SlideShare a Scribd company logo

hr_om11_ch15.ppt

Download as PPT, PDF
R
RajaNorhafizahRajaBe

This document discusses short-term scheduling concepts and techniques. It begins with learning objectives for the chapter on short-term scheduling. It then provides examples of scheduling needs at different companies like Delta Airlines and discusses the importance of effective short-term scheduling. Key concepts covered include forward and backward scheduling, finite and infinite loading, priority sequencing rules, and the assignment method for allocating jobs to resources. Gantt charts are presented as a tool for displaying scheduling information visually.

Education
1 of 74
Download to read offline
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
15 - 1 © 2014 Pearson Education, Inc. Short-Term Scheduling PowerPoint presentation to accompany Heizer and Render Operations Management, Eleventh Edition Principles of Operations Management, Ninth Edition PowerPoint slides by Jeff Heyl 15 © 2014 Pearson Education, Inc.
15 - 2 © 2014 Pearson Education, Inc. Outline ► Global Company Profile: Delta Air Lines ► The Importance of Short-Term Scheduling ► Scheduling Issues ► Scheduling Process-Focused Facilities
15 - 3 © 2014 Pearson Education, Inc. Outline - Continued ► Loading Jobs ► Scheduling Jobs ► Finite Capacity Scheduling (FCS) ► Scheduling Services
15 - 4 © 2014 Pearson Education, Inc. Learning Objectives When you complete this chapter you should be able to: 1. Explain the relationship between short- term scheduling, capacity planning, aggregate planning, and a master schedule 2. Draw Gantt loading and scheduling charts 3. Apply the assignment method for loading jobs
15 - 5 © 2014 Pearson Education, Inc. When you complete this chapter you should be able to: Learning Objectives 4. Name and describe each of the priority sequencing rules 5. Use Johnson’s rule 6. Define finite capacity scheduling 7. Use the cyclical scheduling technique
15 - 6 © 2014 Pearson Education, Inc. Delta Airlines ► About 10% of Delta’s flights are disrupted per year, half because of weather ► Cost is $440 million in lost revenue, overtime pay, food and lodging vouchers ► The $33 million Operations Control Center adjusts to changes and keeps flights flowing ► Saves Delta $35 million per year © 2014 Pearson Education, Inc.
15 - 7 © 2014 Pearson Education, Inc. Short-Term Scheduling The objective of scheduling is to allocate and prioritize demand (generated by either forecasts or customer orders) to available facilities
15 - 8 © 2014 Pearson Education, Inc. Importance of Short-Term Scheduling ▶Effective and efficient scheduling can be a competitive advantage ▶Faster movement of goods through a facility means better use of assets and lower costs ▶Additional capacity resulting from faster throughput improves customer service through faster delivery ▶Good schedules result in more dependable deliveries
15 - 9 © 2014 Pearson Education, Inc. Scheduling Issues ▶Scheduling deals with the timing of operations ▶The task is the allocation and prioritization of demand ▶Significant factors are 1. Forward or backward scheduling 2. Finite or infinite loading 3. The criteria for sequencing jobs
15 - 10 © 2014 Pearson Education, Inc. Scheduling Decisions TABLE 15.1 Scheduling Decisions ORGANIZATION MANAGERS SCHEDULE THE FOLLOWING Delta Air Lines Maintenance of aircraft Departure timetables Flight crews, catering, gate, ticketing personnel Arnold Palmer Hospital Operating room use Patient admissions Nursing, security, maintenance staffs Outpatient treatments University of Alabama Classrooms and audiovisual equipment Student and instructor schedules Graduate and undergraduate courses Amway Center Ushers, ticket takers, food servers, security personnel Delivery of fresh foods and meal preparation Orlando Magic games, concerts, arena football Lockheed Martin Factory Production of goods Purchases of materials Workers
15 - 11 © 2014 Pearson Education, Inc. Figure 15.1 Scheduling Flow
15 - 12 © 2014 Pearson Education, Inc. Forward and Backward Scheduling ▶Forward scheduling starts as soon as the requirements are known ▶Produces a feasible schedule though it may not meet due dates ▶Frequently results in buildup of work-in- process inventory Due Date Now
15 - 13 © 2014 Pearson Education, Inc. Forward and Backward Scheduling ▶Backward scheduling begins with the due date and schedules the final operation first ▶Schedule is produced by working backwards though the processes ▶Resources may not be available to accomplish the schedule Due Date Now
15 - 14 © 2014 Pearson Education, Inc. ▶Backward scheduling begins with the due date and schedules the final operation first ▶Schedule is produced by working backwards though the processes ▶Resources may not be available to accomplish the schedule Forward and Backward Scheduling Due Date Now
15 - 15 © 2014 Pearson Education, Inc. Finite and Infinite Loading ▶Assigning jobs to work stations ▶Finite loading assigns work up to the capacity of the work station ▶All work gets done ▶Due dates may be pushed out ▶Infinite loading does not consider capacity ▶All due dates are met ▶Capacities may have to be adjusted
15 - 16 © 2014 Pearson Education, Inc. Scheduling Criteria 1. Minimize completion time 2. Maximize utilization of facilities 3. Minimize work-in-process (WIP) inventory 4. Minimize customer waiting time
15 - 17 © 2014 Pearson Education, Inc. Different Processes/ Different Approaches TABLE 15.2 Different Processes Suggest Different Approaches to Scheduling Process-focused facilities (job shops) ► Scheduling to customer orders where changes in both volume and variety of jobs/clients/patients are frequent ► Schedules are often due-date focused, with loading refined by finite loading techniques ► Examples: foundries, machine shops, cabinet shops, print shops, many restaurants, and the fashion industry Repetitive facilities (assembly lines) ► Schedule module production and product assembly based on frequent forecasts ► Finite loading with a focus on generating a forward-looking schedule ► JIT techniques are used to schedule components that feed the assembly line ► Examples: assembly lines for washing machines at Whirlpool and automobiles at Ford.
15 - 18 © 2014 Pearson Education, Inc. Different Processes/ Different Approaches TABLE 15.2 Different Processes Suggest Different Approaches to Scheduling Product-focused facilities (continuous) ► Schedule high volume finished products of limited variety to meet a reasonably stable demand within existing fixed capacity ► Finite loading with a focus on generating a forward-looking schedule that can meet known setup and run times for the limited range of products ► Examples: huge paper machines at International Paper, beer in a brewery at Anheuser-Busch, and potato chips at Frito-Lay
15 - 19 © 2014 Pearson Education, Inc. Focus for Different Process Strategies Product-focused (continuous) Schedule finished product Repetitive facilities (assemble lines) Schedule modules Process-focused (job shops) Schedule orders Examples: Print shop Motorcycles Steel, Beer, Bread Machine shop Autos, TVs Lightbulbs Fine-dining restaurant Fast-food restaurant Paper Typical focus of the master production schedule Number of inputs Number of end items
15 - 20 © 2014 Pearson Education, Inc. Scheduling Process- Focused Facilities ▶High-variety, low volume ▶Production differ considerably ▶Schedule incoming orders without violating capacity constraints ▶Scheduling can be complex
15 - 21 © 2014 Pearson Education, Inc. Loading Jobs ▶Assign jobs so that costs, idle time, or completion time are minimized ▶Two forms of loading ▶Capacity oriented ▶Assigning specific jobs to work centers
15 - 22 © 2014 Pearson Education, Inc. Input-Output Control ▶Identifies overloading and underloading conditions ▶Prompts managerial action to resolve scheduling problems ▶Can be maintained using ConWIP cards that control the scheduling of batches
15 - 23 © 2014 Pearson Education, Inc. Input-Output Control Example Week Ending 6/6 6/13 6/20 6/27 7/4 7/11 Planned Input 280 280 280 280 280 Actual Input 270 250 280 285 280 Cumulative Deviation –10 –40 –40 –35 Planned Output 320 320 320 320 Actual Output 270 270 270 270 Cumulative Deviation –50 –100 –150 –200 Cumulative Change in Backlog 0 –20 –10 +5 Figure 15.2 Work Center DNC Milling (in standard hours)
15 - 24 © 2014 Pearson Education, Inc. Input-Output Control Example Week Ending 6/6 6/13 6/20 6/27 7/4 7/11 Planned Input 280 280 280 280 280 Actual Input 270 250 280 285 280 Cumulative Deviation –10 –40 –40 –35 Planned Output 320 320 320 320 Actual Output 270 270 270 270 Cumulative Deviation –50 –100 –150 –200 Cumulative Change in Backlog 0 –20 –10 +5 Figure 15.2 Work Center DNC Milling (in standard hours) Explanation: 270 input, 270 output implies 0 change Explanation: 250 input, 270 output implies –20 change
15 - 25 © 2014 Pearson Education, Inc. Input-Output Control Example Options available to operations personnel include: 1. Correcting performances 2. Increasing capacity 3. Increasing or reducing input to the work center
15 - 26 © 2014 Pearson Education, Inc. Gantt Charts ▶Load chart shows the loading and idle times of departments, machines, or facilities ▶Displays relative workloads over time ▶Schedule chart monitors jobs in process ▶All Gantt charts need to be updated frequently to account for changes
15 - 27 © 2014 Pearson Education, Inc. Gantt Load Chart Example Figure 15.3 Day Monday Tuesday Wednesday Thursday Friday Work Center Metalworks Mechanical Electronics Painting Job 349 Job 349 Job 349 Job 408 Job 408 Job 408 Processing Unscheduled Center not available Job 350 Job 349 Job 295
15 - 28 © 2014 Pearson Education, Inc. Gantt Schedule Chart Example Figure 15.4 Job Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8 A B C Now Maintenance Start of an activity End of an activity Scheduled activity time allowed Actual work progress Nonproduction time Point in time when chart is reviewed
15 - 29 © 2014 Pearson Education, Inc. Assignment Method ▶A special class of linear programming models that assigns tasks or jobs to resources ▶Objective is to minimize cost or time ▶Only one job (or worker) is assigned to one machine (or project)
15 - 30 © 2014 Pearson Education, Inc. Assignment Method ▶Build a table of costs or time associated with particular assignments TYPESETTER JOB A B C R-34 $11 $14 $ 6 S-66 $ 8 $10 $11 T-50 $ 9 $12 $ 7
15 - 31 © 2014 Pearson Education, Inc. Assignment Method 1. Create zero opportunity costs by repeatedly subtracting the lowest costs from each row and column 2. Draw the minimum number of vertical and horizontal lines necessary to cover all the zeros in the table. If the number of lines equals either the number of rows or the number of columns, proceed to step 4. Otherwise proceed to step 3.
15 - 32 © 2014 Pearson Education, Inc. Assignment Method 3. Subtract the smallest number not covered by a line from all other uncovered numbers. Add the same number to any number at the intersection of two lines. Return to step 2. 4. Optimal assignments are at zero locations in the table. Select one, draw lines through the row and column involved, and continue to the next assignment.
15 - 33 © 2014 Pearson Education, Inc. Assignment Example A B C Job R-34 $11 $14 $ 6 S-66 $ 8 $10 $11 T-50 $ 9 $12 $ 7 Typesetter A B C Job R-34 $ 5 $ 8 $ 0 S-66 $ 0 $ 2 $ 3 T-50 $ 2 $ 5 $ 0 Typesetter Step 1a - Rows A B C Job R-34 $ 5 $ 6 $ 0 S-66 $ 0 $ 0 $ 3 T-50 $ 2 $ 3 $ 0 Typesetter Step 1b - Columns
15 - 34 © 2014 Pearson Education, Inc. Assignment Example Step 2 - Lines A B C Job R-34 $ 5 $ 6 $ 0 S-66 $ 0 $ 0 $ 3 T-50 $ 2 $ 3 $ 0 Typesetter Because only two lines are needed to cover all the zeros, the solution is not optimal Step 3 - Subtraction A B C Job R-34 $ 3 $ 4 $ 0 S-66 $ 0 $ 0 $ 5 T-50 $ 0 $ 1 $ 0 Typesetter The smallest uncovered number is 2 so this is subtracted from all other uncovered numbers and added to numbers at the intersection of lines Smallest uncovered number
15 - 35 © 2014 Pearson Education, Inc. Assignment Example Because three lines are needed, the solution is optimal and assignments can be made Step 2 - Lines A B C Job R-34 $ 3 $ 4 $ 0 S-66 $ 0 $ 0 $ 5 T-50 $ 0 $ 1 $ 0 Typesetter Start by assigning R-34 to worker C as this is the only possible assignment for worker C. Step 4 - Assignments A B C Job R-34 $ 3 $ 4 $ 0 S-66 $ 0 $ 0 $ 5 T-50 $ 0 $ 1 $ 0 Typesetter Job T-50 must go to worker A as worker C is already assigned. This leaves S-66 for worker B.
15 - 36 © 2014 Pearson Education, Inc. A B C Job R-34 $ 3 $ 4 $ 0 S-66 $ 0 $ 0 $ 5 T-50 $ 0 $ 1 $ 0 Typesetter Assignment Example From the original cost table Minimum cost = $6 + $10 + $9 = $25 A B C Job R-34 $11 $14 $ 6 S-66 $ 8 $10 $11 T-50 $ 9 $12 $ 7 Typesetter
15 - 37 © 2014 Pearson Education, Inc. Sequencing Jobs ▶Specifies the order in which jobs should be performed at work centers ▶Priority rules are used to dispatch or sequence jobs ▶FCFS: First come, first served ▶SPT: Shortest processing time ▶EDD: Earliest due date ▶LPT: Longest processing time
15 - 38 © 2014 Pearson Education, Inc. Sequencing Example Job Job Work (Processing) Time (Days) Job Due Date (Days) A 6 8 B 2 6 C 8 18 D 3 15 E 9 23 Apply the four popular sequencing rules to these five jobs
15 - 39 © 2014 Pearson Education, Inc. Sequencing Example Job Sequence Job Work (Processing) Time Flow Time Job Due Date Job Lateness A 6 6 8 0 B 2 8 6 2 C 8 16 18 0 D 3 19 15 4 E 9 28 23 5 28 77 11 FCFS: Sequence A-B-C-D-E
15 - 40 © 2014 Pearson Education, Inc. Sequencing Example FCFS: Sequence A-B-C-D-E Average completion time = = 77/5 = 15.4 days Sum of total flow time Number of jobs Utilization metric = = 28/77 = 36.4% Total job work time Sum of total flow time Average number of jobs in the system = = 77/28 = 2.75 jobs Sum of total flow time Total job work time Average job lateness = = 11/5 = 2.2 days Total late days Number of jobs
15 - 41 © 2014 Pearson Education, Inc. Sequencing Example SPT: Sequence B-D-A-C-E Job Sequence Job Work (Processing) Time Flow Time Job Due Date Job Lateness B 2 2 6 0 D 3 5 15 0 A 6 11 8 3 C 8 19 18 1 E 9 28 23 5 28 65 9
15 - 42 © 2014 Pearson Education, Inc. Sequencing Example SPT: Sequence B-D-A-C-E Average completion time = = 65/5 = 13 days Sum of total flow time Number of jobs Utilization metric = = 28/65 = 43.1% Total job work time Sum of total flow time Average number of jobs in the system = = 65/28 = 2.32 jobs Sum of total flow time Total job work time Average job lateness = = 9/5 = 1.8 days Total late days Number of jobs
15 - 43 © 2014 Pearson Education, Inc. Job Sequence Job Work (Processing) Time Flow Time Job Due Date Job Lateness B 2 2 6 0 A 6 8 8 0 D 3 11 15 0 C 8 19 18 1 E 9 28 23 5 28 68 6 Sequencing Example EDD: Sequence B-A-D-C-E
15 - 44 © 2014 Pearson Education, Inc. Sequencing Example EDD: Sequence B-A-D-C-E Average completion time = = 68/5 = 13.6 days Sum of total flow time Number of jobs Utilization metric = = 28/68 = 41.2% Total job work time Sum of total flow time Average number of jobs in the system = = 68/28 = 2.43 jobs Sum of total flow time Total job work time Average job lateness = = 6/5 = 1.2 days Total late days Number of jobs
15 - 45 © 2014 Pearson Education, Inc. Job Sequence Job Work (Processing) Time Flow Time Job Due Date Job Lateness E 9 9 23 0 C 8 17 18 0 A 6 23 8 15 D 3 26 15 11 B 2 28 6 22 28 103 48 Sequencing Example LPT: Sequence E-C-A-D-B
15 - 46 © 2014 Pearson Education, Inc. Sequencing Example LPT: Sequence E-C-A-D-B Average completion time = = 103/5 = 20.6 days Sum of total flow time Number of jobs Utilization metric = = 28/103 = 27.2% Total job work time Sum of total flow time Average number of jobs in the system = = 103/28 = 3.68 jobs Sum of total flow time Total job work time Average job lateness = = 48/5 = 9.6 days Total late days Number of jobs
15 - 47 © 2014 Pearson Education, Inc. Sequencing Example Rule Average Completion Time (Days) Utilization Metric (%) Average Number of Jobs in System Average Lateness (Days) FCFS 15.4 36.4 2.75 2.2 SPT 13.0 43.1 2.32 1.8 EDD 13.6 41.2 2.43 1.2 LPT 20.6 27.2 3.68 9.6 Summary of Rules
15 - 48 © 2014 Pearson Education, Inc. Comparison of Sequencing Rules ▶No one sequencing rule excels on all criteria 1. SPT does well on minimizing flow time and number of jobs in the system ► But SPT moves long jobs to the end which may result in dissatisfied customers 2. FCFS does not do especially well (or poorly) on any criteria but is perceived as fair by customers 3. EDD minimizes maximum lateness
15 - 49 © 2014 Pearson Education, Inc. Critical Ratio (CR) ▶An index number found by dividing the time remaining until the due date by the work time remaining on the job ▶Jobs with low critical ratios are scheduled ahead of jobs with higher critical ratios ▶Performs well on average job lateness criteria CR = = Due date – Today’s date Work (lead) time remaining Time remaining Workdays remaining
15 - 50 © 2014 Pearson Education, Inc. Critical Ratio Example JOB DUE DATE WORKDAYS REMAINING A 30 4 B 28 5 C 27 2 Currently Day 25 With CR < 1, Job B is late. Job C is just on schedule and Job A has some slack time. JOB CRITICAL RATIO PRIORITY ORDER A (30 - 25)/4 = 1.25 3 B (28 - 25)/5 = .60 1 C (27 - 25)/2 = 1.00 2
15 - 51 © 2014 Pearson Education, Inc. Critical Ratio Technique 1. Helps determine the status of specific jobs 2. Establishes relative priorities among jobs on a common basis 3. Adjusts priorities automatically for changes in both demand and job progress 4. Dynamically tracks job progress
15 - 52 © 2014 Pearson Education, Inc. Sequencing N Jobs on Two Machines: Johnson’s Rule ▶Works with two or more jobs that pass through the same two machines or work centers ▶Minimizes total production time and idle time ▶An N/2 problem, N number of jobs through 2 workstations
15 - 53 © 2014 Pearson Education, Inc. Johnson’s Rule 1. List all jobs and times for each work center 2. Choose the job with the shortest activity time. If that time is in the first work center, schedule the job first. If it is in the second work center, schedule the job last. 3. Once a job is scheduled, it is eliminated from the list 4. Repeat steps 2 and 3 working toward the center of the sequence
15 - 54 © 2014 Pearson Education, Inc. Johnson’s Rule Example JOB WORK CENTER 1 (DRILL PRESS) WORK CENTER 2 (LATHE) A 5 2 B 3 6 C 8 4 D 10 7 E 7 12
15 - 55 © 2014 Pearson Education, Inc. A C Johnson’s Rule Example B D E JOB WORK CENTER 1 (DRILL PRESS) WORK CENTER 2 (LATHE) A 5 2 B 3 6 C 8 4 D 10 7 E 7 12
15 - 56 © 2014 Pearson Education, Inc. Johnson’s Rule Example Time 0 3 10 20 28 33 B A C D E WC 1 WC 2 B A C D E JOB WORK CENTER 1 (DRILL PRESS) WORK CENTER 2 (LATHE) A 5 2 B 3 6 C 8 4 D 10 7 E 7 12 Idle Job completed
15 - 57 © 2014 Pearson Education, Inc. Johnson’s Rule Example Time 0 3 10 20 28 33 Time 0 1 3 5 7 9 10 11 12 13 17 19 21 22 2325 27 29 31 33 35 B A C D E B A C D E WC 1 WC 2 B E D C A B A C D E JOB WORK CENTER 1 (DRILL PRESS) WORK CENTER 2 (LATHE) A 5 2 B 3 6 C 8 4 D 10 7 E 7 12 Idle Job completed
15 - 58 © 2014 Pearson Education, Inc. Limitations of Rule-Based Dispatching Systems 1. Scheduling is dynamic and rules need to be revised to adjust to changes 2. Rules do not look upstream or downstream 3. Rules do not look beyond due dates
15 - 59 © 2014 Pearson Education, Inc. Finite Capacity Scheduling ▶Overcomes disadvantages of rule-based systems by providing an interactive, computer-based graphical system ▶May include rules and expert systems or simulation to allow real-time response to system changes ▶FCS allows the balancing of delivery needs and efficiency
15 - 60 © 2014 Pearson Education, Inc. Finite Capacity Scheduling Planning Data • Master schedule • BOM • Inventory Priority rules • Expert systems • Simulation models • Routing files • Work center information Tooling and other resources Setups and run time Figure 15.5 Interactive Finite Capacity Scheduling
15 - 61 © 2014 Pearson Education, Inc. Finite Capacity Scheduling Figure 15.6
15 - 62 © 2014 Pearson Education, Inc. Scheduling Services Service systems differ from manufacturing MANUFACTURING SERVICES Schedules machines and materials Schedule staff Inventories used to smooth demand Seldom maintain inventories Machine-intensive and demand may be smooth Labor-intensive and demand may be variable Scheduling may be bound by union contracts Legal issues may constrain flexible scheduling Few social or behavioral issues Social and behavioral issues may be quite important
15 - 63 © 2014 Pearson Education, Inc. Scheduling Services ▶Hospitals have complex scheduling system to handle complex processes and material requirements ▶Banks use a cross-trained and flexible workforce and part-time workers ▶Retail stores use scheduling optimization systems that track sales, transactions, and customer traffic to create work schedules in less time and with improved customer satisfaction
15 - 64 © 2014 Pearson Education, Inc. Scheduling Services ▶Airlines must meet complex FAA and union regulations and often use linear programming to develop optimal schedules ▶24/7 operations like police/fire departments, emergency hot lines, and mail order businesses use flexible workers and variable schedules, often created using computerized systems
15 - 65 © 2014 Pearson Education, Inc. Scheduling Service Employees With Cyclical Scheduling ▶Objective is to meet staffing requirements with the minimum number of workers ▶Schedules need to be smooth and keep personnel happy ▶Many techniques exist from simple algorithms to complex linear programming solutions
15 - 66 © 2014 Pearson Education, Inc. Cyclical Scheduling Example 1. Determine the staffing requirements 2. Identify two consecutive days with the lowest total requirements and assign these as days off 3. Make a new set of requirements subtracting the days worked by the first employee 4. Apply step 2 to the new row 5. Repeat steps 3 and 4 until all requirements have been met
15 - 67 © 2014 Pearson Education, Inc. Cyclical Scheduling Example M T W T F S S Employee 1 5 5 6 5 4 3 3 Capacity (Employees) Excess Capacity DAY M T W T F S S Staff required 5 5 6 5 4 3 3
15 - 68 © 2014 Pearson Education, Inc. Cyclical Scheduling Example M T W T F S S Employee 1 5 5 6 5 4 3 3 Employee 2 4 4 5 4 3 3 3 Capacity (Employees) Excess Capacity DAY M T W T F S S Staff required 5 5 6 5 4 3 3
15 - 69 © 2014 Pearson Education, Inc. Cyclical Scheduling Example M T W T F S S Employee 1 5 5 6 5 4 3 3 Employee 2 4 4 5 4 3 3 3 Employee 3 3 3 4 3 2 3 3 Capacity (Employees) Excess Capacity DAY M T W T F S S Staff required 5 5 6 5 4 3 3
15 - 70 © 2014 Pearson Education, Inc. Cyclical Scheduling Example M T W T F S S Employee 1 5 5 6 5 4 3 3 Employee 2 4 4 5 4 3 3 3 Employee 3 3 3 4 3 2 3 3 Employee 4 2 2 3 2 2 3 2 Capacity (Employees) Excess Capacity DAY M T W T F S S Staff required 5 5 6 5 4 3 3
15 - 71 © 2014 Pearson Education, Inc. Cyclical Scheduling Example M T W T F S S Employee 1 5 5 6 5 4 3 3 Employee 2 4 4 5 4 3 3 3 Employee 3 3 3 4 3 2 3 3 Employee 4 2 2 3 2 2 3 2 Employee 5 1 1 2 2 2 2 1 Capacity (Employees) Excess Capacity DAY M T W T F S S Staff required 5 5 6 5 4 3 3
15 - 72 © 2014 Pearson Education, Inc. Cyclical Scheduling Example M T W T F S S Employee 1 5 5 6 5 4 3 3 Employee 2 4 4 5 4 3 3 3 Employee 3 3 3 4 3 2 3 3 Employee 4 2 2 3 2 2 3 2 Employee 5 1 1 2 2 2 2 1 Employee 6 1 1 1 1 1 1 0 Capacity (Employees) Excess Capacity DAY M T W T F S S Staff required 5 5 6 5 4 3 3
15 - 73 © 2014 Pearson Education, Inc. Cyclical Scheduling Example M T W T F S S Employee 1 5 5 6 5 4 3 3 Employee 2 4 4 5 4 3 3 3 Employee 3 3 3 4 3 2 3 3 Employee 4 2 2 3 2 2 3 2 Employee 5 1 1 2 2 2 2 1 Employee 6 1 1 1 1 1 1 0 Employee 7 1 Capacity (Employees) 5 5 6 5 4 3 3 Excess Capacity 0 0 0 0 0 1 0 DAY M T W T F S S Staff required 5 5 6 5 4 3 3
15 - 74 © 2014 Pearson Education, Inc. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America.

More Related Content

PPTX
Session 15-16_Lean and TPS and lean.pptx
SupAki1
 
PPT
16. hr_om11_ch16_GE_ JIT, Lean Operations, and the Toyota Production System.ppt
MuhammadSuryanto4
 
PDF
Heizer om10 ch15
ryaekle
 
PPT
14.hr_om11_ch14_GE_Material Requirements Planning (MRP).ppt
MuhammadSuryanto4
 
PPTX
heizer_om12_ch014 final (1).pptx
kikikikiyowooo
 
PPTX
Inventory Management didalam perusahaan indusrty
NofrizalDewanto
 
PPT
week 1 operation & productivity.ppt
devina81
 
PPTX
Ch12-Inventory.pptx
Dinesh Saini
 
Session 15-16_Lean and TPS and lean.pptx
SupAki1
 
16. hr_om11_ch16_GE_ JIT, Lean Operations, and the Toyota Production System.ppt
MuhammadSuryanto4
 
Heizer om10 ch15
ryaekle
 
14.hr_om11_ch14_GE_Material Requirements Planning (MRP).ppt
MuhammadSuryanto4
 
heizer_om12_ch014 final (1).pptx
kikikikiyowooo
 
Inventory Management didalam perusahaan indusrty
NofrizalDewanto
 
week 1 operation & productivity.ppt
devina81
 
Ch12-Inventory.pptx
Dinesh Saini
 

Similar to hr_om11_ch15.ppt (20)

PDF
Ss 07 cost engineering management training- nov 2017 moustafa part ii ch 14...
Moustafa Ismail Abu Dief
 
PPT
2. Manajemen Proyek.ppt management Operasi
ulfaazizah15
 
PPT
hr_om11_ch03.ppt
GaudenceKapinga
 
PPT
hr_om11_ch03.ppt
SharanabasappaDegoan
 
PPT
1. Operation and Productivity Jay H & Barry R.ppt
ulfaazizah15
 
PPT
Inventory Management.ppt
SRIDEVIVVMSG
 
PPTX
OPERATIONAL PLAN
Muhammed Nowfal S
 
PPT
Lecture 10_Inventory Management.ppt
MaiLinh301193
 
PPT
Production and service operations planning
Divya Paulose
 
PPT
Operational Management Chapter - [01].ppt
AhmedAlrashid7
 
PPT
502423 hr om11_ch01_ge (2)
tehreem fatima
 
PDF
Company Profile of Muninmax 2015
GfK
 
PDF
Equipment for Food and Beverage Industry (update 2015) (Extractor, Sterilizat...
GfK
 
PDF
Job description factory services engineer
Babatunde Sofoluwe
 
DOCX
GNB LATEST
Gopinath Bhowmik
 
DOCX
GNB LATEST
Gopinath Bhowmik
 
DOCX
SOLVED SMU MBA ASSIGNMENTS AVAILABLE....
Naveen Kumar
 
PPTX
Ch07
Khaled Musheeb
 
PPT
MO AND PRODUCTIVITY.ppt
KurniaWidiP
 
PPTX
ebert_be10e_inppt07_mnewonepresentaion.pptx
kdiab1
 
Ss 07 cost engineering management training- nov 2017 moustafa part ii ch 14...
Moustafa Ismail Abu Dief
 
2. Manajemen Proyek.ppt management Operasi
ulfaazizah15
 
hr_om11_ch03.ppt
GaudenceKapinga
 
hr_om11_ch03.ppt
SharanabasappaDegoan
 
1. Operation and Productivity Jay H & Barry R.ppt
ulfaazizah15
 
Inventory Management.ppt
SRIDEVIVVMSG
 
OPERATIONAL PLAN
Muhammed Nowfal S
 
Lecture 10_Inventory Management.ppt
MaiLinh301193
 
Production and service operations planning
Divya Paulose
 
Operational Management Chapter - [01].ppt
AhmedAlrashid7
 
502423 hr om11_ch01_ge (2)
tehreem fatima
 
Company Profile of Muninmax 2015
GfK
 
Equipment for Food and Beverage Industry (update 2015) (Extractor, Sterilizat...
GfK
 
Job description factory services engineer
Babatunde Sofoluwe
 
GNB LATEST
Gopinath Bhowmik
 
GNB LATEST
Gopinath Bhowmik
 
SOLVED SMU MBA ASSIGNMENTS AVAILABLE....
Naveen Kumar
 
Ch07
Khaled Musheeb
 
MO AND PRODUCTIVITY.ppt
KurniaWidiP
 
ebert_be10e_inppt07_mnewonepresentaion.pptx
kdiab1
 
Ad

Recently uploaded (20)

PDF
FORM 1 BIOLOGY MIND MAPS and their schemes
arcade5
 
PDF
AI-driven educational solutions for real-life interventions in the Philippine...
EleniIlkou
 
PPTX
Chinmaya Tiranga Azadi Quiz (Class 7-8 )
Nitin Suresh
 
PDF
Computing-Curriculum for Schools in Ghana
abigailanane203
 
PDF
RTP_AR_KS1_Tutor's Guide_English [FOR REPRODUCTION].pdf
RobertMentino1
 
PDF
Practical Manual AGRO-233 Principles and Practices of Natural Farming
MilindKhedekar2
 
PDF
David L Page_DCI Research Study Journey_how Methodology can inform one's prac...
David L Page
 
PDF
احياء السادس العلمي - الفصل الثالث (التكاثر) منهج متميزين/كلية بغداد/موهوبين
S LS
 
PPTX
History, Philosophy and sociology of education (1).pptx
tmdth1
 
PDF
IGGE1 Understanding the Self1234567891011
rhea22labucay
 
PPTX
TNA_Presentation-1-Final(SAVE)) (1).pptx
RomnickTanilon
 
PPTX
Share_Module_2_Power_conflict_and_negotiation.pptx
Lavanyaj33
 
PDF
CISA (Certified Information Systems Auditor) Domain-Wise Summary.pdf
infosecTrain
 
PDF
A GUIDE TO GENETICS FOR UNDERGRADUATE MEDICAL STUDENTS
DrBincy A. S
 
PDF
MBA _Common_ 2nd year Syllabus _2021-22_.pdf
DrAnubha4
 
PDF
Hazard Identification & Risk Assessment .pdf
estagiarioprotegesms
 
PPTX
Virtual and Augmented Reality in Current Scenario
Shruti Dalela
 
PDF
Empowerment Technology for Senior High School Guide
solthereseamericandr
 
PDF
advance database management system book.pdf
hinamannan364
 
PDF
FOISHS ANNUAL IMPLEMENTATION PLAN 2025.pdf
EllenJoyCaniya2
 
FORM 1 BIOLOGY MIND MAPS and their schemes
arcade5
 
AI-driven educational solutions for real-life interventions in the Philippine...
EleniIlkou
 
Chinmaya Tiranga Azadi Quiz (Class 7-8 )
Nitin Suresh
 
Computing-Curriculum for Schools in Ghana
abigailanane203
 
RTP_AR_KS1_Tutor's Guide_English [FOR REPRODUCTION].pdf
RobertMentino1
 
Practical Manual AGRO-233 Principles and Practices of Natural Farming
MilindKhedekar2
 
David L Page_DCI Research Study Journey_how Methodology can inform one's prac...
David L Page
 
احياء السادس العلمي - الفصل الثالث (التكاثر) منهج متميزين/كلية بغداد/موهوبين
S LS
 
History, Philosophy and sociology of education (1).pptx
tmdth1
 
IGGE1 Understanding the Self1234567891011
rhea22labucay
 
TNA_Presentation-1-Final(SAVE)) (1).pptx
RomnickTanilon
 
Share_Module_2_Power_conflict_and_negotiation.pptx
Lavanyaj33
 
CISA (Certified Information Systems Auditor) Domain-Wise Summary.pdf
infosecTrain
 
A GUIDE TO GENETICS FOR UNDERGRADUATE MEDICAL STUDENTS
DrBincy A. S
 
MBA _Common_ 2nd year Syllabus _2021-22_.pdf
DrAnubha4
 
Hazard Identification & Risk Assessment .pdf
estagiarioprotegesms
 
Virtual and Augmented Reality in Current Scenario
Shruti Dalela
 
Empowerment Technology for Senior High School Guide
solthereseamericandr
 
advance database management system book.pdf
hinamannan364
 
FOISHS ANNUAL IMPLEMENTATION PLAN 2025.pdf
EllenJoyCaniya2
 
Ad

hr_om11_ch15.ppt

  • 1. 15 - 1 © 2014 Pearson Education, Inc. Short-Term Scheduling PowerPoint presentation to accompany Heizer and Render Operations Management, Eleventh Edition Principles of Operations Management, Ninth Edition PowerPoint slides by Jeff Heyl 15 © 2014 Pearson Education, Inc.
  • 2. 15 - 2 © 2014 Pearson Education, Inc. Outline ► Global Company Profile: Delta Air Lines ► The Importance of Short-Term Scheduling ► Scheduling Issues ► Scheduling Process-Focused Facilities
  • 3. 15 - 3 © 2014 Pearson Education, Inc. Outline - Continued ► Loading Jobs ► Scheduling Jobs ► Finite Capacity Scheduling (FCS) ► Scheduling Services
  • 4. 15 - 4 © 2014 Pearson Education, Inc. Learning Objectives When you complete this chapter you should be able to: 1. Explain the relationship between short- term scheduling, capacity planning, aggregate planning, and a master schedule 2. Draw Gantt loading and scheduling charts 3. Apply the assignment method for loading jobs
  • 5. 15 - 5 © 2014 Pearson Education, Inc. When you complete this chapter you should be able to: Learning Objectives 4. Name and describe each of the priority sequencing rules 5. Use Johnson’s rule 6. Define finite capacity scheduling 7. Use the cyclical scheduling technique
  • 6. 15 - 6 © 2014 Pearson Education, Inc. Delta Airlines ► About 10% of Delta’s flights are disrupted per year, half because of weather ► Cost is $440 million in lost revenue, overtime pay, food and lodging vouchers ► The $33 million Operations Control Center adjusts to changes and keeps flights flowing ► Saves Delta $35 million per year © 2014 Pearson Education, Inc.
  • 7. 15 - 7 © 2014 Pearson Education, Inc. Short-Term Scheduling The objective of scheduling is to allocate and prioritize demand (generated by either forecasts or customer orders) to available facilities
  • 8. 15 - 8 © 2014 Pearson Education, Inc. Importance of Short-Term Scheduling ▶Effective and efficient scheduling can be a competitive advantage ▶Faster movement of goods through a facility means better use of assets and lower costs ▶Additional capacity resulting from faster throughput improves customer service through faster delivery ▶Good schedules result in more dependable deliveries
  • 9. 15 - 9 © 2014 Pearson Education, Inc. Scheduling Issues ▶Scheduling deals with the timing of operations ▶The task is the allocation and prioritization of demand ▶Significant factors are 1. Forward or backward scheduling 2. Finite or infinite loading 3. The criteria for sequencing jobs
  • 10. 15 - 10 © 2014 Pearson Education, Inc. Scheduling Decisions TABLE 15.1 Scheduling Decisions ORGANIZATION MANAGERS SCHEDULE THE FOLLOWING Delta Air Lines Maintenance of aircraft Departure timetables Flight crews, catering, gate, ticketing personnel Arnold Palmer Hospital Operating room use Patient admissions Nursing, security, maintenance staffs Outpatient treatments University of Alabama Classrooms and audiovisual equipment Student and instructor schedules Graduate and undergraduate courses Amway Center Ushers, ticket takers, food servers, security personnel Delivery of fresh foods and meal preparation Orlando Magic games, concerts, arena football Lockheed Martin Factory Production of goods Purchases of materials Workers
  • 11. 15 - 11 © 2014 Pearson Education, Inc. Figure 15.1 Scheduling Flow
  • 12. 15 - 12 © 2014 Pearson Education, Inc. Forward and Backward Scheduling ▶Forward scheduling starts as soon as the requirements are known ▶Produces a feasible schedule though it may not meet due dates ▶Frequently results in buildup of work-in- process inventory Due Date Now
  • 13. 15 - 13 © 2014 Pearson Education, Inc. Forward and Backward Scheduling ▶Backward scheduling begins with the due date and schedules the final operation first ▶Schedule is produced by working backwards though the processes ▶Resources may not be available to accomplish the schedule Due Date Now
  • 14. 15 - 14 © 2014 Pearson Education, Inc. ▶Backward scheduling begins with the due date and schedules the final operation first ▶Schedule is produced by working backwards though the processes ▶Resources may not be available to accomplish the schedule Forward and Backward Scheduling Due Date Now
  • 15. 15 - 15 © 2014 Pearson Education, Inc. Finite and Infinite Loading ▶Assigning jobs to work stations ▶Finite loading assigns work up to the capacity of the work station ▶All work gets done ▶Due dates may be pushed out ▶Infinite loading does not consider capacity ▶All due dates are met ▶Capacities may have to be adjusted
  • 16. 15 - 16 © 2014 Pearson Education, Inc. Scheduling Criteria 1. Minimize completion time 2. Maximize utilization of facilities 3. Minimize work-in-process (WIP) inventory 4. Minimize customer waiting time
  • 17. 15 - 17 © 2014 Pearson Education, Inc. Different Processes/ Different Approaches TABLE 15.2 Different Processes Suggest Different Approaches to Scheduling Process-focused facilities (job shops) ► Scheduling to customer orders where changes in both volume and variety of jobs/clients/patients are frequent ► Schedules are often due-date focused, with loading refined by finite loading techniques ► Examples: foundries, machine shops, cabinet shops, print shops, many restaurants, and the fashion industry Repetitive facilities (assembly lines) ► Schedule module production and product assembly based on frequent forecasts ► Finite loading with a focus on generating a forward-looking schedule ► JIT techniques are used to schedule components that feed the assembly line ► Examples: assembly lines for washing machines at Whirlpool and automobiles at Ford.
  • 18. 15 - 18 © 2014 Pearson Education, Inc. Different Processes/ Different Approaches TABLE 15.2 Different Processes Suggest Different Approaches to Scheduling Product-focused facilities (continuous) ► Schedule high volume finished products of limited variety to meet a reasonably stable demand within existing fixed capacity ► Finite loading with a focus on generating a forward-looking schedule that can meet known setup and run times for the limited range of products ► Examples: huge paper machines at International Paper, beer in a brewery at Anheuser-Busch, and potato chips at Frito-Lay
  • 19. 15 - 19 © 2014 Pearson Education, Inc. Focus for Different Process Strategies Product-focused (continuous) Schedule finished product Repetitive facilities (assemble lines) Schedule modules Process-focused (job shops) Schedule orders Examples: Print shop Motorcycles Steel, Beer, Bread Machine shop Autos, TVs Lightbulbs Fine-dining restaurant Fast-food restaurant Paper Typical focus of the master production schedule Number of inputs Number of end items
  • 20. 15 - 20 © 2014 Pearson Education, Inc. Scheduling Process- Focused Facilities ▶High-variety, low volume ▶Production differ considerably ▶Schedule incoming orders without violating capacity constraints ▶Scheduling can be complex
  • 21. 15 - 21 © 2014 Pearson Education, Inc. Loading Jobs ▶Assign jobs so that costs, idle time, or completion time are minimized ▶Two forms of loading ▶Capacity oriented ▶Assigning specific jobs to work centers
  • 22. 15 - 22 © 2014 Pearson Education, Inc. Input-Output Control ▶Identifies overloading and underloading conditions ▶Prompts managerial action to resolve scheduling problems ▶Can be maintained using ConWIP cards that control the scheduling of batches
  • 23. 15 - 23 © 2014 Pearson Education, Inc. Input-Output Control Example Week Ending 6/6 6/13 6/20 6/27 7/4 7/11 Planned Input 280 280 280 280 280 Actual Input 270 250 280 285 280 Cumulative Deviation –10 –40 –40 –35 Planned Output 320 320 320 320 Actual Output 270 270 270 270 Cumulative Deviation –50 –100 –150 –200 Cumulative Change in Backlog 0 –20 –10 +5 Figure 15.2 Work Center DNC Milling (in standard hours)
  • 24. 15 - 24 © 2014 Pearson Education, Inc. Input-Output Control Example Week Ending 6/6 6/13 6/20 6/27 7/4 7/11 Planned Input 280 280 280 280 280 Actual Input 270 250 280 285 280 Cumulative Deviation –10 –40 –40 –35 Planned Output 320 320 320 320 Actual Output 270 270 270 270 Cumulative Deviation –50 –100 –150 –200 Cumulative Change in Backlog 0 –20 –10 +5 Figure 15.2 Work Center DNC Milling (in standard hours) Explanation: 270 input, 270 output implies 0 change Explanation: 250 input, 270 output implies –20 change
  • 25. 15 - 25 © 2014 Pearson Education, Inc. Input-Output Control Example Options available to operations personnel include: 1. Correcting performances 2. Increasing capacity 3. Increasing or reducing input to the work center
  • 26. 15 - 26 © 2014 Pearson Education, Inc. Gantt Charts ▶Load chart shows the loading and idle times of departments, machines, or facilities ▶Displays relative workloads over time ▶Schedule chart monitors jobs in process ▶All Gantt charts need to be updated frequently to account for changes
  • 27. 15 - 27 © 2014 Pearson Education, Inc. Gantt Load Chart Example Figure 15.3 Day Monday Tuesday Wednesday Thursday Friday Work Center Metalworks Mechanical Electronics Painting Job 349 Job 349 Job 349 Job 408 Job 408 Job 408 Processing Unscheduled Center not available Job 350 Job 349 Job 295
  • 28. 15 - 28 © 2014 Pearson Education, Inc. Gantt Schedule Chart Example Figure 15.4 Job Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8 A B C Now Maintenance Start of an activity End of an activity Scheduled activity time allowed Actual work progress Nonproduction time Point in time when chart is reviewed
  • 29. 15 - 29 © 2014 Pearson Education, Inc. Assignment Method ▶A special class of linear programming models that assigns tasks or jobs to resources ▶Objective is to minimize cost or time ▶Only one job (or worker) is assigned to one machine (or project)
  • 30. 15 - 30 © 2014 Pearson Education, Inc. Assignment Method ▶Build a table of costs or time associated with particular assignments TYPESETTER JOB A B C R-34 $11 $14 $ 6 S-66 $ 8 $10 $11 T-50 $ 9 $12 $ 7
  • 31. 15 - 31 © 2014 Pearson Education, Inc. Assignment Method 1. Create zero opportunity costs by repeatedly subtracting the lowest costs from each row and column 2. Draw the minimum number of vertical and horizontal lines necessary to cover all the zeros in the table. If the number of lines equals either the number of rows or the number of columns, proceed to step 4. Otherwise proceed to step 3.
  • 32. 15 - 32 © 2014 Pearson Education, Inc. Assignment Method 3. Subtract the smallest number not covered by a line from all other uncovered numbers. Add the same number to any number at the intersection of two lines. Return to step 2. 4. Optimal assignments are at zero locations in the table. Select one, draw lines through the row and column involved, and continue to the next assignment.
  • 33. 15 - 33 © 2014 Pearson Education, Inc. Assignment Example A B C Job R-34 $11 $14 $ 6 S-66 $ 8 $10 $11 T-50 $ 9 $12 $ 7 Typesetter A B C Job R-34 $ 5 $ 8 $ 0 S-66 $ 0 $ 2 $ 3 T-50 $ 2 $ 5 $ 0 Typesetter Step 1a - Rows A B C Job R-34 $ 5 $ 6 $ 0 S-66 $ 0 $ 0 $ 3 T-50 $ 2 $ 3 $ 0 Typesetter Step 1b - Columns
  • 34. 15 - 34 © 2014 Pearson Education, Inc. Assignment Example Step 2 - Lines A B C Job R-34 $ 5 $ 6 $ 0 S-66 $ 0 $ 0 $ 3 T-50 $ 2 $ 3 $ 0 Typesetter Because only two lines are needed to cover all the zeros, the solution is not optimal Step 3 - Subtraction A B C Job R-34 $ 3 $ 4 $ 0 S-66 $ 0 $ 0 $ 5 T-50 $ 0 $ 1 $ 0 Typesetter The smallest uncovered number is 2 so this is subtracted from all other uncovered numbers and added to numbers at the intersection of lines Smallest uncovered number
  • 35. 15 - 35 © 2014 Pearson Education, Inc. Assignment Example Because three lines are needed, the solution is optimal and assignments can be made Step 2 - Lines A B C Job R-34 $ 3 $ 4 $ 0 S-66 $ 0 $ 0 $ 5 T-50 $ 0 $ 1 $ 0 Typesetter Start by assigning R-34 to worker C as this is the only possible assignment for worker C. Step 4 - Assignments A B C Job R-34 $ 3 $ 4 $ 0 S-66 $ 0 $ 0 $ 5 T-50 $ 0 $ 1 $ 0 Typesetter Job T-50 must go to worker A as worker C is already assigned. This leaves S-66 for worker B.
  • 36. 15 - 36 © 2014 Pearson Education, Inc. A B C Job R-34 $ 3 $ 4 $ 0 S-66 $ 0 $ 0 $ 5 T-50 $ 0 $ 1 $ 0 Typesetter Assignment Example From the original cost table Minimum cost = $6 + $10 + $9 = $25 A B C Job R-34 $11 $14 $ 6 S-66 $ 8 $10 $11 T-50 $ 9 $12 $ 7 Typesetter
  • 37. 15 - 37 © 2014 Pearson Education, Inc. Sequencing Jobs ▶Specifies the order in which jobs should be performed at work centers ▶Priority rules are used to dispatch or sequence jobs ▶FCFS: First come, first served ▶SPT: Shortest processing time ▶EDD: Earliest due date ▶LPT: Longest processing time
  • 38. 15 - 38 © 2014 Pearson Education, Inc. Sequencing Example Job Job Work (Processing) Time (Days) Job Due Date (Days) A 6 8 B 2 6 C 8 18 D 3 15 E 9 23 Apply the four popular sequencing rules to these five jobs
  • 39. 15 - 39 © 2014 Pearson Education, Inc. Sequencing Example Job Sequence Job Work (Processing) Time Flow Time Job Due Date Job Lateness A 6 6 8 0 B 2 8 6 2 C 8 16 18 0 D 3 19 15 4 E 9 28 23 5 28 77 11 FCFS: Sequence A-B-C-D-E
  • 40. 15 - 40 © 2014 Pearson Education, Inc. Sequencing Example FCFS: Sequence A-B-C-D-E Average completion time = = 77/5 = 15.4 days Sum of total flow time Number of jobs Utilization metric = = 28/77 = 36.4% Total job work time Sum of total flow time Average number of jobs in the system = = 77/28 = 2.75 jobs Sum of total flow time Total job work time Average job lateness = = 11/5 = 2.2 days Total late days Number of jobs
  • 41. 15 - 41 © 2014 Pearson Education, Inc. Sequencing Example SPT: Sequence B-D-A-C-E Job Sequence Job Work (Processing) Time Flow Time Job Due Date Job Lateness B 2 2 6 0 D 3 5 15 0 A 6 11 8 3 C 8 19 18 1 E 9 28 23 5 28 65 9
  • 42. 15 - 42 © 2014 Pearson Education, Inc. Sequencing Example SPT: Sequence B-D-A-C-E Average completion time = = 65/5 = 13 days Sum of total flow time Number of jobs Utilization metric = = 28/65 = 43.1% Total job work time Sum of total flow time Average number of jobs in the system = = 65/28 = 2.32 jobs Sum of total flow time Total job work time Average job lateness = = 9/5 = 1.8 days Total late days Number of jobs
  • 43. 15 - 43 © 2014 Pearson Education, Inc. Job Sequence Job Work (Processing) Time Flow Time Job Due Date Job Lateness B 2 2 6 0 A 6 8 8 0 D 3 11 15 0 C 8 19 18 1 E 9 28 23 5 28 68 6 Sequencing Example EDD: Sequence B-A-D-C-E
  • 44. 15 - 44 © 2014 Pearson Education, Inc. Sequencing Example EDD: Sequence B-A-D-C-E Average completion time = = 68/5 = 13.6 days Sum of total flow time Number of jobs Utilization metric = = 28/68 = 41.2% Total job work time Sum of total flow time Average number of jobs in the system = = 68/28 = 2.43 jobs Sum of total flow time Total job work time Average job lateness = = 6/5 = 1.2 days Total late days Number of jobs
  • 45. 15 - 45 © 2014 Pearson Education, Inc. Job Sequence Job Work (Processing) Time Flow Time Job Due Date Job Lateness E 9 9 23 0 C 8 17 18 0 A 6 23 8 15 D 3 26 15 11 B 2 28 6 22 28 103 48 Sequencing Example LPT: Sequence E-C-A-D-B
  • 46. 15 - 46 © 2014 Pearson Education, Inc. Sequencing Example LPT: Sequence E-C-A-D-B Average completion time = = 103/5 = 20.6 days Sum of total flow time Number of jobs Utilization metric = = 28/103 = 27.2% Total job work time Sum of total flow time Average number of jobs in the system = = 103/28 = 3.68 jobs Sum of total flow time Total job work time Average job lateness = = 48/5 = 9.6 days Total late days Number of jobs
  • 47. 15 - 47 © 2014 Pearson Education, Inc. Sequencing Example Rule Average Completion Time (Days) Utilization Metric (%) Average Number of Jobs in System Average Lateness (Days) FCFS 15.4 36.4 2.75 2.2 SPT 13.0 43.1 2.32 1.8 EDD 13.6 41.2 2.43 1.2 LPT 20.6 27.2 3.68 9.6 Summary of Rules
  • 48. 15 - 48 © 2014 Pearson Education, Inc. Comparison of Sequencing Rules ▶No one sequencing rule excels on all criteria 1. SPT does well on minimizing flow time and number of jobs in the system ► But SPT moves long jobs to the end which may result in dissatisfied customers 2. FCFS does not do especially well (or poorly) on any criteria but is perceived as fair by customers 3. EDD minimizes maximum lateness
  • 49. 15 - 49 © 2014 Pearson Education, Inc. Critical Ratio (CR) ▶An index number found by dividing the time remaining until the due date by the work time remaining on the job ▶Jobs with low critical ratios are scheduled ahead of jobs with higher critical ratios ▶Performs well on average job lateness criteria CR = = Due date – Today’s date Work (lead) time remaining Time remaining Workdays remaining
  • 50. 15 - 50 © 2014 Pearson Education, Inc. Critical Ratio Example JOB DUE DATE WORKDAYS REMAINING A 30 4 B 28 5 C 27 2 Currently Day 25 With CR < 1, Job B is late. Job C is just on schedule and Job A has some slack time. JOB CRITICAL RATIO PRIORITY ORDER A (30 - 25)/4 = 1.25 3 B (28 - 25)/5 = .60 1 C (27 - 25)/2 = 1.00 2
  • 51. 15 - 51 © 2014 Pearson Education, Inc. Critical Ratio Technique 1. Helps determine the status of specific jobs 2. Establishes relative priorities among jobs on a common basis 3. Adjusts priorities automatically for changes in both demand and job progress 4. Dynamically tracks job progress
  • 52. 15 - 52 © 2014 Pearson Education, Inc. Sequencing N Jobs on Two Machines: Johnson’s Rule ▶Works with two or more jobs that pass through the same two machines or work centers ▶Minimizes total production time and idle time ▶An N/2 problem, N number of jobs through 2 workstations
  • 53. 15 - 53 © 2014 Pearson Education, Inc. Johnson’s Rule 1. List all jobs and times for each work center 2. Choose the job with the shortest activity time. If that time is in the first work center, schedule the job first. If it is in the second work center, schedule the job last. 3. Once a job is scheduled, it is eliminated from the list 4. Repeat steps 2 and 3 working toward the center of the sequence
  • 54. 15 - 54 © 2014 Pearson Education, Inc. Johnson’s Rule Example JOB WORK CENTER 1 (DRILL PRESS) WORK CENTER 2 (LATHE) A 5 2 B 3 6 C 8 4 D 10 7 E 7 12
  • 55. 15 - 55 © 2014 Pearson Education, Inc. A C Johnson’s Rule Example B D E JOB WORK CENTER 1 (DRILL PRESS) WORK CENTER 2 (LATHE) A 5 2 B 3 6 C 8 4 D 10 7 E 7 12
  • 56. 15 - 56 © 2014 Pearson Education, Inc. Johnson’s Rule Example Time 0 3 10 20 28 33 B A C D E WC 1 WC 2 B A C D E JOB WORK CENTER 1 (DRILL PRESS) WORK CENTER 2 (LATHE) A 5 2 B 3 6 C 8 4 D 10 7 E 7 12 Idle Job completed
  • 57. 15 - 57 © 2014 Pearson Education, Inc. Johnson’s Rule Example Time 0 3 10 20 28 33 Time 0 1 3 5 7 9 10 11 12 13 17 19 21 22 2325 27 29 31 33 35 B A C D E B A C D E WC 1 WC 2 B E D C A B A C D E JOB WORK CENTER 1 (DRILL PRESS) WORK CENTER 2 (LATHE) A 5 2 B 3 6 C 8 4 D 10 7 E 7 12 Idle Job completed
  • 58. 15 - 58 © 2014 Pearson Education, Inc. Limitations of Rule-Based Dispatching Systems 1. Scheduling is dynamic and rules need to be revised to adjust to changes 2. Rules do not look upstream or downstream 3. Rules do not look beyond due dates
  • 59. 15 - 59 © 2014 Pearson Education, Inc. Finite Capacity Scheduling ▶Overcomes disadvantages of rule-based systems by providing an interactive, computer-based graphical system ▶May include rules and expert systems or simulation to allow real-time response to system changes ▶FCS allows the balancing of delivery needs and efficiency
  • 60. 15 - 60 © 2014 Pearson Education, Inc. Finite Capacity Scheduling Planning Data • Master schedule • BOM • Inventory Priority rules • Expert systems • Simulation models • Routing files • Work center information Tooling and other resources Setups and run time Figure 15.5 Interactive Finite Capacity Scheduling
  • 61. 15 - 61 © 2014 Pearson Education, Inc. Finite Capacity Scheduling Figure 15.6
  • 62. 15 - 62 © 2014 Pearson Education, Inc. Scheduling Services Service systems differ from manufacturing MANUFACTURING SERVICES Schedules machines and materials Schedule staff Inventories used to smooth demand Seldom maintain inventories Machine-intensive and demand may be smooth Labor-intensive and demand may be variable Scheduling may be bound by union contracts Legal issues may constrain flexible scheduling Few social or behavioral issues Social and behavioral issues may be quite important
  • 63. 15 - 63 © 2014 Pearson Education, Inc. Scheduling Services ▶Hospitals have complex scheduling system to handle complex processes and material requirements ▶Banks use a cross-trained and flexible workforce and part-time workers ▶Retail stores use scheduling optimization systems that track sales, transactions, and customer traffic to create work schedules in less time and with improved customer satisfaction
  • 64. 15 - 64 © 2014 Pearson Education, Inc. Scheduling Services ▶Airlines must meet complex FAA and union regulations and often use linear programming to develop optimal schedules ▶24/7 operations like police/fire departments, emergency hot lines, and mail order businesses use flexible workers and variable schedules, often created using computerized systems
  • 65. 15 - 65 © 2014 Pearson Education, Inc. Scheduling Service Employees With Cyclical Scheduling ▶Objective is to meet staffing requirements with the minimum number of workers ▶Schedules need to be smooth and keep personnel happy ▶Many techniques exist from simple algorithms to complex linear programming solutions
  • 66. 15 - 66 © 2014 Pearson Education, Inc. Cyclical Scheduling Example 1. Determine the staffing requirements 2. Identify two consecutive days with the lowest total requirements and assign these as days off 3. Make a new set of requirements subtracting the days worked by the first employee 4. Apply step 2 to the new row 5. Repeat steps 3 and 4 until all requirements have been met
  • 67. 15 - 67 © 2014 Pearson Education, Inc. Cyclical Scheduling Example M T W T F S S Employee 1 5 5 6 5 4 3 3 Capacity (Employees) Excess Capacity DAY M T W T F S S Staff required 5 5 6 5 4 3 3
  • 68. 15 - 68 © 2014 Pearson Education, Inc. Cyclical Scheduling Example M T W T F S S Employee 1 5 5 6 5 4 3 3 Employee 2 4 4 5 4 3 3 3 Capacity (Employees) Excess Capacity DAY M T W T F S S Staff required 5 5 6 5 4 3 3
  • 69. 15 - 69 © 2014 Pearson Education, Inc. Cyclical Scheduling Example M T W T F S S Employee 1 5 5 6 5 4 3 3 Employee 2 4 4 5 4 3 3 3 Employee 3 3 3 4 3 2 3 3 Capacity (Employees) Excess Capacity DAY M T W T F S S Staff required 5 5 6 5 4 3 3
  • 70. 15 - 70 © 2014 Pearson Education, Inc. Cyclical Scheduling Example M T W T F S S Employee 1 5 5 6 5 4 3 3 Employee 2 4 4 5 4 3 3 3 Employee 3 3 3 4 3 2 3 3 Employee 4 2 2 3 2 2 3 2 Capacity (Employees) Excess Capacity DAY M T W T F S S Staff required 5 5 6 5 4 3 3
  • 71. 15 - 71 © 2014 Pearson Education, Inc. Cyclical Scheduling Example M T W T F S S Employee 1 5 5 6 5 4 3 3 Employee 2 4 4 5 4 3 3 3 Employee 3 3 3 4 3 2 3 3 Employee 4 2 2 3 2 2 3 2 Employee 5 1 1 2 2 2 2 1 Capacity (Employees) Excess Capacity DAY M T W T F S S Staff required 5 5 6 5 4 3 3
  • 72. 15 - 72 © 2014 Pearson Education, Inc. Cyclical Scheduling Example M T W T F S S Employee 1 5 5 6 5 4 3 3 Employee 2 4 4 5 4 3 3 3 Employee 3 3 3 4 3 2 3 3 Employee 4 2 2 3 2 2 3 2 Employee 5 1 1 2 2 2 2 1 Employee 6 1 1 1 1 1 1 0 Capacity (Employees) Excess Capacity DAY M T W T F S S Staff required 5 5 6 5 4 3 3
  • 73. 15 - 73 © 2014 Pearson Education, Inc. Cyclical Scheduling Example M T W T F S S Employee 1 5 5 6 5 4 3 3 Employee 2 4 4 5 4 3 3 3 Employee 3 3 3 4 3 2 3 3 Employee 4 2 2 3 2 2 3 2 Employee 5 1 1 2 2 2 2 1 Employee 6 1 1 1 1 1 1 0 Employee 7 1 Capacity (Employees) 5 5 6 5 4 3 3 Excess Capacity 0 0 0 0 0 1 0 DAY M T W T F S S Staff required 5 5 6 5 4 3 3
  • 74. 15 - 74 © 2014 Pearson Education, Inc. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America.