DFSS for Green Design

The emergence of green technology and increased environmental awareness has prompted a paradigm shift in the way companies think about the design of their products. Because robust designs mean creating products to meet customer and societal needs, it is important that all enterprises rethink these needs in a broader sense. Efforts to alter conventional design and manufacturing processes to construct more eco-friendly products are already viable and will continue to drive results, not only for the environment but also for an enterprise’s bottom line.

In a majority of cases, the implementation of a "green design" for cleaner, greener production has led to an overall reduction in total costs, improvement in efficiency, and a decrease in costly waste.

The ISO 14001 standard assists in the universal challenge to reduce CO2 emissions and facilitate heightened efficiency in manufacturing for the 21st century, but it will not be enough to meet consumer needs. Organizations must include and pursue methods that incorporate the needs of their customers, and society in general, by designing and creating new, environmentally safe products. An effective environmental system will aid in the protection of the environment; however, if you do not design for green, your consumer may not purchase your products.

Green technology is a change against the status quo and that forward-thinking approach is a definitive sign that a company is not only acting intelligently, but is also proving that it is one step ahead of the field and its competition. The marketing aspect of embracing these standards alone can improve business. We saw this with ISO 14001, for instance, where companies used their EMS standards as the tipping point for potential business. Plus, these companies have the ability to gain exposure with new clientele who hold the same green ethos.

Beyond the marketability factor of implementing an EMS, there are legal factors. By committing to standards such as ISO 14001, an organization enhances its reputation with compliance to both regulators and the government. In turn, by having a cleaner, less polluted environment, an organization can shield itself from potential environmental and insurance liability risks that can be associated with wasteful environs. Implementing an EMS, in the most direct sense, can drastically improve an organization’s reputation.

Although adhering to an EMS standard, or any standard, is useful, it isn't enough. Products must be designed from the ground up to be green.

Green Design for Products

The consideration of environmental issues within a framework of product design is a process that is called green design. The goal is to produce more benign products for the environment, yet often, this forward-thinking approach also breeds more efficient processes. Essential in discussing green design is defining what the term "green" actually entails and understanding why there is an overall social movement for green. The "goal of green" on a societal level is to create a platform for sustainable development and the safeguards of both the maintenance of natural resources and the ecological health of our environment. (Chris Hendrickson, Noellette Conway-Schempf, Lester Lave, and Francis McMichael; Green Design Initiative; Carnegie Mellon University; http://gdi.ce.cmu.edu/gd/education/gdedintro.pdf [1])

When we discuss green as a single idea, the defining characteristic is an act that reduces or eliminates a form of pollution. There are hybrid vehicles that definitively put less stress on the environment than a modern SUV. On the other hand, a bicycle produces exponentially less waste than either a hybrid or an SUV, and so from a environment standpoint, it is "better." (Hendrickson, Conway-Schempf, Lave, and McMichael) In other words,  a product that uses renewable materials, renewable energy, and that, at the end of its life span, completely decays, returning its constituent parts to the Earth, would still not be as green as a similar product that simply utilizes a lesser volume of material.

There is no distinct definition of a green product; instead there exists only a comparison of alternative products with comparable functions. Green actions are judged on a scale in accordance to their functionality of a specific task. Green designs breed three universal goals that are to be upheld as guidelines when creating a green product: the elimination of non-renewable materials in a product, the management of renewable resources to guarantee sustainability, and the decrease of harmful emissions that add to increases in global warming. (Hendrickson, Conway-Schempf, Lave, and McMichael)

This, of course, is easier said than done. A car can produce little to no emissions and can be comprised exclusively of recyclable material. However, if that car costs twice the amount of its competitor, more often than not that product will be sitting on the showroom floor while the car that is less green is on the road. With this said, green design is becoming more of an afterthought.

Is it easy to produce a computer that is fast, powerful, cheap, energy efficient, and composed of recyclable material? Of course not. It is a challenge. The brutal truth, though, is that eventually someone will. Products will continue to be novel and innovative, and in the 21st  century they will also be green. Those who do not make changes now will suffer inevitable repercussions.

Using Design for Six Sigma for Green Design

Green innovation is essential in product design, but to optimize the efficiency of this, critical methods such as Design for Six Sigma (DFSS) need to be incorporated into product designs. Product design is defined here as the creation of a detailed description for a physical good or service combined with the actual process of producing that good or service. The application and definition of product design can be improved further by incorporating tools that aid in better understanding the voice of the customer and society.

DFSS should be at the forefront of green technology designs, and in fact, has been used to design one of the most significant advances in green technology — the hybrid electric vehicle. DFSS increased the efficiency and life span of multi-celled batteries that are used in these hybrid electric vehicles, specifically the battery thermal control feature which dictates temperature distribution between cells and overall temperature control for the unit. (Andreas Vlahinos, Ken Kelly, John Rugh, and Ahmad Pesaran; Improving Battery Thermal Management Using Design for Six Sigma ; http://www.nrel.gov/vehiclesandfuels/energystorage/pdfs/evs_20paper.pdf [2])

Battery temperature is the central variable that affects the life of a battery and its performance; DFSS makes improvements in the design process that quantify improvement and eliminate defects in these processes. The specific process of DFSS is a product-oriented design methodology labeled the Define-Measure-Analyze-Design-Verify (DMADV) sequence. Below are the intricacies of this process and corresponding examples of each step in relevance to its deployment.

Define

The Define phase sets the tone for the entire design project in that it establishes its goals, charter, and infrastructure. During this phase, activities are shared between both the management team and the chartered project-design team. The primary objective of this phase is to create the initial business case that validates the selection rationale and establishes the business justification either through reduced product cost, increased sales, or entire new market opportunities.

In the case of battery thermal management, the goal is to maintain battery temperature below pre-determined figures and also to diminish the chances of temperature distribution within the different cells. (Vlahinos, Kelly, Rugh, and Pesaran)

Measure

The Measure phase is concerned with identifying the key customers, determining their critical needs, and what measurable critical-to-quality (CTQ) requirements are necessary for a successfully designed product. The design team transforms the critical customer needs into measurable terms from a design perspective. Translated, these needs become the CTQ requirements that must be satisfied by the design solution. Competitive benchmarking and creative internal development are two additional sources that generate CTQs.

For example, the multi-celled battery uses air between the modules of the battery for heat removal/exchange. To measure this, a parametric finite element model that predicts maximum temperature and maximum differential temperature within the pack is used. The gap between the battery cells, the cooling fan flow rate, and the internal electrical resistance are the three variables being measured for the input design in this process. (Vlahinos, Kelly, Rugh, and Pesaran)

Analyze

The main purpose in the Analyze phase is to select a high-level design from several  alternatives and develop the detailed requirements against which a detailed design will be optimized in the subsequent phase. A functional analysis of the CTQs established in the measure phase result in a high-level functional design. The design team develops several high-level design alternatives that represent different functional solutions to the stated functional design requirement. These alternatives are analyzed against a set of evaluation criteria and one of them, or a combination of alternatives, is selected to carry forward as the preferred “high-level design.” The development of alternatives and the selection of the preferred alternative are both iterative processes — as progressively more design information is developed, the iterative nature inherent in design requires that several passes be made to ensure that the most capable high-level design is carried forward.

The probablistic design loop was used for analysis in the DFSS application for Toyota Prius multi-celled batteries. In this model, design variables stated above in the “measure” section would be considered inputs, while means and standard deviations (i.e. maximum temperature, maximum differential temperature, and pressure drops) would be considered outputs. (Vlahinos, Kelly, Rugh, and Pesaran)

Design Phase

The Design phase builds upon the detailed design requirements to deliver an optimum detailed functional design that meets manufacturing and service requirements. Using the vital few design parameters, designed experiments (DOEs) are conducted to optimize the detail design around key design parameters. Results entail an optimum detailed parametric design represented by a mathematical prediction equation.

The quality level in this example is defined as obtaining maximum value, defined as less impact on environment, and still providing the power needed to start the vehicle. (Vlahinos, Kelly, Rugh, and Pesaran)

Verify Phase

The purpose of the Verify phase is to ensure that the new design can be manufactured and supported within the required quality, reliability, and cost parameters of the project. Upon completion of the several iterations that occur during the pilot runs, the design is solidified and a ramp-up to full scale production is accomplished via the manufacturing verification test (MVT) to highlight any potential production issues and problems.

Conclusion

Quality and environmental or green design are demanded in product design processes and will be ever present now and throughout the 21st century. Combining the applications of Design for Six Sigma and the tenets of green design will enable companies to be environmentally responsible in the development of new products that meet customers and societal need.

References:

1. Green Initiative; Carnegie Mellon http://gdi.ce.cmu.edu/gd/education/gdedintro.pdf [1]

2. ISO www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_ics_browse.htm?ICS1=13&ICS2=20&ICS3=1 [3]

3. Eco Friendly Manufacturing & Profitability, www.solid-state.com/display_article/316507/5/none/none/Dept/Eco-friendlymanufacturing-the-green-path-to-profitability [4]

4. Dow Corning Example, www.dowcorning.com/content/news/midland_environmental_investment.asp [5]

5. EPA: Lean Manufacturing & the Environment, www.epa.gov/lean/leanreport.pdf [6]

6. Lean Manufacturing Factsheet, www.deq.state.va.us/export/sites/default/p2/_documents/leanfactsheet.pdf [7]

7. Improving Battery Thermal Management using Design for Six Sigma Process, www.nrel.gov/vehiclesandfuels/energystorage/pdfs/evs_20paper.pdf [2]