Question

A customer who wants a coffee moves sequentially to 2 stations staffed by 4 employees in a Starbucks: The customer first moves to one of the two cash registers where Alex and Bob are working. One of them places the order and accepts payment. There is one extra cash register where no one is working. One of Charlotte and David makes the coffee using a coffee machine. Both Charlotte and David have their own coffee machines. There is one extra coffee machine which is not used by anyone.

The task time of placing an order and accepting payment is 45 seconds. The task time of making a coffee is 60 seconds.

Tasks Task time Place an order & accept payment 45 seconds Make a coffee 60 seconds

Note: Alex & Bob take the same amount of time to do their tasks. Charlotte & David take the same amount of time to do their tasks.

(a) Draw the process flow diagram.

(b) What is the process capacity and what is (are) the bottleneck(s) of the process?

(c) What is the cycle time of the process?

(d) What is the flow time of the process?

(e) The Starbucks recruits a new staff Elena. It takes Elena 45 seconds to place an order & accept payment and 60 seconds to make a coffee. To improve the process capacity, which task should Elena be assigned to? What is the new process capacity?

Answer 1

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Output of the first station = 60x60/45x2= 160 per hour

Output of the second station = 60x60/60 x2 =120 per hour

Process capacity is equal to the slowest station ( station 2)which is 120 per hour.

station 2 is bottleneck with  capacity of 120

cycle time= 60/120 =0.5 min = 30 sec.

flow time for a unit = 45+60 =105 sec.

If a new resource is assigned to the process, it should be assigned to the slower process hich is stage 2 ( coffee making) The new capacityof stage 2 would be

3x60x60/60 =180

New capacity would be now 160, which is eual to the capacity of slower station which is now 1, with capacity of 160.