into cells based on Group machines into cells based on part familiespart families

3.3. Arrange cells so material movement Arrange cells so material movement is minimizedis minimized

4.4. Locate large shared machines at Locate large shared machines at point of usepoint of use


Parts FamiliesParts Families

A family of A family of similar partssimilar parts

A family of related A family of related grocery itemsgrocery items


Original Process LayoutOriginal Process Layout

CA B Raw materials

Assembly

1

2

3

4

5

6 7

8

9

10

11

12


Part Routing MatrixPart Routing Matrix

MachinesParts 1 2 3 4 5 6 7 8 9 10 11 12

A x x x x xB x x x xC x x xD x x x x xE x x xF x x xG x x x xH x x x

Figure 5.8Figure 5.8


Revised Cellular LayoutRevised Cellular Layout

3

6

9

Assembly

12

4

8 10

5

7

11

12

A C BRaw materials

Cell 1 Cell 2 Cell 3


Reordered Routing MatrixReordered Routing Matrix

MachinesParts 1 2 4 8 10 3 6 9 5 7 11 12

A x x x x xD x x x x xF x x xC x x xG x x x xB x x x xH x x xE x x x


Key:Key:

SS = Saw= SawLL = Lathe= LatheHMHM = Horizontal milling = Horizontal milling

machinemachineVMVM = Vertical milling machine= Vertical milling machineGG = Grinder= Grinder

Paths of three Paths of three workers moving workers moving within cellwithin cell

Material Material movementmovement

InIn OutOutWorker 1Worker 1

Worker 2Worker 2

Worker 3Worker 3

Direction of part movement within cellDirection of part movement within cell

S

L

HM

VM

G

VM

L

Final inspection

Finished part

A Manufacturing Cell with Worker PathsSource: J.T. Black, “Cellular Manufacturing Systems Reduce Setup Time, Make Small Lot Production Economical.” Industrial Engineering (November 1983).


Automated Manufacturing CellAutomated Manufacturing Cell

Source: J. T. Black, “Cellular Manufacturing Systems Reduce Setup Time, Make Small LotProduction Economical.” Industrial Engineering (November 1983)


Advantages and Disadvantages Advantages and Disadvantages of Cellular Layoutsof Cellular Layouts

AdvantagesAdvantages Reduced material Reduced material

handling and transit timehandling and transit time Reduced setup timeReduced setup time Reduced work-in- Reduced work-in-

process inventoryprocess inventory Better use of human Better use of human

resourcesresources Easier to controlEasier to control Easier to automateEasier to automate

DisadvantagesDisadvantages Inadequate part familiesInadequate part families Poorly balanced cellsPoorly balanced cells Expanded training and Expanded training and

scheduling scheduling of workersof workers

Increased capital Increased capital investmentinvestment


Flexible Manufacturing Flexible Manufacturing Systems (FMS)Systems (FMS)

FMS consists of numerous programmable machine tools connected by an automated material handling system and controlled by a common computer network

FMS combines flexibility with efficiency FMS layouts differ based on

variety of parts that the system can process size of parts processed average processing time required for part

completion


Full-Blown FMS


Mixed Model Mixed Model Assembly LinesAssembly Lines

Produce multiple models in any order Produce multiple models in any order on one assembly lineon one assembly line

Issues in mixed model linesIssues in mixed model lines Line balancingLine balancing U-shaped lineU-shaped line Flexible workforceFlexible workforce Model sequencingModel sequencing


Balancing U-Shaped LinesBalancing U-Shaped Lines

A B C

D E

Precedence diagram:Precedence diagram:

Cycle time = 12 minCycle time = 12 min

A,B C,D E

(a) Balanced for a straight line(a) Balanced for a straight line

9 min9 min 12 min12 min 3 min3 min

Efficiency = = = .6666 = 66.7 %Efficiency = = = .6666 = 66.7 %24243636

24243(12)3(12)

12 min12 min 12 min12 min

C,D

A,B

E

(b) Balanced for a U-shaped line(b) Balanced for a U-shaped line

Efficiency = = = 100 %Efficiency = = = 100 %24242424

24242(12)2(12)

7-1 copyright 2009, john wiley & sons, inc. chapter 7: capacity and facilities capacity...

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