3D Printing: Making the Virtual Real
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Introduction
A 3D printer uses a virtual, mathematical model to construct a physical artifact. For example, a designer in the process of creating a new laptop can use a software package to create a three-dimensional model of her creation, that can be manipulated and viewed on the computer screen. The 3D printer can take the symbolic representation of this new object and use it to build a full-size, physical model that can be held and
manipulated, helping the designer to better understand the strengths and limitations of her design. An architect can turn the plans for a building into a three-dimensional model and then “print” a scale model to help him understand and communicate his design. An archaeologist can print duplicates of an important, but fragile, tool so that her students can hold it in their hands and better understand how it might have been used by an ancient civilization. A biochemist can print accurate models of DNA
molecules, enlarged by many orders of magnitude, to help students and researchers better understand nature by engaging their hands as well as their eyes in comprehending the geometry of nature. And a student of the arts can create a unique object that would be difficult or impossible to build by hand.
We will not here consider other types of computer-controlled manufacturing, such subtractive machines, which work by cutting away from a larger piece of material in order to build a part.
Additive rapid prototyping machines were first introduced twenty years ago, when 3D Systems introduced the Stereolithography, or SLA machine. While these machines were remarkable for their ability to create complex parts, they were (and continue to be) large, expense, and difficult to operate. As such, they are of limited interest to most
academic institutions except for a few well-funded laboratories. However in the latenineties lower cost machines using technologies such as fused-deposition modeling
(FDM) and powder binding (defined below) began to be available in the $30,000 to $50,000 range. These machines, which can be used without special environmental controls and with a modest amount of training, are the first 3D printers by our definition.
In the evolution of rapid prototyping equipment, we have seen a history somewhat like that of the mainframe computer (SLA) and the mini-computer (early FDM and powder binding) systems. However, we are on the verge of the introduction of new systems that will cost less than $10,000, require very little training, and are capable of being operated in a typical faculty office or computer lab or home. At least one vendor has
the ambition of producing 3D printers for less than $1000 in five years. It is the thesis of this paper that as these printers achieve lower price points and accessibility, they will spring up across campuses and be used for applications yet to be imagined. Our purpose is to disseminate a basic understanding of a technology that is likely to grow dramatically in popularity within the next few years.
3D Printing: process and equipment
To use a 3D printer, you have to have something to print. In most cases, users create their models using a commercial CAD tool such as Solidworks or Rhinoceros. This complex software can be quite expensive, but as it has come into wide use academic licenses are
generally available for several hundred dollars a seat. Occasionally lower-cost software such as SketchUp, available in free and in “pro” versions can be used, but with some limitations since SketchUp was not designed to create manufacturable objects. As lower cost printers
become available, the software market is likely to broaden and new, simpler programs may become available, analogous to the drop in cost and complexity of desktop publishing software in the 1990’s. Commercial 3D CAD software also places demands on computer
processing power and memory, although the vast majority of the newer multi-core systems will be more than adequate for most modelers.
The current generation of 3D printers typically require the output from the CAD program to be stored in a format called STL, which defines a shape by a list of triangle vertices. This step is largely invisible to the user, although the output may need to go through an automated “clean
up” step to reduce anomalies that might be invisible on a screen but could impact the printing process. Then the cleaned up STL file is used to drive the 3D printer.
EDUCAUSE EVOLVING TECHNOLOGIES COMMITTEE 3D PRINTING: MAKING THE VIRTUAL REAL
3D printers work by building up parts layer by layer. Depending on the machine and the precision required, an individual layer is about 0.0035 to 0.007 inches thick. The size of an object that a particular machine can make is limited by a bounding box called its build size. For example, the powder-binder printers offered by Z Corporation have a build-size of 8 x 10 x 8 inches to 10 x 14 x 8 inches . There is considerable craft in aligning parts within the build area to achieve maximum quality and
minimum build time. Depending on the technology used, the size of the object, and the precision required, build times can run from an hour or two up to twelve hours or more. However, once the build process begins, it generally requires little or no supervision or intervention.
While there are new technologies primed for release in late 2007, as of this writing the vast majority of 3D printers used in educational institutions are either fused-deposition modeling or power binder based. This section provides a brief introduction to two of the most common systems and their capabilities.
Fused-Deposition Modeling (FDM): Stratasys Dimension FDM machines build layers by extruding a thin bead of a semi-molten plastic, usually acrylonitrile butadiene styrene (ABS) plastic. ABS is an attractive material, because it’s hard, durable, and low in toxicity. It’s familiar as the plastic used in Lego-brand toy bricks. Although it can be dyed, it’s typically used in its original off-white form. The FDM
machine heats the ABS to soften it; as it’s extruded, it begins to harden and as it does it adheres to the layer below it. Because the material comes out soft at first, any “overhanging” parts need
to have supports built into them; once the plastic hardens, the support material is removed. The Stratasys Dimension sells for approximately $20,000 to $35,000. The Dimension has a build area of 8 x 8 x 12 inches. The least expensive Dimension systems require the support
parts to be removed manually, while the more expense systems use a soluble material that’s washed away in a solvent bath. FDM machines build strong, precise objects that can be used for a wide variety of purposes. The cost for the plastic used runs about $8-10 per cubic inch.
Powder-Binder Printing: Z Corporation
Powder-binder printing works by building up layers of a plaster-like powder that is then sprayed with a liquid binder, or glue, from an ink-jet printer head. In each pass, a new layer of loose powder followed by a pass by the printer head applying the binder. If you imagine each
layer of powder as something like a piece of paper, it’s virtually the same process as ink-jet printing, except that each layer binds to the next and the powder that isn’t sprayed can later be brushed away to leave the constructed part. As the printer builds the object from the bottom to
the top, the powder can hold any overhanging parts in place, so no supports are needed. Once the parts are printed, they are removed from the bed of powder and dusted off, and unused powder can be recycled.
Z Corporation, or Z Corp as it’s often known, offers printers in the range of approximately $25,000 to $50,000. All models can build excellent parts; the highest price system can build the largest models (10 x 14 x 8 inches) and can add color. Z Corp printers generally build parts