15-1 Scheduling

JIT andLean Operations

15-2 Scheduling

JIT/Lean ProductionJIT/Lean Production

Just-in-time (JIT): A highly coordinated processing system in which goods move through the system, and services are performed, just as they are needed,

JIT lean production

JIT pull (demand) system

JIT operates with very little “fat”

15-3 Scheduling

Goal of JITGoal of JIT

The ultimate goal of JIT is a balanced system.

Achieves a smooth, rapid flow of materials through the system

15-4 SchedulingSummary JIT Goals and Building Summary JIT Goals and Building BlocksBlocks

Figure 14.1

Product Design

ProcessDesign

PersonnelElements

Manufactur-ing Planning

Eliminate disruptions

Make the system flexible Eliminate waste

Abalancedrapid flow

UltimateGoal

SupportingGoals

BuildingBlocks

15-5 Scheduling

JIT Building BlocksJIT Building Blocks

Product design Process design Personnel/organizational

elements Manufacturing

planning and control

15-6 Scheduling

Product DesignProduct Design

Standard parts

Modular design

Highly capable production systems

Concurrentengineering

15-7 Scheduling

Process DesignProcess Design

Small lot sizes Setup time reduction Manufacturing cells Limited work in process Quality improvement Production flexibility Little inventory storage

15-8 Scheduling

Benefits of Small Lot SizesBenefits of Small Lot Sizes

Reduces inventory

Less storage space

Less rework

Problems are more apparent

Increases product flexibility

Easier to balance operations

15-9 Scheduling

Personnel/Organizational ElementsPersonnel/Organizational Elements

Workers as assets

Cross-trained workers

Continuous improvement

Cost accounting

Leadership/project management

15-10 Scheduling

Manufacturing Planning and ControlManufacturing Planning and Control

Level loading

Pull systems

Visual systems

Close vendor relationships

Reduced transaction processing

Preventive maintenance

15-11 Scheduling

Pull/Push SystemsPull/Push Systems

Pull system: System for moving work where a workstation pulls output from the preceding station as needed. (e.g. Kanban)

Push system: System for moving work where output is pushed to the next station as it is completed

15-12 Scheduling

Traditional Supplier NetworkTraditional Supplier Network

BuyerBuyer

SupplierSupplierSupplierSupplier SupplierSupplier SupplierSupplier

SupplierSupplier

SupplierSupplierSupplierSupplier

Figure 14.4a

15-13 Scheduling

Tiered Supplier NetworkTiered Supplier NetworkFigure 14.4b

SupplierSupplier

SupplierSupplier

SupplierSupplier

SupplierSupplierSupplierSupplier SupplierSupplier

BuyerBuyer

SupplierSupplierFirst Tier SupplierFirst Tier Supplier

Second Tier SupplierSecond Tier Supplier

Third Tier SupplierThird Tier Supplier

15-14 Scheduling

Comparison of JIT and TraditionalComparison of JIT and Traditional

Factor Traditional JIT

Inventory Much to offset forecast errors, late deliveries

Minimal necessary to operate

Deliveries Few, large Many, small

Lot sizes Large Small

Setup; runs Few, long runs Many, short runs

Vendors Long-term relationships are unusual

Partners

Workers Necessary to do the work

Assets

Table 14.3

15-15 Scheduling

Transitioning to a JIT SystemTransitioning to a JIT System

Get top management commitment

Decide which parts need most effort

Obtain support of workers

Start by trying to reduce setup times

Gradually convert operations

Convert suppliers to JIT

Prepare for obstacles

15-16 Scheduling

Obstacles to ConversionObstacles to Conversion

Management may not be committed

Workers/management may not be cooperative

Suppliers may resist Why?

15-17 Scheduling

JIT in ServicesJIT in Services

The basic goal of the demand flow technology in the service organization is to provide optimum response to the customer with the highest quality service and lowest possible cost. Eliminate disruptions Make system flexible Reduce setup and lead times Eliminate waste Minimize WIP Simplify the process

15-18 Scheduling

Benefits of JIT SystemsBenefits of JIT Systems

Reduced inventory levels

High quality

Flexibility

Reduced lead times

Increased productivity

15-19 Scheduling

Benefits of JIT Systems (cont’d)Benefits of JIT Systems (cont’d)

Increased equipment utilization

Reduced scrap and rework

Reduced space requirements

Pressure for good vendor relationships

Reduced need for indirect labor

15-20 Scheduling

CHAPTER15

Scheduling

15-21 Scheduling

Scheduling: Establishing the timing of the use of equipment, facilities and human activities in an organization

Effective scheduling can yield

Cost savings

Increases in productivity

Scheduling Scheduling

15-22 Scheduling

High-Volume SystemsHigh-Volume Systems

Flow system: High-volume system with Standardized equipment and activities

Flow-shop scheduling: Scheduling for high-volume flow system

Work Center #1 Work Center #2 Output

15-23 Scheduling

Build A

A Done

Build B

B Done

Build C

C Done

Build D

Ship

JAN FEB MAR APR MAY JUN

On time!

Scheduling Manufacturing OperationsScheduling Manufacturing Operations

High-volume

Intermediate-volume

Low-volume

Service operations

15-24 Scheduling

High-Volume Success FactorsHigh-Volume Success Factors

Process and product design

Preventive maintenance

Rapid repair when breakdown occurs

Optimal product mixes

Minimization of quality problems

Reliability and timing of supplies

15-25 Scheduling

Intermediate-Volume SystemsIntermediate-Volume Systems

Outputs are between standardized high-volume systems and made-to-order job shops

Run size, timing, and sequence of jobs

Economic run size:

QDS

H

p

p u0

2

15-26 Scheduling

Scheduling Low-Volume SystemsScheduling Low-Volume Systems

Loading - assignment of jobs to process centers

Sequencing - determining the order in which jobs will be processed

Job-shop scheduling Scheduling for low-volume

systems with many variations in requirements

15-27 Scheduling

Gantt Load ChartGantt Load Chart

Gantt chart - used as a visual aid for loading and scheduling

WorkCenter

Mon. Tues. Wed. Thurs. Fri.

1 Job 3 Job 42 Job 3 Job 73 Job 1 Job 6 Job 74 Job 10

Figure 15.2

15-28 Scheduling

Infinite loading

Finite loading

Vertical loading

Horizontal loading

Forward scheduling

Backward scheduling

Schedule chart

LoadingLoading

15-29 Scheduling

SequencingSequencing

Sequencing: Determine the order in which jobs at a work center will be processed.

Workstation: An area where one person works, usually with special equipment, on a specialized job.

15-30 Scheduling

SequencingSequencing

Priority rules: Simple heuristics used to select the order in which jobs will be processed.

Job time: Time needed for setup and processing of a job.

Everything is#1 Priority

15-31 Scheduling

Priority RulesPriority Rules

FCFS - first come, first served

SPT - shortest processing time

EDD - earliest due date

CR - critical ratio

S/O - slack per operation

Rush - emergencyTop Priority

Table 15.2

15-32 Scheduling

3.249.6722.17CR

2.686.3318.33EDD

2.636.6718.00SPT

2.939.0020.00FCFS

AverageNumber ofJobs at theWork Center

AverageTardiness(days)

AverageFlow Time(days)Rule

Example 2Example 2Table 15.4

15-33 Scheduling

Two Work Center SequencingTwo Work Center Sequencing

Johnson’s Rule: technique for minimizing completion time for a group of jobs to be processed on two machines or at two work centers.

Minimizes total idle time

Several conditions must be satisfied

15-34 Scheduling

Johnson’s Rule ConditionsJohnson’s Rule Conditions

Job time must be known and constant

Job times must be independent of sequence

Jobs must follow same two-step sequence

Job priorities cannot be used

All units must be completed at the first work center before moving to second

15-35 Scheduling

Johnson’s Rule Optimum SequenceJohnson’s Rule Optimum Sequence

1. List the jobs and their times at each work center

2. Select the job with the shortest time

3. Eliminate the job from further consideration

4. Repeat steps 2 and 3 until all jobs have been scheduled

15-36 Scheduling

Scheduling DifficultiesScheduling Difficulties

Variability in Setup times Processing times Interruptions Changes in the set of jobs

No method for identifying optimal schedule Scheduling is not an exact science Ongoing task for a manager

15-37 Scheduling

Minimizing Scheduling DifficultiesMinimizing Scheduling Difficulties

Set realistic due dates

Focus on bottleneck operations

Consider lot splitting of large jobs

15-38 Scheduling

Scheduling Service Operations Scheduling Service Operations

Appointment systems Controls customer arrivals for service

Reservation systems Estimates demand for service

Scheduling the workforce Manages capacity for service

Scheduling multiple resources Coordinates use of more than one

resource

15-39 Scheduling

Cyclical SchedulingCyclical Scheduling

Hospitals, police/fire departments, restaurants, supermarkets

Rotating schedules Set a scheduling horizon Identify the work pattern Develop a basic employee schedule Assign employees to the schedule

15-40 Scheduling

Service Operation ProblemsService Operation Problems

Cannot store or inventory services Customer service requests are random Scheduling service involves

Customers Workforce Equipment

15-41 Scheduling

Service SchedulingService Scheduling

SSU1Overview—United Airlines

15-42 Scheduling

Service SchedulingService Scheduling

SSU2United Airlines Flight Schedule

15-43 Scheduling

ScheduleSchedule

PS8Painting Example (Washburn Guitar)