Description
product process matrix, scheduling. It explains short term scheduling with examples, Strategic Implications of Short-Term Scheduling. It covers priority rules for dispatching jobs, johnson rule of sequencing.
Scheduling
Learnings for Production Planning game
• Planning for uncertainty and complex nature of planning process – iterative (with self correction) process of matching capacity with demand • Variation/ tradeoffs of three inventory related costs-holding, stockout, overtime • Plan based on logic and do not waiver if you get hit sometimes • You have to live with your mistakes • Planning – use of time buckets - plan for a period at a time- you do not need to plan for longer period as more information
The Production Planning Process
Top Management Planning
Business Planning Sales Planning Production Planning
Objectives Demands Resources no FEEDBACK Products Materials Capacity
Operations management Planning
Resource OK? yes
Bill of Materials Inventory status Routings
Master Scheduling Materials Planning Capacity Planning
Planning OK? yes no
Operations Management Execution
Purchasing Shop Floor control Performance Measurement
Parts Hours Accountability
PRODUCT-PROCESS MATRIX
PRODUCT MIX One off Low Vol High Vol Mass PROCE PATTERN ESS Jumbled Jumbled But Dominant Line Flow Li Fl Cont Flow
Bidding, Design, Del. Quality Volumes
PROJECT JOB SHOP BATCH LINE CONT
Price Forecast
Scheduling Matl Hand Shifting B’Neck Worker Motivation Capital Budget Tech. Mgt Vert Integration
PRODUCT-PROCESS MATRIX
One off Jumbled Aerospace Printing Industrial Machinery Machine tools Apparel Drugs, Electronics Auto A t Rubber & Tyres Cont Flow Paper Oil, Steel, Brewery Low Vol High Vol Mass
Batch, jumbled flow Line Flow
PRODUCT-PROCESS MATRIX Product Low Vol High Vol Mass mix One off
Process pattern Jumbled Batch, jumbled flow Line Flow Custom many product some product Commodity Sequencing rules OPT
MRP & JIT J JIT Periodic review / cyclic scheduling
Cont Flow
PRODUCT-PROCESS MATRIX
Nature of relevant industries Low volume fabrication f b i ti Batch, low volume assembly Medium volume assembly High volume repetitive assembly Continuous process System Sequencing rules Factory physics Optimized production Technology MRP &JIT Primary focus of system Flexibility to cope with many diff ith different t orders Bottleneck management, Effective coordination of material & labor Min set up times & inventories High capacity utilization
JIT Periodic review/ cyclic schedule
Short-Term Scheduling Examples
• Hospital – Outpatient treatments –O Operating rooms ti • University – Instructors – Classrooms • Factor Factory – Production – Purchases
© 1984-1994 T/Maker Co.
Strategic Implications of Short-Term Scheduling
• By scheduling effectively, companies use assets more effectively and create greater capacity per dollar invested, which, in turn, lowers cost • This added capacity and related flexibility provides faster delivery and therefore better customer service • Good scheduling is a competitive advantage which contributes to dependable delivery
Short-Term Scheduling
• Deals with timing of operations • Sh run focus: Hourly, daily, weekly Short f H l d il kl • Types
Forward Scheduling B Today E Due Date Today Backward Scheduling B E Due Date
Manufacturing Process
Legend: Batch of parts Workstation
Sequencing • Specifies order jobs will be worked • Sequencing rules
– First come, first served (FCFS) – Shortest processing time (SPT) – Earliest due date (EDD) – Longest p g processing time ( g (LPT) ) – Critical ratio (CR) – Johnson’s rule
Shipping Department
Raw Materials
Priority Rules for Dispatching Jobs
FCFS EDD SPT LPT CR
First come, first served The first job to arrive at a work center is processed first Earliest due date The job with the earliest due date is processed first Shortest processing time The job with the shortest processing time is processed first Longest processing time The job with the longest processing time is processed first Critical ratio The ratio of time remaining to required work time remaining is calculated, and jobs are scheduled in order of increasing ratio.
First Come, First Served Rule • Process first job to arrive at a work center first • Average performance on most scheduling criteria • Appears ‘fair’ & reasonable to customers
– Important for service organizations
• Example: Restaurants
Shortest Processing Time Rule • Process job with shortest processing time first. • Usually best at minimizing job flow and minimizing the number of jobs in the system • Major disadvantage is that long jobs may be continuously pushed back in the queue.
Longest Processing Time Rule • Process job with longest processing time first. • Usually the least effective method of sequencing.
Earliest Due Date Rule • Process job with earliest due date first • Widely used by many companies
– If due dates important – If MRP used
• Due dates updated by each MRP run
• Performs poorly on many scheduling p y y g criteria
Critical Ratio (CR) ? Ratio of time remaining to work time remaining
CR = Time remaining Work days remaining = Due date - Today' s date Work (lead ) time remaining ( g
• Process job with smallest CR first • Performs well on average lateness
Advantages of the Critical Ratio Scheduling Rule Use of the critical ratio can help to:
–d t determine th status of a specific job i the t t f ifi j b – establish a relative priority among jobs on a common basis – relate both stock and make-to-order jobs on a common basis – adjust priorities and revise schedules automatically for changes in both demand and job progress – dynamically track job progress and location
Sequencing Jobs Through One Process
Some Terms : Flowtime (completion time)
Time for a job to flow through the system
Makespan
Time for a group of jobs to be completed
Tardiness
Difference between a late job’s due date and its completion time
Criteria to Evaluate Priority Rules
Average completion time = ?Flow times #J b Jobs
Utilization =
?Process times ?Flow times
? Flow times ?P Process ti times
? Late times Number of jobs
Average number of jobs in the system =
Average job lateness (tardiness ) =
Simple Sequencing Rules
JOB PROCESSING TIME DUE DATE Evaluation Criteria:
A B C D E
5 10 2 8 6
10 15 5 12 8
1. 1 Average completion time 2. Average Tardiness 3. No. of jobs Tardy 4. Maximum Tardiness
Problem in class: Evaluate the following rules for this problem
Use rules 1. FCFS 2. E D Date 3. Slack 4. Critical Ratio 5. SPT
Simple Sequencing Rules -FCFS
JOB PROCESSING TIME DUE DATE
A B C D E
FCFS SEQUENCE
5 10 2 8 6
START TIME
10 15 5 12 8
FCFS
PROCESSING COMPLETION DUE TIME TIME DATE
TARDINESS
A B C D E
0 5 15 17 25
5 10 2 8 6
5 15 17 25 31
10 15 5 12 8
0 0 12 13 23
Simple Sequencing Rules- ED Date
JOB PROCESSING TIME DUE DATE
A B C D E
DDATE SEQUENCE
5 10 2 8 6
START TIME
10 15 5 12 8
EDDATE
PROCESSING COMPLETION DUE TIME TIME DATE
TARDINESS
C E A D B
0 2 8 13 21
2 6 5 8 10
2 8 13 21 31
5 8 10 12 15
0 0 3 9 16
Simple Sequencing Rules -Slack
JOB PROCESSING TIME DUE DATE
A B C D E
SLACK SEQUENCE
5 10 2 8 6
START TIME
10 15 5 12 8
Job A (10) - 5 B (15) - 10 C (5) - 2 SLACK D (12) - 8 E (8) - 6
= = = = =
5* 5* 3 4 2
PROCESSING COMPLETION DUE TIME TIME DATE
TARDINESS
E C D A B
0 6 8 16 21
6 2 8 5 10
6 8 16 21 31
8 5 12 10 15
0 3 4 11 16
Simple Sequencing Rules: Critical Ratio
JOB PROCESSING TIME DUE DATE
A B C D E
CR SEQUENCE
5 10 2 8 6
START TIME
10 15 5 12 8
Job A (10) / 5 B (15) / 10 CCR / 2 (5) D (12) / 8 E (8) / 6
= = = = =
2.00 1.50 1 50 2.50 1.50 1.33
PROCESSING COMPLETION DUE TIME TIME DATE
TARDINESS
E D B A C
0 6 14 24 29
6 8 10 5 2
6 14 24 29 31
8 12 15 10 5
0 2 9 19 26
Simple Sequencing Rules _ SPT
JOB PROCESSING TIME DUE DATE
A B C D E
SPT SEQUENCE
5 10 2 8 6
START TIME
10 15 5 12 8
SPT
PROCESSING COMPLETION DUE TIME TIME DATE
TARDINESS
C A E D B
0 2 7 13 21
2 5 6 8 10
2 7 13 21 31
5 10 8 12 15
0 0 5 9 16
Simple Sequencing Rules
Summary
RULE AVERAGE COMPLETION TIME AVERAGE TARDINESS NO. OF JOBS TARDY MAXIMUM TARDINESS
FCFS EDDATE SLACK CR SPT
18.60 15.00 16.40 20.80 14.80
9.6 5.6 6.8 11.2 6.0
3 3 4 4 3
23 16 16 26 16
Gantt Load Chart for Week of March 6 • Shows relative workload in facility • Disadvantages
– Does not account for unexpected events – Must be updated regularly
Day
Work Center
Monday Job 349
Tuesday
Wednesday
Thursday Job 350
Friday
Metalworks Mechanical Electronics Painting
Job 349 Job 408 Job 295 Job 408
Job 406 Job 349 Job 349
Processing
Unscheduled
Center not available (for example, maintenance time, repairs, shortages)
Gantt Scheduling Chart
Start of an activity End of an activity Scheduled activity time allowed Actual work progress Nonproduction time
Job Job A Job B Job C
Day S 1
Day 2
Day T 3
Day Day Day W 5 T 4
Day F 6
Day S 7
Maintenance
Now
Point in time when chart is reviewed
Johnson’s Rule
• Used to sequence N jobs through 2 machines i th same order hi in the d
Jobs (N = 3) Saw Drill
Job A Job B Job C
© 1995 Corel Corp. © 1995 Corel Corp.
Sequencing Jobs Through Two Serial Process
1. List time required to process each job at each machine. Set up a one-dimensional matrix to onerepresent desired sequence with # of slots equal to # of jobs jobs. 2. Select smallest processing time at either machine. If that time is on machine 1, put the job as near to beginning of sequence as possible. 3. If smallest time occurs on machine 2, put the job as near to the end of the sequence as possible. 4. Remove job from list. 5. Repeat steps 2-4 until all slots in matrix are filled & 2all jobs are sequenced.
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
C
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
C
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
E
C
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
E
C
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
E
A
B
C
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
E
A
D
B
C
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
E
A
D
B
C
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
E
A
D
B
C
Johnson’s Rule
JOB A B C D E
E 5 A 11
PROCESS 1 6 11 7 9 5
D
PROCESS 2 8 6 3 7 10
B 20 31 Idle time
E
A
D
B
C
C 38
Process 1 (sanding)
E 5 15
A 23
D 30
B 37
C 41
Process 2 (painting) Completion time
Sequencing Jobs Through Many Machines/Processes
Facility i d F ilit is dynamic, new jobs added i j b dd d Develop global sequencing rules
First-inFirst-in-system, first-served (FISFS) firstWork-in-nextWork-in-next-queue (WINQ) Fewest # remaining operations (NOPN) g p ( ) Slack per remaining operation (S/OPN) Remaining work (RWK)
Study system via simulation
Guidelines for Selecting a Sequencing Rule
1. 1 SPT most useful when shop is highly congested t f l h h i hi hl t d 2. Use SLACK or S/OPN for periods of normal activity 3. Use DDATE when only small tardiness values can be tolerated 4. Use LPT if subcontracting is anticipated 5. Use FCFS when operating at low-capacity levels low6. Do not use SPT to sequence jobs that have to be assembled with other jobs at a later date
doc_252522403.pdf
product process matrix, scheduling. It explains short term scheduling with examples, Strategic Implications of Short-Term Scheduling. It covers priority rules for dispatching jobs, johnson rule of sequencing.
Scheduling
Learnings for Production Planning game
• Planning for uncertainty and complex nature of planning process – iterative (with self correction) process of matching capacity with demand • Variation/ tradeoffs of three inventory related costs-holding, stockout, overtime • Plan based on logic and do not waiver if you get hit sometimes • You have to live with your mistakes • Planning – use of time buckets - plan for a period at a time- you do not need to plan for longer period as more information
The Production Planning Process
Top Management Planning
Business Planning Sales Planning Production Planning
Objectives Demands Resources no FEEDBACK Products Materials Capacity
Operations management Planning
Resource OK? yes
Bill of Materials Inventory status Routings
Master Scheduling Materials Planning Capacity Planning
Planning OK? yes no
Operations Management Execution
Purchasing Shop Floor control Performance Measurement
Parts Hours Accountability
PRODUCT-PROCESS MATRIX
PRODUCT MIX One off Low Vol High Vol Mass PROCE PATTERN ESS Jumbled Jumbled But Dominant Line Flow Li Fl Cont Flow
Bidding, Design, Del. Quality Volumes
PROJECT JOB SHOP BATCH LINE CONT
Price Forecast
Scheduling Matl Hand Shifting B’Neck Worker Motivation Capital Budget Tech. Mgt Vert Integration
PRODUCT-PROCESS MATRIX
One off Jumbled Aerospace Printing Industrial Machinery Machine tools Apparel Drugs, Electronics Auto A t Rubber & Tyres Cont Flow Paper Oil, Steel, Brewery Low Vol High Vol Mass
Batch, jumbled flow Line Flow
PRODUCT-PROCESS MATRIX Product Low Vol High Vol Mass mix One off
Process pattern Jumbled Batch, jumbled flow Line Flow Custom many product some product Commodity Sequencing rules OPT
MRP & JIT J JIT Periodic review / cyclic scheduling
Cont Flow
PRODUCT-PROCESS MATRIX
Nature of relevant industries Low volume fabrication f b i ti Batch, low volume assembly Medium volume assembly High volume repetitive assembly Continuous process System Sequencing rules Factory physics Optimized production Technology MRP &JIT Primary focus of system Flexibility to cope with many diff ith different t orders Bottleneck management, Effective coordination of material & labor Min set up times & inventories High capacity utilization
JIT Periodic review/ cyclic schedule
Short-Term Scheduling Examples
• Hospital – Outpatient treatments –O Operating rooms ti • University – Instructors – Classrooms • Factor Factory – Production – Purchases
© 1984-1994 T/Maker Co.
Strategic Implications of Short-Term Scheduling
• By scheduling effectively, companies use assets more effectively and create greater capacity per dollar invested, which, in turn, lowers cost • This added capacity and related flexibility provides faster delivery and therefore better customer service • Good scheduling is a competitive advantage which contributes to dependable delivery
Short-Term Scheduling
• Deals with timing of operations • Sh run focus: Hourly, daily, weekly Short f H l d il kl • Types
Forward Scheduling B Today E Due Date Today Backward Scheduling B E Due Date
Manufacturing Process
Legend: Batch of parts Workstation
Sequencing • Specifies order jobs will be worked • Sequencing rules
– First come, first served (FCFS) – Shortest processing time (SPT) – Earliest due date (EDD) – Longest p g processing time ( g (LPT) ) – Critical ratio (CR) – Johnson’s rule
Shipping Department
Raw Materials
Priority Rules for Dispatching Jobs
FCFS EDD SPT LPT CR
First come, first served The first job to arrive at a work center is processed first Earliest due date The job with the earliest due date is processed first Shortest processing time The job with the shortest processing time is processed first Longest processing time The job with the longest processing time is processed first Critical ratio The ratio of time remaining to required work time remaining is calculated, and jobs are scheduled in order of increasing ratio.
First Come, First Served Rule • Process first job to arrive at a work center first • Average performance on most scheduling criteria • Appears ‘fair’ & reasonable to customers
– Important for service organizations
• Example: Restaurants
Shortest Processing Time Rule • Process job with shortest processing time first. • Usually best at minimizing job flow and minimizing the number of jobs in the system • Major disadvantage is that long jobs may be continuously pushed back in the queue.
Longest Processing Time Rule • Process job with longest processing time first. • Usually the least effective method of sequencing.
Earliest Due Date Rule • Process job with earliest due date first • Widely used by many companies
– If due dates important – If MRP used
• Due dates updated by each MRP run
• Performs poorly on many scheduling p y y g criteria
Critical Ratio (CR) ? Ratio of time remaining to work time remaining
CR = Time remaining Work days remaining = Due date - Today' s date Work (lead ) time remaining ( g
• Process job with smallest CR first • Performs well on average lateness
Advantages of the Critical Ratio Scheduling Rule Use of the critical ratio can help to:
–d t determine th status of a specific job i the t t f ifi j b – establish a relative priority among jobs on a common basis – relate both stock and make-to-order jobs on a common basis – adjust priorities and revise schedules automatically for changes in both demand and job progress – dynamically track job progress and location
Sequencing Jobs Through One Process
Some Terms : Flowtime (completion time)
Time for a job to flow through the system
Makespan
Time for a group of jobs to be completed
Tardiness
Difference between a late job’s due date and its completion time
Criteria to Evaluate Priority Rules
Average completion time = ?Flow times #J b Jobs
Utilization =
?Process times ?Flow times
? Flow times ?P Process ti times
? Late times Number of jobs
Average number of jobs in the system =
Average job lateness (tardiness ) =
Simple Sequencing Rules
JOB PROCESSING TIME DUE DATE Evaluation Criteria:
A B C D E
5 10 2 8 6
10 15 5 12 8
1. 1 Average completion time 2. Average Tardiness 3. No. of jobs Tardy 4. Maximum Tardiness
Problem in class: Evaluate the following rules for this problem
Use rules 1. FCFS 2. E D Date 3. Slack 4. Critical Ratio 5. SPT
Simple Sequencing Rules -FCFS
JOB PROCESSING TIME DUE DATE
A B C D E
FCFS SEQUENCE
5 10 2 8 6
START TIME
10 15 5 12 8
FCFS
PROCESSING COMPLETION DUE TIME TIME DATE
TARDINESS
A B C D E
0 5 15 17 25
5 10 2 8 6
5 15 17 25 31
10 15 5 12 8
0 0 12 13 23
Simple Sequencing Rules- ED Date
JOB PROCESSING TIME DUE DATE
A B C D E
DDATE SEQUENCE
5 10 2 8 6
START TIME
10 15 5 12 8
EDDATE
PROCESSING COMPLETION DUE TIME TIME DATE
TARDINESS
C E A D B
0 2 8 13 21
2 6 5 8 10
2 8 13 21 31
5 8 10 12 15
0 0 3 9 16
Simple Sequencing Rules -Slack
JOB PROCESSING TIME DUE DATE
A B C D E
SLACK SEQUENCE
5 10 2 8 6
START TIME
10 15 5 12 8
Job A (10) - 5 B (15) - 10 C (5) - 2 SLACK D (12) - 8 E (8) - 6
= = = = =
5* 5* 3 4 2
PROCESSING COMPLETION DUE TIME TIME DATE
TARDINESS
E C D A B
0 6 8 16 21
6 2 8 5 10
6 8 16 21 31
8 5 12 10 15
0 3 4 11 16
Simple Sequencing Rules: Critical Ratio
JOB PROCESSING TIME DUE DATE
A B C D E
CR SEQUENCE
5 10 2 8 6
START TIME
10 15 5 12 8
Job A (10) / 5 B (15) / 10 CCR / 2 (5) D (12) / 8 E (8) / 6
= = = = =
2.00 1.50 1 50 2.50 1.50 1.33
PROCESSING COMPLETION DUE TIME TIME DATE
TARDINESS
E D B A C
0 6 14 24 29
6 8 10 5 2
6 14 24 29 31
8 12 15 10 5
0 2 9 19 26
Simple Sequencing Rules _ SPT
JOB PROCESSING TIME DUE DATE
A B C D E
SPT SEQUENCE
5 10 2 8 6
START TIME
10 15 5 12 8
SPT
PROCESSING COMPLETION DUE TIME TIME DATE
TARDINESS
C A E D B
0 2 7 13 21
2 5 6 8 10
2 7 13 21 31
5 10 8 12 15
0 0 5 9 16
Simple Sequencing Rules
Summary
RULE AVERAGE COMPLETION TIME AVERAGE TARDINESS NO. OF JOBS TARDY MAXIMUM TARDINESS
FCFS EDDATE SLACK CR SPT
18.60 15.00 16.40 20.80 14.80
9.6 5.6 6.8 11.2 6.0
3 3 4 4 3
23 16 16 26 16
Gantt Load Chart for Week of March 6 • Shows relative workload in facility • Disadvantages
– Does not account for unexpected events – Must be updated regularly
Day
Work Center
Monday Job 349
Tuesday
Wednesday
Thursday Job 350
Friday
Metalworks Mechanical Electronics Painting
Job 349 Job 408 Job 295 Job 408
Job 406 Job 349 Job 349
Processing
Unscheduled
Center not available (for example, maintenance time, repairs, shortages)
Gantt Scheduling Chart
Start of an activity End of an activity Scheduled activity time allowed Actual work progress Nonproduction time
Job Job A Job B Job C
Day S 1
Day 2
Day T 3
Day Day Day W 5 T 4
Day F 6
Day S 7
Maintenance
Now
Point in time when chart is reviewed
Johnson’s Rule
• Used to sequence N jobs through 2 machines i th same order hi in the d
Jobs (N = 3) Saw Drill
Job A Job B Job C
© 1995 Corel Corp. © 1995 Corel Corp.
Sequencing Jobs Through Two Serial Process
1. List time required to process each job at each machine. Set up a one-dimensional matrix to onerepresent desired sequence with # of slots equal to # of jobs jobs. 2. Select smallest processing time at either machine. If that time is on machine 1, put the job as near to beginning of sequence as possible. 3. If smallest time occurs on machine 2, put the job as near to the end of the sequence as possible. 4. Remove job from list. 5. Repeat steps 2-4 until all slots in matrix are filled & 2all jobs are sequenced.
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
C
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
C
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
E
C
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
E
C
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
E
A
B
C
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
E
A
D
B
C
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
E
A
D
B
C
Johnson’s Rule
JOB A B C D E PROCESS 1 6 11 7 9 5 PROCESS 2 8 6 3 7 10
E
A
D
B
C
Johnson’s Rule
JOB A B C D E
E 5 A 11
PROCESS 1 6 11 7 9 5
D
PROCESS 2 8 6 3 7 10
B 20 31 Idle time
E
A
D
B
C
C 38
Process 1 (sanding)
E 5 15
A 23
D 30
B 37
C 41
Process 2 (painting) Completion time
Sequencing Jobs Through Many Machines/Processes
Facility i d F ilit is dynamic, new jobs added i j b dd d Develop global sequencing rules
First-inFirst-in-system, first-served (FISFS) firstWork-in-nextWork-in-next-queue (WINQ) Fewest # remaining operations (NOPN) g p ( ) Slack per remaining operation (S/OPN) Remaining work (RWK)
Study system via simulation
Guidelines for Selecting a Sequencing Rule
1. 1 SPT most useful when shop is highly congested t f l h h i hi hl t d 2. Use SLACK or S/OPN for periods of normal activity 3. Use DDATE when only small tardiness values can be tolerated 4. Use LPT if subcontracting is anticipated 5. Use FCFS when operating at low-capacity levels low6. Do not use SPT to sequence jobs that have to be assembled with other jobs at a later date
doc_252522403.pdf