Facility Layout

Operations Management

P. Kalyanasundaram

What is Facility Layout?

Location or arrangement of everything within & around buildings

Objectives are to maximize Customer/client interaction/satisfaction Utilization of space, equipment, & people Efficient flow of information, material, & people Employee morale & safety

Constraints on Layout Objectives Product design & volume Process equipment & capacity Quality of work life Building & site

Layout Types Fixed-position layout Process-oriented layout Office layout Retail/service layout Warehouse layout Product-oriented layout

Fixed-Position Layout Design is for stationary project Workers & equipment come to site Complicating factors

Limited space at site Changing material needs

Examples Ship building Highway construction

Process-Oriented Layout Design places departments with large flows of

material or people together Dept. areas have similar processes

e.g., All x-ray machines in same area Used with process-focused processes Examples

Hospitals Machine shops

Process Layout+ Allows specialization - focus on one skill

+ Allows economies of scale - worker can watch several machines at once

+ High level of product flexibility

-- Encourages large lot sizes

-- Difficult to incorporate into JIT

-- Makes cross-training difficult

Process-Oriented Layout

Office

Tool Room

Drill Presses

Table Saws

© 1995 Corel Corp.

© 1995 Corel Corp.

Construct ‘from-to-matrix’ Determine space needs for each dept. Develop initial schematic diagram

Determine layout cost, Xij • Cij

By trial-and-error, improve initial layout Prepare detailed plan

Includes factors besides cost

Process-Oriented Layout Steps

50 100 0 0 20

30 50 10 0

20 0 100

50 0

0

From-to-Matrix

5

1 2 3 4 5 6Department

Dept.

1

2

3

4

6

Number of Trips

Process-Oriented Layout ExampleYou work in facilities engineering. You want to find the cost of this layout. The cost of moving 1 load between adjacent dept. is $1. The cost between nonadjacent dept. is $2.

60 ft.

40 ft.

Room 1 Room 2 Room 3

Dept. 1 Dept. 2 Dept. 3

Dept. 4 Dept. 5 Dept. 6

Room 4 Room 5 Room 6

20

100

50 30

50

50

10

20

Schematic Diagram & CostDept. Dept. Cost

1 3 $2001 2 $ 501 6 $ 404 2 $ 504 3 $ 404 5 $ 502 5 $ 102 3 $ 303 6 $100

Total Cost $570

1 2 3

64 5

100

20

30

50 100

50

50

10

20

Schematic Diagram & CostDept. Dept. Cost

1 2 $ 501 3 $1001 6 $ 204 2 $ 504 3 $ 404 5 $ 502 5 $ 102 3 $ 603 6 $100

Total Cost $480

2 1 3

64 5

100

Larger Layout ProblemsMethod works fine for small problems

Larger problems require software CRAFT-tries to minimize material handling

costs Rearrange many large departments to reduce

costs Human “judgement calls” impossible to

computerize

Product-Oriented Layout

Facility organized around product Design minimizes line imbalance

Delay between work stations Types: Fabrication line; assembly line Examples

Auto assembly line Brewery Paper manufacturing.

1 3

2

4

5

Product-Oriented Layout

Office

Belt Conveyor

Operations

Assembles fabricated parts

Uses workstation Repetitive process Paced by tasks Balanced by moving

tasks

Builds components Uses series of

machines Repetitive process Machine paced Balanced by physical

redesign

Product-Oriented Layout TypesFabrication Line Assembly Line

Cellular Layout (Work Cells) Special case of process-oriented layout Consists of different machines brought

together to make a product May be temporary or permanent Example: Assembly line set up to produce

3000 identical parts in a job shop

Work Cell Floor Plan

Office

Tool RoomWork Cell

Saws Drills

Work Cell Advantages

Reduces:

Inventory

Floor space

Direct labor costs

Increases:

Equipment utilization

Employee participation

Quality

Work Cell Layout+ Facilitates cross-training

+ Can easily adjust production volumes

+ Easy to incorporate into JIT

-- Requires higher volumes to justify

-- May require more capital for equipment

Office Layout Example

Relationship Chart

12

3

Ordinary closeness: President (1) & costing (2)

Absolutely necessary: President (1) & secretary (4)

4

I = Important; U = Unimportant

1 PresidentO

2 Costing UA A

3 Engineering IO

4 President’s Secretary

Relationship Chart

A

OE

OU

UU

UU

U

IO

II

IO

UU

UU

UU

UO

UU

I

IU

UEU

IUE

UUA

UA

II

U

U

E

U

34

21

8765

9

10

12

34

56

78

910

Fast-Food Restaurant

IE

UU

UU

OE

EAA

O

12

34

56

X

UU

1 Cooking Burgers

2 Cooking Fries

3 Packing and Storing

4 Drink Dispensers

5 Counter Service

6 Drive-Up Service

I

Example

21

54 6

3

Example

21

54 6

3

Point Scoring System

Assign points for having two items next to each other (including touching corners)A = 16

E = 8

I = 4

O = 1

U = 0

X = -80

Score for Our SolutionTo

From 1 2 3 4 5 6 Total

1 -80 0 0 0 0 -80

2 4 0 0 0 4

3 0 8 8 16

4 16 0 16

5 1 1

Total -43

Retail/Service Layout Design maximizes product exposure to customers,

profitability per square foot Use Closeness ratings to develop service layouts Decision variables

Store flow pattern Allocation of (shelf) space to products

Types Grid design Free-flow design Video

Retail/Service Layout Grid Design

Office CartsCheck-out

Grocery Store

MeatBread

Mil

k

Retail/Service Layout Free-Flow Design

Feature

Display Table

Trans.Counter

Apparel Store

Warehouse Layout Design balances space (cube)

utilization & handling cost Similar to process layout

Items moved between dock & various storage areas

Optimum layout depends on Variety of items

stored No. items picked

© 1995 Corel Corp.

Warehouse Flow

Receiving Shipping

Warehouse Layout

Try to organize storage in such a way that order pickerscan move through the product in a logical and timely manner.

Warehouse Layout

Fastest near the front Fastest within easy reach Bulk storage vs. Single item picking Serpentine vs. oval picking order Restocking: frequency, safety stock Should be designed around the type of

material handling equipment used (like fork-lift trucks, etc)

Cross-Docking Transferring goods

from incoming trucks at receiving docks

to outgoing trucks at shipping docks

Avoids placing goods into storage

In-comingOutgoing

© 1984-1994 T/Maker Co.

© 1995 Corel Corp.

Conclusion Defined facility layout & its objectives Described the 6 types of layout Did load-distance analysis of process layouts Relationship chart & weighting method Defined work cell Stated the retail store flow guidelines Balanced assembly lines

Readiness Assesment Test (RAT)

1. In a layout, work stations are arranged according to the general function they perform without regard to any particular product. a) product, b) process, c) fixed position, d) storage

2. A product layout is more suited to situations where product demand is stable than when it is fluctuating. a) True, b) False

3. Fixed position layouts are used in projects where the product cannot be moved, and therefore equipment, workers, and materials are brought to it. a) True, b) False

4. In general, work-in-process inventory is large for a product layout and small for a process layout. a) True, b) False

5. Which of the following characteristics is associated with process layout? a) stable demand b) less skilled workers c) specialized machinery d) low volume e) product for general market

RAT – Solution 1. In a Process layout, work stations are arranged according to the general

function they perform without regard to any particular product.

2. True. A product layout is more suited to situations where product demand is stable than when it is fluctuating.

3. True. Fixed position layouts are used in projects where the product cannot be moved, and therefore equipment, workers, and materials are brought to it.

4. False. In general, work-in-process inventory is large for a process layout and small for a product layout.

5. Low Volume is associated with process layout.

Line Balancing is the process of assigning tasks to workstations in such a way that the workstations have approximately equal time requirements.

Design Product Layouts: Line Balancing

Cycle time is the maximum time allowed at each workstation tocomplete its set of tasks on a unit.

Cycle Time

D

OT = timecycle = CT

rateoutput Desired= D

dayper timeoperating OT

CT

OT = rateOutput

D

OT = timecycle = CT

rateoutput Desired= D

dayper timeoperating OT

CT

OT = rateOutput

Determine Maximum Output

task timeof sum = t

CT

t)( =N

Determine the Minimum Number of Workstations Required

Precedence diagram: Tool used in line balancing to display elemental tasks and sequence requirements

A Simple Precedence Diagrama b

c d e

0.1 min.

0.7 min.

1.0 min.

0.5 min. 0.2 min.

Precedence Diagram

Arrange tasks shown in Figure into three workstations. Use a cycle time of 1.0 minute Assign tasks in order of the most number

of followers

Example 1: Assembly Line Balancing

WorkstationTimeRemaining

Eligible AssignTask

RevisedTime Remaining

StationIdle Time

1 1.0

0.9

0.2

a, c

c

none

a

c

-

0.9

0.2

0.2

2 1.0 b b 0.0 0.0

3 1.0

0.5

0.3

d

e

-

d

e

-

0.5

0.3 0.3

0.5

Example 1 Solution

Percent idle time = Idle time per cycle

(N)(CT)

Efficiency = 1 – Percent idle time

Calculate Percent Idle Time

Assign tasks in order of most following tasks.

Count the number of tasks that follow

Assign tasks in order of greatest positional weight.

Positional weight is the sum of each task’s time and the times of all following tasks.

Some Heuristic (intuitive) Rules:Line Balancing Rules

Ranked Positional Weight Heuristic A task is prioritized based on the cumulative assembly

time associated with itself and its successors. Tasks are assigned in this order to the lowest

numbered feasible workstation. Cumulative remaining assembly time constrains the

number of workstations required. Procedure requires computation of positional weight

PW(i) of each task.

Data Known : Two 4 hour-shifts, 4 days a week will be used for

assembly. Each shift receives two 10 minute breaks. Planned production rate of 1500 units/week.

Model Car Production – Example

RPW Procedure - Example

Task Activity Assembly Time

Immediate Predecessor

a Insert Front Axle / Wheels

20 -

b Insert Fan Rod 6 a

c Insert Fan Rod Cover

5 b

d Insert Rear Axle / Wheels

21 -

e Insert Hood to Wheel Frame

8 -

f Glue Windows to top 35 -

g Insert Gear Assembly

15 c, d

h Insert Gear Spacers 10 g

i Secure Front Wheel Frame

15 e, h

j Insert Engine 5 c

k Attach Top 46 f, i, j

l Add Decals 16 k

Example Solution – Cont…

C = 70 Seconds. N = 202/70 = 2.88 workstations (or) 3

unit

minutes17.1

shift

minutes220

day

shifts2

week

days4

Units1500

Week1C

Example SolutionModel Car Precedence Structure

a

d

e

f

b c j

g h

i k l

20

21

8

35

6 5 5

15 10

15 46 16

RPW Procedure - SolutionPositional Weight calculated based on

the precedence structure (previous slide).

PWl = its task time = 16

PWk = tk + PWl = 46+16 = 62

PWj = tj + PWk = 5+62 = 67

Task PW Ranked PW

a 138 1

b 118 3

c 112 4

d 123 2

e 85 8

f 97 6

g 102 5

h 87 7

i 77 9

j 67 10

k 62 11

l 16 12

RPW Solution Cont… Assignment order is given by the rankings. Task a assigned to station 1.

c - ta = 70 – 20 = 50 seconds left in Station 1.

Next Assign task d 50 – 21 = 29 seconds left in Station 1.

j, k, l70, 65, 19, 33

f, h, e, i70, 35, 25, 17, 22

a, d, b, c, g70, 50, 29, 23, 18, 31

TasksTime RemainingStation

Team Exercise Assembly of a product has been divided into elemental tasks suitable for assignment to unskilled workers. Task times and constraints are given below. Solve by RPW Procedure

g14h

e, f6g

c, d7f

b6e

a10d

a6c

-18b

-20a

Immediate Predecessors

TimeTask

Exercise Solution

a

b

d

e

c

f

g h

20

18

6

1010

6

7

6 14

Task PWi Rank

a 63 1

b 44 2

c 33 4

d 37 3

e 26 6

f 27 5

g 20 7

h 14 8Workstation Assigned

TasksRemaining

Time

1 a, d 30, 10, 0

2 b, c, e 30, 12, 6, 0

3 f, g, h 30, 23, 17, 3