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Chapter 4

Flow Time Analysis (T)

Chapter 4

Flow-Time Analysis

Chapter 5

Flow Rate and Capacity Analysis

Chapter 6

Inventory Analysis

I = R x T

Based on Anupindi, et al, MBPF (2e)

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Process Flow Time1. Flow time affects delivery response time.

2. Short flow times reduce the inventory.

3. Shorter flow time in the development process enables a company to get to market quicker giving a competitive advantage.

4. Can minimize production start to gain market information, avoid product obsolescence and minimize inventory.

5. Results in fast feedback and correction of quality problems.

6. Flow time is an integrative measure of overall process performance.

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A process flowchart is a graphical representation of the five process elements: inputs and outputs, flow units, network of activities, resources allocated to activities and information structure.

Direct measurement and indirect measurement method. Example 4.2

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4.3 Theoretical Flow Time

Example 4.4

Theoretical flow time is the minimum amount of time required for processing a typical flow unit without any waiting.

Determining the critical path

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Flow time = Theoretical flow time + Waiting time

Example 4.5

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Activity Number of WorkActivity Time (min) Visits Content (min)

1 Separate 10 1 102 Punch the base 25 1.2 303 Punch the roof 20 1.1 224 Form the base 5 1.2 65 Form the roof 10 1.2 126 Subassemble 10 1.3 137 Assemble 10 1 108 Inspect 30 1.2 36

Example 4.6 | Table 4.4

Work content = activity time * average number of visits

Flow time = value-adding flow time + non-value-adding flow time

Value-adding and Non-value-adding

Rework, Visits and Work Content

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Industry Process Average Flow Time

Theoretical Flow Time

Flow Time Efficiency

Life Insurance New Policy Application

72 hrs. 7 min. 0.16%

Consumer Packaging New Graphic Design

18 days 2 hrs. 0.14%

Commercial Bank Consumer Loan

24 hrs. 34 min. 2.36%

Hospital Patient Billing 10 days 3 hrs. 3.75%

Automobile Manufacture

Financial Closing

11 days 5 hrs 5.60%

Most time inefficiency comes from waiting: E.g.: Flow Times in White Collar Processes

Flow time efficiency = Theoretical flow time / Average flow time

Flow time efficiency X-ray VOH Example 4.7

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Levers for Reducing Flow Time• Decrease the work content of critical activities

– work smarter

– work faster

– do it right the first time

– change product mix

• Move work content from critical to non-critical activities

– to non-critical path or to ``outer loop’’

• Reduce waiting time.

“Just track any work items as it flows through the process and classify the time into one of three categories: (1) value-added work, (2) waste that is required for business reasons, and (3) delays/waste. Then draw a timeline and mark off the time segments for each of these categories. In the example shown, the value-added work (shaded above the centerline) shows the buyer in this purchasing organization is only working the order for 14 minutes of the 4 day cycle. The majority of the time, delineated by white space, is idle queueing time.”

Value Added vs. NVA Time

Lean Six Sigma by George, et al.

Source: Lean Learning Center, Value Stream Mapping Course Notes.

Source: Lean Learning Center, Value Stream Mapping Course Notes.

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source: Finch, Operations Now

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source: Finch, Operations Now

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source: Finch, Operations Now

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source: Finch, Operations Now