International Journal of Conceptions on Mechanical and Civil Engineering Vol. 1, Issue. 1, Dec’ 2013; ISSN: 2357 – 2760

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Potential failure mode and effect analysis (PFMEA) – A case study on valve body matching

Senthil Kumar R, Rajeshwaralu M K, Subramaniam P and Rajkumar A Dept. of Mechanical Engineering,

Coimbatore Institute of Technology, Coimbatore, India.

{rsenthilkumar1990, mkrajeshwaralu1992, spsubbu91, raju2raju52}@gmail.com

Abstract— Products and their components are designed to perform certain specific functions. Every product has some design specifications which ensure its functionality aspects. The task of manufacturing is to produce components such that they meet design specifications. However, these design specifications cannot be achieved as such as they are restricted by some constraints namely process variations. These process variations can be identified and rectified through Failure Mode Effects Analysis (FMEA). This FMEA is the third phase of Product Development Process Model in Advanced Product Quality Planning (APQP). FMEA is a procedure in product development and operational management for analysis of potential failure modes of within a system in which it could fail. PPFMEA is a process is used to identify the causes, effects and its control measures are listed as per the ISO/TS 16949:2009 in a systematic manner indicated in 7.3.3.2.* The chosen criterion for our work is “Process Potential Failure Mode Effects Analysis (PPFMEA) - used to analyze manufacturing and assembly processes. The proposed case study involved the study of PPFMEA of Valve Body Machining process at FITZOL CADET. The PPFMEA of this process supported manufacturing process development in reducing the risk of failures. This involved the identifying of process variables on which to focus process controls for occurrence reduction or increased detection of failure conditions and by enabling the establishment of a priority system for preventive/corrective action, and controls. The work mainly aimed at the following - Process Steps are taken from Process Flow Diagram (PFD), Potential Failure Modes taken from Dimensional Report, Potential Effects of Failure got from pervious complaints and customer feedback, potential Cause of failure got from cause and effect analysis, current Process control Prevention & Detection through the Daily In process check sheets, Severity, Occurrence and Detection values taken from Standard FMEA tables.

Keywords- Process Variation, Risk priority number (RPN),Severity Occurrence Detection (SOD), Process Characteristic Identification, Operation Flow

I. INTRODUCTION Process potential failure mode and effect analysis

(PPFMEA) study on valve body machining operation gives the brief study about the FMEA. It would help to improve the process and reduce the failure occurrences in the machining operation of the Valve body. It gave the basic requirements of Advance Product Quality Planning (APQP) and PPAP needs.

This work gives an opportunity to know and refer the some of the classes of ISO/TS 16949.And also know about the Statistical Quality control tools(SQC) and Quality Circle tools(7QC Tools) etc.

II. CONCEPTS Every process and product has its own process and product

characteristics like Machining parameters and dimensions respectively. During operations due to some unavoidable reasons some of the process parameters and some of the product dimensions get deviated, it is unpredictable. To control the process variation and to maintain the Product dimensions within the specification and control limits.

To control all the variation of the process and product characteristics, an organisation called Automotive Industries Action Group (AIAG) is an association of North American companies as Ford, GM & Chrysler in 1996 created QS-9000 produced the common standard called Potential Failure Mode and Effect Analysis (PFMEA).

Now a days in all ISO and TS companies and MNC Companies the FMEA is essential from its development stage itself. The major contribution of FMEA is to identify the major product characteristics and process characteristics and reduce the failure occurrences and to eliminate the causes in a systematic manner.

III. FMEA FMEA is a procedure in product development and

operational management for analysis of potential failure modes of within a system in which it could fail.

PPFMEA is a process is used to identify the causes, effects and its control measures are listed as per the ISO/TS 16949:2009 in a systematic manner indicated in 7.3.3.2.[6]

We are planning to conduct a study about the Machining process of Valve Body (Braking System).

A. Special Characteristics The organization shall identify special characteristics [see

7.3.3 d)] and

include all special characteristics in the control plan,

International Journal of Conceptions on Mechanical and Civil Engineering Vol. 1, Issue. 1, Dec’ 2013; ISSN: 2357 – 2760

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comply with customer-specified definitions and symbols, and

Identify process control documents including drawings, FMEAs, control plans, and operator instructions with the customer’s special characteristic symbol or the organization’s equivalent symbol or notation to include those process steps that affect special characteristics.

Note: Special characteristics can include product characteristics and process parameters.

B. Manufacturing Process Design Output The manufacturing process design output shall be

expressed in terms that can be verified against manufacturing process design input requirements and validated. The manufacturing process design output shall include

specifications and drawings, manufacturing process flow chart/layout, manufacturing process FMEAs, control plan (see 7.5.1.1), work instructions, process approval acceptance criteria, data for quality, reliability, maintainability and

measurability, results of error-proofing activities, as appropriate,

Fig. 1 Product Development Process Model

IV. TYPES OF FMEA

A. System FMEA: Used to analyze systems and subsystems in the early

concept and Design stages Focuses on potential failure modes associated with the

functions and interfaces of a system caused by Design. B. Design FMEA: Used to analyze Products before they are released to

production Focuses on potential failure modes associated with the

functions of the product caused by Design. C. Process FMEA: Used to analyze Manufacturing and Assembly processes

Focuses on potential failure modes associated with the functions of a process caused by Design and Operation.

V. OBJECTIVES OF FMEA The PPFMEA, Supports manufacturing process

development in reducing the risk of failures by,

-Identifying process variables on which to focus process controls for occurrence reduction or increased detection of failure conditions

-Enabling the establishment of a priority system for preventive/ corrective action.

Improved Process Robust Control Improved Process Control Identify and Minimize RiskPFMEA Understand how to ensure the development and

implementation of the design and process meets all customer and program requirements.

Understand the activities involved in the realization of new products and processes.

Understand the role of FMEAs Competency in the development of FMEAs Understand the linkages between designing the product

and developing the processes

Fig. 2: System Diagram

International Journal of Conceptions on Mechanical and Civil Engineering Vol. 1, Issue. 1, Dec’ 2013; ISSN: 2357 – 2760

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Fig. 3: Component – Valve body

Fig. 4: Component Drawing

Fig.5 Process flow diagram

Fig.6 Dimensional Inspection Report

Realize that product and process design and development should focus on Robustness and error prevention than detection

VI. PRODUCT DETAILS Product name : Valve Body (Machining) Material : Aluminium Application : Automobiles (Used in Hand Brake system) Intermediate Customer : Indo shell Ltd End Customer : Telco Weight : 150 grms Annual Volume : 2.64 Lacks

VII. PRODUCT PARAMETERS Height – 16 ± 0.3 Total Height-53.35 ± 0.15 Depth- 55.7 ± 0.1

Fig.7 Process Capability for product characteristics

International Journal of Conceptions on Mechanical and Civil Engineering Vol. 1, Issue. 1, Dec’ 2013; ISSN: 2357 – 2760

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The Ppk & Pp Value lies between these limits The Process is Capable. Critical Dimensions ≥ 1.67; Major Dimensions ≥ 1.33;Minor Dimensions ≥ 1.0.

VIII. RISK EVALUATION

A. Risk Priority Number (RPN) RPN is used to rank relative risk associated with specific

failure modes Corrective action is taken thereafter to reduce the RPN,as

appropriate.

Note: Preventive Controls do not affect the detection value, only Occurrence Value.

Fig.8 Standard PFMEA Format

IX. PFMEA FOR VALVE BODY MACHINING OPERATION

Fig.9 Valve body Operation- PFMEA

X. CUSTOMER COMPLAINT DETAILS

Dimension 3.60 ± 0.1 measured at customer end and found as 3.90 over size. The complaint was intimated to supplier through Flash report.

The supplier (FITZOL CADET) gave their corrective action report through the 8D approach format. A thorough revision of the FMEA in regard with the customer complaints has been made – which can ensure for the avoidance of the non conformities during customer process or product audit. This can eliminate the customer dissatisfaction.

XI. UPDATED FMEA FOR VALVE BODE WITH CUSTOMER COMPLAINTS

XII. RESULT AND DISCUSSIONS A thorough study on the PFMEA and its requirements. A thorough study on Valve Body PFMEA (4th Revision as

per the ISO/TS 16949 standards.) Updating the pervious customer complaints in the 4th

Revision of FMEA

REFERENCES [1] ISO/TS 16949:2009 Manual [2] OMNEX Training Manual [3] The Engineer’s Hand Book – R.S. Arora [4] Failure Mode and Effect Analysis: FMEA from theory to Execution by

D.H.Stamatis.Publication JUNE 2003, Edition 2Rev. [5] The Basics of FMEA by Robin E.McDermott, Raymond

J.Mikulak,Michael R.Beauregard.SEP 30,1992. [6] ISO/TS 16949:2009 MANUAL