Viewpoint: Confused by Terminology?

"Rapid prototyping" once served well as the term used to describe a class of technology and its application, but times have changed.

By Terry Wohlers

"Viewpoint" is a monthly column authored by Terry Wohlers for Time-Compression Technologies
This column was published in the March/April 2007 issue.

Many are unclear, even puzzled, over what to call the technology that fabricates parts additively from computer model data. The industry has had nearly 20 years to sort it out, yet it is struggling with it more now than ever before. I've put a lot of thought into the problem over the past two years and have some ideas and opinions.

The subject is important because most companies, technologies and industries grow or decline based on their ability to penetrate new markets. Attracting new customers requires communication that people can understand and appreciate. This is especially true when entering non-technical markets that may involve ordinary consumers. If written or spoken words do not properly communicate the intended message, or gain attention, growth can stagnate. Conversely, if words with purpose and meaning are put in front of the same people, a developing industry can be given the chance to prosper.

In the Beginning

In 1988, 3D Systems and CMET, a Japanese company, sold a total of 34 stereolithography systems. These machines were among the first in a new class of technology that produced physical objects by joining thin layers of material, one on top of the next. The shipment and use of these machines marked the beginning of a new industry.

In the late 1980s and early 1990s, these and subsequent competitive systems were used almost exclusively for the building of models and prototype parts for new product development. Compared to traditional means of making prototypes, these machines made them rapidly. Consequently, the term rapid prototyping became popular among the producers, users and others to describe the technology and its application. What's more, most people close to the machines would refer to them as rapid prototyping systems. The term is still in use today.

Over the better part of two decades, many other terms have been used to identify the technology. Among the most popular: solid freeform fabrication, which is still in use today by a number of people in academia and the government. The organizers of the successful annual symposium by the University of Texas at Austin uses the term to promote its event, thus contributing to its popularity.

Layered manufacturing has also been used, mostly in Europe. Other terms include automated fabrication, additive manufacturing, rapid technologies, digital fabrication and 3D printing. One could argue that CNC machines could fall into the realm of rapid technologies and digital fabrication, so that's why I have swayed away from using them to describe a process that fabricates parts additively.

Growing Range of Applications

The industry has evolved and the applications of the technology has expanded greatly over the past. The technology was once used almost exclusively for prototyping, but it is now being used for wide-ranging applications. Among them: models for design concepts, patterns for dental restorations, medical implants for humans, artist sculptures, and custom awards and corporate gifts. Increasingly, companies are also using the technology for the production of parts that would otherwise be injection-molded, cast or machined, albeit in relatively small quantities. None of these examples are prototypes, yet many people, due mostly to habit and the lack of another term, continue to refer to the technology as rapid prototyping.

The concern is this: people being introduced to the technology could easily become baffled if it is explained that rapid prototyping is being used to manufacture end-use products. They might even question the integrity of a product that is being produced using a prototyping process. As a customer, I'd prefer to buy a product that was made using a manufacturing system, not a prototyping machine. I don't want a prototype; I want a fully developed and refined product.

When examining it from an investment point of view, the name has implications. The amount of money being spent on prototyping versus manufacturing when developing and producing a news product is vastly different. The ratio may be one to 1,000 or even greater. In other words, for every dollar spent on prototypes, $1,000 or more is spent on manufacturing. In large manufacturing companies, the ratio is closer to one to 10,000 or 30,000. The point is that manufacturing is where the money is—not in prototyping. So, if you are in the business of new product development and manufacturing and want to attract investment capital or gain support at some level, do you really want to call it rapid prototyping?

If you review how the technology is being used at a high level, one could group the applications into three broad areas. One group is the making of parts for the modeling of new design concepts. Another is for fit and not function prototyping, an application that is arguably among the most important for the majority of mid-range and high-end system installations. The third is custom and short run production, also referred to as rapid manufacturing—a term that has grown a lot in popularity around the world. I believe that this third group will someday become the largest and most important of the three.

About two years ago, I surveyed a number of individuals for whom I have a lot of respect. The purpose of the informal study was to gain input on the preferred name of the technology. The sampling was relatively small, but I was going after quality of input, not quantity. In the end, a level of consensus was reached. Most of the terms discussed earlier in this article were presented as candidates, as well as the term additive fabrication. It bubbled to the top and I've been using it religiously ever since. It has been an adjustment because habits die slowly.

The purpose of this installment of Viewpoint is not to promote the use of additive fabrication as the name to use in the future. In fact, on a scale of one to 10, I'd give it a seven. However, I believe that it's better than the alternatives. It more or less describes the technology that cuts across so many machines, organizations, industries and applications. I believe that most people understand the idea of fabricating objects from material additively, versus the use of a subtractive process—as in the case of CNC milling and turning—so I'm sticking with additive fabrication.

3D Printing

In the distant future, the term that will most likely become the most popular is 3D printing, for a strong reason. In 2005, 70 percent of all additive systems shipped to customers were classified as 3D printers, according to research for Wohlers Report 2006, a global study on the subject. A 3D printer is loosely defined as a low-cost variation of additive fabrication that is usually faster, easier to use and office friendly. 3D printers are often used to produce concept models for the visual and tactile inspection of a proposed design. Over time, the capabilities of 3D printers will expand and they will be used for applications that are now researched for mid-range and high-end systems. Already, a number of 3D printers have been used for fit and function prototyping and rapid manufacturing.

I truly believe that 3D printer will become the term of choice in the future to describe systems that fabricate parts additively. The term is easy to say and understand, given that most people understand the basics of three dimensions and printing. Combined, it communicates exactly what is happening technically in these machines. I believe that few people won't get it.

Today, however, 3D printing is used to group the low end of the market. In the future, when more than 90 percent of the installed base of additive systems is 3D printers, it is no longer the low end—it is the market. The growth of low-end machines is expected to continue for years. In the meantime, we are in need of a term to bridge the transition that will also take years.


Is it important for our industry to get broad consensus on an umbrella term that more accurately communicates the technology? Or, should the industry simply let "nature" take its course as it has for nearly two decades? The industry has debated the terminology for years on Internet mail lists, at conferences and in private meetings. A lot of time and energy has been spent industry wide, yet there has been little agreement. Meanwhile, many continue to use rapid prototyping or RP. Some believe that these choices of words have slowed the development of the industry and I agree. For that reason alone, I feel strongly about the need to use a more accurate term.

Please contact me if you agree or disagree. Which term(s) do you like or dislike? I'm interested in your thoughts and suggestions.

Industry consultant, analyst and speaker Terry Wohlers is principal consultant and president of Wohlers Associates, Inc. (Fort Collins, Colorado, USA). For more information visit