15-1
Scheduling
JIT and
Lean Operations
15-2
Scheduling
JIT/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 JIT
The ultimate goal of JIT is a balanced
system.
Achieves a smooth, rapid flow of materials
through the system
15-4
Scheduling
Summary JIT Goals and Building Blocks
Figure 14.1
Ultimate
A
Goal balanced
rapid flow
Supporting
Goals
Eliminate disruptions
Make the system flexible
Product
Design
Process
Design
Eliminate waste
Personnel
Elements
Manufacturing Planning
Building
Blocks
15-5
Scheduling
JIT Building Blocks

Product design

Process design

Personnel/organizational
elements

Manufacturing
planning and control
15-6
Scheduling
Product Design

Standard parts

Modular design

Highly capable production systems

Concurrent
engineering
15-7
Scheduling

Process 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 Sizes
Reduces inventory
Less rework
Less storage space
Problems are more apparent
Increases product flexibility
Easier to balance operations
15-9
Scheduling
Personnel/Organizational Elements

Workers as assets

Cross-trained workers

Continuous
improvement

Cost accounting

Leadership/project
management
15-10 Scheduling
Manufacturing Planning and Control

Level loading

Pull systems

Visual systems

Close vendor relationships

Reduced transaction
processing

Preventive maintenance
15-11 Scheduling
Pull/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 Network
Figure 14.4a
Buyer
Supplier
Supplier
Supplier
Supplier
Supplier
Supplier
Supplier
15-13 Scheduling
Tiered Supplier Network
Figure 14.4b
Buyer
First Tier Supplier
Second Tier Supplier
Third Tier Supplier
Supplier
Supplier
Supplier
Supplier
Supplier
Supplier
Supplier
15-14 Scheduling
Comparison of JIT and Traditional
Table 14.3
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
15-15 Scheduling
Transitioning 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 Conversion

Management may not be committed

Workers/management may not be
cooperative

Suppliers may
resist

Why?
15-17 Scheduling
JIT 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 Systems

Reduced inventory levels

High quality

Flexibility

Reduced lead times

Increased productivity
15-19 Scheduling
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
CHAPTER
15
Scheduling
15-21 Scheduling
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
15-22 Scheduling

High-Volume Systems
Flow system: High-volume system with
Standardized equipment and activities

Flow-shop scheduling: Scheduling for highvolume flow system
Work Center #1
Work Center #2
Output
15-23 Scheduling
Scheduling Manufacturing Operations
High-volume
Intermediatevolume
JAN
FEB
MAR
APR
MAY
JUN
Build A
A Done
Build B
Low-volume
B Done
Service
operations
C Done
Build C
Build D
Ship
On time!
15-24 Scheduling
High-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 Systems

Outputs are between standardized highvolume systems and made-to-order job shops


Run size, timing, and sequence of jobs
Economic run size:
Q0 
2DS
p
H p u
15-26 Scheduling
Scheduling 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 Chart
Figure 15.2

Gantt chart - used as a visual aid for loading
and scheduling
Work Mon. Tues. Wed. Thurs. Fri.
Center
1
Job 3
Job 4
2
Job 3 Job 7
3
Job 1
Job 6
Job 7
4
Job 10
15-28 Scheduling
Loading

Infinite loading

Finite loading

Vertical loading

Horizontal loading

Forward scheduling

Backward scheduling

Schedule chart
15-29 Scheduling
Sequencing

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

Sequencing
Priority rules: Simple heuristics
used to select the order in
which jobs will be processed.
Everything is
#1 Priority

Job time: Time needed for
setup and processing of a job.
15-31 Scheduling
Priority Rules
Table 15.2

FCFS - first come, first served

SPT - shortest processing time

EDD - earliest due date

CR - critical ratio

S/O - slack per operation

Rush - emergency
Top Priority
15-32 Scheduling
Example 2
Table 15.4
Rule
Average
Flow Time
(days)
Average
Tardiness
(days)
Average
Number of
Jobs at the
Work Center
FCFS
20.00
9.00
2.93
SPT
18.00
6.67
2.63
EDD
18.33
6.33
2.68
CR
22.17
9.67
3.24
15-33 Scheduling
Two 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 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 Sequence
1.
2.
3.
4.
List the jobs and their times at each work
center
Select the job with the shortest time
Eliminate the job from further consideration
Repeat steps 2 and 3 until all jobs have been
scheduled
15-36 Scheduling

Scheduling 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 Difficulties

Set realistic due dates

Focus on bottleneck operations

Consider lot splitting of large jobs
15-38 Scheduling
Scheduling Service Operations

Appointment systems


Reservation systems


Estimates demand for service
Scheduling the workforce


Controls customer arrivals for service
Manages capacity for service
Scheduling multiple resources

Coordinates use of more than one
resource
15-39 Scheduling
Cyclical 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 Problems

Cannot store or inventory services
 Customer service requests are random
 Scheduling service involves

Customers
 Workforce
 Equipment
15-41 Scheduling
Service Scheduling
SSU1
Overview—United Airlines
15-42 Scheduling
Service Scheduling
SSU2
United Airlines Flight Schedule
15-43 Scheduling
Schedule
PS8
Painting Example (Washburn Guitar)