TOM Mid- Ch. 3-4

What is a process flow diagram?

A visual map showing the steps, resources, and movement of a flow unit through a process.

What should you do first when analyzing a process?

Draw a process flow diagram.

What is a flow unit?

The item being studied as it moves through a process.

Examples: a customer, sandwich, package, or patient.

4. What is a resource?

A person, group of people, machine, or equipment that transforms inputs into outputs.

What does “upstream” mean?

The earlier part of the process, closer to the beginning.

What does “downstream” mean?

The later part of the process, closer to the end.

What do arrows represent on a process diagram?

The movement or flow of the flow unit.

8. Why can waiting customers be considered inventory?

They are flow units waiting for a resource to serve them.

9. What is a value-added activity?

An activity that increases the value of a product or service and cannot be removed without harming the process.

10. What is a non-value-added activity?

An activity that uses time or resources but does not increase customer value.

Examples: waiting, overproduction, unnecessary movement, and correcting errors.

What is a value stream map?

A process map that identifies value-added and non-value-added activities, often including their time and cost.

What is the purpose of value stream mapping?

To identify and reduce waste, making the process more efficient.

What is capacity?

The maximum output a resource or business can produce during a specific period.

What is process capacity?

The maximum flow rate that an entire process can provide per unit of time.

What is flow rate?

The actual rate at which flow units move through a process.

What is the formula for flow rate?

Flow Rate=min(Demand Rate,Process Capacity)

The smaller number determines the flow rate.

17. What is demand rate?

The number of flow units customers want per unit of time.

18. What is the difference between capacity and flow rate?

• Capacity is what the process could produce.

• Flow rate is what the process actually produces.

19. What does it mean to be capacity-constrained?

Demand is greater than process capacity.

Example: Demand = 40 customers/hour, capacity = 30 customers/hour.

Flow rate = 30 customers/hour.

What does it mean to be demand-constrained?

Process capacity is greater than demand.

Example: Demand = 20 customers/hour,

capacity = 30 customers/hour.

Flow rate = 20 customers/hour.

A worker takes 120 seconds to serve one customer. What is the capacity?

The capacity is 30 customers per hour.

22. A printer takes 10 seconds to print one poster. What is its hourly capacity?

10 seconds / 3600 seconds​ = 360 posters/hour

Capacity = 360 posters per hour

What is a bottleneck?

The resource with the lowest capacity in a process.

24. Why is the bottleneck important?

It limits the capacity and flow rate of the entire process.

What are common effects of a bottleneck?

Long waiting lines, excess inventory, production delays, inefficiency, and lower employee morale.

26. How can a bottleneck be improved?

Add workers or equipment, reduce setup time, eliminate unnecessary work, reduce downtime, or improve the bottleneck’s speed.

In a series process, how do you calculate process capacity?

Process Capacity = min (Capacity of each resource)

Smallest resource capacity = process capacity

A process has capacities of 100, 80, and 120 units/hour. What is the bottleneck?

The resource with capacity 80 units/hour.

What is the process capacity in that example?

80 units per hour, because the bottleneck limits the whole process.

What is flow time?

The total time a flow unit spends in the process from beginning to end.

What is cycle time?

The time between completing two consecutive flow units.

What is the formula for cycle time?

Cycle Time= 1 / Flow Rate

33. If a process produces 30 customers per hour, what is its cycle time?

1 hour / 30 customers ​= 2 minutes per customer

34. What is lead time?

The time between placing an order and receiving it.

35. What is the difference between cycle time and lead time?

Cycle time measures the spacing between completed units.

Lead time measures how long one order takes from placement to delivery.

36. What is utilization?

How much of a resource’s capacity is being used.

37. What is the formula for utilization?

Utilization = Flow Rate / Resource Capacity

• muktioly by 100 to express a percentage

A resource has a capacity of 50 units/hour and processes 40 units/hour. What is utilization?

40 / 50 = 0.80 = 80%

What does 100% utilization mean?

The resource is operating at its full capacity.

40. Can utilization be greater than 100%?

Usually, no. If calculations show utilization above 100%, demand exceeds the resource’s capacity and the process is capacity-constrained.

41. Which resource usually has the highest utilization?

The bottleneck, because it has the lowest capacity and limits the process.

Airport security has these steps:

• Verify documents: 30 seconds per passenger

• Metal detector: 10 seconds per passenger

• X-ray machine: 60 seconds per passenger

Capacity for each step?

• Document checl: 36000 / 30 = 120 passengers/hr

• Metal detector: 36000 / 10 = 360 passengers per hr

• X-Ray: 36000 / 60 = 60 passengers per hour

Which step is the bottleneck?

The X-ray machine, because it has the lowest capacity.

What is the process capacity?

• Document checl: 36000 / 30 = 120 passengers/hr

• Metal detector: 36000 / 10 = 360 passengers per hr

• X-Ray: 36000 / 60 = 60 passengers per hour

60 passengers per hour.

If many passengers are waiting, what is the flow rate?

60 passengers per hour, because demand exceeds capacity.

What is the utilization of the metal detector?

60 / 360 = 16.7%

The metal detector is utilized at approximately 16.7%.

47. What is the cycle time of the process?

1 hour / 60 passenger = 1 minute per passenger

Quick Memory Rules

• Bottleneck = smallest capacity

• Flow rate = smaller of demand and capacity

• Utilization = flow rate divided by capacity

• Cycle time = 1 divided by flow rate

• Capacity-constrained = demand is too high

• Demand-constrained = capacity is greater than demand

• Upstream = beginning

• Downstream = end