Introduction to Scheduling Chapter 1

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

2. 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. Introduction to Scheduling sch_chap1.ppt

3. 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. Introduction to Scheduling sch_chap1.ppt

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

5. Service system’s information flow Introduction to Scheduling sch_chap1.ppt

6. 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. Introduction to Scheduling sch_chap1.ppt

7. 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? 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. Introduction to Scheduling sch_chap1.ppt

9. 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 Introduction to Scheduling sch_chap1.ppt

10. 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” 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? Introduction to Scheduling sch_chap1.ppt

12. Gantt chart 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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, … Introduction to Scheduling sch_chap1.ppt