What's in a Name?

Whatever it's called in the end, rapid prototyping appears to be the wave of manufacturing's future.

Last week I attended the RAPID 2007 conference and exhibition in Detroit, Michigan. Sponsored by SME (the Society of Manufacturing Engineers), the annual event is the center of the universe for RP&M (rapid prototyping and manufacturing). Attendance was up in both attendees and exhibitors this year, as it has been the past few years, and that's good news for any live event. Beyond RP&M, the event also includes tracks and sessions on reverse engineering and 3D scanning, as well as interoperability and 3D collaboration.

Unlike years past, however, there was lot of conversation, during both formal presentations and informally in the hallways, concerning what this technology should be called and whether there is a term that could be universally agreed upon and understood.

The Ongoing Process Naming Dilemma
Admittedly, rapid prototyping and manufacturing is a mouthful and means different things to different people, such as hardware and software vendors, end users, academics and professional engineering organizations. There is a definite reason for this dilemma. First of all, several of the RP&M vendors have invested heavily in naming the technology that best suits their respective products, so they are in no hurry to embrace new terminology. End users want a term that describes the technology in practical terms, and academics seem to lean toward something that is more technically descriptive. And, yes, even SME has gotten into the act by coining the term DDM (direct digital manufacturing) as an umbrella term to describe RP&M. As testimony that even SME is grappling with the nomenclature, this year's conference was called simply, RAPID 2007.

SME defines DDM broadly as the process of taking a part directly from an electronic digital representation to the final product via additive manufacturing. For those of you who may not be familiar with it, additive manufacturing is the process of creating a physical object through the selective fusion, sintering or polymerization of a material. This process begins when a part is first designed on a computer and output in a digital format, most commonly STL (stereolithography). Ideally, the digital part design yields enough information to direct the operations of an additive manufacturing machine to control the layer-based deposition and processing of materials. This broad process definition also includes diverse materials that can be in a powder, sheet or liquid raw state.

According to SME, when production volumes are low and/or part complexities are high, these technologies can be a very economical choice. Parts that have internal features, complex geometries or sculpted surfaces usually are the ones that realize the greatest cost-benefit ratio from DDM, although there are exceptions to everything. Simply put, DDM is a result of material deposition and processing operations that convert a digital electronic model into a physical part or product.

The good thing about this term and definition is that they take more than one specific additive process into consideration. On the other hand, a lot of people I spoke with during the conference didn't like the term because it wasn't descriptive enough for their tastes.

Believe it or not, the term that seemed to be most universally accepted at the conference was 3D printing. However, by definition (and this, too, is a pretty broad definition), it is performed only by hardware from some vendors such as Z Corp., Stratasys, 3D Systems and Objet. Although it is a popular term today, primarily because 3D printing is in large part driving the growth of RP&M, ultimately (say in a few years), the term may be regarded as too limiting. But, then again, who knows?

Unlike some of the other RP&M processes, 3D printing can be one of several, somewhat similar but different, possible processes. One variation consists of an inkjet printing system whereby layers of a fine plaster and resin powder are selectively bonded by depositing, or "printing," a water-based adhesive from an inkjet printhead in the shape of each cross-section as determined by a CAD file. Other types of 3D printers feed liquids, such as photopolymer, through an inkjet-type printhead to form each layer of the model. Another 3D printing-like technology is FDM (fused deposition modeling), which uses a nozzle to deposit molten polymer onto a support structure, layer by layer. Regardless of the specific technology employed, 3D printing is optimized primarily for speed, relative low cost (machine and consumable material), and ease of use when dimensional accuracy and mechanical strength of prototypes are less important than its aforementioned benefits.

In spite of the fact that only a fraction of RP&M vendors can truly say they are doing it, 3D printing seems to be the term that most end users understand. Will it catch on in a bigger sense? That's hard to predict, but I would encourage you to continue this discussion at Cadalyst's Tech Forum: MCAD and tell us what you think it should be called.

Transitioning from Prototyping to Manufacturing
Historically, rapid methods have been used during the prototyping stage. That is slowly changing as vendors increasingly see that rapid manufacturing is a big part of their collective futures. Major efforts are under way to advance RP and DDM processes into high-volume production methods where they can compete directly with traditional manufacturing processes. However, although there are a lot of opportunities in this area, there are also a number of limitations that must be considered. I will explore that topic in more detail in the next installment of MCAD Tech News.

Author's Note: Because this conference and exhibition cover areas that I believe are important to the future of manufacturing technologies, in the coming weeks I'll review what is considered by many to be the bible of RP&M, Wohlers Report 2007: State of the industry, Annual Worldwide and Progress Report. I've known the author, Terry Wohlers, for several years and have assisted in writing a small section of it on the state of the 3D MCAD industry and how it relates to RP&M the past couple of years.