tn6 facility layout

1

Facility Layout

2

• Facility Layout and Basic Formats

• Process Layout

• Layout Planning

• Assembly Line balancing

• Service Layout

OBJECTIVES

3

Facility Layout Defined

Facility layout can be defined as the process by which the placement of departments, workgroups within departments, workstations, machines, and stock-holding points within a facility are determined

This process requires the following inputs:

• Specification of objectives of the system in terms of output and flexibility

• Estimation of product or service demand on the system

• Processing requirements in terms of number of operations and amount of flow between departments and work centers

• Space requirements for the elements in the layout

• Space availability within the facility itself

4

Criteria for a good Layout – designing of a layout is a creative exercise

• Maximum Flexibility

• Maximum Co-ordination

• Maximum visibility

• Maximum Accessibility

• Minimum distance

• Minimum handling

• Minimum discomfort

• Inbuilt safety

• Efficient process flow

• Identification

5

Basic Production Layout Formats

• Process Layout (also called job-shop or functional layout)

• Product Layout (also called flow-shop layout)

• Group Technology (Cellular) Layout

• Fixed-Position Layout (Static Layout)

• Service Layouts

6

Process Layout: Interdepartmental Flow

• Given

• The flow (number of moves) to and from all departments

• The cost of moving from one department to another

• The existing or planned physical layout of the plant

• Determine

• The “best” locations for each department, where best means maximizing flow, which minimizing costs

7

Process Layout

Advantages : • Reduced investment on m/cs – as they are general purpose• Production flexibility • Maximum utilization of men and machines• Easier maintenanceDisadvantages• Difficulty in materials movement• Layout requires more space• Production time is more as WIP has to travel from point to point in

search of the machines• Accumulation of WIP at different locationsDeveloping a process layout• Graphic and schematic analysis – templates and two – dimension

cutouts of equipments drawn to scale are the layout planning tools.• Computer models – CRAFT (Computerized Relative Allocation of

Facilities Technique)• Load Distance Model- used to minimize the material flow

8Process Layout: CRAFT Approach

• It is a heuristic program; it uses a simple rule of thumb in making evaluations: • "Compare two departments at a time and

exchange them if it reduces the total cost of the layout."

• It does not guarantee an optimal solution

• CRAFT assumes the existence of variable path material handling equipment such as forklift trucks

• (Computerized Relative Allocation of Facilities Technique)

9

Product Layout

Advantages • Avoids production bottlenecks • Economy in manufacturing time• Requires less floor area per unit of production • WIP reduced – consequently less inventories.• Greater incentive to group of workers to raise their level of

production.Disadvantages• Layout is known for inflexibility • Expensive layout • Lesser scope for expansion• M/c breakdown along the production line can disrupt the whole

system.Developing a product layout• Line Balancing • Mixed – model Line balancing

Assembly Lines – different configurations

• Materials Handling Devices – Belt or Roller Conveyors / Overhead Cranes

• Line Configuration – Straight Line / U-shaped / Branching

• Pacing – Mechanical / Human

• Product Mix – One Product / Multiple Products

• Workstation Characteristics – Workers may sit / stand / walk with the line

• Length of the Line – Few Workers / Many Workers

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Station 1

Minutes per Unit 6

Station 2

7

Station 3

3

Assembly Lines Balancing Concepts

Question: Suppose you load work into the three work stations below such that each will take the corresponding number of minutes as shown. What is the cycle time of this line?

Question: Suppose you load work into the three work stations below such that each will take the corresponding number of minutes as shown. What is the cycle time of this line?

Answer: The cycle time of the line is always determined by the work station taking the longest time. In this problem, the cycle time of the line is 7 minutes. There is also going to be idle time at the other two work stations.

Answer: The cycle time of the line is always determined by the work station taking the longest time. In this problem, the cycle time of the line is 7 minutes. There is also going to be idle time at the other two work stations.

12

Example of Line Balancing

You’ve just been assigned the job of setting up an electric fan assembly line with the following tasks:

Task Time (Mins) Description PredecessorsA 2 Assemble frame NoneB 1 Mount switch AC 3.25 Assemble motor housing NoneD 1.2 Mount motor housing in frame A, CE 0.5 Attach blade DF 1 Assemble and attach safety grill EG 1 Attach cord BH 1.4 Test F, G

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Example of Line Balancing: Structuring the Precedence Diagram

Task PredecessorsA None

A

B A

B

C None

C

D A, C

D

Task PredecessorsE D

E

F E

F

G B

G

H F, G

H

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Example of Line Balancing: Precedence Diagram

A

C

B

D E F

GH

2

3.25

1

1.2 .5

11.4

1

Question: Which process step defines the maximum rate of production?

Question: Which process step defines the maximum rate of production?

Answer: Task C is the cycle time of the line and therefore, the maximum rate of production.

Answer: Task C is the cycle time of the line and therefore, the maximum rate of production.

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Example of Line Balancing: Determine Cycle Time

Required Cycle Time, C = Production time per period

Required output per periodRequired Cycle Time, C =

Production time per period

Required output per period

C = 420 mins / day

100 units / day= 4.2 mins / unitC =

420 mins / day

100 units / day= 4.2 mins / unit

Question: Suppose we want to assemble 100 fans per day. What would our cycle time have to be?

Question: Suppose we want to assemble 100 fans per day. What would our cycle time have to be?

Answer: Answer:

17

Example of Line Balancing: Determine Theoretical Minimum Number of

Workstations

Question: What is the theoretical minimum number of workstations for this problem?

Question: What is the theoretical minimum number of workstations for this problem?

Answer: Answer: Theoretical Min. Number of Workstations, N

N = Sum of task times (T)

Cycle time (C)

t

t

Theoretical Min. Number of Workstations, N

N = Sum of task times (T)

Cycle time (C)

t

t

N = 11.35 mins / unit

4.2 mins / unit= 2.702, or 3t

N = 11.35 mins / unit

4.2 mins / unit= 2.702, or 3t

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Example of Line Balancing: Rules To Follow for Loading Workstations

Assign tasks to station 1, then 2, etc. in sequence. Keep assigning to a workstation ensuring that precedence is maintained and total work is less than or equal to the cycle time. Use the following rules to select tasks for assignment.

Primary: Assign tasks in order of the largest number of following tasks

Secondary (tie-breaking): Assign tasks in order of the longest operating time

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A

C

B

D E F

GH

2

3.25

1

1.2 .5

11.4

1

Station 1 Station 2 Station 3

Task Followers Time (Mins)A 6 2C 4 3.25D 3 1.2B 2 1E 2 0.5F 1 1G 1 1H 0 1.4

20

A

C

B

D E F

GH

2

3.25

1

1.2 .5

11.4

1


A (4.2-2=2.2)


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A

C

B

D E F

GH

2

3.25

1

1.2 .5

11.4

1

A (4.2-2=2.2)B (2.2-1=1.2)



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A

C

B

D E F

GH

2

3.25

1

1.2 .5

11.4

1

A (4.2-2=2.2)B (2.2-1=1.2)G (1.2-1= .2)

Idle= .2



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A

C

B

D E F

GH

2

3.25

1

1.2 .5

11.4

1

C (4.2-3.25)=.95


A (4.2-2=2.2)B (2.2-1=1.2)G (1.2-1= .2)

Idle= .2


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C (4.2-3.25)=.95

Idle = .95

A

C

B

D E F

GH

2

3.25

1

1.2 .5

11.4

1


A (4.2-2=2.2)B (2.2-1=1.2)G (1.2-1= .2)

Idle= .2


25

C (4.2-3.25)=.95

Idle = .95

A

C

B

D E F

GH

2

3.25

1

1.2 .5

11.4

1

D (4.2-1.2)=3


A (4.2-2=2.2)B (2.2-1=1.2)G (1.2-1= .2)

Idle= .2


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A

C

B

D E F

GH

2

3.25

1

1.2 .5

11.4

1

C (4.2-3.25)=.95

Idle = .95

D (4.2-1.2)=3E (3-.5)=2.5


A (4.2-2=2.2)B (2.2-1=1.2)G (1.2-1= .2)

Idle= .2


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A

C

B

D E F

GH

2

3.25

1

1.2 .5

11.4

1

C (4.2-3.25)=.95

Idle = .95

D (4.2-1.2)=3E (3-.5)=2.5F (2.5-1)=1.5


A (4.2-2=2.2)B (2.2-1=1.2)G (1.2-1= .2)

Idle= .2


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A

C

B

D E F

GH

2

3.25

1

1.2 .5

11.4

1

C (4.2-3.25)=.95

Idle = .95

D (4.2-1.2)=3E (3-.5)=2.5F (2.5-1)=1.5H (1.5-1.4)=.1Idle = .1


A (4.2-2=2.2)B (2.2-1=1.2)G (1.2-1= .2)

Idle= .2


Which station is the bottleneck? What is the effective cycle time?

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Example of Line Balancing: Determine the Efficiency of the Assembly Line

Efficiency =Sum of task times (T)

Actual number of workstations (Na) x Cycle time (C)Efficiency =

Sum of task times (T)

Actual number of workstations (Na) x Cycle time (C)

Efficiency =11.35 mins / unit

(3)(4.2mins / unit)=.901Efficiency =

11.35 mins / unit

(3)(4.2mins / unit)=.901

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Cellular Manufacturing layout

• Machines are grouped into cells and the cells function somewhat like a product layout within a larger process layout.

• Each cell in this layout is formed to produce a single parts family

• Lower WIP inventories, reduced materials handling costs, simplified production planning

• Improved on time delivery• Improved Quality.

Cellular Manufacturing layout

1 23

5 4

1 23

4

Part APart B

1 2 3 Part D

1 2

Part XPart Y

Cell # 3Cell # 4

Cell # 1 Cell # 2

Production operation

Product or materials flow

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Group Technology:Benefits

1. Better human relations

2. Improved operator expertise

3. Less in-process inventory and material handling

4. Faster production setup

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Group Technology:Transition from Process Layout

1. Grouping parts into families that follow a common sequence of steps

2. Identifying dominant flow patterns of parts families as a basis for location or relocation of processes

3. Physically grouping machines and processes into cells

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Fixed Position Layout

Question: What are our primary considerations for a fixed position layout?

Question: What are our primary considerations for a fixed position layout?

Answer: Arranging materials and equipment concentrically around the production point in their order of use.

Answer: Arranging materials and equipment concentrically around the production point in their order of use.

35

Fixed position layout or Static layout

Involves the movement of men and machines to the product which remains stationery.

Raw materials

Machines Equipments

Labour

Finished Product

(Aircraft)

36

Service facility layout

Two different types of service facility layouts exist – based on the degree of customer contact.

A) Layout which is totally designed around the customer receiving service functions. (Eg Banks, Fast food joints etc.)

B) Layout which is designed around technology, processing of materials and production (Eg. Hospitals, Restaurants etc.)

Parking AreaCasualty Department

and Inpatient Department Parking Area

Hospital Wards

Hospital wards

Hospital Wards

Suregery, Radiology, Intensive Care and Technical Services

CafetariaNuresesLounge/Offices

Doctors Lounge/Offices

Hospital Wards

Parking AreaCasualty Department

and Inpatient Department Parking Area

Entrance Exit

Ais

les/

Gan

gway

s

Par

king

Par

king

Entrance Exit

Service facility layout (Hospital Layout)

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Retail Service Layout

Goal--maximize net profit per square foot of floor space

Servicescapes– Ambient Conditions– Spatial Layout and Functionality– Signs, Symbols, and Artifacts

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Question Bowl

Which of the following are distinguishing features of CRAFT?

a. It is an optimization methodology b. Does not require any assumptions

about the layout or inter-relationships of departments

c. Can handle over 50 departmentsd. All of the abovee. None of the above

Answer: e. None of the above (It is a heuristic program, does not guarantee an optimal solution, requires layout assumptions and

can handle up to 40 departments.)

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Question BowlWhich of the following is a process that involves

developing a relationship chart showing the degree of importance of having each department located adjacent to every other department?

a. Systematic layout planning

b. Assembly-line balancing

c. Splitting tasks

d. U-shaped line layouts

e. None of the above

Answer: a. Systematic layout planning

41

Question Bowl

If the production time per day is 1200 minutes and

the required output per day is 500 units, which of

the following will be the required workstation

cycle time for this assembly line?

a. 2.4 minutes

b. 0.42 minutes

c. 1200 units

d. 500 units


Answer: a. 2.4 minutes (1200/500=2.4 minutes)

42

Question BowlYou have just finished determining the cycle time

for an assembly line to be 5 minutes. The sum of all the tasks required on this assembly is is 60 minutes. Which of the following is the theoretical minimum number of workstations required to satisfy the workstation cycle time?

a. 1 workstationb. 5 workstationsc. 12 workstationsd. 60 workstationse. None of the above

Answer: c. 12 workstations (60/5=12)

43

Question Bowl

If the sum of the task times for an assembly line

is 30 minutes, the actual number of

workstations is 5, and the workstation cycle

time is 10 minutes, what is the resulting

efficiency of this assembly line?

a. 0.00

b. 0.60

c. 1.00

d. 1.20

e. Can not be computed from the data above

Answer: b. 0.60 (30/(5x10)=0.60)

44

Question Bowl

Which of the following are ways that we can

accommodate a 20 second task in a 18

second cycle time?

a. Share the task

b. Use parallel workstations

c. Use a more skilled worker

d. All of the above


Answer: d. All of the above

45

Question Bowl

Which of the following are “ambient conditions” that

should be considered in layout design?

a. Noise level

b. Lighting

c. Temperature

d. Scent

e. All of the above

Answer: e. All of the above

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Solved Problems – OPERATIONS MANAGEMENT(Class of 2010)

Q2. A toaster assembly line has to turn out 50 toasters per hour. The tasks, their times and their immediate predecessors are shown in the table below.

(10 Marks)

Task Time, secs Imm Pred

A 28 ----B 35 AC 29 AD 32 CE 28 CF 45 CG 37 E,FH 31 D,GI 36 HJ 42 HK 49 HL 52 J,KM 37 L

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Design a line to meet the above production rate, and show your design as a diagram in the template given below, writing task letter above the work-station numbers. Remember to fill in the cycle time and efficiency boxes.

Cycle time, secs: Line efficiency, %:

Work Station: 1 2 3 4 5 6 7 8 9 10 11

Answer. Assembly Line Balancing

a) Expected Cycle Time = 1

Throughput Rate

= 60 minutes

50

= 1.2 minutes

= 72 secs. / Toaster

48

b) Now, workout the Total Task Time

c) Theoretical no of Workstations Required (for maximum efficiency)

= Total Task Time Cycle Time

Task Time, secs Imm Pred

A 28 ----B 35 AC 29 AD 32 CE 28 CF 45 CG 37 E,FH 31 D,GI 36 HJ 42 HK 49 HL 52 J,KM 37 L

Total 481

49

= 481

72

= 6.68

= 7 workstations

d) Now, draw the Precedence Diagram (Note:- Let us denote “O” as an Activity)

A28

B35

C29

F45

D32

E28

J42

H31

G37

I36

Terminal Point

M37

L52

K49

50

Note:- As there are no successor of activities B and I, we assume that all three activities B,I and M will meet at a Termination Point. So, as soon as activity M gets completed, all of them will meet at a Termination Point

e) Now, sequencing as per no of followers

Task (Activity) No. of followers A 12 B 0 C 10 D 6 E 7 F 7 G 6 H 5 I 0 J 2 K 2 L 1 M 0

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f) Now, grouping them in descending order of their follower numbers

Tasks Followers

A 12

C 10

E,F 7

D,G 6

H 5

J,K 2

L 1

B,I,M 0

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g) Now, realign them on the basis of maximum time taken

Task Time

A 28

C 29

F 45

E 28

G 37

D 32

H 31

K 49

J 42

L 52

M 37

I 36

B 35

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h) Now, we have to regroup them such that their total time does not exceed the cycle time

Workstation Task Total Time (secs) W1 A,C 57

W2 F 45

W3 E,G 65

W4 D,H 63

W5 K 49

W6 J 42

W7 L 52

W8 M 37

W9 I,B 71

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i) Diagram in the template Given

10

100

90

80

70

60

50

40

30

20

WS1 WS2

WS5

WS3

WS7

WS4

WS6

WS9

WS8

57 45 65 63 5242 3749 71

Time (secs)

Workstation (WS)

55

j) Therefore the no. of Workstations required (N) = 9

However, we found out initially, for maximum efficiency, we need 7 (approx.) Workstations

Therefore Line Efficiency = ∑ T C × N

(where ∑ T = 7 and N = 9)

C

Therefore Line Efficiency = 7 ×100 = 77.78 %

9

k) Cycle time, secs = 72

Line Efficiency, % = 77.78

56

Alternate Answer to Q.2

Task No.of Rank Order of Time Workstation Followers Task Required Grouping (descending (secs) (Time should order) not exceed

72 secs)A 12 1 A 28C 10 2 C 29E 7 3 F 45 W2F 7 3 E 28D 6 4 G 37G 6 4 D 32H 5 5 H 31J 2 6 K 49 W5K 2 6 J 42 W6L 1 7 L 52 W7B 0 8 M 37 W8I 0 8 I 36M 0 8 B 35

W1

W3

W4

W9

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Note : When there are two tasks with the same ranking, then place the task with the higher cycle time first

Diagram in the Given Template

5745

6563

4942

52

37

71

C

AF

G

E

H

DK J L M

I

B

Workstation (WS)

WS1

WS2

WS3

WS4

WS5

WS6

WS7

WS8

WS9

72 secs

tn6 facility layout

Business

disadvantages layout

physical layout

good layout

production line

process layout advantages

process layout graphic

product layout advantages

objectives facility