Six Sigma im Blickpunkt

The tools and techniques of Six Sigma are recognised to have a big impact on productivity given sufficient investment in senior people, time, cost and culture change. Brian Davis finds out the relevance of this long-standing business strategy on modern manufacturing.

SIX Sigma (6S) is a statistical process for determining that the most efficient process is used to satisfy customers, while removing variation and improving consistency. Developed by Motorola in the mid-1980s and taken to heart by big corporations like GE, enthusiasm for the 6S approach spread across the US and then worldwide. The methodology is not limited to manufacturing and is rapidly gaining ground in the financial services sector, retail, airlines and other sectors.

Nevertheless, the methodology has its detractors as it requires strong sponsorship from the board, and Six Sigma personnel need detailed training and commitment in order to drive process improvement projects at different levels in an organisation. Following the Japanese management style, trainers and trainees are given martial-arts style labels. Master black belts are full-time champions of process change and are often strong candidates for senior management promotion. Green belts lead smaller projects on a part-time basis.

Management consultants Kepner-Tregoe offer proprietary methodologies which support 6S implementation using problem solving and root cause analysis. Managing partner Margin Wing insists “Six Sigma is an improvement philosophy that requires significant culture change.” There are three key applications and 6S is only one of the tools.

First, 6S is useful for removing variation from the manufacturing process to get better standardisation. Second, companies need to address lean philosophy i.e. removing non-value added waste. Consequently, manufacturers often favour Lean Sigma to both remove waste and improve process standardisation. Third, there is need for continuous improvement of processes, people and systems in order to rise to the next competitive level.

Kepner-Tregoe recently helped an international food and beverage company to standardise their processes. ”Their processes were mature, but the company had difficulty getting to ‘special cause’ in terms of 6S,” explains Wing. A ‘common cause’ event halts the line as a result of natural variation, whereas a ‘special cause’ falls outside the normal control boundaries. At an operations level there was a lot of fire-fighting to keep lines running as they didn’t address the root cause of variation.

Consequently, four key elements of work were tackled. First, Kepner-Tregoe upped problem solving skills using proprietary Root Cause Analysis methodology. Second, they built these skills into recognised operating procedures, i.e. for handling escalation levels to shift leaders, area managers and above, so that problems were not shelved. Third, people were coached on the job, and fourth, the performance environment was modified by prioritising work, and giving feedback on tasks and individual consequences. “By embracing the hearts and minds of people across the organisation, 6S, lean and continuous improvement can be used effectively to reduce downtime, improve cycle times and improve the bottom line,” says Wing.

What’s the difference?

Quentin Brook, managing director of Opex Resources which publishes operational support tools, argues that “6S programmes shouldn’t be differentiated from other continuous improvement activities. People need 6S skills so they can analyse and approach projects in a logical way. I’m not in favour of having an elite group, such as master belts, as initiatives tend to fall flat after a time unless the skills are deployed in service and across multiple functions.”

Opex Resources has developed a Lean Sigma and Minitab software product in partnership with BT which has sold 50,000 copies. It follows the DMAIC problem solving process, that is: i) Define customer requirements, ii) Measure, iii) Analyse opportunities for process improvement, iv) Improve, to remove variation and improve capability, and v) Control and standardise improvements. The software offers tools for process mapping, value stream mapping and spaghetti diagrams, plus numerical tools for statistical analysis, graphical techniques and designed experiments. “Our pocket guide is aimed at people who have been through 6S training but need a refresher,” says Brook.

The Bourton Group considers 6S to be an invaluable part of the performance improvement toolkit, used in concert with other improvement methodologies like lean and kaizen blitz. “We have a very pragmatic approach to using DMAIC methodology,” says managing director Stuart Smith. “People often go overboard, not knowing what particular tools to use, what to measure or fix. We recommend using a Quad of Aims to institute the project and define the problem; then statistical tools, and Lean process tools, change management and project management tools.”

The ultimate goal of 6S is to achieve 3.4 defects per million opportunities to make a defect. But 6S is a journey to a near impossible ideal, and most processes operate between 3S and 4S. For comparison, 6S is the equivalent of 1 hour wasted in every 160 work years, whereas 3S would be one hour wasted in every two working days. “Ultimately 6S is a journey of process improvement, with focus on variation and defects in processes, while lean focuses on waste and time compression,” says Smith.

Bourton Group worked with Rolls-Royce for five years, training designers, analysts and management to refine, improve and apply Design for Six Sigma (DfSS), to achieve high levels of predictive design quality. Product lifecycle design savings to date exceed £20 million.

Paper manufacturers Aylesford Newsprint worked closely with Bourton to utilise Lean Sigma to resolve local problems and to provide a foundation for continuous improvement. Since Aylesford began the Lean Excellence programme in November 2009, the company has achieved benefits exceeding £250,000 a year. Fifteen green belts and three black belts have been trained, resulting in large savings and improvements in work practices, more uptime, increased throughout yield and better output quality. A variety of tools are being used including 5S for maintenance processes, Root Cause Analysis to resolve a quality defect, and lean waste removal in the roll storage area.

“Six Sigma deployment has to be properly managed,” Smith admits. “Like a diet, you can get some quick effects but then gain weight again unless you stick to the regime. Property managed deployment means having enough capable people trained to green belt and black belt level, with sufficient time to work on a project and selecting the right project in the first place.”

200 black belts

Cummins Engines is an exemplar. The company began the 6S journey about 11 years ago at its Darlington and Daventry plants, and now has over 100 master black belts worldwide. “We’re trying to move emphasis towards customer focus, using lessons learnt in every area of the business, from shopfloor production to HR, finance and supply chain projects,” says Master Black Belt Gary McAlister. Cummins Engines has carried out some environmental projects that have reduced plastic waste, improved throughout, reduced maintenance spares inventory, and improved quality both internally and externally Quality is now between 4S-4.5S.

Logistics has seen a rainbow of projects using standard 6S statistical tools and KG analysis to analyse qualitative factors. “Process mapping is the first tool we use in every 6S project to identify inputs and outputs,” says McAlister. “We focus on cost savings and cycle time as key measures, and aim to drive up 6S certification across the company as a key requirement for promotion.” Forty-five 6S projects have been completed at the Darlington site this year and a further 25 projects are targeted by year end. “We’ve even improved import tax drawback using 6S to identify where we should have been claiming tax but missed it, improved utilisation of shipping containers from China, and improved the process for identifying defects in the suppliers’ warranty processes.”

Glaxo SmithKline’s Global Manufacturing and Supply business applies both 6S and lean manufacturing tools under the banner of Operational Excellence. The GMS business unit has nearly 200 black belts and 74 master black belts, skilled in both lean and 6S. “In the last few years, we have taken an increasingly practical approach to training operators in standard work methodologies,” says Derek Willison Perry, VP Operational Excellence GMS. “This allows us to engage the people who can refine and define processes so that we improve our process control and productivity from the line upwards.”

Richard Holland, managing director of TBM Consulting Group, warns that the Six Sigma toolkit “is sometimes too big a sledgehammer for the problems a company faces. Businesses must be selective – only a small proportion of people in a company are likely to embrace the methodology, and most require quick ways of solving problems on a daily basis. We encourage companies to use policy deployment to agree long-term goals (3-5 years), then identify what’s vital for the coming year, and the improvements necessary to meet those goals, as opposed to continuous improvement activity, which can be seen as optional.”

Doncasters Metal Casting, for example, used the 6S approach to reduce post scrap shrinkage in turbine blades during the casting process. The company converted fixed defect data into continuous data, for improved inspection and recording of yield and rework. Each year it is targeting that 1% of each unit headcount becomes a blackbelt, one for every 10 greenbelts.

Most manufacturers consider that having 6S skills gives competitive advantage. But most will concur, it is only one tool in a continuous improvement arsenal. Choosing the right 6S project should be strategic, not simply for firefighting.

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