International Journal of Conceptions on Mechanical and Civil Engineering Vol. 1, Issue. 1, Dec’ 2013; ISSN: 2357 – 2760
38 | 1 3 3
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
39 | 1 3 3
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
40 | 1 3 3
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
41 | 1 3 3
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