Do it right the first time

Design for Six Sigma develops better products and services

By Elizabeth A. Cudney and Tina Agustiady

Do it right the first timeCustomers’ expectations must be met or exceeded in order for a business to be sustainable. To deliver products that consistently meet customers’ expectations, your enterprise must develop and use a product development process that transforms customer wants and needs into the design of products or services. Product design is a process that identifies the product purposes and functions and then allocates them to a structural or concrete form.

The typical organization spends considerable resources correcting problems during its product development process. To shorten product development time and save costs, product teams must evaluate how the product fills customer needs while simultaneously creating metrics for achieving those needs. The ability to evaluate how a potential design conforms to design specifications prior to building the hardware can shorten the development cycle and decrease costs. The iterative process of design-build-test-fix is simply too slow and expensive.

Design for Six Sigma is a data-driven quality strategy to develop robust products and services. Design for Six Sigma provides a methodology to collect and statistically analyze the voice of the customer (VOC), develop product concepts, experiment to optimize design quality, and model the product to reduce risk to make data-driven decisions in order to create robust products and design services and processes.

Continuous improvement

Design for Six Sigma is integral to Six Sigma quality initiatives because it employs systems engineering techniques to avoid manufacturing and service process problems. The methodology’s purpose is to design a product, process or service right the first time. The design for Six Sigma methodology uses the customer’s critical to quality (CTQ) characteristics throughout the design process to ensure user satisfaction.

Design for Six Sigma is not intended to be a standalone process; rather, it should be a regular part of all design activities. As such, design for Six Sigma should be integrated into the organization’s technical design reviews, also known as tollgates, during the design process to ensure that all problems are escalated appropriately.

Design for Six Sigma improves customer satisfaction and net income by providing a methodology to institute change, make decisions based on analysis, gather data and ask the appropriate questions. Not using the design for Six Sigma methodology can result in a low return on investment, not to mention the risk of creating design solutions that are not innovative. Design for Six Sigma provides insight to creative processes by examining critical design elements. The focus of design for Six Sigma is to emphasize the usability, reliability, serviceability and manufacturability of the design in order to develop a product or service that meets or exceeds customer expectations and business requirements.


Design for Six Sigma embeds the underlying principles of Six Sigma to design a process capable of achieving 3.4 defects per million opportunities. The focus is on preventing design problems rather than fixing them later after they can affect the customer.

Design for Six Sigma follows a five-step methodology – define, measure, analyze, design, verify (DMADV) – that focuses on the customer:

  • Define: Define the problem and the opportunity a new product, process or service represents.
  • Measure: Measure the process and gather the data associated with the problem as well as the VOC data associated with the opportunity to design a new product, process or service.
  • Analyze: Analyze the data to identify relationships between key variables, generate new product concepts and select a new product architecture from the various alternatives.
  • Design: Design new detailed product elements and integrate them to eliminate the problem and meet the customer requirements.
  • Validate: Validate the new product, process or service to ensure customer requirements are met.

Figure 1 outlines these phases and their respective tools.

Design for Six Sigma puts the focus upfront in the design/engineering process. The key focus is ensuring the team understands the customers’ requirements and their tolerance to performance variation. To do this, it is necessary to bring the appropriate experts together to engineer a robust solution and reduce the impact of variation. Design for Six Sigma is used when:

  • Products or processes do not currently exist.
  • New products or services are introduced.
  • Multiple fundamentally different versions of the process are in use.
  • Current improvement efforts are not enough.
  • Products or processes are broken and need help.
  • Products or processes have reached their limit.

Initial process capability limits may not conform to or meet customer needs. Therefore, the design for Six Sigma interactive design process is required to make sure the result meets customer needs, the process becomes capable and the product or service functions as desired. Design for Six Sigma enables teams to understand the process standard deviation, determine Six Sigma tolerances or confirm that customer expectations are met.


By understanding the voice of the customer from the onset and using it throughout the product development process, organizations can reduce costs significantly. When changes to a product design are made early in product development, the costs are relatively low. However, the cost to make changes in the product design increases significantly over time as the product moves from research through design, prototype and production – particularly if defective or unsatisfactory products reach customers. For example, once the design moves to the prototype stage, fixtures have been built and machines bought or reconfigured. Changes in design at this stage result in costs to modify fixtures, machine codes and equipment, along with many other expenses. The price tag is significantly more once the design is finalized and in full production. If customers receive a product that does not meet their needs, the organization must go back to the design phase to implement the necessary changes. Design for Six Sigma enables the voice of the customer to be heard throughout the product development process, thereby reducing potential costs. Figure 2 illustrates the cost impact of making changes to the product design during the product development process.

For design for Six Sigma to be successful, the culture of the organization must transform from a reactive to a proactive mentality, and upper management must provide its full support. Design for Six Sigma involves everyone within the organization, including operators, engineers, quality, suppliers, vendors, upper management and champions.

This can transform, in particular, organizations that use a silo approach based on function to a culture where everyone takes an active role in improving products and processes, beginning from the bottom up.

Project management

Design for Six Sigma has a heavy emphasis on project management. Effective management of resources is necessary to ensure the efficient design of the new products and services. Design for Six Sigma projects are often complex and require considerable resources. Therefore, project management tools are necessary throughout design for Six Sigma project implementation to help meet deadlines and make sure the process achieves its deliverables.

Project management should be used in design for Six Sigma to balance the constraints of time, cost and quality expectations, resulting in a successful product.

This balance is illustrated in Figure 3. When these three factors cannot be balanced, a tradeoff is required. The relationship between the three factors is represented as a rigid (iron) triangle for a project since all aspects of a successful project must be accomplished within the organization’s goals. If a shorter lead-time or cost reduction is expected during the project, then a compromise along one of the other axes must occur, which alters the shape of the triangle. Design for Six Sigma features critical thinking skills that include the following:

  • Identify key elements of the design necessary to achieve the functionality desired by the customer.
  • Decompose the problem (system) into pieces by considering the system architecture.
  • Flow down the customer targets from the system level to subsystems and components.
  • Identify a set of design alternatives.
  • Select the design alternative that best meets customer expectations.
  • Manage the risks of the design at all levels of the system.
  • Deliver a robust design that is insensitive to noise.
  • Manage the variability in a design.

Can lean Six Sigma trump an MBA?

Can lean Six Sigma trump an MBA?

As college costs skyrocket, many are looking for alternate educational paths to success. For his part, Tony Misura touts lean Six Sigma over the coveted MBA.

Writing for LBM Journal, which covers the lumber and building material distribution sector, Misura said his industry’s most common challenge is creating a culture of continuous improvement. He cites a number of successful examples, including L.T. Gibson, the CEO of U.S. LBM. That company embraced lean Six Sigma and had 3,000 employees earn certifications. Misura maintains that lean Six Sigma, unlike an MBA, teaches tools that are practicable for everyone: truck drivers, dispatchers, sales professionals and leaders.

The training is practical and hands-on, unlike the theoretical approach taken in MBA classes. You can get a lean Six Sigma black belt within a year by spending only a few weeks in the classroom, and you implement the practices directly in the workplace, Misura wrote.

So perhaps those looking for a professional leg up can find a cheaper option versus the $60,000 to $70,000 that a full-fledged MBA can cost.

Design for Six Sigma complements the product development process. The voice of the customer interpretation tools are key to design for Six Sigma, along with engineering and statistical methods used during product development. The main objective of design for Six Sigma is to “design it right the first time” by identifying product features and functions that the customer can recognize as being beneficial, ensuring the object of design can consistently deliver exceptional performance.

Customers change constantly, and we need to be able to change to meet their needs through innovation and benchmarking. However, we want them to be satisfied right away – and design for Six Sigma practices can make sure your customer is happy the first time around. This will prevent the customer from going to your competitors, and it will gain commitment from them, along with future access to their buying power.

Let’s examine a couple of examples of how design for Six Sigma has been applied to design products.

Example 1: Portable energy solutions

Customers are always on the move with their electronic devices; however, finding charging stations is not always easy. Based on this need, a design for Six Sigma team focused on developing a portable charging solution that was versatile. By conducting an extensive survey to gather the voice of the customer, the design for Six Sigma team was able to gain a comprehensive perspective of customer needs, such as needing a minimum 5,000 mAh output charger that has a status indicator, is easy to use, small, universally compatible and able to withstand a 3-foot drop.

The team then used quality function deployment to integrate the customer expectations into the functional requirements. This step also involved conducting a thorough benchmarking analysis to identify areas for improvement and prioritize efforts for the product design.

Design for X was then used to generate several concept designs, which were evaluated against the voice of the customer using Pugh’s concept selection matrix to identify the superior concept. Next, optimization methods were employed, including modeling the robustness and tunability of the mean critical functional responses and modeling vibrational sensitivities across the integrated product design in addition to creating a system additive model, system variance model and robustness additive model. The design for Six Sigma team applied these methods to the superior concept in order to minimize noise, improve reliability, reduce failures and improve functionality.

Applying design for Six Sigma helped the product meet the needs of the customer by deploying the voice of the customer through the design of the product, which resulted in a universally compatible charger with solar-charging capability.

Example 2: Better beds for the hospital

Design for Six Sigma also was used in a case to redesign a standard hospital bed.

Hospital bed designs must comply with strict guidelines from the Food and Drug Administration to ensure safe operation to reduce potential life-threatening entrapment areas. In order to redesign a hospital bed effectively, all stakeholders, including patients and medical staff, must be considered to ensure a safe, comfortable and efficient final product. In addition, as medical costs continue to rise, expense is also a key factor.

The first step in the project was to identify all of the stakeholders. This was done through social network analysis. Once the stakeholders were identified, an extensive survey was distributed to gather the voice of the customer from each stakeholder group to determine the critical characteristics. Using the voice of the customer, the design for Six Sigma team brainstormed ideas to improve the standard hospital bed design, which were then organized using the Kano model. Exciting quality features included a built-in tablet for entertainment and ability to track medications. One-dimensional quality characteristics included adjustable height, suitably placed controls, ergonomic side rails and a bed that was easy to move around.

Finally, expected quality characteristics included comfort and affordability. Since cost is an issue, the design for Six Sigma team focused on the expected and one-dimensional characteristics, which were ranked and prioritized.

The design for Six Sigma team then employed quality function deployment to translate the customer expectations into functional requirements for all levels of the system architecture. This also involved a competitive analysis against three hospital beds that medical centers use widely.

Using this information, the design for Six Sigma team developed nine conceptual designs. Due to the complexity of the design, the team considered the system architecture to cascade the customer and product characteristics through all levels of the design.

The conceptual designs were compared to the voice of the customer using the Pugh concept selection matrix. Through the comparative analysis, the best aspects of each conceptual design were combined to develop a hybrid design to better address the customer needs.

The final design was optimized using the p-diagram to understand the input-output relationship of the performance parameters. Noise factors such as wear and tear, hydraulic malfunctions and electrical failures were considered in the p-diagram. This information was then used to identify potential failures using design failure mode and effects analysis (FMEA). Significant potential failures included stuck wheels and defective electronic controls.

By identifying these risks early, the design for Six Sigma team was able to modify the design to address these concerns and design a robust hospital bed. Using design for Six Sigma principles, the final design addressed requirements from all of the stakeholders.

Elizabeth A. Cudney is an associate professor in the engineering management and systems engineering department at Missouri University of Science and Technology. She earned her bachelor’s degree in industrial engineering from North Carolina State University, her master’s degree in mechanical engineering and MBA from the University of Hartford and her doctoral degree in engineering management from the University of Missouri-Rolla. She has been inducted into the International Academy for Quality. She is an IISE lean Six Sigma master black belt. She previously served on the board of directors for IISE’s Society for Engineering and Management Systems (SEMS) and Lean Division. She has co-authored six books, including Design for Six Sigma: A Practical Approach through Innovation, 10 book chapters and more than 65 journal papers. Cudney also served as a program chair for the 2017 IISE Annual Conference and Expo.

Tina Agustiady is a certified Six Sigma master black belt and continuous improvement leader. She is president and CEO of Agustiady Lean Six Sigma and project manager of deploying a lean enterprise system for Masonite. She previously was employed at Philips Healthcare, BASF, Dawn Foods and Nestlé Prepared Foods. Her B.S. in industrial and manufacturing systems engineering is from Ohio University. Agustiady was president of IISE’s Lean Division and has served as a board director and chair for IISE conferences. She has written several books, including Communication for Continuous Improvement Projects. She recently co-authored Design for Six Sigma: A Practical Approach through Innovation. She is an editorial board member for the International Journal of Six Sigma and Competitive Advantage.