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 …show more content…

The length of paths 1 and 2 are computed to be equal to 92.5 and 110.5 minutes respectively. Therefore the theoretical flow time for a mixture of 75% standard and 25% Deluxe is 110.5 minutes.

[c] The flow time efficiency is 110.5/4800 = 2.3%
Problem 4.4

[a] A process flow chart identifying resources, activity times and any potential storage buffers is given in Figure TM-4.3.
[b] We have 4 paths, the critical path is the longest path = 37 minutes (going through seat assembly). Therefore, the theoretical flow time = 37 minutes.
[c] We decrease the theoretical flow time only by decreasing the length of the critical path. Thus we need to decrease the theoretical flow times of seat assembly and/or final assembly: try to change the design and process so that we can perform subtasks in parallel.

Deluxe Garage Work Content (minutes) Activity Activity Time Number of 75% Standard and (Minutes) Visits Deluxe Standard 25% Deluxe
1 Separate 10 1 10 10 10
2 Punch the base 30 1.5 45 30 33.75
3 Punch the roof 24 1.25 30 22 24
4 Form the base 5 1.2 6 6 6
5 Form the roof 10 1.2 12 12 12
6 Sub-assemble 15 1.2 18 13 14.25
7 Assemble 12 1 12 10 10.5
8 Inspect 30 1.2 36 36 36

Table TM-4.2: Work Content computation for Problem 4.2

Figure TM-4.3: Flow Chart for Problem Set 4.4 (a)

4.5

[a] A process map

[b] The theoretical flow time is 50 minutes. The critical path is the