Production Planning Control Operations Scheduling Professor JIANG Zhibin Department of Industrial Engineering Logistics Management Shanghai Jiao Tong University
Production Planning & Control Professor JIANG Zhibin Department of Industrial Engineering & Logistics Management Shanghai Jiao Tong University Operations Scheduling
Operations Scheduling Contents 。Introduction Job Shop Scheduling Terminology ·Sequencing Rules Sequencing Theory for a Single Machine .Sequencing Theory for Multiple Machines Assembly Line Balancing Advanced Topics for Operations scheduling 國上浒充鱼大姿
Operations Scheduling Contents • Introduction • Job Shop Scheduling Terminology • Sequencing Rules • Sequencing Theory for a Single Machine • Sequencing Theory for Multiple Machines • Assembly Line Balancing • Advanced Topics for Operations scheduling
Introduction-What is Operations Scheduling Forecast of future demand Implement the production orders generated in MRP under given objectives Aggregate plan Allocate production resources (machine,workers et al.)to production orders (jobs or tasks Master production schedule(MPS) and their due dates)in an Schedule of production quantities by optimized manners; product and time period The results are time allocations of production resources to different Material Requirement Planning(MRP) jobs (job sequences on each Generate production orders and production resources); purchase order All the orders can be completed while all production resources are Operations Scheduling utilized with their loads being To meet quantities and time balanced. requirements for MRP 上济充通大学
Introduction-What is Operations Scheduling ? • Implement the production orders generated in MRP under given objectives ; • Allocate production resources (machine, workers et al.) to production orders (jobs or tasks and their due dates) in an optimized manners; • The results are time allocations of production resources to different jobs (job sequences on each production resources); • All the orders can be completed while all production resources are utilized with their loads being balanced. Forecast of future demand Aggregate plan Master production schedule (MPS) Schedule of production quantities by product and time period Material Requirement Planning (MRP) Generate production orders and purchase order Operations Scheduling To meet quantities and time requirements for MRP
Introduction-Objectives of Job Shop Scheduling Objectives of operations scheduling 1)Meet due date; 2)Minimize WIP inventory; 3)Minimize the average flow time through the systems; 4)Provide for high machine/worker(time)utilization(minimize idle time); 5) Reduce setup cost; 6 Minimize production and worker costs Discussion 1)and 3)aim at providing a high level of costumer service; V 2),4),5)and 6)are to provide a high level of workshop efficiency; Impossible to optimize all above objectives simultaneously; Proper trade off between cost and quality is one of the most challenging strategic issues facing a firm today;
Introduction-Objectives of Job Shop Scheduling • Objectives of operations scheduling 1) Meet due date; 2) Minimize WIP inventory; 3) Minimize the average flow time through the systems; 4) Provide for high machine/worker (time) utilization (minimize idle time); 5) Reduce setup cost; 6) Minimize production and worker costs • Discussion 1) and 3) aim at providing a high level of costumer service; 2), 4), 5) and 6) are to provide a high level of workshop efficiency; Impossible to optimize all above objectives simultaneously; Proper trade off between cost and quality is one of the most challenging strategic issues facing a firm today;
Introduction-Objectives of operations Scheduling Discussion (Cont. Some of these objectives conflicts,e.g. Reduce WIP inventory Worker idle time may increase or machine utilization may decrease; a Reasons:differences in the throughput rate from one part of the system to another may force the faster operations to wait. As an example,if there is no buffer for WIP between 1 and 2,what happens? Buffer Input (work-in-process) Output Fig8-3 A Process Composed of Two Operations in eries骈克鱼大
Introduction-Objectives of operations Scheduling • Discussion (Cont.) Some of these objectives conflicts, e.g. Reduce WIP inventory Worker idle time may increase or machine utilization may decrease; Reasons: differences in the throughput rate from one part of the system to another may force the faster operations to wait. Fig 8-3 A Process Composed of Two Operations in Series As an example, if there is no buffer for WIP between 1 and 2, what happens?
h Introduction-Functions of Scheduling and Control The following functions must be performed in scheduling and controlling a shop floor: Allocating orders,equipment,and personnel to work centers or other specified location-Short term capacity planning; Determining the sequence of orders(i.e.job priorities); Initializing performance of the scheduled work,commonly termed the dispatching of jobs; Shop-floor control,involving Reviewing the status and controlling the progress of orders as they are being worked on; Expediting the late and critical orders; vRevising the schedules in light of changes in order status. ®上济充道大
Introduction-Functions of Scheduling and Control • The following functions must be performed in scheduling and controlling a shop floor: Allocating orders, equipment, and personnel to work centers or other specified location-Short term capacity planning; Determining the sequence of orders (i. e. job priorities); Initializing performance of the scheduled work, commonly termed the dispatching of jobs; Shop-floor control, involving Reviewing the status and controlling the progress of orders as they are being worked on; Expediting the late and critical orders; Revising the schedules in light of changes in order status
Introduction-Elements of the Shop Floor Scheduling Problems The classic approaches to shop floor scheduling focuses on the following six elements: Job arrival patterns:static or dynamic Static:jobs arrive in batch; Dynamic:jobs arrive over time interval according to some statistical distribution. Numbers and variety of machines in the shop floor If there is only one machine or if a group of machines can be treated as one machine,the scheduling problem is much more simplified; As number of variety of machines increase,the more complex the scheduling problems is likely to become. 圈上泽充鱼大姿
Introduction-Elements of the Shop Floor Scheduling Problems • The classic approaches to shop floor scheduling focuses on the following six elements: Job arrival patterns: static or dynamic Static: jobs arrive in batch; Dynamic: jobs arrive over time interval according to some statistical distribution. Numbers and variety of machines in the shop floor If there is only one machine or if a group of machines can be treated as one machine, the scheduling problem is much more simplified; As number of variety of machines increase, the more complex the scheduling problems is likely to become
h Introduction-Elements of the Shop Floor Scheduling Problems (Continued) Ratio of workers to machines Machine limited system:more workers than machine or equal number workers and machines; Labor-limited system:more machines than worker. Flow pattern of jobs:flow shop or job shop Flow shop:all jobs follow the same paths from one machine to the next; Job shop:no similar pattern of movement of jobs from one machine to the next. 圈上浒充鱼大
Introduction-Elements of the Shop Floor Scheduling Problems • (Continued) Ratio of workers to machines Machine limited system: more workers than machine or equal number workers and machines; Labor-limited system: more machines than worker. Flow pattern of jobs: flow shop or job shop Flow shop: all jobs follow the same paths from one machine to the next; Job shop: no similar pattern of movement of jobs from one machine to the next
Introduction-Elements of the Shop Floor Scheduling Problems (Continued) √Job sequencing Sequencing or priority sequencing:the process of determining which job is started first on some machines or work center by priority rule; Priority rule:the rule used for obtaining a job sequencing; Priority rule evaluation criteria To meet corresponding objectives of scheduling; Common standard measures: > Meeting due date of customers or downstream operations; Minimizing flow time(the time a job spends in the shop flow); > Minimizing WIP; > Minimizing idle time of machines and workers (Maximizing utilization). 圈上泽充鱼大姿
Introduction-Elements of the Shop Floor Scheduling Problems • (Continued) Job sequencing Sequencing or priority sequencing: the process of determining which job is started first on some machines or work center by priority rule; Priority rule: the rule used for obtaining a job sequencing; Priority rule evaluation criteria To meet corresponding objectives of scheduling; Common standard measures: Meeting due date of customers or downstream operations; Minimizing flow time (the time a job spends in the shop flow); Minimizing WIP; Minimizing idle time of machines and workers (Maximizing utilization)
Introduction-Elements of the Job Shop Scheduling Problems Flow shop: Each of the n jobs must be processed through the m machines in the same order. Task Each job is processed exactly once on each machine. An assembly line is a classic example of flow shop Every cars go through all the stations one by one in the same sequences; Same tasks are performed on each car in each station; Its operations scheduling is simplified as assembly line balancing; An assembly balancing problem is to determine the number of stations and to allocate tasks to each station. @上浒充道大皇
Introduction-Elements of the Job Shop Scheduling Problems An assembly line is a classic example of flow shop • Every cars go through all the stations one by one in the same sequences; • Same tasks are performed on each car in each station; • Its operations scheduling is simplified as assembly line balancing; • An assembly balancing problem is to determine the number of stations and to allocate tasks to each station. Flow shop: • Each of the n jobs must be processed through the m machines in the same order. • Each job is processed exactly once on each machine
