what is 3d printing and how does it work
A 3D printer is a device that creates an object by building it up one layer at a time. The materials a 3D printer uses vary from plastics to chocolate to concrete. In many ways, the printer part of the name is misleading; there really is not a lot in common with conventional printing. Joan prefers to use cooking as a metaphor, or you can use the more technical term—additive manufacturing—which is somewhat more descriptive of what the printers are actually doing.
Additive vs. Subtractive Manufacturing
A lot of conventional manufacturing (and old-fashioned shop class) is subtractive. That means that you start off with a big block of material (wood, metal, or anything else), and a machine tool shaves off pieces to create what you want. Additive manufacturing techniques like 3D printing instead add material a little at a time to create something.
There is a third set of manufacturing techniques, such as pouring concrete (although there is now concrete 3D printing, as we describe later), sculpting clay, metal-bending, or casting metal, that do not fit neatly into either the additive or subtractive category. In those cases, a tool, such as a mold or form, is used to shape a material. A malleable material is poured or pushed into the tool, and it conforms to the tool before hardening. Alternatively, as with a metal bending tool or the hands of someone shaping a clay pot, a harder material can be selectively forced into a new shape. Some of these techniques can be used in conjunction with 3D-printed parts to enable very fast prototyping.
A 3D printer starts off with an empty build platform and piles up material onto that platform one layer at a time. To figure out what should be in each layer, software takes a computer model and slices it into very thin vertical layers, like a precooked sliced ham set on end. Then, a computer controls a robotic head that creates one layer at a time in a variety of ways, depending on the type of 3D printer.
pic below shows a visualization of layers in software used to create models for a 3D printer (MatterControl, discussed later in this chapter), and other shows the part being printed.
printed layers simulated in MatterControl
3D printed layers in reality
Does 3D Printing Live Up to Its Hype?
You have probably heard a lot in the news lately about 3D printers and the many applications of the technology. How big an advance is this technology, really? And what new things will it enable? We think it is unfortunate that the technology has been so heavily hyped and suggested for a variety of applications where it might not be as good as incumbent techniques, because this misdirected hype distracts from the areas where it really is transformative.
3D printers are tools. You do not see people writing breathless papers about the crescent wrench and how many applications it has, because wrenches (or spanners, if you are from the eastern side of the Atlantic divide) have been around a long time. But when a new tool comes along, there is a period when things that were not really possible before become possible. We are in this phase with 3D printing, which is genuinely transformative for the following applications in particular:
- Learning how to make physical things: Using a 3D printer is a good gateway to using traditional machine tools. Although it is possible to burn yourself, they are a lot less intimidating than traditional shop-class machine tools.
- Product prototyping: It is now a lot cheaper and easier to prototype a physical product. In the past, either SLA or SLS printers (described later in this chapter) were used to make fragile, very expensive prototypes; or a prototype might have been cut out of foam board. It is now feasible to have a cheap printer at each office of a design firm and avoid shipping around physical models and prototypes altogether. Colleagues can literally email around a design.
- Design iteration: If it is easy and cheap to prototype, then it is also easy and cheap to try out different designs. This can allow for a more “quick and dirty” style of design, rather than perfecting a design before making a (formerly time-consuming) prototype.
- Visualizing complex abstract concepts: The ability to make a complex shape at low cost means that mathematicians, scientists, and engineers can print out a 3D representation of a complex shape to help with insights beyond those possible on a screen.
- Custom items: Medical, fashion, and other unique or small-run manufacturing items become more economical with 3D printing.
- Biomedicine: It is possible to lay up complex tissues involving scaffolding structures and living cells. This area is just beginning to come into its own.
People often ask us what a 3D printer is good for. This is always a slightly weird question for any tool. (Answer: what are you trying to make?) A better question is to ask what sorts of things they are not good for. 3D printing is still pretty slow (it takes hours to make a print of any size), and so at the moment it is not appropriate to make more than a few hundred of something. Beyond that, you want to think about mass-manufacturing techniques, like some sort of molding.
Types of 3D Printers
3D printers have been around since about 1984, when Chuck Hall developed the first 3D printer based on using a robotic mechanism to control a laser. The laser was used to solidify a tiny area in a vat of liquid resin, thus creating an object out of the resin. This technique is known as stereolithography (abbreviated SLA) and was first commercialized by 3D Systems in 1989. Since then, other technologies have evolved. This section categorizes them by the type of feed stock they use: powders, resins, filament, or other things.