1. Scheduling

2. Definition of scheduling Establishing the timing of the use of equipment, facilities and human activities in an organization In the decision-making hierarchy, scheduling decisions are the final step in the transformation process before actual output occurs. Effective scheduling can yield – Cost savings – Increases in productivity

3. Volume Scheduling tasks are largely a function of the volume of system output. – High-volume systems – Intermediate-volume systems – Low-volume systems

4. High-Volume Systems Flow system: High-volume system with Standardized equipment and activities Flow-shop scheduling: Scheduling for high-volume flow system Goal: a smooth rate of flow of goods or customers through the system to get a high utilization of workforce and equipment Highly repetitive nature system leads to: – …the determination of many loading and sequence decisions during the design of the system, – …highly specialized: tools and equipnment, arrangement, division of labour – automatization

5. Balancing the line Allocating the required tasks to workstationsso that they satisfy technical (sequencing) constraints and are balanced with respect to equal work times among stations. Goal: maximum utilization and highest possible output rate

6. Hindrances of highly specialized jobs Discontent of workers: – Too simple tasks: monotonous, boring – Give rise to atigue, absenteesm, turnover – Reduce productivity

7. High-Volume Success Factors Process and product design: manufacturability Preventive maintenance: to minimize disruption of the flow of work Rapid repair when breakdown occurs Optimal product mixes: linear programming Minimization of quality problems: to minimize disruption Reliability and timing of supplies: to avoid shortages (a and high carrying costs)

8. Intermediate-Volume Systems Outputs are between standardized high- volume systems and made-to-order job shops – Usually standard outputs – Not continuous but intermittent production (periodical shifts from one job to another) – Run size (large), timing, and sequence of jobs Economic run size: MRP approach

9. Setup costs Depend on the similarity of products Complex sequencing problem: different setup costs for every combination Off-line setups, modular set-ups, flexible equipment

10. Scheduling in Low-Volume Systems Products made to order not to inventory Orders can be very different Job-shop scheduling: Scheduling for low-volume systems with many variations in requirements Schedules cannot be made prior to actual job order Loading - assignment of jobs to process centres and to various machines in the centres Sequencing - determining the order in which jobs will be processed

11. Aims of loading Find arrangement to minimize: – Processing and setup costs – Idle time among work centres and machines – Job completition time

12. Gantt load charts Visual aid Depicts the loading and iddle times for a group of machines or departments Trial-and-error schedule development

13. Infinite loading: jobs are assigned without regard to the capacity of work centres. This can lead to over- and underloads. Finite loading: takes into account the work center capacity and job processing times. Need frequent updating. Forward scheduling: scheduling ahead from a point in time. ‘How long will it take to complete this job?’ Backward scheduling: scheduling backward from due date. ‘When is the latest job can be started?’ Loading

14. Gantt schedule chart Shows the orders or jobs in progress and whether they are on schedule – horizontal axis: time, – vertical axis: jobs in progress

15. Sequencing Sequencing: Determine the order in which jobs at a work center will be processed (and the order in which jobs are processed at individual workstations within work centers). Crucial if work centres are heavily loaded. Workstation: An area where one person works, usually with special equipment, on a specialized job.

16. Sequencing Priority rules: Simple heuristics used to select the order in which jobs will be processed. Job time: Time needed for setup and processing of a job.

17. Priority Rules FCFS - first come, first served SPT- shortest processing time EDD - earliest due date CR - critical ratio S/O - slack per operation Rush - emergency Top Priority

18. Effectiveness of a given sequence Job flow time: the length of time a job is at a particular workstation or work center. Processing time + waiting Job lateness: the length of time the job completition date is expected to eyceed the date the job was due or promised to a customer. Actual completition time – due date Makespan: total time needed to complete a group of jobs from the beginning of the first job to the completition of the last job Average number of jobs: total flow time / makespan

19. Thank you for your attention!