spørsmålet  |
svaret |
Types of short-term scheduling begynn å lære
|
|
Forward scheduling and backward scheduling
|
|
|
|
begynn å lære
|
|
begins the schedule as soon as the requirements are known; often builds up WIP; jobs performed to customer order, schedule can be accomplished even if due date is missed
|
|
|
|
begynn å lære
|
|
begins with the due date of the final operation, schedules jobs in reverse order, used in many manufacturing environments; ex. catering
|
|
|
Goals of short-term scheduling begynn å lære
|
|
minimize completion time, maximise utilisation, minimise WIP inventory, minimise customer wait time
|
|
|
process-focused work centres begynn å lære
|
|
high variety, low volume, mate-to-order, different materials and processing for each product, complex production planning and control, production scheduling aspects
|
|
|
Loading Jobs in Work Centres begynn å lære
|
|
assigning jobs to work centres; approaches: input-output control, Gantt charts, assignment method
|
|
|
|
begynn å lære
|
|
CONWIP - constant WIP; for given average output rate, try to keep L low and constant then W will be short and constant; Little's formula
|
|
|
|
begynn å lære
|
|
shows relative workload in facility, negatives: does not account for unexpected events, must be updated regularly
|
|
|
|
begynn å lære
|
|
occurs in many environments: resources-jobs, planes-gates, course-rooms); type of binary linear programming model
|
|
|
Priority rules for Dispatching Jobs (sequencing) begynn å lære
|
|
|
|
|
|
begynn å lære
|
|
First come first serve; the first job to arrive at a work centre is processed first
|
|
|
|
begynn å lære
|
|
earliest due date; the job with the easiest due date is processed first
|
|
|
|
begynn å lære
|
|
shortest processing time first
|
|
|
|
begynn å lære
|
|
longets processing time first
|
|
|
|
begynn å lære
|
|
critical ratio; the ratio of time remaining to required work time remaining is calculated and jobs are schedules in order of increasing ratio; CR = time remaining/work days remaining -> process jobs with the smallest CR first
|
|
|
Criteria to evaluate priority rules begynn å lære
|
|
Average Completion Time= Sum of flow times / # jobs; Utilisation = Sum process time / sum flow time; Average number of jobs in system Sum Flow time /Sum processing time; average jobs lateness = sum late times / number of jobs
|
|
|
