Introduction to Scheduling Chapter 1 Prepared by Dr

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

What is Scheduling? n n 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. 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 2

The role of scheduling n The resources and tasks in an organization has many forms, the resources such as: q q n machines in a workshop, runways at an airport crews at a construction site, processing units in a computing environment. The tasks may be: q q operations in a production process, take-offs and landing at an airport. stages in a construction project, executions of computer programs. 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 3

Manufacturing system’s information flow MRP - I Detailed scheduling 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 4

Service system’s information flow 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 5

1. 1 Scheduling Examples n Carton manufacturing operations: High mixed products and on time delivery. q q n 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 q q 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. 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 6

1. 1 Scheduling Examples n A machine shop has only stamping machine: With different dye and a different processing time. q q n 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 q How to group the PCBs into batch for testing? q How to meet the due date? 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 7

1. 2 Scheduling on the shop floor n n n 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. 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 8

Scheduling Algorithm n Data files for shop floor factors q q q n Priority setting (based on the production status daily) q n 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 “Hot”, “very hot” … Information from MRP system 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 9

Methodology n n n 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” 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 10

1. 2 Scheduling on the shop floor n n n 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? 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 11

Gantt chart 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 12

1. 3 Production planning terminology n Single machine q Server: only one machine (server) available q Work: arriving jobs (work) q q q 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. 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 13

1. 3 Production planning terminology n Flow Shop q q 9/30/2020 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_chap 1. ppt 14

1. 3 Production planning terminology n Parallel machines q q 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. 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 15

1. 3 Production planning terminology n Job Shop q q 9/30/2020 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_chap 1. ppt 16

1. 3 Production planning terminology n Open Shop q q 9/30/2020 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_chap 1. ppt 17

1. 3 Production planning terminology n Dependent Shop q q q 9/30/2020 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_chap 1. ppt 18

1. 3 Production planning terminology n Batch Processing Server: machines with limited capacity q 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. q (such as a baking oven) q 9/30/2020 Objective: increasing the quantity of a batch and reduce the processing time. Introduction to Scheduling sch_chap 1. ppt 19

1. 3 Production planning terminology n Sequence-dependent setup times q q 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. q Constraints: each job has a due date q Objective: to minimize the total tardiness penalty. 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 20

1. 3 Production planning terminology n Assembly line q Server: a certain sequence of operations q Work: each job q n Objective: to define workstations and assign tasks to these stations to achieve a certain production level and efficiency. Mixed-mode assembly line q Server: an assembly line q Work: similar product (not identical product) q 9/30/2020 Constraints: each product is with different task requirement and task times. Introduction to Scheduling sch_chap 1. ppt 21

Deterministic vs. Stochastic problems n n 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. 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 22

1. 4 Scheduling Techniques n n Software: Lindo, Simple++, Arena Technique: Group technique, Gantt Chart, CPM Heuristic approach Artificial Intelligence: Fuzzy logic, Genetic Algorithm, Neural network, Artificial Immune System, … 9/30/2020 Introduction to Scheduling sch_chap 1. ppt 23