Page 372 - The Toyota Way Fieldbook

346 THE TOYOTA WAY FIELDBOOK

Continuing with the causal analysis (Five-Why) process in this example
revealed the chain in Figure 15-4. Follow the bold text chain to the root cause in
the outlined box.
Toyota uses this process of continually narrowing, isolating (using the 80/20
rule), and focusing efforts on the items that will provide the greatest benefit.
Continuing to dig until the root causes are discovered also provides causes that
are both easier to improve and, when improved, will solve the original problem.
We can think of it as a funnel as shown in Figure 15-5.

Problem statement: The fabrication units per hour is below goal.
Why?
We are not able to make enough parts each hour
Why?
We are losing production opportunities
Why? Why?
Losing time Losing parts (scrap)
Why? Why? (Not most significant)
Cycle time losses Process not running
Why?
Loading the machine takes too long
Why?
Operator walks 5 feet for material (Root Cause)
Figure 15-4. Final pass Five-Why analysis

LARGE PROBLEM

Many Possible Causes

Most Likely Causes

Point of Cause

Five-Why Process

Root Causes

Figure 15-5. The narrowing and focusing process

Seeking Problem Causes That Are Solvable

During any process of analysis there will be a tendency to jump to predeter-
mined causes. Predetermined conclusions are often based on issues that are not