Product Design Speak 101: Linear versus Iterative Design


Design, by its very nature, is an iterative process. The product design process begins with creating preconceptions. Those preconceptions are used to create a prototype. The prototype is then tested and the test results are evaluated. The evaluations are used to form new preconceptions and the process begins again. These iterative cycles can focus on the entire design, or they can focus on a small area (or technology) of the product. This process relies on prototyping and testing. Prototypes come in many forms. The word ?prototype? is commonly refers to a working model of a product, or product concept. A written, or verbal, description of the product could also be a prototype. A sketch could also serve as prototype. The exact nature of the prototype isnt as important as the effect of the prototype, which is to validate the success, or failure, of the product. As the design progress, the cycles of iteration become more focused, as the developers refine the product.

Different industries have differing levels of toleration number of iterations in a design sequence. Machine design is a good example of an industry with a low tolerance for iteration in the design process. Engineers that design machinery attempt to practice design in a very linear fashion. The goal in the machine design industry is to reach a finished, and proven, design in the least amount of time with the least number of changes or redesign cycles. This approach attempts to follow the straightest possible path to a completed design. This ?straight arrow? approach leads us to classify this industrys design methodology as a linear one. Even with this approach, iterations are necessary. Design iterations inevitably occur during the process of design a new piece of equipment. The can be caused by a machine, or system within a machine, that doesnt perform as expected. When this happens, that part, or sub-system, is redesigned and redeployed. Because of these issues the machine design industry does not have a completely linear process.

The linear nature of machine design is driven by two factors. The first factor is the prevalence of a function requirement and the minimization of aesthetic requirements. In my opinion, the biggest cause of the use of a linear design process in the machine design industry is the percentage of engineering and design costs as compared to the total cost of producing and marketing the machinery. Many machines are custom, or semi-custom, to the specific application (often manufacturing). This results in a small number of units to amortize the engineering costs against. This is a situation where the cost of design and engineering is a significant percentage of the total cost to produce the each machine. As a result, savings in the cost of design have a significant impact on the profitability of that design. This is the exact opposite of consumer products that have a low cost of design, relative to the total cost of producing the product.

Consumer products are examples of products with a very iterative design process. These products are typically produced in high volumes. This allows the cost of design and engineering to be amortized over a large volume of product sales. In higher volume products, there is more incentive to spend more time on the industrial design and front-end design (fuzzy front end) stages of the design process.

Any product, or service, will be judged by the market place based on the experience that the product provides. Machinery is evaluated on institutional-experience criteria including performance, ease-of-use, speed of installation, return on investment (ROI) and uptime. Consumer products are evaluated on end-user experience criteria that include ease-of-use, aesthetics, coolness, usefulness, perception that the product creates and the experience that the user has when interacting with the product. The latter criteria can be very subjective and difficult to capture in any sort of written document.

Products with great user experiences often succeed in the marketplace, where products with poor user experiences fail to generate sales. This does not mean that user experience is the only indicator of potential success. A product may have a compelling value to the customer that overcomes a poor user experience. Typically these products are the first in their class and provide some functionality that is new to the industry. This is a case where the value to the customer is high and the customer will accept a poor user experience in exchange for that functionality. As a segment of an industry matures, the user experience becomes a more important indicator of how well the product will sell in the marketplace.

The current game console war is a good example of this contrast between functionality and usability. The PlayStation 3? is a game console that has an average user experience, but provides state-of-the-art computer graphics. The Wii? is a game console that provides average computer graphics, but has a wonderful user experience. The Wii? has outsold the PlayStation 3? by about twenty percent.

Product iteration allows the design team to explore a variety of concepts. The evaluation of these concepts helps to decide which concepts to integrate into the product and which concepts to drop from the product. Many times the issue isnt whether a concept is good, or bad, but rather ?is it appropriate This is especially true when the design team is evaluating, and improving, the user experience of the proposed product.

Product developers, designers and engineers use the available resources (which are always finite) to work towards achieving the best product possible. The nature of the product and the expectations of the industry and customer ultimately drive the exact nature of the design process. Design is iterative. Product designers rely on experience and a refined process of iterating through the design cycles to create the next product. Often a designer achieves success not by any one single action, but by the consistent application of an educated, and refined, design process.

Montie Roland is President of the Carolinas Chapter of the Product Development Management Association. Roland is also President of Montie Design, a product development and prototyping firm in Morrisville, NC and the RTP Product Development Guild. You can reach Montie by email at:

Montie Roland

Montie Roland is President of Montie Gear, a manufacturer of outdoor sporting equipment in Sanford, NC. Montie is also employed at Pentair in Sanford, NC as a Mechanical Engineer on the New Product Development team. Montie enjoys finding innovative solutions to customer requirements. He has 15 years of experience engineering products in diverse market spaces including industrial, commercial and military. Montie earned a BS in Mechanical Engineering from North Carolina State University. He is also the President Emeritus of the Carolinas chapter of the Product Design Management Association ( and a founder of the RTP Product Development Guild (

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