Chapter 12: Process Control and Improvement:Root Cause Analysis (RCA) - 5 Whys, Fishbone Diagram

Abstract:

Root Cause Analysis (RCA) utilizes tools like the "5 Whys" and the "Fishbone diagram" to systematically identify the underlying causes of a problem by repeatedly asking "why" to reach the root issue, while the Fishbone diagram visually displays potential causes categorized by factors like people, process, materials, and environment, helping to brainstorm and analyze potential root causes. 

Key points about 5 Whys and Fishbone diagrams:

• 5 Whys:

  • A simple, iterative questioning technique where you repeatedly ask "why" about a problem to progressively uncover the root cause. 
  • Effective for straightforward problems where the causal chain is relatively short. 
  • Can be used alone or in conjunction with a Fishbone diagram. 
• Fishbone Diagram (Ishikawa diagram): 

  • A visual representation of potential causes categorized into different categories (like "people," "process," "materials," "environment") branching out from a central problem statement. 
  • Enables brainstorming and identifying multiple potential contributing factors to a problem. 
  • Useful for complex problems with many potential causes. 

How to use them together:

1. Define the problem: Clearly state the issue you want to analyze. 
2. Create a Fishbone diagram:
   • Draw the main "fishbone" with the problem statement at the head. 
   • Identify relevant categories (e.g., people, process, materials, environment) as branches. 
   • Brainstorm potential causes within each category and add them as sub-branches. 
3. Apply the 5 Whys:
   • For each potential cause on the Fishbone diagram, repeatedly ask "why" until you reach the root cause. 
   • Document the "why" answers on the diagram to visually map the causal chain. 

Benefits of using 5 Whys and Fishbone diagrams

• Systematic approach:

  Helps to identify the underlying root causes of a problem rather than just addressing symptoms. 
• Collaborative problem-solving:

  Encourages team participation and brainstorming to identify potential causes. 
• Visual representation:

  The Fishbone diagram provides a clear visual overview of the problem and its potential causes. 

Keywords:

Process Control and Improvement, Root cause analysis (RCA) - 5 Whys, Fishbone diagram

Learning Outcomes

After undergoing this article you will be able to understand the followings in details

Process Control and Improvement, 

Root cause analysis (RCA) - 5 Whys, 

Fishbone diagram

So let's explore chapter 12

Chapter 12: Process Control and Improvement

Root Cause Analysis (RCA) – 5 Whys, Fishbone Diagram

12.1 Introduction

Process control and improvement are critical aspects of quality management that ensure efficiency, reliability, and consistency in operations. One of the fundamental approaches to process improvement is Root Cause Analysis (RCA), which helps organizations identify, understand, and address the underlying causes of problems rather than merely treating the symptoms.

Two widely used RCA tools are:

• The 5 Whys – A simple, iterative questioning technique that helps drill down to the root cause of a problem.
• The Fishbone Diagram (Ishikawa Diagram) – A structured tool that categorizes potential causes into different areas to systematically analyze the root cause.

This chapter discusses these tools in detail, their implementation, benefits, and real-world applications in process control and improvement.

---

12.2 Root Cause Analysis (RCA)

Root Cause Analysis (RCA) is a systematic approach to identifying the fundamental reason behind a problem. Instead of addressing surface-level symptoms, RCA digs deeper into the root cause to prevent recurrence.

12.2.1 Steps in RCA

1. Define the Problem – Clearly describe the issue, including its impact, occurrence, and scope.
2. Collect Data – Gather relevant information, including observations, process records, and employee feedback.
3. Identify Potential Causes – Use structured techniques like the 5 Whys or Fishbone Diagram to explore possible root causes.
4. Determine the Root Cause – Verify and validate the true cause of the problem through testing, experiments, or further analysis.
5. Develop and Implement Solutions – Create corrective actions that address the root cause and prevent recurrence.
6. Monitor and Review – Assess the effectiveness of the solution and make adjustments if needed.

---

12.3 The 5 Whys Technique

The 5 Whys is a simple but effective RCA tool that involves repeatedly asking "Why?" to trace the cause of a problem back to its root.

12.3.1 How to Apply the 5 Whys

1. State the Problem Clearly – Define the issue that needs investigation.
2. Ask "Why?" – Identify the direct cause of the problem.
3. Continue Asking "Why?" – Repeat the process until you uncover the fundamental reason.
4. Stop When the Root Cause is Found – Usually, five iterations are sufficient, but it can be more or fewer.
5. Develop a Corrective Action – Implement solutions to address the root cause and prevent recurrence.

12.3.2 Example of the 5 Whys

Problem: A machine in a manufacturing plant stopped working.

1. Why did the machine stop?
   → Because the motor overheated.
2. Why did the motor overheat?
   → Because the lubrication system failed.
3. Why did the lubrication system fail?
   → Because the oil pump was not functioning.
4. Why was the oil pump not functioning?
   → Because the filter was clogged.
5. Why was the filter clogged?
   → Because it was not maintained regularly.

Root Cause: Lack of preventive maintenance led to a clogged filter.

Solution: Implement a preventive maintenance schedule.

12.3.3 Benefits of the 5 Whys

• Simple and easy to use.
• Helps identify the root cause quickly.
• Encourages critical thinking and problem-solving.
• Prevents recurrence of the issue.

---

12.4 The Fishbone Diagram (Ishikawa Diagram)

The Fishbone Diagram, also known as the Ishikawa Diagram or Cause-and-Effect Diagram, is a visual tool that categorizes potential causes of a problem into major areas.

12.4.1 How to Construct a Fishbone Diagram

1. Define the Problem (Effect) – Write the problem at the right-hand side of the diagram (the fish’s “head”).
2. Identify Major Cause Categories – Draw branches from the main line, representing different factors that contribute to the problem.
3. Brainstorm Causes – List potential causes under each category using brainstorming techniques.
4. Analyze the Diagram – Identify the most likely root cause by evaluating each factor.
5. Develop Corrective Actions – Implement solutions to eliminate the root cause.

12.4.2 Common Cause Categories in a Fishbone Diagram

• Manufacturing (6Ms)

  • Machine
  • Method
  • Material
  • Manpower
  • Measurement
  • Environment

• Service Industry (4Ps)

  • People
  • Processes
  • Policies
  • Place

• Software Industry (5Ms & 1E)

  • Manpower
  • Machine
  • Method
  • Material
  • Measurement
  • Environment

12.4.3 Example of a Fishbone Diagram

Problem: High defect rate in product assembly.

Cause Category	Potential Causes
Machine	Old equipment, improper calibration
Method	Inefficient process, incorrect assembly steps
Material	Defective raw materials, supplier quality issues
Manpower	Lack of training, human errors
Measurement	Inconsistent inspection, inaccurate tools
Environment	Poor lighting, excessive humidity

By analyzing the diagram, the company may find that defective raw materials from a supplier are the primary cause, leading to corrective action.

12.4.4 Benefits of the Fishbone Diagram

• Provides a structured way to analyze problems.
• Encourages team collaboration and brainstorming.
• Identifies multiple potential causes in one view.
• Helps prioritize corrective actions.

---

12.5 Comparison: 5 Whys vs. Fishbone Diagram

Feature	5 Whys	Fishbone Diagram
Purpose	Identifies root cause by iterative questioning	Categorizes and visualizes potential causes
Complexity	Simple, direct approach	More structured, requires brainstorming
Best for	Straightforward problems	Complex, multi-factor problems
Visual Representation	None (Q&A format)	Diagrammatic

The 5 Whys is best suited for simpler issues, while the Fishbone Diagram is ideal for more complex problems that require deeper analysis.

---

12.6 Case Study: Applying RCA Tools in a Manufacturing Plant

Problem Statement:

A car manufacturing company noticed an increase in defective engine parts.

Step 1: Using the 5 Whys

1. Why are engine parts defective?
   → Because they do not fit properly.
2. Why do they not fit properly?
   → Because they are slightly oversized.
3. Why are they oversized?
   → Because the cutting machine settings are incorrect.
4. Why are the machine settings incorrect?
   → Because the calibration process was skipped.
5. Why was the calibration skipped?
   → Because the maintenance team was unaware of the schedule.

Root Cause: Lack of communication and training in the maintenance team.

Step 2: Using the Fishbone Diagram

The company also created a Fishbone Diagram and found that apart from calibration issues, raw material inconsistencies and operator errors were additional contributing factors.

Step 3: Solution Implementation

• Established a training program for maintenance staff.
• Implemented automated calibration alerts.
• Reviewed supplier quality control for raw materials.

As a result, defect rates decreased by 30% within six months.

---

12.7 Conclusion

Root Cause Analysis (RCA) is a powerful approach to process control and improvement. The 5 Whys technique helps in quickly identifying the root cause through iterative questioning, while the Fishbone Diagram provides a structured visualization of potential causes. Both tools are essential for organizations seeking to improve quality, enhance efficiency, and reduce recurring problems.

By effectively applying RCA techniques, businesses can ensure long-term solutions rather than temporary fixes, leading to continuous process improvement and better overall performance.