Question 18) Which dispatching rule ordinarily gives the best results when the c

Question

Question 18)

Which dispatching rule ordinarily gives the best results when the criterion is lowest time for completion of the full sequence of jobs?

Question 19)

Five jobs are waiting for processing through two work centers. Their processing time (in minutes) at each work center is contained in the table below. Each job requires work center Sigma before work center Delta. According to Johnson's rule, what sequence of jobs will minimize the completion time for all jobs?

Job

Sigma

Delta

R

40

10

S

25

30

T

50

20

U

35

35

V

55

15

Question 20) Lead time for computers is 7 days with daily demand of 5 computers and a safety stock of 1 day. Each kanban holds 8 computers. What is the correct number of kanbans?

Job

Sigma

Delta

R

40

10

S

25

30

T

50

20

U

35

35

V

55

15

Explanation / Answer

18) The 'lowest slack first' dispatching rule gives the lowest time for completion of full job sequence.

19)

As per the Johnson's rule, from the table, you first find the job operation with least processing time.If this process is at the first workcentre (sigma) then this job should be done first and should be elimated from the sequence. If it is at the second workcentre, then it should be done last. In this way sequence is built by repeating the steps after each job is eliminated.

In this case, activity having least process time is Job 'R' at delta (10 minutes). Since it is at the second workcentre, job 'R' should be placed last in the sequence and be eliminated.

_ _ _ _ R

Next lowest is V at delta (15 minutes) . Again, since it is at the second workcentre, it should be placed at the last available slot

_ _ _ V-R

Next lowest is T at Delta (20 minutes). Follwing the same logic above, it should be placed at the last available slot.

_ _ T-V-R

Next lowest is S at Sigma (25 minutes). Since this is on the first workstation, it should be placed on the earliest available slot.

S _ T-V-R

Last remaining job is U. So the final sequence is

S-U-T-V-R

20) To find the number of kanbans, you first need to find the maximum stock level necessary.

Maximum stock level = Re-order level = (lead time * daily demand) + safety stock = (7 * 5) + 5 = 35 + 5 = 40 computers

Since each kanban holds 8 computers, number of kanbans required are 40/8 = 5 kanbans

Job Sigma Delta R 40 10 S 25 30 T 50 20 U 35 35 V 55 15

Related Questions

Navigate

• Browse (All)
• Browse Q
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.