Facility Layout

Learning Objectives • Facility Layout and Basic Formats

• Process Layout

• Layout Planning

• Assembly Line balancing

• Service Layout

Facility Layout• 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

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

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

Interdepartmental Flow: Example• Suppose that we want to arrange the eight departments of a

toy factory to minimize the interdepartmental material handling cost. Assume that all departments have the same amount of space (say 40 feet by 40 feet) and that the building is 80 feet wide and 160 feet long.

1 3 5 7

2 4 6 8

Building Dimensions and Departments

LoadingDock

80’

160’

Interdepartmental Flow: Example

• All the material is transported in a standard-size crate by forklift truck, one crate to a truck (which constitute one “load”). Suppose that transportation costs are Re.1 to move a load between adjacent departments and Re.1 extra for each department in between.

175 50 0 30 200 20 25

0 100 75 90 80 90

17 88 125 99 180

20 5 0 25

0 180 187

374 103

7

1 2 3 4 5 6 7 8

1

2

3

4

5

6

7

8

1

2

3

4

5

6

7

8

Department

Shipping & receiving

Plastic molding & stamping

Metal forming

Sewing department

Small toy assembly

Large toy assembly

Painting

Mechanism assembly

ActivityFlow between departments (No of moves)

Interdepartmental Flow: Example

175 50 0 60 400 60 75

0 100 150 180 240 270

17 88 125 198 360

20 5 0 50

0 180 187

374 103

7

1

2

3

4

5

6

7

8

1 2 3 4 5 6 7 8

Cost Matrix – First Solution

Total Cost = Rs. 3,474

Interdepartmental Flow: Example

• Revised Interdepartmental Flow

1 3 5 7

2 6 4 8

Interdepartmental Flow: Example

175 50 0 60 200 60 75

0 200 150 90 240 270

17 88 125 198 360

20 5 0 25

0 180 187

748 206

7

1

2

3

4

5

6

7

8

1 2 3 4 5 6 7 8 Net cost change

- Rs 200

+ 10

- 25

+ Rs 374 + Rs 103

+ Rs 262Total cost : Rs. 3,736

Cost Matrix – Second Solution

Process Layout: CRAFT Approach(Computerized Relative Allocation of Facilities Technique)

• CRAFT is a computerized layout program.• Initial inputs required are ; - Load matrix & distance matrix. • It compares 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

Process Layout: Systematic Layout Planning

• Numerical flow of items between departments – Can be impractical to obtain– Does not account for the qualitative factors that may

be crucial to the placement decision• Systematic Layout Planning

– Accounts for the importance of having each department located next to every other department

– Is also guided by trial and error• Switching departments then checking the results of the

“closeness” score

Systematic Layout Planning: Example

• Consider a five-department problem involving laying out a floor of a department store.

Value Closeness Line code

Numerical weights

A Absolutely necessary 16

E Especially important 8

I Important 4

O Ordinary closeness OK 2

U Unimportant 0

X Undesirable -80

Code Reason

1 Type of customer

2 Ease of supervision

3 Common personnel

4 Contact necessary

5 Share same space

6 Psychology

Table A Table B

Systematic Layout Planning: Example

FromTo

Area (sq. ft.)

2 3 4 5

1. Credit departmentI U E U

1006 -- 4 --

2. Toy departmentU I A

400-- 1 1,6

3. Wine departmentU X

300-- 1

4. Camera departmentX

1001

5. Candy department 100

Table C: Relationship Chart (based on Table A & B)

Letter : Closeness rating Number : Reason for rating

1

24

3

5A

UUE

II

Initial relationship diagram (based on tables A and C)

5 2 4

3 1

Initial layout based on relationship diagram (ignoring space & building constraints)

235 1 4

50 ft.

20 ft.

Final layout adjusted by square footage and building size

Product Layout

• Processes/work stations arranged in sequence of activities required to produce the product/service (Assembly Line).– Use for high volume, standardized products and

services– WIP and handling of materials/customers is

minimized– Equipment is specialized, capital intensive– Output is dependent on the slowest work station– The “line” must be balanced for effectiveness.

Product Layout

• Some featuresSpecialized equipment High capital intensity & wide use of automationProcessing rates are fasterMaterial handling costs are lowerLess space required for inventoriesLess volume or design flexibility

Designing Product Layouts

• Step 1: Identify tasks & immediate predecessors• Step 2: Determine the desired output rate• Step 3: Calculate the cycle time• Step 4: Compute the theoretical minimum number of workstations• Step 5: Assign tasks to workstations (balance the line)• Step 6: Compute efficiency, idle time & balance delay

Assembly Line Balancing

1. Precedence diagram: circles=tasks, arrows show the required sequence.

2. Determine cycle time:

3. Determine required workstations (theoretical minimum)

4. Set rules for assigning tasks (number of following tasks, longest task time)

C = . Production time per day . Required output per day (in units)

Nt = . Sum of task times (T) . Cycle time (C)

Assembly Line Balancing

5. Assign tasks to first workstation, using rules and staying within cycle time. Repeat for following workstations until all tasks are assigned.

6. Evaluate line efficiency:

7. Rebalance if efficiency is not satisfactory.

Efficiency = . Sum of task times (T) . Actual no of workstations (Na) X Workstation cycle time (C)

Assembly Line Balancing: Example• Vicki’s Pizzeria is producing Pizzas. 60 units are required to be produced

every hour. The assembly steps and task times are shown below. Find the balance that minimizes the number of workstations, subject to cycle time and precedence constraints.

Example : 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

Assembly Line Balancing: Example

Assembly Line Balancing: Example

• Step 2: Determine output rate– Vicki needs to produce 60 pizzas per hour

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

complete its tasks

Cycle time = Prod time / Output = {60 min/hrX60 sec/min}/60 min/hr = 60 sec/unit.

Assembly Line Balancing: Example

• Step 4: Compute the theoretical minimum number of stations– Nt = number of stations needed to achieve 100% efficiency

(every second is used)

Nt = Sum of task times/Cycle time = 165/60 = 2.75 or 3 stations

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

Assembly Line Balancing: Example• Step 5: Assign tasks to workstations

– Start at the first station & choose the longest eligible task following precedence relationships

– Continue adding the longest eligible task that fits without going over the desired cycle time

– When no additional tasks can be added within the desired cycle time, begin assigning tasks to the next workstation until finished

Workstation 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

Assembly Line Balancing: Example

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

by total time

Efficiency (%) = Sum of task times/ Na X C = 165 / 3 x 60 = 91.7 %

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

Balance delay = 100 – 91.7 % = 8.3 %.

Group Technology (Cellular) Layout

• GT (or cellular) layout allocates dissimilar machines into cells to work on products that have similar shapes and processing requirements.

• Widely used in metal fabricating, computer chip manufacture, and assembly work.

• GT has the advantage of bringing the efficiencies of a product layout to a process layout environment. These advantages include;

1. Better human relations2. Improved operator expertise3. Less in-process inventory and material handling.4. Faster production setup

Group Technology (Cellular) Layout: Steps1. Grouping parts into families that follow a common sequence

of steps.

Group Technology (Cellular) Layout: Steps2. Identifying dominant flow patterns of parts families as a basis

for location or relocation of processes.

Group Technology (Cellular) Layout: Steps3. Physically grouping machines and processes into cells.

Fixed Position Layout

• The position of a product or customer is fixed; and materials, equipment, workers, and other resources are transported to and from the product or customer.

• Usually used because product movement is difficult (ship building) or for convenience (on-site repair).

• This is often managed through Project Management

Retail Service Layout

• The objective is to maximize net profit per square foot of store space (as found in banks, store and restaurants).

• The term servicescape is coined in this regard to refer to the physical surroundings in which the service takes place and how these surroundings affect customers and employees.

• It has three elements which must be considered: - Ambient Conditions – Refers to background characteristics

such as noise level, music, lighting, temperature, and scent that can affect employee performance and morale as well as customers perceptions of the service.

Retail Service Layout

- Spatial layout and functionality – Refers to planning the circulation path of the customers and grouping the merchandise.

- Signs, Symbols and Artifacts – Refer to the parts of the service that have social significance.

Office Layout

• Office Layout Considerations: - Human interaction and communication are the primary factors

in designing office layouts. - The present trend is towards more Open offices, with

personal work spaces separated by low divider walls. - Layouts need to account for physical environment and

psychological needs of the organization. - One key layout trade-off is between proximity and privacy. - Flexible layouts incorporating “office landscaping” help to

solve the privacy issue in open office environments.