Question

a) Using the EDD (earliest due date) decision rule for sequencing the jobs, the order is (to resolve a tie, use the order in which the jobs were received): At Morgan's Transformer Rebuilding, following jobs (below) are ready for dispatching to a work center. The processing times, date job received, and due dates for the jobs are given below. In what sequence would the jobs be ranked according to the decision rules on the left Sequence Job 1 Date Job Job Received Due Date Processing (days) A 110 180 20 120 200 30 4 C 122 175 10 125 230 16 E 130 210 18 The total flow time for the sequence developed using the EDD rule response to two decimal places) days (round your All dates are according to shop calendar days. Today on the manufacturing planning calendar is day 132. Compute all times based on initiating (starting) work on day 132. The percentage utilization for the sequence deeveloped using the EDD rule response as a percentage rounded to two decimal places) % ( enter your The average number of jobs in the system for the sequence developed using the EDD rule = jobs (round your response to two decimal places) The average tardiness (job lateness) for the sequence developed using the EDD rule days (round your response to two decimal places). b) Using the SPT (shortest processing time) decision rule for sequencing the jobs, the order is (to resolve a tie, use the order in which the jobs were received): Sequence Job 2 3 4 5 The total fiow time for the sequence developed using the SPT rule=days (round your response to two decimal places) The percentage utilization for the sequence deeveloped using the SPT rule response as a percentage rounded to two decimal places) % (onter your The average number of jobs in the system for the sequence developed using the SPT rule jobs (round your response to two decimal places) The average tardiness ob lateness) for the sequence developed using the SPT rule days (round your response to two decimal places).

Answer 1

a)

Using EDD (earliest due date), we will sequence jobs with earliest due date first and then so on and so forth.

Sequence	Job	Due date
1	C	175
2	A	180
3	B	200
4	E	210
5	D	230

We will calculate other parameters as below

Sequence	Job	Processing (Days)	Flow Time	Due date
1	C	10	10	175
2	A	20	30	180
3	B	30	60	200
4	E	18	78	210
5	D	16	94	230
Total		94	272

Total flow time for sequence using EDD rule is 272 days.

Percentage utilization for sequence developed using EDD rule is 94/ 272 = 0.3456 or 34.56%

Average number of jobs in the system for sequence developed using EDD rule is 272/ 94 = 2.89 jobs.

For calculating tardiness, we will have to consider that starting work day is 132 and calculated tardiness as Completion date - Due date (0 if negative)

Sequence	Job	Processing (Days)	Date Job Received	Completion date	Due date	Tardiness
1	C	10	122	132 + 10 = 142	175	0 (142 - 175 is negative)
2	A	20	110	142 + 20 = 162	180	0 (162 - 180 is negative)
3	B	30	120	162 + 30 = 192	200	0 (192 - 200 is negative)
4	E	18	130	192 + 18 = 210	210	0
5	D	16	125	210 + 16 = 226	230	0 (226- 230 is negative)
Total		94				0

Hence, Average tardiness (or job lateness)  for sequence developed using EDD rule is 0/5 = 0 days.

b)

Using SPT (shortest processing time) rule, we will sequence shortest time job first and so on and so forth.

Sequence	Job	Processing (Days)
1	C	10
2	D	16
3	E	18
4	A	20
5	B	30

We will calculate other parameters as below

Sequence	Job	Processing (Days)	Flow time
1	C	10	10
2	D	16	26
3	E	18	44
4	A	20	64
5	B	30	94
Total		94	238

Total flow time for the sequence developed using SPT rule = 238 days

Percentage utilization for the sequence developed using SPT rule = 94/ 238 = 0.3950 or 39.50%

Average number of jobs in the system for the sequence developed using SPT rule = 238/ 94 = 2.53 jobs

For calculating tardiness, we will have to consider that starting work day is 132 and calculated tardiness as Completion date - Due date (0 if negative)

Sequence	Job	Processing (Days)	Date Job Received	Completion date	Due date	Tardiness
1	C	10	122	132 + 10 = 142	175	0 (142 - 175 is negative)
2	D	16	125	142 + 16 = 158	230	0 (158 - 230 is negative)
3	E	18	130	158 + 18 = 176	210	0 (176 - 210 is negative)
4	A	20	110	176 + 20 = 196	180	16 (196 - 180)
5	B	30	120	196 + 30 = 226	200	26 (226- 200)
Total						42

Average tardiness using SPT rule = Total tardiness/ number of jobs = 42/ 5 = 8.4 days.

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