Last month I promised that we’d have a look at the most recent and exciting printing technology—printing in three dimensions.

3D printing is practically science fiction realized. This amazing technology, though conceived decades ago, has emerged in recent years as a production tool for industrial designers, medical technicians and even hobbyists. Nowadays, 3D printers range from multi-million dollar giant industrial robots to inexpensive desktop home printers.

Additive Processes

3D printing, or additive manufacturing as it is called in the biz, is a process of making three-dimensional solid objects from a digital file. The creation of a 3D printed object is achieved by depositing successive layers of material until the entire object is realized. Each layer is a thinly sliced horizontal cross-section of the whole object. Most commonly, each layer is fused to the previous layer. In this article, I’ll describe four of the most common 3D printing technologies in use today. Since 3D printing is a kinetic process and can be a bit challenging to understand, I’ve included a basic schematic illustration of each system and, as a bonus, I’ve included Web addresses where you can watch videos that demonstrate each method.

3D Modeling

3D printing begins by creating a virtual design in a 3D modeling program to create an entirely new object, and saved as a CAD (Computer Aided Design) file. An existing object can be digitized by using a 3D scanner. 

In my October column I published a list of commonly used mainstream 3D programs that enable the artist or designer to create 3D objects from scratch. We also looked at 3D scanning technologies.

How It Works

After the 3D model is rendered, and to prepare a digital file for printing, the 3D modeling software “slices” the final model into hundreds or thousands of horizontal layers. When the sliced file is uploaded, the printer software uses the sliced data to print each layer. It reads each slice and gradually builds the object, fusing each layer it to the previous one.

There are several 3D printing technologies but they have one thing in common; they are all additive. That means that the material is built and not carved. They differ primarily in the way the material is deposited and how layers are fused together. What follows are descriptions of four of the most common 3D printing processes.

Vat Photopolymerisian – Stereolithography (SLA)

This technology uses a vat of liquid UV-curable photopolymer resin to sequentially deposit material one layer one at a time, and an ultra-violet laser to fuse the layers together. Between each layer, the laser exposes a cross-section of the object in the liquid resin to UV light, which cures and solidifies the pattern and fuses it to the layer below.

After a layer has been traced by the laser, an elevator platform to which the object is attached, descends by the distance of the thickness of a single layer  (0.002″ to 0.006″). A resin-filled blade sweeps across the top-most layer and re-coats it with fresh material. On this new liquid surface, the subsequent layer pattern is traced joining it to the previous layer until the complete three-dimensional object is formed (see Figure 1).

Material Jetting

In this additive process, two nozzles supply the material in tiny droplets just like a desktop inkjet printer. One of the nozzles builds the 3D object and the other builds a support structure that stabilizes the object. The material is deposited layer-by-layer and leveled with a leveling blade. The material is hardened by an ultra-violet curing lamp that follows the printhead. Sometimes poly-jet technology (multiple jets) is used to print objects with multiple parts and colors (see Figure 2).

Binder Jetting

This technology uses two components: a gypsum based powder which is form of plaster, and a super-glue like binder. In the build chamber, a roller spreads a layer of powder over the build platform. A nozzle jets binder into the powder in the shape of the cross section of the object. It uses inkjet printer heads similar to an inkjet paper printer to jet the binder into the powder.  Once a layer is printed, the build platform descends the thickness of a single layer and the roller distributes a new layer of powder. The process is repeated until the entire object is built. When completed, the object is removed from the build chamber and the excess powder is recycled. By coloring the binder, multiple colored 3D prints can be created. Binder jetting machines make good solid objects, but because they are essentially composed of plaster and glue they are limited to the creation of rigid parts (see Figure 3).

Powder Bed Fusion Selective Laser Sintering (SLS)

SLS technology uses a high-powered laser to fuse small particles of plastic, metal, ceramic or glass powders into a 3D object. The laser selectively fuses the powdered material by scanning the cross-sections (or layers) generated by the 3D modeling program on the surface of a powder bed, similar to binder jetting. After each pass the powder bed is lowered by the thickness of one layer, then a new layer of powder is deposited on top with a blade. The process is repeated until the object is completed.

The surrounding untouched powder serves as a support structure for the object eliminating the need for an auxiliary structure which is an advantage over technologies like material jetting that build support structures as the object is being printed. Unused powder is recycled for the next print job (see Figure 4).

The 3D Printing Outlook

The outlook for 3D printing over the next few years can only be described with one word and an exclamation point– GROWTH! Like inkjet printing in the 1990s, it has crept into our daily lives and changed the way we work.  The worldwide 3D printing industry’s revenue in 2013 was $3.07 billion. By 2020 it’s expected to exceed $21 billion (according to Wohlers Report 2014). 3D printing will ultimately affect every major manufacturing industry.

Medical

Patients are already benefitting from the development of 3D printed implants like artificial valves and kidneys. Prosthetics too are being printed with 3D technology, which assures comfort, enhanced mobility and durability (seeFigure 5).

3D bio printing of human tissue has been around since the early part of the twenty-first century. Living cells are deposited onto a nutrient rich medium and slowly built into three-dimensional tissue structures. As the technology evolves, scientists may ultimately be able to print entire human organs. Talk about science fiction realized!

Aerospace and Aviation

The development of metal additive manufacturing is responsible for the adoption of 3D printing in the aerospace and aviation industries. NASA, for example, prints combustion chamber liners using selective laser melting. The latest big news is that in April 2015 the FAA cleared the first 3D component to fly in a commercial airliner -- a housing for a compressor inlet temperature sensor on a Boeing 777 aircraft (see Figure 6).

Automotive

The automotive industry was among the earliest to use 3D printing for low-volume prototyping. Nowadays, the use of 3D printing in the automotive industry is rapidly evolving. An explosion in utilization of 3D printing from automotive manufacturers is powering a revolution in automobile design and production. It is conceivable that in the future an entire vehicle may one day be produced by 3D printing technology.

Industrial Printing

3D printing has been around for a few decades. For years manufacturers have been using it to create prototypes. The industry parlance for 3D printing a prototype is called rapid prototyping.

The advantage of rapid prototyping is obvious in the savings of time and money. A fast 3D printer can be obtained for tens of thousands of dollars and end up saving the company many times that amount of money in the prototyping process.

At one time, for example, Nike spent thousands of dollars on a single prototype of a shoe and had to wait weeks to see it developed. Now, the cost of a single prototype is within the hundreds of dollars. Furthermore, design changes can be achieved instantly on the computer and the prototype immediately reprinted.

Besides rapid prototyping, 3D printing is also used for rapid manufacturing. Companies employ 3D printers for short-run custom manufacturing. The printed objects are not prototypes but the actual end user products. 3D printing can offer a cost effective alternative to producing and storing large inventories of parts. Print-on-demand is gradually working its way into the market place.

Personal printing

Domestic 3D printing for artists and hobbyists saw a surge in growth in 2011. And because of the new demand, the cost of a home-based 3D printer has dramatically decreased. Currently prices range from $250 – $2,500 (see Figure 7). Printing 3D objects at home or in a studio on a small 3D printer that an artist scans with a hand held scanner or designs in a 3D modeling program is very rewarding form of sculpture, and work of this kind is rapidly becoming prevalent in art galleries and museums.

RepRap is an open-source project that fed the home 3D printer market. A RepRap 3D printer kit can be purchased for around $1,000 and assembled by the end user (see Figure 8). The RepRap website and blog (http://reprap.org) has a ton of information shared by its members who have purchased and built kits. Improvements to the machines and printing techniques have developed over time from the shared input of the RepRap community.

The Future

3D printing technology has the potential to change the nature of manufacturing as 2D digital printing did in the 1990s. End users will be able to do much of their own manufacturing. Currently 3D printers can print in color with multiple materials, and they will continue to evolve. It’s entirely conceivable that if you need a product you will be able to purchase a 3D file online and print the product at home. The dramatic affect on energy use, waste reduction, customization, product availability, medicine, art, industrial design, construction and science is already being felt and will no doubt grow in future.