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  • 1. International Journal of Industrial Engineering and Development (IJIERD), INTERNATIONAL JOURNAL 4,ResearchSeptember - December (2013),ISSN 0976 – OF INDUSTRIAL ENGINEERING 6979(Print), ISSN 0976 – 6987(Online) Volume Issue 3, © IAEME RESEARCH AND DEVELOPMENT (IJIERD) ISSN 0976 – 6979 (Print) ISSN 0976 – 6987 (Online) Volume 4, Issue 3, September - December (2013), pp. 01-12 © IAEME: www.iaeme.com/ijierd.asp Journal Impact Factor (2013): 5.1283 (Calculated by GISI) www.jifactor.com IJIERD ©IAEME A DETAILED STUDY ON PROCESS FAILURE MODE AND EFFECT ANALYSIS OF PUNCHING PROCESS J. Arun1, S. Pravin Kumar2, M. Venkatesh3, A.S. Giridharan4 1 UG Graduate, Department of Mechanical Engineering, Government College of Technology, Coimbatore. 2 UG Graduate, Department of Mechanical Engineering, Government College of Technology, Coimbatore. 3 UG Graduate, Department of Mechanical Engineering, Government College of Technology, Coimbatore. 4 UG Graduate, Department of Mechanical Engineering, Government College of Technology, Coimbatore. ABSTRACT An FMEA (Failure Mode and Effect Analysis) is a systematic method of identifying and preventing product and process problems before they occur. FMEAs are focused on preventing defects, enhancing safety, and increasing customer satisfaction. Ideally, FMEAs are conducted in the product design or process development stages, although conducting an FMEA on existing products and processes can also yield substantial benefits. FMEA is used in the manufacturing industry to improve production quality and productivity by reducing potential reliability problems early in the development cycle where it is easier to take actions to overcome these issues, thereby enhancing reliability through design. It is a method that evaluates possible failures in the system, design, process or service. In this paper, Failure mode and Effect Analysis is done on the process of Punching. A series of punching operation is done on various work pieces and the defects are found. Based on the evidence found, the ratings are given and risk priority number is given. Based on the RPN, the preventive measures are given. The FMEA is a proactive approach in solving potential failure modes. These works serve as a failure prevention guide for those who perform the punching operation and works towards effective punching operation. KEYWORDS: Failure Modes, Punching, Risk Priority Number, FMEA Table, Chipping. 1
  • 2. International Journal of Industrial Engineering Research and Development (IJIERD), ISSN 0976 – 6979(Print), ISSN 0976 – 6987(Online) Volume 4, Issue 3, September - December (2013), © IAEME 1. INTRODUCTION In today’s market, the expectancy of the customer towards high quality, reliable and cost effective products is really high. So this expectancy proves a burden for the manufactures as they strive to satisfy the customers with defect free, reliable product. So the manufacturers switch to a newer technique which helps them to achieve the expected standards. The challenge is to design a quality and reliability product early in the development cycle. Such challenges are met with latest techniques and strategies implemented in both the design and product manufacturing. One such technique is Failure Mode and Effect Analysis (FMEA). Failure Mode and Effect Analysis (FMEA) is used to identify potential failure modes, determine their effect on the operation of the product, and identify actions to mitigate the failures [1-2]. 1.1 FAILURE MODE & EFFECT ANALYSIS FMEA is a tool originated by SAE reliability engineers. It continues to be associated by many with reliability engineering. It analyzes potential effects caused by system elements ceasing to behave as intended. The purpose of FMEA is to identify possible failure modes of the system, evaluate their influences on system behavior and propose proper countermeasures to suppress these effects. FMEA enhances further improvisation of both the design and manufacturing processes in the future as it serves as a record of the current process in formations [4-5]. FMEA is an engineering technique used to identify, prioritize and alleviate potential problems from the system, design, or process before the problems are actualized (According to Omdahl, 1988). What does the term “Failure Modes” imply? Lots of definitions for this term can be obtained. According to the Automotive Industry Action Group (AIAG), a failure mode is “the way in which a product or process could fail to perform its desired function” (AIAG, 1995). Some sources define “failure mode” as a description of an undesired cause-effect chain of events (MIL-STD-1629A, 1994). Others define “failure mode” as a link in the cause-effect chain [3] (Stamatis, 1995: Humphries, 1994). To conclude with we consider the term failure mode as any errors or defects in a process, design, or item, especially those that affect the customer, and can be potential or actual. The term “Effect Analysis” also invites various definitions. The effect analysis is “the analysis of the outcome of the failure on the system, on the process and the service” (Stamatis, 1995: Humphries, 1994) [2-5]. To put it simply Effects analysis refers to studying the consequences of those failures. FMEA is a tool that allows us to: • • • • • Discover potential failures in a system, product or process Prioritize actions that decrease risk of failure Evaluate the system/design/processes from a new vantage point Guide design evaluation and improvement Troubleshoot and monitor the performance of systems 1.2 IMPORTANCE OF FMEA IN PUNCHING Punching process is a stamping or pressing type of metal removal process in which the product is formed by pressing the work between die [7]. The metal removal is by shearing force between the work and the die. Various components contribute to the accuracy, 2
  • 3. International Journal of Industrial Engineering Research and Development (IJIERD), ISSN 0976 – 6979(Print), ISSN 0976 – 6987(Online) Volume 4, Issue 3, September - December (2013), © IAEME reliability of the product. When these components are defective, this leads to the failure of the product. Some of the failures in the punching process are like Punch chipping, Slug jamming, Galling etc. [7]. These result in unfavorable consequences like failure of the system or production of inaccurate products. Hence it is essential to conduct a FMEA in this process so that the failure is avoided totally or reduced. Prior notification of these failures can prevent them by following control measures. 2. IMPLEMENTATION OF FMEA The purpose of performing an FMEA is to analyze the product's design characteristics relative to the planned manufacturing process and experiment design to ensure that the resultant product meets customer needs and expectations. When potential failure modes are identified, corrective action can be taken to eliminate them or to continually reduce a potential occurrence [3-4]. In FMEA, failures are prioritized according to how serious their consequences are, how frequently they occur and how easily they can be detected. Ideally, FMEA begins during the earliest conceptual stages of design and continues throughout the life of the product or service. Results can be used to identify high-vulnerability elements and to guide resource deployment for best benefit. An FMEA can be done any time in the system lifetime, from initial design onwards. The various steps in Process Failure and Effect Analysis are as follows • Reviewing the process • List the potential effects and modes of failure • Assign a severity rating • Assign an occurrence rating • Assign a detection rating • Calculate the risk priority number (RPN) for each mode of failure • Take action to eliminate or reduce the high-risk failure modes • Calculate the resulting RPN as the failure modes are reduced or eliminated [4]. 2.1 STEP 1: PROCESS REVIEW The blueprint (or engineering drawing) of the product and a detailed flowchart of the operation are reviewed. The process parameters of the conducted tests are as follows: Capacity : 60 Ton Maximum stroke : 6" Bed Area : 42" X 32" Speed : 40 Strokes per minute Floor to Bed : 33" Dimensions : 10'10" High, 8'6" RL, 6' FB Weight : 15,000 Lbs Tool used : Tungsten steel Work piece material : Silicon steel Several trials are to be conducted with the above mentioned parameters. 3
  • 4. International Journal of Industrial Engineering Research and Development (IJIERD), ISSN 0976 – 6979(Print), ISSN 0976 – 6987(Online) Volume 4, Issue 3, September - December (2013), © IAEME Fig 1: High Speed Press Fig 2: Defective product from punching process Burr formation Fig 3: Burr formation in the punched product 2.2 STEP 2: POTENTIAL EFFECTS & FAILURE MODES Based on the trials conducted the failures are listed. In this, previously recorded failures are also added. The effects of these failure modes are also tabulated. These failure modes and their effects are charted separately for the sake of calculating and assigning the ratings and risk priority numbers. With the failure modes listed on the FMEA Worksheet, each failure mode is reviewed and the potential effects of the failure should it occur are identified. For some of the failure modes, there is only one effect, while for other modes there may be several effects. This step must be thorough because this information will feed into the assignment of risk rankings for each of the failures. It is helpful to think of this step as an ifthen process: If the failure occurs, then what are the consequences [4]. 2.3 STEP 3: ASSIGN SEVERITY RATING The severity ranking is an estimation of how serious the effects would be if a given failure did occur. In some cases it is clear, because of past experience, how serious the problem would be. In other cases, it is necessary to estimate the severity based on the 4
  • 5. International Journal of Industrial Engineering Research and Development (IJIERD), ISSN 0976 – 6979(Print), ISSN 0976 – 6987(Online) Volume 4, Issue 3, September - December (2013), © IAEME knowledge of the process. There could be other factors to consider (contributors to the overall severity of the event being analyzed) [4]. Calculating the severity levels provides for a classification ranking that encompasses safety, production continuity, scrap loss, etc. user. Each effect is given a severity number (S) from 1 (no danger) to 10 (critical). A failure mode with severity number of 10 results in severe dissatisfaction of the customer and may even result in the physical injury due to the failure. Severity ratings in the range of 4-6 result in mild dissatisfaction of the customer whereas those in the range of 1-3 are not so severe and may even be not detected [2-6]. Table 1gives the guidelines based on which severity ratings were given. 3-5 Table 1: Severity Ratings Description Failure is of such minor nature that the customer (internal or external) will probably not detect the failure. Failure will result in slight customer annoyance and/or slight deterioration of part or system performance 6-7 Failure will result in customer dissatisfaction and annoyance and/or deterioration of part or system performance. Severity Rating 1-2 Failure will result in high degree of customer dissatisfaction and cause non-functionality of system Failure will result in major customer dissatisfaction and cause non-system operation or non-compliance with regulations 8-9 10 2.4 STEP 4: ASSIGN THE OCCURANCE RATINGS Occurrence ratings denote how often such failures occur. In this step it is necessary to look at the number of times a failure occurs. This can be done by looking at similar products or processes and the failure modes that have been documented [4]. A failure mode is given an occurrence ranking (O), again 1–10. If a failure is inevitable or occurs often, then it is given a rating in the range of 8-10. Those with mild occurrences are given 4-6 whereas those with low or eliminated failure have 1-3 occurrence ratings [2-6]. Table 2 gives the occurrence ratings based on which FMEA table is designed in this paper. Occurrence Rating 1 2,3 4,5,6 Table 2 Occurrence Ratings Meaning Failure eliminated or no know occurrence Low or very few Moderate or few occasional 7,8 High or repeated failure occurrence 9,10 Very high rate of failure or inevitable failures 5
  • 6. International Journal of Industrial Engineering Research and Development (IJIERD), ISSN 0976 – 6979(Print), ISSN 0976 – 6987(Online) Volume 4, Issue 3, September - December (2013), © IAEME 2.5 STEP 5: ASSIGN DETECTION RATING This section provides a ranking based on an assessment of the probability that the failure mode will be detected given the controls that are in place. The proper inspection methods need to be chosen. The probability of detection is ranked in reverse order. For example, a "1" indicates a very high probability that a failure would be detected before reaching the customer; a "10" indicates a low – zero probability that the failure will not be detected [2-6]. Table 3 shows the guidelines based on which the detection ratings of a product are given. Detection Rating 1 2-4 5-6 7-8 9 10 Table 3: Detection Rating Description Very certain that the failure will be detected High probability that the defect will be detected Moderate probability that the failure will be detected Low probability that the failure will be detected Very Low probability that the defect will be detected. Fault will be passed to customer undetected 2.6 STEP 6: CALCULATE THE RISK PRIORITY NUMBER The risk priority number (RPN) is simply calculated by multiplying the severity ranking times the occurrence ranking times the detection ranking for each item. Risk Priority Number = Severity × Occurrence × Detection The total risk priority number should be calculated by adding all of the risk priority numbers. This number alone is meaningless because each FMEA has a different number of failure modes and effects. The small RPN is always better than the high RPN. The RPN can be computed for the entire process and/or for the design process only. Once it is calculated, it is easy to determine the areas of greatest concern. There could be less severe failures, but which occur more often and are less detectable. These actions can include specific inspection, testing or quality procedures, redesign (such as selection of new components), adding more redundancy and limiting environmental stresses or operating range. Once the actions have been implemented in the design/process, the new RPN should be checked, to confirm the improvements [1,2,6]. Table 4: FMEA Table for Punching Process S. No 1 Occurrence Rating 6 Detection Rating 8 Leading to downtime 5 6 Additional die damage 3 Problem Effects Punch Chipping & Point Breakage Deformation Severity Rating 7 3 6 Causes Solutions RPN High impact or compressive failure Misalignment resulting in lateral forces Part material movement Change punch materials and diameter 336 210 Check overall die alignment Use a retainer or punchmounted stripper 63
  • 7. International Journal of Industrial Engineering Research and Development (IJIERD), ISSN 0976 – 6979(Print), ISSN 0976 – 6987(Online) Volume 4, Issue 3, September - December (2013), © IAEME 5 1 3 6 2 2 1 1 8 2 7 Poor material control Excessive stripping force Punch point hardness too low Improper punch material selected Sharpening damage 1 Regrind burr 1 1 Tight die clearance 6 2 Sharp corners on shaped punches 6 4 Flat punch face 3 4 4 3 7 2 Excessive burr 7 2 7 2 Stress concentration at edges 7 Improper heat treatment Improper punch stagger Improper finish on punch point and/or punch face Incorrect clearance Review die, press, & feeder setup Reduce punch-to-die entry Increase punch-to-die button clearance Consider coatings to add lubricity 35 126 28 Verify hardness 7 Change punch material Use Coolant, correct speeds and feeds for grinding Remove regrind burr Increase clearance Change material Use Coatings and surface treatments Increase clearance in the corners of die button Use shear angles and use edge breakers Triple tempered for high-speed and follow the guided speeds Cut-off operation & large point first to enter 112 49 7 84 168 84 84 98 Ensure there are no harsh grinding Restore correct clearance 98
  • 8. International Journal of Industrial Engineering Research and Development (IJIERD), ISSN 0976 – 6979(Print), ISSN 0976 – 6987(Online) Volume 4, Issue 3, September - December (2013), © IAEME Decreases resistance to fracture Shortens fatigue life 5 1 Worn tools Sharpen or replace tools Misalign components Check alignment 8 Tight die clearance Excessive land length Increase die clearance Change relief from counter bore to taper Land length should not exceed four times material thickness Verify there is no reverse taper in the land of the die button 1 1 3 Taper in the land of the die button 6 Punch breakage 1 5 Slug Jamming 1 6 3 4 2 Inadequate taper relief in die button Worn die button Punch point deformation 9 2 9 3 Worn or chipped punch Rough land in die button 5 3 Slug Pulling Punch point deformation Excessive wear on punch and die 6 2 Slug tipping 7 4 1 1 Obstruction in slug relief hole 9 1 Bell mouth wear in die button 8 28 8 48 120 96 Increase per side taper Sharpen, replace, and/or change die button material 144 216 Sharpen or replace punch Use die buttons with smooth wire cut, or ground land Check lubrication— consider lubricating both sides of part material Examine slug path Consider increasing the size of the relief hole in lower plate Increase die clearance Check alignment Change die button material Surface defects 35 40 48 56 54
  • 9. International Journal of Industrial Engineering Research and Development (IJIERD), ISSN 0976 – 6979(Print), ISSN 0976 – 6987(Online) Volume 4, Issue 3, September - December (2013), © IAEME Broken punches and dies 8 2 Punch entry too deep 3 3 Punch entry not deep enough Excessive die clearance Slug not held in the land 9 3 Reduced die performance Reduced punch and die life Requires heat treatment of parts High stress concentration in parts 7 1 3 Punch Wear and/or Galling 2 3 5 1 4 9 1 Tight die clearance 6 2 Use slug control system Reduce punch entry 54 Increase punch entry Reduce die clearance Use slug control system Use vacuum slug sucker Blow air through center hole in punch Use negative taper in land Check lubrication Increase taper relief or use counter bore die Punch entry too deep Sticky lubricants Not enough relief on die 3 2 Misalignment 4 2 Regrind burr 6 1 Improper sharpening of punch 3 1 5 1 Improper punch material Sharp corners on shaped punches 4 1 9 Punch surface too rough 96 Increase die clearance Change punch materials 54 36 18 72 63 84 Reduce punch entry Check die & press alignment Remove regrind burr—break sharp Use flood coolant, and correct grinding wheel speed & feed for steel type Change punch materials Increase clearance in the corners of the die button Consider punch finish improvements 42 56 42 21 35 28
  • 10. International Journal of Industrial Engineering Research and Development (IJIERD), ISSN 0976 – 6979(Print), ISSN 0976 – 6987(Online) Volume 4, Issue 3, September - December (2013), © IAEME 5 6 3 Insufficient chamfer in retainer 4 7 Backing plate too hard 3 6 Head is too hard 4 High impact or high compressive load on head 9 1 Incorrect clearance 2 Lack of lubrication 5 1 6 1 Tough materials Ineffectual extraction system 10 1 Incorrect clearance 2 2 Lack of lubrication 6 Wear 6 3 9 Punch pumping 5 Work part deformation 2 Deflection of punch head 8 5 Excessive shear on punches and die Punch does not extract Increase in punch-to-die clearance 1 Holes too close in sequence 6 8 Speed too fast Increased delay Imprecise components Reduced tool life 10 Lack of lubrication on part and/or incorrect lubrication Punch breakage 7 Punch Head Breakage 2 10 10 6 10 70 Check lubrication Verify head thickness is properly fit in the retainer counter-bore Chamfer retainer to clear head fillet on punch Draw back backing plate to reduce hardness— RC 40-50 Draw back head of punch to lower RC Increase head diameter and thickness Increase shank diameter Restore correct clearance Use proper lubrication or coated punches Revise clearance Replace with a spring or reloaded assembly 100 180 280 180 200 90 60 50 60 Restore correct clearance Use proper lubrication or coated punches Reprogram alternate punching sequence 100 Slow down, use more coolant 288 40 60
  • 11. International Journal of Industrial Engineering Research and Development (IJIERD), ISSN 0976 – 6979(Print), ISSN 0976 – 6987(Online) Volume 4, Issue 3, September - December (2013), © IAEME 3 High cost 4 5 Improper feed rate (too slow) Improper punch-die angle 4 Reduced tool life 8 4 10 Hard material 4 Dimensional inaccuracies 7 5 7 6 5 6 4 6 Improper clearance angle Too much shearing force during punching Tough work material Frequent resharpening of tool Use higher grade tool material, add surface treatment Increase feed rate Change to correct punching angle 126 192 120 120 Give proper clearance angle 168 Select proper tool materials Select premium tool Resharpen the tool periodically 120 96 3. RESULTS & DISCUSSIONS From the table 4, which shows FMEA table for punching process, it is observed that the punch chipping and point breakage due to the high impact or compressive force has the highest risk priority number. This can be minimized by the proper selection of punch-die materials and by maintaining the correct clearance between punch and die. The burr and slug formations also have detrimental effect on the overall quality of the final product. These undesirable developments can be curtailed by varying the feed rates and speed of the machine. To reduce the breakage of tool and burr formation due to excessive feed rate and high cutting speeds, we have to perform the process in rated speed and acceptable feed rates. In order to produce the punched products without any deformations or distortions, better tool and work holding devices are to be used. To reduce metal chipping, initial speed has to be minimum and proper cutting speeds should be employed. The tool life can be increased by proper lubrication, minimizing the wear and other parameter perfection has to be achieved. 4. CONCLUSION Thus the high speed punching process in motor manufacturing section has been analyzed and the expected failure modes have been noted. From the results of the critical analysis made on the punching process, the failure modes with greater risk priority number has been selected. The causes, effects and possible alternate solutions are given along with the ratings and priorities of action that decrease risk failure. The risk priority numbers are specified which indicates the necessity of care for producing defect-free punching process and its products. Thus this process analysis will serve as a helpful tool to detect the failure 11
  • 12. International Journal of Industrial Engineering Research and Development (IJIERD), ISSN 0976 – 6979(Print), ISSN 0976 – 6987(Online) Volume 4, Issue 3, September - December (2013), © IAEME modes occurring in the punching process and also assures in the effective functioning of the process. This study provides a documented method for selecting a design with a high probability of successful operation and safety. As a result of this approach, the system development cost and time, the possibility of occurrence of same kind of failure in future are reduced along with improved quality, reliability and safety of process/product. Consequently, the productivity of the product is also increased. This approach can be well suitably applied to consumer products like automotives, home appliances, etc., and other fields such as manufacturing, aerospace, instrumentation, medical, chemical processing, etc. REFERENCES 1. V Janarthanan, D Rajenthira Kumar. Root Cause analysis & process failure mode and effect analysis of TIG Welding on SS 3041 material (Proceeding of NC MISAA 2013, copyright 2013 PSGCT) 2. Aravind.P, Rooban Babu.R, Arun Dhakshinamoorthy, Venkat Prabhu.N, Subramanian.SP¸ An integrated approach for prediction of failures by process failure mode and effect analysis (PFMEA) in MIG Welding-a predictive analysis (ISBN-97893-82208-00-6) 3. D.H.Stamatis. Failure mode and effect analysis : FMEA from theory to execution (Book 2nd Edition (1995)) 4. Robin E. McDermott, Raymond J. Mikulak, Michael R. Beauregard. The basics of FMEA-Productivity press (1996) 5. Aravind.P, Subramanian.SP, SriVishnu.G, Vignesh.P. Process failure mode and effect analysis on TIG Welding process - a criticality study (ISSN-223-1963) 6. “Failure modes and effects analysis (FMEA)”- Copyright © 2004 Institute for Healthcare Improvement. 7. Jim Szumera, James. A. Szumera. The Metal Stamping Process (Industrial Press Inc, 2003). 8. A.Mariajayaprakash, Dr.T. SenthilVelan and K.P.Vivekananthan, “Optimisation of Shock Absorber Parameters using Failure Mode and Effect Analysis and Taguchi Method”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 2, 2012, pp. 328 - 345, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. 9. Pravin Kumar .S, Venkatakrishnan.R and Vignesh Babu.S, “Process Failure Mode and Effect Analysis on End Milling Process- A Critical Study”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 5, 2013, pp. 191 - 199, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. 12