Prelim 1 – Module 2

Question 1

Capacity

Answer 1

Output per unit time when fully busy, can refer to a single station, work area, or entire process

Question 2

Throughput

Answer 2

Capacity for the entire process. This is the long-run average output per unit time.

Question 3

Bottleneck

Answer 3

The resource that limits production. It determines the cycle time of the entire system.

Question 4

Cycle Time (CT)

Answer 4

CT = 1/Capacity
Average time between completions of successive units for
- the entire system (think about a bell ringing upon each completion)
- an entire work area (i.e., group of workers doing same job), or
- a single work
- often convert units

Question 5

Capacity Utilization

Answer 5

actual output rate/capacity
can refer to a single station, work area, or entire process

Question 6

Rush Order Flow Time

Answer 6

The minimum (i.e., completion time minus entry time) to go through the system without any waiting.

Question 7

Total Direct Labour Content

Answer 7

Sum of all the operation times

Question 8

Direct Labour Utilization

Answer 8

What percent of the time are workers actually contributing value?
= total direct labour content/(process cycle time)(# of workers)

Question 9

Throughput Time

Answer 9

How long does it take to complete a process from time of arrival to time of exit? (including wait time) aka “sojourn time”

Question 10

Why do bottlenecks exist?

Answer 10

Inefficient process, too few resources, excess demand, unbalanced workload

Question 11

What can we do about bottlenecks?

Answer 11

Change the process at the bottleneck, add resources, control demand, shift resources

Question 12

Serial

Answer 12

Customer goes to one station and then the next
Capacity λ1 -> Capacity λ2
Has the same throughput as capacity min(λ1, λ2)

Question 13

Parallel

Answer 13

Customer is “served” by both simultaneously, and needs both to be done before moving on; e.g., body screening and luggage screening in airport security line
Has the same throughput as Capacity min(λ1, λ2)
Diagram: Capacity λ1 over Capacity λ2

Question 14

Multiple Servers

Answer 14

Customers can go to either
Has the same throughput as Capacity λ1+2λ
Diagram: Capacity 1λ over Capacity 2λ with a box around both

Question 15

Strategy to solve

Answer 15

Convert everything to a rate = completions/unit of time

Question 16

What does the process capacity calculation tell us?

Answer 16

Average completion rate with - a “fully loaded” system (i.e., infinite customers)
- note that the completion rate may vary over the short term

Question 17

What does the process capacity not necessarily tell us?

Answer 17

• throughput time
• average number of customers in the system

Question 18

Theory of Constraints

Answer 18

Core idea: every process has a single constraint that limits total process throughput.
Corollary: improving non-constraints will not provide significant benefits.

Question 19

5 focusing steps and meaning

Answer 19

1. Identify: determine the current constraint
2. Exploit: make quick improvements to that constraint’s capacity
3. Subordinate: review other activities and re-align to support the constraint
4. Elevate: invest in more substantial improvements to the constraint
5. Repeat: go back to step 1 once previous constraint is no longer a constraint

Question 20

Fix the Mix to Improve Throughput

Answer 20

Some processes have customers of different “classes”.
If we don’t have the right mix of servers, throughput could suffer.
We need to know: customer mix, total resource budget ($, SF, # seats), and amount of resources needed for each type of server