Lean Six Sigma Green Belt

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Overview of Lean Six Sigma Tutorial

1.1 Overview of Lean Six Sigma

Hello and welcome to the first lesson of the Lean Six Sigma Green Belt Course offered by Simplilearn. Lean six sigma is an improvement methodology that combines the best of the Lean concepts and Six Sigma tools. The emphasis is on obtaining the best of both improvement methodologies, while minimizing any potential weaknesses. The emphasis is on taking advantage of the value generation focus offered by the lean method, while maintaining the statistical rigors of the Six Sigma methodology. This lesson provides an overview of Lean Six Sigma. Let us look at the objectives of this lesson in the next screen.

1.2 Objectives

After completing this lesson, you will be able to describe the basics of Six Sigma. You will also be able to explain lean principles in the organization and design for Six Sigma or DFSS. Let us start with the first topic in the following screen.

1.3 Topic 1 - Six Sigma

In this topic, we cover the basics of six sigma. Let us start with an introduction to Six Sigma in the following screen.

1.4 Introduction to Six Sigma

Six Sigma is a highly disciplined process that focuses on delivering near-perfect products and services consistently. Its strength is that it is a continuous improvement process with an unwavering focus on change empowerment, seamless training of resources and continuous top management support. These three are known as the Pillars of Six Sigma. If Six Sigma is implemented methodically, it will give sustained results for any process. Now the question arises as to what is a process. This will be explained in the next screen.

1.5 Process

A process is a series of steps designed to produce a product and or service according to the requirement of the customer. A process mainly consists of four parts, Input, Process steps, Output, and Feedback. Input is something put into a process or expended in its operation to achieve an output or a result. For example, Man, Material, Machine, and Management. Output is the final product delivered to an internal or external customer. For example, product or services. It is important to understand that if the output of a process is an input for another process, the latter process is the internal customer. Each Input can be classified as Controllable (represented as C), Non-Controllable (represented as NC), Noise (represented as N), and Critical (represented as X). The most important aspect of the process is the feedback. As can be inferred from the image, any change in the inputs causes changes in the output. Therefore, y equals f of x. Feedback helps in process control, because it suggests changes to the inputs. Let us learn about the process of Six Sigma in the next screen.

1.6 Process of Six Sigma

Six Sigma follows a process called DMAIC (Pronounced as D-MAC). DMAIC stands for Define, Measure, Analyze, Improve, and Control. Click each tab to know more. In the Define phase, we define the problem statement and plan the improvement initiative. Consider a typical problem in an Organization. A particular organization’s customers are not satisfied with the current support process of the organization. You can define the problem as the support process of the organization is at 20% satisfaction. In Six Sigma, the projects are always defined objectively. In addition to defining the problem, the Six Sigma project team is also formed in this phase. The Measure phase collects the data from the process and determines the current quality and operational performance levels. Also, the measurement criteria such as how to measure, when to measure, and who will measure are established. In the Analyze phase, the business process and the data generated from the measurement phase are studied to understand the root causes of the problem. In the Improvement phase, possible improvement actions are identified and prioritized. These are then tested and the improvement action plan is finalized. In the last phase, which is the Control phase, the Six Sigma team goes for a full-scale implementation of the improvement action plan and sets up controls to monitor the system in order to sustain the gains.

1.7 List of DMAIC Tools

The list of DMAIC tools is discussed in this screen. There are specific tools used in each phase of the Define, Measure, Analyze, Improve, and Control process. Later in this course, important tools of each phase will be discussed. Click each phase to view the list of tools. The define phase uses tools such as Supply, Input, Process, Output, Customer or SIPOC (Pronounce as: sye-poc) Diagram, Voice of Customer or VOC (Pronounce as: v-o-c), Critical to Quality or CTQ Trees, Quality Function Deployment or QFD, Failure Mode and Effects Analysis or FMEA, Cause and Effect or CE Matrix, and Project Charter. The measure phase uses tools such as GAGE R and R Variables, Run Charts or Control Charts, Cp, Cpk, Sigma level (Z Level) and Defects per Million Opportunity or DPMO, and Anderson Darling Test. The tools used in the analyze phase are Simple Linear Regression or SLR, Pareto Charts, Fishbone Diagram, FMEA, and Multi-Vari Charts or Hypothesis Tests. In the improve phase, the tools that can be used are Brainstorming, Piloting and FMEA, and Design of Experiments or DOE (Pronounce as: d-o-e) (If needed). The control phase uses tools such as Control Charts, Control Plan, and Measurement System Analysis or MSA Re-analysis. Note that some of these tools can be used interchangeably between the phases.

1.8 How does Six Sigma Work

Let us understand how Six Sigma works in this screen. Six Sigma is successful because of the following reasons: Six Sigma is a management strategy. It creates an environment where the management supports Six Sigma as a business strategy and not as a stand-alone approach or a program to satisfy some public relations need. Six Sigma mainly emphasizes the DMAIC method of problem solving. Focused teams are assigned well-defined projects that directly influence the organization’s bottom line with customer satisfaction and increased quality being by-products. Six Sigma also requires extensive use of statistical methods. The next screen will focus on some key terms used in six sigma.

1.9 Six Sigma Terms

Some of the basic terms used in Six Sigma are Sigma, Opportunity, Defect, Specification limits, Rolled Throughput Yield (RTY), and Defects per Million Opportunity (DPMO). Click each tab to review their definitions. Sigma is a Greek letter used as a standard notation for standard deviation of a process metric. The Six Sigma quality means 3.4 defects in 1 million opportunities or a process with 99.99966% yield. An opportunity is defined as every chance for a process to deliver an output that is either “right “ or “wrong”, as perceived by the customers. A defect is defined as every result of an opportunity that does not meet customer specifications and does not fall within Upper Specification Limit or USL and Lower Specification Limit (LSL). Limits set by a customer representing the range of a product deviation the customer can tolerate or accept is termed as a specification limit. Upper specification limit is the highest acceptable limit and lower specification limit is the lowest acceptable limit set by a customer. Rolled Throughput Yield (RTY) is a measure of process efficiency expressed as percentage. Defects per Million Opportunities (DPMO) is also known as Non-Defect per Million Opportunities (NPMO) and is a measure of process performance.

1.10 Sigma Level Chart

Let us look at the sigma level chart in this screen. As discussed earlier, the Six Sigma quality means 3.4 defects in one million opportunities or a process with 99.99966% yield. The sigma level chart given on the screen shows the values for other sigma levels. Please take a look at the values carefully. Let us understand the benefits of Six Sigma in the next screen.

1.11 Benefits of Six Sigma

The organizational benefits of Six Sigma are as follows: A Six Sigma process eliminates the root cause of problems and defects in a process. Sometimes the solution is creating robust products and services that mitigate the impact of a variable input or output on a customer’s experience. For example, many electrical utility systems have voltage variability up to and sometimes exceeding a 10% deviation from nominal value. Thus, most electrical products are built to tolerate the variability, drawing more amperage without damage to any components or the unit itself. Using Six Sigma reduces variation in a process and thereby reduces wastes in a process. It ensures customer satisfaction and provides process standardization. Rework is substantially reduced because one gets it right the very first time. Further, Six Sigma addresses the key business requirement. Six Sigma can also be used by organizations to gain advantage and become world leaders in their respective fields. The entire Six Sigma process ultimately aims to satisfy customers and achieve organizational goals. In the next screen, Six Sigma and quality will be explored.

1.12 Six Sigma and Quality

Taking a process to Six Sigma level ensures that the Quality of the product is maintained. The primary goal of improved quality is increased profits for the organization. In very simple terms, Quality is defined as the Degree of excellence of a product or a service provided to the customer. It is conformance to customer requirement. If the customer is satisfied with the product or service, then the product or service is of the required quality.

1.13 History of Six Sigma

Let us now look at the history of Six Sigma. The most important part in the history of Six Sigma is Motorola initiating Six Sigma for process improvement and thereby reducing defects to negligible levels, and GE using Six Sigma to improve the entire business system. Click each button to know more. Motorola first introduced Six Sigma in the year 1986. Bill Smith and Mikel Harry were the pioneers of the Motorola Six Sigma movement. In the year 1995, Jack Welch, then CEO of GE, initiated Six Sigma at GE to improve the entire business system. By the year 1998, Allied Signal had saved $0.5 billion by using Six Sigma. By the year 2000, GE had saved $2 billion annually with the help of Six Sigma. By 2001, Motorola saves $16 billion cumulatively by using Six Sigma.

1.14 Six Sigma Team

Let us understand the structure of the Six Sigma team in this screen. There are five levels in the Six Sigma Team. The first level consists of the top executives of the organization. These people lead change and provide direction, as they own the vision of the organization. For any improvement initiative to work, it is important that top management of the organization be actively involved in its propagation. The top executives own the Six Sigma initiatives. Next in the level are Six Sigma Champions. They identify and scope projects, develop deployment and strategy, and support cultural change. They also identify and coach Master Black Belts. 3-4 Master Black Belts work under every Champion. Six Sigma Master Black Belts train and coach Black Belts, Green Belts, and various Functional Leaders of the organization. They usually have at least 3-4 Black Belts under them. The Fourth level in Six Sigma structure is Six Sigma Black Belts. They apply strategies to specific projects, and lead and direct teams to execute projects. Finally, there are Six Sigma Green Belts. They support the Black Belt employees by participating in project teams. Green belts play a dual role. They work on the project and perform day-to-day jobs related to their work area. Let us proceed to the next topic of this lesson.

1.15 Topic 2 - Lean Principles

In this topic, we will look at what Lean is and how Lean is applied to a process. Let us start with a brief overview of Lean in the following screen.

1.16 Overview of Lean

The term “Lean” refers to creating more value for customers with fewer resources. It means reducing unwanted activities or process or anything that does not add value to the product or service for the customer. The Lean Philosophy is “to provide perfect value to the customer through a perfect value creation process that has zero waste.” While the ultimate goal is to achieve zero waste, you may not always get there in the first couple of tries. However, you will achieve minimum waste and continue to move towards zero waste eventually. Hence, lean is the path towards perfection. There are many benefits of Lean and some of them are: Lean reduces cost and improves quality. Lean also speeds up delivery by eliminating non-value-added activity or NVA in a process, by identifying and eliminating waste. A popular misconception is that lean is suited only for manufacturing. Lean can be applied to all kinds of businesses and processes. It is not just a cost reduction program, but an approach to optimize end to end processes with maximum value for all. In the next screen, let us learn about the history of Lean.

1.17 History of Lean

Some Lean principles have been in existence and use for decades. The major implementations were noticed during the 1450s, 1913, and 1930. Click each button to learn more. In the 1450s, Lean principles were implemented primarily in the manufacturing industry in various forms like flow, interchangeable parts, automatic assembly lines, automatic defect detection, and more. The first instance of truly integrated Entire Production Process was performed by Henry Ford in 1913 during the production of their “Model T” car. The Model T was not just limited to one color but also to one specification, so all Model T chassis were essentially identical. Lean manufacturing was developed by the Japanese automotive industry utilizing the Toyota Production System (also known as TPS), following the challenge to rebuild the Japanese economy after World War II. In 1930, Kiichiro Toyoda, Taiichi Ohno, and others at Toyota revisited Ford’s original thinking, and invented the Toyota Production System. The goal was to improve the end-to-end production system and provide more value to customers. It occurred to them that a series of simple innovations might make it possible to provide both continuity in process flow and also a wide variety in products The Total Production System shifted the focus from individual machines and their utilization to the flow of the product through the total end-to-end process. With this approach and changes in the mindset, Toyota was able to achieve low cost, high variety, high quality, and very rapid throughput times to respond to changing customer desires.

1.18 Lean Six Sigma

Let us learn about Lean Six Sigma. Lean Six Sigma is the methodology that combines the best of both lean concepts and the Six Sigma methodology and tools. Lean and Six Sigma have some overlapping goals toward improvement, with the aim of creating the most efficient system. Both use different approaches to achieve improvement, but their methods are complementary. Lean Six Sigma is an approach to integrate the power of Six Sigma Methodology, its tools along with the Lean Concepts which can be applied within an organization. This helps in achieving improvement at a faster pace, improving quality, maximizing the shareholder value, and increasing customer satisfaction. For any Lean Six Sigma improvement project, it is often advantageous to begin with Lean to streamline processes and Rapid Improvement Events. This helps in understanding chronic problems and handling them to drive rapid improvements. After this, Six Sigma methodology can be applied for further root cause analysis and breakthrough improvements. In the next screen, let us compare the Lean and the Six Sigma methodologies and see how they complement each other.

1.19 Lean vs. Six Sigma

The primary focus of Lean is on Efficiency whereas Six Sigma focuses on effectiveness. The improvement principles of Lean focus on identifying value, eliminating unnecessary steps and wastes, and dramatically improving the process speed. On the other hand, Six Sigma encourages breakthrough in processes, designs, while improvement teams focus on identifying root cause, eliminating chronic problems, and reducing variation in processes. In statistical terms, Lean is about moving mean, reducing cycle time, reducing excess inventory, and improving response time. Six Sigma is about reducing variation, decreasing defect rates, and increasing product yield. Let us learn about Lean Concepts.

1.20 Lean Concepts

Lean is a continuous process to eliminate or reduce non-value added activities or NVA and waste from a process. When Lean is applied to a process, it increases the continuous flow and minimizes instances of stop-flow and unbalanced production. Before applying Six Sigma to a process, it is important to check the waste status of the process. If waste and NVAs exist, they should be eliminated before applying Six Sigma. Click the button given on the screen to view an example for Lean concepts. Let us understand how Lean can be applied to a process to reduce waste. Consider an operation with defects in the welding process. A welding technician observes that he is sometimes welding rusty components together. One approach to this problem could be to use an oil coating to prevent components from rusting. However, this could create additional tasks of cleaning the components before welding to prevent the oil from causing further problems. This is a traditional solution. Another approach to this problem is the Lean approach, where ways to reduce inventory can be identified and hence waiting or storage time could be minimized. A shorter waiting time would prevent rust from forming on the steel components.

1.21 Lean Concepts - Process Issues

Lean focuses on three major issues in a process, known by their Japanese names, Muda, Mura, and Muri. Muda refers to non-value adding work, Mura represents unevenness, and Muri represents overburden. Together, they represent the key aspects in Lean. Let us look at the seven types of waste in the next screen.

1.22 Seven Types of Waste

There are seven types of Muda or waste described within Lean Principles: Overproduction: This refers to producing more than is required. For Example, a customer needed 10 products and 12 were delivered. Inventory: In simple words, this refers to stock. The term inventory includes finished goods, semi-finished goods, raw materials, supplies kept in waiting, and some of the work in progress. For example, test scripts waiting to be executed by the testing team. Defects, Repairs, Rejects: Any product or service deemed unusable by the customer or any effort to make it usable to the original customer or a new customer. For example, errors found in the source code of a payroll module by quality control team. Motion: A waste due to poor ergonomics of the workplace. For example, Finance and accounts team sit on the first floor, but invoices to customers are printed on the ground floor causing unnecessary personnel movement. Over-processing: Additional process on a product or service to remove unnecessary attribute or feature is over-processing. For Example: a customer needs a bottle and you deliver a bottle with extra plastic casing; a customer needs ABEC 3 bearing and your process is tuned to produced more precise ABEC 7 bearings, taking more time for something the customer doesn’t need. Waiting: When a part waits for processing, or the operator waits for work, the wastage of waiting occurs. For example, Improper scheduling of staff members. Transport: When the product moves unnecessarily in the process without adding value. For Example: a product is finished and yet it travels 10 kilometers to the warehouse before it gets shipped to the customer. Another example: an electronic form is transferred to 12 people, some of them seeing the form more than once (i.e., the form is traveling over the same ‘space’ multiple times). Next, we will look at LEAN wastes other than the 7 types of waste.

1.23 Other Lean Wastes

Some Lean experts talk about additional areas of waste: Underutilized skills: Skills are underutilized when the workforce has capabilities that are not being fully used toward productive efforts; people are assigned to jobs in which they do not fit. Underperforming processes: Automation of a poorly performing process. Improving a process that should be eliminated if possible (for example, the product returns department or product discounts process). Asymmetry in processes that should be eliminated (for example, two signatures to approve a cost reduction and six signatures to reverse a cost reduction that created higher costs in other areas). Let us now examine an exercise on identifying the waste type.

1.24 Identifying the Waste Type Exercise

Let us identify the types of waste from the following examples. Materials are air-freighted into a company for the Materials Requirement Planning (MRP) deadline on the first day of the month. The materials then sit in the warehouse for three weeks before they are used. Click the button to know the answer. Payment from the customer is not received on-time because the customer claims the information on the bill-of-lading, invoice, and order do not match. Click the button to know the answer. An inspector rejects blemished parts observed under a microscope, when the specification allows for blemishes not visible from three feet away. Click the button to know the answer. By the time the work-in-process piles on the shelves and carts reduce, some assemblies done according to the previous revision become unusable. Click the button to know the answer.

1.25 Lean Process

We will now learn about the Lean Process. There are five steps in the process of lean implementation. They are Identify value, Value Stream Mapping, Create Flow, Pull, and Perfection. Click each step to know more. The first step is to identify value from the customer’s perspective. The second step is to perform value stream mapping. This helps you in mapping the path and identifying all the activities involved in the product or service. The third step is to make the value stream steps flow to ensure a continuous flow of products or services. The fourth step is to let the customer pull the products. The last step is to seek perfection, which is complete elimination of Muda.

1.26 Lean Process - Identify Value

We will cover each step of the Lean process in the next few topics. We will now learn about the first step, Identify value. To implement Lean to a process, it is important to determine what the customer wants. Once this is done, the process should be evaluated to identify what it needs to possess to meet customer requirements. The next screen will focus on the next step of the lean process, value stream mapping.

1.27 Lean Process Value Stream Mapping

Value stream mapping is a visualization tool to map the path and hence identify all the activities involved in the product or service. All the activities of a product or service are mapped on a paper using flowcharts. This helps in identifying and eliminating or reducing non-value-added activities. Any organizational activity can be classified into three types, Value added activities (VA), Non-value added activities (NVA), and Necessary, but Non-Value Added Activities Click each type to learn more. Value-added activities add value to the process and the customers are willing to pay for them. They add value in the making of a product and hence add value to the customer who will use the final product. For example, printing is the activity that provides manufacturing details to the customers, which in turn helps in the decision making of purchasing the unit. Non-value-added activities are activities that do not add any value to the product as perceived by the customer, and for which the customer is not willing to pay. For example, any delay in the raw material procurement. Workers waiting for the raw materials to begin the production does not add value to the process. Necessary, but Non-Value Added Activities are the activities required by the process. However, they do not add value to the customer’s perceived value. For example, quality check or inspection does not contribute to the product directly, however it is necessary until the process can be improved to the point where inspection can be eliminated.

1.28 Lean Process Flow Pull and Perfection

Here we will focus on the last three steps of the Lean process, Create Flow, Pull and Perfection. Click each step to know more. Create Flow—It is essential that a product or service moves through a business system in a continuous flow. Any process, which stops or reduces the flow is a non-value-adding activity and hence is a waste. Pull—Instead of making the product or sales based on an estimated sales forecast, the business system makes the product or service as the customer demands for it. This has many advantages such as decrease in cycle time, reduced finished inventory, reduced work-in-progress, stability in price, and smooth flow of the process. Perfection—Perfection is the complete elimination of Muda or waste so that all the activities along a value chain add value to the process. This also means that an organization should stop looking at the competitor market and should establish a perfect system.

1.29 Pull vs. Push

We will now discuss the differences between Push and Pull processes. An organization can adopt either of these processes depending on the requirement: Contrary to a Pull process, in a Push process, the first step is to forecast the demand for a product or service. The production line then begins to fill this demand and produced parts are stocked in anticipation of customer demand. An example of this concept is a garment manufacturer produces 200 shirts based on expected demand and then waits for customer orders. Note that the demand is expected and not actual. Discounts offered to customers by big retailers are examples of the Push process. If the garment company adopts a Pull process instead, it would start making the shirts only after receiving a confirmed demand from customers. Note that although the Pull approach seems better, it is not applicable to all situations. For example, a pharmacy uses a Push process. Let’s next discuss the theory of constraints.

1.30 Theory of Constraints

Every process has a limiting constraint or bottleneck. The Theory of Constraints or TOC (pronounce as T-O-C) is a tool to remove bottlenecks in a process that limit production or throughput. Once the process value stream is mapped, follow the five steps of the TOC methodology. These five steps form a continuous improvement cycle. Click each step to know more. The first step is to identify the constraints in the system or process. A constraint limits the rate at which the business achieves its goals. The second step is to exploit the system’s constraint. This refers to deciding how to exploit the constraint. It also involves deciding how to make improvements to the throughput of the constraint so that it works to its full capacity. In the third step, subordinate the rest of the process to the decisions taken in Step 2. In other words, align the whole process or systems support the decisions made in Step 2. In the fourth step, you must elevate the system's constraint and if the constraint still exists, consider further actions to resolve it. In the last step, if the constraint is broken or resolved, go to Step 1 and find a new constraint.

1.31 Theory of Constraints - Example

Let us look at an example for the TOC methodology in this screen. The three sub-processes in the packing process are coding or printing, filling, and sealing. The data for the 3 sub-processes are observed and collected as number of units produced in an hour. The data is as follows: Coding or Printing is 900 units per hour. Filling is 720 units per hour and Sealing is 780 units per hour. How can you implement the TOC methodology in this example? Let us build the TOC map for this example. The first step in the TOC methodology is to identify the constraint. Data reveals that the output per hour from the filling process is 720. This is the constraint in the system. In the second step, the constraint is exploited by analyzing the performance using data. To break the constraint, a repair and maintenance personnel can be assigned to maintain the filling machine on a daily basis. In the third step, the other fixes in the repair and maintenance function are made as subordinate decisions to the one taken in Step 2. In this example, carry out the maintenance of the filling machine. In the fourth step, the constraint is elevated by implementing the decisions. In this example, remove the damages from the filling machine. The next step is to go back to step one and identify the next system constraint. As per the data collected after implementation of the first cycle of the TOC, sealing can be identified as the next system constraint.

1.32 Theory of Constraints - Example

Let us now analyze the data before and after TOC implementation in this example. The number of units produced per hour before implementing the TOC in coding or printing process was 900 units, filling process was 720 units, and sealing process was 780 units. After implementing the TOC, the number of units produced per hour for the filling process increased to 840 from 720 units.

1.33 Topic 3 - Design for Six Sigma

In this topic, the concepts within Design for Six Sigma or DFSS are discussed.

1.34 Design for Six Sigma

DFSS or Design for Six Sigma is a business process methodology that ensures that any new product or service meets customer requirements and the process for that product or service is already at Six Sigma level. DFSS uses tools such as Quality Function Deployment or QFD and Failure Mode and Effects Analysis or FMEA. DFSS can help a business system to introduce an entirely new product or service for the customer. It can also be used to introduce a new category of product or service for the business system. For example, an FMCG company plans to make a new brand of hair oil, a type of product already in the market. DFSS also improves the product or service and adds to the current product or service lines. To implement DFSS, a business system has to know its customer requirements. DFSS can be used to design a new product or service, a new process for a new product or service, or redesign of an existing product or service to meet customer requirements. We will now learn about Quality Function Deployment or QFD, which is one of the DFSS tools.

1.35 DFSS Tools - Quality Function Deployment

QFD, also called Voice of Customer or VOC or House of Quality, is a predefined method of identifying customer requirements. It is a systematic process to understand the needs of the customer and convert them into a set of design and manufacturing requirements. QFD motivates business to focus on its customers and design products that are competitive in lesser time and at lesser cost. The primary learning from QFD includes which customer requirements are most important, what the organization’s strengths and weaknesses are, where an organization should focus their efforts, and where most of the work needs to be done. To learn from QFD, the organization should ask relevant questions to customers and tabulate them to bring out a set of parameters critical to the design of the product. Apart from understanding customer requirements, it is also important to know what would happen if a particular product or service fails when being used by a customer. It is necessary to understand the effects of failure on the customer to ensure preventive actions are taken and to be able to answer the customers in the event of failure. We will look at another DFSS tool, Failure Modes and Effects Analysis or FMEA.

1.36 DFSS Tools - Failure Modes and Effects Analysis

Failure Modes and Effects Analysis or FMEA is a preemptive tool that aids a system in the identification of potential pitfalls at all levels of a business system. It helps the organization to identify and prioritize the different failure modes of its product or service and determine what effect the failure would have on the customer. It helps in identifying the critical areas in a system where the organization can focus its efforts. Note that while FMEA enables identification of critical areas, it does not offer solutions to the identified problems. Let us look at the varieties of FMEA such as DFMEA and PFMEA.

1.37 PFMEA and DFMEA

PFMEA stands for Process Failure Mode and Effects Analysis and DFMEA stands for Design Failure Mode and Effects Analysis. PFMEA is used on a new or existing process to uncover potential failures. It is done in the quality planning phase to act as an aid during production. A process FMEA can involve fabrication, assembly, transactions, or services. DFMEA is used in the design of a new product, service, or process to uncover potential failures. The purpose is to find out how failure modes affect the system and to reduce the effect of failure on the system. This is done before the product is sent to manufacturing. All design deficiencies are sorted out at the end of this process. Let us next understand FMEA Risk Priority Number.

1.38 FMEA Risk Priority Number

FMEA Risk Priority Number or RPN is a measure used to quantify or assess risk associated with a design or process. Assessing risk helps identify critical failure modes. Higher the RPN, higher the priority the product or process receives. RPN is a product of three numbers, Severity of a failure, Occurrence of a failure, and the Detectability of a failure. All these numbers are given a value on a scale of one to ten. The minimum value of RPN is 1 and the maximum value is 1,000. A failure mode with a high occurrence rating means the failure mode occurs very frequently. A mode with a high severity rating means that the mode is really critical to ensure safety of operations. A mode with a high detection rating means that the current controls are not sufficient. We will now look at the FMEA table.

1.39 FMEA Table

The FMEA table helps plan improvement initiatives by underlining why and how failure modes occur and helps organizations plan for their prevention. Typically, FMEA is applied on the output of root cause analysis, and is a better tool for focus or prioritization as compared to multivoting. One important aspect of FMEA is that it does not need data. Experts in a particular area can form the FMEA table without having to look at data from any source. In functions such as Human Resources, the FMEA table is very useful as there might not be much data available to the problem solving team. The sample FMEA table is given on the screen. Please go through the contents for better understanding. Let us now have a look on severity of risk priority number and scale criteria.

1.40 RPN and Scale Criteria - Severity

Let us first discuss Severity. Severity refers to the seriousness of the effect of the failure mode or how critical the failure mode is to the customer or the process. The severity of a failure mode is rated on a scale of 1 to 10 using a severity table. Different industries follow different structures for the severity table. A high severity rating indicates a mode is critical to operational safety. For example, a team working on FMEA of a radioactive plant may insert “fatal” as the effect with rating 10. Another example is the Severity table for a sports team. The team manager wants to rate the severity of failure of the team in an upcoming game. She might rate it at 9 given that the team would lose a big sponsorship should they face defeat, which could in turn be hazardous to the teams’ future. Shown here is a generalized table of severity. The Severity rating can never be changed. For example, if a mode has a rating of 9 before improvement, it will continue to have a rating of 9 after improvement too. Let us next look at occurrence of RPN and scale criteria.

1.41 RPN and Scale Criteria - Occurrence

Occurrence is the probability that a specific cause will result in the particular failure mode. As with severity, occurrence is rated on a scale of 1 to 10 based on a table. Like the severity table, higher the occurrence of a failure, higher is its rating. Again, this table might vary depending on the industry and scenario. Sometimes, the project team can use data here if available. Based on past data, the probability of occurrence of a failure can easily be rated. Shown here is a generalized table. Let us next look at detection of RPN and scale criteria.

1.42 RPN and Scale Criteria - Detection

Detection is the probability that a particular failure will be detected. The table shown here is again a generalized one. The rating here is bit different from severity or occurrence. Higher the detectability of a failure, lower is its rating. This is because if the failure can easily be detected, then everyone would know of it and therefore there would be less or no damage. For example, if detection is impossible, the failure is given a rating of 10. Please note that at the start of a Six Sigma project, the failure mode is given a relatively high detection rating. Let us look at an example of FMEA and RPN.

1.43 Example of FMEA and RPN

In this example, a bank wants to recognize and prioritize the risks involved in the process of withdrawing cash from an ATM. It can be observed from the table that not having a control in place for network issues has the highest RPN. This is due to the detectability for a network issue being very low. The next set of information in the table shows the action taken by the bank’s management to address the failure modes. Following the implementation, the new RPN is calculated retaining the severity level at 9. This is because the actions were not directed at reducing the severity but at the causes of failure. It can be seen that the new RPN is much lower, and the risk for both causes has been mitigated.

1.44 Quiz

Following is the quiz section to check your understanding of the lesson.

1.45 Summary

Let us summarize what we have learned in this lesson. Six Sigma is a highly disciplined process that focuses on developing and delivering near-perfect products and services, consistently. Lean refers to creating more value for customers with fewer resources. Lean Six Sigma is the methodology that combines the best of both lean concepts and Six Sigma methodology and tools. DFSS ensures that a new product or service meets customer requirements and that a process is at Six Sigma level using tools such as QFD and FMEA. The FMEA table helps in planning improvement initiatives by underlining why and how failure modes occur and planning for their prevention.

1.46 Thank You

With this, we have come to the end of this lesson. Let us learn about Define phase in the next lesson.

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Certified Lean Six Sigma Green Belt 30 Apr -29 May 2021, Weekdays batch Your City View Details
Certified Lean Six Sigma Green Belt 15 May -13 Jun 2021, Weekend batch New York City View Details
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