Need assignment done Operations Management: Sustainability and Supply Chain Management Third Canadian Edition Chapter 15 Short-Term Scheduling Copy -

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Operations Management: Sustainability and Supply Chain Management
Third Canadian Edition
Chapter 15
Short-Term Scheduling
Copyright 2020 Pearson Canada Inc.

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Outline (1 of 2)
Global Company Profile: Air Canada
The Importance of Short-Term Scheduling
Scheduling Issues
Scheduling Process-Focused Facilities
Loading Jobs

Outline (2 of 2)
Sequencing Jobs
Finite Capacity Scheduling (FCS)
Scheduling Repetitive Facilities
Scheduling Services

Learning Objectives (1 of 2)
When you complete this chapter you should be able to:
Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule
Draw Gantt loading and scheduling charts
Apply the assignment method for loading jobs
Name and describe each of the priority sequencing rules

Learning Objectives (2 of 2)
When you complete this chapter you should be able to:
Use Johnsons rule
Define finite capacity scheduling
Use the cyclical scheduling technique

Air Canada
About 10% of Air Canadas flights are disrupted per year, half because of weather
Cost is millions of dollars in lost revenue, overtime pay, food and lodging vouchers
The Operations Control Centre at Torontos Pearson Airport adjusts to changes, notifies passengers, and keeps flights flowing
Labour disruptions also causes delays

Weve all been stuck at the airport at one time or another. Air Canada and other airlines have worked hard to make such waits less frequent and less painful. Airline scheduling has been called the Mother of all scheduling problems, because the companies must schedule thousands of planes with interconnections daily, plus pilots and flight crews with all of their human resource constraints, plus local staff at each airport. This application is where mathematical programming really shines. The static scheduling problem is difficult enough, but the dynamic scheduling problem kicks in when a plane breaks down or Mother Nature gets nasty. One delayed plane can cause a ripple effect throughout the system. The interesting Global Company Profile in Chapter 15 describes how Air Canada handles the 10% of flights that are disrupted each year. The company has created a central control centre to anticipate and react to potential problems. The estimated annual savings are in millions of dollars paid for the high-tech nerve centre in just one year.
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Short-Term Scheduling
Short-term schedules translate capacity decisions, aggregate planning, and master schedules into job sequences and specific assignments of personnel, materials, and machinery

This slide defines short-term scheduling, the focus of Chapter 15. After all of the higher-level planning that the book has discussed, we finally see how to determine exactly what is produced and when.
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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

Good scheduling increases utilization rates on equipment, while producing items quicker and on-time more often.
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Scheduling Issues
Scheduling deals with the timing of operations
The task is the allocation and prioritization of demand
Significant issues are
The type of scheduling, forward or backward
The criteria for priorities

Companies schedule jobs (products or customers), resources (machines, rooms, and employees), and activities (maintenance, purchasing, etc.). The resulting schedules depend upon the priorities that management has deemed important. Slide 10 (Table 15.1) provides examples of scheduling activities at five different organizations.

LO 1: Explain the relationship between short-term scheduling, capacity planning, aggregate planning, and a master schedule.
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Scheduling Decisions
Table 15.1 Scheduling Decisions

Organization Managers Schedule the Following:

The Hospital for Sick Children Operating room use
Patient admissions
Nursing, security, maintenance staff
Outpatient treatments

University of Manitoba Classrooms and audiovisual equipment
Student and instructor schedules
Graduate and undergraduate courses

Magna International factory Production of goods
Purchases of materials
Workers

Hard Rock Cafe Chef, waiters, bartenders
Delivery of fresh foods
Entertainers
Opening of dining areas

Air Canada Maintenance of aircraft
Departure timetables
Flight crews, catering, gate, and ticketing personnel

Scheduling Flow

By this point in the book, students have been exposed to an array of planning functions at different levels of aggregation. This slide (Figure 15.1) does a nice job of showing where short-term scheduling fits in with the other planning functions
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Forward and Backward Scheduling (1 of 3)
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

Scheduling involves assigning due dates to specific jobs, but many jobs compete simultaneously for the same resources. These slides describe forward vs. backward scheduling. Forward scheduling (Slide 12) may be more appropriate in situations where customer orders arrive and the goal is to complete each order as soon as possible. Here due dates are not considered, causing some jobs to potentially be late. Backward scheduling (Slide 13), which may be more appropriate for repetitive manufacturing environments or for services with specific event times (a concert or a doctor appointment), attempts to produce a schedule that meets all due dates. However, the schedule may not be feasible given the available resources. Slide 14 informs us that the two scheduling approaches are often combined in an attempt to address the trade-off between schedules that are feasible given available resources and schedules that meet all customer due dates.
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Forward and Backward Scheduling (3 of 3)
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

Often these approaches are combined to develop a trade-off between a feasible schedule and customer due dates

Slide 14 informs us that the two scheduling approaches are often combined in an attempt to address the trade-off between schedules that are feasible given available resources and schedules that meet all customer due dates.
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Different Processes/Different Approaches
Table 15.2 Different Processes Suggest Different Approaches to Scheduling

Process-focused facilities Forward-looking schedules
MRP due dates
Finite capacity scheduling

Work cells Forward-looking schedules
MRP due dates
Detailed schedule done using work cell priority rules

Repetitive facilities Forward-looking schedule with a balanced line
Pull techniques for scheduling

Product-focused facilities Forward-looking schedule with stable demand and fixed capacity
Capacity, set-up, and run times known
Capacity limited by long-term capital investment

This slide is based on Table 15.2, which provides an overview of different processes and approaches to scheduling.
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Scheduling Criteria
Minimize completion time
Maximize utilization of facilities
Minimize work-in-process (WIP) inventory
Minimize customer waiting time
Optimize the use of resources so that production objectives are met

This slide identifies four important scheduling criteria. (Note that criteria 1 and 3 are often very highly correlated.) Other criteria may be used, such as minimizing the maximum lateness of any job, minimizing the average lateness for those jobs that are late, minimizing the number of late jobs, or some sort of fairness criterion for customers or employees. Determination of the most important criteria often drives which scheduling method to use.
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Scheduling Process-Focused Facilities (1 of 3)
Schedule incoming orders without violating capacity constraints
Check availability of tools and materials before releasing an order
Establish due dates for each job and check progress
Check work in progress
Provide feedback
Provide work efficiency statistics and monitor times

On a daily basis, job shops tend to be more difficult to schedule than assembly lines or continuous flow facilities due to the variety of products produced, different routes through the system that these products take, and unstable demand. (The product-focused facilities might be more likely to utilize mathematical programming to set a weekly or monthly schedule, but once in place, these schedules seldom need to be updatedcertainly not on a daily basis.) Slide 17 identifies the features that a good production planning and control system should incorporate.
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Scheduling Process-Focused Facilities (2 of 3)
Table 15.2 Different Processes Suggest Different Approaches to Scheduling

Process-focused facilities (job shops)

Focus is on generating a forward-looking schedule.

MRP generates due dates that are refined with finite capacity scheduling techniques.

Examples: foundries, machine shops, cabinet shops, print shops, many restaurants, and the fashion industry.

Work cells (focused facilities that process families of similar components)

Focus is on generating a forward-looking schedule.

MRP generates due dates, and subsequent detail scheduling/dispatching is done at the work cell with kanbans and priority rules.

Examples: work cells at ambulance manufacturer Wheeled Coach, aircraft engine rebuilder Standard Aero, greeting-card maker Hallmark.

Scheduling Process-Focused Facilities (3 of 3)
Table 15.2 Continued

Repetitive facilities (assembly lines)

Focus is on generating a forward-looking schedule that is achieved by balancing the line with traditional assembly-line techniques.

Pull techniques, such as JIT and kanban, signal component scheduling to support the assembly line.

Challenging scheduling problems typically occur only when the process is new or when products or models change.

Examples: assembly lines for a wide variety of products from autos to home appliances and computers.

Product-focused facilities (continuous)

Focus is on generating a forward-looking schedule that can meet a reasonably stable demand with the existing fixed capacity.

Capacity in such facilities is usually limited by long-term capital investment.

Capacity is usually known, as is the setup and run time for the limited range of products.

Examples: facilities with very high volume production and limited-variety products such as paper on huge machines at International Paper, beer in a brewery at Labatt Brewing Company, or rolled steel in a Dofasco plant.

Planning and Control Files
Planning Files
An item master file contains information about each component
A routing file indicates each components flow through the shop
A work-centre master file contains information about the work centre
Control Files
Track the actual progress made against the plan

This slide identifies the types of planning and control files that help to ensure that a scheduling system is accurate and relevant.
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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 centres

Loading means the assigning of jobs to work or processing centres. When loading is undertaken via the perspective of capacity, input-output control can be used. When loading is undertaken via assigning specific jobs to work centres, either Gantt charts or the assignment method of linear programming can be used.
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Input-Output Control (1 of 2)
Identifies overloading and underloading conditions
Prompts managerial action to resolve scheduling problems
Can be maintained using ConWIP cards that control the scheduling of batches

Slide 20: Input-output control compares arrival rates of new jobs to the capacity of the facility to identify overloading (too much work) or underloading (too much idleness) conditions. ConWIP (constant work-in-process) cards can be used to aid input-output control. Such cards control the amount of work in a work centre. Once the job has been completed, its ConWIP card is released and returned to the initial workstation, authorizing the entry of a new batch into the work centre. Note that the cumulative change in backlog must be computed as the sum of the actual inputs minus the sum of the actual outputs. When this value moves too far from 0, managers should consider actions such as those identified in Slide 21. Changing work centre input can be accomplished by (a) routing work to or from other work centres, (b) increasing or decreasing subcontracting, or (c) producing less (or more).
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Input-Output Control (2 of 2)
Options available to operations personnel include:
Correcting performances
Increasing capacity
Increasing or reducing input to the work centre

Note that the cumulative change in backlog must be computed as the sum of the actual inputs minus the sum of the actual outputs. When this value moves too far from 0, managers should consider actions such as those identified in Slide 21. Changing work centre input can be accomplished by (a) routing work to or from other work centres, (b) increasing or decreasing subcontracting, or (c) producing less (or more).
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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

Slide 22: Gantt charts are visual aids that are useful in loading and scheduling. The charts show the use of resources, such as work centres and labour. A Gantt load chart shows the relative workloads over time of departments, machines, or facilities. Managers can shift work between resources when overloading or underloading appears. A Gantt schedule chart shows jobs in process, indicating which are on schedule and which are behind or ahead of schedule. Again, this type of chart provides management with a quick visual aid to look for areas requiring action. Slide 23 (Example 2) provides an example of a load chart (here metalworks and painting are completely loaded for the entire week), and Slide 24 (Example 3) provides an example of a schedule chart (here job A is one-half day behind schedule, job B was completed on time, and job C is ahead of schedule).

LO2: Draw Gantt loading and scheduling charts.
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Gantt Load Chart Example

Slide 23 (Example 2) provides an example of a load chart (here metalworks and painting are completely loaded for the entire week).
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Gantt Schedule Chart Example

This slide (Example 3) provides an example of a schedule chart (here job A is one-half day behind schedule, job B was completed on time, and job C is ahead of schedule).
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Sequencing Jobs
Specifies the order in which jobs should be performed at work centres
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

LO 4: Name and describe each of the priority sequencing rules.

Once jobs are loaded, managers must decide the sequence in which they are to be completed (also called dispatching). Students regularly perform sequencing in their own lives when they decide in what order to work on their assignments or which of several errands to run first. This slide identifies the four most popular priority rules for sequencing. A nice feature of sequencing is that, before any processing begins, different priority rules can be easily tested and the results compared. In fact, the rule used might change from one application to another depending on comparison results.
When comparing sequencing rules the four main priority rules have to be applied to the same set of jobs waiting to be sequenced. Note that flow time is defined as total time in the system (waiting plus processing). Job lateness is computed as Max (0, flow time due date). (Here we assume no penalties for finishing early.) Clearly the lateness depends upon the sequence chosen. While total processing time will not depend upon the sequence, total flow time will because the flow time of any particular job in the sequence becomes part of the waiting time for all other jobs that follow. (This is why SPT is the rule that minimizes total flow timeoverall waiting is minimized by getting the quick jobs finished right away.) Four measures of effectiveness can be computed: (1) average completion time, (2) utilization metric, (3) average number of jobs in the system, and (4) average job lateness. Note that the first three measures are completely correlated, i.e., the rule that performs best on one will perform best on all three.
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Comparison of Sequencing Rules
No one sequencing rule excels on all criteria
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
FCFS does not do especially well (or poorly) on any criteria but is perceived as fair by customers
EDD minimizes maximum lateness

This slide provides general comparisons for the four common sequencing rules. While SPT does not always minimize average lateness, it does always minimize average completion time. A suggestion: When in doubt, use SPT. FCFS usually performs at a decent average level, and it has the prime advantage of being fair to customers. FCFS may be particularly appropriate when customers can see the queue of jobs (think about sitting in a restaurant and then watching a group who just entered get seated before you, or think about potential unfairness that arises with multiple grocery store lines). It is very important to emphasize that while EDD does minimize maximum lateness, it does not necessarily minimize average lateness or even number of late jobs. In fact, examples can be presented showing that EDD may perform very poorly on those lateness criteria. The basic idea is that if everything is scheduled via EDD, once the system falls behind, it may well remain behind for every single job that follows. This phenomenon is counter-intuitive and is one reason why students run into trouble meeting due dates during their semesters.
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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

If average lateness is the most important criterion, the critical ratio technique may the best one to use. Its in some sense a hybrid of EDD and LPT that examines the slack available for each job. Slide 35 provides the formula. A primary advantage of this technique is that the ratios can be recomputed after each job finishes, which potentially changes the remaining sequence after the slack conditions have changed. Slide 36 identifies benefits of the critical ratio technique in most production systems.
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Critical Ratio Technique
Helps determine the status of specific jobs
Establishes relative priorities among jobs on a common basis
Relates both stock and make-to-order jobs on a common basis
Adjusts priorities automatically for changes in both demand and job progress
Dynamically tracks job progress

Slide 36 identifies benefits of the critical ratio technique in most production systems.
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Limitations of Rule-Based Dispatching Systems
Scheduling is dynamic and rules need to be revised to adjust to changes
Rules do not look upstream or downstream
Rules do not look beyond due dates

This slide identifies three limitations of using myopic rule-based dispatching systems. Nevertheless, schedulers often apply one of these methods at each work centre and then modify the sequence to deal with a multitude of real-world variables. They may do this manually or with finite capacity scheduling software.
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Finite Capacity Scheduling (1 of 2)
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
Initial data often from an MRP system
FCS allows the balancing of delivery needs and efficiency

Finite capacity scheduling provides the scheduler with interactive computing and graphic output to help overcome the disadvantages of rule-based systems. FCS systems may allow virtually instantaneous schedule changes based on the most up-to-date information. Slide 45 (Figure 15.5) shows the different components that are combined to produce the Gantt chart output in FCS.

LO 6: Define finite capacity scheduling.
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Finite Capacity Scheduling (2 of 2)
Figure 15.5

Scheduling Repetitive Facilities (1 of 2)
Level material use can help repetitive facilities
Better satisfy customer demand
Lower inventory investment
Reduce batch size
Better utilize equipment and facilities

Level material use refers to the use of frequent, high-quality, small lot sizes that contribute to just-in-time production. These slides identify advantages to repetitive producers of implementing level material use.
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Scheduling Repetitive Facilities (2 of 2)
Advantages include:
Lower inventory levels
Faster product throughput
Improved component quality
Reduced floor-space requirements
Improved communications
Smoother production process

Scheduling Services (1 of 3)
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 Labour-intensive and demand may be variable

Scheduling may be bound by union contracts Legal issues may constrain flexible scheduling

Few social or behavioural issues Social and behavioural issues may be quite important

This slide presents several ways in which scheduling service systems differs from scheduling manufacturing systems. Some of these service characteristics appear in the Hard Rock Caf video case associated with this chapter.
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Scheduling Services (2 of 3)
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

The complexity of scheduling services is exemplified by the industries highlighted in these slides.
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Scheduling Services (3 of 3)
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

Demand Management
Appointment or reservation systems
FCFS sequencing rules
Discounts or other promotional schemes
When demand management is not feasible, managing capacity through staffing flexibility may be used

As seen in Chapter 13, demand management techniques can be employed to smooth production, in this case easing the burden on the service company workforce scheduler.
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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

Cyclical scheduling is utilized to develop a schedule with the minimum number of workers. Each employee is assigned to a shift and has time off. The steps used to address the staffing problem is described in Example 8 in the text.

LO 7: Use the cyclical scheduling technique.
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Summary
Scheduling involves the timing of operations to achieve efficient movement of units through a system
Proper scheduling, loading, and sequencing of jobs all increase outputs
Many techniques are used, such as:
Gantt charts, assignment method of scheduling, various priority rules
Critical-ratio rule, Johnsons rule, and finite capacity scheduling
Matching capacity to demand in service environments require different techniques

Copyright 2020 Pearson Canada Inc.
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ning
== Operations Management: Sustainability and Supply Chain Management
Third Canadian Edition
Chapter 14
Material Requirements Planning (MRP) and ERP
Copyright 2020 Pearson Canada Inc.

14 – #

Outline (1 of 2)
Global Company Profile: Wheeled Coach
Dependent Demand
Dependent Inventory Model Requirements
MRP Structure

Outline (2 of 2)
MRP Management
Lot-Sizing Techniques
Extensions of MRP
MRP In Services
Enterprise Resource Planning (ERP)

Learning Objectives (1 of 2)
When you complete this chapter you should be able to:
Develop a product structure
Build a gross requirements plan
Build a net requirements plan
Determine lot sizes for lot-for-lot, EOQ, and POQ

Learning Objectives (2 of 2)
When you complete this chapter you should be able to:
Describe MRP II
Describe closed-loop MRP
Describe ERP

Wheeled Coach (1 of 2)
Largest manufacturer of ambulances in the world
International competitor
12 major ambulance designs
18,000 different inventory items
6,000 manufactured parts
12,000 purchased parts

Because Wheeled Coach deals with so many parts for its custom-made assembled ambulances, an excellent MRP system is crucial for getting the right parts at the right place at the right time.
6

Wheeled Coach (2 of 2)
Four Key Tasks
Material plan must meet both the requirements of the master schedule and the capabilities of the production facility
Plan must be executed as designed
Minimize inventory investment
Maintain excellent record integrity

Dependent Demand (1 of 4)
For any product for which a schedule can be established, dependent demand techniques should be used

While Chapter 12 introduced techniques for independent demand, Chapter 14 illustrates how to handle dependent demand, which occurs when the demand for one item is dependent on the demand for another. In short, for all components that a firm produces to go into a final product, material requirements planning (MRP) determines when to begin producing them and in what quantities. Taking lead times into consideration, components are scheduled far enough in advance to ensure that the final product can be completed when scheduled. Slide 9 identifies four benefits of MRP.
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Dependent Demand (2 of 4)
Benefits of MRP
Better response to customer orders
Faster response to market changes
Improved utilization of facilities and labour
Reduced inventory levels

Dependent Demand (3 of 4)
The demand for one item is related to the demand for another item
Given a quantity for the end item, the demand for all parts and components can be calculated
In general, used whenever a schedule can be established for an item
MRP is the common technique

Dependent Demand (4 of 4)
Effective use of dependent demand inventory models requires the following
Master productio

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