Design for Six Sigma
Posted by isoeasy on May 26, 2006
Design for Six Sigma (DFSS) is a separate and emerging discipline related to Six Sigma quality processes. The tools and order used in Six Sigma require a process to be in place and functioning. DFSS has a different objective, that of determining the needs of customers and the business, and driving those needs into the product solution created. DFSS is relevant to the complex system/product synthesis phase, especially in the context of unprecedented system development. Contrasted with this is the traditional DMAIC Six Sigma process, as it is usually practiced, which is focused on evolutionary and Continuous improvement manufacturing or service process development. DMAIC Six Sigma usually occurs after initial system or product design and development has largely completed. In this way, DMAIC Six Sigma as practiced is usually consumed with solving existing manufacturing or service process problems (e.g., fire fighting).
DFSS seeks to avoid manufacturing/service process problems by using systems engineering techniques to avoid process problems at the outset (e.g., fire prevention). These techniques include tools and processes to predict, model and simulate the product delivery system (the processes/tools, personnel and organization, training, facilities, and logistics to produce the product/service) as well as the analysis of the developing system life cycle itself to ensure customer satisfaction with the proposed system design solution. In this way, DFSS is closely related to Systems engineering, Operations research (solving the Knapsack problem), Systems architecting and Concurrent engineering. DFSS is largely a design activity requiring specialized tools including: Quality function deployment, Axiomatic design, TRIZ, Design for X, Design of experiments (DOE), Taguchi methods, Tolerance design, and the Response surface methodology. While these tools are sometimes used in the classic DMAIC Six Sigma process, they are uniquely used by DFSS to analyze new and unprecedented systems/products
Q Is DFSS a methodology?
Not really. DFSS is an approach and attitude towards delivering new products and services with a high performance as measured by customer critical to quality metrics. Just as the Six Sigma approach has the DMAIC methodology (Define, Measure, Analyse, Improve, Control) by which processes can be improved, DFSS also has a methodology by which new products and services can be designed and implemented.
DMAIC is now an industry standard methodology for Six Sigma, however DFSS does not yet have such a universal offering. DMADV (Design, Measure, Analyse, Design, Verify) is one approach, however there are several in use. In many engineering design departments, DFSS is regarded as design optimisation, and the IDOV (Identify, Design, Optimise, Verify) methodology prevails, however this is focused very much on final stage engineering optimisation, and may miss many of the issues involved in actually selecting good products and features that will meet customer needs!
To deliver a good methodology that is customer focused, encompasses the entire business-to-market process, and deals effectively with both products and services, Geoff Tennant uses the DCCDI methodology – Define, Customer, Concept, Design, Implement.
Q What are the differences between Six Sigma and DFSS?
Six Sigma is a process improvement philosophy and methodology, whereas DFSS is centred on designing new products and services. The main differences are that Six Sigma focuses on one or two CTQ (Critical To Quality) metrics, looks at processes, and aims to improve the CTQ performance by about +1 process-sigma. In contrast, DFSS focuses on every single CTQ that matters to every customer, looks at products and services as well as the processes by which they are delivered, and aims to bring forth a new product/service with a performance of about 4.5 sigma or better.
Other differences are that DFSS projects are often much larger and take longer, and are often based on a long term business need for new products, rather than a short term need to fix a customer problem.
In practicality the divide between a formal DFSS project and a 'simple' Six Sigma project can be indistinct – at times there is a need for a Six Sigma project to radically improve the capability (rather than, or as well as, performance) of a broken or non-existent process using design or re-design.
Q Is DFSS only for manufacturing design?
Certainly not! Design traditionally has been associated with products much more than for services, however this is changing as companies realise that every product has associated services, many of which may matter more to the customer than the product! Engineers may be interested in using some of the 'six sigma' tools such as DOE (Design Of Experiments) to 'micro-optimise' design parameters. This runs the risk of turning out a perfect design but failing to deliver to all the customer requirements or a real commercial and business need. A full approach to DFSS will consider every aspect from the business NPI (New Product Introduction) strategy right through to ongoing commercialization. Any good DFSS methodology and approach must work as a framework for any type of design and for both products and services.
Q Where can I use DFSS in my company?
DFSS can be used anywhere a new product or service is to be introduced or re-introduced. For many manufacturing organisations the design and development of new products is very much a part of everyday company life, and a soundly adopted DFSS methodology can make a considerable improvement to the process of 'design and implement'.
Design and re-design can occur within any standard DMAIC project, and since there are many degrees of design within many commercial environments, there will be many 'flavours' of DFSS. These range from very large projects involving major design of entirely new and complex product/services, through to small 'excursions' into DFSS from a DMAIC type project.
Large DFSS projects are best suited for the introduction of new products/services with major design and large impact, and where customer approval and high levels of performance and delivery are required. DFSS is about reducing the risk of failure – failure to promote and develop the correct products/services, failure to identify all the customers and customer requirements, failure to design and implement appropriately and without error or omission.
Q What are the main tools used in DFSS?
It is very important to have practical experience of Six Sigma, as DFSS builds on the concepts and tools from a typical DMAIC approach. Since DFSS works with products/services rather than processes, and since design and creativity are important, a few new tools are common to any DFSS methodology. Strong emphasis is placed on customer analysis, the transition of customer needs and requirements (of the product/service) down to process requirements, and on error and failure proofing. Since the product/service is often very new, modelling and simulation tools are important, particularly for measuring and evaluating in advance the anticipated performance of the new process.
The main tools include QFD – Quality Function Deployment, FMEA – Failure Mode Effect Analysis, DOE – Design Of Experiment, and simulation techniques. However, just as in Six Sigma, the ability of the approach to be successful in use does not depend entirely on the tools used. Six Sigma brings a methodology (DMAIC) as well as a wider, deeper and more integrated use of existing tools. DFSS methodologies are about a wider, deeper and more integrated approach to commercial design, which involves everyone in the process as well as the customer to deliver a better product/service and final implementation!
Q What is the correct order for using these tools?
If DFSS is to work successfully, it is important that it covers the full life-cycle of any new product or service. This begins when the organisation formally agrees the requirement for something new, and ends when the new product/service is in full commercial delivery.
New Product Introduction
The selection by the business of a concept product/service to fill a new need. Benchmarking, customer survey, Multi Generation Planning (MGP), R&D and Sales and Marking input. Business focus and team chartering with risk analysis.
The start of the DFSS project for real. Plenty more benchmarking, customer survey and analysis, and more work on a team charter to build a solid foundation for the project.
The stage where the customers are fully identified and their needs collected and analysed. Mostly work with Quality Function Deployment (QFD) but here the aim is to identify the most appropriate set of CTQ (Critical To Quality) metrics to use to measure and evaluate the design by. This comes from a set of customer needs, together with a list of potential measures, and a lot of work on the first 'house of quality'. Hopefully too the start of numerical limits and targets for each CTQ!
Concept (Analyse – conceptual design)
The team take the concept provided by the business for the new product/service and begin to flesh out the concept to a working 'paper design'. This will require 'non-technical' design and a second round of QFD to identify the best 'features' that have the potential to deliver to the CTQs. Here we begin to move from CTQ to CTP – Critical To Process metrics. The idea is that, if the process by which the product/service is manufactured/delivered is 100%, then the product/service will also deliver to the customer CTQs and hence deliver to all of the customer needs! The end of this stage is a set of design concepts together with a set of CTPs that will constrain the formal and technical design.
Design (technical design)
The team handover the 'design brief' and the designers then complete the work, using all the CTPs as guides and evaluators to ensure that the design is perfect! Technical design can be carried out by the project team for simpler and service-type design, or by more technical and perhaps traditional design methods for more complex situations. Here we can use DOE and other statistical optimisation techniques, as well as greater creativity to bring inspired solutions that are proven to deliver. Simulation of both product, service and process are important tools.
No product or service should go directly to market without first piloting and refining. Here the team can use Failure Mode Effect Analysis (FMEA) as well as pilot and small scale implementations to test and evaluate real-life performance. Note however that this should be a fine tuning exercise and not a total re-design at this stage! Full scale commercial rollout will often then follow.
Once fully implemented, the new product/service and supporting processes can be handed over to (new) process owners, complete with new CTQs and monitoring systems! Naturally we have omitted to mention good amounts of project management, risk analysis and sound communication, as well as team-work