Kristen’s Cookie Case Study
CHAPTER 4: FLOW TIME ANALYSIS
4.3 Solutions to the Problem Set
Problem 4.1
[a] Draw a process flow diagram.
[b]. The theoretical flow time is 36 minutes:
There are three paths through the system:
A: Take Order – Food – Deliver – Bill → 4 + 18 + 12 + 2 = 36 mins
B: Take Order – Wine – Deliver – Bill → 4 + 4.8 + 12 + 2 = 22.8 mins
C: Take Order – Cart – Deliver – Bill → 4 + 10 + 12 + 2 = 28 mins
Path A is critical so the TFT is 36 minutes
[c]. The flow time efficiency is 36/60 = 60%
Problem 4.2
[a] The flow chart of the process is as shown in Figure TM-4.1.
Figure TM-4.1. Flow chart of the Kristen Cookies Process flow
Flow unit = 1 order of 1 dozen the theoretical flow time is 26 minutes. This is determined by adding the activity times from start to finish for 1 dozen cookies.
[b] Flow unit = 1 order of 2 dozen. To determine the theoretical flow time for this flow unit, we first observe that certain activities can be performed in parallel. For example, while the oven is baking the first dozen, You can spoon the dough for the second dozen into another tray. Therefore, the flow time of such an order is not simply the sum of the activity times. A useful tool is a Gantt chart that shows the times during which different resources of interest are occupied for various activities. A Gantt chart for the three resources executing an order of 2 dozen cookies is shown in Figure TM-4.2. The dough for the 2 dozen cookies is mixed by You in 6 minutes and subsequently you spoon dough for 1 dozen in 2 minutes. Therefore in the 8th minute, the RM is ready to load the oven and set timer, which takes 1 minute. The oven starts baking the first dozen at the 9th minute and completes baking at the 18th minute. Meanwhile, You spoon the second dozen into another tray. At the 18th minute, the RM unloads the first tray from the oven and loads the second tray into the oven and sets the timer. So the second dozen starts baking at the 19th minute. While the
4.3 Solutions to the Problem Set
Problem 4.1
[a] Draw a process flow diagram.
[b]. The theoretical flow time is 36 minutes:
There are three paths through the system:
A: Take Order – Food – Deliver – Bill → 4 + 18 + 12 + 2 = 36 mins
B: Take Order – Wine – Deliver – Bill → 4 + 4.8 + 12 + 2 = 22.8 mins
C: Take Order – Cart – Deliver – Bill → 4 + 10 + 12 + 2 = 28 mins
Path A is critical so the TFT is 36 minutes
[c]. The flow time efficiency is 36/60 = 60%
Problem 4.2
[a] The flow chart of the process is as shown in Figure TM-4.1.
Figure TM-4.1. Flow chart of the Kristen Cookies Process flow
Flow unit = 1 order of 1 dozen the theoretical flow time is 26 minutes. This is determined by adding the activity times from start to finish for 1 dozen cookies.
[b] Flow unit = 1 order of 2 dozen. To determine the theoretical flow time for this flow unit, we first observe that certain activities can be performed in parallel. For example, while the oven is baking the first dozen, You can spoon the dough for the second dozen into another tray. Therefore, the flow time of such an order is not simply the sum of the activity times. A useful tool is a Gantt chart that shows the times during which different resources of interest are occupied for various activities. A Gantt chart for the three resources executing an order of 2 dozen cookies is shown in Figure TM-4.2. The dough for the 2 dozen cookies is mixed by You in 6 minutes and subsequently you spoon dough for 1 dozen in 2 minutes. Therefore in the 8th minute, the RM is ready to load the oven and set timer, which takes 1 minute. The oven starts baking the first dozen at the 9th minute and completes baking at the 18th minute. Meanwhile, You spoon the second dozen into another tray. At the 18th minute, the RM unloads the first tray from the oven and loads the second tray into the oven and sets the timer. So the second dozen starts baking at the 19th minute. While the