Understanding defect analysis using 8D method

Understanding defect analysis using 8D method

8 D -Eight disciplines problem solving Method developed at Ford Motor Company. Its purpose is to identify, correct, and eliminate recurring problems. It establishes a permanent corrective action based on statistical analysis of the problem and on the origin of the problem by determining the root causes.

 8D Follow the logic of the PDCA cycle.

Understanding defect analysis using 8D method

8D Analysis structure

D1- Team Formation

D2- Problem Definition

• 5W2H
• Problem Description

D3- Developing Interim Containment Actions

D4- Identifying & Verifying Root Cause

• Identifying possible cause of problem using Fish bone diagram
• Cause Validation
• Why –Why Analysis

D5- Identify Permanent corrective action plan

D6- Implementing & Validating the Permanent Corrective Action (PCA)

D7- Establishing Preventive Actions

• Lesson Learned [Horizontal Deployment if any.]
• Review the documents / systems where applicable

D8- Congratulate your Team 

Lets understand each Discipline one by one.

D1:- Team Formation

Team formation, we have to make CFT to work on the defect analysis. This team will be responsible for simulation, analysis, case study, measurement and decision making and deployment of action over the defect prevention. 

Here in 8D report we will write team name in Table.

D2:- Problem Definition

In 8D analysis report we will divide this in 2 section, 

• Problem Definition table
• 5W2H table

Problem definition table-

5W2H Table-

In this table we try to find out answer from 5 W question and 2 How question.

Questions in 5W2H is expect from What, Why, Where, When, Who, How, How much?

5W2H table is as below-

D3:- Developing Interim containment Action

Temporary actions to contain the problem and “fix” until permanent correction is in place. Here we explain quick action taken after receiving defect information. In interim containment Action we take countermeasure for short period, temporary. Purpose of interim action plan is to prevent current supply from defect, this action is for verification of current situation. It is like we verify current stock, and supply with OK sticker. 

Here OK parts checked 597 at customer end, marked with batch code. Temporary action taken here is Green mark application on OK parts, so on customer line it can be traced as OK/Verified by vendor.

D4: Identifying and verifying root cause

In this we try to find out root cause of problem. This discipline is divided into 3 section.

1. Identifying possible cause of problem using Fish bone diagram
2. Cause Validation
3. Finding root cause using Why-Why analysis

1. Fish Bone diagram:- With this we try to identify possible cause of problem by using 6M, Man, machine, method, material, measurement & Mother nature.

Here we divide all 6M with their requirements, check is there any gap. 

2. Cause Validation:- Based on the team’s discussions. We begin to complete the Root Cause Action Plan to verify and validate the root causes and test the escape point. 

In validation we do simulation over some possible cause of problem. We want to make sure that the problem is because of a certain root cause. Result of the validation is listed in table. Or a separate cause validation report can be share with 8D report. 

We Document this on the Action Item Table-

3. Why-Why Analysis:- By Why Why analysis we try to reach at root causes. So far we have done simulation over possible causes of problem, now we want to sure which cause is root cause, so we do Why why analysis. 

In this process we describe problem, next ask why this happen , then question for answer of first question will become next Why, and so on.  We do this until we reach up-to final result. That answer will be root cause.

Here why why analysis is done over two condition, Why why for occurrences and Why-why for outflow. Countermeasure to be given for both root causes of occurrence and outflow. 

D5: Identifying Permanent corrective Action plan

Here we will give details about solutions that address and correct the root cause. Solutions determined to be the best of all the alternatives. Corrective action here will be countermeasure for the defect that will solve the customer problem. 

Corrective action to be taken for both occurrence and outflow of defect. Details of action taken can be explained in separate sheet of 8D report.

Document and verify the Permanent Corrective Action (PCA) in the Action Item Table.

D6: Implementing & Validating the Permanent Corrective Action (PCA)

Implement and validate to ensure that corrective action does “what it is supposed to do.” Detect any undesirable side effects. Document this on the Action Item Table. Return to root cause analysis, if necessary.

Here you can add validation report, test report after implementing corrective action. 

We validate this permanent corrective action by doing SPC, MSA and checking same method on other machine, doing trial on big lot, check the variation, if this found OK. We can next move to effective of this permanent corrective action. For that we need at least 3 months, and we expect in those 3 months, no single defect report from customer end after PCA implementation. 

Details report of effectiveness of PCA can be prepared separately. 

D7: Establishing Preventive Actions

We determine what improvements in systems and processes would prevent problem from recurring. Ensure that corrective action remains in place and successful.

While establishing preventive actions we have to take care of 2 things:-

• Lesson Learned [Horizontal Deployment if any.]
• Review the documents / systems where applicable

From lesson learn we check is there any chance of reoccurrence of this defect in other parts, other machine or in future development parts. So horizon deployment of the countermeasure is expected from customer side.

After preventive action establishing we review our following internal documents:

1. PFMEA

2. Control plan

3. WI

4. Process check sheets.

This countermeasure to be record in above mention documents for future analysis or action. Bacuse this study can be used for new development, so advance corrective action can be taken. 

D8: Congratulate Your Team 

In this last discipline we congratulates our team members who help to establish the permanent corrective/preventive action. 

In congratulation we will write the name along with their mail id/Designations. 

Who prepared the report, who did trial and who approved it. 

This was all about 8D method of defect analysis.  

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