TOYOTA INDUSTRIAL EQUIPMENT MFG., INC.
QUALITY ASSURANCE CORRECTIVE & PREVENTIVE ACTION 4.14
Date Issued:
Page Number:
6/11/04 Revision:
1 of 5 Document Number:
B WKIN05614 SECTION:
SUBJECT:
Level 3 Instruction
Fault Tree Analysis (PDCA-FTA)
PURPOSE:
To describe and communicate the recommended use of a PDCA-Fault Tree Analysis.
RESPONSIBILITY: Quality Assurance Department.
PROCEDURE / PROCESS: PDCA-FTA Fault Tree Analysis (FORM01018):
TOYOTA INDUSTRIAL EQUIPMENT MFG., INC.
QUALITY ASSURANCE CORRECTIVE & PREVENTIVE ACTION 4.14
Date Issued:
Page Number:
6/11/04
2 of 5
Revision:
Document Number:
B WKIN05614
Fault Tree Analysis (PDCA-FTA) description: The PDCA-FTA is a graphical analyzing technique tool used to find the causes of faults or problems. A PDCA-FTA can be used for any problem. Common uses are problems identified from AR, Tech Reports, Warranty Claims, TIEM Material Reports, and Supplier Material Reports and Departmental issues. The PDCA-FTA uses logic and facts to narrow down the causes of a problem to the root causes. Implementing effective countermeasures for root causes will eliminate reoccurrence of the problem. The PDCA-FTA encomes the PDCA problem solving technique. Fault Tree Analysis :
Problem or Fault= the difference between the standard situation and the current situation Possible causes = the basic & logical situations that would directly cause the problem to occur. These are determined by brainstorming. o 4Ms & 1E = Man, Method, Machine, Material & Environment (categories used to help brainstorm possible causes). Cause = facts that are determined to directly cause the previous cause to happen. Investigation summary = summary of the facts to be the root cause for each line Countermeasure = action taken to address the root cause for a line of investigation Target Implementation Date = Target date for Countermeasure to be completed. PIC = Person in Charge of seeing Countermeasure is implemented by target completion date. Line of investigation = causes on the same line leading to a root cause and countermeasure
Fault Tree Analysis (PDCA-FTA) recommended use: 1. Clarify the fault or problem. The problem is the difference between the standard situation and the actual situation. Note: Only one problem can be addressed per FTA. 2. Complete the “History” graph to show how many times & how often this problem has occurred. 3. Determine possible causes (using 4Ms & 1E). Each possible cause begins its own line of investigation that will result in its own root cause(s) and countermeasure(s). 4. Investigate possible causes and record why they are happening in the “Cause” box. Do not record opinions, or guesses that could be causes, this can lead to ineffective countermeasures. Only record facts determined through investigation. 5. Possible causes and causes can split to more than one box and start additional lines of investigation. 6. Continue each line of investigation until it cannot be investigated further or is not required to investigate further. 7. Summarize each line of investigation to be the root cause for its line. 8. Determine countermeasures for each root cause along with Target Implementation Date & PIC. 9. Track the implemented countermeasures using the bottom two graphs to determine effectiveness. 10. List the steps that were taken to standardize the countermeasures in the Follow-Up/Result box (Revised Work Instructions, Training, Pokayoke etc.).
QUALITY ASSURANCE CORRECTIVE & PREVENTIVE ACTION 4.14
TOYOTA INDUSTRIAL EQUIPMENT MFG., INC.
Date Issued:
Page Number:
6/11/04
3 of 5
Revision:
Document Number:
B WKIN05614
Fault Tree Analysis (FTA) logical symbols:
AND symbol =
(Next cause)
(Previous cause)
B
The correct usage of the AND Symbol: The previous cause A can exist only when the next cause B and C co-exist.
A C Meaning, taking countermeasures for only one (B or C) suffices in preventing the previous cause from occurring.
AND Symbol
OR symbol = (Next cause) (Previous cause)
B
A
The correct usage of the OR Symbol: The previous cause A can exist when either of the next causes B or C exists.
C OR Symbol
Therefore, countermeasures should be taken for both the B and C causes to eliminate the previous cause from occurring.
TOYOTA INDUSTRIAL EQUIPMENT MFG., INC.
QUALITY ASSURANCE CORRECTIVE & PREVENTIVE ACTION 4.14
Date Issued:
Page Number:
6/11/04
4 of 5
Revision:
Document Number:
B WKIN05614
Line usage.
Incorrect usage. B
C
A
Incorrect
Correct usage.
Should not split a line into multiple lines in the middle.
D
B
C
A
Correct
D
Lines should start and end at a cause or a logical symbol.
TOYOTA INDUSTRIAL EQUIPMENT MFG., INC.
QUALITY ASSURANCE CORRECTIVE & PREVENTIVE ACTION 4.14
Date Issued:
Page Number:
6/11/04
5 of 5
Revision:
Document Number:
B WKIN05614
APPLICABLE FORMS AND REFERENCES: ISO9001:2000 Quality management systems – Requirements 16.01 Records Retention FORM01018 PDCA-FTA
RECORDS: Specific retention and responsibility requirements are maintained on the info card for each document located in MasterControl per the instructions included in PROC00012 (QA Document and Data Control) and PROC00030 (Records Retention) for the following records: FORM01018
PDCA-FTA
REVISION CHANGE: Revision Date 3/2/06 11/8/06
Comments Revised entire document from the basic FTA to the PDCA-FTA form. Replaced the term “factor” with actual term of what is required for each area to help in the understanding of the PDAC/FTA process..