Transcript 15.2 Single - Factor (One - Way) Analysis of Variance
Facilities Layout
Facility Layout
Facility Layout
• the arrangement of everything within and around
buildings;
• the configuration of departments, work centers and
equipment, with particular emphasis on the movement of work (customers or materials) through the system.
Facility Layout decisions arise when:
• Designing new facilities • Redesigning existing facilities
Importance of Layout Decisions
Requires substantial investments of money and effort
Involves long-term commitments
Has significant impact on cost and efficiency of short-term operations
The Need for Layout Planning
• Inefficient operations – High cost – Bottlenecks • Accidents or safety hazards • Changes in product or service design • Introduction of new products or services
The Need for Layout Planning
• Changes in output volume or product mix • Changes in methods or equipment • Changes in environmental or other legal
requirements
• Morale problems
Layout Strategy aims to..
Develop an economical layout which will meet the requirements of:
product design and volume (product strategy)
process equipment and capacity (process strategy)
quality of work life (human resource strategy)
building and site constraints (location strategy)
Layout Design Objectives
• Basic Objective – Facilitate a smooth flow of work, material, and information
through the system
• Supporting objectives – Facilitate product or service quality – Use workers and space efficiently – Avoid bottlenecks – Minimize material handling costs – Eliminate unnecessary movement of workers or material – Minimize production time or customer service time – Design for safety and security
Layout Design Objectives
•
Supporting objectives
– Facilitate communication and interaction between workers,
between workers and their supervisors, or between workers and customers
– Facilitate the entry, exit, and placement of material, products, or
people
– Encourage proper maintenance activities – Provide a visual control of operations or activities – Provide flexibility to adapt to changing conditions – Maximize customer satisfaction – Improve employee morale – Improve customer/client interaction
Basic Types of Layouts
Process Layout (Functional Layout)
Product Layout
Fixed Position Layout
Combination Layouts
Process (Functional) Layout
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Process (Functional) Layout
Used with process-focused (non repetitive) processes
Layout that can handle varied processing requirements
Machines are grouped according to the process they perform. E.g. All x-ray machines in the same area
Used for intermittent processing (job shop or batch shop)
Low raw material and finished goods inventory, high WIP inventory
Process Layouts
Used for Intermittent processing (low volume, high variety) Job Shop or Batch Dept. A Dept. B Dept. C Dept. D Dept. E Dept. F
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Process 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
Emergency Room Layout
E.R.Triage room
Patient A broken leg Patient B - erratic pacemaker Hallway
E.R. beds
Pharmacy Billing/exit
Manufacturing Process Layout
Lathe Department L L Milling Department M M D Drilling Department D D D M M D D D D L L G G G P L L L L G G Grinding Department G P Painting Department L L Receiving and Shipping A A Assembly A
Manufacturing Process Layout
Lathe Department L L Milling Department M M D Drilling Department D D D M M D D D D L L G G G P L L L L G G Grinding Department G P Painting Department L L Receiving and Shipping A A Assembly A
Manufacturing Process Layout
Lathe Department L L Milling Department M M D Drilling Department D D D M M D D D D L L G G G P L L L L G G Grinding Department G P Painting Department L L Receiving and Shipping A A Assembly A
Process Layout
Design places departments with large flows of material or people close to each other
Process Layout: Advantages
Can handle a variety of processing requirements
Not particularly vulnerable to equipment failures
General-purpose equipment is often less costly than the specialized equipment used in product layouts
It is possible to use individual incentive plans
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Process Layout: Disadvantages
In-process inventory costs can be high
Challenging routing and scheduling
Equipment utilization rates are low
Material handling slow and inefficient
Complexities often reduce span of supervision
Special attention for each product or customer
Accounting and purchasing are more involved
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Product Layout
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Product Layout
Linear arrangement of workstations to produce a specific product
Layout that uses standardized processing operations to achieve smooth, rapid, high volume flow
Requires standardized product, high production volume, stable production quantities
High equipment utilization, high investment in justified equipment, large raw material and finished goods inventories
Raw materials or customer Station 1
Product Layout
sequential Station 2 Station 3 Station 4 Finished item Material and/or labor Material and/or labor Material and/or labor Material and/or labor Used for Repetitive or Continuous Processing
Product Layout:A U-Shaped Production Line
In 1 2 3 4 5 Workers 6 Out 10 9 8 7
Mixed Model Assembly Lines
Produce multiple models in any order on one assembly line
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Product Layout: Advantages
• High rate of output • Low unit cost • Labor specialization • Low material handling cost per unit • High utilization of labor and equipment • Established routing and scheduling • Routine accounting, purchasing, and inventory
control
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Product Layout: Disadvantages
• Creates dull, repetitive jobs • Poorly skilled workers may not maintain equipment or
quality of output
• Fairly inflexible to changes in volume or product or
process design
• Highly susceptible to shutdowns • Preventive maintenance, capacity for quick repair and
spare-parts inventories are necessary expenses
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Product Layout
Design minimizes line inbalance and delay between work stations.
Comparison Of Product And Process Layouts (1 of 2)
1.
Description 2. Type of Process 3. Product 4. Demand 5. Volume 6. Equipment 7. Workers PRODUCT LAYOUT Sequential arrangement of machines Continuous, mass production, mainly assembly Standardized made to stock Stable High Special purpose Limited skills PROCESS LAYOUT Functional grouping of machines Intermittent, job shop batch production, mainly fabrication Varied, made to order Fluctuating Low General purpose Varied skills
Comparison Of Product And Process Layouts (2 of 2)
8.
Inventory 9. Storage space 10. Material handling 11. Aisles 12. Scheduling 13. Layout decision 14. Goal 15. Advantage PRODUCT LAYOUT Low in-process, high finished goods Small Fixed path (conveyor) Narrow Part of balancing Line balancing Equalize work at each station Efficiency PROCESS LAYOUT High in-process, low finished goods Large Variable path (forklift) Wide Dynamic Machine location Minimize material handling cost Flexibility
Fixed Position Layouts
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Fixed Position Layouts
– – – –
Layout in which the product or project remains stationary (cannot be moved), and workers, materials, and equipment are moved as needed Generally highly skilled labor is needed Often low fixed costs Typically high variable costs
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Combination Layouts
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Combination Layouts
Some operational environments use a combination of the three basic layout types:
Hospitals
Supermarket
Shipyards
Some organizations are moving away from process layouts in an effort to capture the benefits of product layouts
Cellular manufacturing
Flexible manufacturing systems
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Cellular Layout
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Cellular Layout
Layout in which machines are gruped into a cell that can process items that have similar processing requirements.
Cellular Layout - Work Cells
• Special case of product-oriented layout - in what is
ordinarily a process-oriented facility
• Consists of different machines brought together to
make a product family
• Example: An assembly line set up to produce 3000
identical parts in a job shop
Group Technology Schemes Enable Grouping of Parts
Parts Families
A family of similar parts A family of related grocery items
Original Process Layout
Assembly 4 1 A 6 7 5 2 10 3 B C Raw materials 8 11 9 12
Revised Cellular Layout
8 4 Cell 1 2 Assembly 10 9 12 Cell 2 6 1 3 A B C Raw materials 5 Cell 3 11 7
Automated Manufacturing Cell
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A Comparison of Functional and Cellular Layouts
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Flexible Manufacturing System (FMS)
A group of machines designed to handle intermittent processing requirements and produce a variety of similar products (automated machining and material handling systems)
• Includes supervisory computer control,
automatic material handling, and robots or other automated processing equipment
• It is a more automated version of cellular
manufacturing
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Flexible Manufacturing Systems
Automated machining operations
Automated material handling
Automated tool changers
Computer controlled system
Designed around size of parts processed & average processing time for parts
Can process wide variety of items quickly
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Flexible Manufacturing System
CNC Machine
Finished goods
Computer control room Terminal Automatic tool changer CNC Machine Pallet Parts
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FMS Layouts
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FMS Layouts
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Service Layout
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Service Layouts
Service layouts can be categorized as: product, process, or fixed position
Service layout requirements are somewhat different due to such factors as:
Degree of customer contact
Degree of customization
Common service layouts:
Warehouse and storage layouts
Retail layouts
Office layouts
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Service Layouts
Usually process layouts due to customers needs
Minimize flow of customers or paperwork
Retailing tries to maximize customer exposure to products
Computer programs consider shelf space, demand, profitability
Layouts must be aesthetically pleasing
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Retail Service Layout
• Goal--maximize net profit per square foot of floor
space
• Goal– maximize product exposure to customers • Servicescapes To Accompany Russell and Taylor, Operations Management, 4th Edition, 2003 Prentice-Hall, Inc. All rights reserved.
Office Layout
• Design positions people, equipment, & offices
for maximum information flow
• Arranged by process or product – Example: Payroll dept. is by process • Relationship chart used • Examples – Insurance company – Software company © 1995 Corel Corp.
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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
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A Good Service Layout (Servicescape) Considers
• Ambient conditions -
background characteristics such as lighting, sound, smell, and temperature.
• Spatial layout and functionality
- which involve customer circulation path planning
• Signs, Symbols, and Artifacts
- characteristics of building design that carry social significance
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Layout Methodology
Process Layout Methodology Product Layout Methodology
Process Layout Methodology
Designing Process Layouts
• The main issue in designing process layouts
concerns the relative placement of the departments
• Measuring effectiveness – A major objective in designing process layouts is
to minimize transportation cost, distance, or time
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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, minimizing costs (materials handling costs)
Information Requirements
In designing process layouts, the following information is required:
– A list of departments to be arranged and their dimensions – A projection of future workflows between the pairs of work
centers
– The distance between locations and the cost per unit of
distance to move loads between them
– The amount of money to be invested in the layout – A list of any special considerations – The location of key utilities, access and exit points, etc. To Accompany Russell and Taylor, Operations Management, 4th Edition, 2003 Prentice-Hall, Inc. All rights reserved.
Steps in Developing a Process Layout
Construct a “from-to matrix”
Determine space requirements for each department
Develop an initial schematic diagram
Determine the cost of this layout
By trial-and-error (or more sophisticated means), try to improve the initial layout
Prepare a detailed plan that evaluates factors in addition to transportation cost
Designing Process Layouts
Methods of Designing Process Layouts
Block Diagramming
Minimize nonadjacent loads Use when quantitative data is available
Relationship Diagramming
Based on location preference between areas
Use when quantitative data is not available
Block Diagramming (1 of 7)
Create load summary chart
Calculate composite (two way) movements
Develop trial layouts minimizing number of nonadjacent loads
Block Diagramming (2 of 7)
Load Summary Chart FROM/TO DEPARTMENT
Department 1 2 3 4 Composite
2
3 2
1
1
4
4 3 2 5 1 2 3 4 5 — 60
Movements
200 loads 150 loads 110 loads 100 loads 60 loads 100 — 50 200 — 100 50
Composite
3
5 2
3
1
1
5 4 4 5 50 40 —
5
50 60 —
Movements
50 loads 50 loads 40 loads 0 loads 0 loads
Block Diagramming (3 of 7) Load Summary Chart FROM/TO
Department 1
DEPARTMENT 1
2 3 4
2
5
3
Composite
2
3 2
1
1
4
4 3 2 5 1 2 3 4 5 — 60
Movements
200 loads 150 loads 110 loads 100 loads 60 loads 100 — 50 — 100 50
Composite
3
5 2
3
1
1
5 4 4 5 50 40 — 5 50 60 —
Movements
50 loads 50 loads 40 loads 0 loads 0 loads
Block Diagramming (4 of 7) Composite
2
3 2
1
1
4
4 3 2 5 110 Load Summary Chart FROM/TO Department 1 2 3 4 5
Movements
200 loads 150 loads 110 loads 100 loads 60 loads 1 — 60 2 100 — 200 1 2 3 150 4 50 4 50 200 — 60 50 40 — — 5 5 50 50 60 40 3 50
Composite
3
5 2
3
1
1
5 4 4 5
Movements
50 loads 50 loads 40 loads 0 loads 0 loads
Block Diagramming (5 of 7) Composite
2
3 2
1
1
4
4 3 2 5 Load Summary Chart FROM/TO Department 1 2 3 4 5 1 — 60 150 1 2 2 3 4 200 100 — 100 50 Grid 2 50 200 — 110 50 40 — — 3 50 60 50 40 4 5 60
Movements
200 loads 150 loads 110 loads 100 loads 60 loads
Composite
3
5 2
3
1
1
5 4 4 5
Movements
50 loads 50 loads 40 loads 0 loads 0 loads
Block Diagramming (6 of 7)
(a) Initial block diagram 1 2 3 4 5
Block Diagramming (7 of 7)
(a) Initial block diagram ( b) Final block diagram 1 2 3 4 5 1 3 2 4 5
Relationship Diagramming (Systematic Layout Planning) (1 of 2)
Used when quantitative data is not available
Muther’s grid displays preferences
Denote location preferences with weighted lines
Relationship Diagramming (Systematic Layout Planning) (2 of 2)
• 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
Relationship Diagramming Example
Production Offices O U A I A E I O U X Absolutely necessary Especially important Important Okay Unimportant Undesirable Stockroom O E A X A Shipping and receiving U U O U Locker room O O Toolroom
Relationship Diagrams
( a) Relationship diagram of original layout Offices Stockroom Locker room Toolroom Shipping and receiving Production Key: A E I O U X
Relationship Diagrams
( b) Relationship diagram of revised layout Stockroom Offices Toolroom Production Shipping and receiving Locker room Key: A E I O U X
Product Layout Methodology
Designing Product Layouts
Suitable for production/assembly lines
Jobs are divided into work elements
Precedence diagram of tasks is developed
Work elements are assigned to workstations by trying to balance the amount work of each workstation
Product Layout: Line Balancing
Line Balancing is the process of assigning tasks to workstations in such a way that the workstations have approximately equal time requirements. X Why is line balancing important?
• To allow us to use labor and equipment more
efficiently.
• To avoid fairness issues that arise when one
workstation must work harder than another.
Product Layout
Work 1 Work Station Station 3 2 Belt Conveyor 4 Work Station 5 Office Note: 5 tasks or operations; 3 work stations
Line Balancing Concepts (1 of 2)
Precedence diagram
Network showing order of tasks and restrictions on their performance
Cycle time
Maximum time allowed at each workstation to complete its set of tasks on a unit
Line Balancing Concepts (2 of 2)
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?
Station 1 Station 2 Station 3
Minutes per Unit
6 7 3
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.
Line Balancing
Cycle time example
C d =
production time available desired output rate
C d =
(8 hours x 60 minutes / hour) (120 units)
C d
480 = = 4 minutes 120
Flow Time vs Cycle Time
Cycle time = max time allowed at each workstation to complete its set of tasks on a unit. (establishes the output rate of a line)
Flow time = time to complete all stations 1 4 minutes 2 4 minutes 3 4 minutes Flow time = 4 + 4 + 4 = 12 minutes Cycle time = max (4, 4, 4) = 4 minutes
Line Balancing Objectives
maximize efficiency - minimize the number of work stations
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How Many Workstations are Needed?
• The required number of workstations is a function of – Desired output rate – Our ability to combine tasks into a workstation • Theoretical minimum number of stations
N
min
t
Cycle time where
N
min
t
theoretica l minimum Sum of task time s number of stations To Accompany Russell and Taylor, Operations Management, 4th Edition, 2003 Prentice-Hall, Inc. All rights reserved.
Efficiency
E
=
Efficiency of the Line i i
= 1
nC a t i
Minimum number of workstations
N
=
i i
= 1
t i C d
where
t i j n C a C d
= completion time for element
i
= number of work elements = actual number of workstations = actual cycle time = desired cycle time
Balance Delay
• Balance delay (percentage of idle time of a line) Balance Delay Idle time per cycle
N actual
Cycle time where
N
min Actual number of stations Efficiency 100% Balance Delay To Accompany Russell and Taylor, Operations Management, 4th Edition, 2003 Prentice-Hall, Inc. All rights reserved.
Line Balancing Process
1. Draw and label a precedence diagram.
2. Estimate task times 3. Calculate the desired cycle time required for the line.
4. Calculate the theoretical minimum number of workstations.
5. Group tasks into workstations, recognizing cycle time and precedence constraints.
6. Calculate the efficiency of the line.
7. Stop if theoretical minimum number of workstations on an acceptable efficiency level reached. If not, go back to step 4.
Precedence Diagram
• Precedence diagram – A diagram that shows elemental tasks and their
precedence requirements
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Assigning Tasks to Workstations
Some Heuristic (Intuitive) Rules:
– 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.
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Line Balancing (Example 1)
A B C D WORK ELEMENT Press out sheet of fruit Cut into strips Outline fun shapes Roll up and package PRECEDENCE — A A B, C TIME (MIN) 0.1
0.2
0.4
0.3
Line Balancing (Example 1)
A B C D WORK ELEMENT Press out sheet of fruit Cut into strips Outline fun shapes Roll up and package PRECEDENCE — A A B, C TIME (MIN) 0.1
0.2
0.4
0.3
B 0.2
0.1
A D 0.3
C 0.4
Line Balancing (Example 1)
A B C D WORK ELEMENT Press out sheet of fruit Cut into strips Outline fun shapes Roll up and package PRECEDENCE — A A B, C TIME (MIN) 0.1
0.2
0.4
0.3
C d
0.2
6,000 units B 2400 = = = 0.4 minute 6000
N
0.1
A D 0.3
0.1 + 0.2 + 0.3 + 0.4
= = = 2.5 workstations 0.4
1.0
0.4
C 0.4
3 workstations
Line Balancing (Example 1)
A B C D WORK ELEMENT Press out sheet of fruit Cut into strips Outline fun shapes Roll up and package PRECEDENCE — A A B, C TIME (MIN) 0.1
0.2
0.4
0.3
B 0.2
0.1
A D 0.3
C d N
= 0.4
= 2.5
C 0.4
Line Balancing (Example 1)
WORKSTATION ELEMENT REMAINING TIME REMAINING ELEMENTS 0.1
A B 0.2
D 0.3
C 0.4
C d N
= 0.4
= 2.5
Line Balancing (Example 1)
WORKSTATION 1 ELEMENT A REMAINING TIME 0.3
REMAINING ELEMENTS B, C 0.1
A B 0.2
D 0.3
C d N
= 0.4
= 2.5
C 0.4
Line Balancing (Example 1)
WORKSTATION 1 ELEMENT A B REMAINING TIME 0.3
0.1
REMAINING ELEMENTS B, C C, D
C d N
= 0.4
= 2.5
0.1
A B 0.2
D 0.3
C 0.4
WORKSTATION 1 2
Line Balancing (Example 1)
ELEMENT A B C REMAINING TIME 0.3
0.1
0.0
REMAINING ELEMENTS B, C C, D D
C d N
= 0.4
= 2.5
0.1
A B 0.2
D 0.3
C 0.4
WORKSTATION 1 2 3
Line Balancing (Example 1)
ELEMENT A B C D REMAINING TIME 0.3
0.1
0.0
0.1
REMAINING ELEMENTS B, C C, D D none B 0.2
C d N
= 0.4
= 2.5
0.1
A D 0.3
C 0.4
WORKSTATION 1 2 3
Line Balancing (Example 1)
ELEMENT A station 1 B A, B C 0.3 D minute REMAINING TIME station 2 0.3
0.0
0.4 0.1
minute REMAINING ELEMENTS station 3 B, C D C, D D 0.3 none minute B 0.2
C d N
= 0.4
= 2.5
0.1
A D 0.3
C 0.4
WORKSTATION 1 2 3
Line Balancing (Example 1)
ELEMENT A station 1 B A, B C 0.3 D minute REMAINING TIME station 2 0.3
0.0
0.4 0.1
minute REMAINING ELEMENTS station 3 B, C D C, D D 0.3 none minute B 0.2
C d N
= 0.4
= 2.5
E
0.
1 A 3(0.4) 1.0
C 1.2
0.4
D 0.3
Line Balancing (Example 2)
• You’ve just been assigned the job a setting up an
electric fan assembly line with the following tasks: Task
A B C D E F G H
Time (Mins) Description
2 Assemble frame 1 3.25
1.2
Mount switch Assemble motor housing Mount motor housing in frame 0.5
1 1 1.4
Attach blade Assemble and attach safety grill Attach cord Test
Predecessors
None A None A, C D E B F, G
Line Balancing (Example 2) Structuring the Precedence Diagram
Task Predecessors
A None B C D A None A, C
Task Predecessors
E D F G H E B E, G A B G H C D E F
Line Balancing (Example 2) Precedence Diagram
Question: Which process step defines the maximum rate of production?
2 A 1 B 1 G 1.4
H C 3.25
D 1.2
E .5
F 1
Answer: Task C is the cycle time of the line and therefore, the maximum rate of production.
Line Balancing (Example 2) Determine Cycle Time
Question: Suppose we want to assemble 100 fans per day. What would our cycle time have to be? Answer:
Production time per period
Required Cycle Time,
C = Required output per period 420 mins / day C = 100 units / day = 4.2 mins / unit
Line Balancing (Example 2) Determine Theoretical Minimum Number of Workstations
Question: What is the theoretical minimum number of workstations for this problem? Answer:
Theoretical Min. Number of Workstations,
N t Sum of task times (T) Cycle time (C) 11.35 mins / unit = 2.702, or 3 4.2 mins / unit
2 A C 3.25
1 B D 1.2
Station 1
Line Balancing (Example 2)
1 G E .5
F 1 1.4
H Station 2
Task
A C D B E F G H
Followers
6 4 3 2 2 1 1 0
Time (Mins)
2 3.25
1.2
1 0.5
1 1 1.4
Station 3
2 A C 3.25
1 B 1 G D 1.2
E .5
Station 1 A (4.2-2=2.2) F 1 1.4
H Station 2
Task
A C D B E F G H
Followers
6 4 3 2 2 1 1 0
Time (Mins)
2 3.25
1.2
1 0.5
1 1 1.4
Station 3
2 A C 3.25
1 B 1 G D 1.2
E .5
Station 1 A (4.2-2=2.2) B (2.2-1=1.2) F 1 1.4
H Station 2
Task
A C D B E F G H
Followers
6 4 3 2 2 1 1 0
Time (Mins)
2 3.25
1.2
1 0.5
1 1 1.4
Station 3
2 A C 3.25
1 B 1 G D 1.2
E .5
Station 1 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
F 1 1.4
H Station 2
Task
A C D B E F G H
Followers
6 4 3 2 2 1 1 0
Time (Mins)
2 3.25
1.2
1 0.5
1 1 1.4
Station 3
2 A C 3.25
1 B 1 G D 1.2
E .5
Station 1 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
F 1 1.4
H
Task
A C D B E F G H Station 2 C (4.2-3.25)=.95
Followers
6 4 3 2 2 1 1 0
Time (Mins)
2 3.25
1.2
1 0.5
1 1 1.4
Station 3
2 A C 3.25
1 B 1 G D 1.2
E .5
Station 1 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
F 1 1.4
H
Task
A C D B E F G H Station 2 C (4.2-3.25)=.95
Followers
6 4 3 2 2 1 1 0
Time (Mins)
2 3.25
1.2
1 0.5
1 1 1.4
Station 3 Idle = .95
2 A C 3.25
1 B 1 G D 1.2
E .5
Station 1 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
F 1 1.4
H
Task
A C D B E F G H Station 2 C (4.2-3.25)=.95
Followers
6 4 3 2 2 1 1 0
Time (Mins)
2 3.25
1.2
1 0.5
1 1 1.4
Station 3 D (4.2-1.2)=3 Idle = .95
2 A C 3.25
1 B 1 G D 1.2
E .5
Station 1 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
F 1 1.4
H
Task
A C D B E F G H Station 2 C (4.2-3.25)=.95
Followers
6 4 3 2 2 1 1 0
Time (Mins)
2 3.25
1.2
1 0.5
1 1 1.4
Station 3 D (4.2-1.2)=3 E (3-.5)=2.5
Idle = .95
2 A C 3.25
1 B 1 G D 1.2
E .5
Station 1 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
F 1 1.4
H
Task
A C D B E F G H Station 2 C (4.2-3.25)=.95
Followers
6 4 3 2 2 1 1 0
Time (Mins)
2 3.25
1.2
1 0.5
1 1 1.4
Station 3 D (4.2-1.2)=3 E (3-.5)=2.5
F (2.5-1)=1.5
Idle = .95
2 A C 3.25
1 B D 1.2
1 G E .5
F 1 1.4
H
Task
A C D B E F G H
Followers
6 4 3 2 2 1 1 0
Time (Mins)
2 3.25
1.2
1 0.5
1 1 1.4
Station 1 Station 2 Station 3 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) C (4.2-3.25)=.95
D (4.2-1.2)=3 E (3-.5)=2.5
F (2.5-1)=1.5
H (1.5-1.4)=.1
Idle= .2
Idle = .95
Idle = .1
Which station is the bottleneck? What is the effective cycle time?
Efficiency of the Assembly Line
Sum of task times (T) Efficiency = Actual number of workstations (Na) x Cycle time (C) Efficiency = 11.35 mins / unit (3)(4.2mins / unit) =.
901
Balance Delay (Percent Idle Time)
Percent idle time = Idle time per cycle (N)(CT) = (.2+.95+.1)/3(4.2) = .099
Efficiency = 1 – Percent idle time
Parallel Workstations
1 min.
30/hr.
1 min.
30/hr.
2 min.
30/hr.
Bottleneck
30/hr.
2 min.
1 min.
60/hr.
1 min.
Parallel Workstations
30/hr.
2 min.
30/hr.
30/hr.
1 min.
30/hr.
1 min.
60/hr.
Computerized Line Balancing
Use heuristics to assign tasks to workstations
Ranked positional weight
Longest operation time
Shortest operation time
Most number of following tasks
Least number of following tasks
Balancing U-Shaped Lines
Precedence diagram: A B C Cycle time = 12 min D E
Balancing U-Shaped Lines
Precedence diagram: A B C Cycle time = 12 min D ( a) Balanced for a straight line A,B C,D E 9 min 12 min 3 min 24 Efficiency = = = .6666 = 66.7 % 3(12) 24 36 E
Balancing U-Shaped Lines
Precedence diagram: A B C Cycle time = 12 min D E (a) Balanced for a straight line A,B C,D E 9 min 12 min 3 min 24 Efficiency = = = .6666 = 66.7 % 3(12) 24 36 (b) Balanced for a U-shaped line A,B C,D E 24 Efficiency = = = 100 % 2(12) 24 24 12 min 12 min