FMEA IMPLEMENTATION IN A FOUNDRY IN BANGALORE TO IMPROVE .

Int. J. Mech. Eng. & Rob. Res. 2012Piyush Kumar Pareek et al., 2012ISSN 2278 – 0149 www.ijmerr.comVol. 1, No. 2, July 2012 2012 IJMERR. All Rights ReservedResearch PaperFMEA IMPLEMENTATION IN A FOUNDRY INBANGALORE TO IMPROVE QUALITY ANDRELIABILITYPiyush Kumar Pareek1*, Trupti V Nandikolmath1 and Praveen Gowda1*Corresponding Author: Piyush Kumar Pareek, piyushpareek88@gmail.comFailure Mode and Effect Analysis (FMEA) is a technique to identify and prioritize potential failuresof a process. This paper reports the description of FMEA methodology and its implementation ina foundry in reducing rejections of bushes. It is used as a tool to assure products quality and asa mean to improve operational performance of the process. The work was developed in anIndian foundry, in co-operation with part of the internal staff chosen as FMEA team membersand was focused on the study of core making process. The problems identified in the varioussteps of core making process contributing for high rejection are studied and analyzed in termsof RPN to prioritize the attention for each of the problem. The monetary loss due to core rejectionis considered as measure of risk.Keywords: Core, FMEA, Failure mode, Risk priority numberINTRODUCTIONBasic Terms UsedProcess FMEA is used to solve problems dueto manufacturing processes. It starts with aprocess flow chart that shows each of themanufacturing steps of a product. The potentialfailure modes and potential causes for eachof the process steps are identified, followedby the effects of failures on the product andproduct end users. The risks of these effectsare then assessed accordingly as shown inFigure 1 (Xu et al., 2002).1Failure: The loss of an intended function of adevice under stated conditions.Failure Mode: The manner by which a failureis observed; it generally describes the way thefailure occurs.Failure Effect: Immediate consequences ofa failure on operation, function or functionality,or status of some item.Department of Industrial Engineering & Management, DSCE, Bangalore, Karnataka 560078, India.81

Int. J. Mech. Eng. & Rob. Res. 2012Piyush Kumar Pareek et al., 2012Figure 1: Failure Mode and Effect Analysis CycleActions CheckRisk Priority Number (RPN) SEV OCCUR DETECStep 4: Detection Number(DETEC)Step 1: Detect a FailureModeFailure Mode and Effect AnalysisStep 2: Severity Number(SEV)Step 3: Probability Number(OCCUR)Indenture Levels: An identifier for item iscomplexity. Complexity increases as levelsare closer to one.careful knowledge of the process, thereforethe same is studied by using process flowchart. The first phase of the work was tocollect the core rejection data, informationabout cores, production lines and coremaking machines through visits to theproduction plant. Percent average Corerejection of three months is gathered fromQC reports and the most common problemsdue to which cores are rejected are notedbefore the start of the study. Once FMEAteam obtained all the information availableabout the problems of core rejection orpotential failures of the core making process,it moved the operative phase of riskevaluation through definition of the FMEAform. The form used in this work is basedon the reference manual (Chrysler/Ford/General Motors Task Force).Local Effect: The failure effect as it appliesto the item under analysis.Next Higher Level Effect: The failure effectas it applies at the next higher indenture level.End Effect: The failure effect is at the highestindenture level or total system.Failure Cause: Defects in design, process,quality, or part application, which are theunderlying cause of the failure or which initiatea process which leads to failure.Severity: The consequences of a failuremode are severity. Severity considers theworst potential consequence of a failure,determined by the degree of injury, propertydamage, or system damage that couldultimately occur.DATA COLLECTIONIt has been found that shrinkage is thedefect which is occuring more and needs tobe eliminated as shown in Figure 2.Before design and implementation of FMEAto core making process it is required to haveThe first step of FMEA begins withidentifying the process as shown in Table 1.82

Int. J. Mech. Eng. & Rob. Res. 2012Piyush Kumar Pareek et al., 2012RM %Figure 2: Defect Mapping of 0080 Bush10090807060504030201000080 Foundry RM % – February 201212010080604020ShrinkageDrossCas CadingDefectsBlow HoleCrack0Table 1: Process Flow Chart of 0080 ransportDelay12Not OK34OK56For Disposal7OK83Description ofActivitiesProcedure or SpecificationPreparingDies andHeatingof DiesAs per Regular Heating with Lpg Bumer/Nextto Hot MetalChargeMakeupandMelting ofChargeWork Instruction for Melting and Pouring ofHTB-16MetalurgicalAnalysisof theAlloyWork Instruction for Chemical Analysis forHTB-16Pouring oftheCastingsWork Instruction for Pouring of HTB-16 SEC:24.0 and 28.0Fettling oftheCastingsChipp off Extra Projected Material with SmallHammerInspectionof theCastingsVisual InspectionMovementof the okCastingstoMachinesHopCasting ok Status “OK FOR NEXTOPERATION”

Int. J. Mech. Eng. & Rob. Res. 2012Piyush Kumar Pareek et al., 2012Then we founded out the potential failuremodes and its effects by brainstorming withpeople from Production and Quality departmentsof the company as shown in Table 2.Table 2: Analysing Failure ModesPotential Failure ModePotential Effect(s) of Failure1. Less die/core pins temp.Blow holes/cracks at serration lines2. More die/core pins temp.Shrinkage at inner diameter3. Sticking of casting on to the dieDie damage4. Composition and properties of the alloy out of specIngoting of melt/production plan affected5. Low hardnessRejection6. High hardnessRejection7. Improper solidification of castingDefective casting8. Improper solidification and gas entrapmentDefective castings9. Damages caused to castingDefective castingOccurrenceSeverityIn this step it is necessary to look at thecause of a failure mode and the number oftimes it occurs. This can be done by lookingat similar products or processes and thefailure modes that have been documentedfor them in the past. A failure cause is lookedupon as a design weakness. All the potentialcauses for a failure mode should beidentified and documented. Again thisshould be in technical terms. Examples ofcauses are: erroneous algorithms, excessivevoltage or improper operating conditions. Afailure mode is given an occurrence ranking(O), again 1-10. Actions need to bedetermined if the occurrence is high(meaning 4 for non-safety failure modesand 1 when the severity-number from step2 is 9 or 10). This step is called the detaileddevelopment section of the FMEA process.Occurrence also can be defined as %. If anon-safety issue happened less than 1%, wecan give 1 to it. It is based on your productand customer specification.Determine all failure modes based on thefunctional requirements and their effects.Examples of failure modes are: Electricalshort-circuiting, corrosion or deformation. Afailure mode in one component can lead to afailure mode in another component, thereforeeach failure mode should be listed in technicalterms and for function. Hereafter the ultimateeffect of each failure mode needs to beconsidered. A failure effect is defined as theresult of a failure mode on the function of thesystem as perceived by the user. In this way itis convenient to write these effects down interms of what the user might see orexperience. Examples of failure effects are:degraded performance, noise or even injuryto a user. Each effect is given a severitynumber (S) from 1 (no danger) to 10 (critical).These numbers help an engineer to prioritizethe failure modes and their effects. If thesensitivity of an effect has a number 9 or 10,actions are considered to change the designby eliminating the failure mode, if possible, or84

Int. J. Mech. Eng. & Rob. Res. 2012Piyush Kumar Pareek et al., 2012done it is easy to determine the areas ofgreatest concern. The failure modes that havethe highest RPN should be given the highestpriority for corrective action. This means it isnot always the failure modes with the highestseverity numbers that should be treated first.There could be less severe failures, but whichoccur more often and are less detectable. Afterthese values are allocated, recommendedactions with targets, responsibility and datesof implementation are noted. These actionscan include specific inspection, testing orquality procedures, redesign (such asselection of new components), adding moreredundancy and limiting environmentalstresses or operating range. Once the actionshave been implemented in the design/process,the new RPN should be checked, to confirmthe improvements. These tests are often putin graphs, for easy visualization. Whenever adesign or a process changes, an FMEA shouldbe updated (Stamatis, 1997).protecting the user from the effect. A severityrating of 9 or 10 is generally reserved for thoseeffects which would cause injury to a user orotherwise result in litigation.DetectionWhen appropriate actions are determined, itis necessary to test their efficiency. Inaddition, design verification is needed. Theproper inspection methods need to bechosen. First, an engineer should look at thecurrent controls of the system, that preventfailure modes from occurring or which detectthe failure before it reaches the customer.Hereafter one should identify testing, analysis,monitoring and other techniques that can beor have been used on similar systems todetect failures. From these controls anengineer can learn how likely it is for a failureto be identified or detected. Eachcombination from the previous 2 stepsreceives a detection number (D). This ranksthe ability of planned tests and inspections toremove defects or detect failure modes intime. The assigned detection numbermeasures the risk that the failure will escapedetection. A high detection number indicatesthat the chances are high that the failure willescape detection, or in other words, that thechances of detection are low.A few logical but important thoughts comein mind:Try to eliminate the failure mode (somefailures are more preventable than others). Minimize the severity of the failure. Reduce the occurrence of the failuremode.Risk Priority Number (RPN) Improve the detection.RPN play an important part in the choice of anaction against failure modes. They arethreshold values in the evaluation of theseactions. After ranking the severity, occurrenceand delectability the RPN can be easilycalculated by multiplying these three numbers:RPN S O D. This has to be done for theentire process and/or design. Once this isThen we calculated the severity, occurrenceand detection of the failure modes and finallycalculated the risk priority number as shownin Table 3.Then finally actions were suggested andreadings were calculated as depicted inTable 4.85