National Conference on Advances in Mechanical Engineering Science (NCAMES-2016)

Study and Analysis of Process Capability of 4000 Ton Mechanical Press Using 8D Method Nithin Joshuva1, Dr. Thomas Pinto2 1Assistant Professor, Department of Mechanical Engineering, Srinivas Institute of Technology, Valachil, Mangaluru, Karnataka State, India – 574143 2Professor and Head, Department of Mechanical Engineering, Srinivas Institute of Technology,Valachil, Mangaluru, Karnataka State, India – 574143

Abstract- Forging is a mass production activity. or whether the current team should take other areas Some of the manufacturing equipment’s like for improvement be addressed. mechanical press produce a large number of parts in The Ford 8D’s (disciplines) process is most its running time. Break down of these machines lead effective in dealing with chronic recurring problems, to unavailability of the machines, there by affecting primarily defects or warranty issues. Increasingly, the process performance in terms of major these days, companies practicing lean manufacturing production loss and also affects the quality of are requiring their employees to also understand the product. To overcome this problem an important 8-Discipline approach (8D) to team-based problem problem solving method “Eight disciplines of solving. These essentially present a standard problem solving method” can be employed. methodology for data analysis and statistical The 8-Discipline problem-solving methodology thinking and are a key lean tool. Originally (also called “8-Step Plan” or TOPS – “Team developed at Ford Motor Company; 8D was Oriented Problem- Solving”) is a structured introduced in 1987 in a manual titled "Team procedure used to arrive at the root cause of a Oriented Problem Solving" (TOPS). The focus of problem. 8D uses composite problem solving this system was to use this approach in a team methodology, by employing tools and techniques environment. from various approaches. It establishes a permanent A. Steps in 8D problem solving process corrective action based on statistical analysis of the  D1: Use a Team: Establish a team of people problem and focuses on the origin of the problem by with product/process knowledge. determining its root causes.  D2: Define and describe the Problem: Specify 8D procedure is implemented for the break the problem by identifying in quantifiable terms downs, there by arriving at its root causes. In this who, what, where, when, why, how, and how process various tools like Ishikawa or fishbone many (5W2H) for the problem. diagram, process capability etc., are employed at  D3: Develop Interim Containment Plan; various stages. Suitable corrective and preventive Implement and verify Interim Actions: actions are taken which helps to eliminate its Define and implement containment actions to reoccurrence. This in turn improves process and isolate the problem. quality of the product.  D4: Determine Identify, and Verify Root Causes and Escape Points: Identify all Keywords: 8D, 5-why analysis, TOPS, FMEA, applicable causes that could explain why the process capability problem has occurred. Also identify why the I. INTRODUCTION problem has not been noticed at the time it The problem solving process is a logical occurred. All causes shall be verified or proved, sequence for solving problems and improving the not determined by fuzzy brainstorming. One can quality of decisions. It is also a guide to identify use five whys or Ishikawa diagrams to map which tools and techniques to apply. Problems, no causes against the effect or problem identified. matter what their size or complexity, can best be  D5: Choose and Verify Permanent solved by working through a sequence of steps, Corrections (PCs) for Problem/Non everything possible will be done to apply the Conformity: Through pre-production programs available resources in the most effective and quantitatively confirm that the selected efficient manner, considering a number of options correction will resolve the problem. and selecting the best solution. There is a structured  D6: Implement and Validate Corrective approach to problem solving that will help to prevent Actions: Define and Implement the best adverse consequence. The eight steps can be corrective actions. regarded as a continuous cycle. Once the team has  D7: Take Preventive Measures: Modify the monitored the solution to ensure that the problem is management systems, operation systems, properly solved the members will be able to decide practices, and procedures to prevent recurrence to continue the cycle and seek further improvement of this and all similar problems.

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National Conference on Advances in Mechanical Engineering Science (NCAMES-2016)

 D8: Congratulate Your Team: Recognize the collective efforts of the team. The team needs to be formally thanked by the organization.

The above table enables the detailed understanding of the characteristics of the breakdown and provides a strong foundation of facts. It also gives the confidence to carry out the .Further detailed analysis of the breakdown in the form of root cause analysis enables to find the actual cause for the breakdown and helps to minimize it or completely eliminate it if possible.

II.Process capability: Process capability refers to the long term performance of a process after the process has been brought under control. It is the ability of the combination of people, machine, methods, material, and measurements to produce a product that will

Fig 1 : Steps in 8D problem solving process consistently meet the design requirements or In this paper, the data pertaining to total number customer expectation. Process capability is also the of machines in operation at AMW-MGM forgings performance of a process after significant causes of was collected .Data collection also involves variation have been eliminated. identification of frequent break downs of 4000 ton A process is capable (Cp≥1) if its natural tolerance forging press ,where frequent break downs effects lies within the or quality of the product. Further data collection specifications. The measure of process capability of includes calculation of the process capability of a stable process is 6σ, where σ is the inherent products 1109 Stub axle (R5-03).Reasons for scrap process variability estimated from the process. A and rejection rate due to underfilling of this minimum value of Cp=1.33 is generally used for an product.This paper is mainly highlighted on the use on-going process. This ensures a very low rejected of fishbone diagram and process capability. rate of 0.007% and therefore is an effective strategy for prevention of nonconforming items. Table I: Machine break down details of 4000 ton forging press Process capability for 1109 Stub axle (R5-03) The allowable thickness dimension for the product is 14+2.5 mm for the upper specification limit (USL)

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National Conference on Advances in Mechanical Engineering Science (NCAMES-2016)

and 14-0.5 mm for the lower specification limit. Here 50 consecutive pieces is selected in 10 subgroups of 5.

Table II: Readings for the given 25 consecutive pieces of R5-03

The capability of the process to produce within the Fig 2. Pie chart showing defects of R5-03 specification limits is determined as, between period Jun-15 to Nov-15

III.Analysis and Results Inherent process variability A.Root cause analysis Root Cause Analysis is a method that is used to address a problem or non-conformance, in

order to get to the “root cause” of the problem. It is Based on the subgroup size (n=5), =2.326 used so that we can correct or eliminate the cause, = =16.5/10 and prevent the problem from reoccurring.In this process the main tool of root cause analysis , =1.65 fishbone diagram is employed. =0.709 Cause and Effect Diagram also called as Fishbone or Ishikawa Diagram =0.7052 The fishbone diagram identifies many possible causes for an effect or problem. It Since 1, the process is not capable of immediately sorts ideas into useful categories. Each producing the product that will meet the engineering identified problem should be scrutinized individually specifications. to establish what factors have contributed to that is given by, problem.It is also a useful technique for opening up thinking in problem solving.

Where =Over all process average a) Ram slip in the unit = =14.828

Since =0.6243 1.33, the process cannot be cantered. Suitable corrective action must be taken to eliminate the causes.

Table III: Defects of 1109 Stub axle (R5-03)

The fish bone diagram for the ram slip problem indicates the main causes and its sub-causes. Problem can be prevented by proper selection of materials for aluminium liners (use of aluminium alloys) and hard plates (use of budreus die steel 2714)

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National Conference on Advances in Mechanical Engineering Science (NCAMES-2016)

and by proper setting of torque on the ram adjustment unit. b) Press stroke problem

The capability of the process to produce within the specification limits is determined as,

Inherent process variability

Based on the subgroup size (n=5), =2.326 = =5.5/10 =0.55 =0.2364 The main causes and its various sub-causes for the press stroke problem are indicated in the above fish bone diagram.By proper maintenance of the machine mounting bolts problem can be prevented and also it =2.1150 strengthens the preventive maintenance. Since 1, the process is capable of producing the product that will meet the engineering specifications.  Problem: Ram slip in the unit Results from root cause analysis Process capability index is given by,  Die damage reduced  Machine down time reduced  Overall spare cost reduced Where =Over all process average  Maintenance cost reduced = =15.112  Quality of the product improved  Preventive maintenance management system strengthened

 Problem: Press stroke problem Cpk=1.957 Results from root cause analysis Since 1.33, the process can be adequately  Reduced vibration of the unit centered.  Cam unit failure reduced .  Considerable increase in the life of foundation bolts Table V: Percentage rejection of 1109 Stub axle  Increased life of relative parts (R5-03) due to U/F  Quality of the job increased  Productivity increased

Process capability for 1109 Stub axle (R5-03) after implementation of 8D method The allowable thickness dimension for the product is, 14+2.5 mm for the upper specification limit (USL) and 14-0.5 mm for the lower specification limit will (LSL).

Table IV: Readings for the given 25 consecutive pieces of R5-03

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National Conference on Advances in Mechanical Engineering Science (NCAMES-2016)

Product CP CPK 1109 Stub 2.115 1.957 axle(R5-03) From the above results it can be concluded that before the implementation of the 8D method the values for CP and CPK was less than the required values of 1.0 and 1.33 respectively, therefore the process was not capable. After the implementation of the 8D method there is a significant increase in the values of CP and CPK. Its process spread is within engineering specifications; therefore the process is capable. Hence the process can be improved significantly using 8D problem solving method. Also the rejection rate of three products due to under filling for some of the months was very high and was exceeding pre-set target value of 2% before Fig 3. Comparison of rejection rate for R5-03 implementation of the 8D method. After the implementation of the 8D method the rejection rate considerably meets the target value and ranges from The above graph reveals that after the 1.71% to 2.1% between periods Mar-15 to May-15. implementation of 8D method the percentage Hence the product can be improved significantly rejection of this product due to under filling does not using 8D problem solving method. exceed the present target value of 2%. Hence the rate of rejection of three products is considerably REFERENCES reduced between periods Mar-15 to May-15. [1] Carlos A. Riesenberger and Sergio D. Souza “The 8D Methodology: An Effective Way to Reduce Recurrence of Customer Complaints”, London, 2010, vol III. IV.CONCLUSION This paper work is carried out on 4000 ton [2] Marjanca krajnc “With 8D method to excellent quality”, mechanical press. After the analysis it is found that Journal of universal excellence, Oct2012, pp.118-129. the process is improved and the rejection rate of the [3] S.B.Kamble, D. N.Raut & D.B.Patil “8D’s steps to solve industrial quality problem”, International conference on component due to Under filling is reduced by 8D technology & business management, Mar2012, pp.679-684. method. It also helps to identify the causes for the [4] Bill Arnott “The 8 Discipline Approach to Problem breakdown of mechanical press by under taking root Solving”, Canada, 2004. cause analysis. [5] Hsiang-Ru Chen and Bor-Wen Cheng “A case study in solving customer complaints based on the 8Ds method”, - Some of the tools of root cause analysis like fish Journal of the Chinese Institute of Industrial Engineers, bone diagram are implemented to identify the actual Sep 2010, pp.339-350. causes of the breakdown. Then some necessary [6] H P Garg “Industrial Maintenance”, Rajendra Printers Pvt actions was taken to improve the system using root Ltd, New Delhi, 1972. [7] Anderson B & Fagerhaug T “Root cause analysis: cause analysis and counter measures such that Simplified tools and techniques”. Milwaukee: ASQ similar type of break downs can be reduced. It has Quality Press, 2000. also strengthened the preventive maintenance [8] Automotive Industries Action Group (AIAG). Potential management system by addition of some of the Failure Mode and Effects Analysis, Third Edition, MI: AIAG, Southfield, 2001. important points in the check list after root cause [9] Adedeji b.badiru and Babatunde j.ayeni “Practisioners analysis. guide to quality and process improvement”, 1993. The process capability values for the two [10] www.national.com/en/quality/8d, 8D problem solving components before implementation of 8D method process. [11] http://elsmar.com/8D, the 8D problem solving are as follows: methodology. Product CP CPK [12] www.AMW-MGM forgings Ltd.com 1109 Stub 0.705 0.624 axle(R5-03)

After implementation of 8D method the process capability values observed are:

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