Stanford Rosenberg Computing wants to establish an assembly line for producing a

Question

Stanford Rosenberg Computing wants to establish an assembly line for producing a new? product, the Personal Digital Assistant? (PDA). The? tasks, task? times, and immediate predecessors for the tasks are as? follows:

Rosenberg's goal is to produce 170 PDAs per hour.

?a) The cycle time for the production of a PDA? = _____ seconds ?(round your response to two decimal? places).

?b) The theoretical minimum number of workstations that Rosenberg can achieve in this assembly

line = _____ ?(round your response up to the next whole? number).

?c) For one to assign the tasks to the actual workstations and be able to use the? "theoretical minimum"? number, the activity assignment should? be:

Were you able to assign all the tasks to the theoretical minimum number of? workstations? (Yes/No)

g wants to establish an assembly line for producing a new produc sk times, and immediate predecessors for the tasks are as follows Time (sec) Immediate Predecessor Task 14 B, C 20 170 PDAs per hour

Explanation / Answer

a) Given,

Demand = 170 PDA per hour = 170 per 3600 sec

So, cycle time = 3600/170 = 21.176 sec = 21.18 sec

b) Minimum number of workstations= sum of total task times / cycle time

                        = (11+14+8+4+20)/21.18 = 2.69 = 3 workstations

c)

Task Table

Task

Task time

Precedence

A

11

-

B

14

A

C

8

A

D

4

B,C

E

20

D

The total station time is nothing but the cycle time. So, total station time of each station is 21.18 sec

In order of longest operation time, tasks: E->B->A->C->D

               Workstation 1:

                        First task =A (as E and B are dependent on A)

                        Time left= 21.18-11 = 10.18 sec

                       

So, workstation 1: A

Workstation 2:

                        First task =B (as E is dependent on B)

                        Time left= 21.18-14 = 7.18 sec

                       

So, workstation 2: B

Workstation 3:

                        First task=C (as E is dependent on D, which is dependent on C)

                        Time left= 21.18-8 = 13.18 sec

                        Second task=D (as E is dependent on D)

                        Time left=13.18-4 = 9.18 sec

So, workstation 3: C->D

No workstation is left for assignment of task E, if following the theoretical minimum rule.

Workstation 4:

                        First task= E

                        Time left=21.18-20 = 1.18 sec

So, workstation 4: E

Work Station

Tasks

Workstation Time

Idle Time

1

A

11

10.18

2

B

14

7.18

3

C->D

12

9.18

4

E

20

1.18

Were you able to assign all the tasks to the theoretical minimum no of workstations: No

Total idle time = 10.18+7.18+9.18+1.18 = 27.72 sec

Efficiency with 4 workstations = (sum of all tasks) / (no of workstations * Cycle time) = (57)/ (4*21.18) = 0.673 or 67.3 %

Task

Task time

Precedence

A

11

-

B

14

A

C

8

A

D

4

B,C

E

20

D

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