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22–1. 22–2 Chapter Twenty-Two Copyright © 2014 by The McGraw-Hill Companies, Inc. All rights...
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Transcript of 22–1. 22–2 Chapter Twenty-Two Copyright © 2014 by The McGraw-Hill Companies, Inc. All rights...
22–1
Operations andSupply Chain Management
CHASE | SHANKAR | JACOBS
14e
22–2
Work Center Scheduling
Chapter Twenty-Two
Copyright © 2014 by The McGraw-Hill Companies, Inc. All rights reserved.McGraw-Hill/Irwin
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Learning Objectives
• LO22-1: Explain work center scheduling.
• LO22-2: Analyze scheduling problems using priority rules and more specialized techniques.
• LO22-3: Apply scheduling techniques to the manufacturing shop floor.
• LO22-4: Analyze employee schedules in the service sector.
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.Manufacturing Execution Systems
• Manufacturing execution system (MES): An information system that schedules, dispatches, tracks, monitors, and controls production– Real-time linkage to:
MRP Product and process planning Systems that extend beyond the factory
• Service execution system (SES): An information system that links schedules, dispatches, tracks, monitors, and controls the customer’s encounters with the service organization
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.The Nature and Importance of Work Centers
• Work center: an area in which production resources are organized and work is completed– May be a single machine, a group of
machines, or an area where work is done
– Can be organized according to function, product in a flow, or group technology
• Jobs need to be routed between functionally organized work centers to complete the work
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Loading
• Infinite loading: work is assigned to a work center based on what is needed– No consideration to capacity
• Finite loading: schedules each resource using the setup and run time required for each order– Determines exactly what will be done by
each resource at every moment during the day
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Scheduling
• Forward scheduling: the system takes an order and schedules each operation that must be completed forward in time– Can tell the earliest date an order can be
completed
• Backward scheduling: starts with due date and schedules the required operations in reverse sequence– Can tell when an order must be started in
order to be done by a specific date
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Limitations
• Machine-limited process: equipment is the critical resource that is scheduled
• Labor-limited process: people are the key resource that is scheduled
• Most actual processes are either labor limited or machine limited but not both
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Types of Manufacturing Processes and Scheduling Approaches
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Typical Scheduling and Control Functions
• Allocating orders, equipment, and personnel
• Determining the sequence of order performance
• Initiating performance of the scheduled work
• Shop-floor control
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Objectives of Work-Center Scheduling
• Meet due dates
• Minimize lead time
• Minimize setup time or cost
• Minimize work-in-process inventory
• Maximize machine utilization
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Job Sequencing
• Sequencing: the process of determining the job order on machines or work centers– Also known as priority sequencing
• Priority rules: the rules used in obtaining a job sequence– Can be simple or complex
– Can use one or more pieces of information
– Common rules shown on next slide
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.Priority Rules for Job Sequencing
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Standard Measures of Schedule Performance
• Meeting due dates
• Minimizing the flow time
• Minimizing work-in-process inventory
• Minimizing idle time
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Example 22.1: n Jobs on One Machine
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Example 22.1: FCFS and SOT Rules
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Example 22.1: EDD and LCFS Rules
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Example 22.1: Random and STR Rules
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.Comparison of Priority Rules
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Scheduling n Jobs on Two Machines
• Two or more jobs must be processed on two machines in a common sequence.
• Wish to minimize the flow time from the beginning of the first job to the finish of the last job.
• Use Johnson’s rule.
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.Steps to Johnson’s Rule
• List the operation time for each job.• Select the shortest operation time.• If the shortest time is on the first
machine, do first.– If the shortest time is on the second
machine, do the job last.– For ties, do first.
• Repeat steps 2-3 for each remaining job.
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Example 22.2: n Jobs on Two Machines
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.Example 22.2: Scheduling Jobs
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Example 22.2: Optimal Schedule of Jobs Using Johnson’s Rule
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Scheduling a Set Number of Jobs on the Same Number of Machines
• Some work centers have enough machines to start all the jobs.
• Here the issue is the particular assignment of individual jobs to individual machines.
• Assignment method: a special case of the transportation method of linear programming.– There are n things to be distributed to n
destinations.
– Each thing assigned to one and only one destination.
– Only one criterion can be used.
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Example 22.3: Assignment Method
Assignment Matrix Showing Machine Processing Costs for Each Job
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Example 22.3: Step 1– Row Reduction
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Example 22.3: Step 2 – Column Reduction
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Example 22.3: Step 3 – Apply Line Test
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Example 22.3: Step 4 – Additional Reduction
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.Example 22.3: Optimal Solution
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.Example 22.3: Optimal Assignment and Their Costs
Job I to Machine E $3
Job II to Machine B 4
Job III to Machine C 2
Job IV to Machine D 5
Job V to Machine A 3
Total Cost $17
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Shop-Floor Control: Major Functions
• Assigning priority of each shop order
• Maintaining WIP quantity information
• Conveying shop-order status information to the office
• Providing actual output data for capacity control purposes
• Providing quantity by location by shop order for WIP inventory and accounting
• Providing measurement of efficiency, utilization, and productivity
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Gantt Chart
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.Tools of Shop-Floor Control
• The daily dispatch list• Various status and exception reports– Anticipated delay report– Scrap report– Rework report– Performance summary reports– Shortage list
• An input/output control report
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Some Basic
Tools of Shop-Floor
Control
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.Shop Capacity Control Load Flow
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Principles of Work Center Scheduling
• There is a direct equivalence between work flow and cash flow.
• The effectiveness of any job shop should be measured by speed of flow through the shop.
• Schedule jobs as a string, with process steps back-to-back.
• A job once started should not be interrupted.
• Speed of flow is most efficiently achieved by focusing on bottleneck work centers and jobs.
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.Principles of Job Shop Scheduling (continued)
• Reschedule every day.
• Obtain feedback each day on jobs that are not completed at each work center.
• Match work center input information to what the worker can actually do.
• When improving output, look for incompatibility between engineering design and process execution.
• Certainty of standards, routings, and so forth is not possible, but always work toward achieving it.
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.Personnel Scheduling in Services
• Scheduling consecutive days off
• Scheduling daily work times
• Scheduling hourly work times
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.Software for Employee Scheduling
• ScheduleSource Inc. of Broomfield, Colorado, offers an integrated suite of tools for workforce management named TeamWork.
• At the heart of TeamWork is a customizable and automated employee scheduling system. The benefits of TeamWork software include features such as– Web based
– Optimized schedules
– Zero conflict scheduling
– Time and attendance recordkeeping
– E-mail notifications
– Audit trail
– Advanced reporting
– Accessibility from anywhere any time
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Steps for the Software
• Step 1: Define labor requirements.
• Step 2: Establish employee availability.
• Step 3: Assign employees to particular skill sets and rank an employee’s skill set level from 1 to 10 (1 being novice, 5 being average, and 10 being superlative).
• Step 4: The TeamWork software automatically builds a schedule.
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TSA and ScheduleSource
Software• ScheduleSource customers include– The Transportation Security Administration
(TSA) has successfully implemented ScheduleSource Software to generate schedules for more than 44,000 federal airport security personnel at 429 airports.
– More than 30,000,000 individual shifts were scheduled in the airport security deployment.
