Description
Where the production facilities should be located? What the layout and characteristics of the facilities should be?
Facilities Planning
• How much long range capacity is needed? • When additional capacity is needed? • Where the production facilities should be located? • What the layout and characteristics of the facilities should be?
FACILITY LOCATION
• Once a firm has decided to open a new facility or relocate an existing facility, it must decide where that facility should be located • Facility location problem involves the evaluation of various sites for a new facility. • There are several factors that influence the Facility Location Decision:
Factors Related to Resources
• • • • • • Labour availability, Labour cost, Labour Skills; Materials Availability, Material cost, material quality; Equipment availability, Equipment Cost; Land availability, Land suitability, Land cost; Energy availability, energy cost; Water availability, water quality, water cost.
Factors Related to the Infrastructure &Market
• Availability of Financial Institutions, Strength of Financial Institutions • Government Stability, Government taxes, Import and Export restrictions. • Quality of life, Cultural issues, • Environmental regulations, Transportation availability, Transportation cost, Power • Closeness to the market • Competitors’ size, strength and attitude in that region.
Analytical techniques
• There are many analytical techniques that can be used in facility location decision. • Some of these are: 1) Factor Rating 2) Cost-Profit-Volume analysis 3) Center of Gravity Method, and 4) Transportation and Simulation Models.
Major considerations in Layout Decisions
• Reduce unnecessary or non-value adding activities such as material handling • Reduce inventory and rework • Communication • Safety and security of employees customers and resources • Availability and utilization of space
LAYOUT TYPES
• Different layouts present different managerial challenges • Different layouts present different opportunities to satisfy customers’ needs • A strategic perspective is required to make the right layout choices
– – – – – Fixed-position Product Process Cellular Hybrid (some combination of others)
7
Basic Production Layout Formats
• Fixed-Position Layout – the product remains at one location and equipments are moved to the product • Process Layout (also called job-shop or functional layout) Similar equipments are grouped together • Product Layout (also called line layout)- Equipments are arranged as per the sequence of operations by which the product is made. • Group Technology (Cellular) Layout- Groups dissimilar machines into work centers to work on products that have similar shapes and processing requirements
Fixed-Position Layouts
• Product remains in a fixed position, and the personnel, material and equipment come to it • Used when the product is very bulky, large, heavy or fragile
Fixed product layout
Process (Job Shop) Layouts
• Equipment that perform similar processes are grouped together • Used when the operations system must handle a wide variety of products in relatively small volumes (i.e., flexibility is necessary)
Characteristics of Process Layouts
• • • • • • General-purpose equipments are used Frequent changeovers Material flow is intermittent Operators are highly skilled Technical supervision is required Planning, scheduling and controlling functions are challenging • Production time is relatively long • In-process inventory is relatively high
Materials Handling
• The central focus of most manufacturing layouts is to minimize the cost of processing, transporting, and storing materials throughout the production system. • Materials used in manufacturing include:
– – – – – – Raw material Purchased components Work-in-progress Finished goods Packaging material Maintenance, repair, and operating supplies
Computerized Techniques for Layout Planning Heuristics
• CRAFT ( Computerized Relative Allocation of Facilities Technique) • CORELAP ( Computerized Relationship Layout Planning) • ALDEP ( Automated Layout Design Program)
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 The “best” locations for each department, where best means maximizing flow, which minimizing costs
• Determine
–
Process 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
EXAMPLE : INITIAL LAYOUT
Volume
Sand Sand Turn Turn 100 Asm 325 10 Pnt 250 15 Rip 2 0 Rout 300 0 RfP 200 0 Drl 75 5
Current Layout
Sanding Ripsaw
Asm
Pnt Rip Rout RfP Drl
275
25
150
100
100 200
0
0 350 100
175
100 100 0 0
Turning
Assembly Paint
Router
Rough Plane Drilling
Distance
Sand Sand Turn Asm Pnt Rip Rout RfP Drl Turn 1 Asm 2 1 Pnt 3 2 1 Rip 1 2 3 4 Rout 2 1 2 3 1 RfP 3 2 1 2 2 1 Drl 4 3 2 1 3 2 1
Volume*Distance
Sand Sand Turn Asm Pnt Rip Rout RfP Drl Turn 100 Asm 650 10 Pnt 750 30 275 Rip 2 0 75 600 Rout 600 0 200 300 200 RfP 600 0 0 0 700 100 Drl 300 15 350 100 300 0 0
Total
6257
EXAMPLE : REVISED LAYOUT
Volume
Sand Sand Turn Turn 100 Asm 325 10 Pnt 250 15 Rip 2 0 Rout 300 0 RfP 200 0 Drl 75 5
Revised Layout
Turning Ripsaw
Asm
Pnt Rip Rout RfP Drl
275
25
150
100
100 200
0
0 350 100
175
100 100 0 0
Sanding
Assembly Paint
Router
Rough Plane Drilling
Distance
Sand Sand Turn Asm Pnt Rip Rout RfP Drl Turn 1 Asm 1 2 Pnt 2 3 1 Rip 2 1 3 4 Rout 1 2 2 3 1 RfP 2 3 1 2 2 1 Drl 3 4 2 1 3 2 1
Volume*Distance
Sand Sand Turn Asm Pnt Rip Rout RfP Drl Turn 100 Asm 325 20 Pnt 500 45 275 Rip 4 0 75 600 Rout 300 0 200 300 200 RfP 400 0 0 0 700 100 Drl 225 20 350 100 300 0 0
Total
5139
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 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 of Systematic Layout Planning: Importance of Closeness
Value
Closeness
Line code
Numerical weights
A
E I O U X
Absolutely necessary
Especially important Important Ordinary closeness OK Unimportant Undesirable
16
8 4 2 0 80
EXAMPLE : SSLP METHOD
Restrooms Office Restrooms Office Exam rooms Break rooms Waiting rooms Storage
Storage Room Office Restrooms
Exam rooms I A
Break rooms U E U
Waiting rooms A E A U
Storage U I I U
E
X
A E I X
Break Room
Exam Rooms
Waiting Room
Product (Assembly Line) Layouts
• Operations are arranged in the sequence required to make the product • Used when the operations system must handle a narrow variety of products in relatively high volumes • Operations and personnel are dedicated to producing one or a small number of products
Characteristics of Product Layouts
• • • • • • • • • Special-purpose equipment are used Changeover is expensive and lengthy Material flow approaches continuous Material handling equipment is fixed Operators need not be as skilled Little direct supervision is required Planning, scheduling and controlling functions are relatively straight-forward Production time for a unit is relatively short In-process inventory is relatively low
Cellular Manufacturing Layouts
• Operations required to produce a particular family (group) of parts are arranged in the sequence required to make that family • Used when the operations system must handle a moderate variety of products in moderate volumes
Characteristics of Cellular Manufacturing
• • • • •
Equipment can be less general-purpose Material handling costs are reduced Training periods for operators are shortened In-process inventory is lower Parts can be made faster and shipped more quickly • Equipment can be less special-purpose • Changeovers are simplified • Production is easier to automate
Two Part Families
Process Layout Without Part Families
Group Layout Based on Part Families
Comparison of Basic Layout Patterns
Chapter 8 Assembly Line Balancing
Assembly-Line Balancing • An assembly line is a product layout dedicated to combine the components of a good or service that has been created previously. • Assembly line balancing is a technique to group tasks among workstations so that each workstation has – in the ideal case – the same amount of work. • Examples: winemaking industry, credit card processing, Subway sandwich shops, paper manufacturers, insurance policy processing, and automobile assembly lines.
Assembly Line Balancing
• • • • Work station cycle time Task time Precedence relationships Assembly line balancing problem is one of assigning all tasks to a series of workstations such that the total work content at each work station is not more than the cycle time and that the unassigned time across all workstations is minimum.
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?
Station 1
Station 2
Station 3
Minutes 6 7 3 per Unit 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.
Example of Line Balancing
• You’ve just been assigned the job of setting up an electric fan assembly line with the following tasks:
Task A B C D E F G H Time (Mins) 2 1 3.25 1.2 0.5 1 1 1.4 Description Assemble frame Mount switch Assemble motor housing Mount motor housing in frame Attach blade Assemble and attach safety grill Attach cord Test Predecessors None A None A, C D E B F, G
Precedence Diagram
Task Predecessors A None B A C None
Task Predecessors E D F E G B
D
A, C
A B G
H
F, G
H C D E
F
Example of Line Balancing: Precedence Diagram Question: Which process step defines the maximum rate of production?
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
Answer: Task C is the cycle time of the line and therefore, the maximum rate of production.
Example of Line Balancing: Determine
Cycle Time
Question: Suppose we want to assemble 100 fans per day. What would our cycle time have to be?
Answer:
Required Cycle Time, C = Production time per period Required output per period
420 mins / day C= = 4.2 mins / unit 100 units / day
Example of Line Balancing: 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) Nt = Cycle time (C)
11.35 mins / unit Nt = = 2.702, or 3 4.2 mins / unit
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
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2)
Station 2
Station 3
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2)
Station 2
Station 3
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
Station 2
Station 3
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
Station 2 C (4.2-3.25)=.95
Station 3
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
Station 2 C (4.2-3.25)=.95
Station 3
Idle = .95
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
Station 2 C (4.2-3.25)=.95
Station 3 D (4.2-1.2)=3
Idle = .95
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
Station 2 C (4.2-3.25)=.95
Station 3 D (4.2-1.2)=3 E (3-.5)=2.5
Idle = .95
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
Station 2 C (4.2-3.25)=.95
Station 3 D (4.2-1.2)=3 E (3-.5)=2.5 F (2.5-1)=1.5
Idle = .95
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
Station 2 C (4.2-3.25)=.95
Station 3 D (4.2-1.2)=3 E (3-.5)=2.5 F (2.5-1)=1.5 H (1.5-1.4)=.1 Idle = .1
Idle = .95
Which station is the bottleneck? What is the effective cycle time?
Example of Line Balancing: Determine the Efficiency of the Assembly Line
Sum of task times (T) Efficiency = Actual number of workstations (Na) x Cycle time (C)
11.35 mins / unit Efficiency = =.901 (3)(4.2mins / unit)
Some Heuristic Algorithms for Assembly Line Balancing
• COMSOAL ( Computerized Method for Sequencing Operations of Assembly Line) • Helgeson-Bernie Rank Positional Weight (RPW) Technique • Moody and Young’s Method
doc_978430609.pptx
Where the production facilities should be located? What the layout and characteristics of the facilities should be?
Facilities Planning
• How much long range capacity is needed? • When additional capacity is needed? • Where the production facilities should be located? • What the layout and characteristics of the facilities should be?
FACILITY LOCATION
• Once a firm has decided to open a new facility or relocate an existing facility, it must decide where that facility should be located • Facility location problem involves the evaluation of various sites for a new facility. • There are several factors that influence the Facility Location Decision:
Factors Related to Resources
• • • • • • Labour availability, Labour cost, Labour Skills; Materials Availability, Material cost, material quality; Equipment availability, Equipment Cost; Land availability, Land suitability, Land cost; Energy availability, energy cost; Water availability, water quality, water cost.
Factors Related to the Infrastructure &Market
• Availability of Financial Institutions, Strength of Financial Institutions • Government Stability, Government taxes, Import and Export restrictions. • Quality of life, Cultural issues, • Environmental regulations, Transportation availability, Transportation cost, Power • Closeness to the market • Competitors’ size, strength and attitude in that region.
Analytical techniques
• There are many analytical techniques that can be used in facility location decision. • Some of these are: 1) Factor Rating 2) Cost-Profit-Volume analysis 3) Center of Gravity Method, and 4) Transportation and Simulation Models.
Major considerations in Layout Decisions
• Reduce unnecessary or non-value adding activities such as material handling • Reduce inventory and rework • Communication • Safety and security of employees customers and resources • Availability and utilization of space
LAYOUT TYPES
• Different layouts present different managerial challenges • Different layouts present different opportunities to satisfy customers’ needs • A strategic perspective is required to make the right layout choices
– – – – – Fixed-position Product Process Cellular Hybrid (some combination of others)
7
Basic Production Layout Formats
• Fixed-Position Layout – the product remains at one location and equipments are moved to the product • Process Layout (also called job-shop or functional layout) Similar equipments are grouped together • Product Layout (also called line layout)- Equipments are arranged as per the sequence of operations by which the product is made. • Group Technology (Cellular) Layout- Groups dissimilar machines into work centers to work on products that have similar shapes and processing requirements
Fixed-Position Layouts
• Product remains in a fixed position, and the personnel, material and equipment come to it • Used when the product is very bulky, large, heavy or fragile
Fixed product layout
Process (Job Shop) Layouts
• Equipment that perform similar processes are grouped together • Used when the operations system must handle a wide variety of products in relatively small volumes (i.e., flexibility is necessary)
Characteristics of Process Layouts
• • • • • • General-purpose equipments are used Frequent changeovers Material flow is intermittent Operators are highly skilled Technical supervision is required Planning, scheduling and controlling functions are challenging • Production time is relatively long • In-process inventory is relatively high
Materials Handling
• The central focus of most manufacturing layouts is to minimize the cost of processing, transporting, and storing materials throughout the production system. • Materials used in manufacturing include:
– – – – – – Raw material Purchased components Work-in-progress Finished goods Packaging material Maintenance, repair, and operating supplies
Computerized Techniques for Layout Planning Heuristics
• CRAFT ( Computerized Relative Allocation of Facilities Technique) • CORELAP ( Computerized Relationship Layout Planning) • ALDEP ( Automated Layout Design Program)
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 The “best” locations for each department, where best means maximizing flow, which minimizing costs
• Determine
–
Process 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
EXAMPLE : INITIAL LAYOUT
Volume
Sand Sand Turn Turn 100 Asm 325 10 Pnt 250 15 Rip 2 0 Rout 300 0 RfP 200 0 Drl 75 5
Current Layout
Sanding Ripsaw
Asm
Pnt Rip Rout RfP Drl
275
25
150
100
100 200
0
0 350 100
175
100 100 0 0
Turning
Assembly Paint
Router
Rough Plane Drilling
Distance
Sand Sand Turn Asm Pnt Rip Rout RfP Drl Turn 1 Asm 2 1 Pnt 3 2 1 Rip 1 2 3 4 Rout 2 1 2 3 1 RfP 3 2 1 2 2 1 Drl 4 3 2 1 3 2 1
Volume*Distance
Sand Sand Turn Asm Pnt Rip Rout RfP Drl Turn 100 Asm 650 10 Pnt 750 30 275 Rip 2 0 75 600 Rout 600 0 200 300 200 RfP 600 0 0 0 700 100 Drl 300 15 350 100 300 0 0
Total
6257
EXAMPLE : REVISED LAYOUT
Volume
Sand Sand Turn Turn 100 Asm 325 10 Pnt 250 15 Rip 2 0 Rout 300 0 RfP 200 0 Drl 75 5
Revised Layout
Turning Ripsaw
Asm
Pnt Rip Rout RfP Drl
275
25
150
100
100 200
0
0 350 100
175
100 100 0 0
Sanding
Assembly Paint
Router
Rough Plane Drilling
Distance
Sand Sand Turn Asm Pnt Rip Rout RfP Drl Turn 1 Asm 1 2 Pnt 2 3 1 Rip 2 1 3 4 Rout 1 2 2 3 1 RfP 2 3 1 2 2 1 Drl 3 4 2 1 3 2 1
Volume*Distance
Sand Sand Turn Asm Pnt Rip Rout RfP Drl Turn 100 Asm 325 20 Pnt 500 45 275 Rip 4 0 75 600 Rout 300 0 200 300 200 RfP 400 0 0 0 700 100 Drl 225 20 350 100 300 0 0
Total
5139
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 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 of Systematic Layout Planning: Importance of Closeness
Value
Closeness
Line code
Numerical weights
A
E I O U X
Absolutely necessary
Especially important Important Ordinary closeness OK Unimportant Undesirable
16
8 4 2 0 80
EXAMPLE : SSLP METHOD
Restrooms Office Restrooms Office Exam rooms Break rooms Waiting rooms Storage
Storage Room Office Restrooms
Exam rooms I A
Break rooms U E U
Waiting rooms A E A U
Storage U I I U
E
X
A E I X
Break Room
Exam Rooms
Waiting Room
Product (Assembly Line) Layouts
• Operations are arranged in the sequence required to make the product • Used when the operations system must handle a narrow variety of products in relatively high volumes • Operations and personnel are dedicated to producing one or a small number of products
Characteristics of Product Layouts
• • • • • • • • • Special-purpose equipment are used Changeover is expensive and lengthy Material flow approaches continuous Material handling equipment is fixed Operators need not be as skilled Little direct supervision is required Planning, scheduling and controlling functions are relatively straight-forward Production time for a unit is relatively short In-process inventory is relatively low
Cellular Manufacturing Layouts
• Operations required to produce a particular family (group) of parts are arranged in the sequence required to make that family • Used when the operations system must handle a moderate variety of products in moderate volumes
Characteristics of Cellular Manufacturing
• • • • •
Equipment can be less general-purpose Material handling costs are reduced Training periods for operators are shortened In-process inventory is lower Parts can be made faster and shipped more quickly • Equipment can be less special-purpose • Changeovers are simplified • Production is easier to automate
Two Part Families
Process Layout Without Part Families
Group Layout Based on Part Families
Comparison of Basic Layout Patterns
Chapter 8 Assembly Line Balancing
Assembly-Line Balancing • An assembly line is a product layout dedicated to combine the components of a good or service that has been created previously. • Assembly line balancing is a technique to group tasks among workstations so that each workstation has – in the ideal case – the same amount of work. • Examples: winemaking industry, credit card processing, Subway sandwich shops, paper manufacturers, insurance policy processing, and automobile assembly lines.
Assembly Line Balancing
• • • • Work station cycle time Task time Precedence relationships Assembly line balancing problem is one of assigning all tasks to a series of workstations such that the total work content at each work station is not more than the cycle time and that the unassigned time across all workstations is minimum.
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?
Station 1
Station 2
Station 3
Minutes 6 7 3 per Unit 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.
Example of Line Balancing
• You’ve just been assigned the job of setting up an electric fan assembly line with the following tasks:
Task A B C D E F G H Time (Mins) 2 1 3.25 1.2 0.5 1 1 1.4 Description Assemble frame Mount switch Assemble motor housing Mount motor housing in frame Attach blade Assemble and attach safety grill Attach cord Test Predecessors None A None A, C D E B F, G
Precedence Diagram
Task Predecessors A None B A C None
Task Predecessors E D F E G B
D
A, C
A B G
H
F, G
H C D E
F
Example of Line Balancing: Precedence Diagram Question: Which process step defines the maximum rate of production?
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
Answer: Task C is the cycle time of the line and therefore, the maximum rate of production.
Example of Line Balancing: Determine
Cycle Time
Question: Suppose we want to assemble 100 fans per day. What would our cycle time have to be?
Answer:
Required Cycle Time, C = Production time per period Required output per period
420 mins / day C= = 4.2 mins / unit 100 units / day
Example of Line Balancing: 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) Nt = Cycle time (C)
11.35 mins / unit Nt = = 2.702, or 3 4.2 mins / unit
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
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2)
Station 2
Station 3
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2)
Station 2
Station 3
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
Station 2
Station 3
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
Station 2 C (4.2-3.25)=.95
Station 3
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
Station 2 C (4.2-3.25)=.95
Station 3
Idle = .95
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
Station 2 C (4.2-3.25)=.95
Station 3 D (4.2-1.2)=3
Idle = .95
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
Station 2 C (4.2-3.25)=.95
Station 3 D (4.2-1.2)=3 E (3-.5)=2.5
Idle = .95
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
Station 2 C (4.2-3.25)=.95
Station 3 D (4.2-1.2)=3 E (3-.5)=2.5 F (2.5-1)=1.5
Idle = .95
2 A
1 B
1 G
1.4 H F 1
C 3.25
D 1.2
E .5
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 A (4.2-2=2.2) B (2.2-1=1.2) G (1.2-1= .2) Idle= .2
Station 2 C (4.2-3.25)=.95
Station 3 D (4.2-1.2)=3 E (3-.5)=2.5 F (2.5-1)=1.5 H (1.5-1.4)=.1 Idle = .1
Idle = .95
Which station is the bottleneck? What is the effective cycle time?
Example of Line Balancing: Determine the Efficiency of the Assembly Line
Sum of task times (T) Efficiency = Actual number of workstations (Na) x Cycle time (C)
11.35 mins / unit Efficiency = =.901 (3)(4.2mins / unit)
Some Heuristic Algorithms for Assembly Line Balancing
• COMSOAL ( Computerized Method for Sequencing Operations of Assembly Line) • Helgeson-Bernie Rank Positional Weight (RPW) Technique • Moody and Young’s Method
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