pert 08 penjadwalan jangka pendek (1) pentingnya penjadwalan
TRANSCRIPT
PERT 08 Penjadwalan Jangka Pendek (1)
� Pentingnya Penjadwalan jangka pendek
� Forward & Backward Scheduling
� Input Output Control
� Gantt Charts
Strategic Implications of Short-TermScheduling
� By scheduling effectively, companies use
assets more effectively and create greater
capacity per dollar invested, which, in turn,
lowers cost
� This added capacity and related flexibility
provides faster delivery and therefore better
customer service
� Good scheduling is a competitive advantage
which contributes to dependable delivery
�Deals with timing of operations
� Short run focus: Hourly, daily, weekly
�Types
TodayToday Due Date
BB EE
Forward SchedulingForward Scheduling
TodayToday Due Date
BB EE
Backward SchedulingBackward Scheduling
Short-Term Scheduling
� Hospital– Outpatient treatments
– Operating rooms
� University– Instructors
– Classrooms
� Factory– Production
– Purchases
© 1984-1994 T/Maker Co.
Short-Term Scheduling Examples
Organization Managers Must ScheduleOperating room use
Patient admission
Nursing, security, maintenance staffs
Outpatient treatments
Classrooms and audiovisual equipment
Student and instructor schedules
Graduate and undergraduate courses
Production of goods
Purchase of materials
Workers
Scheduling Decisions
� Mount Sinai Hospital
� Indiana University
� Lockheed-MartinFactory
Organization Managers Must Schedule
Chefs, waiters,bartenders
Delivery of fresh foods
Entertainers
Opening of dining areas
Maintenance of aircraftDeparture timetables
Flight crews, catering, gate, and ticketing personnel
Scheduling Decisions
� Hard Rock Cafe
� Delta Airlines
Capacity Planning, Aggregate Scheduling, Master
Schedule, and Short-Term Scheduling
Capacity Planning
1. Facility size
2. Equipment procurement
Aggregate Scheduling
1. Facility utilization
2. Personnel needs
3. Subcontracting
Master Schedule
1. MRP
2. Disaggregation of master plan
Long-term
Intermediate-term
Short-term
Intermediate-term
Short-term Scheduling
1. Work center loading
2. Job sequencing
Forward and Backward Scheduling
� Forward scheduling: begins the schedule as soon as the
requirements are known
– jobs performed to customer order
– schedule can be accomplished even if due date is
missed
– often causes buildup of WIP
� Backward scheduling: begins with the due date of the
final operation; schedules jobs in reverse order
– used in many manufacturing environments, catering,
scheduling surgery
The Goals of Short-Term Scheduling
� Minimize completion time
� Maximize utilization (make effective
use of personnel and equipment)
� Minimize WIP inventory (keep
inventory levels low)
� Minimize customer wait time
�Qualitative factors– Number and variety of jobs
– Complexity of jobs
– Nature of operations
�Quantitative criteria– Average completion time
– Utilization (% of time facility is used)
– WIP inventory (average # jobs in system)
– Customer waiting time (average lateness)
Choosing a Scheduling Method
Level Use
Methods
Repetitive-
Focused
Product-
Focused
Process-
Focused
Variety of
Methods
Scheduling Methods Differ by Process
� High variety, low volume systems
� Products made to order
� Products need different materials and
processing
� Complex production planning and control
� Production planning aspects
– Shop loading
– Job sequencing
Process-Focused Work Centers
Requirements for Scheduling Process-Focused Work Centers
� Schedule incoming orders without violating capacity
constraints of individual work centers
� Check availability of tools and materials before releasing
an order to a department
� Establish due dates for each job and check progress against
need dates and order lead times
� Check work-in-progress as jobs move through the shop
� Provide feedback on plant and production activities
� Provide work-efficiency statistics and monitor operator
times for payroll and labor distribution analyses
Types of Planning Files
� Item master file - contains information
about each component the firm
produces or purchases
� Routing file - indicates each
component’s flow through the shop
� Work-center master file - contains
information about the work center such
as capacity and efficiency
� Assigning jobs to work centers
� Considerations
– Job priority (e.g., due date)
– Capacity
• Work center hours available
• Hours needed for job
� Approaches
– Gantt charts (load & scheduling) - capacity
– Assignment method - job to specific work center
Loading Jobs in Work Centers
-+5-10-200Cumulative
Change in Backlog
-200-150-100-50Cumulative
Deviation
270270270270Actual Output
320320320320Planned Output
-35-40-40-10Cumulative
Deviation
280285280250270Actual input
280280280280280Planned input
7/117/46/276/206/136/6Week Ending
Input-Output Control
Explanation: 270 input, 270
output, implies 0 change
Explanation: 250 input,
270 output implies –20
change (20 standard
hours less in the work
center)
Order Release Begins Shop Loading
No
Release
Order
Hold
Release
Priority & Capacity
OK?
Gross Requirements
Scheduled Receipts
Available
Net Requirements
Planned Order Receipt
Planned Order Release
Yes
1 2
100
100
3
Options for Managing Facility Work Flow
� Correcting performance
� Increasing capacity
� Increasing or reducing input to the work
center by:
– routing work to or from other work centers
– increasing or decreasing subcontracting
– producing less (or more)
� Shows relative workload in facility
� Disadvantages
– Does not account for unexpected events
– Must be updated regularly
Work Center M T W Th F
Metal Works Job 349 Job 350
Mechanical Job D Job G
Electronics Job B Job H
Painting Job C Job E Job I
Gantt Load Chart
Gantt Load Chart for Week of March 6
� Shows relative workload in facility
� Disadvantages– Does not account for unexpected events– Must be updated regularly
Job 349Job 408Job 295Painting
Job 349Job 408Electronics
Job 406Job 349Mechanical
Job 350Job 349Metalworks
FridayThursdayWednesdayTuesdayMondayDay
Work
Center
Processing UnscheduledCenter not available (for
example, maintenance time,
repairs, shortages)
Gantt Scheduling ChartStart of an activity
Scheduled activity time allowed
Point in time when chart is reviewed
S T W T F S
DayJob
Job A
Job B
Job C
Maintenance
Now
End of an activity
Actual work progress
Non-production time
Day
1
Day
2
Day
3
Day
4
Day
5
Day
6
Day
7