Johnson’s 2‑Machine Sprint — Minimize makespan on M1→M2

Tip: Choose Manual (drag rows) to try beating Johnson’s makespan. Delete with ✕.

Drag Job M1 M2
M1
M2

Makespan (Cmax)

–

M2 Idle

–

M1 Utilization

–

M2 Utilization

–

Scheduling rule: repeatedly pick the smallest processing time among all remaining jobs. If the smallest is on M1, place that job next at the front; if it’s on M2, place it next at the back. Ties can be broken arbitrarily.

Instructor notes
  • Have students first press Johnson’s Rule, capture Cmax and M2 idle. Then switch to Manual and try to beat it.
  • Debrief: why does M2 often idle? Where do blocking and waiting happen? What layout or buffering changes could help?
  • Challenge: give teams a target Cmax and 3 minutes to find the best order. Fastest valid solution wins.