Unformatted text preview: 54 Interactive Models for Operations and Supply Chain Management The Sequencing Rules Model The Sequencing Rule Interactive Model provides a quick and easy way to compare
the performance of several traditional sequencing rules. The technlques included
for comparison are earliest due date (EDD), shortest processing time (SPT), criti—
cal ratio (CR), and ﬁrst-come, ﬁrst-served (FCF S). The user has the option of us1ng
the default data or entering new data for estimated completion time and due date.
The user must also select the number of orders to be sequenced. By selecting the
rule to be applied and clicking on the “Schedule” button, the model resequences
the orders and provides a color-coded Gantt chart of the resulting schedule. When
orders are projected to be completed after their due date, a line showing the due
date is also provided. Performance measures of total days late, number of orders
late, and average lateness are provided.
Exhibit 5.7 shows the Sequencing Rules Model. EXHIBIT 5.7 Screen View of the Sequencing Rules Model wvwmwmm mammamt . <l/wW1-«W NW... '4 .mmemw M mew:mam“war-m».may»... t. Inventory Management and SCheduling 55 Interactive Case Sequencing Jobs at Jensen’s Custom Auto Restoration Jensen’s Custom Auto Restoration specializes in refurbishing sports cars from the
1950s, 1960s, and 19705. Jensen’s capabilities range from mechanical engine work
to body and paint projects. As a part of the cost estimation process, Bill Jensen
estimates the number of days to complete each job and negotiates a due date based
on the projected time to complete the project and the availability of necessary
parts. History shows that Bill has been quite accurate at estimating time to com-
plete various jobs. Bill wishes to evaluate the potential of using sequencing rules
that differ from his typical “ﬁrst-come, ﬁrst-served” approach to sequencing
restoration jobs. Analysis 1. Use the default data for the ﬁve jobs to be sequenced, as shown below, and sequence the
jobs by earliest due date. Job ID Estimated Completion Time Due Date
*- A 3 5
B 4 6 _l
C 2 7
D 6 9
E 1 2 a. Record the performance measures and re-sequence by shortest processing time. How
does the performance of the two rules compare on total days late, number of j obs late,
and average lateness? Were you surprised by the results? b. Which rule would you select? Explain your answer. 2. Again, use the default data for the ﬁve jobs to be sequenced, and sequence the orders by the critical ratio rule. Record the performance measures.
a. Resequence the orders by ﬁrst-come, ﬁrst-served and compare the results. b. Rank the four rules for each performance measure. How does the performance of the
four rules compare? 3. As new jobs come in, they must be added into the sequence. Suppose that as Job B was completed, a new order arrived. Delete the estimated completion time and due date for
job B and replace them with an estimated processing time of 8 and a due date 0f 17.
Resequence the orders, again using shortest processing time. What position does that
order take in the sequence? What happens to the performance measures? 4 ,ér? 4 . r ...
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- Spring '08