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# Six Sigma Part 1

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### Six Sigma Part 1

1. 1. Six Sigma Part 1 Hill Farmhouse 20 Chishill Road Heydon Royston Herts SG8 8PW Tel: 01763 837111 Fax: 01763 837223 www.wdpconsulting.com wdp consulting six sigma
2. 2. Contents – Part 1 Introduction Six Sigma Model Project Management Process Mapping Measurement Statistical Thinking Basic Statistics Lean Operation Leading Teams wdp consulting six sigma
4. 4. garage becomes far easier. The aim of Six Sigma is to reduce the width of the car such that two car widths would fit into the garage. This would represent ‘Six’ sigmas. Achieving this would, in process terms, reduce the number of defects to as low as 3.4 defects per million opportunities (DPMO). Understanding variation Variation around target Six Sigma Three Sigma Measured Target Characteristic Lower Spec Upper Spec 6σ Six Sigma Model The generic Six Sigma process follows the accronym DMAIC. Define the goals of the existing system: - choose a process or product that is critical to business success Measure the current system: - select characteristics critical to quality, map and measure the process. Analyse the system: - use benchmarking to identify potential areas for improvement. The simple quality tools and basic statistics are used at this stage. Improve the system: - determine how to significantly change the process and reduce the defect levels. More advanced statistical tools such as Experimental Design may be used at this stage. Control the new system: - once the new process is up and running, standardise and monitor to ensuring that the gains are realised. This may involve the use of Statistical Process Control (SPC). wdp consulting six sigma
5. 5. Six Sigma Training. Typical Six Sigma training programmes rely strongly on statistical methods. These are taught to proposed project leaders (Black Belts) usually in four one week sessions with one session taking place each month. This is complimented by a project applying the techniques learnt. Green Belts (project team members) would receive two, one week training sessions. Six Sigma tools Subjects covered FMEA Seven Quality Tools Design of Experiments Mistake Proofing Statistical Process Taguchi Methods Control Benchmarking QFD Hypothesis Testing Measurement Systems Analysis T-Tests Basic Statistics ANOVA Reliability Engineering Response Surfaces Regression Analysis 6σ Six Sigma Standards Unfortunately there is no standard describing Six Sigma and each provider offers a different view and curriculum. Some companies say a Black Belt qualifies having successfully completed two projects, some say three, others are happy to take your money, giving accredition to those who have simply completed their training course. Motorola, itself, has additional Yellow belts and one consultancy even has the position of Brown belt. One company has combined Six Sigma and Lean Manufacturing to create Lean Sigma! The American Society for Quality (ASQ) has produced its ‘Body of Knowledge for Black Belts’ although this is by no means accepted as standard. Nothing New under the Sun? Those who have lived through quality initiatives during the last twenty years will recognise many of the concepts. So why is this different? In simple terms, there is little difference except many of the successful quality techniques have been brought together. In addition, there is focus on projects with measured improvement, something which has for many years been advocated by Juran. wdp consulting six sigma
6. 6. So what is the secret? Advocates of Six Sigma would probably say that it is the correct application of the steps and tools. However, it is interesting to note that GE along with many others had past initiatives using tools similar to those of Six Sigma that gradually faded out. The key to Six Sigma is that the leadership at the highest level of an organisation drives it. As with any successful initiative, Six Sigma requires top management commitment, provision of appropriate resources and appropriate training but certainly not four weeks of statistical methodology. A positive aspect is that, in most cases, Black Belts are released from their day-to- day work to be full time on projects. In GE, 40% of executives’ incentives are tied to key Six Sigma achievements. In Motorola, Black Belts receive bonuses for project success. Team skills? Knowledge of teamworking and facilitation is essential, and basic project management skills will be needed for any projects that are developed. More advanced tools can be picked up as and when they are needed. Although individuals are trained, it is highly unlikely that they will be able to achieve their project aims without the help of others. Benefits of Six Sigma As with any improvement methodology for which the appropriate resources and commitment are applied the benefits can be enormous. For many of the large companies small savings can become huge when applied worldwide. On a smaller scale these improvements may not reach billions of dollars but can still be significant. For example; a manufacturer of plastic packaging had tended to make the bags overlarge to avoid the customer receiving a bag that was too short for the application. By using experimental design the factors affecting bag length were understood and the production was able to reduce the average bag length without creating risk for the customer. In fact, the process was more stable and meant that the customer was even less likely to get an undersized bag. The savings on material amounted to about £0.005 per bag. Not a huge saving, except that the company produced 40 million bags per year giving a saving of £200,000 per year. The benefits of Six Sigma are often talked of in terms of savings to the company. However, it should always be remembered that the original aim of Six Sigma was to improve customer satisfaction, reduce errors, improve products and processes and as a result save money. wdp consulting six sigma
7. 7. Benefits of Six Sigma Produces significant bottom line results Requires and gets top management support Provides better products and services for customers Develops and empowers employees Works in all parts of the business Sustains gains over time Uses previous tools 6σ Six Sigma Pitfalls Six Sigma cannot be introduced as something that only impacts in one area eg. manufacturing. If it is to be successful it has to be applied throughout an organisation. The key to achieving this is to ensure that Six Sigma is aligned and woven into the organisational strategy, objectives and plans. Although the tools dominate the training it is not simply enough to have the tools without management commitment to changing the way the organisation operates. Six Sigma is in essence a platform for change. Six Sigma Success Advert for Satellite Broadcasts Oct 2001 ‘Dr Harry will show why successful installation of Six Sigma has little to do with statistics but, rather, with leadership setting performance goals, establishing valid deployment plans and defining execution tactics…..’ 6σ wdp consulting six sigma
8. 8. Six Sigma Model The DMAIC model is intended to be cyclical i.e. the improvement cycle never ends. Define Control Measure Improve Analyse Define, Measure, Analyse, Improve, Control, (Transfer) Define the Customer, their Critical to Quality (CTQ) issues, and the Core Business Process involved. • Define who customers are, what their requirements are for products and services, and what their expectations are • Define project boundaries the stop and start of the process Define the process to be improved by mapping the process flow Measure the performance of the Core Business Process involved. • Develop a data collection plan for the process • Collect data from many sources to determine types of defects and metrics • Compare to customer survey results to determine shortfall Analyse the data collected and process map to determine root causes of defects and opportunities for improvement. • Identify gaps between current performance and goal performance • Prioritise opportunities to improve • Identify sources of variation Improve the target process by designing creative solutions. • Create innovate solutions using technology and discipline • Develop and deploy implementation plan wdp consulting six sigma
9. 9. Control the improvements to keep the process on the new course. • Prevent reverting back to the "old way" • Require the development, documentation and implementation of an ongoing monitoring plan Institutionalise the improvements through the modification of systems and structures. Some companies add Transfer after Control. That is; transfer the learning to other relevant areas of the company. wdp consulting six sigma
10. 10. Six Sigma Checklist (adapted from P.S. Pande “The Six Sigma Way”) Define Has the project team …. 1. Confirmed that the project is a worthwhile improvement priority for the organisation and is supported by the business leaders? 2. Been given a brief project rationale explaining the potential impact of the project on customers, profits and its relationship to the company’s business strategies? 3. Composed and agreed a two to three sentence description of the situation as currently seen? 4. Prepared a goal statement defining the results expected from the project, with a measurable target. (note: results not solution)? 5. Completed a Team charter including a list of constraints, team membership, a preliminary plan and schedule and process scope? 6. Reviewed the charter with the Champion / Sponsor and confirmed their support? 7. Identified the primary customer and key requirements of the process being improved and created a SIPOC diagram of the areas of concern? 8. Prepared a detailed process map of the areas of the process where the initial measurement will be focussed? Measure Has the project team…. 1. Determined what needs to be understood about the process and where to go to get the answer? 2. Identified the types of measures to be collected and have a balance between effectiveness / efficiency and input / process / output? 3. Developed clear, unambiguous operational definitions of the things to be measured? 4. Tested the operational definitions with others to ensure their clarity and consistent interpretation? 5. Made a clear, reasonable choice between gathering new data or taking advantage of existing data? 6. Clarified the factors needed to facilitate the analysis of the data? 7. Developed and tested data collection forms to ensure the collection of consistent and complete data? wdp consulting six sigma
11. 11. 8. Identified an appropriate sample size and sampling frequency to ensure a valid representation of the process under study? 9. Prepared and tested the measurement system, including training of collectors and assessment of data collection stability/ 10. Used data to prepare baseline process performance measures, including proportion defective and yield? Analyse Has the project team … 1. Examined the process and identified potential bottlenecks, disconnects and redundancies that could contribute to poor performance? 2. Conducted a value and cycle time analysis, locating areas where time and resources are devoted to tasks that are not critical to the customer? 3. Analysed data about the process and its performance, identified reasons for variation in the process and identified possible areas for improvement? 4. Evaluated whether the project should focus on process design or redesign, as opposed to process improvement and confirmed the decision with the Champion / Sponsor? For Process Design / Redesign 5. Ensured that the key areas of the process are understood so that a new process can be created to meet the needs of the customer efficiently and effectively? For Process Improvement 6. Investigated and understood whether they are dealing with Special Cause or Common Cause variation? 7. If Special Cause, identified and verified the root cause? 8. If Common Cause, identified the significant factors influencing the variation in the process? Improve Has the Project team … 1. Created a list of innovative ideas for potential solutions? 2. Identified clear criteria for a successful solution? 3. Made a final choice based on the above criteria? wdp consulting six sigma
12. 12. 4. Verified that the solution will give the required improvements? 5. Agreed with the Champion / Sponsor and received the go-ahead? 6. Developed a plan for piloting and implementing the solution including a pilot strategy, action plan, results assessment, schedule etc. 7. Evaluated the results and confirmed that the results in the Goal statement can be achieved? 8. Identified and implemented refinements to the solution based on lessons learnt from the Pilot? 9. Created and put in place a plan to completely implement the solution? 10. Considered potential problems and unintended consequences of the solution and developed preventive and contingent actions to address them? Control Has the Project team … 1. Compiled results data confirming that our improvement has achieved the Goal defined in the Team charter? 2. Selected on-going measures to monitor performance of the process and continued effectiveness of the solution? 3. Determined key charts / graphs for a process ‘Scorecard’ on this process? 4. Prepared all essential documentation of the revised process, including key procedures and process maps? 5. Identified an ‘owner’ of the process who will take over responsibility for the improvement and for managing continuing operations? 6. Documented the team’s work and data collected during the project? 7. Forwarded other issues / opportunities, that were identified during the project, to senior management? 8. Celebrated the work and efforts of the team? wdp consulting six sigma
13. 13. Project Management Introduction These notes have been compiled to give the reader an introduction into project management skills. It should be used as a reference point and as a guide. It cannot tell you exactly how to manage projects; that is down to an individual’s style and aptitude. What it does do is give some key pointers, and things to think about. The picture below shows a juggler. Project management is often like juggling. A good juggler will have an awareness of their own ability, the mood they are in when juggling, the people who may be juggling with them and those who may just be watching. The balls they have in the air relate to different things they are trying to keep in balance at any one time. At all times the juggler must be aware of where the balls are, and will be catching and throwing them up in the air again so they do not fall in the ground. As a project manager, you will have to do very similar interventions, albeit rarely with balls!! What you should not do is expect the impossible, how many jugglers have you seen spinning 20 plates at the same time as juggling 5 chainsaws? wdp consulting six sigma
14. 14. Definition of Project Management Projects come in different forms. Many people think of a project as being the Channel Tunnel or British Library or other large engineering projects that hit the news headlines, usually for being grossly overspent!! Projects can be both large and small. There are a variety of definitions of a project, which include: - “A human activity that achieves a clear objective against a timescale. Projects nearly always have the following characteristics - one clear objective, a fixed timescale, a team of people, no practice or rehearsal, and change” “A human endeavour that creates change; is limited in time and scope; has mixed goals and objectives; involves a variety of resources; and is unique” All projects have to be managed. Project management has been described as, “the process of planning, controlling, and managing people as a temporary team. This is no different in Six Sigma. Different Types of Project “Many traditional definitions of projects assume that the objectives of a project, and the methods of achieving them, are well understood throughout the project.” Projects can be judged against two parameters: “whether the goals are well defined, and whether the methods of achieving them are well defined”. This concept leads to the definition of four types of project, see diagram below: - Type 2 Project Type 4 Project Greater No Research & chance Product Organisational developmentt of failure change Methods Well Defined Type 1 Project Type 3 Project Applications Engineering software development Yes Greater chance of Yes No success Goals Well Defined Type one projects: goals and methods are well-defined - typically large engineering projects. Type two projects: goals are well defined but the methods of achieving them are not e.g. product development projects. wdp consulting six sigma
15. 15. Type three projects: goals are not well defined but the methods are - e.g. software development projects where the user requirements are hard to specify. Type four projects: neither the goals nor methods are well-defined - e.g. typically organisational development projects. Some people argue that the best way of achieving these projects is to move the project into the type three or two category (preferably type two), and then into the type one category as quickly as possible, thereby fixing the goals and methods. Milestones become key decision points and configuration management is suggested as a way of managing this. The conventional view of projects as complex, but well defined, sequences of activities to deliver clearly defined goals and objectives may be invalid for a large number, if not the majority, of projects. Whatever the type of project, one of the first things the project manager must do is to identify the external environment, particularly who the stakeholders are, in order to build appropriate relationships and satisfy competing demands. The Development of Projects Projects can come from a variety of sources. They may be part of the logical strategy of an organisation and be created on an annual basis, programmed into the ongoing efficient running of an organisation, and many large projects will often fall into this category. There are also other sources that may drive projects. For example, an operation manager may see the scope to introduce technology to make the operational process much more efficient. This will inevitably create a project to implement the technology. External influences can also create the need for projects. If there are plans to change legislation then organisations often have to react to this, and create projects to deal with the external changes. Above all else customer demands may create the need for projects. Some of these demands will be focused in an organisation’s annual strategy, but others will be much more immediate. For example, if service provision falls down to an extent that a great deal of bad publicity is created, then customers will place demands upon the organisation to make changes in the way the service is delivered. There are four key stages in the life of a project. PROJECT LIFE SPAN BIRTH MATURITY Proposal and Implementation and initiation control WDP GROWTH DEATH Design and approval Finalisation & control & evaluation wdp consulting six sigma
16. 16. The first is the Birth stage. This will be where the seeds for the project are sown, and the outline proposal documentation is drawn up. This may be the end of the project as it quickly becomes apparent that it is a not feasible. However, if the project passes successfully through the first stage then it moves into the Growth stage. During this phase the project design is made clear, the scope of the project agreed and people understand the likely impact on resources. This is followed by the Maturity stage of the project wherein the plans will be implemented, monitored and controlled. Even at this stage of the project, progress may and should be aborted if things change so radically as to make the project no longer feasible. One of the worst crimes of the project manager is to ‘press on regardless’. Analogies can be drawn with the Titanic, where despite iceberg warning the ship continued on at high speed, only to suffer drastic consequences. The Death stage of the project marks the end of the project, hopefully completed, and will be the time that project evaluation and learning takes place. Defining The Project As already described, the definition of the project will be paramount to a successful completion. There are four key elements to this: - Scope, Stakeholders, Self and Team. Charter / Scope Writing a scope document that incorporates the necessary information will mean that there will be a formal agreement between Project Manager and the Project Champion as to what should be delivered. This document will become ever increasingly useful to the Project Manager as the project progresses. It should be a document that is constantly referred to and ensures that all work is focused and that only the right amount of work is undertaken, thereby ensuring an effectively managed project. Within Six Sigma this known as the Project Charter. Areas to be considered: Project Title: this should give others a quick view of the project and use key words or phrases. Project Leader: who is leading the efforts? Champion / Sponsor: who is responsible for “creating the environment” for the team leader and team to undertake the project. Project Start date: the date the project formally started. wdp consulting six sigma
17. 17. Project End date: the Champion will probably set the anticipated project end date. The time allowed for the project should give enough time to complete the project given its complexity and current business conditions. Cost of Poor Quality: quantifying the total cost of quality can be difficult but there may be information on such things as scrap produced, excess hours spent etc. This will give an idea of the potential savings and size of the project. Process: which process is to be improved? Why does it need improving? How will it affect the customer? I.e. what is the need for this improvement? Project boundaries: the team cannot solve everything. The team needs clear boundaries to help it focus on the extent of the project. Project objectives: what is the project expected to achieve? Are the objectives SMART? OBJECTIVES Specific Measurable Achievable WDP Relevant Time based Process Measurements: what are the measures that will determine the success of the project? Team members: who should be part of the team? Subject matter experts? Project Milestones: what are the major milestones within the projects? Once the scope is defined, the process of scope management begins and this is covered later. Stakeholders The management of a project’s “stakeholders” means that the project is explicitly described in terms of the individuals and institutions that share a stake or an interest in the project. Stakeholders can include a variety of people, often outside the wdp consulting six sigma
18. 18. control of the project manager and therefore presenting serious management problems. It is only by identifying what is important to each of the stakeholders in terms of both hard and soft expectations, that the project manager can develop options for managing any interference or conflicting expectations and for managing the project to ensure the stakeholders are satisfied at its conclusion. There are few prescribed tools and techniques for the management of stakeholders, and what does exist is often based on simple forms identifying the stakeholders and their level of power and interest, as demonstrated in the model below: Level of interest Low High Minimal Keep Low effort informed Power Keep Key High satisfied players It is critical that all stakeholders are identified and none overlooked. Only in this way will all external influences be considered. While deciding the approach to take regarding stakeholder management, it is necessary to look at the project life cycle, and dovetail the two accordingly since stakeholders may appear during the life of the project. Self Only by knowing him or herself / herself will the Project Manager ensure that they make an effective contribution to the project. By being realistic about this, and possibly using some assessment tools to aid the process, the Project Manager will be able to see their own strengths and weaknesses. This information can be used to map how this might affect the project and then the necessary action can be taken to ensure the project does not falter due to a weakness in a key skill area such as planning. The following questions will be useful in assessing this: - What experiences have you had? What are you good at? wdp consulting six sigma
19. 19. What are you not so good at? What do you want to develop? How will you measure this? The strengths and weaknesses identified should then be matched against expected role and performance. Strengths are often easier to build on and identify whereas weaknesses are often hard to admit to, accept and then either develop or resolve. The development of a weakness may well take some time, and so the project manager should seek to overcome a weakness by using the skills of others where necessary. Admitting to the weakness does not have to be a part of this, although doing so may well allow the designated person to act as a mentor for the development of the skill in question. Teams Teams are an essential feature of the work pattern of almost any organisation. Once in a team, the people within it influence each other in many different ways. The team may even develop its own hierarchy and its own leaders. Both may be different to that of the organisation from which it originates. Group pressures can have a major influence on the behaviour of individual members within that team and their performance to the team’s overall aims. The activities of the team can also be closely associated with the process and style of leadership adopted by the leader / facilitator of the team. wdp consulting six sigma
20. 20. There are two different types of group: formal and informal. Formal groups are created to achieve specific organisational objectives and concerned with the co-ordination of work activities. People are brought together on the basis of defined roles and the structure of the organisation. The nature of the task to be undertaken is an important feature of the formal group with goals being identified by management and certain ground rules, relationships and perhaps norms of behaviour established. Informal groups are based more on personal relationships and agreement of group members than on defined role relationships. These groups tend to satisfy psychological and social needs, not necessarily related to the task being undertaken. These groups tend to devise ways of attempting to satisfy member’s affiliation and other social motivations that are perhaps lacking in the work situation. The membership and roles of informal groups can cut across formal structure. It is very unusual for an informal group to be exactly the same as a formal group. Understanding the informal group network can be critical in determining how to facilitate formal teams. The performance of a team is essentially its effectiveness. This is influenced by: (1) the givens - the team, the task, the environment (2) the intervening factors - leadership / facilitation style, motivation, processes and procedures leading to (3) the outcomes - productivity and member satisfaction. The Givens The size of the team is an important factor in its performance. As team size increases, problems arise with communication and co-ordination. If a team becomes too large it may split in two sub-teams with friction developing between them. The optimum performance of team size is probably five to seven people. Teams with more than seven or eight permanent members start to split into sub-groups, and can under perform. For larger projects it therefore makes sense to have teams and sub- teams for different work packages, with the occasionally ‘whole project’ team briefings to manage communication. Compatibility of members of a team is also important. The more homogenous the team in terms of background, interests, attitudes and values, the easier it is to promote cohesiveness. Differences in personality or skills in the team may actually complement each other and help the overall performance. However, they can also cause difficulties and conflict may arise when members are in competition with each other. If teams are too cohesive, they can suffer the phenomenon of ‘group think’, where people are so in tune with what the others are thinking they do not always see the broader picture and may overlook something incredibly obvious. wdp consulting six sigma
22. 22. Team Development When examining the components of team performance, it is also important to consider team development. Teams, like individuals, have a growth cycle. The team will function differently at various stages of development, and performance expectations must be altered accordingly. A model that is frequently used splits the development into four stages:- Forming this is the initial stage of development. Participants can be anxious, testing to discover the nature of the situation, trying to discover what help is available from the leader or facilitator, and what behaviour is or is not appropriate. Participants try to discover the nature of the task, and the ground rules. Storming conflict begins to emerge between individuals or sub-groups; the authority of the leader, the make up of the group, indeed its purpose for existing is challenged. Discussion causes differences of opinion to emerge. BUILDING THE TEAM 4 stages of team development forming storming norming WDP performing motivation is key Task needs Balancing needs Group maintenance Individual needs needs Norming the group begins to harmonise; cohesion and unity begin to be experienced by participants; norms emerge for handling conflict; mutual support develops. Plans are made and work standards laid down. Communication of views and feelings begins to develop. Performing the group structures itself or accepts a structure that fits most appropriately a common task. Roles are established and accepted in relation to the task. The group begins to apply more of its energy to being effective in the area of its common task. This results in progress and achievement. Performance will improve if teams can ‘get through’ the first stages as quickly as possible. Teambuilding exercises may help with this, and should not be overlooked even if the team already know each other. It is also important to recognise that teams need to be maintained, and team-building exercises should not just be saved wdp consulting six sigma
23. 23. for the beginning of a team’s task, but undertaken at various intervals, as appropriate, throughout the life of the project. The Forming Stage During the initial stage of development, the primary concern of new team members is to be included. They typically wonder: ‘How do I fit here?’ ‘what’s expected of me?’ They may think that if they speak out they’re misbehaving, so they don’t express their negative feelings – they don’t want to rock the boat. They look to the facilitator for guidance and assistance. That can be the beginning of a long-term dependency. Here are some things you can do to encourage team responsibility from the start. Help the team develop ground rules, and explain their use. Encourage team members to assume responsibility not only for adhering to the ground rules, but also for enforcing them. Provide a mini lesson on how to intervene regarding breaking the rules: • make a statement or ask a question that describes the inappropriate behaviour, and correlate it to the ground rules. Example: Joe, one of our ground rules if no cheap shots. When Sarah offered her idea, you said ‘You need to get out of the office more, Sarah.’ • invite comment. This step isn’t always necessary, but it can be used to help someone recognise his or her behaviour and its effect on the team • request that the person change his or her behaviour to be more consistent with the ground rules, or suggest the desired behaviour. Example: What did you intend by that? Or, I felt that comment was a cheap shot. Would you be willing to hear how Sarah’s idea might work? Clarify roles Working with the team, define and spell out in specific terms (preferably written) the roles of facilitator, team member, and team leader. That not only establishes immediate ownership for the success of the team, but also individual responsibility for fulfilling roles and expectations. Check progress Team progress or process checks are an easy way to encourage team ownership of results and how the team works together to achieve them. Progress checks are led by the facilitator and are usually the last item on a meeting agenda. Each member is asked to respond to a few questions – such as; What did we do well? What did we not do well? What do we need to do differently the next time? The facilitator asks the questions one at a time. Team members take turns answering, and then the facilitator offers his or her view. The Storming Stage Once team members are oriented, they should focus on being heard and having control. At this stage, conflict is often evident. As facilitator, your focus should be on group dynamics and positive confrontation to help team members find workable ways to address their differences. This is the stage at which many teams (and facilitators) either make it or break it. wdp consulting six sigma
26. 26. Project Planning & Control SEQUENCE OF PLANNING Consider the ‘big picture’ Break the project into sub projects WDP Determine the relevant milestones Break each sub project down Clarify resources Project planning is a form of management, evolved and established to co-ordinate complex activities - some man-made ones still survive today, For example, the Egyptian pyramids. However it has not been until the later part of this century that many of the techniques have been developed, partly as a result of nations’ competition for supremacy in weapons and defence systems. Although variations exist, there is a core set of techniques that are commonly used. Before looking at the various ways in which plans can be developed it is worth understanding the sequence of planning. It is also worth noting that plans should be developed with the project team, and other relevant stakeholders. The plan should be targeted at its audience, which will often mean that different levels of a plan will exist. For example, senior people in the organisation will not be interested in the detail of the tasks to be undertaken, but they will be interested in the overall picture and some of the key milestones to be achieved. The methods and tools for planning projects can be as follows: - Work breakdown structure (WBS) this involves the division of an activity into sub activities and sub-sub activities in order to control the project effectively. It is something that provides better control of work definition; it allows work to be delegated in coherent and often independent packages; it allows work to be defined at an appropriate level for estimating and control; and it allows risk to be contained more easily. It simply follows the principle that when faced with a mountain, turn it into a series of molehills. Milestone plan this is a tool that allows the project manager to show how the intermediate deliverables build towards the final objectives of the project. It wdp consulting six sigma
27. 27. therefore allows different members of a project team to see the interfaces between their activity and others. MILESTONE PLAN WBS1 WBS2 WBS3 tasks activities (sub WBS3) WDP interdependencies milestone result path Milestones are useful to show the logical sequence of events, highlighting dependencies. Where these are not always clear, the milestone plan is likely to be much more broadly focused. Defining milestones can be a tricky task. They do not show how something is to be done, but what is to be achieved. An example of a milestone would be ‘arrival at work’, but not ‘when I have driven to work’; the reason for this is that you could arrive at work by bus should your car breakdown. This can get quite complicated, but the key issue is ‘what will have been achieved’. Once milestones have been defined a result path can be drawn to show the interdependencies between tasks, as we see illustrated here. Responsibility charts can be described as a matrix with tasks shown as rows and organisational resources as columns. Symbols are placed in the body of the matrix to represent the involvement of each resource type in each work element. This method can be invaluable in managing and allocating known tasks. If tasks are predictable they can be developed in advance, if not, as is often the case in open projects, they can be used over shorter time frames, but still providing a useful tool for the project manager. RESPONSIBILITY CHART Companies / Departments / Functions Resources / People WDP Milestones Activity / Task Roles / Responsibilities wdp consulting six sigma
29. 29. intensive whilst others will not be. OD projects by their very nature are less capital intensive, and the costs can often be, and are often, hidden - For example, people’s time (it is often just fitted in!!). The costs will frequently arise in the expertise bought in to assist with certain interventions. Complete cost predictability is therefore impossible until the tasks are known! QUALITY Give the customers what they want! Achieve by: Carefully developed & managed processes WDP An inbuilt attitude of mind ‘We never have time to do anything, but we always find time to do it twice!’ Quality can be managed through a variety of means. At the start of the project the manager should draw up a quality plan to define how quality will be achieved, how the company’s procedure will work on this project, and how the manager intends to assure and control quality. Quality assurance systems, such as ISO9000 are not a product standard, but a management standard system, relating to how quality is provided. It provides a framework of procedures with which to achieve quality, but it is a means to an end and should not be seen as anything more. It is geared to the achievement of quality of production, not the production of quality. In order to assure the quality of the project there needs to be a clear specification with defined standards, appropriately qualified people, periodic reviews and reasonable change control. A project handbook may well be used, either as part of the organisations approach to projects generally or specifically produced for major projects. Quality control is the process of diagnosis and cure. As the facility is erected and commissioned it is checked against the specification to ensure it is of the required standards, and any variances are eliminated. The activities by which this is done must be planned, tested, recorded and analysed. Techniques are employed to produce the best product and service possible - through constant innovation. Three tools that can be adapted from regular initiatives include the Cause and Effect diagram, Pareto's 80/20 rule and ‘Just-in-Time’ methodologies. wdp consulting six sigma
30. 30. RISK Outcome Simple Some New Process innovation Simple low risk high Medium High high high risk WDP complexity Affected by: Overcome by: technology - new and old avoidance - identify and time replan people - skills and deflection - pass the buck teamwork contingency uncertainty Risk management – There are probably five sources of risk, external-unpredictable; external-predictable; internal - technical; internal - non-technical; and legal. The techniques that can be used to identify these risks include - expert judgement; plan decomposition; assumption analysis; decision drivers’ analysis; and group brainstorming. These can then be reduced by avoidance, deflection or contingency planning. Whilst risks exist in every project, the above categories may not be appropriate to OD projects; For example, internal-technical risks may not be relevant to a quality improvement programme. Risk can be identified by using the simple table shown. Project Management Information Systems a PMIS is used for collecting data from across various functions, and analysing and presenting those data in a form suitable for all the parties involved in a project. The systems are used for planning and controlling projects, throughout the project management lifecycle, providing timely control information. The systems are also used for recording historical data for estimating future projects. Microsoft Project is an example of a computer software package that can help in the management of a project. It should not however be assumed that by purchasing such a system, a project will automatically be well managed and planned. A typical system has two key purposes, to act as a planning system and also as a control system - as illustrated below. THE THE PLANNING CONTROL SYSTEM SYSTEM • scope • purpose management data structured • organisation decision and information • time • resources direction • cost • quality • management wdp consulting six sigma
31. 31. This sort of system builds, and relies upon much of the data set-up in the ‘scoping tools and techniques’ (as illustrated in the previous diagram), and therefore the same arguments apply when considering their usefulness with open projects. Summary A key part of Six Sigma is the running of projects to achieve the improvements within a process or product. Thus, it is necessary to use the knowledge developed from running projects to help ensure that the Six Sigma project is successful. The key parts of the project are : Defining the Charter Selecting the most appropriate team Planning and monitoring the project steps using tools described Communication with all stakeholders Process Mapping wdp consulting six sigma
32. 32. A Process Map is a graphical representation of a process, showing the sequence of tasks or events using a number of symbols. (see appendix ). Mapping can be applied to anything from the movement of an invoice to the flow of materials in manufacturing or the steps involved in making a sale. You will discover that individuals will have a different understanding of what the map looks like and how the process works. Hence maps should be created by a team rather than by an individual. The objective of creating a process map is to help understand the process, highlight where problems exist and ultimately improve the process. A good map is the foundation for continuous improvement. What is a Process? A process is a set of steps/tasks/activities that have a beginning and an end. Another definition could be; a group of logically related tasks, decisions or activities which together produce a result or output. In its simplest format it can be seen as: INPUT PROCESS OUTPUT The process transforms the inputs into the outputs. This simple diagram can be expanded to include Suppliers and Customers. SUPPLIERS INPUTS PROCESS OUTPUT CUSTOMERS This diagram is sometimes referred to as SIPOC. Customers and Suppliers may be either internal or external to the organisation. A further development of the diagram brings in reference to Controls and Resources. CONTROLS SUPPLIERS INPUTS PROCESS OUTPUT CUSTOMERS RESOURCES Definitions: wdp consulting six sigma
33. 33. Process – any activity that transforms inputs into outputs Inputs – material and/or data transformed by the process to create the output Outputs – the results of the transformation of the inputs Controls – regulators or influences on the process Resources – people, equipment or material not transformed by the process Supplier – individual, department or organisation that supplies the inputs Customer – individual, department or organisation that receives the outputs In looking at a process for the first time it can be useful to list the elements under each of the S.I.P.O.C. This helps remind the team of aspects of the process that need to be considered. E.g. have they considered the requirements of all the customers listed? Suppliers Inputs Process Outputs Customers Requirements See Below Step 1: Step 2: Step 3: Step 4: Step 5: wdp consulting six sigma
34. 34. SIPOC Example Suppliers Inputs Process Outputs Customer s Manufacturer Copier Copies You O ffice Supply Company Paper File Toner O thers Making a photocopy Yourself Original Pow er Company Electricity Process Steps Remove Remove Put original Put original Adjust Adjust Press Press Close Lid Close Lid originals originals on glass on glass Settings Settings START START and copies and copies Levels of a Process Your position within an organisation will affect how you see a process. A process can be shown at a number of levels. High Level Process (Core Process) E.g. introduce new products to the market Identify Develop Develop Launch Market Need Product Production New Product Design Capability Within this there are Key Processes e.g. Launch Product. Key Process (Major Process) E.g. Launch Product Prepare Sales Train Sales Pilot Sales of Sell Literature Team New New Product Product Each of theses processes can be further broken down into Activities or Tasks. wdp consulting six sigma
35. 35. Sub-Process E.g. Prepare Sales literature Design Agree Print Distribute Brochure Design Brochure Brochure Activity / Task E.g. Design brochure Write Text Agree Prepare Produce Draft Layout Artwork Brochure If needed even each of these could be broken down further. It is important to agree from the start at which level the process is being considered. For most improvement situations, the more detailed activity / task level will be used. However, this may not always be the case. For example it may be decided that a radical overhaul of the method of identifying a market need is required. Whatever level is being considered, it is important that an accurate map of what currently happens is created. It is very tempting for teams to produce a map of what should happen according to procedures or what they would like to happen. Honesty is a key requirement before any real improvement can be made. Example A chemical process was showing high and at times irregular variability. When the Supervisors were consulted over this they had no answer even though some of the changes appeared to be shift related. It was only during conversations with operators that it became known that at the start of a shift, once the previous Supervisor had left, the new Supervisor got out his little black book and changed the process settings. Initially, the Supervisors denied they did this and it was only under pressure from Operators saying they did, that it was acknowledged. Once the Supervisors stopped changing the process that they were able to move forward and improve the process which ultimately led them to running a line for several days without any breaks or changes; a situation unheard of before. wdp consulting six sigma
36. 36. Link to Key Business Objectives There are many processes within an organisation, thus if significant improvements are to be made, then there needs to be an understanding of which processes are linked to which key business objectives. Amongst the key business objectives should be those that directly relate to serving the external customer. Make sure that the objectives are not purely internal. A decision making process (see Tools) can then be used to identify the most critical process i.e. the process having the greatest impact on the business objectives. Process Mapping Steps Step 1: Decide on the process to be mapped Step 2 Decide where the process begins and ends (boundaries) Step 3 List the outputs and identify the customers for these outputs Step 4 Determine the requirements for these customers Step 5 List the inputs and their suppliers Step 6 List the main activities and decision points in the process Step 7 Arrange these activities in their proper order, using arrows to show the direction of flow Step 8 Agree this represents the current ‘as is’ process Customers and Suppliers (Steps 3 – 5) In drawing the Process map it is important to recognise those who may have some interest in this process, i.e. customers, suppliers and other stakeholders. Think of a process that you are involved in: Who are your main customers? wdp consulting six sigma
37. 37. Do you know what their requirements are? Are your customers aware of what you can or cannot do for them? Who are your main suppliers? Do you know what their capabilities are? Are any of your customers also your suppliers? Do any other groups have an interest in your process? Too often organisations produce Process Maps without any reference to customer needs and expectations. Map the Process (Steps 6 – 7) In order to display the process than different methods may be used. Systems Flowcharting Operations Flowchart (See appendix for description) 10 20 30 40 wdp consulting six sigma 50
38. 38. Example: Washing dishes after a meal Clear dishes from table yes yes Food Dispo Put food on se of in bin dishes? food? No No Store food Stack dishes in dishwasher Add detergent Set dishwasher controls and turn on wdp consulting six sigma
39. 39. Improving the Process Map Simply getting a team to draw a Process Map can lead to the identification of areas for improvement. For example discovering output that goes nowhere or realising some things could be done earlier in the process. However, on studying the final Process Map it is necessary to ask whether or not this represents the ideal process flow. If the answer is no, then improvements must be made. In many cases it may not be possible to answer this question immediately and it is necessary to collect data from the process in order to identify areas for improvement. Measurement The measures chosen should relate to customer requirements or necessary controls required to ensure that the process works correctly. Typical areas of measurement might be: Effectiveness: output measures of your customer’s requirements Efficiency: measures of the amount of time, cost or labour Supplier’s effectiveness: how good is the input material or information? Process controls: how stable is the process? In deciding on the measures to be used, take care to ensure that their definitions are agreed. For example in a delivery performance project, the key measure was on-time delivery. It was not until part way through the project that it was discovered that half of the team thought that on-time meant as measured against the factory scheduled delivery date whilst the remainder thought that it was measured against the customer’s required delivery date; sometimes there were weeks between them. A typical measure of a process is that of Cycle Time. This is the total amount of time to complete the process from boundary to boundary. Value Analysis There may be many steps within a process. Each step will take time, material and add cost to the process. Thus, it is important that each step adds value to the process. A step that contributes to customer satisfaction adds value. If this step were eliminated then the customer would notice. The definition of whether a step adds value or not needs to meet three criteria (Eckes): wdp consulting six sigma
40. 40. 1. The customer must be willing to pay for that step in the process 2. The step must physically change or transform the product or service 3. The step must be done right the first time It is often easy to identify non-value added work as the process step begins with the prefix “re” e.g.: rework, review, reclaim, rewrite, reject, retest, recall. Eckes identifies six major categories of non-value adding work: Internal failures – steps related to correcting errors/ rejects in the process External failures – steps relating to failures at the customers Control / Inspection – does this add value? Why can’t the process get it right first time? Delays – often seen as waiting for the next stage of the process Preparation/set up – the time this activity takes up has led to the demand for long runs Movement – excess movement is often created due to poor factory layout Compare this list to the Seven Wastes (see Lean Operations) identified by Taiichi Ohno: 1. Overproducing 2. Waiting 3. Transporting 4. Inappropriate processing 5. Unnecessary inventory 6. Unnecessary motion 7. Defects Having identified non-value adding steps it is useful to calculate the impact they are having on the total cycle time of the process. It will also enable priority to be given to the step that has the largest detriment on the process. Given that most processes have been in operation for many years then it is quite possible for steps and procedures to have been added for someone or purpose many years ago but are no longer of value. At each step consider key customers’ needs. If the step does not satisfy a customers’ needs then look to eliminate it. For each step ask: Does this step add value in our customers’ eyes? What would happen to the customer if this step were eliminated? Are others in the organisation affected by this step? If a value-adding step adds considerably to the cycle time, try to brainstorm ways of reducing the time taken without losing the value. wdp consulting six sigma
41. 41. Inspection / Control Points A point of contention is the identification of inspection or control points. Inspection does not add value and appears when a step within a process cannot produce its output right-first-time. In the interests of process improvement it would be better to not have such inspection. However, within critical processes some inspection may be necessary in order to monitor the process and to check for any unforeseen changes to the process. Needless to say, such points should be kept to a minimum. Where an inspection point is deemed necessary then it is important that the standards to which the inspection is made are clear. Inspection/ Control points should be positioned close to where an error may be first detected. Suppliers The quality of the inputs will influence the quality of the process. Often there is little communication between Customers and Suppliers, whether internal or external, such that there is often little knowledge of exactly what the customer requires and from the customer’s point of view exactly what the Supplier can provide. Too often Suppliers take on contracts knowing that they will find it difficult to meet them. An example in the electronics industry found a Supplier receiving returns from a customer for oversized mounting holes in a circuit board. After several rejected batches and varied excuses from the Supplier, they eventually admitted that they could not maintain the hole-tolerance of +/-1mm. Further investigation at the customer’s revealed that the tolerance was a default tolerance and the process could easily cope with a tolerance of +/-2mm, a figure the Supplier could achieve. A lot of unnecessary hassle and frustration could easily have been avoided. wdp consulting six sigma
42. 42. Measurement “What gets measured gets done.” Measurement is an important part of process / product improvement. If you don’t measure, how do you know whether things have improved? Within an organisation there are many things that could be measured but for historical reasons the things that are currently measured may have little to do with the areas that need to be improved. By measuring we can: Ensure customer requirements have been met Monitor progress against objectives Create standards for comparisons – Benchmarking Provide visibility for everyone to understand their performance level Estimate the costs of poor quality Identify areas for improvement However, beware what gets measured affects behaviour. “Tell me how you will measure me and I will tell you how I will behave. If you measure me in an illogical way, do not complain about illogical behaviour.” (E. Goldratt: The Haystack Syndrome) For example: in a chemical company each shift was measured by its yield. A poor yield resulted in aggressive messages on the notice board and strong words from the departmental manager. In most cases the operators were powerless to affect the yield yet they still were blamed. So to avoid the hassle, the Supervisors under- reported the quantities of raw material used. This led to an improvement in the yields and a quiet Management. The only problem that Management had to confront was to account for the thousands of pounds of missing raw material at the annual stock check. The choice of measurement is important. There needs to be a clear understanding of why something is being measured and whether it is the most appropriate measure. Three criteria for measurement (Eckes) are: 1. Measure only what is important to the customer. 2. Only measure those outputs of a process that you can improve. 3. Measures of effectiveness in which you have no history of customer dissatisfaction should be avoided. wdp consulting six sigma
43. 43. In Six Sigma a term that is commonly used is that of Critical to Quality or CTQ. (This can also be referred to at Critical to Customer or CTC).This refers to any features of a product or aspects of a process that a customer would view as being important in the performance of the product or process. Thus, if they are critical to the customer then they should be measured. A word of warning; there are many things that can be measured. Concentrate on the critical few. Measurement Systems Measurement Systems are the means by which data is obtained. For measuring dimensions this will include gauges, scales etc. For process related measures it may be the point at which the data is collected or the data itself. It is often assumed, incorrectly, that the tools used to create the data are suitable for the job. It is important that several aspects of the measurement system are known. Accuracy – the measured value reflects the true value Repeatability – the same person repeating the measurement gets the same result Reproducibility – a different person repeating the measure gets the same result Stability – the same measurement repeated over time does not vary Adequate Resolution – the measure has enough different values to pick up differences. For measuring equipment then a Gauge R & R study should be carried out before data is collected. Just because a piece of equipment has been calibrated does not guarantee its suitability. This process is more difficult for qualitative data i.e. yes/no, opinions etc and if possible quantitative data should be collected. Qualitative data can be made to look more like quantitative data. For example in the measuring of “pain” in drug trials a 20cm line is used marked “no pain” at one end and “severe pain” at the other. The individual is then asked to mark on the line the appropriate level of pain. This point is then measured in either centimetres or millimetres. This is better than a qualitative five-point scale: “no pain”, “a little pain”, “moderate pain”, “a lot of pain”, “severe pain” wdp consulting six sigma
44. 44. Measurement Variability When collecting data it is recognised that there will be variation from the process, but there will also be variation introduced by the measurement system. It is important to know how much variation is being introduced by the measurement system hence the need for an assessment of the system. Questions to be answered. How big is the measurement system variability? What are the sources of the measurement variability? Is the measurement system stable over time? Is the measurement system capable of making the required measurements of the process? What needs to be done to improve the measurement process? The purpose of measurement systems analysis is to quantify the variation due to the measurement system itself. Too much variation from the measurement system and - changes in the process may be hidden - the measurement system may give rise to a false belief that a change in the process has taken place. Measurement System requirements - the measurement system must be in a state of statistical control (stability) - the variability of the measurement system must be small compared with the manufacturing process variability and any specification limits - the increments of measure must be small relative to either the process variability or the specification limits - the measurement system should give the true or reference value, within acceptable limits (accuracy and precision) Accuracy and Precision Confusion often exists between these two terms. Accuracy is were the data on average reflects the true value. Precision is where the data shows very little variation. Ideally a measurement system should be both accurate and precise. Sometimes accuracy is called bias – the difference between the observed average and a reference value. This should be close to zero. wdp consulting six sigma
45. 45. Precision / Accuracy Accurate not precise Precise not accurate Neither precise nor accurate Precise and accurate Repeatability – this is the variation observed when a gauge is used by one person repeatedly to measure the same part. Theoretically the observed value should always be the same, however, in practice this is not the case. Repeatability is usually much smaller than the precision of the system. Reproducibility – This is the variation present when the same part is measured by different people. Variation of Measurement System (precision) = Repeatability plus Reproducibility σ2 ms = σ2 rpt + σ2 rpd Stability – this is the variation present when the same part is measured by the same person over time. This can be assessed using a Control Chart and must be stable. Measurement Discrimination – this sis the capability of the measurement tool to detect small changes in a measured characteristic. The higher the discrimination, the smaller the changes that can be detected. As a rule of thumb the tool should be able to detect a change of a tenth of the total process spread. Gauge R&R This stands for Gauge Repeatability and Reproducibility. This is a set of trials conducted to assess the Repeatability and Reproducibility of the measurement system. In simple terms – several operators measure several items a number of times. For example: 3 operators measure ten parts three times. wdp consulting six sigma
46. 46. The calculations associated with this study will be covered in the training. Sample Size One of the difficulties, in collecting data, is knowing how much to collect. There are statistical methods of calculating the minimum sample size but the result of the calculation is often a size that is beyond the practicalities of the study. Formula: Sample size > (2 x process sd / difference to be detected)^2 (95% confidence level) Example: Process has an sd of 0.25. What sample size is required to detect a difference of 0.1 mm? Sample size = ((2 x 0.25) / (0.1))^2 = 25 units Basic principles to follow are: Collect enough data to represent the total variation of the usual process. Try to collect quantitative data Ensure that the data represents “common cause” variation and not “special cause” variation Sigma Calculation Six Sigma has introduced the measure known as Process Sigma or the Sigma metric. This is simply a metric that reflects the ability of the process to meet the specifications of the process. It is important to ensure that the specifications used represent the customer requirements and do not as often happens represent the organisations view. Sigma is derived from DPMO (Defects per Million Opportunities). DPU = number of defects / number of units DPMO = (DPU / Opportunities for error)*1,000,000 wdp consulting six sigma
47. 47. DPMO is then converted to Sigma from tables (see Appendix) DPMO Process Sigma 308,537 2 66,807 3 6,210 4 233 5 3.4 6 Where Does Sigma come from? The Sigma value is based on mathematical calculations of the area under the Normal distribution curve. Normal curve Under the standardised Normal curve it is known that 68.27% of the data lie within one standard deviation of the mean, 95.45% of the data lie within two standard deviations of the mean. Thus if we consider what lies outside of two standard deviations from the mean we can calculate 100-95.45 = 4.55. If we convert to a proportion (divide by 100) and multiply this by 1,000,000 we have the number of defects we would expect in every million items. (45,000 defects). So at the level of two sigma we would expect 45,000 defects. Notice that this is not the same value as in the tables. This is because the table values are adjusted to allow for a long-term shift of the process (estimated at 1.5 sigma). Thus two sigma is really 0.5 sigma. The Sigma metric has both benefits and problems Benefits Allows different processes to be compared. Accounts for the fact that one process may have many steps whilst another only has a few. Moves the mindset away from percentages (many managers would stop improvement if they had a process that was producing 95% good product) Provides a baseline to compare improvement Disadvantages wdp consulting six sigma
48. 48. Is based on the theoretical Normal distribution Is used as an exact measure when at the edges of any distribution the ability to predict accurately declines The 1.5 sigma allowance may be inappropriate Sigma can be inflated by increasing the number of opportunities for error Some organisations have avoided the problem of defining an “opportunity for error” by simply using defects per unit. Thus if a process has a failure rate of 5% then DPU = 0.05, DPMO = 50,000. From tables Sigma = 3.1. wdp consulting six sigma
49. 49. Statistical Thinking Understanding Variation Variation appears in all processes. Look around you; no one is exactly the same – even identical twins have differences. Write your signature several times – they are different. Measure the output from a machine – they will never be exactly the same. In essence statistics is the study of variation. Without understanding variation, process improvement cannot be achieved. In order to describe the amount of variation then a number of measures are used: mean, mode, median, standard deviation and range. Together these will describe the variation. These values will be discussed in basic statistics. Understanding the variation within a process will help determine what needs to be done to reduce it. Why reduce Variation? Life becomes so much easier if every time you do something the outcome is exactly the same. You can predict what is going to happen and therefore be prepared. This is especially true for the output from a manufacturing process or service provision. If you knew that your journey to work would take exactly twenty minutes every time then you know what you have to do to arrive at work on time. However, most things do vary and so we have to allow for the variation. Variation presents problems in both manufacturing and services. For instance, a screw has to be put into a block. Variation can mean that the screw and block do not match. Or a bearing is produced slightly large creating increased friction causing a poor performance of the product. A service call takes longer than expected thus impacting on planned calls for the rest of the day. Understanding the variation will allow us to reduce the main sources and thus incur less problems and failures. This has been the basic premise of Quality improvement. wdp consulting six sigma
50. 50. Special Cause and Common Cause Variation Variation can be of two types: Common Cause - there all the time - part of the natural variation inherent in the process Special Cause - exceptional - unpredictable It is important in starting process improvement to be able to distinguish between Common Cause and Special Cause variation. Six Sigma looks at reducing Common cause variation and in doing so may change the process such that Special Causes are eliminated. However, if Special Causes are present in the process then they need to be identified and removed. To identify and remove Special Causes for which the root cause is unknown, a rigorous and logical problem solving methodology, such as RISE, is required. Special Causes must be removed to allow a clearer understanding of the Common Cause variation. They must also be removed because they may fail to appear during the data collection and give a false sense of security to the improved process only to appear later and produce unexpected rejects. In terms of responsibilities: Common causes – management must change the system. Use process improvement, Six Sigma methodologies Special cause – operators/administrators to identify cause and eliminate. Deming estimated that 94% of processes exhibit Common Cause variation and 6% exhibit Special Cause variation Sources of Variation Variation can be found in a number of sources, some of which may be easy to affect; others may be difficult. For a process the sources of variation may be understood by use of MEPEM or the M’s. wdp consulting six sigma
51. 51. MEPEM M’s Materials Materials Equipment Machines People Men Environment Mother Nature Methods Methods Measurement Maintenance For a product then the above categories can be used or the following: 1. Piece to piece variation 2. Changes over time (wear) 3. Customer usage 4. External environment 5. Interaction with neighbouring sub-system This is known as a Noise Tree. Consider a fountain pen. Why might a pen not function as intended? Piece to piece – variation due to size of nib, size of casing, size of ink cartridge/ holder, ink viscosity Wear – nib wear, amount of ink Customer Usage – user style, angle of writing, pressure applied, storage, hand size Environment – temperature System to system – type of paper In looking for improvement then there needs to be an understanding of what factors are influencing these sources in order to make changes to reduce the effect. Taguchi’s Loss Function Six Sigma tends to have the philosophy that the aim is to reduce variation such that it is well within the customer specification. This focuses on the specification limits. However, Taguchi points out that the philosophy should be to focus on the centre point (mean) and minimise variation around that point irrespective of the specification limits. wdp consulting six sigma