ME.6.MC:5.2 - Compare parallel checks with their shared capacity exposed

A team considers one automated test bench versus two independent benches. Two preparations can run independently from time zero, each with its own analyst. Preparation A takes three minutes; preparation B takes two. Each subsequent check occupies a bench for four minutes. Both completed check results are required for one minute of final assembly.

For this calculation, durations are fixed, the work is nonpreemptive, and setup and transfer times are zero. Benches and the final assembler are available when needed, with no competing work. Checks initially require no continuously attending operator. The required completion time is at most ten minutes.

With two benches, check A runs from minute 3 to 7 and check B from 2 to 6. Assembly runs from 7 to 8. The model admits completion at minute 8.

With one bench, the two checks cannot overlap. A feasible schedule is B from 2 to 6, A from 6 to 10, and assembly from 10 to 11. No schedule finishes earlier: the bench cannot start a check before minute 2 and must perform eight minutes of check work before the final assembly minute. Thus eleven minutes is both a lower bound and an achieved value.

The one-bench arrangement fails the ten-minute criterion under these premises. The two-bench arrangement passes that criterion in the constructed schedule. Whether acquiring or allocating another bench is worthwhile remains a choice involving its availability and other burdens. The calculation does not supply those missing facts.

Changed premise. Both checks now require one qualified operator throughout, and only one such operator is available from minute 2 onward. Add a capacity-one operator constraint to the model. Two benches no longer permit overlap: there are still eight exclusive operator minutes, no check can begin before minute 2, and assembly follows both checks. The eleven-minute lower bound applies again and the same serial schedule attains it.

A hardware-only proposal therefore does not repair the deadline under the changed condition. The useful next comparison concerns an available arrangement that changes the limiting condition, or a justified change of requirement. Merely redrawing two parallel lanes leaves the conflict in place.