Introduction-Job Shop Turnning Center Drilling Center Grinding Center Milling Center ∞ A job shop is organized by machines which are grouped according to their functions. @上浒充道大漫
Introduction-Job Shop Turnning Center Drilling Center Grinding Center Milling Center A job shop is organized by machines which are grouped according to their functions
h Introduction-Job Shop Work Center 2 Work Center 1 D D JobA Work Center 4 Work Center 3 Job B Not all jobs are assumed to require exactly the same number of operations,and some jobs may require multiple operations on a single machine (Reentrant system,Job B twice in work center 3 ) Each job may have a different required sequencing of operations. No all-purpose solution algorithms for solving general job shop problems Operations scheduling of shop floor usually means job shop scheduling; 圆上泽充通大
Introduction-Job Shop Work Center 1 Work Center 2 Work Center 4 Work Center 3 • Not all jobs are assumed to require exactly the same number of operations, and some jobs may require multiple operations on a single machine (Reentrant system, Job B twice in work center 3 ). • Each job may have a different required sequencing of operations. • No all-purpose solution algorithms for solving general job shop problems ; • Operations scheduling of shop floor usually means job shop scheduling; Job A Job B
Job Shop Scheduling Terminology 1.Parallel processing versus sequential processing Sequencing Processing:the m machines are distinguishable,and different operations are performed by different machines. Parallel processing:The machines are identical,and any job can be processed on any machine. Job M2 Job A M M2 Job M3 Job B M M, M,M2,M3,and Ma are different; Job a has 2 operations which should be processed on different Machines:M and M2; M,M,M3,and M are identical; Job B has 3 operations which should be Jobs A and B can be processed on processed on different Machines:M3,M2 any one of the 4 machines and M4; 上泽充通大崇
Job Shop Scheduling Terminology 1. Parallel processing versus sequential processing • Sequencing Processing: the m machines are distinguishable, and different operations are performed by different machines. • Parallel processing: The machines are identical, and any job can be processed on any machine. M1 M2 M3 M4 Job A Job B • M1 , M2 , M3 , and M4 are different; • Job A has 2 operations which should be processed on different Machines: M1 and M2 ; • Job B has 3 operations which should be processed on different Machines: M3 , M2 and M4 ; M1 M2 M3 M4 Job A Job B •M1 , M2 , M3 , and M4 are identical; •Jobs A and B can be processed on any one of the 4 machines
Job Shop Scheduling Terminology 2 Flow time The flow time of job i is the time that elapses from the initiation of that job on the first machine to the completion of job i. The mean flow time,which is a common measure of system performance,is the arithmetic average of the flow times for all n jobs Machine Mean Flow Time=(F+F2+F3)/3 S M Job1 Job2 Job 3 M2 Job1 Job2 Job3 F:FT of Job 1 Time F2:FT of Job 2 F3:FT of Job3 圈上泽充道大姿
Job Shop Scheduling Terminology 2 Flow time • The flow time of job i is the time that elapses from the initiation of that job on the first machine to the completion of job i. • The mean flow time, which is a common measure of system performance, is the arithmetic average of the flow times for all n jobs Job 1 Job 2 Job 1 Job 3 Job 2 Job 3 Machine s M1 M2 F1 Time : FT of Job 1 F2 : FT of Job 2 F3 : FT of Job 3 Mean Flow Time=(F1+F2+F3 )/3
h Job Shop Scheduling Terminology 3.Make-span The make-span is the time required to complete a group of jobs(all n jobs). Minimizing the make-span is a common objective in multiple-machine sequencing problems. Machines M Job1 Job 2 Job 3 M2 Job 1 Job2 Job 3 F:FT of Job Time F2:FT of Job 2 F3: FT of Job Make-span of the 3 圈上泽充道大姿
Job Shop Scheduling Terminology 3. Make-span • The make-span is the time required to complete a group of jobs (all n jobs). • Minimizing the make-span is a common objective in multiple-machine sequencing problems. Job 1 Job 2 Job 1 Job 3 Job 2 Job 3 Machines M1 M2 F1 Time : FT of Job 1 F2 : FT of Job 2 F3 : FT of Job 3 Make-span of the 3 jobs