Introduction to fabbers

     A fabber (short for “digital fabricator”) is a “factory in a box” that makes things automatically from digital data. Fabbers generate three-dimensional, solid objects you can hold in your hands, submit to testing, or assemble into working mechanisms. They are used by manufacturers around the world for low-volume production, prototyping, and mold mastering. They are also used by scientists and surgeons for solid imaging, and by a few modern artists for innovative computerized sculpture. Manufacturers report enormous productivity gains from using fabbers.

     Fabbers are categorized by the manner in which they operate on their raw material:

Figure 1.6. The three fundamental fabber processes.

• Subtractive: Material is carved away from a solid block, such as by milling, turning, or electrodischarge machining (EDM). Subtractive fabbers have been automated since the late 1940s, and are often called computer-numerically controlled (CNC) machines.
• Additive: Material is successively added into place to build up the desired object. The methods used include selective curing, selective sintering, and aimed deposition. The first commercial additive fabber was introduced in 1987.
• Formative: Material is neither added nor removed, but opposing pressures are applied to the material to modify its shape. Techniques in this category, including automated bending and reconfigurable molding, are under development.
• Hybrid: Processes from two or more of the above categories are combined. Sheet-based fabbers, which cut and laminate successive layers of sheet material, are hybrid subtractive/additive devices. A combination CNC punch press and press brake is a hybrid subtractive/formative fabber.

     Fabbers are a $10 billion industry worldwide in terms of annual sales of machines. Almost all of this is in the subtractive variety, with additive fabbers garnering only about $200 million in sales in 1998. (No purely formative fabbers are commercially available at present.) Sales of subtractive fabbers have been essentially flat throughout the 1990s. Additive sales, which grew dynamically through the early- and mid-1990s, have now flattened off as well.

     Most fabbers on the market today are industrial equipment, costing between $45,000 and $800,000 and requiring a specialized facility and a trained operator. When additive fabbers become available that are fast, inexpensive, and easy-to-use, this will spur new growth of the market, and ultimately additive machines will surpass the subtractive variety in market size.

Today’s additive fabbers

Figure 1.17. Fabbers are magical devices that transform digital data into models and products. Today’s big, expensive, complicated systems are paving the way for a new generation of small, affordable office machines.

     Available processes. There are six basic technologies on the market today for additive fabrication, including hybrid techniques incorporating an additive process:

• Selective curing. A liquid resin is caused to cure (harden) in specific locations to grow the desired object. Currently limited to photocuring, these processes use light as supplied by either a laser or by a masked lamp.
• Selective sintering. A powder is caused to melt in specific locations, and the melted powder then fuses into a contiguous solid, which builds up the shape of the desired object. Heat is currently supplied by a laser.
• Aimed deposition. A stream of material is aimed at specific locations on the growing object. There are currently three deposition processes.
  • Drop-on-drop. The material is deposited in a stream of tiny droplets from an ink-jet printhead. Currently limited to molten thermoplastics.
  • Continuous. The material is deposited in a continuous bead extruded through a nozzle. Currently limited to molten thermoplastics.
  • Drop-on-powder. A stream of droplets is aimed at specific locations on a stationary powder bed, and the object is grown by fusing of the deposited and powder materials. Currently limited to ceramic binders deposited on ceramic powders.
• Bond-first pattern lamination. Material in the form of a sheet is bonded onto a growing stack and patterns are cut in each successive layer to define the shape of the desired object. Currently limited to paper (yielding artificial wood) and some plastics.

     Process diagrams. See the process diagrams document for illustrations of most of the processes described above.

     Commercial fabbers. The following table lists the commercial fabbers that implement each of these processes.

     Several other techniques are under investigation in industry, government, and university laboratories around the world.

What are fabbers used for?

     (The page on Fabber Applications provides more detail on this subject. The summary here is provided for convenience.)

Figure 1. Fabbers are widely used today by automotive, medical, and packaging companies, as well as in scientific applications. For descriptions of some specific applications, please visit the Fabber Applications page.

     Commercial applications of fabbers are many and large. Some people have described the machines as “3-dimensional Xerox machines,” or “3-D faxes.” Indeed, both duplication and remote transmission of 3-dimensional geometries have been demonstrated using currently available machines.

     The applications of fabbers fall into five basic categories:

• Direct, low-volume production of products or parts
• Industrial models and prototypes
• Copy tooling, such as molds and mold patterns
• Imaging of scientific, mathematical, statistical, medical, and other types of 3-D data
• Computer sculpture

     Direct production and copy tooling are the primary applications of subtractive fabbers, which are generally capable of high precision work in steel and other metals. The first successful commercial application of additive fabbers has been in prototyping because of their ability to render almost any geometrical shape. From the beginning, prototypes made in additive fabbers have been used as masters for making soft tooling for low-volume copies, but interest is growing in the use of additive fabbers to directly grow hard tooling for injection molding and other high-volume copy processes.

     People who use fabbers today, or will use them in the foreseeable future, include

• Manufacturers for making small quantities of specialty items, such as design prototypes, production molds, and custom products
• Prosthetists, architects, theater prop makers, and other professionals whose work involves the production of individual, unique items
• Chemists, biologists, surgeons, and others needing to represent complex physical structures or 3-dimensional data sets
• Artists, including sculptors and jewelers
• Consumers in general, when the cost and ease of use become acceptable

     For brief descriptions of some of the specific ways that people have used fabbers effectively, or will use them in the future, see the page on Fabber Applications.

When to use a fabber

     There are four criteria that determine whether a project is appropriate for a fabber:

• Low volume
• Shape data is available in computerized form
• The desired shape is complex
• The ability to make changes is useful

     In this list, the first two are mandatory: a fabber is not appropriate for direct high-volume production (although it can be used to make a copy tool, which can then be used to make large quantities of a product or part), and it cannot be used without computerized shape data. The third and fourth criteria are optional but determine the importance of using a fabber: The more complex a shape is, and the more likely one is to benefit from the ability to iterate the design, the more advantage is likely to be obtained from using a fabber.

Why use one?

     Some of the advantages of fabricators over other means of generating solid objects are:

• Direct generation based on digital data, without the errors arising from a tradesman’s interpretation of the designer’s drawings
• Ease of iteration. Part of a design can be changed and the object refabricated without the need to redo the design of the entire object
• Accuracy and repeatability of dimensions on the order of 25 to 250 microns (0.001 to 0.01 inch)
• For the additive processes, the ability to generate shapes of arbitrary geometric complexity, including composite and nested (“ship in a bottle”) structures made without assembly and without seams

     The advantages of using fabbers in design and production applications have been nothing short of dramatic. Manufacturers have typically realized time and cost savings of 50 to 80 per cent in product development, and even greater cost savings and schedule reductions are not uncommon. Along with reduced cost and development time, the practical ability to iterate designs leads to improved final product quality. Moreover, the ability to turn a new idea into a final product quickly can cause a stir of excitement and professional satisfaction in the product team. This in turn feeds back to high productivity and quality of performance from the individuals involved.

Limitations

     Although they often seem magical in their abilities, fabbers today are still far from the “Replicator” of Star Trek fame. Additive fabbers are generally limited in accuracy and resolution to about 0.1 mm (0.004 inch), although better results can be obtained by experienced operators or with some experimental techniques. Although fabbers are often much faster than alternative methods, they are not instantaneous, and sizable projects can run for days to be produced. Moreover, the maximum size that can be built in a single run of the largest additive fabbers is limited to less than half a cubic meter (a few cubic feet). Materials selection is also a limitation of the currently available machines. The commonly available materials include acrylics, epoxies, urethanes, and ABS, as well as wax for investment casting masters. Specialty materials also available include artificial wood and specially formulated ceramics, metallic alloys, and metallic composites. Finally, one must recognize that fabbers are still highly technical devices, requiring trained personnel and often industrial environmental controls for their use.

Process diagrams

     For diagrams of additive fabber processes, click on the name of the process below.

Selective curing	Selective sintering	Continuous deposition	Drop-on-powder deposition	Bond-first pattern lamination	Cut-first pattern lamination (Offset™ Fabbing)

For more information

     Provocative thinking about the future of fabbers is presented in the following articles and speech transcripts:

• The FAB–ulous Fabber! — How to Profit from the Next Technology Revolution. The all new presentation on fabbers for the year 2000.
• Fabbing the Future: Developments in Rapid Manufacturing, presentation by Marshall Burns at Plastics Product Design & Development Forum, Chicago, Illinois, May 30, 1998
• Automated Fabrication—The Freedom to Create, by Marshall Burns in Technology Management, Volume 1, Number 4, 1995
• The Household Fabricator, comments offered by Marshall Burns in panel discussion on Future Directions in Solid Freeform Fabrication at the Fourth Solid Freeform Fabrication Symposium, University of Texas at Austin, Austin, Texas, August 11, 1993
• The Origins and Direction of the Fabricator Revolution, by Marshall Burns in Rapid News, North American edition, September 1997
• Using Fabricators to Reduce Space Transportation Costs, by David S. McKay, Hubert P. Davis, and Marshall Burns at the Solid Freeform Fabrication Symposium, Austin, Texas, 1996
• The Personal Factory, by Brock Hinzmann, SRI International, from the MCB Internet Conference on Rapid Prototyping, 1996
• Automated Fabrication: The Future of Manufacturing, by Marshall Burns in Rapid Prototyping Journal, Volume 1, Number 1, 1995
• Growing Autofab into the 21^st Century, by Marshall Burns in Rapid Prototyping Report, April 1994
• Perspectives on StereoLithography: Automated Fabrication in the 19^th, 20^th, and 21^st Centuries, keynote address by Marshall Burns at StereoLithography Users Group Conference and Annual Meeting, San Francisco, California, March 31, 1992