Posted on March 26, 2022

In recent years, 3D printing has drawn a lot of attention to itself with breakthroughs in various industrial applications. Given the relatively recent explosion in the press, it may surprise you then to learn that the first 3D printer was actually built in 1983 – over 30 years ago – by Charles (Chuck) Hull, a co-founder and now Executive Vice President of the company 3D Systems [1]. The recent upsurge in applications and mainstream news coverage of 3D printers comes partly from the steep drop in price in the last several years; machines that once sold for thousands of dollars are now available for purchase for as little as a couple hundred [2]. While still not readily accessible to the average American, this technology is rapidly approaching a point where 3D printers could become as commonplace in a typical household as a regular printer.

How does it work?

At its most basic, 3D printing is an example of additive manufacturing: creating something through the sequential addition of material. This differs from a lot from more traditional methods used for fabrication, called subtractive manufacturing. These methods, such as machining or carving, start with a chunk of material and remove or “subtract” layers off to create the desired part. While methods that are essentially additive have been in used in manufacturing for quite some time, such as building a metal utensil from several pieces of wire, 3D printing gives us two main advantages over these other methods. First, it allows us to more easily make small, detailed objects with high precision, and second, it allows us to model the end product in detail and create it exactly as planned.

The concept behind 3D printing is fairly simple. To start a 3D printing project, you first need a model, or blueprint, of what you want to create. These models are usually made using computer-aided design (CAD) software. A computer then takes this 3D prototype, cuts it up into a bunch of very thin horizontal slices, and saves these slices into a file. You send this file to a 3D printer which uses the information to print the slices, one at a time, on top of one another. These layers are fused together to create a solid three dimensional object. A normal printer works very similarly, printing a very thin layer of ink onto a piece of paper in a design specified in a file you provide. But, while a normal printer uses ink and computer files we’re all fairly familiar with, such as Word documents or PDF files, a 3D printer can use a variety of materials to print with, print multiple layers, and uses a different kind of file that stores a three dimensional design. These added functions serve to make a 3D printer much more versatile than a normal printer in what it can create.

To elaborate, there are three main types of 3D printing techniques used to create these layers and fuse them together: selective solidification of liquid, selective bonding of layers of powder, and material deposition. The first two techniques use a laser to solidify or bond a specific section of a reservoir of liquid or powder to match the design of one of the slices. The most common example of selective solidification of liquid is stereolithography, which is the technique invented by Charles Hull and used in the first 3D printer. Stereolithography uses a material that changes from a liquid to a solid when exposed to ultraviolet (UV) light. It is one of the most precise techniques available, able to create layers only 0.0025 inches thick [4]. A common example of the second technique is selective laser sintering (SLS), which uses a high power laser to fuse the selected group of particles in a layer of powder together, both within each layer and between layers. There is a wide range of options for materials to use – plastic, metal, ceramic, wax and glass can all be ground into particulates that are usable in SLS [4],[5].

The third technique, material deposition, involves melting or softening a material and then forcing it through a nozzle onto a surface in the desired pattern. Fusion deposition modeling (FDM) is one example of this technique. Most FDM machines use a thin piece of either plastic or metal that is fed up from a coil within the machine and melted within the nozzle of the printer, to be deposited on a surface in successive layers. Many biodegradable options are being developed for the input filaments, making this a more sustainable option for 3D printing. The use of semi-liquid materials also gives this technique a wide range of applications – from gourmet food processing (imagine 3D printing chocolate or cheese!) to building houses by extruding concrete [4], [5].

Applications

Given the wide range of materials available for use in 3D printing, the variety of printing techniques, and the dropping prices for the machines themselves, it is no wonder we are seeing so many varied applications of 3D printing popping up recently. Applications span a whole host of industries – art, construction, culinary, medical sciences, and more. A 3D printer developed by the Cornell Creative Machines Lab at Cornell University allows for the fabrication of customizable food [6]. Several architectural firms and companies are working on 3D printed house projects, using both concrete and plastic, including a Chinese company that just built 10 one-story houses in a single day using a giant 3D printer [7]. Another exciting adaptation of 3D printing technology is the LIX 3D pen, a material deposition 3D printer housed in an object the shape and size of a pen, which allows the user to “just doodle in the air” [8].

In the medical sciences, 3D “bio-printers” are being used for many applications – prosthetics, cartilage, and bone transplants are all being produced at a fraction of the normal cost. Soft tissue implants are also being developed including tissues and organs, potentially making organ donors a thing of the past [9]. The creation of blood vessels within 3D printed tissues and organs has been one of the main problems in bio-printing, but a recent breakthrough offers a possible solution to the problem. Tissues are printed using multiple types of “ink”: an ink containing the cells to build the tissue with, and an ink that contains proteins and other biological molecules that surround cells in the body. Researchers at Harvard have added another ink to the mix that has a Jello-like consistency at room temperature, but liquefies when cooled. This ink gets printed within the tissue where blood vessels would go, then the printed tissue is cooled, liquefying the ink. The liquefied ink is then removed, leaving empty channels where blood vessel cells can be inserted [10].

Many consumer-friendly 3D printing options are available as well. For those interested in owning their own 3D printer there are both build-from-scratch 3D printer kits and pre-assembled machines. For those who don’t want to purchase a 3D printer, websites such as Sculpteo, MakerBot, and Shapeways help users design their own objects then print and ship them to the users. With such a wide range of customization, availability, and applications, we are sure to keep hearing about 3D printing.

Original article: https://sitn.hms.harvard.edu/flash/2014/3d-printing-why-all-the-hype/

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