Three Dimensional Printing At the Advanced Media Studio

By Alexander Gibbons

As computers become increasingly integrated into our daily lives, the technology that enables them to communicate back to the world becomes ever more advanced. Computer monitors and printers, typical output devices, are limited in their utility and are only capable of creating impressions of the physical world around them. As technology evolves, however, the computer will do more than just represent and calculate ideas or objects; it will build them as well. In fact, the time when your home computer can be used to construct the desk lamp that it sits next to is already here, and the technology that accomplishes this is part of a burgeoning set of technologies known as rapid prototyping (RP).

Although the technology to translate computer data into physical models has existed since the 80's, it has only recently evolved to a level that doesn't require specialized technicians to operate. Traditionally, RP technology had been reserved for the aerospace industry and the military, but today's RP equipment is often used by small design and architecture firms to create models, by scientists for visualization, by doctors for implants and prostheses, as well as by artists for sculptures. In the future, RP machines will likely find their way into our homes and will operate in much the same fashion as our current home printer.

Figure 1. Plane models generated by NYU's Spectrum Z510 3D printer.

NOMENCLATURE OF RAPID PROTOTYPING

Rapid prototyping, as it's most popularly known, is more accurately described as solid freeform fabrication (SFF) and is defined as "a technique for manufacturing solid objects by the sequential delivery of energy and/or material to specified points in space to produce that solid."¹ Rapid prototyping is not always as rapid as some might imagine—NYU's Spectrum Z510 three-dimensional printer, for instance, sometimes requires six to seven hours to build an object (though this is often significantly less time than it would take to craft the object by hand)—nor is it used solely for prototyping, as the object is sometimes the final product or piece of art

Three dimensional printing is one amongst a number of subsets of RP technologies, such as stereolithography (SLA) and selective laser sintering (SLS). In 3D printing, a computer program divides a model into cross sections, which are then built with many layers of powder selectively bonded by a liquid adhesive that is precisely dispensed from an inkjet printhead.²

Figure 2. Detail of a model that takes advantage of the
Spectrum Z510's color printing capabilities.

THE PHYSICAL MODEL

NYU's ZCorp Spectrum Z510 builds parts from a proprietary plaster-based powder in layers of a few thousandths of an inch thick. Each layer of powder is spread across a piston-supported bed, and is lowered with each pass and then sprayed with binder using traditional inkjet printheads. Binder is applied to the areas of the cross section that are solid—any areas that are left dry will remain as loose powder that will support the model as it's built but must be removed when the process is completed. The build bed of the Z510 is 10" x 14" and can extend to a depth of 8", thus is capable of building parts within a 10" x 14" x 8" envelope.

The premier feature of the Z510, however, is its ability to print objects in full color—a feature that is unique among other RP technologies. Parts can be printed with textual labels, colored surfaces, or even with photobased textures. Also of note is the ability of the Z510 to build models with moving parts. Because parts are separated by loose powder, they can be built up against other parts without joining, so that, for instance, gears can be built onto axles that connect to other gears and axles and form a functioning machine.

Figure 3. The front desk of the renovated Advanced Media Studio.

THE VIRTUAL MODEL

Before a physical model can be produced on a 3D printer, a virtual computer model must be assembled. Traditionally, computer models destined for rapid prototyping came from computer aided design (CAD) software programs and were usually designed by engineers. At the time, 3D modeling software typically described only surfaces, and did not define the space inside an object any differently from the space outside the object. The complex task of building water-tight models— capable of differentiating inside from outside space—from accurately stitched and oriented surfaces required the skill of a highly trained specialist. Luckily, today's more user friendly 3D programs and the Z510's advanced ability to interpolate solid space from geometric surface data have empowered less experienced designers to generate 3D files and build physical parts.

Figure 4. Sculptural shapes generated
by the Z510 printer.

Rapid prototyping systems will not directly print from a 3D program's native file format. They must first be converted to a triangulated file format, such as STL (Stereo-Lithography) or VRML (Virtual Reality Modeling Language), in which surface geometry is broken down into 2D triangles. Almost all 3D programs have such a feature or will accept a plug-in to perform the conversion. The VRML file format is required when preserving color or texture along with the geometry of the original model, while STL is a geometry-only file format. Neither of these formats, however, preserves the scale of the original model. Scale and orientation within the bed are assigned when the triangulated file is brought into ZCorp's 3D printing software. Additionally, the printer's software is used to perform some basic automatic as well as manual correction of any problem areas in the file, such as overlapping vertices, aligned and unconnected surfaces, and inverted normals.³

THE ADVANCED MEDIA STUDIO

The Advanced Media Studio (AMS), located at 35 West 4th Street on the 2nd floor, provides three dimensional printing services to all faculty, students of the arts, and visiting artists with approved project proposals. The AMS also offers access to a suite of 3D modeling programs, including sophisticated CAD packages such as: Form·Z, SolidWorks, and Cobalt; the NURBS modeling software Rhino; the 3D animation-oriented package Maya; Mathematica and MATLAB; and SketchUp, an easy-to-learn, conceptually based 3D modeling program. Clients interested in using this service should note that file inspection and correction is their responsibility, and will involve learning ZCorp's ZPrint software.

For more information about 3D printing services at the ITS Advanced Media Studio, visit www.nyu.edu/its/ams/, or send an email to its.rp@nyu.edu.

Footnotes

1. Wikipedia, http://en.wikipedia.org/wiki/Solid_ freeform_ fabrication
2. Wikipedia, http://en.wikipedia.org/wiki/3D_printing
3. A "normal" is a 3D vector that is perpendicular to a flat surface. (Wikipedia, http://en.wikipedia.org/wiki/Surface_normal)

Author Biography

Alex Gibbons is a Faculty Technology Specialist at the Advanced Media Studio for ITS' .edu Services.