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Author: Yeh-Liang Hsu(2000-08-01); Last updated: Yeh-Liang Hsu(2003-06-25); recommended: Yeh-Liang Hsu(2000-08-01).
Note: This article is the lecture note of “ME4410 Automated Machine Design” Yuan Ze University. It is used strictly for teaching purposes.

Measuring a design

“It’s a bad design.” You must have said this very often. But why is it a bad design? How do you know it’s a bad design? Can a design be measured?

1.     Price and quality

From the consumer’s point of view, a design (a product) could be measured by its price and quality. Actually, the price of a product may change consumers’ expectation to the product.

The price of a product depends heavily on the cost of producing the product. Manufacturers do whatever they can to reduce the cost of producing the product. However, the fact that is often overlooked is that, the decisions made during the design process have a great effect on the cost of a product but cost very little. According to the data from Ford Motor Company, the cost of a vehicle consists of 50% material, 15% labor, 30% overhead, and only 5% design. But design can change the cost of manufacturing a product by 50%!

On the other hand, good design can also add value to the product. People are willing to pay more for good quality designs, even though the actual “cost” is much lower than the price. Note that here we are talking about the “quality of a design”, not manufacturing quality that we often talk about.

So what is a good quality design, anyway?

Here is the result of a consumer survey on what determines quality: works as it should: 98%; lasts a long time: 95%; is easy to maintain: 93%; looks attractive: 58%; incorporates latest technology: 57%; has many features: 48%.

Personally, I think there is one intangible quality that is missing, “being cool”.

2.     Kano’s model of customer satisfaction

According to the Kano’s model of customer satisfaction, there are three different types of product quality that give customer satisfaction: basic quality, performance, and excitement quality, as shown in the figure below.

Figure 1. Kano’s model of customer satisfaction

Basic quality is the customers’ requirements that are not verbalized as they specify assumed functions of the device.

Performance quality refers to customer’s requirements that are verbalized in the form that the better the performance, the better the product.

The products that include excitement quality will be popular and delighted. However, these customers’ requirements are often unspoken because customers do not expect them to be met in the products. Therefore, an engineering designer has a responsibility to find the excitement qualities of the products that customers may not even realize.

Another interesting fact is, over time, excitement level requirements become performance level requirements and, ultimately, basic requirements.

Conclusions

The only way to learn about design is to do design.

Just do it.