process selection and facility layout. learning objectives explain the strategic importance of...
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Process Selection and
Facility Layout
Learning ObjectivesLearning Objectives
Explain the strategic importance of process selection.
Explain the influence that process selection has on an organization.
Describe the basic processing types. Discuss automated approaches to
processing.
Learning ObjectivesLearning Objectives
List some reasons for redesign of layouts. Describe the basic layout types. List the main advantages and
disadvantages of product layouts and process layouts.
Solve simple line-balancing problems.
Process selection Deciding on the way production of
goods or services will be organized Major implications
Capacity planning Layout of facilities Equipment Design of work systems
IntroductionIntroduction
Forecasting
Product andService Design
TechnologicalChange
CapacityPlanning
ProcessSelection
Facilities andEquipment
Layout
WorkDesign
Process Selection and Process Selection and System DesignSystem Design
• Key aspects of process strategy– Capital intensive (mix of equipment/labor)
– Process flexibility
– Design
– Volume
– Technology
Process StrategyProcess Strategy
Kinds of TechnologyKinds of Technology
Operations management is primarily concerned with three kinds of technology: Product and service technology Process technology Information technology
All three have a major impact on: Costs Productivity Competitiveness
Technology Competitive Technology Competitive AdvantageAdvantage
Innovations in Products and services
Cell phonesPDAsWireless computing
Processing technology Increasing productivity Increasing qualityLowering costs
Variety How much
Flexibility What degree
Volume Expected output
Job Shop
Batch
Repetitive
Continuous
Process SelectionProcess Selection
Job shop Small scale
Batch Moderate volume
Repetitive/assembly line High volumes of standardized goods or
services
Continuous Very high volumes of non-discrete goods
Process TypesProcess Types
Process Type
Job Shop Appliance repairEmergency
room
Ineffective
Batch Commercialbaking
ClassroomLecture
Repetitive Automotiveassembly
Automaticcarwash
Continuous(flow)
Ineffective Steel ProductionWater purification
Product and Service Product and Service ProcessesProcesses
Low Volume High Volume
Dimension Job shop Batch Repetitive Continuous
Job variety Very High Moderate Low Very low
Process flexibility
Very High Moderate Low Very low
Unit cost Very High Moderate Low Very low
Volume of output
Very low Low High Very High
Product – Process MatrixProduct – Process Matrix
Other issues; schedulingwork-in-process inventorylabor skill
Process and Product ProfilingProcess and Product Profiling Process selection can involve substantial
investment in Equipment Layout of facilities
Product profiling: Linking key product or service requirements to process capabilities
Key dimensions Range of products or services Expected order sizes Pricing strategies Expected schedule changes Order winning requirements
Automation: Machinery that has sensing and control devices that enables it to operate Fixed automation Programmable automation
AutomationAutomation
• Computer-aided design and manufacturing systems (CAD/CAM)
• Numerically controlled (NC) machines
• Robot
• Manufacturing cell
• Flexible manufacturing systems(FMS)
• Computer-integrated manufacturing (CIM)
AutomationAutomation
Layout: the configuration of departments, work centers, and equipment, with particular emphasis on movement of work (customers
or materials) through the system
Product layouts
Process layouts
Fixed-Position layout
Combination layouts
Facilities LayoutFacilities Layout
Objective of Layout DesignObjective of Layout Design
1. Facilitate attainment of product quality2. Use workers and space efficiently3. Avoid bottlenecks4. Minimize unnecessary material handling
costs5. Eliminate unnecessary movement of
workers or materials6. Minimize production time or customer
service time7. Design for safety
Requires substantial investments of money and effort
Involves long-term commitments Has significant impact on cost and
efficiency of short-term operations
Importance of Layout Importance of Layout DecisionsDecisions
Inefficient operations
For Example:
High CostBottlenecks
Changes in the designof products or services
The introduction of newproducts or services
Accidents
Safety hazards
The Need for Layout DesignThe Need for Layout Design
Changes inenvironmentalor other legalrequirements
Changes in volume ofoutput or mix of
products
Changes in methodsand equipment
Morale problems
The Need for Layout Design The Need for Layout Design (Cont’d)(Cont’d)
Product layouts
Process layouts
Fixed-Position layout
Combination layouts
Basic Layout TypesBasic Layout Types
Product layout Layout that uses standardized processing
operations to achieve smooth, rapid, high-volume flow
Process layout Layout that can handle varied processing
requirements Fixed Position layout
Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed
Basic Layout TypesBasic Layout Types
Raw materialsor customer
Finished item
Station 2
Station 2
Station 3
Station 3
Station 4
Station 4
Material and/or labor
Station 1
Material and/or labor
Material and/or labor
Material and/or labor
Used for Repetitive or Continuous Processing
Product LayoutProduct Layout
High rate of output Low unit cost Labor specialization Low material handling cost High utilization of labor and equipment Established routing and scheduling Routine accounting, purchasing and
inventory control
Advantages of Product LayoutAdvantages of Product Layout
Creates dull, repetitive jobs Poorly skilled workers may not maintain
equipment or quality of output Fairly inflexible to changes in volume Highly susceptible to shutdowns Needs preventive maintenance Individual incentive plans are
impractical
Disadvantages of Product LayoutDisadvantages of Product Layout
1 2 3 4
5
6
78910
In
Out
Workers
A U-Shaped Production LineA U-Shaped Production Line
Ease to cross-travel of workers and vehicles More compact More communication between workers
Work Station 1
Work Station 2
Work Station 3
Product Layout(sequential)
Used for Repetitive Processingor Continuous Processes
Product LayoutProduct Layout
Dept. A
Dept. B Dept. D
Dept. C
Dept. F
Dept. E
Used for Intermittent processingJob Shop or Batch Processes
Process Layout(functional)
Process LayoutProcess Layout
Can handle a variety of processing requirements
Not particularly vulnerable to equipment failures
Equipment used is less costly Possible to use individual incentive
plans
Advantages of Process LayoutsAdvantages of Process Layouts
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
Disadvantages of Process Disadvantages of Process LayoutsLayouts
Fixed Position LayoutsFixed Position Layouts
Fixed Position Layout: Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed.
Nature of the product dictates this type of layout Weight Size Bulk
Large construction projects
Cellular Production Layout in which machines are grouped into
a cell that can process items that have similar processing requirements
Group Technology The grouping into part families of items with
similar design or manufacturing characteristics
Cellular LayoutsCellular Layouts
Dimension Functional CellularNumber of moves between departments
many few
Travel distances longer shorter
Travel paths variable fixed
Job waiting times greater shorter
Throughput time higher lower
Amount of work in process
higher lower
Supervision difficulty higher lower
Scheduling complexity higher lower
Equipment utilization lower higher
Functional vs. Cellular LayoutsFunctional vs. Cellular Layouts
Warehouse and storage layouts Retail layouts Office layouts
Service LayoutsService Layouts
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 Design Product Layouts: Line BalancingBalancing
Cycle time is the maximum time allowed at each workstation tocomplete its set of tasks on a unit.
Cycle TimeCycle 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 OutputDetermine Maximum Output
task timeof sum = t
CT
t)( =N
Determine the Minimum Number Determine the Minimum Number
of Workstations Requiredof 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 DiagramPrecedence Diagram
Arrange tasks shown in Figure 6.10 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 Example 1: Assembly Line BalancingBalancing
Workstation
TimeRemaining 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 SolutionExample 1 Solution
Percent idle time = Idle time per cycle
(N)(CT)
Efficiency = 100 – Percent idle time
Calculate Percent Idle TimeCalculate 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 RulesLine Balancing Rules
Example 2Example 2Plan to produce 400 units in 1 day (8 hours)
Immediate Task time Task follower (min)a b 0.2b e 0.2c d 0.8d f 0.6e f 0.3f g 1.0g h 0.4h end 0.3
c d
a b e
f g h
0.2 0.2 0.3
0.8 0.6
1.0 0.4 0.3
Station 1 Station 2 Station 3 Station 4
a b ef
d
g h
c
Solution to Example 2Solution to Example 2
1 min.2 min.1 min.1 min. 30/hr. 30/hr. 30/hr. 30/hr.
Bottleneck
Bottleneck WorkstationBottleneck Workstation
Parallel WorkstationsParallel Workstations
1 min.
2 min.
1 min.1 min. 60/hr.
30/hr. 30/hr.
60/hr.
2 min.
30/hr.30/hr.
Parallel Workstations
Copier ExampleCopier Example
This means that This means that tasks B and E tasks B and E cannot be done cannot be done until task A has until task A has been completedbeen completed
PerformancePerformance Task Must FollowTask Must FollowTimeTime Task ListedTask Listed
TaskTask (minutes)(minutes) BelowBelow
AA 1010 ——BB 1111 AACC 55 BBDD 44 BBEE 1212 AAFF 33 C, DC, DGG 77 FFHH 1111 EEII 33 G, HG, H
Total time Total time 6666
Copier ExampleCopier Example
PerformancePerformance Task Must FollowTask Must FollowTimeTime Task ListedTask Listed
TaskTask (minutes)(minutes) BelowBelow
AA 1010 ——BB 1111 AACC 55 BBDD 44 BBEE 1212 AAFF 33 C, DC, DGG 77 FFHH 1111 EEII 33 G, HG, H
Total time Total time 6666 I
GF
C
D
H
B
E
A
10
1112
5
4 3
711 3
Figure 9.13
I
GF
C
D
H
B
E
A
10
1112
5
4 3
711 3
Figure 9.13
PerformancePerformance Task Must FollowTask Must FollowTimeTime Task ListedTask Listed
TaskTask (minutes)(minutes) BelowBelow
AA 1010 ——BB 1111 AACC 55 BBDD 44 BBEE 1212 AAFF 33 C, DC, DGG 77 FFHH 1111 EEII 33 G, HG, H
Total time Total time 6666
Copier ExampleCopier Example480 available
mins per day40 units required
Cycle time =
Production time available per day
Units required per day
= 480 / 40= 12 minutes per unit
Minimum number of
workstations=
∑ Time for task i
Cycle time
n
i = 1
= 66 / 12= 5.5 or 6 stations
I
GF
C
D
H
B
E
A
10
1112
5
4 3
711 3
Figure 9.13
PerformancePerformance Task Must FollowTask Must FollowTimeTime Task ListedTask Listed
TaskTask (minutes)(minutes) BelowBelow
AA 1010 ——BB 1111 AACC 55 BBDD 44 BBEE 1212 AAFF 33 C, DC, DGG 77 FFHH 1111 EEII 33 G, HG, H
Total time Total time 6666
Copier ExampleCopier Example480 available
mins per day40 units required
Cycle time = 12 mins
Minimum workstations = 5.5 or 6
Line-Balancing Heuristics
1. Longest task time Choose the available task with the longest task time
2. Most following tasks Choose the available task with the largest number of following tasks
3. Ranked positional weight
Choose the available task for which the sum of following task times is the longest
4. Shortest task time Choose the available task with the shortest task time
5. Least number of following tasks
Choose the available task with the least number of following tasks
Table 9.4
480 available mins per day
40 units required
Cycle time = 12 mins
Minimum workstations = 5.5 or 6
PerformancePerformance Task Must FollowTask Must FollowTimeTime Task ListedTask Listed
TaskTask (minutes)(minutes) BelowBelow
AA 1010 ——BB 1111 AACC 55 BBDD 44 BBEE 1212 AAFF 33 C, DC, DGG 77 FFHH 1111 EEII 33 G, HG, H
Total time Total time 6666
Copier ExampleCopier Example
I
GF
H
C
D
10 11
12
5
4
3 7
11
3B
E
A
Station 1
Station 2
Station 3
Station 5
Station 4
Station 6
Figure 9.14
PerformancePerformance Task Must FollowTask Must FollowTimeTime Task ListedTask Listed
TaskTask (minutes)(minutes) BelowBelow
AA 1010 ——BB 1111 AACC 55 BBDD 44 BBEE 1212 AAFF 33 C, DC, DGG 77 FFHH 1111 EEII 33 G, HG, H
Total time Total time 6666
Copier ExampleCopier Example480 available
mins per day40 units required
Cycle time = 12 mins
Minimum workstations = 5.5 or 6
Efficiency =∑ Task times
(actual number of workstations) x (largest cycle time)
= 66 minutes / (6 stations) x (12 minutes)
= 91.7%
Example 1Example 1PerformancePerformance Task Must FollowTask Must Follow
TimeTime Task ListedTask ListedTaskTask (minutes)(minutes) BelowBelow
11 0.200.20 --22 0.400.40 --33 0.700.70 1144 0.100.10 1,21,255 0.300.30 2266 0.110.11 3377 0.320.32 3388 0.600.60 3,43,499 0.270.27 6,7,86,7,8
1010 0.380.38 5,85,8
1111 0.500.50 9,109,10
1212 0.120.12 1111
Total time 4 min.Total time 4 min.
Balance by Balance by
1 Longest task time 1 Longest task time methodmethod
2 RPW method2 RPW method
Example 2Example 2PerformancePerformance Task Must FollowTask Must Follow
TimeTime Task ListedTask ListedTaskTask (minutes)(minutes) BelowBelow
11 0.50.5 --22 0.30.3 1133 0.80.8 1144 0.20.2 2255 0.10.1 2266 0.60.6 3377 0.40.4 4,54,588 0.50.5 3,53,599 0.30.3 7,87,8
1010 0.60.6 6,96,9
Total time 4.3 min.Total time 4.3 min.
Balance by Balance by
1 Longest task time 1 Longest task time methodmethod
2 RPW method2 RPW method
Information Requirements:
1. List of departments
2. Projection of work flows
3. Distance between locations
4. Amount of money to be invested
5. List of special considerations
6. Location of key utilities
Designing Process LayoutsDesigning Process Layouts
1 3 2
30
170 100
A B C
Example 3: Interdepartmental Work Example 3: Interdepartmental Work FlowsFlows
for Assigned Departmentsfor Assigned Departments
Gearcutting
Mill Drill
Lathes
Grind
Heattreat
Assembly
111
333
222
444
222111444
111 3331111 2222
222
3333
111
444111
333333333
44444
3333
3322
222
Functional LayoutFunctional Layout
1111 -1111
2222 - 2222
Ass
emb
ly
3333 - 3333
4444 - 4444
Lathe
Lathe
Mill
Mill
Mill
Mill
Drill
Drill
Drill
Heat treat
Heat treat
Heat treat
Gear cut
Gear cut
Grind
Grind
Cellular Manufacturing LayoutCellular Manufacturing Layout
Used to obtain optimal solutions to problems that involve restrictions or limitations, such as: Materials Budgets Labor Machine time
Linear ProgrammingLinear Programming
Objective Function: mathematical statement of profit or cost for a given solution
Decision variables: amounts of either inputs or outputs
Feasible solution space: the set of all feasible combinations of decision variables as defined by the constraints
Constraints: limitations that restrict the available alternatives
Parameters: numerical values
Linear Programming ModelLinear Programming Model
1.Set up objective function and constraints in mathematical format
2.Plot the constraints
3.Identify the feasible solution space
4.Plot the objective function
5.Determine the optimum solution
Graphical Linear ProgrammingGraphical Linear Programming
Graphical method for finding optimal solutions to two-variable problems
Objective - profitMaximize Z=60X1 + 50X2
Subject toAssembly 4X1 + 10X2 <= 100 hours
Inspection 2X1 + 1X2 <= 22 hours
Storage 3X1 + 3X2 <= 39 cubic feet
X1, X2 >= 0
Linear Programming ExampleLinear Programming Example
Assembly Constraint4X1 +10X2 = 100
0
2
4
6
8
10
12
0 2 4 6 8 10 12 14 16 18 20 22 24
Product X1
Pro
du
ct X
2
Linear Programming ExampleLinear Programming Example
Linear Programming ExampleLinear Programming Example
Add Inspection Constraint2X1 + 1X2 = 22
0
5
10
15
20
25
0 2 4 6 8 10 12 14 16 18 20 22 24
Product X1
Pro
du
ct X
2
Add Storage Constraint3X1 + 3X2 = 39
0
5
10
15
20
25
0 2 4 6 8 10 12 14 16 18 20 22 24
Product X1
Pro
du
ct X
2
AssemblyStorage
Inspection
Feasible solution space
Linear Programming ExampleLinear Programming Example
Add Profit Lines
0
5
10
15
20
25
0 2 4 6 8 10 12 14 16 18 20 22 24
Product X1
Pro
du
ct X
2
Z=300
Z=900
Z=600
Linear Programming ExampleLinear Programming Example
The intersection of inspection and storage Solve two equations in two unknowns
2X1 + 1X2 = 223X1 + 3X2 = 39
X1 = 9X2 = 4Z = $740
SolutionSolution
Solutions and Corner PointsSolutions and Corner Points
Feasible solution space is usually a polygon Solution will be at one of the corner points
Enumeration approach: Substituting the coordinates of each corner point into the objective function to determine which corner point is optimal.
Simplex: a linear-programming algorithm that can solve problems having more than two decision variables
Simplex MethodSimplex Method
MS Excel Worksheet for MS Excel Worksheet for Microcomputer ProblemMicrocomputer Problem
MS Excel Worksheet SolutionMS Excel Worksheet Solution