Q4(a)A vehicle repainting operation uses a two-step sequence that all jobs in a certain category follow. For the group of jobs listed in the Table 3, the operations coordinator has planned for a job sequence of ABCDE. Using Johnson method, prove that the operations coordinator plan is not an optimum solution.

(10 marks)

Table 3: Processing time (hours)

Job / Workstation 1 / Workstation 2
A / 5 / 10
B / 3 / 4
C / 7 / 6
D / 12 / 5
E / 9 / 11

(b)A lumber manufacturing company has four (4) jobs as shown in Table 4. In what sequence would the jobs be ranked according to the critical ratio rule?

Table 4: Jobs due date and processing time

Job / Due date / Processing Time (days)
A / 7 / 6
B / 4 / 3
C / 3 / 3
D / 5 / 8

Q2(a)The times required to complete each of five jobs in a two-machine flow shop are shown in Table 2. Each job must follow the same sequence, beginning with machine A and moving to machine B.

(i)Determine a sequence that will minimize makespan time. (4 marks)

(ii)Construct a chart of the resulting sequence, Identify the completion time of D at Machine 2.

( 4 marks)

Table 2: Processing job data

Job / TIME (HOURS)
Machine 1 / Machine 2
A / 16 / 5
B / 3 / 13
C / 9 / 6
D / 8 / 7
E / 2 / 14

Q3Table 2 contains information concerning four jobs that are awaiting processing at a work center. The list of jobs in Table 2 is by order of its arrival.

(a)Sequence the jobs using:

(i)FCFS.

(ii)SPT.

(iii)EDD.

(iv)CR.

(b)For each of the methods in part (a), determine:

(i)The average job flow time.

(ii)The average tardiness.

(iii)The average number of jobs at the work center.

Table 2: List of jobs to be processed in a work center

Job / Job time (days) / Due date (days)
A / 14 / 20
B / 10 / 16
C / 7 / 15
D / 6 / 17

(20 marks)

Q6(a)Explain forward and backward scheduling.

(2marks)

(b)There are three machines and seven jobs to be processed in the same way as given in Table 5. Using Johnson’s rule approach, find the optimum sequence on which all the jobs are to be processed, total elapsed time, and idle time of each machine.

Table 5

Jobs
Machine / A / B / C / D / E / F / G
M1 / 3 / 8 / 7 / 4 / 9 / 8 / 7
M2 / 4 / 3 / 2 / 5 / 1 / 4 / 3
M3 / 6 / 7 / 5 / 11 / 5 / 6 / 12

(8 marks)

(c)Table 6 contains information concerning four jobs that are awaiting processing at a work center. The jobs are supposed to be arranged following the sequencing rules of:

(i)FCFS (First come first served)

(ii)SPT (Shortest processing time)

(iii)EDD (Earliest due date)

(iv)LPT (Longest processing time)

Based on the analysis, suggest the suitable process to be followed for economic utilization of the work center.

Table 6

Job / Job time (days) / Due dates
A / 28 / 38
B / 9 / 15
C / 7 / 17
D / 6 / 18

(10 marks)

Q3Table 5shows the task times and predecessor relationships for a newly introduced product in an assembly line. The output rate for the assembly line is targeted at 30 units per hour. Using the ranked positional weight technique, analyze the problem and propose a balanced line for the assembly process. Support your analysis with proper precedence diagram, cycle time determination, work station balancing steps, actual line efficiency computation and total idle time (balance delay).

(20 marks)

Table 5: Assembly tasks information

Task / Time Required (seconds) / Immediate Predecessors
A / 55 / -
B / 45 / -
C / 25 / A
D / 50 / A
E / 30 / C
F / 22 / B,D
G / 33 / F
H / 48 / F
I / 70 / E
J / 68 / G,H
K / 58 / I,J

Q2Table 2 shows the task times and predecessor relationships for a newly introduced product in an assembly line. The management has decided to have the output rate of 45 units per hour. Using the ranked positional weight technique, analyse the problem and propose a balanced line for the assembly process. Support your analysis with proper precedence diagram, cycle time determination, work station balancing steps, actual line efficiency computation and total idle time (balance delay).

Table 2: Assembly tasks information

Task / Time Required (seconds) / Immediate Predecessors
A / 55 / -
B / 45 / -
C / 25 / -
D / 50 / A,C
E / 30 / B
F / 22 / D
G / 33 / D
H / 48 / E,F
I / 70 / G
J / 68 / G,H
K / 58 / I,J

(15 marks)

Q2The production coordinator for an assembly plant is considering taking a new long term order for one of the assembly line. The task times and predecessor relationships for the new order are given in Table 3. The desired output rate is targeted at 40 units per hour. Using the ranked positional weight technique, analyse the problem and propose a balanced line for the assembly process. Support your analysis with proper precedence diagram, cycle time determination, work station balancing steps, actual line efficiency computation and total idle time (balance delay).

(20 marks)

Table 3: Assembly tasks information

Task / Time Required (seconds) / Immediate Predecessors
A / 55 / -
B / 45 / -
C / 25 / -
D / 50 / A,B
E / 30 / C
F / 22 / D
G / 33 / D
H / 48 / E
I / 70 / G
J / 68 / G,H
K / 58 / F,I,J

Q2Table 2 shows the task times and predecessor relationships for an assembly line in automotive industry. The desired output rate is targeted at 2000 units per week and the assembly line is operating at 40 hours per week. Using the ranked positional weight technique, analyse the problem and propose a balanced line for the assembly process. Support your analysis with proper precedence diagram, cycle time determination, and work station balancing steps.

Table 2: Assembly tasks information

Task / Time Required (seconds) / Immediate Predecessors
A / 70 / -
B / 45 / -
C / 28 / -
D / 30 / A,B,C
E / 55 / D
F / 22 / B
G / 33 / E,F
H / 48 / G
I / 38 / A,F
J / 65 / E
K / 28 / J
L / 40 / H,I,K

(15 marks)