9.11 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:

Task                Time               Immediate Processor

            A                     12                    –

            B                     15                    A

            C                     8                      A

            D                     5                      B,C

            E                      20                    D

Rosenberg’s goal is to produce 180 PDAs per hour.

 a) What is the cycle time?

b) What is the theoretical minimum for the number of workstations that Rosenberg can achieve in this assembly line?

c) Can the theoretical minimum actually be reached when workstations are assigned?

 9.13 Sue Helms Appliances wants to establish an assembly line to manufacture its new product, the Micro Popcorn Popper. The goal is to produce five poppers per hour. The tasks, task times, and immediate predecessors for producing one Micro Popcorn Popper are as follows:

Task                Time               Immediate Predecessors

A                     10                    –

            B                     12                    A

            C                     8                      A,B

            D                     6                      B,C

            E                      6                      C

            F                      6                      D,E

a) What is the theoretical minimum for the smallest number of workstations that Helms can achieve in this assembly line?

b) Graph the assembly line and assign workers to workstations. Can you assign them with the theoretical minimum?

 c) What is the efficiency of your assignment?

9.15 The following table details the tasks required for Indiana-based Frank Pianki Industries to manufacture a fully portable industrial vacuum cleaner. The times in the table are in minutes. Demand forecasts indicate a need to operate with a cycle time of 10 minutes.

Activity           Activity Description              Immediate Predecessors                   Time  

A                     Attach wheels to tub                           —                                           5

B                     Attach motor to lid                             —                                           1.5

C                     Attach battery pack                            B                                             3

D                     Attach safety cutoff                           C                                             4

E                      Attach filters                                       B                                             3

F                      Attach lid to tub                                 A, E                                         2

G                     Assemble attachments                                    —                                           3

H                     Function test                                       D, F, G                                    3.5

I                       Final inspection                                   H                                             2

J                       Packing                                               I                                               2

a) Draw the appropriate precedence diagram for this production line.

b) Assign tasks to workstations and determine how much idle time is present each cycle.

c) Discuss how this balance could be improved to 100%.

d) What is the theoretical minimum number of workstations?