Academic journal article Library Technology Reports

Chapter 2: The Types of 3-D Printing

Academic journal article Library Technology Reports

Chapter 2: The Types of 3-D Printing

Article excerpt


Chapter 2 of Library Technology Reports (vol 50, no. 5) "3-D Printers for Libraries" describes in detail the predominant type of 3-D printing, fused deposition modeling (FDM). The chapter also covers stereolithography, selective laser sintering, and laminated object manufacturing.

In chapter 11 described the most common type of 3-D printing as a sort of robotic hot glue gun. This process, only one of multiple kinds of 3-D printing that are available, is usually referred to as fused deposition modeling. In this chapter we'll take a look at not only fused deposition modeling, but also selective laser sintering, stereolithography, laminated object manufacturing, and electron beam melting. While many of them are well outside the price point for most libraries, prices go down dramatically as soon as patents expire on the core technologies behind the printing methods. This is the central reason that fused deposition became inexpensive so quickly over the last five years, and most people that follow 3-D printing believe that laser sintering will follow suit shortly because a key patent for that technology expired in January 2014.

I'll start with the printing technology most central to libraries at the current time, fused deposition modeling, and then, after we wrap our heads around how that technology works, we'll take a look at other options that may be coming for us to use in the next three to five years.

Fused Deposition Modeling Printing

Fused deposition modeling (FDM) is what most people understand to be 3-D printing, as this technology is by far the most common and in many ways the simplest of the possibilities. FDM uses a variety of plastics that fall within a range of melting points and that fuse when melted and resolidified, the most common of which are ABS (acrylonitrile butadiene styrene) and PLA (polylactic acid). We'll discuss the specifics of these and other print substrates below.

The most common arrangement for an FDM printer is called a Cartesian print engine because it uses basic Cartesian coordinates (X, Y, Z) to create the printed objects. There are multiple types of printers even within this general category, although two are more common than others: the MakerBot style (see figure 2.1), which relies on a fixed plane X and Y printhead and movable Z print bed, and the so-called "RepRap" style, which relies on a fixed plane X axis, while the Y axis is controlled by moving the print bed itself and the Z axis is accomplished by moving the whole printhead system vertically upwards (see figure 2.2).

There is at least one other significantly different geometry for an FDM printer, the layout that is called a delta printer. In this instance, the printhead is suspended from three arms that are controlled along vertical supports while the print bed is completely stationary. This arrangement allows the printhead to "float" above the print bed and be located at any physical point in three dimensions simply by altering the relation of each of the three arms to the other. This is the same sort of control geometry at work in the flying cameras used in NFL games, applied to a robot. I will discuss two examples of a delta printer in chapter 5.

The Mechanics of Printing

Regardless of the control geometry used, the method of printing is the same for both types of FDM printers.

The printhead is a metal tube with a heating element and thermistor to control the temperature. The plastic substrate is melted by the heat of the printhead, and pressure is applied by forcing more plastic in, causing some of the liquid plastic to extrude through a small nozzle that ranges from .2 mm to .5 mm in size.

A print from an FDM printer begins with a single layer of plastic applied very thinly to the print bed, the nozzle moving across the print bed and depositing the plastic in the shape of the object it's creating. This initial layer is the base layer of the object, and the second layer will be deposited directly on top of the first and will fuse due to the properties of the plastic involved. …

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