1. Introduction to Scheduling Chapter 1
Prepared by: Dr. Tsung-Nan Tsai

2. Introduction to Scheduling sch_chap1.ppt
What is Scheduling?
Scheduling deals with the allocation of scarce resources to tasks over time. It is a decision-making process with the goal of optimizing one or more objectives.
Consists of planning and prioritizing activities that need to be performed in an orderly sequence of operation.
Scheduling leads to increased efficiency and capacity utilization, reducing time required to complete jobs and consequently increasing the profitability of an organization.
Resource scheduling, such as machines, labor, and material.
2019/1/16
Introduction to Scheduling sch_chap1.ppt

3. Introduction to Scheduling sch_chap1.ppt
The role of scheduling
The resources and tasks in an organization has many forms, the resources such as:
machines in a workshop, runways at an airport
crews at a construction site, processing units in a computing environment.
The tasks may be:
operations in a production process, take-offs and landing at an airport.
stages in a construction project, executions of computer programs.
2019/1/16
Introduction to Scheduling sch_chap1.ppt

4. Manufacturing system’s information flow
MRP - I
Detailed
scheduling
2019/1/16
Introduction to Scheduling sch_chap1.ppt

5. Service system’s information flow
2019/1/16
Introduction to Scheduling sch_chap1.ppt

6. Introduction to Scheduling sch_chap1.ppt
1.1 Scheduling Examples
Carton manufacturing operations: High mixed products and on time delivery.
Order delay: How to minimize the penalties?
Product similarity: How to produce with same setup? How to plan the production?
Industrial lighting equipment: With current line layout and operators
How to modify the product or new product by using same facility and operators?
How can the assembly lines be modified for production modification or new products.
2019/1/16
Introduction to Scheduling sch_chap1.ppt

7. Introduction to Scheduling sch_chap1.ppt
1.1 Scheduling Examples
A machine shop has only stamping machine: With different dye and a different processing time.
How to generate weekly schedule to minimize the number of late shipments?
How should these schedules be developed?
Electronic assembly: With burn-in (stress screen), reliability test
How to group the PCBs into batch for testing?
How to meet the due date?
2019/1/16
Introduction to Scheduling sch_chap1.ppt

8. 1.2 Scheduling on the shop floor
Scheduling is a timetable for both jobs and machines, and play an important role in shop floor planning.
Stocking the raw material before the work-order release time will add to the carrying cost.
If materials are not available at release time, the jobs could be delayed and added to the operational cost.
Capacity planning is an integral part of scheduling procedures. It refers to how much of a machine’s production time should be allocated to each job.
To calculate the processing time for a job, considering setup time, unit processing time, machine speed, quality factors, and number of units needed.
2019/1/16
Introduction to Scheduling sch_chap1.ppt

9. Introduction to Scheduling sch_chap1.ppt
Scheduling Algorithm
Data files for shop floor factors
Workers’ shift schedules
Machines and their characteristics
Maintenance data
Progress on processing jobs presently
Current status of the machines (busy, idle, broken, need repair, under repair)
Customer order data
Priority setting (based on the production status daily)
“Hot”, “very hot” …
Information from MRP system
2019/1/16
Introduction to Scheduling sch_chap1.ppt

10. Introduction to Scheduling sch_chap1.ppt
Methodology
Practically, schedules are generated using scheduling algorithms or knowledge-based rules (“If-Then”).
Scheduling algorithms tend to optimize a measuring criterion such as the minimizing deviations from due dates, tardiness penalty, or the maximum delay.
The rule-, or knowledge-based tries to find a feasible solution under the operating environment. “If machine A and operator X are available, Then load job Z”
2019/1/16
Introduction to Scheduling sch_chap1.ppt

11. 1.2 Scheduling on the shop floor
What is responsibility of the department production control?
What is responsibility of the department of material control?
What is the responsibility of process engineer?
What is the responsibility of the production?
What is responsibility of the department of quality control ?
What is responsibility of the department of purchasing?
2019/1/16
Introduction to Scheduling sch_chap1.ppt

12. Introduction to Scheduling sch_chap1.ppt
Gantt chart
2019/1/16
Introduction to Scheduling sch_chap1.ppt

13. 1.3 Production planning terminology
Single machine
Server: only one machine (server) available
Work: arriving jobs (work)
Constraints: each job has a processing time and a due date and may have other characteristics (priority).
Penalty function: deviating from the due date.
Objective: to sequence jobs on the machine with min penalty.
2019/1/16
Introduction to Scheduling sch_chap1.ppt

14. 1.3 Production planning terminology
Flow Shop
Server: multiple machines in an identical sequence
Work: arriving jobs (work)
Constraints: processing time of each job on each machine may be different.
Objective: to minimize the time required for completion of all jobs, called the makespan.
2019/1/16
Introduction to Scheduling sch_chap1.ppt

15. 1.3 Production planning terminology
Parallel machines
Server: a number of identical machines available
Work: jobs can be processed any one of the available machines.
Constraints: Jobs may have dependency. Next job in the sequence may not start until the previous job has been completely processed.
Objective: to minimize the makespan.
2019/1/16
Introduction to Scheduling sch_chap1.ppt

16. 1.3 Production planning terminology
Job Shop
Server: there are different machines available in the shop
Work: a job may require some or all of these machines in specific sequence.
Constraints: a job can not use the same machine more than once.
Objective: may be to minimize the makespan or tardiness penalty.
2019/1/16
Introduction to Scheduling sch_chap1.ppt

17. 1.3 Production planning terminology
Open Shop
Server: there are different machines available in the shop
Work: is similar to a job shop except that a job processed on the machine in any sequence the job needs.
Constraints: there is no operationally dependent sequence that a job must follow.
Objective: to minimize the makespan.
2019/1/16
Introduction to Scheduling sch_chap1.ppt

18. 1.3 Production planning terminology
Dependent Shop
Server: there are different machines available in the shop
Work: a job shop environment in which the processing order of one or more jobs depends on the processing of other jobs.
Objective: to minimize the makespan.
2019/1/16
Introduction to Scheduling sch_chap1.ppt

19. 1.3 Production planning terminology
Batch Processing
Server: machines with limited capacity
Work: jobs are processed in batches, each batch requiring certain processing time, and there may be a capacity limitation on how many jobs can be processed at one time.
(such as a baking oven)
Objective: increasing the quantity of a batch and reduce the processing time.
2019/1/16
Introduction to Scheduling sch_chap1.ppt

20. 1.3 Production planning terminology
Sequence-dependent setup times
Server: referred to be batch processing
Work: each job may belong to a type. If jobs of the same type are processed one after the other, then no additional setup is required. If a different type of job is processed, there is a setup cost.
Constraints: each job has a due date
Objective: to minimize the total tardiness penalty.
2019/1/16
Introduction to Scheduling sch_chap1.ppt

21. 1.3 Production planning terminology
Assembly line
Server: a certain sequence of operations
Work: each job
Objective: to define workstations and assign tasks to these stations to achieve a certain production level and efficiency.
Mixed-mode assembly line
Server: an assembly line
Work: similar product (not identical product)
Constraints: each product is with different task requirement and task times.
2019/1/16
Introduction to Scheduling sch_chap1.ppt

22. Deterministic vs. Stochastic problems
Deterministic problem: All scheduling data are known.
Stochastic problem: The data are probabilistic in nature (randomness or fuzziness).
Most scheduling problems are either deterministic or can be closely approximately by the deterministic models.
The most common way to convert a stochastic problem into a deterministic problem is work with the average values.
2019/1/16
Introduction to Scheduling sch_chap1.ppt

23. 1.4 Scheduling Techniques
Software: Lindo, Simple++, Arena
Technique: Group technique, Gantt Chart, CPM
Heuristic approach
Artificial Intelligence: Fuzzy logic, Genetic Algorithm, Neural network, Artificial Immune System, …
2019/1/16
Introduction to Scheduling sch_chap1.ppt