Chapter 16 & 9

SchedulingWork & Employees

SchedulingOutline

What needs to be scheduled?– doctor’s office, restaurant, mfg. plant, hospital– employees vs. products

Gantt charts

Dispatching (sequencing) rules for scheduling work

Scheduling employees

Shop floor control includes:

1. assigning a priority to each order2. issuing dispatching lists to each work center

(what and when to produce)3. keeping WIP inventory updated4. providing input-output control for all work

centers5. monitoring efficiency, utilization, and

productivity of workers and machines

Scheduling (Dispatching/Sequencing) Rules

FCFS – First Come, First ServedSPT – Shortest Processing TimeEDD – Earliest Due DateLeast Slack (LS)

slack = (time until due date) – (remaining lead time) process job with smallest slack first

Critical Ratio (CR)CR = (time until due date) / (remaining lead time) process job with smallest CR first

Scheduling Rules Example

Job # Due Date Remaining Lead Time

Time Until Due Date Slack CR

768 58 4

775 65 12

751 61 7

758 56 8

763 69 14

currently day 50; 5 jobs at a machine

Gantt Chart

weeks of processing time

work order # mach. A mach. B mach. C total 34 4 2 1 35 1 3 1 36 2 2 2 37 1 1 2

Gantt ChartFCFS: 34, 35, 36, 37

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

34 35 36 37

34

34

35

35

36

36

37

37C

B

A 15 weeks

Gantt ChartSPT: 37, 35, 36, 34

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

3435 3637

34

34

35

35

36

36

37

37C

B

A 11 weeks

Work-Shift Scheduling Rule(work 5 days, 2 consecutive days off)

Sun Mon Tue Wed Thu Fri Sat

2 5 3 4 2 4 5

Minimum # ofemployeesneeded

Work-Shift Scheduling Rule(work 5 days, any 2 days off)

Sun Mon Tue Wed Thu Fri Sat

2 5 3 4 2 4 5

Minimum # ofemployeesneeded

Work-Shift Scheduling Rule(work 4 days, 3 consecutive days off)

Sun Mon Tue Wed Thu Fri Sat

2 5 3 4 2 4 5

Minimum # ofemployeesneeded