What's in a Name?

Although the definition of rapid prototyping is varied and the application of the term is diverse, it will continue to be the commonly used term to describe such processes as SLA, SLS and FDM.

"Perspectives" is a column co-authored by Terry Wohlers. The following was published 
in the May 2001 issue of Time-Compression Technologies magazine.

For nearly a decade there has been a great debate in rapid prototyping. The discussion is not about the best systems, materials or processes, or even the best ways to apply the technology; the debate is over its name and definition.

With so many disparate processes using the term, rapid prototyping has become diluted and is losing a sense of clarity and meaning - especially to those new to the rapid prototyping industry. New names and definitions have emerged and will continue to develop, at least as it is seen from our perspective.

Rapid Prototyping Defined

What is rapid prototyping? Some say that it is a process that creates parts in an additive, layer-by-layer manner. In the Wohlers Report 2000, the definition is "A special class of machine technology that quickly produces models and prototype parts from 3-D data using an additive approach to form the physical models." This is the "classic" definition, one that describes the systems and technologies that created a new industry in the late 1980s.

The broader definition applies to nearly any prototyping process that is executed faster than historically expected. In this loose definition of rapid prototyping, any process or technique that generates prototypes quickly is deserving of the rapid prototyping moniker. These definitions aren't wrong - both are acceptable, which has created the confusion.

Loss of Meaning

Scan any design or manufacturing publication and you will find the phrase rapid prototyping being applied to the "classic" RP systems or to every conceivable application - vacuum cast urethane parts from silicon rubber molding, investment casting, toolmaking, machining and reverse engineering scanning systems.

The attractiveness of the term has led companies of all disciplines to adopt rapid prototyping in their message. Rapid prototyping has been used because it is the latest buzzword, to convey that a company has kept pace with technology or to assure prospects of fast delivery.

Rapid prototyping continues to lose even more of its meaning when reviewing applications outside of mechanical engineering and product design. For example, in a recent marketing newsletter, an article titled Rapid Prototyping discusses the advantage of rapid prototyping website designs and structure - not exactly what those familiar with SLA, SLS and FDM would expect. With such a diversity of definition, the name cannot stand on its own.

Change is Challenging

Even though the definition is varied and the application of the term is diverse, rapid prototyping will continue to be the commonly used term to describe processes like stereolithography, selective laser sintering and fused deposition modeling.

Past attempts at renaming the industry and its technologies demonstrate how difficult this change would be. Alternative names have included freeform fabrication, solid freeform fabrication, automated fabrication, solid imaging, additive manufacturing and layered manufacturing. Each of these alternatives was proposed and greeted with little support. Yet, within the realm of rapid prototyping, there has been some success with new names such as 3-D printers, concept modelers and direct metal deposition, which clearly illustrates the need and desire for clearly defined labels.

To further demonstrate this confusion and need for clarity, consider the "high-end" rapid prototyping systems. If 3-D printing applies to quick, low-cost systems and direct metal deposition applies to systems that directly produce metal parts and tools, what label exists for the SLA 7000, Sinterstation® 2500plus and FDM Quantum? The answer is rapid prototyping, which when applied to both a general class of technology and a specific subset of that class, makes discussions confusing and complicated.

Alternatives for the Future

Within the manufacturing, computer and software markets, there is an unwritten guideline for naming new processes. Consider the names applied to a variety of manufacturing processes of which the majority describe a unique element of each process - differentiating the processes from each other. For example:

Another significant element is that each process is grouped with others that are similar - creating categories and subcategories. The major category offers a general classification of the technology, while the subcategory specifies the exact nature of the process. Following are some examples in other related and unrelated areas:

This structure of categories and subcategories, combined with names that clearly illustrate what is being represented, is used to describe vehicles, homes, movies and corporate organizations. Why then would rapid prototyping be any different? Marketing. That is the difference and it has the potential to contradict or complement the category and subcategory structure.

In the future, a company - possibly an established company in the document printer business - may commercialize an inexpensive machine and armed with loads of consumer data, this organization may create a name like "PlasticJet," which is immediately adopted and because of its utility and low cost, could become the "Kleenex®" of the rapid prototyping industry.

As technology improves, a process that is significantly faster than today's rapid prototyping systems may be developed and marketers may decide that this technology deserves a name that distinguishes it from other technology. Perhaps they decide to offer "hyper-prototyping" systems or "replicators" - a term that the industry has ignored. Whatever the name, it could become widely used to describe the category of machine technology that we today refer to as rapid prototyping.


No one knows how these names and definitions will develop or if they will be accepted, but industry - led by the press and the media - will influence these names and definitions based on clarity, conciseness and ease of delivery.

A critical benefit of rapid prototyping is that it communicates complex designs quickly, clearly and concisely, yet these technologies have not developed names that do the same. What we have today is both success and failure to communicate. The bottom line is that human nature will not allow this to exist over the long term, so new names and definitions must, and will, surface as the future unfolds. But, until that time, rapid prototyping is the name that most people understand and accept.

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