Characteristics of a “job” • Constituent operations • Due date • Time of arrival in shop • Starting time • Completion time • Flow time • Lateness
Characteristics of a schedule Two basic types of scheduling • Work-force scheduling • Operations scheduling
Operations Scheduling short-term plans designed to implement the master production schedule • job shop • flow shop
Timing of job/operations scheduled (Gantt chart) • Job or activity progress chart • Machine chart For n jobs, each requiring m machines there are (n!)m possible schedules
Measures • Average flow time of jobs • Average lateness of jobs • Makespan • Idle time • Past Due • WIP • Utilization Which of these would Goldratt have said was best?
Scheduling heuristics • FCFS – first come, first served • SPT – shortest processing time • EDD – earliest due date
Information Needed for Scheduling • Question: What information do you feel is needed to accurately schedule an operation?
Scheduling Class Activity At the beginning: 400 birch in inventory 100 cherry past due Equipment is set up for cherry
Scheduling Game Process. • I will give you demand for week • Decide on how much of each type to process – don’t forget open orders & birch forecast! • Record on decision log • Make a feasible schedule (don’t forget setups) • Turn in decision for week to me • When complete wait for actual birch demand for week • Calculate profit/loss – give total to me • Get demand for new week