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. ISSN: 2231-5381 http://www.ijettjournal.org Page 104 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 root cause analysis .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 engineering tolerance 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) ISSN: 2231-5381 http://www.ijettjournal.org Page 105 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 Process capability index 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) ISSN: 2231-5381 http://www.ijettjournal.org Page 106 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.