Scheduling · Industrial Engineering · GATE ME

A set of jobs $U, V, W, X, Y, Z$ arrive at time $t = 0$ to a production line consisting of two workstations in series. Each job must be processed by both workstations in sequence (i.e., the first followed by the second). The process times (in minutes) for each job on each workstation in the production line are given below.

The sequence in which the jobs must be processed by the production line if the total makespan of production is to be minimized is

Four jobs are on order in a factory. As on day 20 of the production calendar, the corresponding due date and work remaining to complete these jobs (in days) are given in the table below.

$$ \begin{array}{|c|c|c|} \hline \text { Job } & \text { Due date } & \text { Work remaining (in days) } \\ \hline \text { M } & 26 & 5 \\ \hline \text { N } & 24 & 10 \\ \hline \text { O } & 28 & 10 \\ \hline \text { P } & 31 & 5 \\ \hline \end{array} $$

Which job(s) has/have critical ratio less than unity?

Parts P1 - P7 are machined first on a milling machine and then polished at a separate machine. Using the information in the following table, the minimum total completion time required for carrying out both the operations for all 7 parts is _______ hours.

Using the Shortest Processing Time $$(SPT)$$ rule, total tardiness is

If the Earliest Due Date $$(EDD)$$ rule is used to sequence the jobs, the number of jobs delayed is

Average flow time (in days) for the above jobs using Shortest Processing Time rule is

A schedule that minimizes the total inventory cost is

Assume that all orders are ready for processing. Give a production schedule that minimizes the average flow time. Compare this schedule with one that minimizes tardiness (lateness).

Which schedule will minimize the total cost?
What is the minimum total cost?
Which jobs (if any) fail to meet their due dates?

Considering mean lateness and mean flow time, evaluate the shortest-time rule and least-slack rule and recommend the desirable rule.